JP5525563B2 - Lower body structure of automobile - Google Patents

Description

  According to the present invention, a floor tunnel extending in the front-rear direction from the center in the vehicle width direction of the floor panel is raised upward, and fastening portions at both ends of the tunnel bar extending in the vehicle width direction and straddling the opening of the floor tunnel are connected to the left and right fronts. The present invention relates to a lower body structure of an automobile that is fastened with a bolt to a rear portion of a side frame.

  Patent Document 1 below describes a brace that extends in the vehicle width direction of an automobile and that is formed by bending and crushing a steel pipe with braces fastened to the lower surfaces of left and right rockers (side sills) and left and right suspension brackets. It is known.

JP 2008-279951 A

  However, in the above conventional one, since the fastening part of the brace fastened to the rocker or the suspension bracket is formed by crushing the iron pipe, the secondary moment of section of the fastening part has a circular cross section in the middle part in the vehicle width direction. There is a possibility that the effect as a reinforcing member cannot be sufficiently obtained because the moment of inertia is greatly reduced as compared with the partial moment of the section. In order to prevent this, if the diameter or thickness of the iron pipe is increased, there is a problem that the strength of the intermediate portion becomes excessive and the weight increases. Moreover, in order to crush an iron pipe into an elliptical cross section, there exists a problem which processing cost increases. And since the head of the bolt which fastens a brace protrudes below in the above-mentioned conventional thing, a road surface obstacle may collide with the head of a bolt, and a fastening part may break.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to achieve both the strength and weight reduction of a tunnel bar that connects left and right front side frames in the vehicle width direction.

In order to achieve the above object, according to the first aspect of the present invention, a floor tunnel extending in the front-rear direction from the vehicle width direction center of the floor panel is raised upward, and extends in the vehicle width direction to extend the floor tunnel. A vehicle body lower structure in which fastening portions at both ends of the tunnel bar straddling the opening of the vehicle are fastened with bolts to the rear portions of the left and right front side frames, and the tunnel bar includes at least an upper wall, a lower wall, a front wall, and a rear wall An aluminum extrusion material having a constant closed cross section, wherein, in the fastening portion, the lower wall has a first bolt hole having a diameter larger than a diameter of a head portion of the bolt, and the upper wall is formed of the bolt. a second bolt hole larger than the diameter of the shaft portion of smaller the bolt than the diameter of the head portion, the bolt is housed inside the tunnel bar engaged state, the flow A bead extending in the front-rear direction and recessed upward is formed on the rear lower surface of the toeside frame, and the tunnel bar is fastened to the front side frame by the bolt at two locations on both sides of the bead in the vehicle width direction. A vehicle body lower part structure for an automobile is proposed in which a connecting portion constructed in an opening of an under cover that covers a lower surface of a floor panel is accommodated in the bead .

  According to the invention described in claim 2, in addition to the configuration of claim 1, the cross section of the tunnel bar is a closed curve that is flat in the vertical direction, and the thickness of the front wall and the rear wall is There is proposed a lower body structure of an automobile characterized by being thinner than the wall thickness of the upper wall and the lower wall.

  According to a third aspect of the present invention, in addition to the configuration of the first or second aspect, the lower wall is inclined so that the rear portion is higher than the front portion. A lower body structure is proposed.

According to the invention described in claim 4, in addition to the configuration of any one of claims 1 to 3, an exhaust pipe disposed inside the floor tunnel is provided, and the tunnel bar includes the tunnel bar underbody structure for an automobile, characterized in that it comprises a weak portion at a position corresponding to the lower portion of the exhaust pipe Ru been proposed.

According to a fifth aspect of the present invention, in addition to the structure of any one of the first to fourth aspects , the upper wall is in contact with the lower surface of the under cover. A lower body structure is proposed.

  According to the configuration of the first aspect, since the fastening portions at both ends of the tunnel bar extending in the vehicle width direction and straddling the opening of the floor tunnel of the floor panel are fastened with bolts to the rear portions of the left and right front side frames, Therefore, it is possible to suppress the deformation of the floor tunnel opening so as to open to the left and right, and to increase the strength of the floor panel. In particular, the tunnel bar is an aluminum extruded material with a certain closed cross-section consisting of at least the upper wall, lower wall, front wall, and rear wall. Therefore, the degree of freedom of the cross-sectional shape is higher than that of a tunnel bar in which pipe material is crushed. Therefore, not only can the height of the floor panel of the automobile be kept low, but it can also contribute to weight reduction and manufacturing cost reduction. In the tunnel bar fastening portion, the lower wall has a first bolt hole whose diameter is larger than the diameter of the bolt head, and the upper wall is smaller than the bolt head diameter and larger than the bolt shaft diameter. Since it has the 2nd hole, it becomes possible to store a bolt in a fastening state inside a tunnel bar, and it can prevent that a road surface obstacle collides with a bolt and a fastening part fractures.

In addition, a bead extending in the front-rear direction and recessed upward is formed on the rear lower surface of the front side frame, and the tunnel bar is fastened to the front side frame by bolts at two locations on both sides of the bead in the vehicle width direction. At this time, since the connecting portion installed in the opening of the under cover that covers the lower surface of the floor panel is stored in the bead, the position of the under cover can be displaced by regulating the position by sandwiching the connecting portion between the bead and the tunnel bar. Can be prevented.

  According to the construction of claim 2, the cross section of the tunnel bar is a closed curve that is flat in the vertical direction, and the wall thickness of the front wall and the rear wall is thinner than the wall thickness of the upper wall and the lower wall. The height can be kept to a minimum to avoid contact with road surface obstacles. Even if contacted with road surface obstacles, the tunnel bar deforms so that it collapses in the vertical direction and loads from road surface obstacles Therefore, the fastening portion can be prevented from breaking.

  According to the third aspect of the present invention, the lower wall of the tunnel bar is inclined so that the rear part is higher than the front part, so that the airflow from the front is prevented from being disturbed by the tunnel bar when the automobile is running. It is possible to reduce air resistance and prevent air noise.

According to the fourth aspect of the present invention, since the tunnel bar includes the fragile portion at a position corresponding to the lower portion of the exhaust pipe disposed inside the floor tunnel, the tunnel bar is broken at the fragile portion at the time of a frontal collision of the automobile. by enabling downward movement of the exhaust pipe, preventing deformation of the securing and the floor panel of the shock absorbing stroke can be ing.

According to the fifth aspect of the present invention, since the upper wall of the tunnel bar comes into contact with the lower surface of the under cover, the under cover can be supported from below by the tunnel bar so that it does not hang down due to its own weight.

The figure which looked at the front part of the body of a car from the slanting lower part. FIG. 2 is a two-direction arrow view of FIG. 1. FIG. 3 is an enlarged view of part 3 of FIG. 2. FIG. 4 is a sectional view taken along line 4-4 of FIG. FIG. 5 is a sectional view taken along line 5-5 of FIG. FIG. 6 is a sectional view taken along line 6-6 of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. Note that the front-rear direction, the left-right direction (vehicle width direction), and the up-down direction in this specification are based on the driver seated in the driver's seat.

  As shown in FIG. 1, a vehicle body frame includes a pair of left and right front side frames 11, 11 that extend in the engine room in the front-rear direction to support the engine and the transmission, and in the front-rear direction along both sides of the vehicle compartment. A pair of left and right side sills 12, 12 that extend and a pair of left and right floor frames 13, 13 that are disposed on the inner side in the vehicle width direction of the side sills 12, 12 are provided. The front side frame rear ends 14 and 14 are connected to the front ends of the floor frames 13 and 13, and the front side frame rear ends 14 and 14 are connected to the front ends of the side sills 12 and 12 via a pair of left and right outriggers 15 and 15.

  A floor tunnel 17 having a reverse U-shaped cross section extending in the front-rear direction protrudes upward at the center in the vehicle width direction of the floor panel 16 connecting the left and right side sills 12, 12, and an exhaust pipe extending rearward from the engine 18 is housed inside the floor tunnel 17. The lower surface of the floor panel 16 is covered with an under cover 19 made of synthetic resin, and a pair of left and right openings 19a and 19a are formed in a portion where the under cover 19 covers the rear end portions of the front side frame rear ends 14 and 14. Fastening portions 21 and 21 at both left and right ends of the tunnel bar 20 extending in the vehicle width direction are fastened to the lower surfaces of the rear end portions of the front side frame rear ends 14 and 14 exposed from the openings 19a and 19a of the under cover 19.

  Next, based on FIGS. 2-6, the structure of the tunnel bar 20 and the structure of the fastening parts 21 and 21 which fasten it to the front side frame rear end 14 and 14 are demonstrated.

  The tunnel bar 20 is a member having a certain closed cross section in the longitudinal direction and made of an aluminum alloy drawing material, and is formed between a flat upper wall 20a, a flat lower wall 20b, and front ends of the upper wall 20a and the lower wall 20b. And a rear wall 20d that connects the rear ends of the upper wall 20a and the lower wall 20b in an arc shape, and is formed flat in the vertical direction as a whole (see FIG. 5). . The wall thickness of the front wall 20c and the rear wall 20d is smaller than the wall thickness of the upper wall 20a and the lower wall 20b, and the upper wall 20a is arranged in the horizontal direction so that the front part and the rear part have the same height. On the other hand, the lower wall 20b is inclined by an angle θ so that the rear part is higher than the front part (see FIG. 5).

  Fastening portions 21, 21 at both ends of the tunnel bar 20 are fastened to weld nuts 23, 23 fixed in advance to the front side frame rear end 14 with two bolts 22, 22, respectively. Each fastening portion 21 includes a first bolt hole 20e formed in the lower wall 20b and a second bolt hole 20f formed in the upper wall 20a (see FIG. 5). Each bolt 22 includes a large-diameter head portion 22a and a shaft portion 22b having a smaller diameter than the head portion, and the diameter of the first bolt hole 20e in the lower wall 20b is larger than the diameter of the head portion 22a of the bolt 22. The diameter of the second bolt hole 20f in the upper wall 20a is smaller than the diameter of the head portion 22a of the bolt 22 and larger than the diameter of the shaft portion 22b.

  Accordingly, the shaft portion 22b of the bolt 22 passes through the first bolt hole 20e of the lower wall 22d and the second bolt hole 20f of the upper wall 20a and is screwed into the weld nut 23, and the head portion 22a of the bolt 22 is lowered to the lower wall 22d. The fastening portion 21 of the tunnel bar 20 is fastened to the lower surface of the front side frame rear end 14 by passing through the first bolt hole 20e and seating around the second bolt hole 20f of the upper wall 20a. In this fastened state, the head 22a of the bolt 22 is housed inside the tunnel bar 20, and the lower end of the head 22a does not protrude below the lower surface of the lower wall 22b of the tunnel bar 20 (see FIG. 5). .

  Further, a bead 14a extending in the front-rear direction is recessed upward in the front side frame rear end 14 (see FIGS. 3 and 4), and the two bolts 22 and 22 sandwich both sides of the bead 14a in the vehicle width direction. Be placed. Between the two bolts 22 and 22, a space α is formed between the upper surface of the upper wall 20a of the tunnel bar 20 and the lower surface of the bead 14a (see FIG. 4), and the center of the opening 19a of the under cover 19 is formed. A connecting portion 19b erected in the front-rear direction is disposed in the space α. The lower surface of the under cover 19 is supported on the upper surface of the upper wall 20a of the tunnel bar 20.

  The exhaust pipe 18 housed in the front-rear direction inside the floor tunnel 17 intersects the upper part of the tunnel bar 20 extending in the vehicle width direction, and the weakened part 20g formed by an opening in the tunnel bar 20 corresponding to the lower part of the exhaust pipe 18. Is formed (see FIGS. 2 and 6).

  Next, the operation of the embodiment of the present invention having the above configuration will be described.

  In order to fix the tunnel bar 20 to the vehicle body, the tunnel bar 20 is overlapped on the lower surface of the under cover 19 attached in advance to the lower surface of the vehicle body, and the left and right fastening portions 21 and 21 of the tunnel bar 20 are respectively connected to two bolts 22 and 22. Then, it may be fastened to the lower surface of the front side frame rear end 14,14. As a result, the front side frame rear ends 14, 14 at the rear of the left and right front side frames 11, 11 are connected by the tunnel bar 20 so as to straddle the floor tunnel 17 formed in the floor panel 16. It is possible to increase the strength of the floor panel 16 by suppressing the deformation of the floor panel 16 so as to open to the left and right.

  Since the tunnel bar 20 is an aluminum extruded material having a certain closed cross section composed of an upper wall 20a, a lower wall 20b, a front wall 20c, and a rear wall 20d, the degree of freedom of the cross-sectional shape as compared with a tunnel bar obtained by crushing a pipe material. The height of the vehicle floor panel 16 can be kept low, and the weight can be reduced and the manufacturing cost can be reduced. In the fastening portion 21 of the tunnel bar 20, the lower wall 20b has first bolt holes 20e and 20e having a diameter larger than the diameters of the heads 22a and 22a of the bolts 22 and 22, and the upper wall 20a has the bolts 22 and 22 as well. Since the second bolt holes 20f and 20f are smaller than the diameters of the head portions 22a and 22a of the bolts 22 and 22 and larger than the diameters of the shaft portions 22b and 22b of the bolts 22 and 22a, It is possible to prevent the fastening portion 21 from breaking due to a road surface obstacle colliding with the bolts 22 and 22.

  Further, the cross section of the tunnel bar 20 is a closed curve which is flat in the vertical direction, and the thickness of the front wall 20c and the rear wall 20d is thinner than the thickness of the upper wall 20a and the lower wall 20b. The contact with the road surface obstacle can be avoided by minimizing it, and even if it comes into contact with the road surface obstacle, the tunnel bar 20 is deformed so as to be crushed in the vertical direction to release the load from the road surface obstacle. Therefore, the fastening part 21 can be prevented from breaking. Moreover, since the lower wall 20b of the tunnel bar 20 is inclined so that the rear part is higher than the front part, the thickness of the rear part of the tunnel bar 20 becomes thinner than the thickness of the front part. Is minimized by the tunnel bar 20, and it is possible to reduce air resistance and prevent air noise. Furthermore, since the tunnel bar 20 includes the weakened portion 20g at a position corresponding to the lower side of the exhaust pipe 18 disposed inside the floor tunnel 17, the tunnel bar 20 is broken at the weakened portion 20g at the time of a frontal collision of the automobile, so that the exhaust pipe By enabling the downward movement of 18, it is possible to secure a shock absorbing stroke and prevent deformation of the floor panel 16.

  Further, a bead 14a extending in the front-rear direction and recessed upward is formed on the lower surface of the front side frame rear end 14, and the tunnel bar 20 is fastened by bolts 22 and 22 at two locations on both sides in the vehicle width direction of the bead 14a. A connecting portion 19b installed in the opening 19a of the under cover 19 covering the lower surface of 16 is accommodated in the bead 14a. Thereby, the position shift of the under cover 19 can be prevented by restricting the position by sandwiching the connecting portion 19b of the under cover 19 with the bead 14a and the tunnel bar 20. Moreover, since the upper wall 20a of the tunnel bar 20 contacts the lower surface of the under cover 19, the under cover 19 can be supported from below by the tunnel bar 20 so that it does not hang down due to its own weight.

  The embodiments of the present invention have been described above, but various design changes can be made without departing from the scope of the present invention.

  For example, the fragile portion 20g of the tunnel bar 20 is not limited to the opening of the embodiment, and may be a notch or a thin portion.

11 Front side frame 14a Bead 16 Floor panel 17 Floor tunnel 18 Exhaust pipe 19 Under cover 19b Opening 19b Connecting part 20 Tunnel bar 20a Upper wall 20b Lower wall 20c Front wall 20d Rear wall 20e First bolt hole 20f Second bolt hole 20g Vulnerable Part 21 Fastening part 22 Bolt 22a Head part 22b Shaft part

Claims (5)

The floor tunnel (17) extending in the front-rear direction from the vehicle width direction center of the floor panel (16) is raised upward, and the tunnel bar (20) extends in the vehicle width direction and straddles the opening of the floor tunnel (17). A vehicle body lower structure in which fastening portions (21) at both ends are fastened to rear portions of left and right front side frames (11) with bolts (22),
The tunnel bar (20) is an aluminum extruded member having a certain closed cross section composed of at least an upper wall (20a), a lower wall (20b), a front wall (20c) and a rear wall (20d), and the fastening portion (21 ), The lower wall (20b) has a first bolt hole (20e) having a diameter larger than the diameter of the head (22a) of the bolt (22), and the upper wall (20a) has the bolt (22). ) Having a second bolt hole (20f) that is smaller than the diameter of the head portion (22a) of the bolt (22) and larger than the diameter of the shaft portion (22b) of the bolt (22). housed inside the bar (20), wherein the rear lower surface of the front side frame (11), with a bead (14a) that is recessed upward and extends in the front-rear direction is formed in the vehicle width direction of the bead (14a) The tunnel bar (20) is fastened to the front side frame (11) by the bolts (22) at two locations on the side, inside the opening (19a) of the under cover (19) covering the lower surface of the floor panel (16) A vehicle body lower part structure for an automobile, characterized in that a connecting part (19b) erected on the vehicle is housed in the bead (14a) .   The cross section of the tunnel bar (20) is a closed curve that is flat in the vertical direction, and the thickness of the front wall (20c) and the rear wall (20d) is the same as that of the upper wall (20a) and the lower wall (20b). The vehicle body lower part structure according to claim 1, wherein the lower body structure is thinner than a wall thickness.   The vehicle body lower part structure according to claim 1 or 2, wherein the lower wall (20b) is inclined so that a rear part is higher than a front part. An exhaust pipe (18) disposed inside the floor tunnel (17) is provided, and the tunnel bar (20) includes a weakened portion (20g) at a position corresponding to the lower side of the exhaust pipe (18). that, underbody structure of an automobile according to any one of claims 1 to 3. The vehicle body lower part structure according to any one of claims 1 to 4, wherein the upper wall (20a) is in contact with a lower surface of the under cover (19).

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