Automobile frame structure

Abstract

This frame structure includes: a first member composed of a metal material having a tensile strength of at least 780 MPa; and a second member composed of a metal material and disposed further toward the inside of the vehicle than the first member. The first member has a side wall constituting a wall part on the outside of the vehicle, and a stepped wall part extending from the side wall to the inside of the vehicle. The plate thickness of the first member is at least 2.3 mm. The step height h of the stepped wall part and the cross-sectional height h0 of the first member satisfy 0.01 ≤ h / h0 ≤ 0.15. The step width w of the stepped wall part and the cross-sectional width w0 of the first member satisfy 0.01 ≤ w / w0 ≤ 0.60.

Description

Automobile frame structure

[0001] The present invention relates to a frame structure of an automobile.

[0002] The bodies of automobiles such as SUVs and trucks employ a body-on-frame structure, which has a ladder-shaped frame called a ladder frame at the bottom of the vehicle body. Patent Document 1 discloses a vehicle ladder frame that can reduce lateral bending stress generated at specific locations on the side rails. Patent Document 2 also discloses a strength member for an automobile formed by drawing or hydroforming, which can be used as a framework member for a monocoque body.

[0003] Japanese Patent Application Publication No. 2004-243984 Japanese Patent Application Publication No. 2002-284033

[0004] With the recent trend toward electrification of automobiles, developments to accommodate electrification are also required for frame-structure vehicles equipped with ladder frames. Specifically, from the perspective of further improving battery protection performance, a structure that can further suppress deformation of the ladder frame into the vehicle body during a collision is required. Furthermore, even for automobiles that do not have a battery installed under the floor, a frame structure with excellent collision performance that can suppress deformation into the vehicle body is required from the perspective of further improving occupant protection performance. At the same time, from the perspective of reducing environmental impact, vehicle weight reduction is also required. In other words, in order to achieve both weight reduction and collision performance, it is desirable to develop a ladder frame that improves collision performance without substantially increasing weight. Furthermore, achieving both weight reduction and collision performance is a common challenge not only for ladder frames but also for the framework components of monocoque bodies.

[0005] The present invention has been made in view of the above circumstances, and has as its object to provide a frame structure that has excellent collision performance without substantially increasing weight.

[0006] One aspect of the present invention that solves the above-mentioned problems is a frame structure for an automobile, comprising: a first member made of a metal material having a tensile strength of 780 MPa or more; a second member made of a metal material and arranged on the vehicle interior side of the first member; and a hollow portion formed by the first member and the second member and extending in an axial direction of the frame structure, wherein the first member has a side wall that constitutes a wall portion on the vehicle exterior side of the hollow portion; a stepped wall portion extending from the side wall to the vehicle interior side; and an edge extending in the axial direction that connects the side wall and the stepped wall portion. the stepped wall portion has a first wall portion joined to the second member and extending parallel to the joining surface with the second member, and a second wall portion located more inward of the hollow portion than the first wall portion and connected to the ridge portion, the thickness of the first member is 2.3 mm or more, a step height h of the stepped wall portion and a cross-sectional height h0 of the first member satisfy 0.01≦h / h0≦0.15, and a step width w of the stepped wall portion and a cross-sectional width w0 of the first member satisfy 0.01≦w / w0≦0.60.

[0007] Another aspect of the present invention is a frame structure for an automobile, comprising: a first member made of a metal material having a tensile strength of 780 MPa or more; a second member made of a metal material and arranged on the vehicle interior side of the first member; and a hollow portion formed by the first member and the second member and extending in an axial direction of the frame structure, wherein the first member comprises a side wall constituting a wall portion on the vehicle exterior side of the hollow portion; a stepped wall portion extending from the side wall toward the vehicle interior side; and a ridge portion extending in the axial direction connecting the side wall and the stepped wall portion. the stepped wall portion has a first wall portion joined to the second member and extending parallel to a joining surface with the second member, and a second wall portion located more inward of the hollow portion than the first wall portion and connected to the ridge portion, the plate thickness of the first member is 2.0 mm or more and less than 2.3 mm, a step height h of the stepped wall portion and a cross-sectional height h0 of the first member satisfy 0.01≦h / h0≦0.22, and a step width w of the stepped wall portion and a cross-sectional width w0 of the first member satisfy 0.01≦w / w0≦0.63.

[0008] According to yet another aspect of the present invention, there is provided a frame structure for an automobile, the frame structure comprising: a first member made of a metal material having a tensile strength of 780 MPa or more; a second member made of a metal material and arranged on the vehicle interior side of the first member; and a hollow portion formed by the first member and the second member and extending in an axial direction of the frame structure, wherein the first member has a side wall constituting a wall portion on the vehicle exterior side of the hollow portion; a stepped wall portion extending from the side wall to the vehicle interior side; and a ridge portion extending in the axial direction connecting the side wall and the stepped wall portion. the stepped wall portion has a first wall portion joined to the second member and extending parallel to the joining surface with the second member, and a second wall portion located more inward of the hollow portion than the first wall portion and connected to the ridge portion, the plate thickness of the first member is 0.8 mm or more and less than 2.0 mm, a step height h of the stepped wall portion and a cross-sectional height h0 of the first member satisfy 0.01≦h / h0≦0.30, and a step width w of the stepped wall portion and a cross-sectional width w0 of the first member satisfy 0.01≦w / w0≦0.65.

[0009] It is possible to provide a frame structure with excellent collision performance without substantially increasing the weight.

[0010] 1 is a diagram showing an example of a ladder frame to which the frame structure according to the first embodiment is applied. FIG. 1 is a cross-sectional view illustrating the schematic configuration of a side rail as the frame structure according to the first embodiment. FIG. 2 is a diagram illustrating the definitions of the step height h, cross-sectional height h0, step width w, and cross-sectional width w0 of a stepped wall portion. FIG. 3 is a diagram illustrating the schematic configuration of a press forming apparatus for illustrating an example of a manufacturing method for an outer panel having a stepped wall portion. FIG. 4 is a diagram illustrating an example of a side frame as the frame structure according to the second embodiment, attached to a battery case. FIG. 5 is a cross-sectional view illustrating the schematic configuration of a side frame as the frame structure according to the second embodiment. FIG. 6 is a diagram illustrating an example of the structure of a side frame. FIG. 7 is a diagram illustrating an analytical model of a three-point bending simulation assuming a pole side collision. FIG. 8 is a diagram illustrating the definition of the intrusion amount of the frame structure into the vehicle body during a pole collision. FIG. 9 is a diagram illustrating the relationship between the step height h / cross-sectional height h0 and the intrusion amount. FIG. 10 is a diagram illustrating the relationship between the step width w / cross-sectional width w0 and the intrusion amount. FIG. 11 is a diagram illustrating a schematic view of a model without a stepped wall portion during a pole collision. FIG. 12 is a diagram illustrating a schematic view of a model with a stepped wall portion during a pole collision.

[0011] 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.

[0012] <First embodiment> Fig. 1 is a diagram showing an example of a ladder frame to which a frame structure according to a first embodiment is applied. In the drawings referred to in this embodiment and a second embodiment described later, 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 (vertical direction), and the X direction, Y direction, and Z direction are directions perpendicular to one another. In the frame structure according to this embodiment and a second embodiment described later, the X direction can also be referred to as the axial direction of the frame structure.

[0013] As shown in Figure 1, the ladder frame 1 includes two side rails 10, 11 extending in the vehicle length direction (X direction) and multiple cross members 12 extending in the vehicle width direction (Y direction). The two side rails 10, 11 are spaced apart in the vehicle width direction. The multiple cross members 12 are spaced apart in the vehicle length direction between the two side rails 10, 11 and joined to each of the side rails 10, 11.

[0014] The frame structure according to the present invention is applied to, for example, the above-mentioned side rails 10, 11. Next, the schematic configuration of the side rail 10 as a frame structure will be described with reference to Fig. 2. Fig. 2 corresponds to the cross section A-A in Fig. 1 and shows a cross section of the side rail 10 perpendicular to the vehicle length direction (X direction).

[0015] The side rail 10 has an outer panel 20 as a first member, an inner panel 30 as a second member arranged on the vehicle widthwise inward side (negative side in the Y direction) of the outer panel 20, and a hollow portion 40 extending in the vehicle length direction (X direction) formed by the outer panel 20 and the inner panel 30. The side rail 10 is located to the side of the battery case 50, and the side rail 10 protects the battery case 50 in the event of a side collision of the vehicle.

[0016] The outer panel 20 has side walls 21 extending in the X-Z plane and constituting the wall portion of the hollow portion 40 on the outer side in the vehicle width direction (positive side in the Y direction), a bottom wall 22 extending from the lower end of the side wall 21 toward the inner side in the vehicle width direction (negative side in the Y direction), and a top wall 23 extending from the upper end of the side wall 21 toward the inner side in the vehicle width direction. These side walls 21, bottom wall 22, and top wall 23 are formed, for example, by pressing a single steel plate, thereby forming a ridge line portion 24a between the lower end of the side wall 21 and the bottom wall 22, and a ridge line portion 25a between the upper end of the side wall 21 and the top wall 23. In other words, the outer panel 20 has a ridge line portion 24a connecting the side wall 21 and the bottom wall 22, and a ridge line portion 25a connecting the side wall 21 and the top wall 23. These ridge lines 24a, 25a extend along the axial direction (X direction) of the outer panel 20.

[0017] The outer panel 20, which includes the side walls 21, bottom wall 22, top wall 23, and ridges 24a and 25a, is a member having a generally U-shaped cross section, not a hat-shaped cross section. That is, no flange extends downward from the bottom wall 22 or upward from the top wall 23.

[0018] The bottom wall 22 has a first wall portion 22 a joined to the inner panel 30 and a second wall portion 22 b positioned between the first wall portion 22 a and the side wall 21 .

[0019] The first wall portion 22a of the bottom wall 22 is a wall portion that extends within one plane (within the X-Y plane in this embodiment), and the plane on which the first wall portion 22a extends is a plane parallel to the joint surface between the inner panel 30 and the first wall portion 22a. In other words, the first wall portion 22a is a wall portion that extends parallel to the joint surface with the inner panel 30.

[0020] The second wall portion 22b of the bottom wall 22 is located further inward (upper in the example of FIG. 2 ) in the hollow portion 40 than the first wall portion 22a, and is connected to the lower end of the side wall 21 via the aforementioned ridge portion 24a. The first wall portion 22a and the second wall portion 22b are formed by, for example, pressing a steel plate, and ridge portions 24b, 24c are formed between the first wall portion 22a and the second wall portion 22b, extending in the axial direction (X direction) of the outer panel 20.

[0021] The first wall portion 22 a and the second wall portion 22 b are connected to each other via these ridge portions 24 b, 24 c, and the bottom wall 22 is configured as a wall portion in which a step is formed by the first wall portion 22 a and the second wall portion 22 b. In this specification, a wall portion having such a step is referred to as a “stepped wall portion.”

[0022] The top wall 23 is a stepped wall portion similar to the bottom wall 22. The top wall 23 has a first wall portion 23a joined to the inner panel 30 and a second wall portion 23b located between the first wall portion 23a and the side wall 21.

[0023] The first wall portion 23a of the top wall 23 is a wall portion that extends within one plane (within the X-Y plane in this embodiment), and the plane on which the first wall portion 23a extends is a plane parallel to the joint surface between the inner panel 30 and the first wall portion 23a. In other words, the first wall portion 23a is a wall portion that extends parallel to the joint surface with the inner panel 30.

[0024] The second wall portion 23b of the top wall 23 is located further inward in the hollow portion 40 than the first wall portion 23a (lower in the example of FIG. 2 ) and is connected to the upper end of the side wall 21 via the aforementioned ridge portion 25a. The first wall portion 23a and the second wall portion 23b are formed, for example, by pressing a steel plate, and ridge portions 25b, 25c are formed between the first wall portion 23a and the second wall portion 23b, extending in the axial direction (X direction) of the outer panel 20. The first wall portion 23a and the second wall portion 23b are connected to each other via these ridge portions 25b, 25c.

[0025] The outer panel 20 having the stepped wall portion is manufactured using, for example, the press molding apparatus shown in Fig. 4. Specifically, the central portion of the blank 45 (the portion corresponding to the side wall 21 of the molded product) is clamped between a pad 46 and a punch 47, and in this state, a die 48 is lowered to manufacture the outer panel.

[0026] The inner panel 30 has side walls 31 extending in the X-Z plane that form walls on the inner side in the vehicle width direction (negative side in the Y direction) of the hollow portion 40, a bottom wall 32 extending from the lower end of the side wall 31 toward the outer side in the vehicle width direction (positive side in the Y direction), and a top wall 33 extending from the upper end of the side wall 31 toward the outer side in the vehicle width direction. These side walls 31, bottom wall 32 and top wall 33 are formed by, for example, pressing a single steel plate.

[0027] The hollow portion 40 is formed by joining the bottom wall 32 of the inner panel 30 and the first wall portion 22a of the bottom wall 22 of the outer panel 20 together, and by joining the top wall 33 of the inner panel 30 and the first wall portion 23a of the top wall 23 of the outer panel 20 together. As the joining means, for example, welding such as arc welding or spot welding, or adhesion with an industrial adhesive, etc. can be selected.

[0028] In this embodiment, the hollow portion 40 is formed by joining the outer panel 20 as the first member and the inner panel 30 as the second member, but the second member that constitutes the hollow portion 40 is not limited to the inner panel 30 and may be another member.

[0029] The outer panel 20 and the inner panel 30 are made of a metal material such as steel having a tensile strength of 590 MPa or more or 780 MPa or more, or an aluminum alloy or magnesium alloy. The tensile strength of the steel is preferably 980 MPa or more, and more preferably 1180 MPa or more.

[0030] The tensile strength of the material of each panel 20, 30 processed into a product is determined by converting the Vickers hardness measured by the following method. First, a test specimen is taken from a top plate portion (side wall 21 or side wall 31 in this embodiment) of the press-formed product, including a cross section along the thickness direction. Then, a Vickers hardness test (test force of 9.8 N) conforming to JIS Z 2244-1 (2024) is performed on the cross section (test surface) at 1 / 4 of the plate thickness from the top plate surface (the exterior surface of side wall 21 or the interior surface of side wall 31 in this embodiment) at 1 mm intervals. The average Vickers hardness measured at each measurement point is then calculated, and the tensile strength is calculated from the average Vickers hardness using a hardness conversion table. For example, a Vickers hardness of 243 HV corresponds to a tensile strength of 780 MPa, a Vickers hardness of 305 HV corresponds to a tensile strength of 980 MPa, and a Vickers hardness of 367 HV corresponds to a tensile strength of 1180 MPa.

[0031] The thickness of each panel 20, 30 is, for example, 0.8 to 10.0 mm. The thickness of each panel 20, 30 is preferably 1.6 mm or more, and more preferably 2.0 mm or more or 2.3 mm or more. The thickness of each panel 20, 30 may also be selected to be, for example, 2.5 mm or more or 2.9 mm or more. The thickness of each panel 20, 30 may also be selected to be, for example, 4.0 mm or less, 3.5 mm or less, or 3.0 mm or less. The thicknesses of each panel 20, 30 may also be different from each other.

[0032] The radius of curvature at the center of thickness of each ridge line portion of each panel 20, 30 is, for example, 5.0 to 15.0 mm. The axial length of each panel 20, 30 is, for example, 500 to 5000 mm.

[0033] Next, the stepped wall portion (bottom wall 22 and top wall 23) will be described in more detail with reference to Figure 3. As will be shown in the results of the examples described later, in a frame structure having a stepped wall portion, a step is formed so as to satisfy a specific numerical range depending on the thickness of the outer panel 20. Specifically, when the thickness of the outer panel 20 is 2.3 mm or more, the step height h of the stepped wall portion and the cross-sectional height h of the outer panel 20 satisfy 0.01 ≤ h / h ≤ 0.15, and the step width w of the stepped wall portion and the cross-sectional width w of the outer panel 20 satisfy 0.01 ≤ w / w ≤ 0.60. When the thickness of the outer panel 20 is 2.0 mm or more but less than 2.3 mm, the step is formed so as to satisfy 0.01 ≤ h / h ≤ 0.22 and 0.01 ≤ w / w ≤ 0.63. When the plate thickness of the outer panel 20 is 0.8 mm or more and less than 2.0 mm, the step is formed so as to satisfy 0.01≦h / h0≦0.30 and 0.01≦w / w0≦0.65.

[0034] Here, the "step height" refers to the height from the first wall portion to the second wall portion (length in the vehicle height direction). This step height can also be rephrased as the vertical length between the outer surfaces of the first wall portion and the second wall portion. In this embodiment, the height from the lower surface of the first wall portion 22a to the lower surface of the second wall portion 22b in the bottom wall 22 and the height from the upper surface of the first wall portion 23a to the upper surface of the second wall portion 23b in the top wall 23 are both step height h.

[0035] The "cross-sectional height" refers to the maximum length in the vehicle height direction (Z direction) of the outer panel 20. In this embodiment, the cross-sectional height h0 is the length in the Z direction from the lower surface of the first wall portion 22a of the bottom wall 22 to the upper surface of the first wall portion 23a of the top wall 23.

[0036] The "step width" is the minimum length from the outer surface of the side wall 21 to the first wall portion in the vehicle width direction (Y direction). This step width can also be rephrased as the length in the vehicle width direction from the outer surface of the side wall 21 to the boundary point (R end) between the first wall portion and the adjacent ridge line portion. In this embodiment, the Y-direction length from the outer surface of the side wall 21 to the first wall portion 22a of the bottom wall 22 and the Y-direction length from the outer surface of the side wall 21 to the first wall portion 23a of the top wall 23 are both the step width w.

[0037] The "cross-sectional width" refers to the maximum length in the vehicle width direction (Y direction) of the outer panel 20. In this embodiment, the cross-sectional width w0 is the length in the Y direction from the outer surface of the side wall 21 to the inner end of the bottom wall 22 or the top wall 23 in the vehicle width direction.

[0038] When the step height h / cross-sectional height h0 and the step width w / cross-sectional width w0 are formed so as to satisfy the above-mentioned specific ranges, crushing deformation of the outer panel 20 side of the side rail 10 during a side collision of the vehicle can be promoted, and deformation of the side rail 10 toward the vehicle body due to bending deformation can be suppressed. Furthermore, the second wall portions 22b, 23b function similarly to a typical bead-shaped portion, suppressing local buckling of the side wall 21 during a side collision and suppressing deformation of the side rail 10 toward the vehicle body. This reduces the amount of intrusion of the side rail 10 toward the vehicle body during a side collision, thereby improving the collision performance of the side rail 10.

[0039] If the shapes of the step portions of bottom wall 22 and top wall 23 are different from each other, the step height h and step width w of bottom wall 22 may have different numerical values ​​from the step height h and step width w of top wall 23. In this case, it is sufficient that the step of bottom wall 22 is formed so as to satisfy the above-mentioned numerical range using the step height h and step width w of bottom wall 22, and that the step of top wall 23 is further formed so as to satisfy the above-mentioned numerical range using the step height h and step width w of top wall 23.

[0040] When the plate thickness of the outer panel 20 is 2.3 mm or more, from the viewpoint of enhancing the effect of improving the collision performance, h / h0 is preferably 0.12 or less or 0.10 or less. h / h0 is more preferably 0.08 or less, and even more preferably 0.06 or less. Similarly, from the viewpoint of enhancing the effect of improving the collision performance, w / w0 is preferably 0.45 or more. w / w0 is more preferably 0.47 or more, and even more preferably 0.50 or more. Furthermore, w / w0 is preferably 0.58 or less, more preferably 0.57 or less, and even more preferably 0.56 or less.

[0041] When the plate thickness of the outer panel 20 is 2.0 mm or more and less than 2.3 mm, from the viewpoint of enhancing the above-mentioned effect of improving the collision performance, h / h0 is preferably 0.15 or less or 0.10 or less. h / h0 is more preferably 0.08 or less, and even more preferably 0.06 or less. Similarly, from the viewpoint of enhancing the above-mentioned effect of improving the collision performance, w / w0 is preferably 0.60 or less, more preferably 0.55 or less, and even more preferably 0.50 or less.

[0042] When the plate thickness of the outer panel 20 is 0.8 mm or more and less than 2.0 mm, from the viewpoint of enhancing the effect of improving the collision performance, h / h0 is preferably 0.08 or less. h / h0 is more preferably 0.07 or less, and even more preferably 0.06 or less. Similarly, from the viewpoint of enhancing the effect of improving the collision performance, w / w0 is preferably 0.60 or less. More preferably, it is 0.55 or less, and even more preferably, it is 0.50 or less.

[0043] The above describes the general configuration of the side rail 10 as a frame structure according to this embodiment. Note that the side rail 11 shown in Figure 1, which is disposed opposite the side rail 10, has a structure obtained by mirror-inverting the side rail 10 shown in Figures 2 and 3, and therefore a detailed description thereof will be omitted. However, the side rail 11 also provides the same functions and effects as the side rail 10.

[0044] The side rails 10, 11 with stepped walls according to this embodiment reduce the amount of intrusion into the vehicle body during a side collision, improving crashworthiness. Furthermore, the linear length of the side rails 10, 11 in a cross section perpendicular to the axial direction is substantially the same as the linear length of a side frame (not shown) without stepped walls, so the provision of the stepped walls does not result in a substantial increase in weight. In other words, the side rails 10, 11 with stepped walls according to this embodiment can be said to be a frame structure with excellent crashworthiness without a substantial increase in weight.

[0045] Second Embodiment Figure 5 is a diagram for explaining side frames 60, 61 as a frame structure according to a second embodiment. In this embodiment, the side frames 60, 61 are provided on the sides of the battery case 50. The battery case 50 has a pair of side walls 51, 52 extending in the vehicle length direction (X direction), with the side frame 60 attached to the side wall 51 and the side frame 61 attached to the side wall 52.

[0046] Next, the schematic configuration of the side frame 60 will be described, but explanations of materials, plate thickness, etc. that overlap with those of the first embodiment may be omitted. Furthermore, since the structure of the side frame 61 is a left-right inverted structure of the side frame 60 when viewed from the vehicle length direction (X direction), detailed explanation of the side frame 61 will be omitted.

[0047] 6 is a diagram showing the schematic configuration of the side frame 60 attached to the side wall 51 of the battery case 50, showing a cross section perpendicular to the vehicle length direction (X direction). The side frame 60 is disposed between the battery case 50 and the side sill 70 of the monocoque body.

[0048] The outer panel 20 of the side frame 60 has a generally L-shaped cross section including a side wall 21 and a bottom wall 22. The bottom wall 22 is a stepped wall portion having a first wall portion 22a and a second wall portion 22b located above the first wall portion 22a.

[0049] The inner panel 30 has a side wall 31 and a top wall 33, and further has a flange 34 extending from the lower end of the side wall 31 toward the inside in the vehicle width direction (negative side in the Y direction), and a flange 35 extending upward in the vehicle height direction from the outer end of the top wall 33 in the vehicle width direction (positive end in the Y direction).

[0050] The hollow portion 40 is formed by joining the side wall 21 of the outer panel 20 and the flange 35 of the inner panel 30 together, and by joining the bottom wall 22 of the outer panel 20 and the flange 34 of the inner panel 30 together. In addition, the side frame 60 is attached to the battery case 50 by, for example, joining the side wall 31 or the flange 34 of the inner panel 30 to the battery case 50.

[0051] When the structure of the side frame 60 is the structure shown in FIG. 6, the cross-sectional height h0 is the length in the vehicle height direction (length in the Z direction) from the lower surface of the first wall portion 22a of the bottom wall 22 to the upper end of the side wall 21, and the step height h, step width w, and cross-sectional width w0 are the same as in the first embodiment.

[0052] In the side frame 60 according to the second embodiment, if the step height h / cross-sectional height h0 and the step width w / cross-sectional width w0 satisfy the specific numerical ranges as described in the first embodiment, the amount of intrusion of the structure into the inside of the vehicle body can be reduced, and collision performance can be improved.

[0053] The structure of the side frame 60 is not limited to the structure shown in Fig. 6 and may be, for example, a structure as shown in Fig. 7. In the side frame 60 shown in Fig. 7, the outer panel 20 is not generally L-shaped, but has a shape including a side wall 21, a bottom wall 22 that is a stepped wall portion, a top wall 26, and a flange 27. The top wall 26 extends inward in the vehicle width direction (negative side in the Y direction) from the upper end of the side wall 21, and the flange 27 extends upward from the inner end of the top wall 26 in the vehicle width direction.

[0054] The inner panel 30 shown in Figure 7 is formed in an L-shape including a side wall 31 and a flange 34. The side wall 31 is joined to the flange 27 of the outer panel 20, and the flange 34 is joined to the first wall portion 22a of the bottom wall 22 of the outer panel 20. This forms the hollow portion 40 of the side frame 60.

[0055] 7, the cross-sectional height h0 is the length in the vehicle height direction (length in the Z direction) from the lower surface of the first wall portion 22a of the bottom wall 22 to the upper end of the flange 27. The step height h, step width w, and cross-sectional width w0 are the same as those of the side frame 60 having the structure shown in FIG.

[0056] The side frame 60 may have a structure as shown in Fig. 8. In the example shown in Fig. 8, the overall shape of the outer panel 20 is substantially the same as the shape of the outer panel 20 in Fig. 7 described above, but the outer panel 20 is composed of two parts. More specifically, the outer panel 20 has a part 20A including a bottom wall 22 and a side wall 21a, which are stepped wall portions, and a part 20B including a side wall 21b, a top wall 26, and a flange 27.

[0057] The upper end of the side wall 21a of the component 20A and the lower end of the side wall 21b of the component 20B are joined together, and these side walls 21a and 21b form the side wall 21 of the outer panel 20. In other words, the side wall 21a forms the lower part of the side wall 21 of the outer panel 20, and the side wall 21b forms the upper part of the side wall 21 of the outer panel 20.

[0058] When the side frame 60 has the structure shown in Figure 8, the step height h is the length in the vehicle height direction (length in the Z direction) from the lower surface of the first wall portion 22a to the lower surface of the second wall portion 22b of the bottom wall 22 of the part 20A. The cross-sectional height h0 is the length in the vehicle height direction (length in the Z direction) from the lower surface of the first wall portion 22a of the part 20A to the upper end of the flange 27 of the part 20B. The step width w is the length in the vehicle width direction (length in the Y direction) from the outer surface of the side wall 21a of the part 20A to the first wall portion 22a of the bottom wall 22. The cross-sectional width w0 is the length in the vehicle width direction (length in the Y direction) from the outer surface of the side wall 21a of the part 20A to the inner end of the bottom wall 22 in the vehicle width direction.

[0059] As described with reference to Figure 8, the outer panel 20 as the first member having the stepped wall portion is not limited to being made up of a single part, but may be made up of multiple parts joined together.

[0060] As illustrated in Figures 6 to 8, the first wall portion 22a of the bottom wall 22, which corresponds to the stepped wall portion, is a wall portion extending within a single plane (within the X-Y plane in this embodiment), and the plane on which the first wall portion 22a extends is a plane parallel to the joint surface between the inner panel 30 and the first wall portion 22a. In other words, the first wall portion 22a is a wall portion extending parallel to the joint surface with the inner panel 30. On the other hand, for example, in a hat-shaped part having a flange (not shown) extending downward from the bottom wall 22, the plane on which the bottom wall 22 extends is non-parallel to the joint surface between the inner panel 30 and the bottom wall 22. In other words, such a hat-shaped part is different from the outer panel 20 having the bottom wall 22 that is a stepped wall portion.

[0061] While the embodiments of the present invention have been described above, the present invention is not limited to these examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the technical ideas described in the claims, and it is understood that these modifications also fall within the technical scope of the present invention.

[0062] 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 the individual components involved in the combination, as well as other functions and advantages that will be apparent to those skilled in the art from the description herein.

[0063] In addition, in the above-described first embodiment, the side rails 10, 11 provided on the sides of the battery case 50 were described as an example of a frame structure, but the side rails 10, 11 may also be applied, for example, as side rails of a ladder frame in a vehicle not equipped with a battery case.

[0064] Furthermore, for example, the frame structure described in this specification may be a bumper beam, a door impact beam, a side sill, a center pillar (B-pillar), a front pillar (A-pillar), or a roof rail. In any of the application examples, in a frame structure having a hollow portion including a first member and a second member located on the vehicle interior side of the first member, if the first member has a side wall that forms the vehicle exterior wall of the hollow portion and a stepped wall portion extending from the side wall to the vehicle interior side, and if the stepped wall portion has a shape that satisfies the specific numerical ranges for h / h0 and w / w0 described above, then an effect of suppressing deformation toward the inside of the vehicle body can be obtained.

[0065] Note that when the frame structure is, for example, the side rails 10, 11 or side frame 60 of the ladder frame 1 described above, a door impact beam, a side sill, a center pillar, a front pillar, or a roof rail, the "outside of the vehicle" refers to the outside in the vehicle width direction (the opposite side to the cabin). Also, when the frame structure is a front bumper beam, the "outside of the vehicle" refers to the front side in the vehicle length direction (the opposite side to the cabin), and when the frame structure is a rear bumper beam, the "outside of the vehicle" refers to the rear side in the vehicle length direction (the opposite side to the cabin).

[0066] Furthermore, when the frame structure is, for example, the side rails 10, 11 or side frame 60 of the ladder frame 1 described above, a door impact beam, a side sill, a center pillar, a front pillar, or a roof rail, the "interior side" refers to the inside in the vehicle width direction (cabin side). When the frame structure is a front bumper beam, the "interior side" refers to the rear side in the vehicle length direction (cabin side), and when the frame structure is a rear bumper beam, the "interior side" refers to the front side in the vehicle length direction (cabin side).

[0067] As an example of the present invention, an analytical model of a frame structure having steps on the top and bottom walls of the outer panel as shown in Figure 3 was created, and a three-point bending simulation was performed to evaluate collision performance. As a comparative example, an analytical model of a frame structure having no steps on the top and bottom walls of the outer panel was created, and a three-point bending simulation was performed in the same way as in the example.

[0068] (Simulation Conditions) Fig. 9 is a diagram for explaining an analytical model of a three-point bending simulation assuming a side impact with a pole. The frame structure 80 shown in Fig. 9 is a structure in which an outer panel 90 having a U-shaped cross section and an inner panel 30 having a U-shaped cross section are joined together, and is a model as a comparative example in which the outer panel 90 does not have a stepped wall portion.

[0069] Two pillars 100 extending in the vehicle width direction (Y direction) are in contact with the inner panel 30 of the frame structure 80 and spaced apart in the vehicle length direction (X direction). The diameter of the pillars 100 is 100 mm, and the distance between the centers of the two pillars 100 is 350 mm. The three-point bending simulation was performed by impacting a pole 101 with a diameter of 300 mm from the outer panel 90 side at the center position between the two pillars 100. The energy input to the pole 101 was 12 kJ.

[0070] 10 is a diagram for explaining the intrusion amount of the frame structure into the vehicle body during a pole collision. In this simulation, the intrusion amount of the frame structure into the vehicle body is the distance in the Y direction from the initial position of the wall surface of the inner panel 30 on the vehicle body inner side (the wall surface on the negative side in the Y direction) to the point on that wall that is located most inward in the vehicle body after the pole collision.

[0071] A three-point bending simulation under the simulation conditions described above and an evaluation of the amount of intrusion of the frame structure into the vehicle body were performed for each model (No. 1 to 18) shown in Table 1. The outer panel and inner panel of each model were both made of 1180 MPa steel plate.

[0072]

[0073] Details of each item in Table 1 are as follows: "Outer plate thickness" is the plate thickness of the outer panel, and "Inner plate thickness" is the plate thickness of the inner panel. "h", "h0", "w", and "w0" are the step height, cross-sectional height, step width, and cross-sectional width, respectively, as described in the above embodiment. Note that the underlined values ​​in the "h / h0" and "w / w0" items in Table 1 indicate values ​​outside the range of values ​​specified according to the plate thickness as described in the above embodiment.

[0074] The "rate of change in intrusion amount" is an index showing the amount of intrusion of each model relative to the amount of intrusion of a comparative example model that does not have a stepped wall portion, and is a value obtained by dividing the amount of intrusion of each model by the amount of intrusion of a model that does not have a stepped wall portion. A rate of change in intrusion amount of less than 1 means that the amount of intrusion into the vehicle body is smaller than that of a model that does not have a stepped wall portion, and collision performance is improved. Note that the rate of change in intrusion amount of models Nos. 1 to 6 is a value based on the amount of intrusion of model No. 1, the rate of change in intrusion amount of models Nos. 7 to 12 is a value based on the amount of intrusion of model No. 7, and the rate of change in intrusion amount of models Nos. 13 to 18 is a value based on the amount of intrusion of model No. 13.

[0075] FIG. 11 shows the relationship between the step height h / cross-sectional height h0 and the intrusion amount in this simulation. FIG. 12 shows the relationship between the step width w / cross-sectional width w0 and the intrusion amount in this simulation. As shown in FIGS. 11 and 12 and Table 1 above, among the models (Nos. 1 to 6) with an outer panel thickness of 2.9 mm, the intrusion amount change rate was less than 1 for models that satisfied 0.01≦h / h0≦0.12 and 0.01≦w / w0≦0.60. In other words, the intrusion amount of the frame structure into the vehicle body during a pole collision was suppressed compared to Model No. 1, which did not have a stepped wall portion, and the collision performance was improved.

[0076] Furthermore, among the models (Nos. 7 to 12) with an outer panel thickness of 1.6 mm, the models that satisfied 0.01≦h / h0≦0.30 and 0.01≦w / w0≦0.65 had an intrusion change rate of less than 1. In other words, the intrusion amount of the frame structure into the vehicle body during a pole collision was suppressed more than in Model No. 7, which did not have a stepped wall portion, and the collision performance was improved.

[0077] Among the models (Nos. 13 to 18) with an outer panel thickness of 2.3 mm, the models that satisfied 0.01≦h / h0≦0.15 and 0.01≦w / w0≦0.60 had an intrusion change rate of less than 1. In other words, the intrusion amount of the frame structure into the vehicle body during a pole collision was suppressed more than in Model No. 13, which did not have a stepped wall portion, and the collision performance was improved.

[0078] As shown in Table 1, the h / h0 of Model No. 18, which has an outer panel thickness of 2.3 mm, is the same as the h / h0 of Model No. 12, which has an outer panel thickness of 1.6 mm. However, the rate of change in intrusion amount of Model No. 18 was inferior to that of Model No. 12. Considering the slope of the line connecting the plotted points for the same thickness in Figure 11, it is inferred that when the outer panel thickness is slightly thinner than 2.3 mm, the rate of change in intrusion amount will be less than 1 even if h / h0 is approximately 0.22. Similarly, considering the slope of the line connecting the plotted points for the same thickness in Figure 11, it is inferred that when the outer panel thickness is slightly thinner than 2.3 mm, the rate of change in intrusion amount will be less than 1 even if w / w0 is approximately 0.63. Therefore, when the thickness of the outer panel is 2.0 mm or more and less than 2.3 mm, a stepped wall portion is formed that satisfies 0.01≦h / h0≦0.22 and 0.01≦w / w0≦0.63, thereby obtaining a frame structure with excellent collision performance.

[0079] 11 and 12, it is inferred that when the outer panel thickness is less than 2.0 mm, even if the upper limits of h / h0 and w / w0 are further increased compared to when the outer panel thickness is 2.0 mm or greater, the rate of change in penetration amount will be less than 1. Therefore, when the outer panel 20 thickness is 0.8 mm or greater and less than 2.0 mm, a stepped wall portion is formed that satisfies 0.01≦h / h0≦0.30 and 0.01≦w / w0≦0.65, thereby obtaining a frame structure with excellent collision performance.

[0080] Here, the reason why collision performance differs depending on whether or not the outer panel has a stepped wall portion will be explained with reference to Figures 13 and 14. Figure 13 is a diagram that schematically shows the deformation state of a model without a stepped wall portion when a pole collides. Figure 14 is a diagram that schematically shows the deformation state of a model with a stepped wall portion when a pole collides. In the diagram, (a) shows the initial state of the frame structure before the pole collides, and (b) shows the deformation state of the frame structure when the pole collides.

[0081] In the model shown in Figure 13, in which the outer panel 90 does not have a stepped wall portion, when the pole 101 collides with the side wall 91, the bottom wall 92 and the top wall 93 are deformed by a bending moment, so that they collapse outward from their initial positions in cross section. On the other hand, in the model shown in Figure 14, in which the outer panel 20 has the bottom wall 22 and the top wall 23 that are stepped wall portions, when the pole collides, the first wall portions 22a, 23a of the stepped wall portions collapse outward in cross section, but the second wall portions 22b, 23b collapse inward in cross section.

[0082] This increases the amount of crushing deformation on the outer panel 20 side of the frame structure 10, and suppresses bending deformation on the inner panel 30 side. In addition, the stepped wall portion functions similarly to a typical bead-shaped portion during a collision of the pole 101, suppressing local buckling of the side wall 21. As a result, the stress generated in the outer panel 20 during a collision of the pole 101 is distributed over a wider range in the vehicle length direction (X direction) compared to the frame structure 80 with a U-shaped cross section as shown in Figure 13, suppressing deformation of the frame structure 10. The frame structure 10 with the stepped wall portion has improved collision performance due to these deformation suppression effects, and can suppress intrusion into the inside of the vehicle body.

[0083] The above describes embodiments of the present invention. The effects described herein are merely illustrative or exemplary and are not limiting. In other words, the technology disclosed herein may achieve other effects that will be apparent to those skilled in the art from the description of this specification, in addition to or in place of the above effects.

[0084] The present invention is applicable to automobile frame structures such as side rails of ladder frames.

[0085] REFERENCE SIGNS LIST 1 Ladder frame 10 Side rail (frame structure) 11 Side rail (frame structure) 12 Cross member 20 Outer panel 20A Outer panel component 20B Outer panel component 21 Side wall 21a Side wall 21b Side wall 22 Bottom wall 22a First wall portion 22b Second wall portion 23 Top wall 23a First wall portion 23b Second wall portion 24a to 24c Ridge portion 25a to 25c Ridge portion 26 Top wall 27 Flange 30 Inner panel 31 Side wall 32 Bottom wall 33 Top wall 34 Flange 35 Flange 40 Hollow portion 45 Blank 46 Pad 47 Punch 48 Die 50 Battery case 60 Side frame 61 Side frame 70 Side sill 80 Frame structure 90 Outer panel 91 Side wall 92 Bottom wall 93 Top wall 100 Support 101 Pole h Step height h0 Section height w Step width w0 Section width

Claims

1. An automobile frame structure comprising: a first member made of a metal material having a tensile strength of 780 MPa or more; a second member made of a metal material and positioned on the vehicle interior side of the first member; and a hollow portion extending in the axial direction of the frame structure formed by the first member and the second member, wherein the first member has: a side wall constituting the wall portion on the vehicle exterior side of the hollow portion; a stepped wall portion extending from the side wall toward the vehicle interior side; and a ridge portion extending in the axial direction connecting the side wall and the stepped wall portion, wherein the stepped wall portion has: a first wall portion joined to the second member and extending parallel to the joint surface with the second member; and a second wall portion located on the inner side of the hollow portion than the first wall portion and connected to the ridge portion, wherein the plate thickness of the first member is 2.3 mm or more, and the step height h of the stepped wall portion and the cross-sectional height h0 of the first member satisfy the relationship 0.01≦h / h0≦0.15, A frame structure, wherein a step width w of the stepped wall portion and a cross-sectional width w0 of the first member satisfy 0.01≦w / w0≦0.

60.

2. The frame structure according to claim 1, wherein the plate thickness of the first member is 2.5 mm or more, and the step height h and the cross-sectional height h0 satisfy h / h0≦0.

12.

3. The frame structure according to claim 1 or 2, wherein the step height h and the cross-sectional height h0 satisfy h / h0≦0.

10.

4. A frame structure according to any one of claims 1 to 3, wherein the step width w and the cross-sectional width w0 satisfy 0.45≦w / w0≦0.

58.

5. An automobile frame structure comprising: a first member made of a metal material having a tensile strength of 780 MPa or more; a second member made of a metal material and positioned on the vehicle interior side of the first member; and a hollow portion extending in the axial direction of the frame structure formed by the first member and the second member, wherein the first member has: a side wall constituting the wall portion on the vehicle exterior side of the hollow portion; a stepped wall portion extending from the side wall toward the vehicle interior side; and a ridge portion extending in the axial direction connecting the side wall and the stepped wall portion, wherein the stepped wall portion has: a first wall portion joined to the second member and extending parallel to the joint surface with the second member; and a second wall portion located on the inner side of the hollow portion than the first wall portion and connected to the ridge portion, wherein the plate thickness of the first member is 2.0 mm or more and less than 2.3 mm, A frame structure, wherein a step height h of the stepped wall portion and a cross-sectional height h0 of the first member satisfy 0.01≦h / h0≦0.22, and a step width w of the stepped wall portion and a cross-sectional width w0 of the first member satisfy 0.01≦w / w0≦0.

63.

6. An automobile frame structure comprising: a first member made of a metal material with a tensile strength of 780 MPa or more; a second member made of a metal material and positioned on the vehicle interior side of the first member; and a hollow portion extending in the axial direction of the frame structure formed by the first member and the second member, wherein the first member has: a side wall constituting the wall portion on the vehicle exterior side of the hollow portion; a stepped wall portion extending from the side wall toward the vehicle interior side; and a ridge portion extending in the axial direction connecting the side wall and the stepped wall portion, wherein the stepped wall portion has: a first wall portion joined to the second member and extending parallel to the joint surface with the second member; and a second wall portion located on the inner side of the hollow portion than the first wall portion and connected to the ridge portion, wherein the plate thickness of the first member is 0.8 mm or more and less than 2.0 mm, A frame structure, wherein a step height h of the stepped wall portion and a cross-sectional height h0 of the first member satisfy 0.01≦h / h0≦0.30, and a step width w of the stepped wall portion and a cross-sectional width w0 of the first member satisfy 0.01≦w / w0≦0.

65.

7. The frame structure according to claim 5 or 6, wherein the step height h and the cross-sectional height h0 satisfy the relationship h / h0≦0.

08.

8. A frame structure according to any one of claims 5 to 7, wherein the step width w and the cross-sectional width w0 satisfy w / w0≦0.

60.

9. A frame structure according to any one of claims 1 to 8, wherein the frame structure is a side rail of a ladder frame.

10. The frame structure according to any one of claims 1 to 8, wherein the frame structure is a side frame disposed between a battery case and a side sill.

11. A frame structure according to any one of claims 1 to 8, wherein the frame structure is a bumper beam.

12. A frame structure according to any one of claims 1 to 8, wherein the frame structure is a door impact beam.

13. The frame structure according to any one of claims 1 to 8, wherein the frame structure is a side sill.

14. The frame structure according to any one of claims 1 to 8, wherein the frame structure is a center pillar.

15. The frame structure according to any one of claims 1 to 8, wherein the frame structure is a front pillar.

16. The frame structure according to any one of claims 1 to 8, wherein the frame structure is a roof rail.

Images