JP7571567B2 - Vehicle underbody structure - Google Patents

Description

The present invention relates to a vehicle undercarriage structure.

In automobiles and other vehicles, large loads may be applied in the longitudinal and transverse directions of the vehicle while it is in motion. For example, when the vehicle turns, inertial and centrifugal forces may act on the front outer wheel. In such cases, torsional vibrations may occur in which the underside of the floor panel tries to twist inward in the longitudinal and transverse directions of the vehicle, centered on the underside of the floor panel on the wheel side diagonally opposite the wheel to which the load is applied.

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 longitudinal direction of the vehicle, a pair of side sills 2 extending in the longitudinal direction of the vehicle at a predetermined distance on the outer sides of the main side frames 1 in the transverse direction of the vehicle, a number of cross members 31-35 extending in the transverse direction of the vehicle and spaced apart in the longitudinal direction of the vehicle, and a number of torque boxes 41-43. The cross members 31-35 connect the pair of main side frames 1.

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 increasing the energy absorption efficiency during a side collision.

Patent No. 4349039

However, in the support structure of Patent Document 1, no special ingenuity is put into the cross members 31-36, which are the transmission paths for the transmission of load and vibration between the right front wheel and the left rear wheel, which are diagonally arranged on the vehicle, or between the left front wheel and the right rear wheel. Therefore, it is difficult to say that efficient transmission of load and vibration has been achieved.

As a result, the support structure of Patent Document 1 is unable to effectively suppress torsional vibrations in the floor panel, making it difficult to improve the vehicle's noise and vibration (NV) characteristics.

In view of these problems, the present invention aims to provide a vehicle underbody structure that can efficiently transmit load and vibration from a wheel bearing a vehicle load to a wheel diagonally disposed therefrom, suppressing torsional vibration of the floor panel and improving the vehicle's noise and vibration characteristics.

In order to solve the above problems, a representative configuration of the vehicle underbody structure according to the present invention is a vehicle underbody structure that includes a floor panel that forms the floor surface of the vehicle, the vehicle underbody structure further includes a pair of side sills that extend in the vehicle longitudinal direction along the edge of the floor panel, a cross member that extends in the vehicle width direction below the floor panel and connects the pair of side sills to form a closed cross section inside, a pair of rear side members that are connected to the pair of side sills and extend further rearward, and a rear connecting portion that connects the cross member to each of the pair of rear side members, the rear connecting portion having an inner rear connecting surface that connects the inner side surface of each of the pair of rear side members to the rear surface of the cross member and extends inward in the vehicle width direction toward the front of the vehicle, and a lower rear connecting surface that is continuous with the lower edge of the inner rear connecting surface and connects the lower surface of each of the pair of side sills to the lower surface of the cross member.

The present invention provides a vehicle underbody structure that efficiently transmits load and vibration from a wheel carrying a vehicle load to a wheel diagonally opposite the wheel, suppressing torsional vibration of the floor panel and improving the vehicle's noise and vibration characteristics.

1 is a bottom view showing a vehicle underbody structure according to a first embodiment of the present invention; 2 is a diagram showing a state in which a part of the vehicle underbody structure of FIG. 1 is viewed from another direction. 3 is a diagram showing the vehicle underbody structure of FIG. 2 with the rear connecting portion omitted. FIG. 2 is a diagram showing a modified example of the vehicle underbody structure of FIG. 1 . 1. FIG. 4 is a diagram showing another modified example of the vehicle underbody structure of FIG. FIG. 6 is a bottom view showing a vehicle underbody structure according to a second embodiment of the present invention.

A typical configuration of a vehicle underbody structure according to one embodiment of the present invention is a vehicle underbody structure that includes a floor panel that forms the floor surface of the vehicle, the vehicle underbody structure further includes a pair of side sills that extend in the vehicle longitudinal direction along the edge of the floor panel, a cross member that extends below the floor panel in the vehicle width direction and connects the pair of side sills to form a closed cross section inside, a pair of rear side members that are connected to the pair of side sills and extend further rearward, and a rear connecting portion that connects the cross member to each of the pair of rear side members, the rear connecting portion having an inner rear connecting surface that connects the inner side surface of each of the pair of rear side members to the rear surface of the cross member and extends inward in the vehicle width direction toward the front of the vehicle, and a lower rear connecting surface that is continuous with the lower edge of the inner rear connecting surface and connects the lower surface of each of the pair of side sills to the lower surface of the cross member.

In the above configuration, the rear connecting portion connects the inner side of the rear side member to the rear surface of the cross member at the inner rear connecting surface. Therefore, even if a large load is transmitted to either the left or right front wheel and torsional vibration occurs in the floor panel centered on either the left or right rear wheel located diagonally opposite, because the rear side member and the cross member are connected by the rear connecting portion, this torsional vibration can be transmitted to and dispersed by the highly rigid cross member.

In addition, the inner rear connecting surface of the rear connecting portion that transmits the torsional vibration to the cross member is shaped to extend inward in the vehicle width direction as it moves toward the front of the vehicle. Therefore, this torsional vibration can also be transmitted and dispersed to the opposite side sill or rear side member via the cross member and the opposite rear connecting portion. Furthermore, the lower rear connecting surface is connected to the lower surface of the side sill, continuing from the lower edge of the inner rear connecting surface. Therefore, the vibration in the vehicle width direction transmitted from the rear suspension to the rear side member can be transmitted and dispersed to the side sill connected to the rear side member, and can be transmitted and dispersed to the opposite side sill or rear side member via the inner rear connecting surface of the rear connecting portion, which has the same shape as above. Therefore, according to the above configuration, the load and vibration can be efficiently transmitted from the wheel to which the load of the vehicle is applied to the wheel side arranged diagonally from the wheel, suppressing the torsional vibration of the floor panel and improving the NV characteristics of the vehicle.

A closed space may be formed by the rear connecting portion, the floor panel, the rear surface of the cross member, the inner side surfaces of each of the pair of side sills, and the inner side surfaces of each of the pair of rear side members.

In this way, each component forms a closed cross section, which increases the rigidity of the rear connector, floor panel, cross member, side sill and rear side member, thereby suppressing floor vibration.

The inner rear connecting surface of the rear connecting portion may be arc-shaped.

In this way, because the inner rear connecting surface is arc-shaped, it is possible to prevent the load and vibration transmitted from the rear side member from concentrating locally. Therefore, the inner rear connecting surface can efficiently transmit and distribute the load and vibration to the cross member. Note that the term "arc-shaped" is not limited to an arc-shaped shape that is a part of a circle, but also includes an arc-shaped shape that is a part of an ellipse. Because the inner rear connecting surface is arc-shaped, it is easier to transmit the load and vibration transmitted from the rear of the vehicle to either the left or right rear side member to the side sill on the opposite side, compared to when the inner rear connecting surface is inclined linearly inward in the vehicle width direction.

Each of the pair of rear side members has a front end that extends outward in the vehicle width direction as it approaches each of the pair of side sills, and the inner rear connecting surface of the rear connecting portion is connected to the inner side surface of each of the front ends of the pair of rear side members.

As a result, when vibrations are transmitted to the rear side member from the rear of the vehicle, the vibrations can be efficiently transmitted from the inner side surface of the front end of the rear side member to the inner rear connecting surface of the rear connecting part.

The vehicle undercarriage structure may further include a rear cross member that extends in the vehicle width direction and connects the inner side surfaces of the pair of rear side members, and the inner rear connecting surface of the rear connecting portion may be joined to the rear cross member so as to straddle the rear cross member.

This allows vibrations transmitted through the inner rear connecting surface to be dispersed and released to the rear cross member.

The arc-shaped inner rear connecting surface of the rear connecting portion may begin to curve forward from the joint with the rear cross member, or the degree of curvature may increase.

In this way, the arc-shaped inner rear connecting surface curves or the degree of curvature increases starting from the joint with the rear cross member, which increases the efficiency of vibration transmission between the rear cross member and the inner rear connecting surface while avoiding localized load concentration in the curvature start area where the curvature of the inner rear connecting surface begins, where stress is likely to concentrate.

As an example, if the inner rear connecting surface is curved starting from the joint with the rear cross member, a portion of the load acting on the curvature start area from the rear can be transmitted to the rear cross member. Also, if the inner rear connecting surface increases the degree of curvature starting from the joint with the rear cross member, the degree of curvature of the inner rear connecting surface can be made gentler to avoid concentrating the load in the curvature start area, while transmitting the load transmitted to the area where the degree of curvature increases to the rear cross member. Furthermore, because the inner rear connecting surface is curved toward the rear cross member, the efficiency of vibration transmission to the rear cross member can be increased.

The lower rear connecting surface of the rear connecting portion is connected to each of the pair of side sills in an area where it overlaps with the arc-shaped inner rear connecting surface when viewed from the vehicle width direction, and is connected to each of the pair of side sills so as to overlap a predetermined suspension fixing portion that fixes the swinging suspension for the rear wheels, behind the area.

In this way, the lower rear connecting surface is connected to the side sill in the area where it overlaps with the inner rear connecting surface when viewed from the vehicle width direction, and is overlapped and connected to the suspension fixing part and side sill behind the area. This increases the number of vibration transmission paths between the rear side member and the side sill, allowing vibration to be transmitted and dispersed efficiently. In addition, rigidity can be increased by connecting the suspension fixing part, rear connecting part, and side sill to each other.

The vehicle undercarriage structure may further include a front connecting portion that connects the cross member and each of the pair of side sills forward of the rear connecting portion, and the front connecting portion may have an inner front connecting surface that connects the inner side surface of each of the pair of side sills to the front surface of the cross member and extends outward in the vehicle width direction toward the front of the vehicle, and a lower front connecting surface that is continuous with the lower edge of the inner front connecting surface and connects the lower surface of each of the pair of side sills to the lower surface of the cross member.

In this way, the front connecting portion has an inner front connecting surface that extends outward in the vehicle width direction toward the front of the vehicle, and a lower front connecting surface that connects the inner front connecting surface, side sill, and cross member. Therefore, vibrations transmitted to the cross member can be efficiently transmitted and dispersed to the pair of side sills via the inner front connecting surfaces that extend outward in the vehicle width direction toward the front of the vehicle. In addition, vibrations can be efficiently transmitted and dispersed in the vehicle width direction via the cross member between the inner rear connecting surface on either the left or right side and the inner front connecting surface on the opposite side.

The vehicle underbody structure further includes a pair of floor side members connected to a front member located at the front of the vehicle below the floor panel, each of the pair of floor side members having a rear end portion that extends outward in the vehicle width direction as it approaches each of the pair of side sills, the inner front connecting surface of the front connecting portion being connected to the inner side surface of the rear end portion of each of the pair of floor side members, and the lower front connecting surface of the front connecting portion being connected to the lower surface of each of the pair of side sills in the range between the rear end portion of each of the pair of floor side members and the cross member.

In this way, the inner front connecting surface of the front connecting part is connected to the inner side surface of the rear end part of the floor side member, and further, the lower front connecting surface is connected to the side sill. Therefore, vibrations can be transmitted and dispersed between the rear side member on either the left or right side and the floor side member on the opposite side via the rear connecting part, cross member, and front connecting part. In this way, the transmission paths of vibrations transmitted to the cross member and to the side sill can be increased, so vibrations can be dispersed more efficiently.

Another representative configuration of a vehicle undercarriage according to one embodiment of the present invention is a vehicle undercarriage having a floor panel that forms the floor surface of the vehicle, the vehicle undercarriage further comprising a front member located at the front of the underside of the floor panel, a rear member located rearward of the front member, a pair of floor side members that connect the front member and the rear member under the floor panel and have their front ends connected to each other in the vehicle width direction, a cross member that extends in the vehicle width direction and connects the pair of floor side members to form a closed cross section therein, a rear connecting portion that connects the cross member and each of the pair of floor side members, and a connecting portion that connects the cross member and the pair of floor side members forward of the rear connecting portion. and a front connecting portion connecting between each of the pair of floor side members and the cross member, the rear connecting portion having an inner rear connecting surface connecting the inner side surface of each of the pair of floor side members to the rear surface of the cross member and extending inward in the vehicle width direction toward the front of the vehicle, and a lower rear connecting surface continuing to the lower edge of the inner rear connecting surface and connecting the lower surface of each of the pair of floor side members to the lower surface of the cross member, the front connecting portion having an inner front connecting surface connecting the inner side surface of each of the pair of floor side members to the front surface of the cross member and extending outward in the vehicle width direction toward the front of the vehicle, and a lower front connecting surface continuing to the lower edge of the inner front connecting surface and connecting the lower surface of each of the pair of floor side members to the lower surface of the cross member.

In the above configuration, the rear connecting portion connects the inner side of the floor side member to the rear surface of the cross member with the inner rear connecting surface, and further connects the inner rear connecting surface, floor side member, and cross member with the lower rear connecting surface. Therefore, even if torsional vibration occurs in the floor panel around the left or right rear wheel side located diagonally from the front wheel when a large load is transmitted to the left or right front wheel, the floor side member and cross member are connected with the rear connecting portion, so this vibration can be transmitted to and dispersed by the highly rigid cross member. In addition, this torsional vibration is efficiently transmitted to the cross member via the inner rear connecting surface that extends inward in the vehicle width direction toward the front of the vehicle.

The front connecting portion also has an inner front connecting surface that extends outward in the vehicle width direction toward the front of the vehicle, and a lower front connecting surface that connects the inner front connecting surface, floor side member, and cross member. Therefore, vibrations transmitted to the cross member can be efficiently transmitted and dispersed to a pair of floor side members via the inner front connecting surface that extends outward in the vehicle width direction toward the front of the vehicle.

In this way, vibrations can be efficiently transmitted and dispersed in the vehicle width direction via the cross member between the inner rear connecting surface on either the left or right side and the inner front connecting surface on the opposite side. Therefore, with the above configuration, vibrations can be efficiently dispersed via the rear connecting portion, the cross member, and the front connecting portion, suppressing torsional vibrations of the floor panel and improving the vehicle's NV characteristics. Furthermore, since a pair of floor side members connect the front member and rear member below the floor panel, loads can be efficiently transmitted between the front member and rear member via the floor side members.

A preferred embodiment 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 embodiment are merely examples to facilitate understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same function and configuration are given the same reference numerals to avoid repeated explanation, and elements not directly related to the present invention are not shown. In this embodiment, connection includes cases where each member is directly connected and cases where each member is connected via an appropriate connecting member. Connection includes joining separate members together, and integration (bonding) where each member becomes the same member.

Figure 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 following figures, 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 cross member 108. 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 extend in the fore-and-aft direction of the vehicle along edges 109, 110 of the floor panel 102. The cross member 108 extends in the vehicle width direction below the floor panel 102, connecting the pair of side sills 104, 106 and forming a closed cross section inside.

The vehicle undercarriage 100 further includes a pair of rear side members 112, 114 and rear connecting portions 116, 118. The pair of rear side members 112, 114 are connected to the pair of side sills 104, 106, respectively, and extend further rearward. The rear connecting portions 116, 118 connect the cross member 108 to each of the pair of rear side members 112, 114.

The rear connecting portions 116, 118 have inner rear connecting surfaces 120, 122 and lower rear connecting surfaces 124, 126. The inner rear connecting surfaces 120, 122 connect the inner side surfaces 128, 130 of each of the pair of rear side members 112, 114 to the rear surface 132 of the cross member 108, and extend inward in the vehicle width direction toward the front of the vehicle. The lower rear connecting surfaces 124, 126 are continuous with the lower edges 134, 136 of the inner rear connecting surfaces 120, 122, and connect the lower surfaces 138, 140 of each of the pair of side sills 104, 106 to the lower surface 142 of the cross member 108.

In addition, in the vehicle undercarriage structure 100, a closed cross section is formed by the rear connecting parts 116, 118, the floor panel 102, the rear surface 132 of the cross member 108, the inner side surfaces 144, 146 of each of the pair of side sills 104, 106, and the inner side surfaces 128, 130 of each of the pair of rear side members 112, 114. Because a closed cross section is formed by each of these members, the rigidity of the rear connecting parts 116, 118, the floor panel 102, the cross member 108, the side sills 104, 106, and the rear side members 112, 114 can be increased, and floor vibration can be suppressed.

The inner rear connecting surfaces 120, 122 of the rear connecting parts 116, 118 are concave outward in the vehicle width direction as shown in the figure. Note that the term "arc" is not limited to an arc that is a part of a circle, but also includes an arc that is a part of an ellipse. Therefore, the inner rear connecting surfaces 120, 122 can prevent the load and vibration transmitted from the rear side members 112, 114 from concentrating locally, and can efficiently transmit and distribute the load and vibration to the cross member 108.

In addition, because the inner rear connecting surfaces 120, 122 are arc-shaped, loads and vibrations transmitted from the rear of the vehicle to the left rear side member 112, for example, can be more easily transmitted to the side sill 106 on the opposite side (right side) compared to when they are inclined linearly inward in the vehicle width direction.

The front ends 148, 150 of the pair of rear side members 112, 114 extend outward in the vehicle width direction as they approach the pair of side sills 104, 106, as shown by dotted lines in FIG. 1. The inner rear connecting surfaces 120, 122 are connected to the inner side surfaces 128, 130 of the front ends 148, 150 of the pair of rear side members 112, 114.

As a result, when vibrations are transmitted to the rear side members 112, 114 from the rear of the vehicle, the vibrations can be efficiently transmitted from the inner side surfaces 128, 130 of the front end portions 148, 150 of the rear side members 112, 114 to the inner rear connecting surfaces 120, 122 of the rear connecting portions 116, 118.

The vehicle undercarriage structure 100 further includes a rear cross member (first rear cross member 152) that extends in the vehicle width direction, and a second rear cross member 153. The first rear cross member 152 connects the inner side surfaces 128, 130 of the rear side members 112, 114 to each other. In addition, the inner rear connecting surfaces 120, 122 of the rear connecting parts 116, 118 are joined to the first rear cross member 152 so as to straddle the first rear cross member 152. This allows vibrations transmitted via the inner rear connecting surfaces 120, 122 to be dispersed and released to the first rear cross member 152.

As shown in the figure, the second rear cross member 153 is spaced rearward of the first rear cross member 152, extends in the vehicle width direction, and is joined to the rear side members 112, 114.

The arc-shaped inner rear connecting surfaces 120, 122 of the rear connecting parts 116, 118 start to curve or the degree of curvature increases forward from the joints 154, 156 with the first rear cross member 152. In this way, the arc-shaped inner rear connecting surfaces 120, 122 start to curve or the degree of curvature increases from the joints 154, 156 with the first rear cross member 152, so that it is possible to increase the efficiency of vibration transmission between the first rear cross member 152 and the arc-shaped inner rear connecting surfaces 120, 122 while avoiding localized concentration of load in a predetermined curvature start region where the curvature of the inner rear connecting surfaces 120, 122, where stress is likely to concentrate, begins.

As an example, when the inner rear connecting surfaces 120, 122 are curved starting from the joints 154, 156 with the first rear cross member 152, a part of the load acting on a predetermined curve start area from the rear can be transmitted to the first rear cross member 152 side. Also, when the inner rear connecting surfaces 120, 122 are curved starting from the joints 154, 156 with the first rear cross member 152, the degree of curvature of the inner rear connecting surfaces 120, 122 is made gentler to avoid the load concentrating in the predetermined curve start area, and the load transmitted to the predetermined area where the degree of curvature is larger can be transmitted to the first rear cross member 152. Furthermore, since the inner rear connecting surfaces 120, 122 are curved toward the first rear cross member 152 side, the transmission efficiency of vibration to the first rear cross member 152 can be improved.

The vehicle undercarriage 100 further includes front connecting portions 158, 160 and a pair of floor side members 162, 164. The front connecting portions 158, 160 connect the cross member 108 to each of the pair of side sills 104, 106 on the vehicle front side of the rear connecting portions 116, 118 as shown in the figure.

The front connecting portions 158, 160 have inner front connecting surfaces 166, 168 and lower front connecting surfaces 170, 172. The inner front connecting surfaces 166, 168 connect the inner side surfaces 144, 146 of each of the pair of side sills 104, 106 to the front surface 174 of the cross member 108, and extend outward in the vehicle width direction toward the front of the vehicle. The lower front connecting surfaces 170, 172 are continuous with the lower edges 176, 178 of the inner front connecting surfaces 166, 168, and connect the lower surfaces 138, 140 of each of the pair of side sills 104, 106 to the lower surface 142 of the cross member 108.

Thus, the front connecting portions 158, 160 have inner front connecting surfaces 166, 168 that extend outward in the vehicle width direction toward the front of the vehicle, and lower front connecting surfaces 170, 172 that connect the inner front connecting surfaces 166, 168, the side sills 104, 106, and the cross member 108.

As a result, vibrations transmitted to the cross member 108 can be efficiently transmitted and dispersed to the pair of side sills 104, 106, for example, via the arc-shaped inner front connecting surfaces 166, 168. In addition, vibrations can be efficiently transmitted and dispersed in the vehicle width direction, for example, via the cross member 108 between the arc-shaped inner rear connecting surface 120 on the left side and the arc-shaped inner front connecting surface 168 on the opposite side (right side).

The rear ends 180, 182 of the pair of floor side members 162, 164 extend outward in the vehicle width direction as they approach the pair of side sills 104, 106. The inner front connecting surfaces 166, 168 of the front connecting parts 158, 160 are connected to the inner side surfaces 184, 186 of the rear ends 180, 182 of the pair of floor side members 162, 164. The lower front connecting surfaces 170, 172 are connected to the lower surfaces 138, 140 of the pair of side sills 104, 106 in the range between the rear ends 180, 182 of the pair of floor side members 162, 164 and the cross member 108.

In this way, in the vehicle undercarriage structure 100, the inner front connecting surfaces 166, 168 of the front connecting parts 158, 160 are connected to the inner side surfaces 184, 186 of the rear ends 180, 182 of the floor side members 162, 164, and the lower front connecting surfaces 170, 172 are connected to the side sills 104, 106.

For this reason, for example, vibrations can be transmitted and dispersed between the rear side member 112 on the left side and the floor side member 164 on the opposite side (right side) via the rear connecting parts 116, 118, the cross member 108, and the front connecting parts 158, 160. Therefore, in the vehicle undercarriage structure 100, the transmission paths of vibrations transmitted to the cross member 108 and to the side sills 104, 106 can be increased, so that vibrations can be dispersed more efficiently.

Figure 2 is a diagram showing a part of the vehicle underbody structure 100 in Figure 1 as seen from another direction. The figure shows the rear side member 112, the rear connecting portion 116, and their surroundings. Figure 3 is a diagram of the vehicle underbody structure 100 in Figure 2 without the rear connecting portion 116. Note that point A in Figure 3 indicates the welding point of the rear connecting portion 116.

The inner rear connecting surface 120 of the rear connecting portion 116 has a front joint surface 188 that is joined to the rear surface 132 of the cross member 108, and a rear joint surface 190 that is joined to the rear side member 112. The inner rear connecting surface 120 further has an arc-shaped surface 192 that connects the front joint surface 188 and the rear joint surface 190, and a rear cross joint surface 194 that is joined to the first rear cross member 152.

The lower rear connecting surface 124 of the rear connecting portion 116 has a front outer end 196 that is joined to the inner side surface 144 of the side sill 104, and a rear outer end 198. The rear outer end 198 is joined to a rear suspension fixing portion 200. The rear suspension fixing portion 200 has a swing shaft portion 202 and a bracket 204 that is continuous with or overlaps the side sill 104.

The lower rear connecting surface 124 is connected to the side sill 104 in a region where it overlaps with the arcuate surface 190 of the inner rear connecting surface 120 when viewed from the vehicle width direction. The lower rear connecting surface 124 is also connected such that the rear outer end 198 located rearward in this region overlaps with the rear suspension fixing part 200 and the side sill 104.

As a result, the vehicle undercarriage structure 100 can increase the number of vibration transmission paths between the rear side members 112, 114 and the side sills 104, 106, allowing vibrations to be efficiently transmitted and dispersed. In addition, rigidity can be increased by connecting the suspension fixing part 200, the rear connecting part 116, and the side sill 104 to each other.

In area B enclosed by a dashed line in FIG. 3, the inner rear connecting surface 120 of the rear connecting portion 116 shown in FIG. 2 is joined to the first rear cross member 152. In area C, the inner rear connecting surface 120, the rear side member 112, and the side brace 206 are joined on the inside to increase connection rigidity. Note that in FIG. 3, part of the outline of the side brace 206 is shown by a dotted line. Note that the side brace 206 may be formed from part of the floor panel 102, and two inner rear connecting surfaces 120 and two rear side members 112 may be joined.

In addition, in area D, the three pieces are joined on the inside by the lower rear connecting surface 124 of the rear connecting part 116, the rear side member 112, and the swing shaft part 202 of the rear suspension fixing part 200, increasing the connection rigidity. In area E, the three pieces are joined in the vertical direction by the lower rear connecting surface 124, the rear side member 112, and the bracket 204 of the rear suspension fixing part 200, increasing the connection rigidity. Note that in area E, the side sill 104 may also be included in addition to these members, making a four-piece joint.

In addition, in area F, the lower rear connecting surface 124 of the rear connecting portion 116, the rear side member 112, and the first rear cross member 152 join the three pieces in the vertical direction to increase connection rigidity. In area G, the lower rear connecting surface 124, the first rear cross member 152, and the bracket 204 of the rear suspension fixing portion 200 join the three pieces in the vertical direction to increase connection rigidity. Furthermore, in area H, the lower rear connecting surface 124, the side sill 104, and the bracket 204 of the rear suspension fixing portion 200 join the three pieces in the vertical direction to increase connection rigidity.

As shown in FIG. 2, the first rear cross member 152 has a floor surface portion 208 and a bridging portion 210. The bridging portion 210 is a portion that connects the rear side members 112, 114 to each other. At the joint 154, the underside 214, front surface 216, and rear surface 218 of the outer end portion 212 of the bridging portion 210 are joined to the rear cross joint surface 194 of the inner rear connecting surface 120.

In the vehicle undercarriage structure 100, as described above, the rear connecting parts 116, 118 connect the inner side surfaces 128, 130 of the rear side members 112, 114 to the rear surface 132 of the cross member 108 at the inner rear connecting surfaces 120, 122. Therefore, even if a large load is transmitted to either the left or right front wheel, in this embodiment the left front wheel, and a torsional vibration occurs in the floor panel 102 centered on the right rear wheel side located on the diagonal line I (see FIG. 1) of the left front wheel, the rear side members 112, 114 and the cross member 108 are connected by the rear connecting parts 116, 118, so that the torsional vibration can be transmitted to and dispersed by the highly rigid cross member 108.

This torsional vibration is also transmitted to the cross member 108 via the arc-shaped inner rear connecting surfaces 120, 122. FIG. 1 shows an example of a vibration transmission path J. This vibration transmission path J includes, for example, a path that passes through the side sill 104 side, and a path that passes through the inner rear connecting surface 120 and the lower connecting surface 124. Therefore, this torsional vibration can be transmitted and dispersed to the same right side sill 104 and rear side member 112 via the cross member 108 and, for example, the right rear connecting portion 116.

Furthermore, in the vehicle underbody structure 100, the lower rear connecting surfaces 124, 126 are connected to the lower surfaces 138, 140 of the side sills 104, 106 in succession to the lower edges 134, 136 of the inner rear connecting surfaces 120, 122. Therefore, for example, vibrations in the vehicle width direction transmitted from the rear suspension fixing part 200 to the rear side member 112 can be transmitted to the side sill 104 connected to the rear side member 112 and dispersed, and can also be transmitted to the opposite side sill 106 and rear side member 114 via the arc-shaped inner rear connecting surface 120 of the rear connecting part 116, the cross member 108, and the opposite rear connecting part 118. Therefore, according to the vehicle underbody structure 100, the load and vibration can be efficiently transmitted from the wheel to which the vehicle load is applied to the wheel side arranged diagonally from the wheel, suppressing the torsional vibration of the floor panel 102 and improving the NV characteristics of the vehicle.

Note that the rear connecting portions 116, 118 and the front connecting portions 158, 160 are separate from the cross member 108 which forms a closed cross section, but they may be integrated with the cross member 108. Also, while the vehicle undercarriage structure 100 includes both the rear connecting portions 116, 118 and the front connecting portions 158, 160, this is not limited, and only one of them may be included. Furthermore, although the cross member 108 is described as forming a closed cross section, an appropriate configuration that does not form a closed cross section may be adopted as long as it has the rigidity and strength to suppress floor vibration.

Figure 4 shows a modified example of the vehicle underbody structure 100 of Figure 1. The modified vehicle underbody structure 100A has braces 220, 222 provided at the rear connecting portion 116A and the front connecting portion 158A, respectively. These braces 220, 222 are arranged so as to overlap in the fore-and-aft direction of the vehicle via the cross member 108 as shown, so that loads and vibrations can be transmitted in the fore-and-aft direction of the vehicle between the floor side member 162A and the rear side member 112.

In addition, in the vehicle underbody structure 100A, the rear connecting portion 118A and the front connecting portion 160A have smaller areas than the rear connecting portion 118 and the front connecting portion 160 of the vehicle underbody structure 100. This makes it possible to reduce surface vibrations at the rear connecting portion 118A and the front connecting portion 160A. The floor side members 162A, 164A have their front ends 224, 226 connected in the vehicle width direction via a connecting member 228.

Even with this type of vehicle substructure 100A, the torsional vibration of the floor panel 102 can be suppressed, improving the vehicle's noise and vibration characteristics.

Figure 5 shows another modified example of the vehicle underbody structure 100 of Figure 1. The modified vehicle underbody structure 100B does not have the front connecting parts 158, 160 of the vehicle underbody structure 100, and arc-shaped floor side members 162B, 164B are connected to the cross member 108 from the front side of the vehicle. The floor side members 162B, 164B have their front ends 230, 232 connected in the vehicle width direction via a connecting member 228.

In addition, in the vehicle undercarriage structure 100B, the shape of the lower rear connecting surfaces 234, 236 of the rear connecting parts 116B, 118B is different from the shape of the lower rear connecting surfaces 124, 126 of the rear connecting parts 116, 118 of the vehicle undercarriage structure 100. In other words, the lower rear connecting surfaces 234, 236 are arched not only on the inside in the vehicle width direction but also on the outside in the vehicle width direction, which makes it possible to better prevent loads and vibrations from concentrating locally.

Figure 6 is a bottom view showing a vehicle substructure 100C according to a second embodiment of the present invention. The vehicle substructure 100C includes a front member 238 and a rear member 240. The front member 238 is a member located at the front of the lower side of the floor panel 102, and includes, for example, a front suspension frame 242. The rear member 240 is a member located rearward of the front member 238, and includes, for example, rear side members 112, 114.

The vehicle substructure 100C also includes a pair of floor side members 162C, 164C. The pair of floor side members 162C, 164C connect the front member 238 and the rear member 240 below the floor panel 102, and as shown in the figure, the front ends 244, 246 are connected to each other in the vehicle width direction.

The vehicle substructure 100C further includes a cross member 248, rear connecting portions 250 and 252, and front connecting portions 254 and 256. The cross member 248 extends in the vehicle width direction and connects a pair of floor side members 162C and 164C to form a closed cross section inside.

The rear connecting parts 250, 252 connect the cross member 248 to each of the pair of floor side members 162C, 164C. The rear connecting parts 250, 252 have inner rear connecting surfaces 258, 260. The inner rear connecting surfaces 258, 260 connect the inner side surfaces 262, 264 of each of the pair of floor side members 162C, 164C to the rear surface 266 of the cross member 248, and extend inward in the vehicle width direction toward the front of the vehicle.

The rear connection portions 250, 252 further have lower rear connection surfaces 268, 270. The lower rear connection surfaces 268, 270 are continuous with the lower edges 272, 274 of the inner rear connection surfaces 258, 260 and connect the lower surfaces 276, 278 of the pair of floor side members 162C, 164C to the lower surface 280 of the cross member 248.

The front connecting parts 254, 256 connect the cross member 248 to each of the pair of floor side members 162C, 164C on the vehicle front side of the rear connecting parts 250, 252. The front connecting parts 254, 256 have inner front connecting surfaces 282, 284 and lower front connecting surfaces 286, 288.

The inner front connecting surfaces 282, 284 connect the inner side surfaces 262, 264 of each of the pair of floor side members 162C, 164C to the front surface 290 of the cross member 248, and extend outward in the vehicle width direction toward the front of the vehicle. The lower front connecting surfaces 286, 288 are continuous with the lower edges 292, 294 of the inner front connecting surfaces 282, 284, and connect the lower surfaces 276, 278 of each of the pair of floor side members 162C, 164C to the lower surface 280 of the cross member 248.

Therefore, in the vehicle underbody structure 100C, the rear connecting parts 250, 252 connect the inner side surfaces 262, 264 of the floor side members 162C, 164C to the rear surface 266 of the cross member 248 via the inner rear connecting surfaces 258, 260, and further connect the inner rear connecting surfaces 258, 260, the floor side members 162C, 164C, and the cross member 248 via the lower rear connecting surfaces 268, 270. Therefore, even if a torsional vibration occurs in the floor panel 102 around the left or right rear wheel side located diagonally from the front wheel when a large load is transmitted to the left or right front wheel, the floor side members 162C, 164C and the cross member 248 are connected to each other via the rear connecting parts 250, 252, so that the vibration can be transmitted to the highly rigid cross member 248 and dispersed. In addition, the vibration is efficiently transmitted to the cross member 248 via the arc-shaped inner rear connecting surfaces 258, 260.

The front connecting portions 254, 256 also have inner front connecting surfaces 282, 284 that extend outward in the vehicle width direction toward the front of the vehicle, and lower front connecting surfaces 286, 288 that connect the inner front connecting surfaces 282, 284, the floor side members 162C, 164C, and the cross member 248. Therefore, vibrations transmitted to the cross member 248 can be efficiently transmitted and dispersed to the pair of floor side members 162C, 164C, for example, via the arc-shaped inner front connecting surfaces 282, 284.

This allows vibrations to be efficiently transmitted and dispersed in the vehicle width direction via the cross member 248 between the arc-shaped inner rear connecting surface 258 or 260 on either the left or right side and the arc-shaped inner front connecting surface 284 or 282 on the opposite side.

Therefore, according to the vehicle lower structure 100C, vibrations can be efficiently dispersed via the rear connecting parts 250, 252, the cross member 248, and the front connecting parts 254, 256, and torsional vibrations of the floor panel 102 can be suppressed to improve the NV characteristics of the vehicle. Furthermore, in the vehicle lower structure 100C, a pair of floor side members 162C, 164C connect the front member 238 and the rear member 240 below the floor panel 102, so that loads can be efficiently transmitted between the front member 238 and the rear member 240 via the floor side members 162C, 164C.

As a modification of the present invention, the rear connecting portion, rear side member, side sill and cross member may be provided on the upper surface side of the floor panel. In this case, the terms "lower surface," "lower side" and "lower edge" described above are replaced with "upper surface," "upper side" and "upper edge," respectively. For example, a typical vehicle underbody structure includes a floor panel that forms the floor surface of the vehicle, a pair of side sills that extend in the vehicle longitudinal direction along the edge of the floor panel, a cross member that extends in the vehicle width direction above the floor panel and connects the pair of side sills to form a closed cross section inside, a pair of rear side members that are connected to the pair of side sills and extend further rearward, and a rear connecting portion that connects the cross member to each of the pair of rear side members, the rear connecting portion having an inner rear connecting surface that connects the inner side surface of each of the pair of rear side members to the rear surface of the cross member and extends inward in the vehicle width direction toward the front of the vehicle, and an upper rear connecting surface that is continuous with the upper edge of the inner rear connecting surface and connects the upper surface of each of the pair of side sills to the upper surface of the cross member.

The above describes preferred embodiments of the present invention with reference to the attached drawings, but it goes without saying that the present invention is not limited to such examples. 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, 100C...vehicle underbody structure, 102...floor panel, 104, 106...side sill, 108, 248...cross member, 109, 110...edge of floor panel, 112, 114...rear side member, 116, 116A, 116B, 118, 118A, 118B, 250, 252...rear connection portion, 120, 122, 258, 260...inner rear connection surface, 124, 126, 234, 236, 268, 270...lower rear connection surface, 128, 130...inner side of rear side member, 132, 266...of cross member rear surface, 134, 136, 272, 274...lower edge of inner rear connecting surface, 138, 140...lower surface of side sill, 142, 280...lower surface of cross member, 144, 146...inner side surface of side sill, 148, 150...front end of rear side member, 152...first rear cross member, 153...second rear cross member, 154, 156...joint, 158, 158A, 160, 160A, 254, 256...front connecting portion, 162, 162A, 162B, 162C, 164, 164A, 164B, 164C...floor side member, 166, 16 8, 282, 284...inner front connecting surface, 170, 172, 286, 288...lower front connecting surface, 174, 290...front surface of cross member, 176, 178, 292, 294...lower edge of inner front connecting surface, 180, 182...rear end of floor side member, 184, 186...inner side surface of rear end of floor side member, 188...front joint surface of inner rear connecting surface, 190...rear joint surface, 192...arc-shaped surface, 194...rear cross joint surface, 196...front outer end of lower rear connecting surface, 198...rear outer end, 200...suspension fixing portion, 20 2...oscillating shaft portion, 204...bracket, 206...side brace, 208...floor surface portion of rear cross member, 210...bridge portion, 212...outer end portion, 214...lower surface of outer end portion, 216...front surface of outer end portion, 218...rear surface of outer end portion, 220, 222...brace, 224, 226, 230, 232, 244, 246...front end of floor side member, 238...front member, 240...rear member, 242...front suspension frame, 262, 264...inner side surface of floor side member, 276, 278...lower surface of floor side member

Claims (9)

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 front-rear direction of the vehicle along edges of the floor panel;
a cross member extending below the floor panel in the vehicle width direction and connecting the pair of side sills;
a pair of rear side members respectively connected to the pair of side sills and extending rearward;
a rear connecting portion connecting the cross member to each of the pair of rear side members,
The rear connection portion is
an inner rear connecting surface that connects an inner side surface of each of the pair of rear side members to a rear surface of the cross member and extends inward in a vehicle width direction toward the front of the vehicle;
a lower rear connecting surface that is continuous with a lower edge of the inner rear connecting surface and connects the lower surface of each of the pair of side sills to the lower surface of the cross member. The vehicle underbody structure according to claim 1, characterized in that a closed space is formed by the rear connecting portion, the floor panel, the rear surface of the cross member, the inner side surfaces of each of the pair of side sills, and the inner side surfaces of each of the pair of rear side members. The vehicle underbody structure according to claim 1 or 2, characterized in that the inner rear connecting surface of the rear connecting portion is arc-shaped. Each of the pair of rear side members has a front end portion that extends outward in a vehicle width direction as it approaches each of the pair of side sills,
4. The vehicle underbody structure according to claim 3, wherein an inner rear connecting surface of the rear connecting portion is connected to inner side surfaces of front ends of each of the pair of rear side members. The vehicle lower structure further includes a rear cross member extending in a vehicle width direction and connecting inner side surfaces of the pair of rear side members to each other,
5. The vehicle underbody structure according to claim 3, wherein an inner rear connecting surface of the rear connecting portion is joined to the rear cross member so as to straddle the rear cross member. The vehicle underbody structure described in claim 5, characterized in that the arc-shaped inner rear connecting surface of the rear connecting portion starts to curve or the degree of curvature increases from the joint with the rear cross member toward the front. The lower rear connecting surface of the rear connecting portion is
a region overlapping with the arc-shaped inner rear connecting surface as viewed in the vehicle width direction, the region being connected to each of the pair of side sills,
7. The vehicle undercarriage structure according to claim 5 or 6, characterized in that, rear of the region, a predetermined suspension fixing portion for fixing a swinging suspension for a rear wheel is connected to each of the pair of side sills so as to overlap each other. The vehicle underbody structure further includes a front connection portion that connects the cross member and each of the pair of side sills on a vehicle front side relative to the rear connection portion,
The front connecting portion is
an inner front connecting surface extending outward in a vehicle width direction toward the front of the vehicle ;
8. The vehicle underbody structure according to claim 1, further comprising a lower front connecting surface that is continuous with a lower edge of the inner front connecting surface and connects the lower surface of each of the pair of side sills to the lower surface of the cross member. The vehicle underbody structure further includes a pair of floor side members connected to a front member located at the front of the vehicle below the floor panel,
each of the pair of floor side members has a rear end portion that extends outward in a vehicle width direction as it approaches each of the pair of side sills,
The inner front connecting surface of the front connecting portion is connected to the inner side surface of each of the rear ends of the pair of floor side members,
9. The vehicle underbody structure according to claim 8, wherein the lower front connecting surface of the front connecting portion is connected to the lower surface of each of the pair of side sills in the area between the rear end portions of each of the pair of floor side members and the cross member.

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