Vehicle undercarriage

Abstract

The present invention is a bottom structure of a vehicle in which a rear section of a leaf spring 11 is linked via a shackle to a position further back on the vehicle than a connection section connecting a cross member 10 to the rearmost section of a side member 5. The bottom structure comprises: a tubular part 40 which passes through and is affixed to a side surface of the side member 5 in the vehicle width direction and into which a shackle pin is inserted; and a reinforcing part 45 provided so as to surround the tubular part 40 at the vehicle width direction inner side end of the tubular part 40. The reinforcing part 45 includes a first portion 45a which extends in the vehicle forward direction towards the cross member 10, and a second portion 45b which is provided contiguous with the first portion 45a, extends in the vehicle rear direction, and has a hole into which the vehicle width direction inner side end of the tubular part 40 is inserted.

Description

[Technical Field]

[0001] The present invention relates to a support structure for a suspension device of a vehicle. [Background technology]

[0002] Vehicles such as pickup trucks are equipped with a pair of side members spaced apart in the vehicle width direction as strength members, which are further connected by multiple cross members extending in the vehicle width direction to form a chassis frame. Furthermore, many vehicles with relatively heavy loads, such as pickup trucks, use leaf springs as suspension devices. The front and rear ends of the leaf springs are pivotally attached to side members. For example, in Patent Document 1, the rear end of the leaf spring is supported on the side member via a shackle. A cylindrical pin is inserted into a circular hole provided in the side member so as to extend in the vehicle width direction, and the pin connects the side member and the shackle so as to be pivotable in the vertical direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-306019 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to ensure strength and rigidity while reducing weight, side members are often made of steel plates with a rectangular box-like or U-shaped cross section. In order to further reduce the weight of vehicles, there is a demand for reducing the weight of side members by, for example, reducing the plate thickness as much as possible.

[0005] However, since a large load is input from the leaf spring to the connection portion of the side member with the shackle, it is necessary to ensure sufficient rigidity of the side member, particularly in the vicinity of this connection portion, in order to improve the vehicle's handling stability and ride comfort.

[0006] The present invention has been made to solve such problems, and aims to provide a vehicle understructure that improves the rigidity of the leaf spring support portion in a vehicle that has a chassis frame formed by connecting a pair of left and right side members with a cross member and in which leaf springs are supported on the side members. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the vehicle understructure of the present invention comprises a pair of side members arranged at intervals in the vehicle width direction and extending in the vehicle's fore-and-aft direction, a cross member extending in the vehicle width direction and connecting the pair of side members, leaf springs arranged respectively along the pair of side members and supporting the axles of the vehicle, and a connecting shaft rotatably connecting one end of the leaf spring to the side member, wherein the side member and the connecting shaft are connected at a position spaced apart in the vehicle's fore-and-aft direction from the connection portion between the side member and the cross member, and the vehicle understructure comprises: a tubular portion that is fixed so as to penetrate through the vehicle width direction side of the side member, and into which the connecting shaft is rotatably inserted, and a reinforcing portion provided on the side of the side member so as to surround the tubular portion at least on one end side of the tubular portion, and the reinforcing portion has a first portion extending in a first direction toward the cross member, and a second portion that is provided continuous with the first portion and extends in a second direction opposite to the first direction.

[0008] As a result, the connecting portion between the side member and the connecting shaft, i.e., the support portion of the leaf spring, is structured so that a load is input from the leaf spring to the side member via the connecting shaft and the tubular portion, but the reinforcement portion is provided on the side surface of the side member so as to surround the tubular portion at one end side, thereby increasing the rigidity of the support portion of the leaf spring. In particular, the reinforcement portion has a first portion extending toward the cross member and a second portion provided contiguous with the first portion and extending in the opposite direction from the first portion, which increases the rigidity of the side member near one end of the tubular portion and between the tubular portion and the cross member, thereby effectively increasing the rigidity of the side member against the load received from the leaf spring.

[0009] Preferably, the reinforcing portion holds the one end of the cylindrical portion. This allows the reinforcing portion to hold the tubular portion against the side member without rattle.

[0010] Preferably, the reinforcing portion is provided at an inner end in the vehicle width direction of both end portions of the tubular portion. As a result, a reinforcing portion is provided on the side member at the end on the inner side in the vehicle width direction, closer to the cross member, of both ends of the tubular portion, thereby more effectively increasing the rigidity of the side member near the support portion of the leaf spring.

[0011] Preferably, the second portion has a substantially annular shape surrounding the cylindrical portion. This makes it possible to reduce the space occupied by the second portion while increasing the rigidity of the side member near the support portion of the leaf spring.

[0012] Preferably, the first portion is arranged to extend linearly toward the cross member in the extension direction of the side member. This reduces the length of the first portion of the reinforcing portion, thereby reducing the vehicle weight, while bringing the first portion closer to the cross member, thereby increasing the rigidity of the leaf spring near the support portion.

[0013] Preferably, the first portion and the second portion have a width in a direction perpendicular to the extending direction of the side member that is larger than that of the cylindrical portion. This makes it possible to greatly increase the rigidity of the side member in the vicinity of the cylindrical portion by the first and second portions of the reinforcing portion.

[0014] Preferably, the side members are formed of a member having a thinner plate thickness at a portion closer to the tubular portion than a portion opposite to the tubular portion in the extension direction relative to a connection position with the cross member. This allows the thickness of the side member at the cylindrical portion side to be reduced, thereby reducing its weight. The cylindrical portion side of the side member is provided with a reinforcing portion, so rigidity is ensured even when this portion is made thin.

[0015] Preferably, the cross member is arranged at the rearmost of the vehicle's multiple cross members connecting the pair of side members, and the tubular portion is arranged behind the cross member in the vehicle. This allows the reinforcing portion to extend forward from the tubular portion toward the rearmost cross member. This improves the rigidity of the side member near the tubular portion located at the rear of the vehicle, thereby improving the rigidity against loads acting on the side member from the support portion of the leaf spring located at the rear of the vehicle. Furthermore, if the portion of the side member closer to the tubular portion than the connection position with the cross member is formed from a thinner material than the portion opposite the tubular portion, the thickness of the portion rearward of the rearmost cross member can be reduced, thereby significantly reducing the weight of the side member.

[0016] Preferably, the side member is a hollow member having a reinforcement extending in the vehicle width direction inside and connecting the inner walls of both sides in the vehicle width direction, and the reinforcement is positioned at a position in the front and rear of the vehicle between the reinforcing portion and the cross member. This allows the reinforcement to increase the rigidity of the side member near the connection portion with the cross member and the support portion of the leaf spring.

[0017] Preferably, the vehicle includes a mount bracket for fixing a luggage box to the side member, and the mount bracket is disposed at a front-rear position of the vehicle between the reinforcing portion and the cross member. This allows the load received by the support portion of the leaf spring to be transmitted to the cargo box via the mount bracket, thereby further increasing the rigidity of the support portion of the leaf spring by utilizing the cargo box. [Effects of the Invention]

[0018] According to the vehicle undercarriage structure of the present invention, the stiffness of the support portion of the leaf spring can be increased by the reinforcing portion provided on the side surface of the side member, thereby improving the handling stability and ride comfort of the vehicle. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a perspective view showing a schematic structure of a rear lower part of a vehicle according to an embodiment of the present invention; [Figure 2] 1 is a perspective view showing a schematic structure of a chassis frame of a vehicle according to an embodiment of the present invention; [Figure 3] FIG. 2 is a perspective view showing the structure of a mounting portion for a cargo box at the rear portion of the side member according to the embodiment. [Figure 4] 1 is a perspective view showing a lower structure near a rear support portion of a left leaf spring and near a connection portion between a left side member and a rearmost cross member according to the present embodiment. FIG. [Figure 5] 1 is a top view showing the lower structure near the rear support portion of the left leaf spring and near the connection portion between the left side member and the rearmost cross member according to this embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view showing a schematic structure of the lower rear part of a vehicle 1 according to an embodiment of the present invention. Fig. 2 is a perspective view showing a schematic structure of a chassis frame 2 of the vehicle 1 according to this embodiment. Fig. 3 is a perspective view showing a structure of a mounting portion for a luggage box 4 at the rear of a side member according to this embodiment.

[0021] A vehicle 1 employing the undercarriage of the present invention is a vehicle equipped with a suspension device 8 using leaf springs 11, such as a pickup truck.

[0022] 1 and 2, a vehicle 1 is provided with a pair of side members 5, 6 that extend in the vehicle longitudinal direction and are spaced apart in the vehicle width direction. The pair of side members 5, 6 are connected by a plurality of cross members to form a chassis frame 2. The cross members extend in the vehicle width direction and are arranged at intervals in the vehicle longitudinal direction. A cargo box 4 is placed on the chassis frame 2. The cargo box 4 is fixed to a mount bracket 3 fixed to side members 5 and 6 with bolts and nuts (not shown).

[0023] A plurality of mount brackets 3 are provided at intervals in the longitudinal direction of the vehicle on the outer sides of the side members 5, 6 in the vehicle width direction. Of the plurality of mount brackets 3, the mount bracket 3 located at the rearmost position of the vehicle is provided near the front-rear position of the rearmost cross member 10.

[0024] The axles of the rear wheels 7 of the vehicle 1 are suspended by a suspension device 8 using leaf springs 11 . The leaf springs 11 are disposed below the side members 5, 6 so as to extend in the direction in which the side members 5, 6 extend, i.e., in the longitudinal direction of the vehicle. The front ends of the leaf springs 11 are supported by the side members 5, 6 via front connecting shafts (not shown) so as to be rotatable in the vertical direction of the vehicle.

[0025] The rear end of the leaf spring 11 is supported by the side members 5, 6 via a shackle 12 so as to be rotatable in the vertical direction of the vehicle. The shackle 12 is supported by the side members 5, 6 behind and in the vicinity of the cross member 10.

[0026] The shackle 12 is connected to the side members 5, 6 by a shackle pin 41 (connecting shaft) inserted into an insertion hole 13 extending in the vehicle width direction provided in the side wall of the side members 5, 6, and is supported so as to be rotatable around the insertion hole 13, and is also structured to support the rear end of the leaf spring 11 so as to be rotatable around an axis extending in the vehicle width direction.

[0027] The side members 5, 6 are formed by butting together and welding both ends of an inner member 19 and an outer member 20, which are formed by bending sheet metal into a U-shape. The side members 5, 6 are hollow with a box-shaped longitudinal cross section, and have an upper wall 21, a lower wall 22, an inner wall 23, and an outer wall 24. The upper wall 21 and the lower wall 22 have weld lines 25 where the inner member 19 and the outer member 20 butt together.

[0028] The cross member 10 is hollow and has a box-shaped vertical cross section, and has an upper wall 26, a lower wall 27, a front wall 28, and a rear wall 29. The ends of the cross member 10 are abutted against the inner walls 23 of the side members 5, 6 on the inner side in the vehicle width direction and fixed thereto by welding.

[0029] As shown in Figure 3, the mount bracket 3 has a U-shaped cross section and includes an upper wall 30 and two support side walls 31, 32. The mount bracket 3 is arranged so that the upper wall 30 and the support side walls 31, 32 extend perpendicularly in the vehicle width direction from the outer side walls 24 of the side members 5, 6. The upper wall 30 of the mount bracket 3 is arranged to extend horizontally of the vehicle 1 at approximately the same vertical height as the upper walls 21 of the side members 5, 6, and the two support side walls 31, 32 are arranged side by side and spaced apart in the vehicle fore-and-aft direction. Therefore, the mount bracket 3 is arranged so that the opening of the U-shaped cross section faces downward.

[0030] The ends of the support side walls 31, 32 of the mount bracket 3 facing the side members 5, 6 are bent perpendicularly outward in the vehicle longitudinal direction to form outer flange portions 35. The outer flange portions 35 are fitted to the outer wall 24 of the side member, and their outer peripheries are fixed to the outer wall 24 by welding. In addition, the outer flange portions 35 of the mount bracket 3 each have a substantially semicircular cutout portion 36 formed thereon.

[0031] A bolt hole 37 is provided in the upper wall 30 of the mounting bracket 3, and a bolt is inserted into and fastened together with a bolt hole provided in a strength member at the bottom of the cargo box 4 or a bolt hole provided in the mounting bracket fixed to the bottom of the cargo box 4, thereby detachably fixing the cargo box 4 to the side members 5 and 6 via the mounting bracket 3.

[0032] 4 and 5 are views showing the lower structure near the rear support portion of the left leaf spring 11 according to an embodiment of the present invention, and near the connection portion between the left side member 5 and the rearmost cross member 10. Fig. 4 is a perspective view, and Fig. 5 is a top view. Fig. 4 is a view showing the vicinity of the connection portion between the left side member 5 in the vehicle width direction and the rearmost cross member 10, as viewed from above and rearward in the approximate center in the vehicle width direction of the vehicle 1.

[0033] The side member 5 is provided with a tubular portion 40 near the rear of the cross member 10, which connects the shackle 12. The tubular portion 40 is a cylindrical member whose axis extends in the vehicle width direction and is disposed so as to penetrate the side member 5, and has an insertion hole 13 formed therein into which a circular rod-shaped shackle pin 41 is inserted. The shackle 12 has a pair of plate members disposed so that one end thereof sandwiches the side member 5 on the left and right, and one end of the shackle 12 is supported by the side member 5 by the shackle pin 41 so as to be rotatable in the vertical direction. Both ends of the tubular portion 40 are disposed so as to protrude slightly outward from the side walls (inner wall 23, outer wall 24) of the side member 5, and are fixed to the side walls of the side member 5 by, for example, welding.

[0034] A reinforcing portion 45 is provided on the inner end (one end) side of the tubular portion 40 in the vehicle width direction, protruding radially outward from the outer peripheral wall of the tubular portion 40. The reinforcing portion 45 is a plate-like member having a hole into which the inner end of the tubular portion 40 is inserted, and is fixed around its entire periphery by welding to the outer peripheral surface of the inner end of the tubular portion 40. The reinforcing portion 45 has a first portion 45a extending toward the front of the vehicle (first direction) toward the cross member 10, and a second portion 45b provided contiguous with the first portion 45a and extending toward the rear of the vehicle (second direction).

[0035] The second portion 45b is substantially annular and has a hole into which the inner end of the tubular portion 40 is inserted, and is fixed by welding while abutting against the inner wall 23 of the side member 5. Therefore, one end of the tubular portion 40 is fixed to the side member 5 via the reinforcing portion 45.

[0036] The first portion 45a extends linearly along the inner surface of the side member 5 toward the front of the vehicle from the second portion 45b to a position close to the rear wall 29 of the cross member 10. The support side wall 31 on the rear side of the vehicle's rearmost mount bracket 3 is located in a longitudinal position between the rear wall 29 of the vehicle's rearmost cross member 10 and the front end of the reinforcing portion 45. The first portion 45a of the reinforcing portion 45 may extend toward the front of the vehicle until it contacts the rear wall 29 of the cross member 10. The rear wall 29 of the cross member 10, the front end of the reinforcing portion 45, and the support side wall 31 on the rear side of the vehicle's rearmost mount bracket 3 may be located in approximately the same or nearby longitudinal positions.

[0037] Furthermore, the inner member 19 on the inside of the side member 5 in the vehicle width direction is divided into a front inner member 19a on the vehicle front side and a rear inner member 19b on the vehicle rear side between the front wall 28 and rear wall 29 of the cross member 10 and at a position forward of the center position in the fore-and-aft direction of the cross member 10. The rear end of the front inner member 19a and the front end of the rear inner member 19b are connected by welding (connection portion 38). Furthermore, the rear inner member 19b is formed to have a thickness thinner than that of the front inner member 19a and the outer member 20.

[0038] Furthermore, the rear inner member 19b gradually becomes longer in a linear manner in the vehicle width direction as it extends rearward from the cylindrical portion 40, and accordingly, the rear portion of the outer member 20 gradually becomes shorter in the vehicle width direction as it extends rearward from the cylindrical portion 40. As a result, the proportion of the side member 5 taken up by the rear inner member 19b becomes larger than that of the outer member 20 as it extends rearward from the cylindrical portion 40 toward the vehicle rear. At the rear end of the side member 5, the outer member 20 does not have substantially the upper wall 21 or the lower wall 22 but only the outer wall 24, and the vehicle width of the rear inner member 19b is substantially the same as the vehicle width of the side member 5.

[0039] Two reinforcements 50, 51 are provided within the side members 5, 6 near the connection with the cross member 10, and are spaced apart from each other in the vehicle longitudinal direction, which is the extension direction of the side member 5, to reinforce the side member 5.

[0040] The reinforcements 50, 51 are rectangular thick plate members, and the entire periphery thereof is welded and fixed to the inner wall of the side member 5. That is, the reinforcements 50, 51 have the effect of supporting the inner wall of the side member 5 and improving the strength and rigidity of the side member 5. The vehicle rear reinforcement 50 is disposed in a front-to-rear position between the rear wall 29 of the cross member 10 at the rearmost position of the vehicle and the front end of the reinforcing portion 45. Note that the rear wall 29 of the cross member 10, the front end of the reinforcing portion 45, the support side wall 31 on the vehicle rear side of the mount bracket 3, and the vehicle rear reinforcement 50 may be disposed in approximately the same or nearby front-to-rear positions.

[0041] On the other hand, the reinforcement 51 on the front side of the vehicle is located slightly rearward of the front wall 28 of the cross member 10 and slightly forward of the connection position between the front inner member 19a and the rear inner member 19b.

[0042] The reinforcement 50 has a two-piece structure composed of an inner reinforcement 50a fixed to the inner member 19 and an outer reinforcement 50b fixed to the outer member 20. The inner reinforcement 51a is fixed to the inside of the inner member 19 by welding, and the outer reinforcement 51b is fixed to the inside of the outer member 20 by welding. When manufacturing the side member 5 by welding the inner member 19 and the outer member 20 together, the inner reinforcement 51a and the outer reinforcement 51b are partially overlapped and connected to each other at the overlapping portion by welding.

[0043] Similarly to the reinforcement 50 on the rear side of the vehicle, the reinforcement 51 on the front side of the vehicle is configured by connecting an inner reinforcement 51a and an outer reinforcement 51b. In the above embodiment, the structure of the side member 5 on the left side of the vehicle has been described, but the side member 6 on the right side of the vehicle may also be made to have a similar structure that is symmetrical on the left and right sides.

[0044] As described above, in this embodiment, the reinforcing portion 45 extends along the inner wall 23 of the side members 5, 6 so as to surround the inner end in the vehicle width direction of the tubular portion 40 into which the shackle pin 41 is inserted. This increases the rigidity of the support portion of the leaf spring 11 of the vehicle 1, and increases the rigidity of the connecting portion between the shackle 12 and the side members 5, 6, i.e., the side members 5, 6 near the rear end support portion of the leaf spring 11 that is the suspension device 8 for the rear wheel 7. This makes it possible to improve the handling stability and ride comfort of the vehicle 1.

[0045] Furthermore, the reinforcing portion 45 has a second portion 45b that surrounds the tubular portion 40 and a first portion 45a that extends from the second portion 45b to the front of the vehicle (first direction) to the vicinity of the cross member 10, and the first portion 45a and the second portion 45b form a single continuous plate-like member, so that the rigidity of the side members 5, 6 between the tubular portion 40 and the cross member 10 can be increased with a simple structure, and the rigidity of the side members 5, 6 against the load received from the leaf spring 11 can be effectively increased.

[0046] In addition, the second part 45b of the reinforcing portion 45 and the tubular portion 40 are fixed by welding, and the reinforcing portion 45 is structured to hold the tubular portion 40, so that the reinforcing portion 45 can hold the tubular portion 40 against the side members 5, 6 without any rattling.

[0047] Furthermore, of the two ends of the tubular portion 40 extending in the vehicle width direction, a reinforcing portion 45 is provided at the end on the inner side in the vehicle width direction that is closer to the cross member 10, so that the cross member 10 effectively suppresses deflection due to the load acting on the tubular portion 40 from the leaf spring 11, and the rigidity of the support portion of the leaf spring 11 can be more effectively increased with fewer reinforcing portions 45.

[0048] Furthermore, since the second portion 45b of the reinforcing portion 45 is approximately annular and surrounds the tubular portion 40, it is possible to reinforce the support portion of the leaf spring 11 while reducing the space occupied by the second portion 45b, compared to, for example, a case in which the first portion 45a and the second portion 45b of the reinforcing portion 45 are combined to form a rectangular shape.

[0049] Furthermore, since the reinforcing portion 45 extends linearly from the tubular portion 40 toward the cross member 10 in the vehicle longitudinal direction, which is the extension direction of the side members 5, 6, the length of the reinforcing portion 45 can be reduced while bringing the extended end closer to the cross member 10. This makes it possible to increase the rigidity of the support portion of the leaf spring 11 while minimizing the weight increase due to the reinforcing portion 45.

[0050] In addition, the width of the first portion 45a and the second portion 45b of the reinforcing portion 45 in the vertical direction (the direction perpendicular to the extending direction of the side members 5, 6) is formed to be larger than that of the tubular portion 40, thereby significantly increasing the rigidity of the side members 5, 6. Furthermore, the reinforcing portion 45 is configured so that the tubular portion 40 is included within its vertical width, so that the reinforcing portion 45 can efficiently and significantly increase the rigidity of the side members 5, 6 in the vicinity of the tubular portion 40.

[0051] In addition, of the side members 5 and 6, the inner member 19 on the inside of the vehicle is divided into a front inner member 19a and a rear inner member 19b at the front and rear, and the front inner member 19a and the rear inner member 19b are connected near the connection position with the cross member 10 to form the inner member 19.

[0052] Of the front inner member 19a and the rear inner member 19b, the rear inner member 19b, which is closer to the tubular portion 40 than the connection position with the cross member 10, is formed from a member with a thinner plate thickness than the front inner member 19a on the opposite side from the tubular portion 40.

[0053] This allows the weight of the rear inner member 19b to be reduced, and furthermore, makes the rear ends of the side members more easily crushable, thereby improving collision performance. Also, even if the rear inner member 19b is made thinner, the rigidity of the side members 5, 6 near the cylindrical portion 40 is ensured.

[0054] Furthermore, since the cross member 10 is located at the rearmost of the multiple cross members provided on the vehicle 1 and the tubular portion 40 is located at the rear of the cross member 10, the reinforcing portion 45 can increase the rigidity of the side members 5, 6 near the tubular portion 40 at the support portion of the leaf spring 11 that is supported behind the rearmost cross member 10. Here, since the rear inner member 19b is formed from a member with a thinner plate thickness than the outer member 20 and the front inner member 19a, the plate thickness of the side members 5, 6 can be made thinner behind the rear support portion of the leaf spring 11, which is less likely to receive a relatively large load while the vehicle is running, and the weight of the side members 5, 6 can be significantly reduced.

[0055] Furthermore, two reinforcements 50, 51 are provided at a distance in the vehicle longitudinal direction within the side members 5, 6 near the connection portion of the cross member 10, thereby further improving the strength and rigidity of the side members 5, 6 near the connection portion of the cross member 10. Therefore, even if stress occurs at the connection portion of the side members 5, 6, it is possible to suppress deformation of the cross section of the side members 5, 6. This improves the torsional rigidity of the side members 5, 6 near the connection portion of the cross member 10 and further near the rear support portion of the leaf spring 11, thereby improving the handling stability of the vehicle.

[0056] Of the two reinforcements 50, 51 provided near the connection portion of the cross member 10, the reinforcement 50 on the rear side of the vehicle is positioned at a position in the fore-and-aft direction of the vehicle between the rear wall 29 of the cross member 10 and the front end of the reinforcing portion 45, thereby improving the strength and rigidity of the side members 5, 6 near the connection portion between the rear wall 29 of the cross member 10 and the side members 5, 6, and near the support portion of the leaf spring 11.

[0057] Furthermore, the reinforcement 50 on the vehicle rear side, the support side wall 31 on the vehicle rear side of the mount bracket 3, and the rear wall 29 of the cross member 10 are arranged to be connected in a substantially straight line by the reinforcement 50, and the reinforcing portion 45 extends up to the vicinity of the rear wall 29 of the cross member 10, so that the load input from the leaf springs 11 of the suspension device 8 can be distributed to the side members 5, 6 and the cross member 10. More specifically, the load is transmitted from the inner end of the tubular portion 40 in the vehicle width direction to the cross member 10 via the reinforcing portion 45 and the inner member 19, while the load is transmitted from the outer end of the tubular portion 40 in the vehicle width direction to the outer member 20 and also to the strength member at the bottom of the cargo box 4 via the mount bracket 3. This makes it possible to further improve the rigidity of the support portion of the leaf spring 11 by utilizing the cargo box 4.

[0058] Furthermore, since semicircular cutout 36 is formed in outer flange 35 of mount bracket 3, a long welding length can be ensured for fixing outer flange 35 to outer wall 24 of side member 5. Furthermore, by extending the upper part of outer flange 35 on the vehicle rear side so that it approaches tubular portion 40, the distance between the support portion of leaf spring 11 and mount bracket 3 can be shortened, and the rigidity of the outer member 20 side of side member 5 near tubular portion 40 can be improved.

[0059] The present invention is not limited to the above-described embodiments. For example, the shape of the reinforcing portion 45 may be changed as appropriate, such as the vertical length or the length in the vehicle longitudinal direction. The second portion 45b may be rectangular, or the first portion 45a and the second portion 45b may have the same vertical width, making the reinforcing portion 45 rectangular overall. The support position of the tubular portion 40 relative to the reinforcing portion 45 may be changed as appropriate, for example, by positioning the support position of the tubular portion 40 on the first portion 45a or at a position spanning the first portion 45a and the second portion 45b. The second portion 45b may also be configured to extend further in the opposite direction (toward the rear of the vehicle) from the first portion 45a.

[0060] Furthermore, in the above embodiment, the second portion 45b of the reinforcing portion 45 and the cylindrical portion 40 are fixed by welding, but the second portion 45b and the cylindrical portion 40 may be supported without being fixed. Also, for example, the reinforcing portion 45 may extend obliquely in the longitudinal direction of the vehicle and in the vertical direction of the vehicle along the inner member 19. However, it is desirable that the front end of the reinforcing portion 45 extend linearly in the longitudinal direction of the vehicle so as to approach the cross member 10 at a short distance.

[0061] Furthermore, in the above embodiment, the present invention is adopted to provide a reinforcing portion 45 between the cross member 10 at the rearmost part of the vehicle and the rear support portion of the leaf spring 11, but the present invention may also be applied to a cross member other than the rearmost part, or to a cross member 10 that has a support portion for the leaf spring 11 on the front side. For example, if the cross member 10 has a support portion for the leaf spring 11 on the front side, the reinforcing portion 45 is positioned so as to extend toward the rear of the vehicle toward the cross member 10. The present invention may also be applied to the support portion on the front side of the leaf spring 11.

[0062] In the above embodiment, the reinforcing portion 45 is provided along the inner member 19 of the side members 5 and 6, but a reinforcing portion similar to the reinforcing portion 45 may be further provided along the outer member 20. Furthermore, the detailed structures of the side members 5, 6, the cross member 10, the cylindrical portion 40, etc. may be changed as appropriate. The vehicle 1 may also not have a luggage box. The present invention can be widely applied to vehicles equipped with leaf springs as suspension devices. [Explanation of symbols]

[0063] 1 vehicle 3 Mounting Bracket 4 packing boxes 5, 6 Side members 8. Suspension device 10 Cross member 11 Leaf spring 19a Front inner member 19b Rear inner member 40 Cylindrical part 41 Shackle pin (connecting shaft) 45 Reinforcement 45a Part 1 45b Part 2 50 Reinforce

Claims

1. a pair of side members arranged at an interval in a vehicle width direction of the vehicle and extending in a front-rear direction of the vehicle; a cross member extending in the vehicle width direction and connecting the pair of side members; leaf springs arranged along the pair of side members, respectively, to support the axles of the vehicle; a connecting shaft that rotatably connects one end of the leaf spring to the side member, the side member and the connecting shaft are connected at a position spaced apart in the vehicle longitudinal direction from a connection portion between the side member and the cross member, a cylindrical portion that penetrates through a side surface of the side member in the vehicle width direction and is fixed to the side member, and into which the connecting shaft is rotatably inserted; a reinforcing portion provided on the side surface of the side member so as to surround the cylindrical portion on at least one end side of the cylindrical portion, A vehicle undercarriage structure characterized in that the reinforcing portion has a first portion extending in a first direction toward the cross member, and a second portion that is continuous with the first portion and extends in a second direction opposite to the first direction.

2. The vehicle undercarriage structure according to claim 1 , wherein the reinforcing portion holds the one end of the cylindrical portion.

3. 3. The vehicle underbody structure according to claim 1, wherein the reinforcing portion is provided at an inner end in the vehicle width direction of both end portions of the tubular portion.

4. 4. The vehicle undercarriage structure according to claim 1, wherein the second portion has a substantially annular shape surrounding the cylindrical portion.

5. 4. The vehicle undercarriage structure according to claim 1, wherein the first portion is disposed so as to extend linearly toward the cross member in the extending direction of the side members.

6. 5. The vehicle underbody structure according to claim 1, wherein the first portion and the second portion have a width in a direction perpendicular to the extending direction of the side member that is larger than that of the tubular portion.

7. A vehicle undercarriage structure as described in any one of claims 1 to 6, characterized in that the side member is formed of a material with a thinner plate thickness in the portion on the tubular portion side of the connection position with the cross member in the extension direction than in the portion on the opposite side of the tubular portion side.

8. the cross member is disposed at the rearmost of a plurality of cross members of the vehicle that connect the pair of side members, 8. The vehicle undercarriage structure according to claim 1, wherein the tubular portion is disposed rearward of the cross member.

9. The side members are hollow members having reinforcements extending in the vehicle width direction therein and connecting the inner walls of both side surfaces in the vehicle width direction, 9. The vehicle underbody structure according to claim 1, wherein the reinforcement is disposed at a front-rear position of the vehicle between the reinforcing portion and the cross member.

10. The vehicle includes a mount bracket for fixing a cargo box to the side member, 10. The vehicle undercarriage structure according to claim 1, wherein the mount bracket is disposed at a front-rear position of the vehicle between the reinforcing portion and the cross member.

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