Frame Structure

Abstract

To provide a frame structure which can alleviate unique stress generated in an end cross even when a narrow width part is provided in a rear end portion of a main frame.SOLUTION: A frame structure 1 is the frame structure 1 applied to rear end portions of a pair of main frames 2. Narrow width parts 22 of the pair of main frames 2 are connected with each other by an end cross 4 extending in a width direction of a vehicle. The end cross 4 comprises: a side surface part 4a which extends in the width direction of the vehicle; an upper surface part 4b which protrudes in a front-rear direction from an upper end of the side surface part 4a; a bottom surface part 4c which protrudes in a same direction as the upper surface part 4b from a lower end of the side surface part 4a; and an upper flange part 4d which protrudes downward from both ends in the width direction on the upper surface part 4b. A corner part formed by the upper surface part 4b, the side face part 4a and the upper flange part 4d is provided with an upper side notch F1 including a second region F12 overlapping the bottom surface part 4c when viewed from a vertical direction of the vehicle.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a frame structure. [Background technology]

[0002] An example of a conventional frame structure is a frame structure used in an underfloor storage lifting device described in Patent Document 1. In this frame structure, a suspension area for suspending a retractable tailgate is provided at the rear end portion of a main frame extending in the fore-and-aft direction of a vehicle such as a truck. The tailgate has a slide guide attached to the rear end portion of the main frame, and can be driven between a retracted position and a lifted position by engaging a runner that is slidable relative to the slide guide. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-040896 Summary of the Invention [Problem to be solved by the invention]

[0004] In a vehicle in which a retractable tailgate is suspended from the rear end portion of the main frame, it is necessary to adjust the shape of the rear end portion of the main frame and ensure a certain amount of space in the suspension area of ​​the tailgate to avoid interference between the main frame and the tailgate. To meet this requirement, for example, it is conceivable to form a narrow portion whose vertical width is smaller than that of the main body of the main frame by cutting out the lower side of the rear end portion of the main frame in the area corresponding to the suspension area of ​​the tailgate.

[0005] The rear end portions of a pair of main frames are connected to each other by an end cross. However, in a frame structure in which a narrow portion is formed at the rear end portion of the main frame, the cross section of the rear end portion is asymmetrical from top to bottom, so when stress is applied to the main frame, a specific stress may be applied to the end cross.

[0006] One example of this particular stress is a phase input that applies compressive stress to the upper side of the end cross while applying tensile stress to the lower side of the end cross. To suppress this particular stress, it is possible to increase the thickness of the rear end portions of the main frames or the end crosses, or to install separate end crosses that connect the rear end portions of the main frames together, but these measures pose problems such as increased mass and cost of the frame structure.

[0007] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a frame structure that can alleviate the unique stress that occurs in the end cross even when a narrow portion is provided at the rear end portion of the main frame. [Means for solving the problem]

[0008] A frame structure according to one aspect of the present disclosure is a frame structure applied to the rear end portions of a pair of main frames extending in the fore-and-aft direction of a vehicle, wherein the main frames have a narrow portion whose vertical width is smaller than that of the main body portion of the main frame formed by cutting out the lower side of the rear end portion, and the narrow portions of the pair of main frames are connected by an end cross extending in the width direction of the vehicle, and the end cross has side portions extending in the width direction of the vehicle, an upper surface portion extending in the fore-and-aft direction from the upper end of the side surface portion, a bottom surface portion extending in the same direction as the top surface portion from the lower end of the side surface portion, and upper flange portions joined to the narrow portion and extending downward from both ends of the top surface portion in the width direction, and upper cutout portions are provided at the corners formed by the top surface portion, side portions, and upper flange portions, including an area that overlaps with the bottom surface portion when viewed from the up-and-down direction of the vehicle.

[0009] In this frame structure, upper cutouts are provided at the corners of the end crosses formed by the top surface, side surface, and upper flange, including areas that overlap with the bottom surface when viewed from the vehicle's vertical direction. These upper cutouts ensure that the upper side of the end cross can easily deform under compressive stress, thereby mitigating stress concentration. The lower side of the end cross follows tensile stress, absorbing compressive stress on the upper side and tensile stress on the lower side in a balanced manner. Therefore, with this frame structure, even if a narrow width portion is provided at the rear end of the main frame, the unique stress applied to the end cross can be mitigated.

[0010] The end cross is joined to the narrow width portion and has lower flanges that extend upward from both widthwise ends of the bottom surface portion. Lower notches are provided at corners formed by the bottom surface portion, side surfaces, and lower flanges. The upper notches may have regions that do not overlap with the lower notches when viewed from the vertical direction of the vehicle. In this case, the lower notches ensure ease of deformation of the lower side of the end cross against tensile stress and reduce stress concentration. Furthermore, by providing the upper notches with regions that do not overlap with the lower notches, compressive stress on the upper side and tensile stress on the lower side can be absorbed in a more balanced manner.

[0011] The upper cutout portion may have a region that does not overlap with the lower cutout portion and extends in the longitudinal direction of the vehicle at a position on the upper surface away from the upper flange portion. In this case, the upper surface can be provided with a sufficient deformation margin for the upper flange portion while forming the upper cutout portion. This further ensures easy deformation of the end cross against compressive stress applied to the upper side. [Effects of the Invention]

[0012] According to the present disclosure, even when a narrow portion is provided at the rear end portion of the main frame, the stress specific to the end cross can be alleviated. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view showing a lower structure of a vehicle to which a frame structure according to an embodiment is applied; [Figure 2] FIG. 2 is a side view of a frame structure according to one embodiment. [Figure 3] (a) is a schematic cross-sectional view showing the deformation when a lateral force is applied to a frame structure in which a narrow portion is formed at the rear end portion of the main frame, and (b) is a schematic cross-sectional view showing the deformation when a vertical force is applied to a frame structure in which a narrow portion is formed at the rear end portion of the main frame. [Figure 4] FIG. 2 is an enlarged view of a main part of the end cross shown in FIG. [Figure 5] FIG. 5 is a schematic plan view of the end cross shown in FIG. 4. [Figure 6] FIG. 1A is a schematic cross-sectional view showing deformation when a lateral input is applied to a frame structure according to one embodiment, and FIG. 1B is a schematic cross-sectional view showing deformation when a vertical input is applied to a frame structure according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a preferred embodiment of a frame structure according to one aspect of the present disclosure will be described in detail with reference to the drawings.

[0015] Fig. 1 is a perspective view showing the undercarriage of a vehicle to which a frame structure according to one embodiment is applied. The frame structure 1 shown in Fig. 1 is a structure that is applied to the rear lower part of a vehicle, for example, a truck capable of carrying containers. As shown in Fig. 1, the underside of the vehicle according to this embodiment is provided with a pair of main frames 2 and a plurality of cross members 3.

[0016] The main frame 2 is a pair of left and right members that make up the chassis of the vehicle and extends in the longitudinal direction of the vehicle. The main frame 2 is made of, for example, a metal molding material with a roughly C-shaped cross section. The main body 21 of the main frame 2 has a side surface 2a and a top surface 2b and a bottom surface 2c that extend from the upper and lower ends of the side surface 2a in the same direction, perpendicular to the side surface 2a. The side surface 2a is provided with a through hole (not shown) that is used to connect the main frame 2 to other members.

[0017] The cross member 3 is a member that connects the pair of main frames 2, 2 and extends in the width direction of the vehicle. Each of the multiple cross members 3 is provided so as to be spaced apart from each other in the front-to-rear direction of the vehicle. In this embodiment, a total of seven cross members 3 are provided in the lower part of the vehicle, and six of the cross members 3 connect the main body portions 21, 21 of the pair of main frames 2. The cross members 3 may be joined to the pair of main frames 2 by, for example, bolt and nut fastening.

[0018] An end cross 4 is provided at the rear end portion of the main frame 2 as one of the cross members 3. The end cross 4 is a member that connects narrow width portions 22, 22 (described later) provided at the rear end portions of a pair of main frames 2, and extends in the width direction of the vehicle. The vertical width of the end cross 4 is formed smaller than the vertical width of the narrow width portion 22. Details of the end cross 4 will be described later.

[0019] The vehicle according to this embodiment is equipped with a retractable tailgate (not shown) for loading and unloading cargo into a container. For example, while the vehicle is traveling, the tailgate is stored in the rear lower part of the vehicle by being suspended from a suspension region R (described later) provided on the frame structure 1. Furthermore, for example, when loading and unloading cargo, the tailgate is driven in the longitudinal direction of the vehicle. Various types of tailgates can be used.

[0020] FIG. 2 is a side view of a frame structure according to one embodiment. As shown in FIG. 2, a suspension region R for the retractable tailgate described above is provided at the rear end portion of the main frame 2. To avoid interference between the main frame 2 and the tailgate, a narrow portion 22, which corresponds to the suspension region R and has a vertical width smaller than that of the main body portion 21 of the main frame 2, is formed at the rear end portion of the main frame 2. The narrow portion 22 is formed by cutting out the lower side of the rear end portion of the main frame 2. In this embodiment, the cutout portion F formed at the lower side of the rear end portion of the main frame 2 is formed over a certain range forward from the rear end of the main frame 2. The front portion of the cutout portion F has a gently curved shape so that the main body portion 21 and the narrow portion 22 are smoothly connected in a side view of the main frame 2.

[0021] The dimensions of the cutout F can be designed appropriately taking into consideration the strength and dimensions of the main frame 2, the weight and dimensions of the tailgate, the ground clearance of the vehicle when the tailgate is suspended, etc. In this embodiment, the length of the cutout F in the front-to-rear direction is greater than the length of the tailgate suspended in the suspension region R in the front-to-rear direction when it is in a stored state, and the length of the cutout F in the up-to-down direction is approximately half or less of the vertical width of the side surface portion 2a of the main frame 2.

[0022] In a frame structure in which a narrow portion is formed at the rear end portion of the main frame, the cross-sectional shape of the rear end portion is asymmetrical from top to bottom, so when stress is input to the main frame, it is thought that specific stress will be applied to the end cross.

[0023] Figure 3(a) is a schematic cross-sectional view showing the deformation when a lateral input is applied to a frame structure having a narrow portion formed at the rear end of the main frame, and Figure 3(b) is a schematic cross-sectional view showing the deformation when a vertical input is applied to a frame structure having a narrow portion formed at the rear end of the main frame.

[0024] 3(a), when a lateral input S1 (here, an input from the left side of the page) is applied to the pair of main frames 102, 102, the main frame 102 on the opposite side (here, the right side of the page) is displaced and tilts significantly relative to the main frame 102 on the input side (here, the left side of the page) due to the narrow width portion 122 provided at the rear end of the main frame 102. At this time, the lower sides of the main frames 102 are displaced more than the upper sides, so the distance B between the lower sides of the main frames 102 becomes larger than the distance A between the upper sides of the main frames 102.

[0025] 3(b), when a vertical input S2 (here, an input from the upper side of the page) is applied to the pair of main frames 102, 102, the main frames 102, 102 are displaced so as to widen downward due to the narrow portion 122 provided at the rear end of the main frame 102. At this time, the lower sides of each main frame 102 are displaced more than the upper sides, so the distance B between the lower sides of the main frames 102 becomes larger than the distance A between the upper sides of the main frames 102.

[0026] When the rear end portions of the main frames 102 are deformed as described above, a phase input may occur in which compressive stress is applied to the upper side of the end crosses while tensile stress is applied to the lower side of the end crosses. Possible solutions to suppress this type of specific stress include increasing the thickness of the rear end portions of the main frames 102 or the end crosses, or providing separate end crosses that connect the rear end portions of the main frames 102 together. However, these solutions pose problems, such as increased mass and cost of the frame structure.

[0027] To address this problem, in the frame structure 1, the end crosses 4 are configured in a way that can alleviate the specific stress that occurs in the end crosses 4, even when a narrow width portion 22 is provided at the rear end portion of the main frame 2. The configuration of the end crosses 4 will be described in detail below.

[0028] Figure 4 is an enlarged view of a main portion of the end cross member 4 shown in Figure 1. As shown in the figure, the end cross member 4 is made of a metal profile member having a generally C-shaped cross section. The end cross member 4 has a side portion 4a extending in the width direction of the vehicle, a top portion 4b extending from the upper end of the side portion 4a in the longitudinal direction of the vehicle, perpendicular to the side portion 4a, and a bottom portion 4c extending from the lower end of the side portion 4a in the same direction as the top portion 4b.

[0029] The end cross 4 also has upper flange portions 4d that extend downward from both widthwise ends of the top surface portion 4b, and lower flange portions 4e that extend upward from both widthwise ends of the bottom surface portion 4c. The upper flange portion 4d has two through holes 5, 5 that are used for connecting to, for example, the main frame 2. The lower flange portion 4e has two through holes 6, 6 that are used for connecting to, for example, the main frame 2. When joining the end cross 4 to the main frame 2, for example, fastening members such as bolts are inserted through the through holes of the main frame 2 and the through holes 5 and 6 in the upper and lower flange portions 4d and 4e, respectively, to join the upper and lower flange portions 4d and 4e to the narrow width portion 22. The lower end of the upper flange portion 4d and the upper end of the lower flange portion 4e are spaced apart vertically.

[0030] At the corners formed by the top surface 4b, the side surface 4a, and the upper flange 4d, upper cutouts F1 are formed by cutting out the corners from the top surface 4b to the lower end of the upper flange 4d. At the corners formed by the bottom surface 4c, the side surface 4a, and the lower flange 4e, lower cutouts F2 are formed by cutting out the corners from the bottom surface 4c to the upper end of the lower flange 4e.

[0031] FIG. 5 is a schematic plan view of the end cross shown in FIG. 4. In the example of FIG. 5, the upper surface portion 4b is illustrated by a solid line, and the bottom surface portion 4c is illustrated by a dashed line. As shown in the figure, the upper cutout portion F1 includes a first region F11 that overlaps with the lower cutout portion F2 when viewed from the vertical direction of the vehicle, and a second region F12 that does not overlap with the lower cutout portion F2. The second region F12 coincides with the region that overlaps with the bottom surface portion 4c when viewed from the vertical direction of the vehicle. The first region F11 has a substantially rectangular shape in plan view, similar to the region where the lower cutout portion F2 is formed. The second region F12 has a shape that protrudes toward the front of the vehicle when viewed from the vertical direction.

[0032] The second region F12 of the upper cutout F1 that does not overlap with the lower cutout F2 extends in the front-to-rear direction of the vehicle at a position on the upper surface 4b spaced apart from the upper flange 4d. In this embodiment, the second region F12 extends in the front direction of the vehicle from the inner end of the first region F11 in the vehicle width direction. By forming such upper cutout F1, the upper side of the end cross 4 is more easily deformed than the lower side of the end cross 4 in response to compressive stress.

[0033] FIG. 6(a) is a schematic cross-sectional view showing deformation when a lateral input is applied to a frame structure according to one embodiment, and FIG. 6(b) is a schematic cross-sectional view showing deformation when a vertical input is applied to a frame structure according to one embodiment.

[0034] As shown in FIG. 6(a), when a lateral force S1 (here, an force from the left side of the drawing) is applied to a pair of main frames 2, 2, the narrow width portion 22 at the rear end of the main frame 2 causes the main frame 2 on the opposite side to tilt significantly relative to the main frame 2 on the input side, as in the case of FIG. 3(a). In contrast, in this embodiment, the end crosses 4 are provided with the upper notch F1 and lower notch F2 described above. This ensures that the upper side of the end crosses 4 can easily deform under compressive stress and alleviates stress concentration, while the lower side of the end crosses 4 responds to tensile stress, absorbing compressive stress on the upper side and tensile stress on the lower side in a balanced manner. Therefore, when a lateral force S1 is applied, the difference between the distance A between the pair of upper main frames 2, 2 and the distance B between the lower main frames 2, 2 can be reduced.

[0035] As shown in FIG. 6(b), when a vertical force S2 (here, an force from above in the drawing) is applied to the pair of main frames 2, 2, as in the case of FIG. 3(b), the narrow portion 22 at the rear end of the main frame 2 causes the main frames 2, 2 to displace downward, widening toward the rear. In contrast, in this embodiment, the end crosses 4 are provided with the upper notch F1 and lower notch F2 described above. This ensures that the upper side of the end crosses 4 can easily deform under compressive stress and alleviates stress concentration, while the lower side of the end crosses 4 responds to tensile stress, absorbing compressive stress on the upper side and tensile stress on the lower side in a balanced manner. Therefore, when the vertical force S2 is applied, as in the case of a lateral force S1, the difference between the distance A between the pair of upper main frames 2, 2 and the distance B between the pair of lower main frames 2, 2 can be reduced.

[0036] As described above, in this frame structure 1, an upper cutout F1 including a second region F12 that overlaps with the bottom surface 4c when viewed from the vehicle's vertical direction is provided at the corner of the end cross 4 formed by the top surface 4b, side surface 4a, and upper flange 4d. This upper cutout F1 ensures that the upper side of the end cross 4 can easily deform in response to compressive stress, thereby mitigating stress concentration. The lower side of the end cross 4 follows tensile stress, absorbing compressive stress on the upper side and tensile stress on the lower side in a balanced manner. Therefore, in this frame structure 1, even when a narrow width portion 22 is provided at the rear end portion of the main frame 2, the unique stress applied to the end cross 4 can be mitigated.

[0037] In this embodiment, the end cross 4 is joined to the narrow width portion 22 and has lower flanges 4e that extend upward from both widthwise ends of the bottom surface 4c. Lower cutouts F2 are provided at the corners formed by the bottom surface 4c, the side surfaces 4a, and the lower flanges 4e. The upper cutouts F1 have second regions F12 that do not overlap with the lower cutouts F2 when viewed from the top-bottom direction of the vehicle. In this case, the lower cutouts F2 ensure ease of deformation of the lower side of the end cross 4 against tensile stress and reduce stress concentration. Furthermore, by providing the second regions F12 that do not overlap with the lower cutouts F2 in the upper cutouts F1, compressive stress on the upper side and tensile stress on the lower side can be absorbed in a more balanced manner.

[0038] In this embodiment, the second region F12 of the upper cutout F1 that does not overlap with the lower cutout F2 extends in the longitudinal direction of the vehicle at a position on the upper surface 4b away from the upper flange 4d. In this case, the upper cutout F1 is formed while ensuring sufficient deformation margin for the upper flange 4d on the upper surface 4b. This further ensures easy deformability against compressive stress applied to the upper side of the end cross 4.

[0039] While preferred embodiments of the present disclosure have been described above, the present disclosure is not necessarily limited to the above-described embodiments and various modifications are possible without departing from the spirit and scope of the present disclosure. For example, in the above-described embodiment, the second region F12 of the upper cutout F1 extends from the inner end of the first region F11 in the vehicle width direction toward the front of the vehicle. However, the second region F12 may extend from a portion outer than the inner end of the first region F11 toward the front of the vehicle. The shape, size, position, etc. of the upper cutout F1 are not limited to those described above and may be modified as appropriate.

[0040] In the above embodiment, a lower cutout F2 is provided at the corner formed by the bottom surface 4c, the side surface 4a, and the lower flange 4e. However, the lower cutout F2 does not have to be provided. Even in this case, the upper cutout F1 includes a second region F12 that overlaps with the bottom surface 4c when viewed from the vehicle's vertical direction, ensuring ease of deformation of the upper side of the end cross 4 against compressive stress and mitigating stress concentration. The lower side of the end cross 4 follows tensile stress, absorbing compressive stress on the upper side and tensile stress on the lower side in a balanced manner. Therefore, even with this configuration, the specific stress applied to the end cross 4 can be mitigated even when a narrow width portion 22 is provided at the rear end portion of the main frame 2. [Explanation of symbols]

[0041] 1...frame structure, 2...main frame, 4...end cross, 4a...side portion, 4b...top portion, 4c...bottom portion, 4d...upper flange portion, 4e...lower flange portion, 21...main body portion, 22...narrow portion, F1...upper cutout portion, F2...lower cutout portion, F11...first region (region), F12...second region (region).

Claims

1. A frame structure applied to rear end portions of a pair of main frames extending in the front-rear direction of a vehicle, a narrow portion having a vertical width smaller than that of a main body portion of the main frame is formed by cutting out a lower side of the rear end portion of the main frame; The narrow portions of the pair of main frames are connected to each other by end crosses extending in the width direction of the vehicle, The end cross is a side surface portion extending in a width direction of the vehicle; an upper surface portion extending in the front-rear direction from an upper end of the side surface portion; a bottom surface portion extending from a lower end of the side surface portion in the same direction as the top surface portion; upper flange portions joined to the narrow width portion and extending downward from both ends of the upper surface portion in the width direction; a lower flange portion joined to the narrow portion and projecting upward from both ends of the bottom surface portion in the width direction, a corner formed by the upper surface portion, the side surface portion, and the upper flange portion includes an area that overlaps with the bottom surface portion when viewed from the vertical direction of the vehicle, and an upper cutout portion is provided that cuts out the corner formed by the upper surface portion, the side surface portion, and the upper flange; a lower cutout portion that cuts out the corner formed by the bottom surface portion, the side surface portion, and the lower flange portion is provided at the corner formed by the bottom surface portion, the side surface portion, and the lower flange portion; A frame structure, wherein the upper cutout portion has an area that does not overlap with the lower cutout portion when viewed from the top-bottom direction of the vehicle.

2. The frame structure according to claim 1 , wherein a region of the upper cutout portion that does not overlap with the lower cutout portion extends in the longitudinal direction of the vehicle at a position on the upper surface portion spaced apart from the upper flange portion.

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