JP4415809B2 - Lower body structure of automobile - Google Patents

Description

  The present invention relates to a lower body structure of an automobile, and in particular, includes a floor cross member having a curved portion extending in the vehicle width direction and protruding upward in the vicinity of a boundary step portion between a main floor panel and a rear floor panel. The present invention relates to a fuel tank provided.

  2. Description of the Related Art Conventionally, a structure in which a fuel tank is provided behind a boundary step portion (hereinafter also referred to as a kick-up portion in the present specification) between a main floor panel and a rear floor panel is known. For example, in Patent Document 1, between each rear side member (corresponding to a rear side frame in the present specification) extending in the front-rear direction in the vicinity of both ends in the vehicle width direction behind the kick-up portion, it is disposed over substantially the entire width. A fuel tank is shown. In recent years, in order to satisfy the demand for increasing the capacity of fuel tanks, a configuration that is as wide as possible has been adopted.

Further, a floor cross member, which is a rigid member extending in the vehicle width direction, is disposed near the kick-up portion. For example, Patent Document 2 discloses a cross member (corresponding to a floor cross member in the present specification) in the vicinity of a kick-up portion in an automobile in which a fuel tank is disposed behind the kick-up portion and on one side in the vehicle width direction. What we have is shown. The cross member is provided with a reinforcement integral with the cross member at a position outside the fuel tank in the vehicle width direction. The cross member and reinforcement form a closed cross section when viewed from the side, so that the rigidity of the cross member is increased, and deformation of the fuel tank or the like during a side collision (collision from the side surface) is suppressed. ing.
JP-A-8-301139 JP 2000-272544 A

  However, depending on the layout situation of the parts and the shape of the fuel tank, there is a problem that even in the structure as described in Patent Document 2, deformation of the fuel tank at the time of a side collision may not be sufficiently suppressed.

  Usually, an exhaust pipe, a propeller shaft, and the like (hereinafter collectively referred to as a floor lower member) are disposed below the main floor panel and the rear floor panel. In order to secure the minimum ground clearance, these need to be arranged at a certain high position. However, since the floor lower member and the floor cross member are arranged so as to be substantially orthogonal, if the upper end of the floor lower member protrudes above the lower end of the floor cross member, they interfere with each other. In such a case, an upwardly curved portion is provided on the floor cross member side to avoid interference.

  However, providing such a curved portion on the floor cross member makes it easy to increase the amount of intrusion (the amount of deformation to the inside of the vehicle) at the time of a side collision. In particular, when it is necessary to set the upper end of the lower member at a relatively high position, the bending degree of the bending portion must be increased, which is a disadvantageous condition for increasing the amount of penetration.

  On the other hand, a fuel tank that is as wide as possible as disclosed in Patent Document 1 is susceptible to side impacts even with a relatively small amount of intrusion, which is disadvantageous in suppressing deformation of the fuel tank. It has become.

  Furthermore, in order to increase the capacity of the fuel tank, the height of the fuel tank is also increasing. When the height of the fuel tank is increased, a so-called saddle type fuel tank shape is employed in which the lower surface is curved upward while avoiding interference with the floor lower member. When the upper end of the floor lower member is set high, the degree of curvature of the lower surface of the fuel tank needs to be increased, and the rigidity against the load from the side is reduced. That is, it is disadvantageous for suppressing deformation at the time of a side collision.

  As described above, when the upper end of the floor lower member is set at a relatively high position and a wide fuel tank is mounted, unfavorable conditions overlap in suppressing deformation of the fuel tank at the time of a side collision. . In such a case, the structure as shown in Patent Document 2 is no longer sufficient, and a structure with increased rigidity against side collision is required.

  In view of the circumstances as described above, the present invention suppresses intrusion at the time of a side collision while establishing a layout that avoids interference between a floor lower member whose upper end is set at a relatively high position and a floor cross member. Another object of the present invention is to provide a lower body structure of an automobile capable of suppressing deformation at the time of a side collision even when a wide fuel tank is mounted.

  The present invention for solving the above-described problems includes a fuel tank disposed substantially in the center in the vehicle width direction behind a boundary step portion (kick-up portion) between the main floor panel and the rear floor panel, the main floor panel, A floor lower member that is long in the front-rear direction and a rigid member that extends in the vehicle width direction in the vicinity of the boundary step portion at a substantially center in the vehicle width direction below the rear floor panel, and is disposed above the floor lower member. And a floor cross member having a curved portion that protrudes upward so as to avoid interference with the floor lower member, and is integrated with the floor cross member above the curved portion. And extends substantially linearly in the vehicle width direction over at least substantially the entire width of the fuel tank, and the cross section perpendicular to the axial direction is a closed cross section. Characterized by comprising a Jo closed-section member.

  This structure includes a rear side frame that is a rigid member extending in the front-rear direction, particularly in the vicinity of both ends in the vehicle width direction, and the fuel tank is disposed between the rear side frames over substantially the entire width. It is suitable for.

  The linear closed cross-section member is preferably a pipe member, for example.

  Further, the floor cross member is provided with a vertical wall that is erected substantially vertically and has an upper end joined to the rear floor panel, and includes a substantially U-shaped cross section in a side view, and the linear cross section on the U-shaped cross section. A storage member configured to store the closed cross-section member extending in the vehicle width direction may be configured to be joined to the vertical wall on the open surface side of the U-shaped cross-section.

  Further, the floor cross member includes a horizontal wall disposed substantially horizontally and having a front end joined to the main floor panel. The floor cross member is disposed integrally with the floor cross member in the vicinity of the curved portion, and the vertical cross member. It is good also as a structure provided with the reinforcement member which joins a wall and the said horizontal wall, and forms the closed cross section which surrounds the said linear closed cross section member.

  Further, the linear closed cross-section member may be provided integrally with the floor cross member in the vicinity of both ends in the vehicle width direction, and may include a box member having a wall surface extending in the front-rear direction and forming a closed cross section in front view. .

  According to the lower body structure of an automobile of the present invention, even when the floor cross member has a relatively large curved portion, the linear closed cross-section member can ensure rigidity against a load from the side. That is, it is possible to increase the rigidity of the floor cross member while establishing a layout that avoids interference between the floor lower member such as the propeller shaft and the exhaust pipe and the floor cross member. In addition, since the linear closed cross-section member is provided over substantially the entire width of the fuel tank, the linear closed cross-section member can directly prevent the intrusion of the counterpart collision object that reaches the fuel tank. Therefore, for example, even when a wide fuel tank that is disposed across the entire width of the gap between the rear side frames is mounted, deformation at the time of the side collision can be effectively suppressed. it can.

  If the linear closed cross-section member is a pipe member, the cross-sectional secondary moment can be made larger than that of a solid member having the same cross-sectional area. That is, a structure that is superior to the deformation in the bending mode can be obtained. Among pipe members, a round pipe or a polygonal pipe close to a circle is particularly advantageous for the deformation of the bending mode.

  When the storage member shown in claim 4 is provided, the U-shaped cross section and the floor cross member form a closed cross section in a side view, so that a double closed cross section is formed together with the linear closed cross section member, The rigidity of the floor cross member is further increased. Further, the linear closed cross-section member and the floor cross member can be easily joined by the storage member. That is, the linear closed cross-section member may be stored in advance in the U-shaped cross section of the storage member and joined, and then the open surface side of the U-shaped cross section and the floor cross member may be joined. This is particularly effective when a round pipe or the like that is difficult to be directly joined to the floor cross member is employed as the linear closed cross-section member.

  If the reinforcing member shown in claim 5 is provided, a further closed cross section can be formed in the vicinity of the curved portion of the floor cross member by the vertical and horizontal walls of the floor cross member and the reinforcing member. That is, effective local reinforcement can be performed on the curved portion with reduced rigidity.

  When the box member shown in claim 6 is provided, the load from the side is received by both the linear closed cross-section member and the box member, so that intrusion at the time of a side collision can be further suppressed. Further, since the box member forms a closed cross section when viewed from the front, it has high rigidity in the front-rear direction. Therefore, it is possible to suppress the deformation of the floor cross member in the front-rear direction during a front-rear collision.

  In addition, the front-back, left-right, up-down directions in this specification point out the direction seen from the driver | operator who seated in the driver's seat. That is, the vehicle width direction is synonymous with the left-right direction. Further, the front view means a state viewed from a viewpoint facing the front end of the vehicle.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a main part of a lower body structure 1 for an automobile according to an embodiment of the present invention. A substantially horizontal main floor panel 10 (indicated by a two-dot chain line) is provided in the vicinity of the center in the front-rear direction at the bottom of the vehicle. The rear end is a kick-up portion 10a (boundary stepped portion, indicated by a two-dot chain line) that rises slightly inclined backward. A rear floor panel 12 that extends substantially horizontally is joined to the upper end of the kick-up portion 10a. The main floor panel 10 and the rear floor panel 12 are provided between both side sills 2 that are rigid members extending in the front-rear direction at both lower portions of the vehicle. In FIG. 1, the side sill 2 on the right side (left side in the drawing) is shown.

  A floor cross member 3 (so-called No. 3 cross member), which is a rigid member extending in the vehicle width direction between both side sills 2, is provided below the vicinity of the kick-up portion 10a. The floor cross member 3 is a member having a substantially L-shaped cross section in a side view, and is disposed substantially horizontally and has a floor cross member lower wall 3b (horizontal wall) whose front end is joined to the main floor panel 10; The floor cross member lower wall 3b is a floor cross member rear wall 3a (vertical wall) that rises slightly rearward from the rear end and is joined to the rear floor panel 12 at the upper end.

  A floor lower member (propeller shaft 18 and exhaust pipe 19 in the present embodiment) that is long in the front-rear direction is disposed substantially at the center in the vehicle width direction below the floor cross member lower wall 3b. The floor cross member 3 is provided with a floor cross member curved portion 3c that protrudes upward so as to avoid interference therewith.

  A wide fuel tank 15 is provided behind the floor cross member rear wall 3a. The bottom surface of the fuel tank 15 is located lower than the floor cross member lower wall 3b, and the fuel tank curved portion that protrudes upward so as to avoid interference with the propeller shaft 18 and the exhaust pipe 19 is the same as the floor cross member curved portion 3c. 15a (refer FIG. 3) is provided. That is, the fuel tank 15 is a so-called vertical fuel tank.

  The floor cross member 3 is joined directly or indirectly to the pipe member 20, the overlap panel 21, the storage member 22, the reinforcing member 24, and the box member 26. Detailed description.

  2 is a schematic bottom view of FIG. 1, and FIG. 3 is a schematic front view of FIG. As shown in FIGS. 2 and 3, the propeller shaft 18 and the exhaust pipe 19 are disposed long in the front-rear direction at the approximate center in the vehicle width direction. These occupy partially overlapping spaces in a plan view, and avoid mutual interference by offsetting in the vertical direction. In the present embodiment, the propeller shaft 18 is located above the exhaust pipe 19 in the vicinity of the floor cross member 3.

  In order to avoid interference with the floor cross member 3 and the fuel tank 15, it is desirable that the installation height of the propeller shaft 18 and the exhaust pipe 19 is low. However, on the other hand, it is necessary to ensure a predetermined minimum ground clearance, and since the installation height of the exhaust pipe 19 has a lower limit, the upper end of the propeller shaft 18 is relatively high. For this reason, for example, the degree of curvature of the floor cross member curved portion 3c and the fuel tank curved portion 15a is greater than when the propeller shaft 18 is not provided and interference with the exhaust pipe 19 only has to be avoided.

  As shown in FIG. 2, a rear side frame 5 is provided as a rigid member that is connected to the rear ends of both side sills 2 and extends further rearward. A rear cross member 4 (so-called No. 4 cross member) that is a rigid member extending in the vehicle width direction is provided between the rear side frames 5.

  The fuel tank 15 is supported by a pair of left and right mounting belts 9 stretched in the front-rear direction. The attachment belt 9 has a front end fixed to the floor cross member 3 and a rear end fixed to the inner overhang portion of the rear side frame 5 via a belt support portion 9a. As shown in FIG. 2, the fuel tank 15 is provided between the two rear side frames 5 in a plan view, but the width thereof is slightly smaller than the distance between the rear side frames 5 in the vehicle width direction. That is, the fuel tank 15 is set to the maximum width as a fuel tank disposed between the rear side frames 5.

  4 is a cross-sectional view taken along line IV-IV in FIG. In this cross section, the pipe member 20, the superposed panel 21 and the storage member 22 are joined directly or indirectly to the floor cross member rear wall 3a. As shown in FIG. 3, these members are members that extend in the vehicle width direction over substantially the entire width of the fuel tank 15 in a front view.

  The overlapping panel 21 is a plate-like member having a substantially L-shaped cross section in a side view, and is joined to the front surface of the floor cross member rear wall 3a and the upper surface of the floor cross member lower wall 3b so as to be substantially overlapped.

  The storage member 22 is a member having a hat-shaped cross section in a side view. That is, it is composed of a U-shaped cross-section 22a having a substantially U-shaped cross-section, and a folded portion 22b in which both upper and lower edges of the U-shaped cross-section 22a are folded back about 90 degrees. The folded portion 22b is joined to the floor cross member rear wall 3a via the overlapping panel 21 with the open surface side of the U-shaped cross-section 22a facing rearward. Therefore, the U-shaped cross section 22a and the floor cross member rear wall 3a form a closed cross section.

  The pipe member 20 (linear closed cross-section member) is stored in the U-shaped cross-section 22 a of the storage member 22. The pipe member 20 is a round pipe having a tubular cross section in a side view. The pipe member 20 is joined directly to the floor cross member rear wall 3a via the storage member 22 by being joined to the U-shaped cross section 22a.

  5 is a cross-sectional view taken along line III-III in FIG. This cross-sectional position is the maximum height position of the propeller shaft 18. For this reason, it is also a curved vertex position of the floor cross member curved portion 3c and the fuel tank curved portion 15a. Since the vertical installation space of the pipe member 20 and the storage member 22 is narrow at this cross-sectional position, the storage member 22 leaves a U-shaped cross-section 22a, and the folded portion 22b is cut off.

  A reinforcing member 24 is provided so as to surround the pipe member 20 and the storage member 22. As shown in FIG. 1 and FIG. 3, the reinforcing member 24 is provided over substantially the entire width of the floor cross member curved portion 3c in the vehicle width direction, and the floor cross member lower wall 3b and the floor cross member rear wall 3a are joined to each other. 21 is a plate-like member joined in a substantially inverted L shape via 21. Therefore, the floor cross member rear wall 3a, the floor cross member lower wall 3b, and the reinforcing member 24 form a closed section in a side view, and the pipe member 20 and the storage member 22 are configured to pass through the closed section. ing.

  6 is a cross-sectional view taken along the line V-V in FIG. This cross-sectional position is near the end of the pipe member 20. Even at this cross-sectional position, the storage member 22 leaves a U-shaped cross-section 22a, and the folded-back portion 22b is cut off. A box member 26 is provided below the storage member 22. The box member 26 is a box-shaped member having an open front surface. The upper edge is folded upward by about 90 degrees, and the folded portion is joined to the storage member 22. Further, the rear surface and the lower surface are joined to the floor cross member rear wall 3 a and the floor cross member lower wall 3 b through the overlapping panel 21. The upper and lower surfaces and the left and right surfaces of the box member 26 form a rectangular wall surface (having a closed cross section when viewed from the front) that is erected in the front-rear direction. The box member 26 is also provided symmetrically on the other end side of the pipe member 20.

  The lower body structure 1 of the automobile having the above configuration acts as follows at the time of a side collision. When an excessive load is received due to a side collision in the vicinity of the floor cross member 3, the side sill 2 and the floor cross member 3 are deformed to some extent while absorbing an impact. However, since the rigidity of the floor cross member 3 is sufficiently increased, entry into the fuel tank 15 is suppressed.

  Since the floor cross member 3 itself has a relatively large floor cross member curved portion 3c at the center in the vehicle width direction, it is disadvantageous for suppressing intrusion at the time of a side collision. However, the disadvantage is eliminated by the pipe member 20, the storage member 22, the reinforcing member 24, and the box member 26.

  First, since the pipe member 20 is a straight round pipe having the most advantageous shape against deformation in the bending mode, by joining to the floor cross member 3, the rigidity of the floor cross member 3 against the load from the side is remarkably increased. ing. Moreover, since the pipe member 20 is provided over substantially the entire width of the fuel tank 15, it is possible to directly suppress the intrusion of the opponent collision object that reaches the fuel tank 15 by the pipe member 20.

  The storage member 22 forms a closed cross section in a side view by joining the U-shaped cross-section 22 a to the floor cross member via the overlapping panel 21. Since the closed cross section and the closed cross section of the pipe member 20 form a double closed cross section, the rigidity of the floor cross member 3 is further enhanced.

  The reinforcing member 24 is joined to the floor cross member rear wall 3a and the floor cross member lower wall 3b through the overlapping panel 21, thereby forming a closed cross section in a side view. Since the closed cross section and the closed cross section of the pipe member 20 form a closed cross section that is double (a triple where the folded portion 22b of the storage member 22 is provided), the floor cross member curved portion 3c has a closed cross section. Effective local reinforcement.

  The box member 26 is provided in the vicinity of both ends of the pipe member 20 and receives a load from the side together with the pipe member 20. Yes. Since the box member 26 has a closed cross section when viewed from the front, the rigidity in the front-rear direction of the floor cross member 3 is also increased. Therefore, it also has an effect of suppressing the deformation of the floor cross member 3 in the front-rear direction during a front-rear collision.

  As other operational effects, the provision of the storage member 22 makes it easy to join the pipe member 20 to the floor cross member rear wall 3a (directly the polymerization panel 21). That is, since the shape of the pipe member 20 is a round pipe, the operation of positioning and the like tends to be complicated to join this directly to the polymerization panel 21. Therefore, by configuring as in this embodiment, the pipe member 20 is stored in advance in the U-shaped cross section 22a of the storage member 22 and joined, and then the open surface side of the U-shaped cross section 22a and the polymerization panel By joining 21, the joining work can be facilitated.

  As described above, according to the configuration of the present embodiment, a layout that avoids interference between the propeller shaft 18 and the exhaust pipe 19 and the floor cross member 3 is established, and intrusion at the time of a side collision is suppressed. Even when a fuel tank is mounted, deformation at the time of a side collision can be suppressed.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications may be made within the scope of the claims. For example, instead of the pipe member 20, a solid linear member may be used. Alternatively, a polygonal pipe other than a round pipe may be used. However, if a pipe member, particularly a round pipe, is used as in this embodiment, there is an advantage that the effect of improving the rigidity against the increase in weight can be maximized.

  The floor cross member curved portion 3c does not necessarily have to be provided in order to avoid interference with the propeller shaft 18 and the exhaust pipe 19. You may avoid interference with either one or another member.

  The floor cross member 3 does not necessarily have a substantially L-shaped cross section in a side view as in the present embodiment. For example, it may have a rectangular closed cross section in a side view. However, the effect of the present invention can be remarkably exhibited when the shape has a relatively large influence on rigidity reduction due to the floor cross member bending portion 3c as in the present embodiment.

  The storage member 22 does not necessarily have a hat-shaped cross section in a side view. For example, both the upper and lower or one folded portion 22b may be folded inside the U-shaped cross-sectional portion 22a. Further, the folded portion 22b may be provided only on one of the upper and lower sides.

It is a principal part perspective view of the lower vehicle body structure of the motor vehicle which concerns on embodiment of this invention. It is a schematic bottom view of FIG. It is a schematic front view of FIG. It is the IV-IV sectional view taken on the line of FIG. It is the III-III sectional view taken on the line of FIG. It is the VV sectional view taken on the line of FIG.

Explanation of symbols

1 Car lower body structure 3 Floor cross member 3a Floor cross member rear wall (vertical wall)
3b Floor cross member lower wall (horizontal wall)
3c Floor cross member curved part (curved part)
5 Rear side frame 10 Main floor panel 10a Kick-up part (boundary step part)
12 Rear floor panel 15 Fuel tank 18 Propeller shaft (lower floor member)
19 Exhaust pipe (lower floor member)
20 Pipe member (Linear closed section member)
22 Storage member 22a U-shaped cross section 24 Reinforcement member 26 Box member

Claims (6)

A fuel tank disposed at a substantially center in the vehicle width direction behind the boundary step between the main floor panel and the rear floor panel;
A floor lower member disposed long in the front-rear direction at a substantially center in the vehicle width direction below the main floor panel and the rear floor panel;
A rigid member that extends in the vehicle width direction in the vicinity of the boundary step portion, and has a curved portion that is disposed above the floor lower member and protrudes upward so as to avoid interference with the floor lower member. In the lower body structure of an automobile with a cross member,
Above the curved portion, it is disposed integrally with the floor cross member, extends substantially linearly in the vehicle width direction over at least the entire width of the fuel tank, and a cross section perpendicular to the axial direction is a closed cross section. An automobile lower body structure comprising a linear closed cross-section member. With a rear side frame that is a rigid member extending in the front-rear direction near both ends in the vehicle width direction,
2. The lower body structure of an automobile according to claim 1, wherein the fuel tank is disposed between the rear side frames over substantially the entire width thereof.   3. The lower body structure of an automobile according to claim 1, wherein the linear closed section member is a pipe member. The floor cross member includes a vertical wall that is erected substantially vertically and has an upper end joined to the rear floor panel.
A storage member that includes a substantially U-shaped cross-section in a side view and that is configured to store the linear closed cross-section member in the U-shaped cross-section is an open surface of the U-shaped cross-section. The lower body structure of an automobile according to any one of claims 1 to 3, wherein the lower body structure is joined to the vertical wall on the side. The floor cross member includes a horizontal wall disposed substantially horizontally and having a front end joined to the main floor panel,
A reinforcing member that is disposed integrally with the floor cross member in the vicinity of the curved portion and that is joined to the vertical wall and the horizontal wall to form a closed section surrounding the linear closed section member. The lower body structure of an automobile according to claim 4.   The linear closed cross-section member is provided integrally with the floor cross member near both ends in the vehicle width direction, and includes a box member having a wall surface extending in the front-rear direction and forming a closed cross section in front view. The lower body structure of an automobile according to any one of claims 1 to 5.

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