JP7779101B2 - Vehicle lower body structure - Google Patents

Description

The present invention relates to an automobile body structure, and more specifically to a body structure in which a reinforcing member is joined to a body component that forms a closed cross-sectional structure.

Closed cross-section structures have higher strength and rigidity than open cross-section structures, and are widely used in vehicle body components. Patent Document 1 discloses a vehicle body structure in which a reinforcing member is joined to a vehicle body component that forms a closed cross-section structure. In this vehicle body structure, to further increase the strength and rigidity of the closed cross-section structure, the reinforcing member is joined to the vehicle body component via a flange portion formed integrally with the reinforcing member. Specifically, the reinforcing member is joined to a hat-shaped cross-section member that forms the closed cross-section structure together with a flat plate-shaped member that extends in the vehicle width direction and opens upward.

The reinforcing member in Patent Document 1 has left and right side portions and a top portion connecting them, and has a total of eight flange portions extending from the front and rear edges of the top portion, the front and rear edges of both side portions, and the bottom edges of both side portions. A total of three flange portions extending from the top portion and the front edges of both side portions of the reinforcing member are joined to the front portion of the hat-shaped cross-section member, three flange portions extending from the top portion and the rear edges of both side portions of the reinforcing member are joined to the rear portion, and two flange portions extending from the bottom edges of both side portions of the reinforcing member are joined to the bottom portion.

JP 2014-162400 A

In the structure described in Patent Document 1, the reinforcing members are joined to three surfaces—the front, rear, and bottom surfaces—of the hat-shaped cross-section member, further increasing the strength and rigidity of the closed cross-section structure formed by the hat-shaped cross-section member and the flat plate-shaped member. When applied to a closed cross-section structure formed by a reinforcing member and a hat-shaped cross-section member, there are no problems because the reinforcing members can be welded to the three surfaces of the hat-shaped cross-section member before the closed cross-section structure is formed. However, problems arise when applied to other closed cross-section structures typically found in the rear of a passenger vehicle cabin. Specifically, the structure described includes a vehicle body structure having a cross-member lower extending in the vehicle width direction and vertically, a lower surface portion connected to the lower edge of the vertical wall portion and positioned forward, and an upper surface portion connected to the upper edge of the vertical wall portion and positioned rearward, the cross-member upper portion having a front surface located forward of the vertical wall portion of the cross-member lower and an upper surface portion connected to the upper edge of the front surface and positioned rearward, forming a closed cross-section structure together with the cross-member lower. If the structure of Patent Document 1 were to be applied to this vehicle body structure, it would be necessary to weld reinforcing members to two surfaces of the lower cross member, then weld the upper cross member to the lower cross member, and finally weld a reinforcing member to one surface of the upper cross member inside the closed cross section structure. This would require creating an opening in the lower cross member or upper cross member to pass a welding gun through for welding work on the closed cross section structure, which would be extremely disadvantageous in terms of strength and rigidity.

Therefore, issues remain when applying the reinforcing member of Patent Document 1 to a vehicle body structure in which the above-mentioned cross member lower and cross member upper form a closed cross-sectional structure.

In light of the above issues, the inventors of the present invention thoroughly investigated ways to increase the strength and rigidity of a vehicle body structure in which the above-mentioned cross-member lower and upper cross-members form a closed cross-section structure by placing a reinforcing member inside the closed cross-section structure while ensuring productivity. First, to increase productivity, they considered reducing the joint surface between the reinforcing member and the member that forms the closed cross-section structure. However, reducing the joint surface reduces the reinforcing effect of the reinforcing member. They then considered increasing the strength and rigidity of the reinforcing member itself. As a result, they arrived at the idea of compensating for the reduced reinforcing effect by giving the reinforcing member a top surface, front surface, and side surface that are continuous with each other, thereby increasing the strength and rigidity of the reinforcing member itself.

The present invention, which embodies this concept, is based on a vehicle body structure having a cross-member lower that includes vertical wall portions extending in the vehicle width direction and the vehicle up-down direction, a lower surface portion that is continuous with the lower edge of the vertical wall portion and located forward, and an upper surface portion that is continuous with the upper edge of the vertical wall portion and located rearward, the cross-member upper including a front portion that is located forward of the vertical wall portion of the cross-member lower, and an upper surface portion that is continuous with the upper edge of the front portion and located rearward, the cross-member upper forming a closed cross-sectional structure together with the cross-member lower. The present invention also includes a reinforcing member that is disposed within the closed cross-sectional structure formed by the cross-member lower and the cross-member upper. The reinforcing member integrally includes a front portion facing the front of the vehicle, an upper surface portion that is continuous with the upper edge of the front portion, a pair of side portions that are continuous with the side edges of the front portion, a pair of first flanges that are continuous with the rear edges of the pair of side portions, and a pair of second flanges that are continuous with the lower edges of the pair of side portions. The pair of first flanges are joined to the vertical wall portion of the cross member lower, and the pair of second flanges are joined to the lower surface portion of the cross member lower, and further, a damping member is filled in at least a portion of the gap between the upper surface portion of the cross member upper and the upper surface portion of the reinforcing member .

With this configuration, the first flanges formed integrally with the pair of side surfaces of the reinforcing member are joined to the vertical wall of the lower cross-member, and the second flanges formed integrally with the side surfaces are joined to the lower surface of the lower cross-member. This provides sufficient reinforcement for the closed cross-section structure of the reinforcing member. At the same time, it is possible to weld the lower cross-member and the reinforcing member together before welding the lower cross-member and the upper cross-member together, improving productivity.

In addition, by filling at least a portion of the gap between the upper surface of the cross member upper and the upper surface of the reinforcing member with a damping material , the joint between the vertical wall portion of the cross member lower and the flange portion at the lower surface, plus the upper surface of the cross member upper, is essentially joined on three sides, further enhancing the reinforcing effect of the closed cross-sectional structure of the reinforcing member.

In the present invention, the damping member may be made up of a plurality of members, each of which may be spaced apart from one another in the vehicle width direction and filled in the gap between the upper surface of the cross member upper and the upper surface of the reinforcing member.

With this configuration, the damping members are spaced apart and positioned in multiple locations on the upper surface, allowing the damping members to be used effectively to transmit loads, further enhancing the reinforcing effect of the reinforcing member on the closed cross-sectional structure.

In the present invention, the shape of the reinforcing member may be plane-symmetric with respect to a vertical plane extending in the up-down direction of the vehicle.

With this configuration, the symmetrical reinforcing members absorb loads input from all directions to the closed cross-section structure evenly, further enhancing the reinforcing effect on the closed cross-section structure.

Furthermore, the plane of symmetry of the reinforcing member may be located at the center in the vehicle width direction.

With this configuration, the reinforcing member located at the center of the vehicle width absorbs loads input to the closed cross-section structure from all directions evenly, further enhancing the reinforcing effect of the closed cross-section structure.

In the present invention, the lower surface of the cross member lower may have a raised portion that rises higher than other portions, and the second flange portion of the reinforcing member may be joined to the raised portion.

With this configuration, the cross-sectional area of the closed cross-section structure formed by the lower cross member and upper cross member is smallest, and the reinforcing member is attached to the protruding portion, where deformation is most likely to occur, allowing the reinforcing member to be used effectively.

As explained above, the vehicle body structure of the present invention allows for a reinforcing member that provides sufficient reinforcing effect for the closed cross-section structure to be welded to the cross-member lower, and then the cross-member lower and cross-member upper are welded together to complete the closed cross-section structure, thereby improving productivity.

1 is a plan view of a lower body of an automobile equipped with a vehicle body structure according to an embodiment of the present invention. FIG. 2 is an exploded perspective view showing the periphery of a third cross member of the lower vehicle body. FIG. 2 is a perspective view of the third cross member as seen obliquely from the front. FIG. 4 is a cross-sectional view taken along the line A-A in FIG. 3 . FIG. 4 is a cross-sectional view taken along the line B-B in FIG. 3 . FIG. 10 is a perspective view of the gusset as seen obliquely from the front. FIG. 7 is a cross-sectional view taken along the line CC in FIG. 6 .

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the accompanying drawings, Fr and Rr respectively indicate the front (or forward) and rear (or rearward) sides of the vehicle, and OUT and IN respectively indicate the outside (or outward) and inside (or inward) sides of the vehicle width.

Figure 1 shows an automobile lower body 1 equipped with a vehicle body structure according to an embodiment of the present invention. The lower body 1 includes a pair of left and right side sills 2 extending in the longitudinal direction of the vehicle, a tunnel panel 3 positioned in the center of the vehicle width between the pair of left and right side sills 2 and extending in the longitudinal direction of the vehicle, and a right floor panel 41 and a left floor panel 42 extending inward in the vehicle width direction from the inner ends of the pair of left and right side sills 2 to the tunnel panel 3.

A pair of left and right floor frames 5 are arranged as reinforcing members on the lower body 1, extending in the longitudinal direction of the vehicle between a pair of left and right side sills 2 and a tunnel panel 3. A first cross member 6 and a second cross member 7 are arranged in this order toward the rear of the vehicle, spanning the width of the vehicle between the pair of left and right side sills 2 and the tunnel panel 3.

Furthermore, a diagonal frame 8 is disposed forward of the first cross member 6, extending diagonally rearward from the pair of left and right side sills 2 to the pair of left and right floor frames 5. Furthermore, a third cross member 9 is disposed rearward of the second cross member 7, spanning between the pair of left and right side sills 2.

On the other hand, the front portion of the lower body 1 is equipped with a dash panel 10a, a dash panel cowl 10b, a pair of left and right front side frames 11, a bumper reinforcement 12, a front cross member 13, an apron member 14, a suspension housing 15, etc. Furthermore, the rear portion of the lower body 1 is equipped with a pair of left and right rear side frames 16 extending rearward from the rear ends of the pair of left and right side sills 2, a rear floor panel 17 extending in the vehicle width direction between the pair of left and right rear side frames 16, and a rear cross member 18.

The left and right floor panels 41, 42 extend in the fore-and-aft direction of the vehicle from the dash panel 10a to the third cross member 9 in Figure 1.

As shown in Figure 2, the third cross member 9, which has a closed cross-section structure, is formed by joining a lower cross member 91, which is the lower rear member, and an upper cross member 92, which is the upper front member.

The cross member lower 91 has a symmetrical shape in the vehicle width direction and includes a vertical wall portion 911 extending in the vehicle vertical direction, a lower surface portion 912 protruding forward from the lower edge of the vertical wall portion 911, and an upper surface portion 913 protruding rearward from the upper edge of the vertical wall portion 911. The lower surface portion 912 is spot welded to the rear ends of the floor panel 4 and the tunnel panel 3. The upper surface portion 913 is spot welded to the front end of the rear floor panel 17. The central portion of the lower surface portion 912 is higher in the vehicle vertical direction toward the center to match the changing height of the tunnel panel 3, and the vertical length of the vertical wall portion 911 also decreases toward the center. The lower surface portion 912 is highest at the center in the vehicle width direction.

As shown in Figure 4, which is a cross-sectional view taken along line A-A in Figure 3, the cross member upper 92 has a symmetrical shape in the vehicle width direction and has a front surface portion 921 extending in the vertical direction of the vehicle, a lower surface portion 922 protruding forward from the lower edge of the front surface portion 921, and an upper surface portion 923 protruding rearward from the upper edge of the front surface portion 921. The lower surface portion 922 is spot welded to the rear ends of the floor panel 4 and the tunnel panel 3. The upper surface portion 923 is spot welded to the front end of the rear floor panel 17.

The lower cross member 91 and upper cross member 92 are welded together at the lower surface 912 of the lower cross member to the lower surface 922 of the upper cross member, and at the upper surface 913 of the lower cross member to the upper surface 923 of the upper cross member, respectively, to form a closed cross-section structure.

As shown in Figure 2, a gusset 19 is disposed within the closed cross-section structure formed by the cross member lower 91 and cross member upper 92 as a reinforcing member for the third cross member 9. The gusset extends in the vertical and longitudinal directions of the vehicle and has a symmetrical shape with a vertical plane located in the center of the vehicle width as the plane of symmetry.

As shown in Figure 6, the gusset 19 consists of a front portion 191 facing the front of the vehicle, an upper portion 192 that is continuous with the upper end of the front portion 191, a right side portion 193 that is continuous with the right end of the front portion 191, and a left side portion 194 that is continuous with the left end.

The front surface portion 191 consists of a central front surface portion 191a with a downwardly opening notch, a right front surface portion 191b that continues from the sloped portion at the right end of the central front surface portion 191a and protrudes further forward than the central front surface portion 191a, and a left front surface portion 191c that continues from the sloped portion at the left end of the central front surface portion 191a and protrudes further forward than the central front surface portion 191a.

The top surface 192 consists of a central top surface 192a with an upwardly opening notch, a right upper surface 192b that continues from the sloped portion at the right end of the central top surface 192a and protrudes higher than the central top surface 192a, and a left upper surface 192c that continues from the sloped portion at the left end of the central top surface 192a and protrudes higher than the central top surface 192a.

As shown in FIG. 7, the right side surface portion 193 has a first flange portion 193a that continues to the rear edge and a second flange portion 193b that continues to the bottom edge. Similar to the right side surface portion 193, the left side surface portion 194 has a first flange portion 194a that continues to the rear edge and a second flange portion 194b that continues to the bottom edge. The first flange portions 193a, 194a are joined to the vertical wall portion 911 of the cross member lower 91, and the second flange portions 193b, 194b are joined to the lower surface portion 912 of the cross member lower 91.

A circular damping member 20 is adhered to the gap between the upper surface portion 192 of the gusset 19 and the upper surface portion 923 of the cross member upper 92. A first member 20a is adhered to the upper right surface portion 192b , and a second member 20b is adhered to the upper left surface portion 192c .

The damping member 20 is a viscoelastic material with a storage modulus of 500 MPa or less and a loss factor of 0.2 or more under conditions where the temperature is 20°C and the frequency of the excitation force is 30 Hz. The damping member 20 itself has adhesive properties, and is also called a damping bond because of its relatively high viscosity before drying. The upper surface 192 of the gusset and the upper surface 923 of the cross member upper 92 are joined to each other solely by the adhesive force of the damping member 20.

We will now explain the process of disposing the gusset 19 and damping member 20 inside the third cross member 9 using the cross member lower 91, cross member upper 92, gusset 19, and damping member 20 shown in Figure 2. First, the cross member lower 91 and gusset 19 are welded together. Specifically, the first flange portions 193a and 194a of the gusset 19 are welded to the vertical wall portion 911 of the cross member lower 91, and the second flange portions 193b and 194b are welded to the lower surface portion 912 of the cross member lower 91. Next, the damping member 20 is applied to the upper surface portion 192 of the gusset 19. When applying the damping member 20, it is necessary to apply it thicker than the gap between the upper surface portion 192 of the gusset 19 and the upper surface portion 923 of the cross member upper 92. For example, if the gap is 0.5 to 3.5 mm, it is preferable to apply the damping member 20 to a thickness of 6.0 to 8.0 mm. The damping member 20 evaporates and solidifies when exposed to air, so after application, the lower surface 912 of the cross member lower is welded to the lower surface 922 of the cross member upper, and the upper surface 913 of the cross member lower is welded to the upper surface 923 of the cross member upper. In this way, the gusset 19 is welded to the cross member lower 91 inside the third cross member 9, and is bonded to the cross member upper 92 via the damping member 20.

As described above, the gusset 19 and the cross member lower 91 are first welded together to form a box-shaped reinforcement structure. Next, the cross member lower 91 and the cross member upper 92 are welded together to form a closed cross-section structure. This increases the rigidity of the third cross member 9 without creating openings in the cross member lower 91 or cross member upper 92 for passing a welding gun through.

Furthermore, when the cross member lower 91 and the cross member upper 92 are welded together, the damping member 20 is filled into the gap between the cross member upper 92 and the upper surface 192 of the gusset 19. This further increases the rigidity of the third cross member 9.

DESCRIPTION OF SYMBOLS 1... Lower body 2... Side sill 3... Tunnel panel 4... Floor panel 41... Right floor panel 42... Left floor panel 5... Floor frame 6... First cross member 7... Second cross member 8... Diagonal frame 9... Third cross member 91... Lower cross member 911... Vertical wall portion 912... Lower surface portion 913... Upper surface portion 92... Upper cross member 921... Front portion 922... Lower surface portion 923... Upper surface portion 10a... Dash panel 10b... Dash panel cowl 11... Front side frame 12... Bumper reinforcement 13... Front cross member 14... Apron member 15... Suspension housing 16... Rear side frame 17... Rear floor panel 18... Rear cross member 19... Gusset (reinforcement member)
191...Front portion 191a...Central front portion, 191b...Right front portion, 191c...Left front portion 192...Top portion 192a...Central upper surface portion, 192b...Right upper surface portion, 192c...Left upper surface portion 193...Right side portion 193a...First flange portion 193b...Second flange portion 194...Left side portion 194a...First flange portion 194b...Second flange portion 20...Dampening member 20a...First member, 20b...Second member

Claims (5)

a cross member lower extending in the vehicle width direction, the cross member lower including: a vertical wall portion extending in the vehicle width direction and the vehicle up-down direction; a lower surface portion contiguous with a lower edge of the vertical wall portion and positioned forward; and an upper surface portion contiguous with an upper edge of the vertical wall portion and positioned rearward;
a cross member upper including a front surface portion located forward of the vertical wall portion of the cross member lower and an upper surface portion located rearward and continuous with an upper edge of the front surface portion, the cross member upper forming a closed cross section structure together with the cross member lower ;
A vehicle body structure having a reinforcing member disposed inside a closed cross-sectional structure formed by the cross member lower and the cross member upper,
the reinforcing member integrally comprises a front portion facing the front of the vehicle, an upper surface portion continuous with the upper edge of the front portion, a pair of side surfaces continuous with the side edges of the front portion, a pair of first flanges continuous with the rear edges of the pair of side surfaces, and a pair of second flanges continuous with the lower edges of the pair of side surfaces, the pair of first flanges being joined to the vertical wall portions of the cross member lower, and the pair of second flanges being joined to the lower surface portions of the cross member lower,
A vehicle body structure, characterized in that at least a part of a gap between the upper surface portion of the cross member upper and the upper surface portion of the reinforcing member is filled with a damping member . 2. The vehicle body structure according to claim 1 , wherein the damping member is filled in the gap at a plurality of locations spaced apart from one another in the vehicle width direction . 3. The vehicle body structure according to claim 1 , wherein the shape of the reinforcing member is plane-symmetrical with respect to a vertical plane extending in the up-down direction of the vehicle . 4. The vehicle body structure according to claim 3 , wherein the plane of symmetry of the reinforcing member is positioned at the center in the vehicle width direction . A vehicle body structure as described in any one of claims 1 to 4 , characterized in that the lower surface portion of the cross member lower has a raised portion that rises higher than other portions, and the second flange portion of the reinforcing member is joined to the raised portion .