WO2024225295A1

WO2024225295A1 - Joint structure

Info

Publication number: WO2024225295A1
Application number: PCT/JP2024/016015
Authority: WO
Inventors: 奈沙島崎; 毅河内; 功作石原
Original assignee: 日本製鉄株式会社
Priority date: 2023-04-24
Filing date: 2024-04-24
Publication date: 2024-10-31

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

Joint Structure

The present invention relates to a joint structure.

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

For this reason, in order to meet the demand for weight reduction while suppressing the decline in vehicle body rigidity, it is necessary to improve the shape of each part and the joining structure between parts. Note that in this specification, the structure around the joints where multiple parts are joined together is sometimes referred to as the "joint structure."

As a vehicle body structure including a joint structure, Patent Document 1 discloses a vehicle underbody structure that includes a pair of rockers extending in the vehicle longitudinal direction and a floor cross member with 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.

Patent document 2 discloses an automobile lower body structure that includes a floor panel that constitutes the passenger compartment floor, side sills that extend 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.

Patent Document 3 discloses a vehicle body frame structure 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.

Patent document 4 discloses a mounting structure for a suspension upper arm that includes a suspension upper arm support bracket that connects an apron upper member and a front side member with a closed cross-sectional structure.

Patent document 5 discloses a reinforcement structure for an automobile floor panel in which a cross member is arranged in the vehicle width direction of a floor panel that has a tunnel section in the fore-and-aft direction of the vehicle body, a tunnel reinforcement member is crossed so as to straddle the cross member, and a seat mounting section is provided on the cross member.

Patent document 6 discloses a front body structure for an automobile that includes front side members that are disposed 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 disposed between the left and right front pillars and extends in the width direction.

Japanese Patent No. 6264864 Japanese Patent Application Publication No. Hei 4 (1992)-303076 Japanese Patent Application Publication No. 2004-322776 Japanese Utility Model Application Publication No. Hei 3 (1991)-040171 Japanese Patent Application Publication No. 2004-352080 Japanese Patent Application Publication No. 2000-153779

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

From the perspective of achieving both weight reduction and rigidity, a structure in which the rigidity per unit weight is excessively reduced as a result of weight reduction is undesirable. In other words, it is desirable to create a joint structure that can reduce weight while preventing 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 issue of reducing weight in a joint structure while preventing an excessive decrease in rigidity per unit weight can also arise in structures other than automobiles.

The present invention was made in consideration of the above circumstances, and aims to provide a joint structure that is lightweight while preventing an excessive decrease in rigidity per unit weight.

The 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 that includes 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 preventing an excessive decrease in rigidity per unit weight, and thus came up with the present invention.

One aspect of the present invention that solves the above-mentioned problems is a 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, the vertical wall extending from the top plate towards the third member, the first member having 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, the first region having a first vertical wall that is a first height from the first top plate, The second region has a second top plate that is a part of the top plate and a second vertical wall whose height from the second top plate is 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 that connects 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.

Another aspect of the present invention is a joint structure comprising a first member having a top plate and a vertical wall, a second member that is not an automobile frame member and is joined to an axial end of the first member, and a third member joined to each of the first member and the second member, the vertical wall extending from the top plate toward the third member, the first member having a first region and a second region located between the first region and the second member, the first region comprising 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 has a second top plate that is a part of the top plate and a second vertical wall whose height from the second top plate is 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 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 region is 0.3 to 0.8.

The present invention provides a joint structure that is lightweight while preventing excessive loss of rigidity per unit weight.

FIG. 2 is a perspective view for explaining an application location of a joint structure according to one embodiment of the present invention. FIG. 1 is a perspective view for explaining a schematic configuration of a joint structure according to a first embodiment. FIG. 2 is a side view for explaining a schematic configuration of a joint structure. 4A and 4B are views showing cross sections AA and BB in FIG. 3. FIG. 11 is a side view for explaining the definition of H ₂ /H ₀ . FIG. 1 is a side view showing a conventional joint structure in which H ₂ /H ₀ is 1.0. FIG. 11 is a perspective view for explaining a schematic configuration of a joint structure according to a second embodiment. FIG. 2 is a side view for explaining a schematic configuration of a joint structure. FIG. 1 is a side view showing a conventional joint structure in which H ₂ /H ₀ is 1.0. FIG. 11 is a side view of a joint structure for explaining simulation conditions. 1 is a graph showing the results of simulation (1). 13 is a graph showing the results of simulation (2). FIG. 11 is a side view of a joint structure for explaining simulation conditions. 13 is a graph showing the results of simulation (3).

Below, an embodiment of the present invention will be described with reference to the drawings. Note that in this specification and the drawings, elements having substantially the same functional configuration will be given the same reference numerals to avoid redundant description.

First Embodiment
(Applicable locations 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 parallel-cross 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.

The joint structure 1 in the application example of Figure 1 comprises 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 the 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, the 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 the side surface of the axial end of the cross frame 10.

Note that the cross-shaped subframe 90 in the example of Figure 1 has a pair of cross frames that extend parallel to each other and a pair of side frames that extend parallel to each other, but Figure 1 only illustrates one of the pair of cross frames, cross frame 10, and one of the pair of side frames, side frame 91, with the other cross frame and side frame not illustrated. In addition, 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.

Furthermore, the application of the joint structure according to the present disclosure is not limited to the subframe of an automobile, but may also be applied to the places where parts are joined in a T-shape. For example, at least any of the first member, second member, and third member included in the joint structure may not be an automobile skeletal member like the subframe 90 described above, or may be an automobile skeletal member. The automobile skeletal members mentioned here are members used as the skeleton of the vehicle body, such as the front bumper beam, rear bumper beam, front side member, rear side member, side sill, floor cross member, roof side rail, roof cross member, center pillar, side rails and cross members that make up a ladder frame, etc.

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 lower body structure of an automobile. In that 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. In addition, 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 upper body structure of an automobile. In that 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.

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

The second member may not be a single part, but may be a part 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 being a plate extending in the same plane, but may have a step, inclination, etc.

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. are used. Also, when the joint structure is applied to an automobile body and the material of the first to third members is steel, for example, steel with a tensile strength of 440 MPa or more, 590 MPa or more, or 780 MPa or more is used.

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. In addition, 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.

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

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.

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 on either side of 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. A detailed explanation of the configuration of the cross frame 10 will be given later.

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 ends of the top plate 21 in the vehicle length direction (X direction) toward the bottom plate 30. The flanges 23 are formed by opening outward from each of the bottom plate 30 side ends of the two opposing vertical walls 22. A through hole 24 is formed in the center of each of the two vertical walls 22 for attaching a suspension arm (not shown).

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.

Here, the configuration of the cross frame 10 will be described in more detail. Figure 3 is a side view for explaining the general configuration of the joint structure 1 shown in Figure 2. Figure 4(A) is a diagram showing the A-A cross section of Figure 3, and Figure 4(B) is a diagram showing the B-B cross section of Figure 3. The X, Y, and Z directions in each figure are perpendicular to each other.

The cross frame 10 according to this embodiment has three areas, each with a different height of the vertical wall 12 from the top plate 11: a first area (I), a second area (II), and a third area (III).

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

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

The two first vertical walls 12a face each other so as to sandwich the first top plate 11a, and the height of the first vertical wall 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 H _{1. Note that the first height H 1} 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.

The flanges 13 extend outward from each of 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 the portion of the cross frame 10 that is joined to the bottom plate 30.

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.

The two second vertical walls 12b face each other on either side of the second top plate 11b, and the height of the second vertical walls 12b from the second top plate 11b (i.e., the length from the second top plate 11b to the tip of the second vertical wall 12b in a direction perpendicular to the second top plate 11b) is a second height _H2 .

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.

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 area (I), and there is a gap 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 area (II), and the second area (II) is not joined to the bottom plate 30.

As described above, the second area (II) is joined to the bracket 20 as the second member, but is not joined to the bottom plate 30 as the third member.

The third region (III) is located between the first region (I) and the second region (II) and has a third top plate 11c and a third vertical wall 12c. The third top plate 11c is a wall portion connecting the first top plate 11a and the second top plate 11b, and the third vertical wall 12c is a wall portion 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.

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

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 the third member than the second top plate 11b. The third top plate 11c in the 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. In addition, the height _H2 of the second vertical wall 12b is lower than the 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.

5, the height from the bottom plate 30 to the top plate (second top plate 11b) in the second region (II) is defined as H _0. In the cross frame 10 according to the first embodiment, the second vertical wall 12b is formed so that the ratio (H ₂ /H ₀ ) of the second height H ₂ to the top plate height H ₀ is within the range of 0.4 to 0.8.

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, while achieving weight reduction, can suppress an excessive decrease in rigidity per unit weight against the lateral force input to the second member (in this embodiment, the force in the vehicle width direction input to the bracket 20).

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 decrease in rigidity per unit weight is significant compared to the conventional joint structure 100, and the decrease in rigidity due to weight reduction is large. 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 in terms of improving rigidity per unit weight.

That is, the joint structure 1 according to the first embodiment, in which _H2 / _H0 satisfies 0.4 to 0.8 and has the space 40 below the second region (II), is a structure that can obtain a weight reduction effect and suppress an excessive decrease in rigidity per unit weight. 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.

In addition, in the inclined third region (III) connecting the first region (I) and the second region (II), when at least a part of the third region (III) is formed in a straight line, the angle θ between the axial direction _C3 in the straight line portion and the axial direction _C1 of the first region (I) is preferably 25° or less. As shown in the examples described later, when the angle θ is 25° or less, the rigidity per unit weight is improved. In terms of enhancing this effect, the angle θ is preferably 20° or less, 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 an angle greater than 0°.

The above describes the joint structure 1 according to the first embodiment. 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 making it possible to reduce the weight while suppressing an excessive decrease in rigidity per unit weight.

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

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

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 area (I) and the second area (II) are appropriately set according to the size of the design space around the application point of the joint structure and the performance required of the structure including the joint structure, etc.

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.

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 on the same plane. Note that in the following explanation, content that overlaps with the explanation of the first embodiment may be omitted.

In the joint structure 1 in which the first top plate 11a to the third top plate 11c extend in the same plane, the second vertical wall 12b is formed so that _H2 / _H0 is within a range of 0.3 to 0.8. With such a joint structure 1, as 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 realizing a weight reduction.

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 decrease in rigidity per unit weight is significant compared to the conventional joint structure 101, and the decrease in rigidity due to weight reduction is large. 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 in terms of improving rigidity per unit weight.

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 suppress an excessive decrease in rigidity per unit weight. 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.

The above describes the joint structure 1 according to the second embodiment. Note that 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).

The joint structure 1 according to the second embodiment is intended to be applied to an automobile subframe, but the application of the joint structure according to the present disclosure is not limited to an automobile subframe, and may also be applied to a location where parts are joined in a T-shape. However, in a joint structure in which the first top plate 11a to the third top plate 11c extend in the same plane as in the second embodiment, at least the second member among the first member, second member, and third member is not an automobile skeleton member. The automobile skeleton members referred to here are members used as the skeleton of the vehicle body, such as the front bumper beam, rear bumper beam, front side member, rear side member, side sill, floor cross member, roof side rail, roof cross member, center pillar, and side rails and cross members that make up a ladder frame.

The above describes one example of an embodiment of the present invention, but the present invention is not limited to this example. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

For example, the components of the above embodiments can be combined in any manner. Any such combination will naturally provide the actions and effects of each of the components in the combination, and will also provide other actions and effects that will be apparent to those skilled in the art from the description in this specification.

Furthermore, the effects described in this specification are merely descriptive or exemplary and are not limiting. In other words, the technology disclosed herein may achieve other effects that are apparent to a person skilled in the art from the description in this specification, in addition to or in place of the above effects.

<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 a load F parallel to the vehicle width direction was applied from the through hole 24 toward the cross frame 10 side to evaluate the rigidity. 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°.

In the simulation (1), a number of simulations were performed using a model in which the height (second height H ₂ ) of the second vertical wall 12b of the cross frame 10 was varied. The results are shown in FIG.

As shown in Fig. 11, when _H2 / _H0 is less than 0.4, the weight efficiency of rigidity (rigidity per unit weight) falls to less than 75% compared to the conventional structure with _H2 / _H0 of 1.0, and rigidity is excessively reduced. On the other hand, when _H2 / _H0 exceeds 0.8, the effect of improving rigidity per unit weight is small. Therefore, a joint structure with _H2 / _H0 of 0.4 to 0.8 can be said to be a structure in which the reduction in rigidity per unit weight is suppressed while achieving weight reduction.

<Simulation (2)>
Next, in the joint structure 1 shown in Fig. 5, a simulation was performed multiple times 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 Fig. 12. The constraint conditions and the load input position of the analysis model were the same as those in simulation (1).

As shown in Figure 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.

<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 assumed to be a lateral force from the wheel via a suspension arm (not shown).

In the simulation (3), a number of simulations were performed using a model in which the height (second height H ₂ ) of the second vertical wall 12b of the cross frame 10 was varied. The results are shown in FIG.

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 the conventional structure with _H2 / _H0 of 1.0. In other words, a joint structure with _H2 / _H0 of 0.3 to 0.8 is a structure that can suppress the decrease in rigidity per unit weight that accompanies weight reduction.

1 Joint structure 10 Cross frame 11 Top plate 11a First top plate 11b Second top plate 11c Third top plate 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 hole 30 Bottom plate 40 Space 90 Subframe 91 Side frame 100 Conventional joint structure 101 Conventional joint structure (I) First region (II) Second region (III) Third region C ₁ Axial direction C of first region ₃ Axial direction _H of third region ₀ Height H from bottom plate to top _plate in second region

Claims

A joint structure,
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 area 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 which 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 a ratio of the second height to a height from the third member to the second top plate in the second region is 0.4 to 0.8.
The third region is at least partially formed in a linear shape,
2. The joint structure according to claim 1, wherein an angle between an axial direction of the first region and an axial direction of the third region is 25 degrees or less.
A joint structure,
A first member having a top plate and a vertical wall;
A second member that is not an automobile frame member and is 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 area 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 a ratio of the second height to a height from the third member to the top plate in the second region is 0.3 to 0.8.
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.
The joint structure according to any one of claims 1 to 4, characterized in that it is used in a subframe of an automobile.