Automotive subframe structure

Abstract

To provide a sub-frame structure of an automobile allowing an opening for accessing a pivot bolt of a control arm to be provided without allowing rigidity of a cross member to decrease.SOLUTION: In a sub-frame structure of an automobile according to the present invention, an attachment portion 36 for a control arm 8 is provided on a rear surface portion 23b of a plate-like member 223 on a rear side of each rear cross member lower portion 23. The attachment portion 36 is attached with a pivot bolt 39 pivotally supporting the control arm 8 so that a toe angle of a rear wheel 2 is adjustable. An opening 23f is formed in front of the attachment portion 36 of the control arm 8 in an upper edge portion of plate-like members 123, 124 on a front side of the rear cross member 23, and the pivot bolt 39 is provided in the opening 23f when viewed from the front.SELECTED DRAWING: Figure 11

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] A conventional multi-link suspension device is known that has five I-links, with the vehicle body end of each link connected to a subframe attached to the vehicle body and the wheel end of each link connected to a wheel support that supports the wheel. A known subframe for such a multi-link suspension is one that is configured in a lattice shape with a pair of side members and front and rear cross members (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2006-347338 Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of five-link suspension, it is effective for the lower arm and control arm to be longer than the other arms in terms of the function of each arm, and for this reason the connection positions of the lower arm and control arm to the subframe are set closer to the center in the vehicle width direction than both left and right ends of the rear cross member, and the mounting parts of each arm are provided at such positions.Here, since the lower arm receives a large input from the wheels, it is possible to provide an arm support part in the hollow member that constitutes the cross member so that it is supported by the cross member itself, and to provide a bracket as an arm support part on the rear surface of the cross member to support the control arm, which receives a relatively small input from the wheels.

[0005] Furthermore, the function of the control arm may be to adjust the toe angle by using the pivot bolt as a cam bolt. In this case, it is necessary to form a subframe so that the pivot bolt can be accessed to adjust the toe angle. However, forming an access hole in the hollow member that constitutes the cross member reduces the rigidity of the cross member.

[0006] Therefore, the present invention has been made to solve the above-mentioned problems, and aims to provide an automobile subframe structure that can provide an opening for access to the control arm support bolt without reducing the rigidity of the cross member. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention provides an automobile subframe structure configured in a criss-cross shape by a pair of side members extending in the fore-and-aft direction of the vehicle on both the left and right sides of 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 rear cross member has a rear cross member main body consisting of a first hollow body connecting front and rear plate-like members to each other, and a pair of second hollow bodies connecting front and rear plate-like members to each other, which are respectively connected to the lower parts of both the left and right ends of the rear cross member main body, The pair of second hollow bodies are formed with a support portion for the end of the lower arm on the vehicle body side,The rear surface of the rear plate-like member of the pair of second hollow bodies is provided with a control arm. The mounting bracket is attached. , these Mounting bracket for, One of the support portions of the vehicle body side end of the control arm is formed at a position spaced from the rear surface of the rear plate member of the pair of second hollow bodies, and the other support portion of the vehicle body side end of the control arm is formed on the rear surface of the rear plate member of the pair of second hollow bodies, so that the vehicle body side end of the control arm is supported by the one support portion and the other support portion, and one of the support portions of the mounting bracket is provided with A support bolt is attached to support the control arm so that the toe angle of the wheel can be adjusted. The upper edge of the front plate-like member of the pair of second hollow bodies is provided with a support bolt for supporting the control arm. One pivot point and the other pivot point In front view, openings are formed in the front position, and support bolts are provided in these openings. The support bolt extends forward from one support portion through the other support portion toward the opening. , which is its characteristic.

[0008] According to the present invention thus configured, the control arm mounting portion is provided on the rear plate member of the second hollow body. (The other pivot point and one of the pivot points of the mounting bracket) and an opening is formed in the front plate-like member of the second hollow body at a position coinciding with the front-rear direction of the arm attachment portion, and a pivot bolt is provided within the opening in front view, so that the pivot bolt of the control arm (a fastening member such as a cam bolt that adjusts the toe angle) can be accessed from the opening. In this way, an opening is not formed in the first hollow body (rear cross member main body), which is a main member of the lattice frame, but an opening is formed in the second hollow body. Therefore, an opening for access to the pivot bolt of the control arm can be provided without reducing the rigidity of the cross member.

[0009] In addition, in the present invention, preferably, the second hollow body extends from the joint with the lower part of the rear cross member main body, wrapping around from the lower side of the side member to the outer surface side and extending above the outer surface of the side member in a vehicle width direction outward, and the second hollow body has an inner portion in the vehicle width direction joined to the first hollow body and an outer portion in the vehicle width direction joined to the side member with respect to an opening formed in the upper edge part. According to the present invention configured in this manner, the second hollow body can contribute to improving the rigidity of the lattice-shaped frame. Effect of the Invention

[0010] The subframe structure for an automobile of the present invention allows an opening for accessing the pivot bolt of the control arm to be provided without reducing the rigidity of the cross member. [Brief description of the drawings]

[0011] [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] FIG. 4 is a partially enlarged rear view similar to FIG. 3, showing the structure of a rear cross member on the left side of the vehicle in the automobile subframe according to the present embodiment. [Figure 8] 8 is a perspective view of the rear cross member shown in FIG. 7, as viewed diagonally from the rear of the vehicle. [Figure 9] FIG. 2 is a left side view showing the subframe structure on the left side of the vehicle according to the present embodiment. [Figure 10] 10 is a perspective view of the subframe structure on the left side of the vehicle shown in FIG. 9, as viewed obliquely from the front of the vehicle. [Figure 11] FIG. 4 is a front view showing a joining structure of a rear cross member to a side cross member. [Figure 12] 4 is a left side partial cross-sectional view showing a lower arm mounting portion and a control arm mounting portion of the rear cross member according to the embodiment. FIG. [Figure 13] FIG. 2 is a perspective view showing a mounting bracket for a control arm according to the present embodiment. [Figure 14]14 is a perspective view of the mounting bracket for the control arm according to the present embodiment, seen from an angle different from that of FIG. 13. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a subframe structure for an automobile according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] Further, at both left and right ends of the front cross member 20, in positions close to the joints (open ends 20a) with the side cross members 24, 26 and above and below 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.

[0020] 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.

[0021] Moreover, 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 in the vehicle width direction of the side cross members 24, 26 and is joined (welded) to the lower and outer surfaces of the side cross members 24, 26 (see FIGS. 7 to 11).

[0022] 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 9 and 10).

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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).

[0030] 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.

[0031] The pivot support portion 32 of the leading arm 5 is composed of two opposing plate-shaped members, one of which is the upper end portion (plate-shaped member 124) of the above-mentioned rear cross member lower portion 23, and the other is a plate-shaped member whose base is welded to the side cross members 24, 26 (see Figures 4 and 5).

[0032] 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.

[0033] 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.

[0034] 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).

[0035] 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.

[0036] 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).

[0037] 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.

[0038] 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.

[0039] 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).

[0040] 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).

[0041] 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 in the portion rearward of the opening 84 (the portion rearward of the axle), and the toe control arm 8 is connected to this rear vertical wall portion 90.

[0042] Next, the joining structure of the rear cross member 22 to the side cross members 24, 26 will be described with reference to Figures 7 to 12. Figure 7 is a partially enlarged rear view similar to Figure 3, showing the structure of the rear cross member on the vehicle left side of the subframe for an automobile according to this embodiment, Figure 8 is a perspective view of the rear cross member shown in Figure 7, seen diagonally from the rear of the vehicle, Figure 9 is a left side view showing the subframe structure on the vehicle left side according to this embodiment, Figure 10 is a perspective view of the subframe structure on the vehicle left side shown in Figure 9, seen diagonally from the front of the vehicle, Figure 11 is a front view showing the joining structure of the rear cross member to the side cross members, and Figure 12 is a left side partial cross-sectional view showing the lower arm mounting portion and the control arm mounting portion of the rear cross member according to this embodiment. First, as shown in Figs. 7 and 11, rear cross member lower portions 23 are provided on the lower left and right sides of rear cross member main body 21. The rear cross member lower portion 23 is mainly composed of a first plate-shaped member (first front member) 123 on the front and lower side, as shown in Figures 10 and 11, a second plate-shaped member (second front member) 124 on the front and upper side, and a rear plate-shaped member (rear member) 223 on the rear side, as shown in Figures 7 to 9.

[0043] First, the configuration of the rear member 223 of the rear cross member lower portion 23 will be described with reference to FIGS. The rear member 223 is formed with an upper edge portion 23d that is joined to the lower edge portion of the rear surface 21a of the rear cross member body 21, and a stepped portion 23e (see FIG. 9 in particular) that is located on the vehicle front side of the rear surface 21a of the rear cross member body 21 relative to the upper edge portion 23d. The upper edge portion 23d of the rear member 223 is welded to the rear surface 21a of the rear cross member body 21 along a weld line indicated by the symbol W in the drawings. In addition, a pivot support portion 34 of the lower arm 7 is provided at the lower end portion of the rear member 223, i.e., below the stepped portion 23e, as shown in FIGS. 7 to 9.

[0044] 7 to 9, a pivot support portion 36 of the toe control arm 8 described above is provided on the rear surface of the rear member 223 (rear surface 23b of the rear cross-member lower portion 23). The pivot support portion 36 includes an arm support bracket 37 having a U-shaped cross section, and the arm support bracket 37 has an upper surface portion 37a, a lower surface portion 37b, and a rear surface portion 37c, and a base portion 37d is joined (welded) to the rear surface 23b of the rear member 223. In this embodiment, the upper surface portion 37a is formed so as to be positioned higher as it moves outward in the vehicle width direction, and the lower surface portion 37b is formed so as to extend in a substantially horizontal direction, so that the bracket 37 is formed in a triangular shape in rear view so that the vertical length increases toward the outer side in the vehicle width direction.

[0045] 7 and 8, the bracket 37 is welded to the rear surface 23b of the rear member 223 at weld lines W that run along the base 37d of the upper surface portion 37a and the base 37d of the lower surface portion 37b. In addition, the bracket 37 is welded to the rear member 223 by these weld lines W so as to straddle the upper edge portion 23d and the stepped portion 23e of the rear cross-member lower portion 23.

[0046] Next, one of the pivot portions (bracket side pivot portion) 37e is formed on the end portion on the vehicle width direction outer side of the rear surface portion 37c of the arm support bracket 37. On the other hand, as shown in particular in Fig. 9, at a position facing the front side of this pivot portion 37e, the other of the pivot portions (cross member side pivot portion) 23c (see Figs. 9 and 12) is formed in the above-mentioned stepped portion 23e of the rear member 223, and the pivot portion including the vehicle body side pivot bolt 39 of the control arm 8 is pivotally supported by these two facing pivot portions 37e, 23c. 12, in this embodiment, the journal bolt 39 of the toe control arm 8 is a cam bolt, giving the toe control arm 8 the ability to adjust the toe angle of the rear wheel 2. For this reason, a hole for inserting the cam bolt 39 is formed in the journal portion 37e of the arm support bracket 37, and an eccentricity index plate 41 (see FIG. 8) with a scale indicating the degree of eccentricity (degree of toe angle adjustment) is attached.

[0047] Next, openings 37f that open outward in the vehicle width direction are formed above and below the pivot portion 37e on the upper surface 37a and lower surface 37b of the arm support bracket 37, and a rib 37g is formed near the pivot portion 37e of the bracket 37.

[0048] Next, the configuration of the front members 123, 124 of the rear cross member lower portion 23 will be described with reference to FIGS. First, as shown in FIGS. 9 to 11, the rear cross member lower portion 23 has a first front member 123 on the front and lower side, and a second front member 124 on the front and upper side. The first front member 123 is formed so as to extend from a joint 23a with the lower part of the rear cross member main body 21 outward in the vehicle width direction and wrap around from the lower side of the side cross member 24 (26) to the outer surface side.

[0049] An opening 23f is formed in the upper edge of the first front member 123 so that an operator can access the cam bolt 39 for adjusting the toe angle. That is, in this embodiment, as shown in Fig. 11, the cam bolt 39 is provided in the opening 23f when viewed from the front of the vehicle.

[0050] Next, the upper edge of the first front member 123, which is outward in the vehicle width direction from the opening 23f, is welded from the underside to the side of the side cross member 24 (26) (see welding line W). Furthermore, the upper edge of the first front member 123, which is inward in the vehicle width direction, is welded to the lower part of the rear cross member main body 21 (see welding line W), and the outer edge in the vehicle width direction is welded to the outer edge in the vehicle width direction of the above-mentioned rear member 223 (see welding line W).

[0051] Next, the second front member 124 provided above is configured as an extension of the first front member 123 up to above the outer surface of the side cross member 24 (26), and also configures one of the opposing plate-shaped members that support the pivot shaft in the mounting seat 32 of the leading arm 5 described above.

[0052] The second front member 124 has an outer edge in the vehicle width direction welded to an outer edge in the vehicle width direction of the above-mentioned rear member 223 (see welding line W). Furthermore, the second front member 124 is welded to the side and upper surface of the side cross member 24 (26) (see welding line W) so as to ensure the arm support rigidity of the above-mentioned mounting seat 32. Furthermore, the lower edge of the second front member 124 is welded to an outer edge in the vehicle width direction of the first front member 123 (see welding line W).

[0053] Next, the rear cross member lower portion 23, which is composed of the front members 123, 124 and the rear member 223 configured as described above, is formed so that its front-to-rear length is smaller than the front-to-rear length of the expanded portion 22b of the rear cross member main body 21 (the connection portion to the side cross member 24 (26) at both left and right ends), as shown particularly in Figures 8 and 10.

[0054] Next, as shown in Figures 13 and 14, arm support bracket 37 is formed by pressing a plate-shaped steel plate member, and has the above-mentioned upper surface portion 37a, lower surface portion 37b, rear surface portion 37c, base portion 37d and pivot portion 37e, and bracket 37 is also formed with opening 37f and rib 37g.

[0055] Next, the effects of this embodiment will be described. According to this embodiment, the rear cross member 22 has a rear cross member main body 21 consisting of a first hollow body formed by connecting front and rear plate-like members 121, 221 to each other, and a pair of rear cross member lower parts (second hollow bodies) 23 formed by connecting front and rear plate-like members 123, 124), 223 to each other, which are respectively connected to the lower part of both left and right ends of the rear cross member main body 21. A mounting portion 36 for a control arm 8 is provided on each rear surface portion 23b of the rear plate-like member 223 of the pair of rear cross member lower parts 23, and a support bolt 39 for supporting the control arm 8 so that the toe angle of the rear wheel 2 can be adjusted is attached to each of these mounting portions 36. An opening 23f is formed in the upper edge portion of the front plate-like members 123, 124 of the pair of rear cross member lower parts 23, respectively, at a position forward of the mounting portion 36 of the control arm 8, and a support bolt 3 is provided within these openings 23f when viewed from the front. According to the present embodiment configured as described above, the mounting portion 36 of the control arm 8 is provided on the rear plate-like member 233 of the rear cross-member lower portion (second hollow body) 23, and the front plate-like members 123, 124 of the rear cross-member lower portion 23 have openings 23f formed at positions that coincide with the arm mounting portion 36 in the front-rear direction, and the pivot bolt 39 is provided in the openings 23f in a front view, so that the pivot bolt 39 of the control arm 8 (a fastening member such as a cam bolt for adjusting the toe angle) can be accessed from the openings 23f. In this way, the openings 23f are not formed in the rear cross-member main body (first hollow body) 21, which is a main member of the lattice frame, but are formed in the rear cross-member lower portion (second hollow body) 23. Therefore, an opening for accessing the pivot bolt of the control arm can be provided without reducing the rigidity of the cross member.

[0056] In addition, in this embodiment, the second hollow body 23 extends from the connection portion 23a with the lower part of the rear cross member main body 21 outward in the vehicle width direction, around from the lower side of the side cross members 24, 26 to the outer side surface side and above the outer surface of the side cross members 24, 26, and the rear cross member lower part 23 has its vehicle width inner portion connected to the first hollow body 21 and its vehicle width outer portion connected to the side cross members 24, 26 with respect to the opening 23f formed in its upper edge, so that the second hollow body 23 can contribute to improving the rigidity of the lattice-shaped frame. [Explanation of symbols]

[0057] 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 21 Rear cross member body (first hollow body) 21a Rear 22 Rear cross member 22a Both ends / left and right open ends 22b Enlarged section 23 Lower part of rear cross member (second hollow body) 23a Joint part 23b Rear 23c Cross member side support 23d Upper edge part 23e Step area 23f: Front opening of rear cross member lower portion 23 24, 26 Side cross member (side member) 32 Pivot support part (pivot support part) of leading arm 5 34 Pivot shaft support portion (pivot support portion) of lower arm 7 37 Toe control arm 8 support bracket 37a, 37b, 37c Top, bottom, rear 37d base 37e Bracket side support 37f opening 37g Rib 39 Support bolt / cam bolt 41 Eccentric index plate 123 Front lower plate member of rear cross member (first front member) 124 Front upper plate member of rear cross member (second front member) 223 Rear plate-shaped member of rear cross member (rear member) IK Virtual Kingpin Axis 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 a 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 rear cross member has a rear cross member body composed of a first hollow body formed by joining front and rear plate-like members together, and a pair of second hollow bodies formed by joining front and rear plate-like members together, which are respectively joined to the lower parts of both left and right ends of the rear cross member body, and a support portion for the vehicle body side end of the lower arm is formed in the pair of second hollow bodies, A mounting bracket for a control arm is attached to each of the rear surface portions of the rear plate-like member of the pair of second hollow bodies, and one of the support portions for the vehicle body side end of the control arm is formed on each of the mounting brackets at a position spaced from the rear surface portion of the rear plate-like member of the pair of second hollow bodies, and the other of the support portions for the vehicle body side end of the control arm is formed on the rear surface portion of the rear plate-like member of the pair of second hollow bodies, such that the vehicle body side end of the control arm is supported by the one support portion and the other support portion, and a support bolt for supporting the control arm so as to adjust the toe angle of the wheel is attached to the one support portion of the mounting bracket, A subframe structure for an automobile, characterized in that an opening is formed in the upper edge portion of the front plate-shaped member of the pair of second hollow bodies, respectively, at a position forward of the one support portion and the other support portion of the control arm, and the support bolt extends forward from the one support portion via the other support portion toward the opening so that the support bolt is provided within these openings when viewed from the front.

2. the second hollow body extends from a joint portion with the lower portion of the rear cross member body outward in the vehicle width direction, around from the lower side of the side member to the outer surface side, and up to an upper portion of the outer surface of the side member, 2. The subframe structure for an automobile as described in claim 1, wherein the second hollow body has an inner portion in the vehicle width direction connected to the first hollow body and an outer portion in the vehicle width direction connected to the side member with respect to an opening formed in the upper edge portion.

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