Automotive subframe structure

Abstract

To provide a sub-frame structure of an automobile capable of enhancing strength of an arm support bracket provided on an outer surface of a side member in a parallel cross-shaped sub-frame, as well as, enhancing support rigidity of the arm.SOLUTION: In a sub-frame structure of an automobile according to the present invention, a base portion 30d of an arm support bracket 30 having a U-shaped cross section is welded to each of outer surfaces of side cross members 24, 26 at a position in the vicinity of a connection portion 20a of a cross member 20. An arm support bracket 30 includes opposing side surface portions 30a and 30b, which support a pivot portion of a trailing arm 6, in a manner of sandwiching it from both sides. A part of the open end portion 20a of the cross member 20 is formed with a cutout portion 20g open outward in a vehicle width direction. The cutout portion 20g is welded to at least one of the opposing side surface portions of the arm support bracket at a position spaced downwardly or upwardly from the base portion 30d of the arm support bracket.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to a subframe structure for an automobile, and in particular to a subframe structure for an automobile formed in a criss-cross shape by a pair of side members extending in the fore-and-aft direction of the vehicle, and front and rear cross members extending in the vehicle width direction so as to connect the pair of side members to each other. [Background technology]

[0002] Conventionally, a multi-link suspension device is known that has five I-links, each of which has a vehicle body side end connected to a subframe attached to the vehicle body and a wheel side end connected to a wheel support that supports the wheel. A known subframe for such a multi-link suspension is one that has a frame formed in a lattice shape with a pair of side members and front and rear cross members. In such a subframe, a structure is known in which the front and rear cross members are joined by abutting against the inner side surfaces of the side members in the vehicle width direction (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2006-347337 [Patent Document 2] DE 102010030292 Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of crisscross subframe, the pair of side members and the front and rear cross members are each closed cross-section bodies formed from plate-like members, and the left and right open ends of the cross members extending in the vehicle width direction are typically abutted against the inner side surfaces of the side members in the vehicle width direction and joined together.

[0005] In such a parallel-cross subframe, support brackets for each arm (each link) are provided on the outer surface of the side members, and it is necessary to increase the strength of these brackets as well as the support rigidity of the arms.

[0006] Therefore, the present invention has been made to solve the above-mentioned problems, and has an object to provide a subframe structure for an automobile that can increase the strength of an arm support bracket provided on the outer surface of a side member in a lattice-shaped subframe, and also increase the supporting rigidity of the arm. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention provides an automobile subframe structure formed in a grid shape by a pair of side members extending in the fore-and-aft direction of the vehicle on both the left and right sides in the vehicle width direction, and a front cross member and a rear cross member extending in the vehicle width direction so as to connect the pair of side members to each other, wherein the cross members constituting the front cross member and / or the rear cross member are joined so that at least a portion of their left and right open ends abut against the inner side surfaces of the pair of side members in the vehicle width direction, and the outer surfaces of the pair of side members have a groove at a position near the joint portion of the cross member to the side member. And the lower side of the side member A base of an arm support bracket having a U-shaped cross section is welded to the cross member, the arm support bracket including opposing side portions that sandwich and support the pivot portion of the suspension arm from both sides, and a cutout portion that opens outward in the vehicle width direction is formed in a part of the open end of the cross member, and the cutout portion is The arm support bracket is formed so as to surround at least one of the side surfaces and the rear surface of the arm support bracket, The arm support bracket is characterized in that it is welded to at least one of the opposing side portions of the arm support bracket at a position spaced downward from the base of the arm support bracket.

[0008] According to the present invention configured as described above, in addition to welding the base of the arm support bracket to the side member, the arm support bracket is also welded to the cross member at a position spaced downward or upward. This improves the strength against bending forces applied to the portion near the base, and accordingly improves the bending rigidity of the bracket, so that the pivot position of the arm does not move. Therefore, in the lattice-shaped subframe, the strength of the arm support bracket provided on the outer surface of the side member can be increased, and the support rigidity of the arm can be increased.

[0009] In the present invention, preferably, a bulge that bulges downward is formed in a portion of the open end of the cross member, and a notch is formed in this bulge. According to the present invention configured in this manner, it is possible to more effectively increase the strength of the arm support bracket provided on the outer surface of the side member and to increase the supporting rigidity of the arm.

[0010] In the present invention, the cutout portion of the cross member is preferably welded to and abuts against at least one of the side portions and the rear portion of the arm support bracket so as to surround the cutout portion. According to the present invention configured in this manner, it is possible to more effectively increase the strength of the arm support bracket provided on the outer surface of the side member and to increase the supporting rigidity of the arm. Effect of the Invention

[0011] According to the subframe structure for an automobile of the present invention, in the parallel-cross subframe, the strength of the arm support bracket provided on the outer surface of the side member can be increased and the supporting rigidity of the arm can be increased. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of a rear suspension assembly of an automobile to which an automobile subframe according to an embodiment of the present invention is applied. [Diagram 2] FIG. 2 is a top view of the rear suspension assembly shown in FIG. [Diagram 3] FIG. 2 is a rear view of the rear suspension assembly shown in FIG. [Figure 4] FIG. 2 is a top view of the rear suspension on the left side of the vehicle according to the present embodiment. [Diagram 5] FIG. 5 is a left side view of the rear suspension of FIG. 4. [Figure 6] FIG. 5 is a front view of the rear suspension of FIG. [Figure 7] 1 is a perspective view showing the structure of a front cross member on the left side of the vehicle of the automobile subframe according to the present embodiment and the joining structure to a side cross member, as viewed diagonally from the front. FIG. [Figure 8] 8 is a perspective view of the structure of a portion similar to that of FIG. 7, as viewed obliquely from the rear of the vehicle. [Figure 9] 1 is an oblique view of the structure of a front cross member on the left side of the vehicle of an automobile subframe according to this embodiment and the joining structure to a side cross member, as viewed from diagonally below and behind the vehicle. [Figure 10] 10 is a perspective view of the structure of a portion similar to that of FIG. 9, as viewed from below and obliquely rearward of the vehicle. [Figure 11] FIG. 2 is a plan view showing an upper member of the front cross member according to the present embodiment. [Figure 12] FIG. 2 is a perspective view showing an upper member of the front cross member according to the present embodiment. [Figure 13] FIG. 2 is a side view showing an upper member of the front cross member according to the present embodiment. [Figure 14] FIG. 4 is a plan view showing a lower member of the front cross member according to the present embodiment. [Figure 15] FIG. 2 is a perspective view showing a lower member of the front cross member according to the present embodiment. [Figure 16] FIG. 4 is a side view showing a lower member of the front cross member according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a subframe structure for an automobile according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, the overall configuration of an automobile subframe structure according to an embodiment of the present invention will be described with reference to Figures 1 to 3. Figures 1 to 3 show an embodiment in which an automobile rear wheel suspension device 1 (hereinafter simply referred to as a rear suspension) according to an embodiment of the present invention is applied to the rear wheels on both the left and right sides of an automobile, Figure 1 is a perspective view of an automobile rear suspension assembly to which the automobile subframe structure according to the embodiment of the present invention is applied, Figure 2 is a top view of the rear suspension assembly shown in Figure 1, and Figure 3 is a rear view of the rear suspension assembly shown in Figure 1. The automobile (vehicle) of this embodiment is a rear-wheel drive vehicle having an engine mounted in an engine room at the front of the vehicle body (not shown), a differential disposed at the rear of the vehicle body, and rear wheels 2 driven by an axle (not shown). As shown in FIGS. 1 to 3, a rear suspension assembly of a rear wheel suspension device 1 includes a subframe 3 to which a pair of left and right rear suspensions are connected.

[0015] First, the general configuration of the rear suspension will be described. The rear suspension of this embodiment is of a multi-link type in which a wheel support 10 of a rear wheel 2 is connected to a vehicle body so as to be movable by five independent I-links 4 to 8. The rear suspension device 1 includes a front upper link (upper arm) 4 and a rear leading link (leading arm) 5 that virtually constitute an upper arm, a front trailing link (trailing arm) 6 and a rear lower link (lower arm) 7 that virtually constitute a lower arm, and a toe control link (toe control arm) 8 that restricts the rotational displacement of the rear wheel 2 around a virtual kingpin axis IK (see FIG. 5). The upper arm 4, the leading arm 5, the trailing arm 6, and the lower arm 7 each swing up and down around a connecting portion (44, 52, 60, 68) on the vehicle body side, so that the wheel support 10 and the rear wheel 2 stroke up and down along a predetermined trajectory.

[0016] In addition, a shock absorber 16 is provided that includes a coil spring 12 and a damper 14 to allow such a stroke of the rear wheel 2 while at the same time applying a predetermined biasing force and damping force. The shock absorber 16 has a vertically long cylindrical shape in which the coil spring 12 and the damper 14 are arranged approximately coaxially, and its upper end is attached to the vehicle body. The lower end of the shock absorber 16 is pivotally attached to the lower arm 7. Further, a stabilizer bar 18 is rotatably attached to the suspension device 1 so as to extend so as to connect the left and right lower arms 7 together.

[0017] Next, a schematic configuration of the subframe 3 according to this embodiment will be described. The subframe 3 is mainly formed by combining four steel plate frames into a rectangular frame / cross shape in a plan view, and includes a front cross member (front cross member) 20 and a rear cross member (rear cross member) 22 which each extend in the vehicle width direction, and a pair of side cross members (side members) 24, 26 which extend in the fore-and-aft direction of the vehicle body on both the left and right sides so as to connect the left and right ends of the front and rear cross members together.

[0018] First, the front cross member 20 in this embodiment is configured as a hollow body with a closed cross section formed by joining upper and lower plate-shaped members 120, 220 together, and extends in a straight line in the vehicle width direction when viewed from above the vehicle, with its left and right end portions / open ends 20a in the vehicle width direction being joined to the front ends of the left and right side cross members 24, 26, respectively. As shown in Figs. 1 and 2, when viewed in the vehicle longitudinal direction, the front cross member 20 is formed in an arch shape that is curved overall so that the longitudinal center portion is located higher than both left and right ends.

[0019] 2, when viewed from above the vehicle, the front cross member 20 has a central portion in the longitudinal direction that extends linearly and extends such that the front-to-rear length increases from the central portion toward both left and right ends 20a. More specifically, when viewed from above, the front end edge of the front cross member 20 extends linearly in the vehicle width direction, and the central portion of the rear end edge extends linearly in the vehicle width direction while curving so that both left and right sides of the rear end edge extend in the vehicle width direction and are located rearward of the central portion. The portions 20b whose front-to-rear length is expanded on both the left and right sides include open ends 20a with a closed cross section, and as shown in Figures 1 and 2, each open end 20a is joined (welded) to a location on the front end side of each of the side members 24, 26, respectively.

[0020] Further, at both left and right ends of the front cross member 20, in positions close to the joints 20a with the side cross members 24, 26 and on the upper and lower sides of the side cross members 24, 26, there are provided mounting seats (pivot support portions) 28 for the upper arm 4 and mounting seats (pivot support portions) 30 for the trailing arm 6, respectively (see Figs. 4 to 6). The mounting seats 28 on both the left and right sides are connected to the end portions of the upper arm 4 facing the vehicle body, and the mounting seats 30 on both the left and right sides are connected to the end portions of the trailing arm 6 facing the vehicle body.

[0021] Next, the rear cross member 22 in this embodiment has a rear cross member main body 21 that constitutes part of the criss-cross shaped subframe 3, and left and right rear cross member lower portions (hanging portions) 23 that mainly serve to support the lower arms, and is joined to the front end locations of the left and right side cross members 24, 26 at both left and right end portions / open ends 22a in the vehicle width direction when viewed from above the vehicle. The rear cross member main body 21 is configured as a hollow body with a closed cross section formed by joining front and rear plate-like members 121, 221 together, and when viewed from above the vehicle, its longitudinal center portion is formed in a substantially straight line, and enlarged portions 22b are formed on both the left and right sides in the vehicle width direction, the enlarged portions 22b being enlarged in length toward both ends. The open ends 22a of these enlarged portions 22b are joined (welded) to the rear end portions of the side cross members 24, 26, respectively. In this embodiment, this configuration ensures the rigidity of the rear cross member 22 itself and the subframe 3. As shown in FIG. 3, the rear cross member body 21 is formed in an arch shape that is curved overall so that the longitudinal center portion is located lower than both left and right ends when viewed from the rear of the vehicle.

[0022] The rear cross-member lower portion 23 is configured as a hollow body with a closed cross section formed by joining together three front and rear plate-like members 123, 124, 223 (see FIG. 5). The rear cross-member lower portion 23 is joined (welded) to the lower part of the rear cross-member main body 21 at a position inward in the vehicle width direction of and adjacent to the side cross members 24, 26, and extends to the outer sides of the side cross members 24, 26 in the vehicle width direction and is joined (welded) to the lower and outer surfaces of the side cross members 24, 26.

[0023] At the left and right ends of the rear cross member 22, above and below the side cross members 24, 26, there are provided mounting seats (pivot shaft support portions) 32 for the leading arm 5 and mounting seats (pivot shaft support portions) 34 for the lower arm 7 (see Figures 4 and 5). The mounting seats 32 on both the left and right sides are connected to the vehicle body side ends of the leading arms 5, and the mounting seats 34 on both the left and right sides are connected to the vehicle body side ends of the lower arms 7. In this embodiment, the lower end of the rear cross member lower portion 23 is formed as a mounting seat 34 for the lower arm 7, and the upper end of the rear cross member lower portion 23 is formed as part of the mounting seat 32 for the leading arm 5 (see Figures 4 and 5).

[0024] Further, mounting seats (pivot support portions) 36 for the toe control arms 8 are provided on the rear surface 23b of the rear cross-member lower portion 23 at positions inward in the vehicle width direction of each of the side cross members 24, 26 when viewed from above and at positions diagonally below each of the side cross members 24, 26 when viewed from behind. The mounting seats 36 on both the left and right sides are connected to the vehicle body side ends of the toe control arms 8, respectively.

[0025] Next, the left and right side cross members 24, 26 are each curved so that their longitudinal center portions are located inward in the vehicle width direction compared to the front and rear ends when viewed from above the vehicle, and extend obliquely downward toward the front of the vehicle from the rear end to the front end when viewed from the side (see FIG. 5). The above-mentioned mounting seats 28, 30 are provided in the front portions of these side cross members 24, 26, and the above-mentioned mounting seats 32, 34 are provided in the rear portions thereof.

[0026] Additionally, the side cross members 24, 26 are provided with elastic mounts 38, 40 for elastically supporting the entire subframe 3 on the vehicle body, and these elastic mounts 38, 40 are provided at a total of four locations, at the front and rear ends of each side cross member 24, 26. Each elastic mount 38, 40 has a cylindrical shape with an axis in the up-down direction, and is attached to a recess formed in each side cross member 24, 26. In each side cross member 24, 26, each elastic mount 38, 40 is disposed so that, when viewed from above the vehicle, a straight line connecting the elastic mount 38 at the front end and the elastic mount 40 at the rear end is substantially parallel to the center line CL (shown only in FIG. 2) in the fore-and-aft direction of the vehicle body.

[0027] Each elastic mount 38, 40 has a predetermined gap called a "sugiri" and is formed so that its stiffness (characteristics indicated by the magnitude of the load (N) that produces a predetermined amount of deflection (mm)) differs in the front-rear direction and the left-right direction with respect to its axis. Each elastic mount 38, 40 is attached to the side cross members 24, 26 so that its stiffness in the vehicle width direction is greater than its stiffness in the vehicle front-rear direction.

[0028] Next, the arrangement of the arms 4-8 and the arm support structure of the subframe 3 for the rear suspension device 1 on the left side of the vehicle will be described with reference to Figures 4 to 6. Figure 4 is a top view of the rear suspension on the left side of the vehicle according to this embodiment, Figure 5 is a left side view of the rear suspension in Figure 4, and Figure 6 is a front view of the rear suspension in Figure 4. The rear suspension device 1 on the right side of the vehicle has the same structure as the rear suspension 1 on the left side of the vehicle, so its description will be omitted below.

[0029] 4 to 6, the upper arm 4 has an end portion on the vehicle body side connected to the pivot shaft support portion 28 of the side cross member 24 (26) via an elastic bush (a rubber bush, hereinafter referred to as "bush") 42. The upper arm 4 extends at a rearward inclination so as to be gradually positioned rearward from a connecting portion 44 on the vehicle body side toward the outside in the vehicle width direction when viewed from above the vehicle. At a connecting portion 46 on the wheel side, the end portion on the wheel side of the upper arm 4 is connected to the wheel support 10 via a bush 48.

[0030] The pivot support portion 28 of the upper arm 4 is composed of two opposing plate-shaped members whose bases are welded to the side cross members 24, 26, and these plate-shaped members support the pivot portion of the upper arm 4 on the vehicle body side (see Figures 4 to 6).

[0031] Next, the leading arm 5 has its end on the vehicle body side connected to the pivot shaft support portion 32 via a bush 50. When viewed from above the vehicle, the leading arm 5 extends with a forward inclination so as to be gradually positioned forward from the connecting portion 52 on the vehicle body side toward the outside in the vehicle width direction. At the connecting portion 54 on the wheel side, the end of the leading arm 5 on the wheel side is connected to the wheel support 10 via a bush 56.

[0032] The pivot support portion 32 of the leading arm 5 is composed of two opposing plate-shaped members, one of which in this embodiment is the upper end portion of the rear cross member lower portion 23 described above, and the other is a plate-shaped member whose base is welded to the side cross members 24, 26 (see Figures 4 and 5).

[0033] In this manner, the two upper arms 4, 5 are disposed so as to approach each other toward the outside of the vehicle body when viewed from above the vehicle. In this embodiment, pillow ball joints are used for the bushes 42, 50 on the vehicle body side and the bushes 48, 56 on the wheel side.

[0034] Next, the trailing arm 6 has its end on the vehicle body side connected to the pivot shaft support portion 30 via a bush 58. The trailing arm 6 extends at a rearward incline so as to be gradually positioned rearward from the vehicle body side connecting portion 60 toward the outside in the vehicle width direction when viewed from above the vehicle. At the wheel side connecting portion 62, the wheel side end of the trailing arm 6 is connected to the wheel support 10 via a bush 64.

[0035] The pivot support portion 30 of the trailing arm 6 is an arm support bracket 30 with a U-shaped cross section formed by welding two opposing L-shaped side members together, and the pivot portion on the vehicle body side of the trailing arm 6 is supported by the opposing side portions (see Figures 5 and 6).

[0036] Next, the lower arm 7 has its end on the vehicle body side connected to the pivot shaft support portion 34 via a bush 66. The lower arm 7 extends with a forward inclination so as to be gradually positioned forward from the connecting portion 68 on the vehicle body side toward the outside in the vehicle width direction when viewed from above the vehicle. At the connecting portion 70 on the wheel side, the end of the trailing arm 6 on the wheel side is connected to the wheel support 10 via a bush 72.

[0037] The pivot support portion 34 of the lower arm 7 is the lower end portion of the rear cross member lower portion 23 described above, and the pivot portion of the lower arm 7 on the vehicle body side is supported by front and rear plate-shaped members 123, 223 at the lower end portion (see Figure 5).

[0038] In this way, the two lower arms 6, 7 are positioned so that they approach each other outward in the vehicle width direction when viewed from above the vehicle. Due to this positioning mainly, when braking force from the road surface G (see Figure 3) acts on the rear wheels 2 during braking, for example, the rear wheels 2 are geometrically toe-in as they displace toward the rear of the vehicle (longitudinal force compliance steer), and when a lateral force is applied to the rear wheels 2 during turning, the rear wheels 2 change their toe-in direction mainly due to the flexing of the bushes 56, 64 of the lower arms 6, 7 (lateral force compliance steer). In this embodiment, pillow ball joints are used for the bushes 58, 66 on the vehicle body side and the bushes 64, 72 on the wheel side.

[0039] Next, the toe control arm 8 has its end on the vehicle body side connected to the pivot shaft support portion 36 via a bush 74. When viewed from above the vehicle, the toe control arm 8 extends with a forward inclination so as to be gradually positioned forward from the connecting portion 76 on the vehicle body side toward the outside in the vehicle width direction. At the connecting portion 78 on the wheel side, the end of the trailing arm 6 on the wheel side is connected to the wheel support 10 via a bush 80. In this embodiment, a pillow ball joint is used for the bush 74 on the vehicle body side and the bush 80 on the wheel side.

[0040] The pivot support portion 36 of the toe control arm 8 has an arm support bracket 37 with a U-shaped cross section that is integrally formed by press molding. The pivot support portion 36 is composed of a support portion of this arm support bracket 37 and a support portion on the side of the rear cross member lower portion 23 that is formed at a position opposing each other in the front-rear direction, and the pivot portion on the vehicle body side of the control arm 8 is supported by these two opposing support portions (see Figures 3 and 5).

[0041] Here, in the rear suspension, a virtual kingpin axis IK (see FIG. 5) is formed that vertically connects the intersection of the virtual extension line of the upper arm 4 and the virtual extension line of the leading arm 5 and the intersection of the virtual extension line of the trailing arm 6 and the virtual extension line of the lower arm 7. This virtual kingpin axis is the instantaneous rotation center of the rear wheel 2 in the steering direction (toe direction).

[0042] Next, the configuration of the wheel support 10 and the mounting configuration of each arm will be described with reference to Figs. First, as shown in FIGS. 4 to 6, the wheel support 10 has a hub 82 attached to its center, and is formed with an opening 84 through which an axle (not shown) passes. Further, the wheel support 10 is formed with a front vertical wall portion 86 that protrudes inward in the vehicle width direction at a portion closer to the front of the opening 84, and the upper arm 4, the leading arm 5 and the trailing arm 6 are connected to this front vertical wall portion 86. As shown in Fig. 6, a reinforcing rib 86a is formed on the outer edge of this front vertical wall portion 86. Further, the wheel support 10 is formed with a lower vertical wall portion 88 that protrudes inward in the vehicle width direction below the opening 84, and the lower arm 7 is connected to this lower vertical wall portion 88. Furthermore, the wheel support 10 has a rear vertical wall portion 90 that protrudes inward in the vehicle width direction at a portion of the wheel support 10 that is rearward of the opening 84, and the toe control arm 8 is connected to this rear vertical wall portion 90.

[0043] Next, the joining structure of the front cross member 20 to the side cross members 24, 26 will be described with reference to Figures 7 to 10. Figure 7 is a perspective view showing the structure of the front cross member on the left side of the vehicle of the subframe of an automobile according to this embodiment and the joining structure to the side cross member, as viewed obliquely from the front, Figure 8 is a perspective view of the structure of a portion similar to that of Figure 7, as viewed obliquely from the rear of the vehicle, Figure 9 is a perspective view of the structure of the front cross member on the left side of the vehicle of the subframe of an automobile according to this embodiment and the joining structure to the side cross member, as viewed obliquely from below the rear of the vehicle, and Figure 10 is a perspective view of the structure of a portion similar to that of Figure 9, as viewed obliquely from below the rear of the vehicle. First, as shown in Figures 7 to 10, the front cross member 20 is a hollow body with a closed cross section formed by welding an upper plate-like member (upper member) 120 and a lower plate-like member (lower member) 220 together, and the enlarged portion (portion near both left and right ends 20a) 20b in the front-rear length including the left and right open ends 20a has a polygonal closed cross section having approximately four corners (see Figures 13 and 16). These left and right open ends (openings open in the vehicle width direction on both left and right sides) 20a are respectively joined to the outer surface of the side cross member 24 (26). Also, a part of the left and right open ends 20a is respectively joined to the inner surface of the side cross member 24 (26) so as to abut against the inner surface of the side cross member 24 (26).

[0044] 7 and 8, in the vicinity 20b of both the left and right ends 20a, a protrusion 20c is formed at a corner of the rear edge thereof, the protrusion 20c extending along the rear edge (along the longitudinal direction of the front cross member 20) and protruding upward. In this embodiment, the protrusion 20c is formed on the upper member 120. This protruding portion 20c further has an extension portion 20d that extends outward in the longitudinal direction of the front cross member 20 further than the other portions of the open end portion 20a. In other words, the protruding portion 20c has an extension portion 20d that extends outward in the vehicle width direction further than the other portions of the open end portion 20a, relative to the position of the inner surface of the side cross member 24 (26) when viewed from above.

[0045] In this embodiment, such an extension 20d is joined to the upper surface of the side cross member 24 (26). The joining of the extension 20d is configured by welding the front and rear portions 20e of the extension 20d to the outer surface of the side cross member 24 (26) along a welding line W indicated by the symbol W in the drawings, as shown in Fig. 7 and Fig. 8. More specifically, the front and rear portions 20e of the extension 20d are the open end 20a of the upper member 120, and are portions formed in a curved shape so as to follow the shape of the outer surface of the side cross member 24 (26), and these front and rear curved portions 20e are welded to the upper surface of the side cross member 24 (26). Furthermore, on the outer surface of the side cross member 24 (26), a plate-like member on one side of the pivot support portion 28 of the upper arm 4 is welded to a position facing the extension portion 20d (see weld line W).

[0046] As a modified example, such protrusions 20c and extensions 20d may be formed on the lower member 220 and joined to the outer surface of the side cross member 24 (26), i.e., in this case, the lower surface of the side cross member 24 (26), in the same manner as the upper member 120. In this case, it is preferable that the protrusions (20c) on the lower member 220 protrude downward.

[0047] Next, as shown in Figures 7, 9 and 10, a bulging portion 20f that bulges downward is formed near the corner of the front edge and lower edge of the open end 20a of the front cross member 20, and a substantially L-shaped notch 20g is formed in this bulging portion 20f so as to conform to the outer shape of the arm support bracket 30 of the trailing arm 6 (see Figure 16). Here, the arm support bracket 30 of the trailing arm 6 is an arm support bracket 30 with a U-shaped cross section formed by welding two opposing L-shaped side members to each other, and has side portions 30a, 30b that face each other in the front-rear direction and a rear surface portion 30c on the inner side in the vehicle width direction. The arm support bracket 30 has a base portion 30d that is joined (welded) to the side cross members 24, 26, and the pivot portion on the vehicle body side of the trailing arm 6 is journaled by the two opposing side portions (see Figures 7, 9 and 10).

[0048] In this embodiment, the cutout portion 20g of the bulging portion 20f is welded to one of the two opposing side surface portions 30a of the arm support bracket 30 (see welding line W) as shown in Figures 9 and 10, and is also welded to the rear surface portion 30c of the bracket 30 (see welding line W) as shown in Figures 7 and 9. Also, in this embodiment, the cutout portion 20g is welded to one of the two L-shaped cross-section members constituting the arm support bracket 30 (see welding line W) as shown in Figure 7.

[0049] Thus, in this embodiment, a portion of the open end 20a of the front cross member 20 is welded to surround one of the side portions 30a and the rear portion 30c of the bracket 30 by forming a bulge portion 20f and a cutout portion 20g in the lower member 220. Alternatively, the cutout portion 20g may be formed as a U-shaped opening so as to surround both side surfaces 30a, 30b and the rear surface 30c of the bracket 30, and the opening may be butted together and welded.

[0050] Next, as shown in Figures 9 and 10, an outer edge portion 20h is formed in the open end 20a of the lower member 220, in the rear portion of the above-mentioned bulge portion 20f, so as to be shaped to conform to the shape of the outer surface of the side cross member 24 (26), and this outer edge portion 20h is welded to the underside of the side cross member 24 (26) along the weld line W indicated by the symbol W in the figures.

[0051] Here, the arm support bracket 30 has its base portion 30d extending in a U-shape welded to the lower side of the side cross member 24 (26) (see weld line W). In this embodiment, the lower member 220 is formed with a bulging portion 20f that bulges downward and a cutout portion 20g, so that the lower member 220 is welded to the side portion 30a of the bracket 30 at a position spaced downward from the base portion 30d of the arm support bracket 30, as shown in Figs. 9 and 10. As a result, as shown in Fig. 10 in particular, a space S is formed between the base portion 30d, the downward bulging portion 20f, and the lower surface of the side cross member 24 (26), thereby increasing the arm support rigidity of the arm support bracket 30. That is, the space S formed mainly by the bulging portion 20f is formed so that the outer edge portion 20h supports the bracket 30 from the side via the bulging portion 20f on the front side thereof. In particular, the strength against bending forces applied to the portion of the arm support bracket 30 near the base portion 30d is improved, and the bending rigidity of the bracket 30 is improved accordingly, so that the pivot position of the trailing arm 6 does not wobble.

[0052] As a modified example, such a bulge 20f may be formed in the upper member 120 and welded to an arm pivot support portion (for example, the pivot support portion 28 of the upper arm 4) in the same manner as the lower member 220. In this case, it is preferable that the bulge (20f) in the upper member 120 bulges upward. As a modified example, the bulge 20f and the cutout 20g may be welded to a support portion of an arm other than the trailing arm 6 (for example, the upper arm 4 or the leading arm 5) as described above. As a modified example, the structure of the front cross member 20 may be applied to a rear cross member.

[0053] Next, as shown in Figures 11 to 13, the upper member 120 of the front cross member 20 is formed by pressing a plate-shaped steel plate member, and has both end portions 20a and front and rear expanded portions 20b described above, and the upper member 120 is also formed with the protrusions 20c, extensions 20d, and front and rear curved portions 20e described above.

[0054] Next, as shown in Figures 14 to 16, the lower member 220 of the front cross member 20 is formed by pressing a plate-shaped steel plate member and has both end portions 20a described above, and the lower member 220 is formed with the bulge portion 20f, cutout portion 20g, and outer edge portion 20h described above.

[0055] Next, the effects of this embodiment and the modified example will be described. According to this embodiment and its modified example, the cross members constituting the front cross member 20 and / or the rear cross member 22 are joined so that at least a portion of the left and right open ends 20a (22a) thereof abut against the vehicle width direction inner side surfaces of the pair of side cross members 24, 26, and the outer surfaces of the pair of side cross members 24, 26 are provided with a base 30d of an arm support bracket 30 having a U-shaped cross section at a position near the joint portion (20a, 22a) of the cross member 20 (22) to the side cross members 24, 26. is welded to at least one of the opposing side portions 30a, 30b of the arm support bracket 30, which supports the pivot portion of the suspension arm (trailing arm 6) by sandwiching it from both sides, and a notch 20g that opens outward in the vehicle width direction is formed in a part of the open end 20a (22a) of the cross member 20 (22), and the notch 20g is welded to at least one of the opposing side portions 30a, 30b of the arm support bracket 30 at a position spaced downward or upward from the base 30d of the arm support bracket 30.

[0056] According to this embodiment and the modified example configured as described above, the arm support bracket 30 is welded to the cross member 20 (22) at a position spaced downward or upward, in addition to welding its base 30d to the side cross members 24, 26. This improves the strength against bending forces applied to the portion near the base 30d, and accordingly improves the bending rigidity of the bracket 30, so that the pivot position of the arm (trailing arm 6) does not move. Therefore, in the parallel-crested subframe 3, the strength of the arm support bracket 30 provided on the outer surfaces of the side cross members 24, 26 can be increased, and the support rigidity of the arm can be increased.

[0057] Furthermore, in this embodiment and its modified example, a bulge 20f that bulges downward or upward is formed in a portion of the open end 20a (22a) of the cross member 20 (22), and a cutout portion 20g is formed in this bulge 20f, thereby more effectively increasing the strength of the arm support bracket 30 provided on the outer surface of the side cross members 24, 26 and increasing the supporting rigidity of the arm.

[0058] Furthermore, in this embodiment and its modified example, the cutout portion 20g of the cross member 20 (22) is welded to surround at least one of the side portions 30a, 30b and the rear portion 30c of the arm support bracket 30, thereby more effectively increasing the strength of the arm support bracket 30 provided on the outer surface of the side cross members 24, 26 and increasing the supporting rigidity of the arm. [Explanation of symbols]

[0059] 1 Automotive suspension system / rear suspension assembly 2 Rear wheels 3 Subframe 4 Upper Arm 5 Leading Arm 6 Trailing Arm 7 Lower Arm 8 Toe control arm (control arm) 10. Wheel Support 16 Shock absorber 18 Stabilizer bar (stabilizer link) 20 Front cross member 20a Both ends / left and right open ends 20b Enlarged section 20c protrusion 20d extension 20e Front and rear curved parts 20f bulge 20g Notch 20h outer edge 21 Rear cross member body 22 Rear cross member 22a Both ends / left and right open ends 23 Lower part of rear cross member 24, 26 Side cross member (side member) 30 Trailing arm 6 support bracket (pivot support) 30a, 30b Side portion of arm support bracket 30c Rear part of arm support bracket 30d Base of arm support bracket 120, 220 Upper and lower plate-shaped members of the front cross member 20 123, 124, 223 Front and rear plate members of rear cross member IK Virtual Kingpin Axis S space W Welding line (welding line)

Claims

1. A subframe structure for an automobile is configured in a lattice shape by a pair of side members extending in a front-rear direction of the vehicle on both left and right sides in the vehicle width direction, and a front cross member and a rear cross member extending in the vehicle width direction so as to connect the pair of side members to each other, The cross members constituting the front cross member and / or the rear cross member are connected such that at least a portion of the left and right open ends thereof abut against inner side surfaces in the vehicle width direction of the pair of side members, a base portion of an arm support bracket having a U-shaped cross section is welded to an outer surface of the pair of side members at a position near a joint portion of the cross member to the side member and below the side member, the arm support bracket including opposing side portions which support the pivot portion of the suspension arm so as to sandwich it from both sides; A cutout portion that opens outward in the vehicle width direction is formed in a part of the open end of the cross member, the cutout portion is formed so as to surround at least one of the side portions and a rear portion of the arm support bracket, and is welded to at least one of the opposing side portions of the arm support bracket at a position spaced downward from a base of the arm support bracket.

2. 2. The subframe structure for an automobile according to claim 1, wherein a downwardly bulging portion is formed on a part of the open end of said cross member, and said cutout portion is formed in said bulging portion.

3. 3. The subframe structure for an automobile according to claim 1, wherein the cutout portion of the cross member is welded to and abuts against at least one of the side portions and a rear portion of the arm support bracket so as to surround the cutout portion.

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