Joint Structure

Abstract

This joint structure comprises a first member having a top plate and a vertical wall, a second member joined to an axial direction end portion of the first member, and a third member joined to each of the first member and the second member, wherein: the first member has a first region portion, a second region portion and a third region portion; the first region portion has a first top plate and a first vertical wall in which the height of the vertical wall from the first top plate is a first height; the second region portion has a second top plate and a second vertical wall in which the height of the vertical wall from the second top plate is a second height; the third region portion has a third top plate and a third vertical wall connecting the first vertical wall and the second vertical wall; the height of the first top plate is lower than the height of the second top plate; and a ratio of the second height to the height from the third member to the second top plate in the second region portion is 0.4 to 0.8.

Description

[Technical Field]

[0001] The present invention relates to a joint structure. [Background technology]

[0002] Weight reduction is required to reduce the environmental impact of transportation equipment such as automobiles, ships, and railway vehicles, as well as various structures such as steel frame structures. For example, in the automotive field, the weight of the car body is reduced by using thinner steel materials, but there are concerns that the weight reduction will result in a decrease in the rigidity of the car body.

[0003] Therefore, in order to respond to the demand for weight reduction while suppressing a decrease in the rigidity of the vehicle body, it is necessary to improve the shape of each part and the joining structure between the parts, etc. In this specification, the structure around the joint where multiple parts are joined together may be referred to as a "joint structure."

[0004] As a vehicle body structure including a joint structure, Patent Document 1 discloses a vehicle underbody structure including a pair of rockers extending in the vehicle longitudinal direction and a floor cross member having one end joined to the lower part of the rockers. This vehicle underbody structure includes a connecting member that connects the inner side of the rockers in the vehicle width direction to the upper part of the floor cross member.

[0005] Patent document 2 discloses an automobile lower body structure comprising a floor panel that forms the floor of the passenger compartment, a side sill that extends in the fore-and-aft direction of the vehicle body along the vehicle width edge of the floor panel, and a cross member that extends inward in the vehicle width direction from the vehicle width edge of the floor panel.

[0006] Patent document 3 discloses a frame structure of a vehicle body that includes a first member arranged to extend in one direction, a second member arranged on the vehicle exterior side of the first member, a third member that is connected to the side of the first member from a direction intersecting the first member and forms the frame of the vehicle body together with the first member, and a fourth member that is provided between the first member and the second member on the longitudinal extension of the third member.

[0007] Patent Document 4 discloses a mounting structure for a suspension upper arm, which includes a suspension upper arm support bracket that connects an apron upper member and a front side member with a closed cross-sectional structure.

[0008] Patent document 5 discloses a reinforcing structure for an automobile floor panel in which a cross member is arranged in the width direction of the vehicle on a floor panel having a tunnel portion in the fore-and-aft direction of the vehicle body, a tunnel reinforcing member is crossed so as to straddle the cross member, and a seat mounting portion is provided on the cross member.

[0009] Patent Document 6 discloses a front body structure for an automobile that includes front side members that are arranged on each of the left and right sides of the vehicle body and extend in the longitudinal direction, and an instrument panel reinforcement that is arranged between the left and right front pillars and extends in the width direction. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent No. 6264864 [Patent Document 2] Japanese Patent Application Publication No. Hei 4 (1992)-303076 [Patent Document 3] Japanese Patent Application Publication No. 2004-322776 [Patent Document 4] Japanese Utility Model Application Publication No. Hei 3 (1991)-040171 [Patent Document 5] Japanese Patent Application Publication No. 2004-352080 [Patent Document 6] Japanese Patent Application Publication No. 2000-153779 Summary of the Invention [Problem to be solved by the invention]

[0011] The vehicle undercarriage structure described in Patent Document 1 has a joint structure in which another member, a connecting member, is joined to the upper surface of a floor cross member joined to the side of a rocker. However, joining another member to a structure in which the rocker and floor cross member are joined results in an increase in weight.

[0012] From the viewpoint of achieving both weight reduction and rigidity, a structure in which the rigidity per unit weight is excessively reduced due to the weight reduction is undesirable. In other words, it is desirable to create a joint structure that can reduce weight while suppressing an excessive decrease in rigidity per unit weight. However, such a joint structure is neither disclosed nor suggested in Patent Documents 1 to 6. Furthermore, the problem of reducing weight in a joint structure while suppressing an excessive decrease in rigidity per unit weight can also arise in structures other than automobiles.

[0013] The present invention has been made in consideration of the above circumstances, and has an object to provide a joint structure that is lightweight and can suppress an excessive decrease in rigidity per unit weight. [Means for solving the problem]

[0014] The present inventors focused on the relationship between the height and rigidity of the vertical wall near the joint between the first and second members in a joint structure including a first member having a top plate and a vertical wall, and a second member to which an axial end of the first member is joined. They discovered that by keeping the height of the vertical wall near the joint within a specific range, it is possible to reduce weight while suppressing an excessive decrease in rigidity per unit weight, and arrived at the present invention.

[0015] One aspect of the present invention that solves the above-mentioned problems is For automobile subframesA joint structure comprising: a first member having a top plate and a vertical wall; a second member joined to an axial end of the first member; and a third member joined to each of the first member and the second member, wherein the vertical wall extends from the top plate toward the third member, the first member has a first region, a second region located between the first region and the second member, and a third region located between the first region and the second region, the first region having a first top plate that is a part of the top plate, and a first vertical wall having a first height from the first top plate, and the first region is joined to the third member, The second region has a second top plate that is a part of the top plate and a second vertical wall, the height of the vertical wall from the second top plate being a second height, the second region is joined to the second member and not joined to the third member, there is a space between the second vertical wall and the third member, the third region has a third top plate that is a part of the top plate and a third vertical wall connecting the first vertical wall and the second vertical wall, the height of the first top plate is lower than the height of the second top plate, and the ratio of the second height to the height from the third member to the second top plate in the second region is 0.4 to 0.8.

[0016] Another aspect of the present invention is For automobile subframes A joint structure, comprising: a first member having a top plate and a vertical wall; and a joint member joined to an axial end of the first member. Thethe first area portion has a first top plate that is a part of the top plate and a first vertical wall, the height of the vertical wall from the first top plate being a first height; the first area portion is joined to the third member; the second area portion has a second top plate that is a part of the top plate and a second vertical wall, the height of the vertical wall from the second top plate being a second height; the second area portion is joined to the second member but not to the third member; there is a space between the second vertical wall and the third member; the first top plate and the second top plate are in the same plane; and the ratio of the second height to the height from the third member to the top plate in the second area portion is 0.3 to 0.8. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a joint structure that is lightweight and can prevent an excessive decrease in rigidity per unit weight. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 2 is a perspective view for explaining an application location of a joint structure according to an embodiment of the present invention. [Figure 2] FIG. 1 is a perspective view for explaining a schematic configuration of a joint structure according to a first embodiment. [Figure 3] FIG. 2 is a side view for explaining a schematic configuration of a joint structure. [Figure 4] 4A and 4B are views showing cross sections AA and BB in FIG. 3. [Figure 5] FIG. 10 is a side view for explaining the definition of H2 / H0. [Figure 6] FIG. 1 is a side view showing a conventional joint structure in which H2 / H0 is 1.0. [Figure 7] FIG. 10 is a perspective view for explaining a schematic configuration of a joint structure according to a second embodiment. [Figure 8]FIG. 2 is a side view for explaining a schematic configuration of a joint structure. [Figure 9] FIG. 1 is a side view showing a conventional joint structure in which H2 / H0 is 1.0. [Figure 10] FIG. 10 is a side view of a joint structure for explaining simulation conditions. [Figure 11] 10 is a graph showing the results of simulation (1). [Figure 12] 10 is a graph showing the results of simulation (2). [Figure 13] FIG. 10 is a side view of a joint structure for explaining simulation conditions. [Figure 14] 10 is a graph showing the results of simulation (3). DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0020] First Embodiment (Applicable areas of joint structure) First, an application location of the joint structure according to the first embodiment will be described with reference to Fig. 1. The example shown in Fig. 1 is an example in which the joint structure 1 is applied to a grid-shaped subframe 90 to which an automobile suspension arm (not shown) is attached. Fig. 1 illustrates the vicinity of the attachment portion of the suspension arm, and in the example shown in Fig. 1, the X direction is the vehicle length direction, the Y direction is the vehicle width direction, and the Z direction is the vehicle height direction.

[0021] The joint structure 1 in the application example of FIG. 1 includes a cross frame 10 as a first member, a bracket 20 as a second member, and a bottom plate 30 as a third member. The cross frame 10 extends in the vehicle width direction, and a bracket 20 that serves as a mounting portion for a suspension arm (not shown) is joined to an end of the cross frame 10 in the vehicle width direction. Both the cross frame 10 and the bracket 20 are joined to the bottom plate 30. In addition, an axial end of a side frame 91 that extends in the vehicle length direction and is one of the components of a subframe 90 of an automobile is joined to a side surface of the axial end of the cross frame 10.

[0022] Note that the grid-shaped subframe 90 in the example of Fig. 1 has a pair of cross frames extending parallel to each other and a pair of side frames extending parallel to each other, but Fig. 1 only illustrates one cross frame 10 of the pair of cross frames and one side frame 91 of the pair of side frames, and does not illustrate the other cross frame or side frame. Furthermore, the "automobile subframe" to which the joint structure 1 is applied includes a front subframe to which a front suspension arm of the vehicle body is attached, and a rear subframe to which a rear suspension arm of the vehicle body is attached.

[0023] Furthermore, the application of the joint structure according to the present disclosure is not limited to automobile subframes, but may also be applied to locations where parts are joined in a T-shape. For example, at least one of the first member, second member, and third member included in the joint structure does not have to be an automobile frame member like the subframe 90 described above, or may be an automobile frame member. The automobile frame member referred to here is a member used as the frame of the vehicle body, such as a front bumper beam, a rear bumper beam, a front side member, a rear side member, a side sill, a floor cross member, a roof side rail, a roof cross member, a center pillar, or a side rail or cross member that constitutes a ladder frame.

[0024] For example, the joint structure according to the first embodiment may be applied to a joint between a floor cross member and a side sill, which are part of the vehicle body lower structure. In this case, the first member is a floor cross member extending in the vehicle width direction, the second member is a side sill extending in the vehicle length direction, and the third member is, for example, a floor panel. Also, for example, the joint structure may be applied to a joint between a roof cross member and a roof side rail, which are part of the vehicle body upper structure. In this case, the first member is a roof cross member extending in the vehicle width direction, the second member is a roof side rail extending in the vehicle length direction, and the third member is, for example, a roof panel. In other words, the joint structure may also be applied to a location where parts are joined in a T-shape.

[0025] Furthermore, the first member is not limited to a member extending in the vehicle width direction, and may be a member extending in the vehicle length direction or vehicle height direction, for example, depending on the location where the joint structure is applied. Furthermore, the joint structure is not limited to being applied to automobile bodies, and can be applied to locations where rigidity is required in structures such as ships, railway vehicles, and steel frame structures.

[0026] The second member may not be a single part, but may be a member composed of multiple parts. For example, if the second member is composed of two parts, a joint structure may be formed by joining the first member to one part and the third member to the other part. Furthermore, the third member is not limited to a plate extending in the same plane, and may have steps, slopes, etc.

[0027] The materials of the first to third members are changed as appropriate depending on the application location of the joint structure, but when the joint structure is applied to an automobile body, for example, metal materials such as steel, aluminum alloy members, magnesium alloy members, etc. Furthermore, when the joint structure is applied to an automobile body and the materials of the first to third members are steel, for example, steel having a tensile strength of 440 MPa or more, 590 MPa or more, or 780 MPa or more is used.

[0028] The plate thicknesses of the first to third members are changed as appropriate depending on the application location of the joint structure, but are, for example, 1 to 5 mm when the joint structure is applied to an automobile body. The overall length, overall width, and overall height of the first to third members are changed as appropriate depending on the application location of the joint structure, but when the joint structure is applied to an automobile body, the length of the first member in the axial direction (Y direction) is, for example, 500 to 3000 mm. Furthermore, the size of the cross section perpendicular to the axial direction (Y direction) of the tubular portion formed by joining the first and third members is, for example, 50 to 200 mm square.

[0029] The means for joining the first to third members may be changed as appropriate depending on the application location of the joint structure, but for example, joining means using various types of welding such as spot welding, arc welding, and laser welding, or joining means using an industrial adhesive may be applied.

[0030] Next, the joint structure 1 according to the first embodiment will be described in more detail with reference to Fig. 2. The joint structure 1 includes a cross frame 10 as a first member, a bracket 20 as a second member, and a bottom plate 30 as a third member.

[0031] The cross frame 10 has a top plate 11 and vertical walls 12. The top plate 11 extends in the vehicle width direction (Y direction). The vertical walls 12 extend from both ends of the top plate 11 in the vehicle length direction (X direction) toward the bottom plate 30, and the two vertical walls 12 facing each other so as to sandwich the top plate 11 extend in the vehicle width direction. The vertical walls 12 do not have to be formed perpendicular to the top plate 11, and the angle between the top plate 11 and the vertical walls 12 is, for example, 80 to 110 degrees. The configuration of the cross frame 10 will be described in detail later.

[0032] The bracket 20 is a member whose axial direction faces the vehicle width direction (Y direction) and whose cross section perpendicular to the axial direction is hat-shaped. The bracket 20 has a top plate 21, vertical walls 22, and flanges 23. The top plate 21 extends in the vehicle width direction, and the vertical walls 22 extend from both end portions of the top plate 21 in the vehicle length direction (X direction) toward the bottom plate 30. The flanges 23 are formed so as to open outward from each of the bottom plate 30-side end portions of the two opposing vertical walls 22. A through-hole 24 for attaching a suspension arm (not shown) is formed in the center of each of the two vertical walls 22.

[0033] The bottom plate 30 is a flat plate, and the lower end of the cross frame 10 and the flange 23 of the bracket 20 are joined to the upper surface of the bottom plate 30 .

[0034] Here, the configuration of the cross frame 10 will be described in more detail. Fig. 3 is a side view for explaining the schematic configuration of the joint structure 1 shown in Fig. 2. Fig. 4(A) is a diagram showing the AA cross section of Fig. 3, and Fig. 4(B) is a diagram showing the BB cross section of Fig. 3. The X direction, Y direction, and Z direction in each diagram are perpendicular to each other.

[0035] The cross frame 10 according to this embodiment has three regions, each having a vertical wall 12 with a different height from the top plate 11, namely, a first region (I), a second region (II), and a third region (III).

[0036] In this specification, the "height of the vertical wall" refers to the length of the vertical wall in the direction (Z direction) perpendicular to the table top 11 when viewed from the axial direction (Y direction) of the cross frame 10. For example, if the angle between the table top 11 and the vertical wall 12 is not perpendicular, the Z direction component of the length from the table top 11 to the tip of the vertical wall 12 is the height of the vertical wall.

[0037] As shown in FIG. 4(A), the first region (I) has a hat-shaped cross section perpendicular to the axial direction, and includes a first top plate 11a, two first vertical walls 12a, and two flanges 13.

[0038] The two first vertical walls 12a face each other with the first top plate 11a in between, and the height of the first vertical walls 12a from the first top plate 11a (i.e., the length from the first top plate 11a to the tip of the first vertical wall 12a in a direction perpendicular to the first top plate 11a) is a first height H1. Note that the first height H1 in the example of FIG. 1 can be rephrased as the length in the Z direction from the top plate 11 to the flange 13.

[0039] The flanges 13 extend outward from the lower ends of the two first vertical walls 12a. The two flanges 23 are joined to the bottom plate 30, thereby joining the cross frame 10 to the bottom plate 30. In other words, the first region (I) is a portion of the cross frame 10 that is joined to the bottom plate 30.

[0040] The second area (II) is an area located closer to the bracket 20 than the first area (I), and is located between the bracket 20 as the second member and the first area (I). As shown in Fig. 4(B), the second area (II) has a U-shaped cross section perpendicular to the axial direction that opens downward, and has a second top plate 11b and two second vertical walls 12b.

[0041] The two second vertical walls 12b face each other on either side of the second tabletop 11b, and the height of the second vertical walls 12b from the second tabletop 11b (i.e., the length from the second tabletop 11b to the tip of the second vertical walls 12b in a direction perpendicular to the second tabletop 11b) is the second height H2.

[0042] The distance between the two second vertical walls 12b is narrower than the distance between the two vertical walls 22 of the bracket 20, and the second vertical walls 12b are in contact with the vertical walls 22 on the inside of the bracket 20. In this state, the second vertical walls 12b and the vertical walls 22 are joined together, thereby joining the axial end of the cross frame 10 and the bracket 20.

[0043] On the other hand, the lower end of the second vertical wall 12b does not have a flange like the flange 23 of the first region (I), and a gap is left between the lower end of the second vertical wall 12b and the bottom plate 30. Therefore, as shown in FIG. 3, a space 40 is formed below the second region (II), and the second region (II) is not joined to the bottom plate 30.

[0044] As described above, the second region (II) is a region that is joined to the bracket 20 as the second member, but is not joined to the bottom plate 30 as the third member.

[0045] The third region (III) is located between the first region (I) and the second region (II) and includes a third top plate 11c and a third vertical wall 12c. The third top plate 11c is a wall connecting the first top plate 11a and the second top plate 11b, and the third vertical wall 12c is a wall connecting the first vertical wall 12a and the second vertical wall 12b. In the example of FIG. 3, a space 40 is formed below the third region (III), and the third region (III) is not joined to the bottom plate 30.

[0046] As described above, the cross frame 10 has the first region (I) to the third region (III), the top plate 11 is made up of the first top plate 11a, the second top plate 11b, and the third top plate 11c, and the vertical walls 12 are made up of the first vertical wall 12a, the second vertical wall 12b, and the third vertical wall 12c. In other words, the first top plate 11a, the second top plate 11b, and the third top plate 11c are each part of the top plate 11, and the first vertical wall 12a, the second vertical wall 12b, and the third vertical wall 12c are each part of the vertical walls 12.

[0047] In the first embodiment, the height from the bottom plate 30 to the first top plate 11a is lower than the height from the bottom plate 30 to the second top plate 11b, and the first top plate 11a is located closer to the bottom plate 30 (negative side in the Z direction) as a third member than the second top plate 11b. A third top plate 11c in a third region (III) connecting the first top plate 11a and the second top plate 11b is inclined with respect to the first top plate 11a. Furthermore, a height H2 of the second vertical wall 12b is lower than a height H1 of the first vertical wall 12a. When the joint structure 1 is applied to a subframe of an automobile, the difference in height between the first top plate 11a and the second top plate 11b is, for example, 20 to 100 mm.

[0048] 5, the height from the bottom plate 30 to the top plate (second top plate 11b) in the second region (II) is defined as H0. In the cross frame 10 according to the first embodiment, the second vertical wall 12b is formed so that the ratio (H2 / H0) of the second height H2 to the top plate height H0 is within a range of 0.4 to 0.8.

[0049] As will be shown in the examples described later, the joint structure 1 of the first embodiment, in which H2 / H0 satisfies 0.4 to 0.8, can achieve weight reduction while suppressing an excessive decrease in rigidity per unit weight against lateral force input to the second member (in this embodiment, force in the vehicle width direction input to bracket 20).

[0050] For example, a structure in which H2 / H0 is 1.0 corresponds to the conventional joint structure 100 shown in Fig. 6, but when H2 / H0 is less than 0.4, the reduction in rigidity per unit weight is significant compared to the conventional joint structure 100, and the reduction in rigidity due to weight reduction is significant. On the other hand, when H2 / H0 exceeds 0.8, the effect of improving rigidity per unit weight is small, so increasing the height H2 of the second vertical wall 12b so that H2 / H0 exceeds 0.8 is not an advantageous structure from the viewpoint of improving rigidity per unit weight.

[0051] That is, the joint structure 1 according to the first embodiment, in which H2 / H0 satisfies 0.4 to 0.8 and the space 40 is provided below the second region (II), is a structure that can obtain a weight reduction effect and can suppress an excessive decrease in rigidity per unit weight. Note that, from the viewpoint of ensuring the same level of rigidity per unit weight as the conventional structure in which H2 / H0 is 1.0, H2 / H0 is preferably 0.5 or more, and more preferably 0.6 or more.

[0052] Furthermore, in the inclined third region (III) connecting the first region (I) and the second region (II), when at least a portion thereof is formed linearly, the angle θ between the axial direction C3 of the linear portion and the axial direction C1 of the first region (I) is preferably 25° or less. As will be shown in the examples described later, when the angle θ is 25° or less, the rigidity per unit weight is improved. To enhance this effect, the angle θ is preferably 20° or less, and more preferably 15° or less. Note that, since the third region (III) is inclined with respect to the first region (I), the angle θ is necessarily greater than 0°.

[0053] The joint structure 1 according to the first embodiment has been described above. According to the joint structure 1 according to the first embodiment, the second region (II) of the cross frame 10 is provided so that H2 / H0 falls within the range of 0.4 to 0.8, thereby achieving weight reduction and preventing an excessive decrease in rigidity per unit weight.

[0054] Furthermore, in the joint structure 1, the space 40 is formed between the second region (II) of the cross frame 10 and the bottom plate 30, which improves the degree of freedom in designing the vehicle body. For example, it becomes possible to design a vehicle body structure that could not be realized with conventional technology, such as providing another member (not shown) extending in the vehicle length direction (X direction) in the space 40.

[0055] The cross frame 10 as the first member in the first embodiment is manufactured by pressing a metal plate using the method for manufacturing curved parts disclosed in Japanese Patent No. 5733475 so that no flange is formed in the second region (II).

[0056] In addition, the height of the top plate 11 from the third member (bottom plate 30 in this embodiment) or the axial length of the first region (I) and the second region (II) are appropriately set depending on the size of the design space around the application location of the joint structure and the performance required of the structure including the joint structure.

[0057] Second Embodiment Next, a joint structure 1 according to a second embodiment will be described. Fig. 7 is a perspective view for explaining a schematic configuration of the joint structure 1 according to this embodiment. Fig. 8 is a side view for explaining a schematic configuration of the joint structure 1.

[0058] The joint structure 1 according to the second embodiment differs from the first embodiment in that the height from the bottom plate 30 to the first top plate 11a, the height from the second top plate 11b, and the height from the third top plate 11c are all the same, and the top plates 11a to 11c are all in the same plane. In the following description, content that overlaps with the description of the first embodiment may be omitted.

[0059] In the joint structure 1 in which the first to third top plates 11a to 11c extend in the same plane, the second vertical wall 12b is formed so that H2 / H0 is in the range of 0.3 to 0.8. With this joint structure 1, as will be shown in the examples described later, it is possible to suppress an excessive decrease in rigidity per unit weight against a lateral force input to the second member (in this embodiment, a force in the vehicle width direction input to the bracket 20) while achieving a weight reduction.

[0060] For example, a structure in which H2 / H0 is 1.0 corresponds to the conventional joint structure 101 shown in Fig. 9, but when H2 / H0 is less than 0.3, the reduction in rigidity per unit weight is significant compared to the conventional joint structure 101, and the reduction in rigidity due to weight reduction is significant. On the other hand, when H2 / H0 exceeds 0.8, the effect of improving rigidity per unit weight is small, so increasing the height H2 of the second vertical wall 12b so that H2 / H0 exceeds 0.8 is not an advantageous structure from the viewpoint of improving rigidity per unit weight.

[0061] That is, the joint structure 1 according to the second embodiment, in which H2 / H0 satisfies 0.3 to 0.8 and has the space 40 below the second region (II), is a structure that can obtain a weight reduction effect and can suppress an excessive decrease in rigidity per unit weight. Note that, from the viewpoint of ensuring the same level of rigidity per unit weight as the conventional structure in which H2 / H0 is 1.0, H2 / H0 is preferably 0.4 or more, and more preferably 0.5 or more.

[0062] The joint structure 1 according to the second embodiment has been described above. In the joint structure 1, the first region (I) and the second region (II) may be adjacent to each other without providing the third region (III).

[0063] Furthermore, although the joint structure 1 according to the second embodiment is intended for application to an automobile subframe, the application of the joint structure according to the present disclosure is not limited to automobile subframes and can also be applied to locations where parts are joined in a T-shape. However, in a joint structure in which the first top panel 11a to the third top panel 11c extend in the same plane as in the second embodiment, at least the second member among the first, second, and third members is not an automobile frame member. The automobile frame members referred to here are members used as the frame of the vehicle body, such as a front bumper beam, a rear bumper beam, front side members, rear side members, side sills, floor cross members, roof side rails, roof cross members, center pillars, and side rails and cross members that constitute a ladder frame.

[0064] While one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the technical ideas set forth in the claims, and it is understood that such modifications also fall within the technical scope of the present invention.

[0065] For example, the components of the above-described embodiments can be combined in any manner, and such combinations will naturally provide the functions and advantages of each of the components in the combination, as well as other functions and advantages that will be apparent to those skilled in the art from the description herein.

[0066] Furthermore, the effects described herein are merely descriptive or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that are apparent to those skilled in the art from the description of this specification, in addition to or in place of the above-described effects. [Example]

[0067] <Simulation (1)> A simulation was carried out to evaluate the rigidity of the analytical model of the joint structure 1 shown in Figures 2 to 5. In this simulation, as shown in Figure 10, the through hole 24 of the bracket 20 was used as a restraint point, and the rigidity was evaluated by applying a load F parallel to the vehicle width direction from the through hole 24 toward the cross frame 10. This load F is assumed to be a lateral force from the wheel via a suspension arm (not shown). In this simulation, the angle θ between the axial direction C1 of the first region (I) and the axial direction C3 of the third region (III) shown in Figure 5 was set to 30°.

[0068] In simulation (1), multiple simulations were performed using a model in which the height (second height H2) of the second vertical wall 12b of the cross frame 10 was varied. The results are shown in FIG.

[0069] As shown in Figure 11, when H2 / H0 is less than 0.4, the weight efficiency of stiffness (stiffness per unit weight) falls to less than 75% compared to the conventional structure with H2 / H0 of 1.0, resulting in an excessive decrease in stiffness. On the other hand, when H2 / H0 exceeds 0.8, the effect of improving stiffness per unit weight is small. For this reason, a joint structure with an H2 / H0 ratio of 0.4 to 0.8 can be said to be a structure in which the decrease in stiffness per unit weight is suppressed while achieving weight reduction.

[0070] <Simulation (2)> Next, in the joint structure 1 shown in Figure 5, multiple simulations were performed using a model in which the height (second height H2) of the second vertical wall 12b was fixed at 30 mm and the angle θ was varied by adjusting the axial length (Y-direction length) of the first region portion (I). The results are shown in Figure 12. The constraint conditions and load input position of the analytical model were the same as those in simulation (1).

[0071] As shown in FIG. 12, if the angle θ is 25° or less, the rigidity per unit weight is improved, and a joint structure with an excellent balance between lightweight and rigidity can be obtained.

[0072] <Simulation (3)> Next, a simulation was performed to evaluate the rigidity of the analytical model of the joint structure 1 shown in Figures 7 and 8. In this simulation, as shown in Figure 13, the through hole 24 of the bracket 20 was used as a restraint point, and a load F was applied parallel to the vehicle width direction from the through hole 24 toward the cross frame 10 to evaluate the rigidity. This load F is an assumed lateral force from the wheel via a suspension arm (not shown).

[0073] In simulation (3), a plurality of simulations were performed using a model in which the height (second height H2) of the second vertical wall 12b of the cross frame 10 was varied. The results are shown in FIG.

[0074] As shown in Figure 14, if H2 / H0 is within the range of 0.3 to 0.8, it is possible to ensure the same level of weight efficiency (rigidity per unit weight) of rigidity as a conventional structure with H2 / H0 of 1.0. In other words, a joint structure with H2 / H0 of 0.3 to 0.8 can be said to be a structure that can suppress the decrease in rigidity per unit weight that comes with weight reduction. [Explanation of symbols]

[0075] 1 Joint structure 10 Cross Frame 11 Top plate 11a First top plate 11b Second top plate 11c Third top 12 Vertical Wall 12a First vertical wall 12b Second vertical wall 12c Third vertical wall 13 Flange 20 Bracket 21 Top plate 22 Vertical Wall 23 flange 24 through holes 30 Bottom plate 40 space 90 subframe 91 Side frame 100 Conventional joint structure 101 Conventional joint structure (I) First area (II) Second area (III) Third area C1 Axial direction of the first region C3 Axial direction of the third region H0 Height from the bottom plate to the top plate in the second area H1 First height H2 Second height

Claims

1. A joint structure for an automobile subframe, comprising: a first member having a top plate and a vertical wall; a second member joined to an axial end of the first member; a third member joined to each of the first member and the second member, the vertical wall extends from the top plate toward the third member, The first member is A first region portion; a second region located between the first region and the second member; a third region located between the first region and the second region, The first region is A first top plate that is a part of the top plate; a first vertical wall having a first height from the first top plate; the first region is joined to the third member, The second region is A second top plate that is a part of the top plate; a second vertical wall having a second height from the second top plate; the second region is joined to the second member and is not joined to the third member, a space exists between the second vertical wall and the third member, The third region is A third top plate that is a part of the top plate; a third vertical wall connecting the first vertical wall and the second vertical wall, The height of the first tabletop is lower than the height of the second tabletop, A joint structure, wherein the ratio of the second height to the height from the third member to the second top plate in the second region is 0.4 to 0.

8.

2. At least a portion of the third region is formed linearly, 2. The joint structure according to claim 1, wherein an angle formed between an axial direction of the first region and an axial direction of the third region is 25 degrees or less.

3. A joint structure for an automobile subframe, comprising: a first member having a top plate and a vertical wall; a second member joined to an axial end of the first member; a third member joined to each of the first member and the second member, the vertical wall extends from the top plate toward the third member, The first member is A first region portion; a second region located between the first region and the second member, The first region is A first top plate that is a part of the top plate; a first vertical wall having a first height from the first top plate; the first region is joined to the third member, The second region is A second top plate that is a part of the top plate; a second vertical wall having a second height from the second top plate; the second region is joined to the second member and is not joined to the third member, a space exists between the second vertical wall and the third member, the first top plate and the second top plate are in the same plane; A joint structure, wherein the ratio of the second height to the height from the third member to the top plate in the second region is 0.3 to 0.

8.

4. the first member has a third region located between the first region and the second region, The joint structure according to claim 3 , wherein the third region has a third vertical wall connecting the first vertical wall and the second vertical wall.

Images