Subframe for vehicle

Abstract

The present invention provides a vehicle subframe. In the lower component of the vehicle subframe, the middle portion between the outer and inner portions has an outer curved bottom and an inner curved bottom. A first closed section of a first transverse member and a second closed section of the lower component are arranged side by side in the vertical direction in such a way that they are separated by the wall portion of the first closed section of the first transverse member and are adjacent to each other, thereby forming a parallel closed section. The parallel closed section is provided in correspondence with at least a portion of the outer curved bottom and the inner curved bottom.

Description

Technical Field

[0001] This invention relates to a vehicle subframe, and more particularly to a vehicle subframe that supports suspension arms and the like and is mounted on automobiles and other vehicles. Background Technology

[0002] In recent years, in automobiles and other vehicles, in addition to improving sport performance, there is also a demand to improve the quality of the ride. Therefore, in the subframes installed in related vehicles, in addition to ensuring strength, it is also necessary to set the appropriate rigidity.

[0003] Therefore, the subframe is required to have the following structure: while maintaining productivity, it should be able to increase the degree of freedom in setting the support rigidity of the suspension components, and should be able to avoid localized stress concentration.

[0004] In this context, Japanese Patent Application Publication No. 2013-95393 discloses a structure for the rear body of an automobile, which, while ensuring arm length, improves the lightweight and high rigidity of the rear subframe and seeks to enhance rear-end collision safety. In the rear subframe 21, the rear portions 26 of the left and right side member parts 22, 22 are mounted to the left and right rear side frames 7, 7, and the front portions 25 of the left and right side member parts 22, 22 are mounted to the left and right rear side frames 7. The portion of the transverse member 10 of the vehicle body between the rear and 7 that is closer to the rear frame 7, and the bracket 31 that forms the support portion 29 of the front lower arm 33, has: a front side plate 34 and a rear side plate 35, which each have an L-shaped cross section and a generally triangular shape when viewed from the front; and a side plate 36 that blocks the outer openings of the front side plate 34 and the rear side plate 35. The bracket 31 has a closed cross section structure and is joined to the tubular side member portion 22 and transverse member portion 23. Summary of the Invention

[0005] However, according to the inventor's research, in the structure disclosed in Japanese Patent Application Publication No. 2013-95393, a cutout is provided at the inner end of the bracket 31, where the stress tends to increase due to input loads from the lower arm and the like during vehicle operation, thereby opening the closed section of the bracket 31. Furthermore, the front side plate 34 and the rear side plate 35 have a simple triangular shape in which the area decreases linearly towards their inner sides. Therefore, there are naturally limits to the degree of freedom in setting the support stiffness of the suspension components in order to appropriately reduce stress concentration. In this respect, it is believed that there is room for improvement in achieving a balance between strength and stiffness, and in setting appropriate stiffness while ensuring necessary strength.

[0006] The present invention was completed based on the above research, and its purpose is to provide a vehicle subframe that optimizes the balance between strength and rigidity by realizing a structure that improves the degree of freedom in setting its rigidity, and ensures the necessary strength while appropriately setting the rigidity.

[0007] To achieve the above objectives, a vehicle subframe according to a first aspect of the present invention has the following structure: a cylindrical first transverse member extending in the width direction of the vehicle; a second transverse member opposing the first transverse member in the longitudinal direction of the vehicle and extending in the width direction; a pair of side members opposing each other in the width direction and extending in the longitudinal direction, respectively engaging with the first transverse member and the second transverse member; and a lower member extending in the width direction relative to the first transverse member on the lower side in the vertical direction of the vehicle and engaging with the first transverse member, wherein the lower member sequentially comprises, from the outer side to the inner side in the width direction: an outer portion having a lower support portion for supporting the suspension components of the vehicle; a middle portion connected to the outer portion; and an inner portion connected to the middle portion, wherein the middle portion... It has: an outer curved bottom that connects to the bottom of the outer portion and curves upward from the bottom of the outer portion without descending as it moves toward the inner side; and an inner curved bottom that connects to the bottom of the inner portion and curves downward from the bottom of the inner portion without ascending as it moves toward the outer side, the first transverse member having a first closed section in a cross-section obtained by cutting with a plane defined by the front-back direction and the vertical direction, the lower member having a second closed section in a cross-section obtained by cutting with the plane, the first closed section and the second closed section being arranged side by side in the vertical direction to form a parallel closed section, the parallel closed section being arranged to correspond to at least a portion of the outer curved bottom and the inner curved bottom in the middle portion.

[0008] Furthermore, in the second aspect of the present invention, based on the first aspect described above, the parallel arrangement of closed sections must be configured to correspond to at least a portion of the inner curved bottom.

[0009] Furthermore, in a third aspect of the present invention, based on the first or second aspect, the parallel closed sections are continuously arranged in the width direction to extend over one or both of the inner curved bottom, the outer curved bottom, and the bottom of the inner portion.

[0010] Furthermore, in a fourth aspect of the invention, based on any one of the first to third aspects, an upper support member is positioned opposite the lower member on its upper side in the vertical direction, across the first transverse member, and has an upper support portion for supporting a suspension member of the vehicle. The upper support member is provided in a manner that engages with the first transverse member, and engages with an inclined face formed by recessing and tilting a portion of the cylindrical wall of the first transverse member.

[0011] Furthermore, in a fifth aspect of the invention, based on any one of the first to fourth aspects, the pair of side members each have: a pair of sidewalls facing each other in the width direction; a top wall connecting the upper ends of the pair of sidewalls in the vertical direction to each other; and a bottom wall facing the top wall on the lower side and connecting the lower ends of the pair of sidewalls in the vertical direction to each other, wherein the front portion of the top wall in the front-rear direction has: a recessed portion formed by recessing the middle portion of the top wall in the width direction toward the lower side; and a pair of convex shapes. The top wall is formed by protruding from both ends of the top wall in the width direction relative to the recessed portion toward the upper side. In the top wall, the front end of the recessed portion engages with the first transverse member. The bottom wall has the following on its front side: a recessed portion formed by recessing the middle portion of the bottom wall in the width direction toward the upper side; and a pair of convex portions formed by protruding from both ends of the bottom wall in the width direction relative to the recessed portion toward the lower side. In the bottom wall, the front end of the recessed portion engages with the first transverse member.

[0012] According to the structure of a first aspect of the invention, the lower member, from the outer side toward the inner side in the width direction, sequentially comprises: an outer portion having a lower support portion for supporting the suspension components of the vehicle; a middle portion connected to the outer portion; and an inner portion connected to the middle portion. The middle portion has: an outer curved bottom connected to the bottom of the outer portion, and having a trajectory that curves upward from the bottom of the outer portion without descending as it moves toward the inner side; and an inner curved bottom connected to the bottom of the inner portion, and having a trajectory that curves downward from the bottom of the inner portion without ascending as it moves toward the outer side. The first transverse member has a first closed cross-section in a section obtained by cutting with a plane defined by the front-rear direction and the vertical direction. The lower member has a second closed section in the section obtained by cutting with the plane. The first closed section and the second closed section are arranged side by side in the vertical direction, separated by the wall portion of the first closed section of the first transverse member. The side by side closed sections are arranged to correspond to at least a portion of the outer curved bottom and the inner curved bottom in the middle part. With the above structure, the necessary strength of the vehicle subframe can be ensured, and the degree of freedom in setting the support stiffness of its suspension components can be improved. It is possible to optimize the strength and stiffness while achieving a balance between them, and to set the desired stiffness and ensure the required strength.

[0013] Furthermore, according to the structure of the second aspect of the invention, the parallel closed sections must be configured to correspond to at least a portion of the inner curved bottom, thereby enabling the necessary strength of the vehicle subframe to be ensured by utilizing the minimum range of parallel longitudinal sections in the width direction, and appropriately setting the support rigidity of the suspension components.

[0014] Furthermore, according to the structure of the third aspect of the present invention, the closed sections are arranged side by side and continuously arranged in the width direction to cover one or both of the inner curved bottom and the outer curved bottom and the bottom of the inner portion, thereby reducing stress concentration in the vehicle subframe and eliminating local weak points, and further increasing its strength.

[0015] Furthermore, according to the structure of the fourth aspect of the present invention, the upper support member is opposite to the lower member in the vertical direction via the first transverse member, and has an upper support portion for supporting the suspension member of the vehicle. The upper support member is provided in such a way as to engage with the first transverse member. The upper support member engages with an inclined surface formed by recessing and tilting a portion of the cylindrical wall of the first transverse member. Thus, the upper support members can be reliably engaged with each other in a state of contact with the inclined surface, and the occurrence of peeling failure of the joint can be suppressed.

[0016] Furthermore, according to the structure of the fifth aspect of the present invention, each of the pair of side members has: a pair of sidewalls facing each other in the width direction; a top wall connecting the upper ends of the pair of sidewalls in the vertical direction to each other; and a bottom wall facing the top wall on the lower side and connecting the lower ends of the pair of sidewalls in the vertical direction to each other. The front portion of the top wall in the front-rear direction has: a recessed portion formed by recessing the middle portion of the top wall in the width direction toward the lower side; and a pair of convex portions formed by recessing the two ends of the top wall in the width direction relative to the recessed portion. The recessed portion is formed by protruding upwards relative to each other. In the top wall, the front end of the recessed portion is joined to the first transverse member. The bottom wall has the following on its front side: a recessed portion formed by recessing the middle part of the bottom wall in the width direction upwards; and a pair of convex portions, the two ends of the bottom wall in the width direction protruding downwards relative to the recessed portion. In the bottom wall, the front end of the recessed portion is joined to the first transverse member, thereby improving the coating distribution capability of the pair of side members and ensuring their welding length to increase welding strength. Attached Figure Description

[0017] Figure 1 This is a perspective view of a vehicle subframe according to an embodiment of the present invention;

[0018] Figure 2 This is a top view of the vehicle subframe in this embodiment;

[0019] Figure 3 This is a bottom view of the vehicle subframe in this embodiment;

[0020] Figure 4 This is a front view of the vehicle subframe in this embodiment;

[0021] Figure 5 This is a right view of the vehicle subframe in this embodiment;

[0022] Figure 6A This is a front view of the front of the right side frame of the vehicle subframe according to this embodiment. Figure 6B It is along Figure 6A A sectional view of the DD line in the middle;

[0023] Figure 7 It is along Figure 4 A sectional view of line AA in the diagram;

[0024] Figure 8 It is along Figure 4 A sectional view of the BB line in the middle;

[0025] Figure 9 It is along Figure 4 A cross-sectional view of the CC line. Detailed Implementation

[0026] The following is for reference only. Figures 1 to 9 The vehicle subframe according to an embodiment of the present invention will be described in detail. Furthermore, in the figures, the x-axis, y-axis, and z-axis constitute a three-axis orthogonal coordinate system. The positive direction of the x-axis is the leftward direction of the vehicle body, the positive direction of the y-axis is the forward direction of the vehicle body, and the positive direction of the z-axis is the upward direction of the vehicle body. Sometimes the direction of the x-axis is referred to as the width direction, sometimes the direction of the y-axis is referred to as the front-rear direction, and sometimes the direction of the z-axis is referred to as the vertical direction. Additionally, the xy-plane is sometimes referred to as the horizontal plane.

[0027] Figure 1 This is a perspective view of the vehicle subframe according to this embodiment. Figure 2 This is a top view of the vehicle subframe according to this embodiment. Figure 3 This is a bottom view of the vehicle subframe according to this embodiment. Figure 4 This is a front view of the vehicle subframe according to this embodiment. Figure 5 This is a right view of the vehicle subframe according to this embodiment. Figure 6A This is a front view of the front of the right side frame of the vehicle subframe according to this embodiment. Figure 6B It is along Figure 6A A cross-sectional view of the DD line. Additionally... Figures 7 to 9 In order along Figure 4 The cross-sectional views along line AA, line BB, and line CC are shown. Furthermore, for ease of explanation, in... Figures 5 to 6B In the diagram, a portion of the components on the left side of the vehicle's subframe is shown with numbers in parentheses, as needed, together with the numbers of the components on the right side.

[0028] like Figures 1 to 9 As shown, the subframe 1 in this embodiment, although not illustrated, is mounted on the rear frame or other body structure of a vehicle such as an automobile and supports the suspension arms. This subframe 1 typically has a shape that is substantially symmetrical about a plane parallel to the yz plane and passing through the center of the vehicle body in the width direction.

[0029] Specifically, the subframe 1, when viewed from above, has a grid-like shape and includes the following main skeletal elements: a front transverse member 10, which is composed of a cylindrical component extending in the width direction; a rear transverse member 100, which is opposite to the front transverse member 10 on its rear side and extends in the width direction; and a left side member 120 and a right side member 220, which are opposite to each other in the width direction and each extends in the front-rear direction, and are respectively joined to the front transverse member 10 and the rear transverse member 100. Each of these skeletal elements is typically welded together by means of arc welding or the like. Furthermore, depending on the type of vehicle to which it is applied, the front-rear configuration of the subframe 1 can be reversed.

[0030] The front transverse member 10 is typically made of a cylindrical steel tube. It is formed and flattened by partially recessing a portion of the cylindrical surrounding wall 12 from its original shape using hydroforming or similar methods, resulting in a planar portion such as an inclined plane 14 inclined relative to the xz plane and a planar portion 16 parallel to the xz plane. Alternatively, the front transverse member 10 may also have a planar portion parallel to the xy plane formed by partially flattening the top or bottom of the surrounding wall 12. Furthermore, the front transverse member 10 may also be composed of multiple parts obtained by stamping various flat steel plates or other flat components.

[0031] In detail, the front transverse member 10 has: a main body 20, which has a curved shape protruding rearward when viewed from above and extends in the width direction; a left extension 22, which bends at the left end of the main body 20 in the width direction with a curvature greater than that of the main body 20 and extends in the left-forward direction; and a right extension 26, which bends at the right end of the main body 20 in the width direction with a curvature greater than that of the main body 20 and extends in the right-forward direction. The left end of the left extension 22 forms a left cutout 24 cut into a generally arc shape, and a sleeve member 310 is welded to the left cutout 24 by arc welding or the like. Similarly, the right end of the right extension 26 forms a right cutout 28 cut into a generally arc shape, and a sleeve member 310 is welded to the right cutout 28 by arc welding or the like.

[0032] In the front transverse member 10, the left cutout 24 and the right cutout 28 become open ends with respect to the main body 20, the left extension 22 and the right extension 26, thereby opening the interior of the main body 20, the left extension 22 and the right extension 26 to the outside, but forming a closed section SE1 in the longitudinal section obtained by cutting with a plane parallel to the yz plane.

[0033] In the front transverse member 10, the curvature of the left extension 22 and the right extension 26 is set to be greater than that of the main body 20. This is to increase the layout space at the front of the main body 20 while ensuring the rigidity of the main body 20 in the width direction. The left end of the left extension 22 and the right end of the right extension 26 are respectively positioned at a more forward position. The sleeve member 310, which is welded to the left cutout 24 and the right cutout 28 and becomes the front body mounting part, is located at a more forward position away from the rear body mounting part, thereby increasing the span between the front and rear body mounting parts.

[0034] In the front transverse member 10, the premise is that the sleeve members 310 and 310 with the necessary capacity of the subframe mounting components (not shown) can be welded to the left cutout 24 and the right cutout 28 with the required welding strength, and the required strength and rigidity of the left extension 22 and the right extension 26 can be ensured. Under this premise, from the viewpoint of increasing the layout freedom of the left extension 22 and the right extension 26 in the vertical direction, the length of the left extension 22 and the right extension 26 in the vertical direction is set to be shorter than the length of the main body 20 in the vertical direction, and the left extension 22 and the right extension 26 are flattened.

[0035] Additionally, the front transverse member 10 has a lower member 30 extending in the width direction below the front transverse member 10 and engaging with the front transverse member 10. Furthermore, the lower member 30 may also engage only the portions of its two ends in the width direction that protrude rearward from the front transverse member 10 across the left member 120 and the right member 220.

[0036] The lower component 30 typically comprises a first component 40 and a second component 50, which are obtained by stamping flat components such as steel plates and have a longitudinal section of approximately L-shape obtained by cutting with a plane parallel to the yz plane. Alternatively, the lower component 30 may be formed using a single plate component instead of the two plate components, the first component 40 and the second component 50, as needed.

[0037] The first component 40 includes: a front longitudinal wall 42, which is a longitudinal wall blocking the front side of the lower component 30, erected vertically and extending in the width direction; and a front bottom wall 44, which bends rearward parallel to the horizontal plane at the lower end of the front longitudinal wall 42, protrudes rearward from the lower end, and extends in the width direction. A left front through hole 46 is formed at the left end of the front longitudinal wall 42, and a right front through hole 48 is formed at the right end of the front longitudinal wall 42. Nut components 320 and 320 are welded to the left front through hole 46 and the right front through hole 48 respectively, erected from the front surface of the front longitudinal wall 42 and facing forward.

[0038] The second component 50 has a basic structure that flips the first component 40 backwards, and includes: a rear longitudinal wall 52, which is a longitudinal wall that blocks the rear side of the lower component 30, erected vertically and extending in the width direction; and a rear bottom wall 54, which bends forward parallel to the horizontal plane at the lower end of the rear longitudinal wall 52, protrudes forward from the lower end, and extends in the width direction. A left rear through hole 56 is formed at the left end of the rear longitudinal wall 52, and a right rear through hole 58 is formed at the right end of the rear longitudinal wall 52, the left rear through hole 56 and the right rear through hole 58 being opposite to the left front through hole 46 and the right front through hole 48 on the rear side.

[0039] In detail, the lower member 30 has the following components from the left outer side to the inner side: a left outer side portion 60, which is provided with a nut member 320 for supporting the left front lower side support portion of the vehicle's suspension arm such as the lower arm, a left front through hole 46, and a left rear through hole 56; a left middle portion 62, which is connected to the left outer side portion 60 on the right side; and a left inner side portion 65, which is connected to the left middle portion 62 on the right side and near the center in the width direction. The left middle portion 62 has: a left outward curved bottom 63, which is connected to the front bottom wall 44 and the rear bottom wall 54 of the left outer portion 60, i.e., the left outer bottom 61, and has a curved shape that protrudes towards the lower right side. Moreover, the curved shape has a trajectory that rises from the left outer bottom 61 without descending inward and increases in the tangential inclination (angle relative to the horizontal plane) as it moves inward; and a left inward curved bottom 64, which is connected to the front bottom wall 44 and the rear bottom wall 54 of the left inner portion 65, i.e., the left inner bottom 66, and has a curved shape that protrudes towards the upper left side. Moreover, the curved shape has a trajectory that rises from the left inner bottom 66 without ascending outward and decreases in the tangential inclination (angle relative to the horizontal plane) as it moves inward. By setting such a left outward curved bottom 63 and a left inward curved bottom 64, during the design process, if their curvature (radii of curvature RO, RI) is varied, the rigidity against input loads, primarily in the width direction, applied from the suspension arm can be varied. Therefore, provided that the required strength of the lower member 30, and consequently the subframe 1, is ensured, the shape of the left outward curved bottom 63 and the left inward curved bottom 64, which impart this required support rigidity to the suspension arm, can be set with a high degree of freedom. Furthermore, provided that the required strength and rigidity are ensured, an uncurved planar bottom can be positioned between the left outward curved bottom 63 and the left inward curved bottom 64. In addition, the curvature (radii of curvature RO, RI) of the left outward curved bottom 63 and the left inward curved bottom 64 is not limited to being a single curvature (radii of curvature RO, RI), but can be a composite curvature composed of multiple curvatures (radii of curvature RO, RO', ..., RI, RI', ...) as needed.

[0040] The structure associated with the right outer portion 70, right middle portion 72, and right inner portion 75, which are arranged sequentially from the right outer side to the inner side of the lower component 30, is a structure that is symmetrical about a plane parallel to the yz plane and passing through the center of the width direction of the vehicle body, relative to the structure associated with the left outer portion 60, left middle portion 62, and left inner portion 65. Therefore, its detailed description is omitted. The right outer portion 70, right outer bottom portion 71, right middle portion 72, right outer bottom portion 73, right inner bottom portion 74, right inner portion 75, and right inner bottom portion 76 are provided corresponding to the left outer portion 60, left outer bottom portion 61, left middle portion 62, left outer curved bottom portion 63, left inner curved bottom portion 64, left inner portion 65, and left inner bottom portion 66. Furthermore, provided that the required strength and rigidity can be ensured, the lower member 30 may be discontinuous and interrupted in the width direction in the central area or adjacent area of ​​the subframe 1 in the width direction, typically in the left inner part 65, the right inner part 75 and the part between them in the width direction, and may be divided into left and right sections.

[0041] In the lower member 30, at the left inner side 65, the right inner side 75, the portion between them in the width direction, the left middle part 62, and the right middle part 72, the upper end of the front longitudinal wall 42 abuts against the outer surface of the planar part 16 on the front side of the front transverse member 10 by arc welding or the like, thereby the first member 40 is joined with the front transverse member 10 to form an integral unit. And the upper end of the rear longitudinal wall 52 abuts against the outer surface of the planar part 16 on the rear side of the front transverse member 10 by arc welding or the like, thereby the second member 50 is joined with the front transverse member 10 to form an integral unit. Therefore, even when the input loads input to the lower member 30 and the input loads input to the left support member 80 or the right support member 90 are aligned in the same direction in the width direction, and the shear stress applied to the weld between the forward transverse member 10 and the lower member 30 increases, the occurrence of peeling failure of the weld can be suppressed, thereby ensuring the required weld strength. Furthermore, along the entire length in the width direction, the rear end of the front bottom wall 44 and the front end of the rear longitudinal wall 52 are welded along their boundary defined by mutual overlap using arc welding or the like, thereby joining the first member 40 and the second member 50 to form an integral lower member 30. Furthermore, in the left outer portion 60 and the right outer portion 70, a flange portion bending forward parallel to the horizontal plane is provided at the upper end of the front longitudinal wall 42, and a flange portion bending rearward parallel to the horizontal plane is provided at the upper end of the rear longitudinal wall 52. These flange portions are welded to the outer surface of the bottom plane portion 18 of the front transverse member 10 by means of arc welding or the like, while their upper surfaces abut against the outer surface of the bottom plane portion 18. Similar to the plane portion 16, the bottom plane portion 18 is a plane portion formed by partially recessing and flattening the bottom of the surrounding wall 12 of the front transverse member 10 through hydroforming or the like, and is parallel to the xy plane. The welded portions in the left outer portion 60 and the right outer portion 70 only need to have the auxiliary significance of having a shorter weld length and front-to-back span compared to the welded portions in the left inner portion 65, the right inner portion 75, the portion between them in the width direction, the left middle portion 62, and the right middle portion 72.

[0042] That is, in the front transverse member 10 and the lower member 30, the ends of the abutting members are welded together to form a single unit. Thus, the surrounding wall 12 in the front transverse member 10, together with the front longitudinal wall 42, front bottom wall 44, rear longitudinal wall 52, and rear bottom wall 54 in the lower member 30, cooperate to form a closed section SE2 in a longitudinal section obtained by cutting with a plane parallel to the yz plane. At least at the left middle portion 62 and the right middle portion 72, the upper ends of the front longitudinal wall 42 and the rear longitudinal wall 52 are defined as closed sections SE2 by abutting their inner surfaces against and welding them to the outer surface of the planar portion 16 of the front transverse member 10. This allows for a longer length in the longitudinal direction, ensuring a larger cross-sectional area. Here, the closed section SE2 is adjacent to the lower side of the closed section SE1 of the front transverse member 10, separated by its surrounding wall 12. The closed sections SE1 and SE2 form two stacked sections arranged adjacent to each other in the vertical direction. From the viewpoint that the closed section SE2 and closed section SE1 cooperate to increase the strength of the subframe 1 and improve the support rigidity of the suspension arms, it is preferable that the closed section SE2, i.e., the closed sections SE1 and SE2 arranged side by side, be positioned in at least a portion of either the left middle portion 62 or the right middle portion 72, where stress concentration tends to occur due to input loads applied from the suspension arms. Furthermore, stress is most likely to concentrate in the left middle portion 62 and the right middle portion 72 near the left inner side portion 65 and the right inner side portion 75; therefore, the closed section SE2, i.e., the closed sections SE1 and SE2 arranged side by side, are more preferably positioned corresponding to at least a portion of either the left inner curve bottom 64 or the right inner curve bottom 74. Moreover, from the viewpoint of further mitigating stress concentration by applying input loads from the suspension arms, the closed section SE2, i.e., the closed sections SE1 and SE2 arranged side by side, are more preferably arranged continuously in the width direction, extending over the left inner curve bottom 64 and the right inner curve bottom 74, and their corresponding left inner bottom 66 and right inner bottom 76. Furthermore, similarly, from the viewpoint of further mitigating stress concentration by applying input loads from the suspension arms, the closed section SE2, i.e., the closed sections SE1 and SE2 arranged side by side, is more preferably arranged continuously in the width direction, covering the left inner bend bottom 64 and the right inner bend bottom 74 and their corresponding left outer bend bottom 63 and right outer bend bottom 73. That is, in principle, drainage holes, paint discharge holes, etc., cannot be provided at the location of the closed section SE2 in the lower member 30. However, depending on the specifications of the subframe 1, if the degree of stress concentration between the left outer bend bottom 63 and the right outer bend bottom 73, the left inner bottom 66 and the right inner bottom 76, and the left inner bottom 66 and the right inner bottom 76 in the width direction is low, holes can be provided under the condition that the required strength and rigidity can be ensured.Similarly, when the left outer portion 60 and the right outer portion 70 have sufficient strength, holes or openings can also be provided in the left outer bottom portion 61 and the right outer portion 70. In addition, the dimensions of the closed section SE2, especially its length in the vertical direction, are also set in accordance with the positions of the left lower support portion and the right lower support portion supporting the suspension arm, increasing from the inner portion near the center to the outer portions on the left and right, especially at the left middle portion 62 and the right middle portion 72.

[0043] Additionally, the front transverse member 10 has a left support member 80 and a right support member 90 extending in the width direction at both ends on its upper side and engaging with the front transverse member 10 respectively. Furthermore, the left support member 80 and the right support member 90 may also engage at their ends in the width direction with portions protruding from the front transverse member 10 across the left side member 120 and the right side member 220.

[0044] The left support member 80 typically has a generally cap-shaped longitudinal section that opens downwards, obtained by stamping a flat plate such as a steel plate. It includes: a front longitudinal wall 82 with a left front through hole 88 extending through the left end of the front longitudinal wall 82 in the front-rear direction; a rear longitudinal wall 84 with a left rear through hole 89 extending through the left end of the rear longitudinal wall 84 in the front-rear direction and opposite the left front through hole 88 of the front longitudinal wall 82 on its rear side; and a top wall 86 connecting the front longitudinal wall 82 and the rear longitudinal wall 84. Furthermore, a nut member 320 is welded to the left front through hole 88.

[0045] Furthermore, the left support member 80 has a front flange 83 extending forward from the lower end of its front longitudinal wall 82 and a rear flange 85 extending rearward from the lower end of its rear longitudinal wall 84. The ends of the front flange 83 and the rear flange 85 are typically joined by welding, such as arc welding, while their inner surfaces abut against the outer surfaces of the inclined plane portion 14 of the front transverse member 10 and the top wall 136 of the upper left member 130 of the left side member 120. Thus, even when the input load input to the lower member 30 and the input load input to the left support member 80 or the right support member 90 are aligned in the same direction in the width direction, and the shear stress applied to the various welded portions between the front transverse member 10 and the left support member 80 increases, the occurrence of peeling failure of the relevant welded portions can be suppressed, thereby ensuring the required weld strength.

[0046] In the front transverse member 10 and the left support member 80, they are joined and integrated by welding the ends of their abutting portions together. Thus, the surrounding wall 12 in the front transverse member 10, together with the front longitudinal wall 82, rear longitudinal wall 84, and top wall 86 in the left support member 80, cooperate to form a closed section SE3 in a longitudinal section obtained by cutting with a plane parallel to the yz plane. From the viewpoint of increasing the strength of the subframe 1 and improving the support rigidity of the suspension arms, this closed section SE3 preferably has a portion that is vertically opposed to the closed section SE2 of the lower member 30, separated from the closed section SE1 of the front transverse member 10.

[0047] Regarding the structure associated with the right support member 90, since it is symmetrical to the structure associated with the left support member 80, a detailed description of it is omitted. However, the front longitudinal wall 82, the front flange 93, the rear longitudinal wall 84, the rear flange 85, the top wall 86, the left front through hole 88, the left rear through hole 89, and the closed section SE3 are provided correspondingly.

[0048] The rear transverse member 100 typically has a generally cap-shaped longitudinal section that opens downwards, obtained by stamping a flat plate component such as a steel plate. It has: a left front through-hole 103 and a right front through-hole 107 that correspondingly penetrate the left and right ends of its front longitudinal wall 102 in the longitudinal direction; and a left rear through-hole 104 and a right rear through-hole 108 that correspondingly penetrate the left and right ends of its rear longitudinal wall 106 in the longitudinal direction and are opposite to the left front through-hole 103 and right front through-hole 107 of the front longitudinal wall 102 on the rear side. The front longitudinal wall 102 and the rear longitudinal wall 106 are connected via a top wall 112. Furthermore, although not shown in the figures, guide components can be installed in the left front through-hole 103, right front through-hole 107, left rear through-hole 104, and right rear through-hole 108 to guide the lower arm or other suspension arms.

[0049] The rear transverse member 100 has a left widening portion 116 and a right widening portion 118 whose length in the front-rear direction gradually increases from the central portion 114, which is its width direction, outwards to the left and right. The left end of the left widening portion 116 and the right end of the right widening portion 118 are each cut-off portions, typically joined to the left member 120 and the right member 220 by welding, such as arc welding. However, the front end of the left end of the left widening portion 116 and the front end of the right end of the right widening portion 118 are offset forward by a greater offset length than their respective rear ends, and are located close to the front end faces of the recessed portions 136a, 236a and 156a, 256a of the left member 120 and the right member 220, which will be described later. As a result, the rear transverse member 100 can have a longer welding length relative to the left member 120 and the right member 220, and can be joined to the front transverse member 10 and the lower transverse member 30, which have greater strength and rigidity.

[0050] Typically, the left component 120 is formed by stamping a flat component such as a steel plate, and has an upper left component 130 and a lower left component 150 with a roughly U-shaped longitudinal section facing each other in the vertical direction. When viewed in the vertical direction, the left component 120 has a curved shape that bulges to the right. Alternatively, the left component 120 can also be made of a tubular component such as a steel pipe.

[0051] The upper left component 130 has: an outer wall 132 and an inner wall 134 that are opposite each other in the width direction and extend in the front-rear direction; and a top wall 136 connecting the outer wall 132 and the inner wall 134. The front portion 142 of the top wall 136 has a recessed portion 136a formed by recessing the middle portion (the central portion and its left and right portions) of the top wall 136 in the width direction downwards, and a rear cut-out portion 148 formed by cutting it into a generally arc shape at the rear end of the top wall 136. In the front portion 142, the two ends of the recessed portion 136a in the width direction form upward protrusions 144 and 144 that protrude upwards relative to the recessed portion 136a.

[0052] The lower left component 150 has a basic structure similar to flipping the upper left component 130 vertically, and includes: an outer wall 152 and an inner wall 154 that are opposite each other in the width direction and extend in the front-rear direction; and a bottom wall 156 connecting the outer wall 152 and the inner wall 154. The front portion 162 of the bottom wall 156 has a recessed portion 156a formed by recessing the middle portion of the bottom wall 156 in the width direction upwards, and the rear end of the bottom wall 156 has a rear cutout portion 168 formed by cutting it into a generally arc shape. In the front portion 162, the two ends of the recessed portion 156a in the width direction form downward protrusions 164 and 164 that protrude downwards relative to the recessed portion 156a.

[0053] The upper left component 130 and the lower left component 150 are joined together and formed as one piece by corresponding welding, typically by arc welding or the like, to form the left-side component 120 with a closed cross-section. Additionally, the plate thicknesses of the upper left component 130 and the lower left component 150 may be different.

[0054] In the front portions 142 and 162 of the upper left component 130 and the lower left component 150, the front ends of the recessed portions 136a and 156a, and the front ends of the outer wall 152 and the inner wall 154, are welded to the outer surface of the surrounding wall 12 of the front transverse member 10, which is mainly the rear side. The front transverse member 10 and the left component 120 are joined together as one unit. Here, since the front ends of the upper protrusion 144 and the lower protrusion 164 are separated from the outer surface of the surrounding wall 12 of the front transverse member 10 by gaps, the internal space of the left component 120 communicates with the outside through these gaps. Therefore, the contact length between the front ends of the recessed portions 136a and 156a, and the front ends of the outer wall 152 and the inner wall 154, and the outer surface of the surrounding wall 12 of the front transverse member 10, which is mainly the rear side, can be ensured to be longer. This ensures that the welding length between the front transverse member 10 and the left member 120 is longer, and that the paint can penetrate through the gap between the front ends of the upper protrusion 144 and the lower protrusion 164 and the outer surface of the surrounding wall 12 of the front transverse member 10, thereby ensuring good paint distribution capability for coating the left member 120.

[0055] The rear cutouts 148 and 168 are arranged opposite each other in the vertical direction at the rear ends of the upper left component 130 and the lower left component 150, and the sleeve component 310 is disposed in the rear cutouts 148 and 168 with its vertical ends protruding from the top wall 136 and the bottom wall 156 respectively, and is typically fixed by means of arc welding or the like.

[0056] Regarding the structure related to the right-side component 220, since it is symmetrical about a plane parallel to the yz plane and extending along a centerline in the longitudinal direction from the center of the width direction of the vehicle body, its detailed description is omitted. In the structure related to the right-side component 220, the following components are included: upper left component 130, outer wall 132, inner wall 134, top wall 136, recessed portion 136a, front portion 142, upper protrusion 144, left extension 146, rear cutout 148, lower left component 150, outer wall 152, and inner wall 120. 54. Correspondingly provided on the bottom wall 156, the recessed setting part 156a, the front part 162, the lower protrusion part 164, the left extension part 166, and the rear cutout part 168 are the upper right component 230, the outer wall 232, the inner wall 234, the top wall 236, the recessed setting part 236a, the front part 242, the upper protrusion part 244, the right extension part 246, the rear cutout part 248, the lower right component 250, the outer wall 252, the inner wall 254, the bottom wall 256, the recessed setting part 256a, the front part 262, the lower protrusion part 264, the right extension part 266, and the rear cutout part 268.

[0057] In the above structure, each component constituting the subframe 1 has an externally open portion, namely a first opening, a second opening, a third opening, a fourth opening, a fifth opening, and a sixth opening. Specifically, the first opening is the portion between the left front through hole 46 and the left rear through hole 56 of the lower component 30, opening its interior to the outside. The second opening is the portion between the right front through hole 48 and the right rear through hole 58 of the lower component 30, opening its interior to the outside. The third opening is the portion between the left front through hole 103 and the left rear through hole 104 of the rear transverse component 100, opening its interior to the outside. The fourth opening is the portion between the right front through hole 107 and the right rear through hole 108 of the rear transverse component 100, opening its interior to the outside. The fifth opening is the portion between the left front through hole 88 and the left rear through hole 89 of the left support component 80, opening its interior to the outside. The sixth opening is the part between the right front through hole 98 and the right rear through hole 99 of the right support member 90, which opens the interior to the outside.

[0058] Here, for the first opening, the second opening, the third opening, the fourth opening, the fifth opening, and the sixth opening, a first support part S1 is provided on the lower left front, a second support part S2 is provided on the lower right front, a third support part S3 is provided on the lower left rear, a fourth support part S4 is provided on the lower right rear, a fifth support part S5 is provided on the upper left front, and a sixth support part S6 is provided on the upper right front.

[0059] In detail, in the first support part S1 which is arranged corresponding to the first opening, the right pivot of the suspension arm (not shown in the figure) is fastened by fastening components such as fastening bolts via the left front through hole 46, the left rear through hole 56 and the nut member 320 provided in the lower member 30.

[0060] In the second support portion S2, which is arranged corresponding to the second opening, the left pivot of the suspension arm (not shown in the figure) is fastened by fastening components such as fastening bolts via the right front through hole 48, the right rear through hole 58 and the nut component 320 provided in the lower member 30.

[0061] In the third support portion S3, which is configured corresponding to the third opening, the right pivot of the suspension arm (not shown) is fastened by fastening components such as fastening bolts via the left front through hole 103, the left rear through hole 104 and the guide member provided in the rear transverse member 100.

[0062] In the fourth support portion S4, which is configured corresponding to the fourth opening, the left pivot of the suspension arm (not shown) is fastened by fastening components such as fastening bolts via the right front through hole 107, the right rear through hole 108 and the guide member provided in the rear transverse member 100.

[0063] In the fifth support portion S5, which is arranged corresponding to the fifth opening, the right pivot of the suspension arm (not shown in the figure) is fastened by fastening components such as fastening bolts via the left front through hole 88, the left rear through hole 89 and the nut component 320 provided in the left support member 80.

[0064] In the sixth support portion S6, which is arranged corresponding to the sixth opening, the left pivot of the suspension arm (not shown in the figure) is fastened by fastening components such as fastening bolts via the right front through hole 98, the right rear through hole 99 and the nut component 320 provided on the right support component 90.

[0065] The left and right pivots are suspension pivots located inside each other in the width direction, corresponding to the left and right pivots not shown in the diagram. They correspondingly define the positions of the left and right rear wheels (not shown in the diagram) in the length and width directions, and apply a relatively large external force to the subframe primarily in the width direction. Furthermore, a typical structure for these left and right pivots includes an insulating bushing component with a rubber portion bonded to a sleeve component through which the fastening member is inserted, and a spring constant that is small in the front-rear direction and large in the width direction. Additionally, the spring reaction force of the suspension springs (not shown in the diagram) can be applied to the specified left and right pair of the aforementioned left and right pivots.

[0066] Furthermore, the subframe 1 is also provided with a first mounting part A1 on the front left, a second mounting part A2 on the rear left, a third mounting part A3 on the front right, and a fourth mounting part A4 on the rear right.

[0067] In detail, the first mounting part A1 is configured corresponding to the sleeve member 310 of the left cutout 24 in the left extension 22 of the front transverse member 10. In this first mounting part A1, the left extension 22 is mounted on the vehicle body side by means of a subframe mounting member (not shown) mounted on the sleeve member 310 and fastened to the left rear frame by fastening members such as fastening bolts (not shown).

[0068] The third mounting part A3 is configured corresponding to the sleeve member 310 of the right cutout 28 in the right extension 26 of the front transverse member 10. In this third mounting part A3, the right extension 26 is mounted to the vehicle body side by means of a subframe mounting member (not shown) mounted on the sleeve member 310 and fastening members such as fastening bolts (not shown).

[0069] The second mounting portion A2 is correspondingly arranged with the sleeve components 310 of the rear cutout portions 148 and 168 in the left extension portions 146 and 166 of the left component 120. In this second mounting portion A2, the left extension portions 146 and 166 are mounted on the vehicle body side by means of a subframe mounting component (not shown) mounted on the sleeve component 310 and fastened to the left rear frame by fastening components such as fastening bolts (not shown).

[0070] The fourth mounting section A4 is correspondingly arranged with the sleeve members 310 of the rear cutouts 248 and 268 in the right extensions 246 and 266 of the right side member 220. In this fourth mounting section A4, the right extensions 246 and 266 are mounted to the vehicle body side by means of a subframe mounting member (not shown) mounted on the sleeve member 310 and fastened to the right rear frame by fastening members such as fastening bolts (not shown).

[0071] As a typical structure for the subframe mounting component, an insulating bushing component can be listed, which has a rubber portion bonded to a sleeve component through which the fastening component is inserted, and has a small spring constant in the vertical direction and a large spring constant in the width direction.

[0072] In the structure of this embodiment described above, the lower member 30, from the outside to the inside in the width direction, sequentially includes: outer portions 60 and 70, which are provided with lower support portions supporting the suspension components of the vehicle; middle portions 62 and 72, which are connected to the outer portions 60 and 70; and inner portions 65 and 75, which are connected to the middle portions 62 and 72. The middle portions 62 and 72 have: outer curved bottoms 63 and 73, which are connected to the bottoms 61 and 71 of the outer portions 60 and 70, and have a curved upward trajectory that does not descend from the bottoms 61 and 71 of the outer portions 60 and 70 as they move towards the inside; and inner curved bottoms 64 and 74, which are connected to the bottoms 66 and 76 of the inner portions 65 and 75, and have a curved downward trajectory that does not rise from the bottoms 66 and 76 of the inner portions 65 and 75 as they move towards the outside. The first transverse member 10 is used in the front-rear direction... The lower member 30 forms a first closed section SE1 in the cross section obtained by cutting with a plane defined in the vertical direction, and a second closed section SE2 in the cross section obtained by cutting with the same plane. The first closed section SE1 and the second closed section SE2 are arranged side by side in the vertical direction, separated by the wall portion 12 of the first closed section SE1 defined by the first transverse member 10, to form parallel closed sections SE1 and SE2. The parallel closed sections SE1 and SE2 are arranged to correspond to at least a portion of the outer curved bottoms 63 and 73 and the inner curved bottoms 64 and 74 in the middle portions 62 and 72. With such a structure, the necessary strength of the vehicle subframe 1 can be ensured and the degree of freedom in setting the support stiffness of the suspension component can be increased. It is possible to achieve a balance between its strength and stiffness and optimize them, and to set the desired stiffness and ensure the required strength.

[0073] Furthermore, in the structure of this embodiment, the parallel closed sections SE1 and SE2 must be configured to correspond to at least a portion of the inner curved bottoms 64 and 74. Thus, the necessary strength of the vehicle subframe 1 can be ensured by using the parallel longitudinal sections with the minimum range in the width direction, and the support rigidity of the suspension components can be appropriately set.

[0074] Furthermore, in the structure of this embodiment, the closed sections SE1 and SE2 are arranged side by side and continuously arranged in the width direction to cover one or both of the inner curved bottoms 64 and 74, the outer curved bottoms 63 and 73, and the bottoms 66 and 76 of the inner portions 65 and 75. This reduces stress concentration in the vehicle subframe 1 and eliminates local weak points, thereby further increasing its strength.

[0075] Furthermore, in the structure of this embodiment, the upper support members 80 and 90 are positioned opposite the lower member 30 in the vertical direction, separated by the first transverse member 10, and have an upper support portion for the suspension components supporting the vehicle. The upper support members 80 and 90 are provided to engage with the first transverse member 10. The upper support members 80 and 90 engage with an inclined surface 14 formed by recessing and tilting a portion of the cylindrical wall 12 of the first transverse member 10. As a result, the upper support members 80 and 90 can engage with each other in a state of reliably abutting against the inclined surface 14, and the occurrence of peeling damage at the joint can be suppressed.

[0076] Furthermore, in the structure of this embodiment, the pair of side members 120 and 220 each have: a pair of sidewalls 132 and 134, 232 and 234, which are opposite each other in the width direction; top walls 136 and 236, which connect the upper ends of the pair of sidewalls 132 and 134, 232 and 234 in the vertical direction to each other; and bottom walls 156 and 256, which are opposite the top walls 136 and 236 on the lower side, and connect the pair of sidewalls 132 and 234. The lower ends of 134, 232, and 234 in the vertical direction are connected to each other. The front portions 142 and 242 of the top walls 136 and 236 in the front-rear direction have: recessed portions 136a and 236a, formed by recessing the middle portion of the top walls 136 and 236 in the width direction downwards; and a pair of convex portions 144 and 244, formed by recessing the middle portion of the top walls 136 and 236 in the width direction... Both ends are formed to protrude upwards relative to the recessed portions 136a and 236a. In the top walls 136 and 236, the front ends of the recessed portions 136a and 236a engage with the first transverse member 10. The bottom walls 156 and 256 have the following in their front portions 162 and 262: recessed portions 156a and 256a, which are formed by recessing the middle portion of the bottom walls 156 and 256 in the width direction upwards; and a pair of convex shapes. The portions 164 and 264 are formed by making the two ends of the bottom walls 156 and 256 protrude downward relative to the recessed portions 156a and 256 in the width direction. In the bottom walls 156 and 256, the front ends of the recessed portions 156a and 256a engage with the first transverse member 10, thereby improving the coating distribution capability for coating a pair of side members 120 and 220 and ensuring their welding length to increase welding strength.

[0077] In addition, in this embodiment, the various nut components, sleeve components, and guide components are typically made of metals such as steel.

[0078] In addition, in this embodiment, the suspension arm can be any structure other than that exemplified in this embodiment, as long as it has the same function.

[0079] In addition, in this embodiment, the subframe 1 may not be a floating type, but rather a rigid type mounted on the vehicle body.

[0080] Furthermore, the types, shapes, arrangements, and numbers of components of the present invention are not limited to the embodiments described above. Of course, appropriate changes can be made without departing from the spirit of the invention, and the constituent elements can be appropriately replaced with elements that have the same effect.

[0081] As described above, in this invention, by realizing a structure that improves the degree of freedom in setting its rigidity, a vehicle subframe can be provided that optimizes its strength and rigidity while achieving a balance between them, appropriately setting the rigidity, and ensuring the necessary strength. Therefore, based on its universal and general nature, it is expected to be widely applied in the field of subframes for moving bodies such as vehicles.

Claims

1. A vehicle subframe, said vehicle subframe comprising: A cylindrical first transverse member that extends in the width direction of the vehicle; A second lateral member is opposite to the first lateral member in the longitudinal direction of the vehicle and extends in the width direction; A pair of side members, which are opposite each other in the width direction and extend respectively in the front-rear direction, and respectively engage with the first transverse member and the second transverse member; as well as The lower member extends along the width direction on its lower side in the vertical direction of the vehicle relative to the first transverse member, and engages with the first transverse member. The lower component, from the outer side to the inner side in the width direction, sequentially comprises: an outer portion having a lower support portion for supporting the suspension components of the vehicle; a middle portion connected to the outer portion; and an inner portion connected to the middle portion. The middle portion has: an outer curved bottom that connects to the bottom of the outer portion and curves upward from the bottom of the outer portion without descending as it moves toward the inner side; and an inner curved bottom that connects to the bottom of the inner portion and curves downward from the bottom of the inner portion without ascending as it moves toward the outer side. The first transverse member has a first closed section in the cross-section obtained by cutting with a plane defined by the front-back direction and the vertical direction. The lower component forms a second closed section in the cross-section obtained by cutting with the plane. The first closed section and the second closed section are arranged side by side in the vertical direction, separated by the wall portion of the first closed section defined by the first transverse member, to form a parallel closed section. The parallel closed sections are configured to correspond to at least a portion of the outer curved bottom and the inner curved bottom in the middle portion. The pair of side members each have: a pair of sidewalls facing each other in the width direction; a top wall connecting the upper ends of the pair of sidewalls in the vertical direction; and a bottom wall facing the top wall on the lower side and connecting the lower ends of the pair of sidewalls in the vertical direction. The front portion of the top wall in the front-rear direction has: a recessed portion formed by recessing the middle portion of the top wall in the width direction toward the lower side; and a pair of convex portions formed by protruding the two ends of the top wall in the width direction toward the upper side relative to the recessed portion. In the top wall, the front end of the recessed portion abuts against the outer surface of the rear side of the first transverse member. The bottom wall has, on its front side, a recessed portion formed by recessing the middle portion of the bottom wall in the width direction toward the upper side; and a pair of convex portions formed by protruding the two ends of the bottom wall in the width direction toward the lower side relative to the recessed portion. In the bottom wall, the front end of the recessed portion abuts against the outer surface of the rear side of the first transverse member.

2. The vehicle subframe according to claim 1, wherein, The parallel closed sections must be configured to correspond to at least a portion of the inner curved bottom.

3. The vehicle subframe according to claim 1 or 2, wherein, The parallel closed sections are continuously arranged in the width direction to extend over one or both of the inner curved bottom, the outer curved bottom, and the bottom of the inner portion.

4. The vehicle subframe according to claim 1 or 2, wherein, The upper support member is positioned above the lower member in the vertical direction, across the first transverse member, and has an upper support portion for supporting the suspension components of the vehicle. The upper support member is configured to engage with the first transverse member and engages with an inclined face formed by recessing and tilting a portion of the cylindrical wall of the first transverse member.

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