Subframe for a motor vehicle

Abstract

Auxiliary frame (10) for a motor vehicle, comprising: two longitudinal beams (11, 12), a front cross member (13) and a rear cross member (14), each connecting the two longitudinal members (11, 12) in the transverse direction of the vehicle, wherein the cross-sectional profile of the front cross member (13) is asymmetrical with respect to a vertical longitudinal center plane of the vehicle, characterized by the fact that the front cross member (13) has a symmetrical lateral stiffness in the transverse direction of the vehicle.

Description

[0001] The invention relates to an auxiliary frame for a motor vehicle with the features of the preamble of claim 1.

[0002] A subframe for a motor vehicle, comprising two longitudinal members, as well as a front crossmember and a rear crossmember, each connecting the two longitudinal members in the transverse direction of the vehicle, is known, for example, from DE 10 2006 058 993 A1. Another subframe is known from DE 199 09 945 C1. In these, the basic construction of longitudinal and transverse members is symmetrical with respect to a longitudinal center axis of the vehicle.

[0003] A generic auxiliary frame according to the preamble of claim 1 is known from DE 101 09 636 A1. This frame has a projection on the front cross member for supporting a differential gear, resulting in a certain asymmetry of the front cross member.

[0004] Another generic subframe according to the preamble of claim 1 is known from DE 10 2010 049 344 A1. This subframe has a bulge on one of the cross members for a force application point, which in turn results in an asymmetry of the cross member. Depending on whether the subframe is to be used in series production for a more or less powerful vehicle, the bulge can optionally be filled with polyurethane foam to provide an additional stiffening effect at the relevant point.

[0005] The invention is based on the objective of demonstrating alternatives to this. In particular, a solution is to be created that, taking into account stiffness and strength requirements, requires little installation space and has a low component weight.

[0006] This problem is solved by an auxiliary frame according to claim 1 and further by a rear axle arrangement comprising such an auxiliary frame according to claim 10. The auxiliary frame is characterized in particular by the fact that, in the case of an asymmetric cross-sectional profile of the front cross member with respect to a vertical longitudinal center plane of the vehicle, the front cross member has a symmetrical lateral stiffness in the transverse direction of the vehicle.

[0007] This allows for space-optimized placement of the subframe on the vehicle while ensuring harmonious driving behavior, especially when considering a gearbox located in the area of ​​the rear axle, as is the case, for example, with all-wheel drive vehicles.

[0008] Advantageous embodiments of the invention are specified in further patent claims.

[0009] The invention will now be explained in more detail with reference to an embodiment illustrated in the drawing. The drawing shows: Fig. 1 a spatial view of an embodiment of an auxiliary frame according to the invention from the front top, Fig. 2 a front view of the subframe according to Fig. 1, Fig. 3 an exploded view of the subframe according to Fig. 1, Fig. 4 a detailed view of the front upper handlebar mount O1, Fig. 5 a detailed view of the front lower handlebar mount S1, Fig. 6 a detailed view of the rear crossmember, and in Fig. 7 a top view of the auxiliary frame according to Fig. 1 and a rear axle gearbox supported on it.

[0010] The in the Fig. 1 to Fig. The illustrated embodiment 7 shows a subframe 10 for a passenger car.

[0011] The subframe 10 has two longitudinal members 11 and 12 extending essentially in the longitudinal direction x of the vehicle, as well as a front cross member 13 and a rear cross member 14 with respect to the forward direction V. The two cross members 13 and 14 are spaced apart from each other in the longitudinal direction x of the vehicle and connect the two longitudinal members 11 and 12 in the transverse direction y of the vehicle, thus forming a roughly rectangular frame.

[0012] The longitudinal beams 11 and 12 are each connected to the front crossbeam 13 at an end point V facing forward. The front crossbeam 13 projects laterally beyond the end points of the longitudinal beams 11 and 12 and has a front connection point 17 at each of its end sections 15 and 16 for connection to a vehicle body. The end sections 15 and 16 transition via cranked transition sections 18 and 19 into a central section 20, which is offset upwards with respect to the vehicle's height z compared to the end sections 15 and 16.

[0013] The longitudinal beams 11 and 12 project beyond the rear crossbeam 14 with their rear end sections 21 and 22. The latter has a U-shaped, downwardly open cross-sectional profile and is connected at its ends to the inner flanks of the longitudinal beams 11 and 12. Further rear attachment points 23 for securing the subframe 10 to the vehicle body are located at the rear end sections 21 and 22 of the longitudinal beams 11 and 12.

[0014] The subframe 10 also has several control arm mounts O1, S1, U3 on each side of the vehicle for attaching wheel guide arms. The control arm mounts O1, S1, U3 are each present in duplicate and arranged symmetrically with respect to a vertical longitudinal center plane E, which contains the longitudinal center axis X of the vehicle. Therefore, only the control arm mounts on the left side of the vehicle will be discussed below.

[0015] A first upper control arm mounting O1 is located on the outside of the longitudinal member 12, shortly behind its front end. This control arm mounting O1 is shown here by way of example by a bracket 24 welded to the longitudinal control arm 12. The bracket 24 is formed by two bracket halves 24a and 24b with eccentric projections 25 and has two openings 26 for the passage of a bearing bolt. The associated pivot axis runs essentially horizontally in the longitudinal direction of the vehicle. However, a one-piece bracket 24 can also be provided.

[0016] Below the upper handlebar mount O1 is a second lower handlebar mount S1. This lower handlebar mount S1 is also exemplified by a bracket 27 with two openings 28 for the passage of a bearing bolt. The bracket 27 can be formed by two bracket halves 27a and 27b. Preferably, the softer rear bracket half 27b has a greater wall thickness than the front bracket half 27a. Furthermore, a one-piece design of the bracket 27 is also possible.

[0017] The console 27 of the front lower control arm mount S1 extends downwards from the associated longitudinal member 12 in the vehicle's vertical direction z. The pivot axis may be offset relative to the longitudinal member 12 towards the nearest outer side of the vehicle. The console 27 is located in the region of the front end of the longitudinal member 12. Preferably, it is also supported, at least partially, by the front cross member 13. However, it is also possible to arrange the console 27 next to, and preferably directly next to, the front cross member 13. The lateral stiffness of the subframe 10 in the vehicle's transverse direction y is the same at the consoles 27 of the front lower control arm mounts S1 that are opposite each other with respect to the vehicle's longitudinal center plane E.

[0018] A further rear control arm mounting point U3 for another wheel guide link is located approximately at the level of the lower control arm mounting point S1 on the rear crossmember 14. This rear control arm mounting point U3 is formed by opposing flanks of the crossmember profile and has corresponding openings 29 for the passage of a bearing bolt. The rear control arm mounting points U3 are offset towards the center of the vehicle compared to the front lower control arm mounting points S1. The pivot axes of the rear control arm mounting points U3 are predominantly horizontal and predominantly in the forward direction of travel, and can also be angled towards each other in a forward-facing direction. In a variation of the embodiment, separate brackets for the rear control arm mounting points U3 can also be attached to the second crossmember 14.

[0019] Between the rear handlebar mounts U3 is a passage 30 for an exhaust system. The cross member 14 can be provided in its center with a corresponding recess 31 or a bend upwards, or possibly downwards.

[0020] To optimize the strength and stiffness properties and to maintain a compact design in the area of ​​the rear axle with low component weight, the auxiliary frame 10 according to the invention has the modifications explained in more detail below, particularly in the area of ​​the front cross member 13.

[0021] The front crossmember 13 has a cross-sectional profile in the transverse direction of the vehicle that is asymmetrical with respect to the vertical longitudinal center plane E of the vehicle. At the same time, the front crossmember 13 exhibits a symmetrical transverse stiffness in the transverse direction y of the vehicle. The transverse stiffness Q L or Q RThe magnitude of the front crossbeam 13 is equal at its opposite ends, but has opposite signs.

[0022] The asymmetrical cross-sectional profile is particularly noticeable in Fig. 2. This can be clearly seen from the differently designed transition sections 18 and 19 of the exemplary embodiment, whose profile height, i.e., extension in the vehicle's vertical direction z, differs with respect to the vehicle's transverse direction y. The central section 20 and the end sections 15 and 16, on the other hand, can be designed symmetrically to the vehicle's longitudinal median plane E.

[0023] However, the asymmetry can also be achieved in other ways and need not be limited to the transition sections 18 and 19. Rather, it can also be created on other sections of the crossbeam 13 or over its entire length.

[0024] In particular, a symmetrical design of the transition sections 18 and 19 is also possible, while other sections of the front cross member 13 are simultaneously designed asymmetrically. This also applies in particular to cases where the front cross member 13 is manufactured without a distinct bend, i.e., without pronounced transition sections 18 and 19.

[0025] The asymmetrical cross-sectional profile is preferably obtained by a different profile height in the transverse direction of the vehicle, as shown in the exemplary embodiment.

[0026] For example, the front crossmember 13 can have at least one area where the profile height, when viewed from the center of the vehicle outwards, increases later but then more sharply on one side (in Fig. 2 in transition section 18 on the left, i.e. on the right side of the vehicle), than on the opposite side.

[0027] This allows the use of a particularly narrow front crossmember 13 in the longitudinal direction x of the vehicle. For example, the profile height can always be greater than the profile width. In particular, the front crossmember can also be designed with a constant profile width.

[0028] However, an asymmetry of the cross-sectional profile can also be created solely via the profile width, i.e. the extent in the longitudinal direction of the vehicle x, or by a combination of different profile height and profile width.

[0029] In all cases, however, the cross-sectional profile is always chosen such that the front cross member 13 has a symmetrical transverse stiffness in the transverse direction y of the vehicle, i.e. the transverse stiffness on the left side of the vehicle is the same as on the right side of the vehicle.

[0030] The auxiliary frame 10 described above is preferably constructed of sheet metal. Its individual components, which are in Fig. The components shown in section 3 can be manufactured easily and cost-effectively, for example by sheet metal forming. They are preferably joined together by welding.

[0031] Preferably, the front crossbeam 13 is longitudinally divided and has two half-shells 13a and 13b, which together form a box-shaped cross-sectional profile. The division is preferably vertical.

[0032] However, it is also possible to realize an asymmetric cross-sectional profile on a tube formed, for example, by internal high-pressure forming, which serves as a front cross member 13.

[0033] However, the shell design allows for a more flexible shaping of the desired asymmetry of the cross-sectional profile.

[0034] When using half-shells in conjunction with a box-shaped cross-sectional profile, it is advantageous to weld the half-shells 13a and 13b together at the top and bottom of the crossbeam 13.

[0035] The rear crossmember 14 can also be designed as a two-shell profile with two half-shells 14a and 14b. In contrast to the front crossmember 13, the cross-sectional profile of the rear crossmember 14 is open at the bottom, so that two wheel guide arms can engage from below into the open profile between the two half-shells 14a and 14b in the area of ​​the rear control arm mounts U3.

[0036] Furthermore, as in Fig. Figure 6 shows that a sheet 36 is integrated into the rear cross member 14, serving to attach a heat shield. The sheet 36 can be formed as a tab on one or both of the half-shells 14a and 14b. However, it is also possible to attach the sheet 36 separately to the rear cross member 14. It can also be used to stiffen the cross-section of the rear cross member 14.

[0037] The longitudinal beams 11 and 12 are preferably designed as formed tubular elements, each of which is attached to the front crossbeam 13 with a front end end.

[0038] The subframe 10 described above can, for example, be used to support a rear axle drive 32, but is not limited to such use. It can also be used in purely front-wheel-drive vehicles.

[0039] In the case of supporting a rear axle transmission 32, the subframe 10 has suitable support points for the transmission 32. For this purpose, a bracket 33 can be provided, in particular, on the front crossmember 13. In the illustrated embodiment, this bracket is arranged off-center on the front crossmember 13. It is located at the front of the crossmember 13, but can also be attached to its rear if required.

[0040] Preferably, the transmission support is designed as a three-point mounting with three support points on the subframe 10, so that the in Fig. The rear axle arrangement shown in Figure 7 results. As already explained, in every case a first support point P1 is located outside the vehicle center on the front crossmember 13, which runs above the transmission 32. The two further support points P2 and P3 are located on the rear crossmember 14 and / or the longitudinal members 11 and 12.

[0041] The exemplary embodiment shows the arrangement of two rear support points P2 and P3 on the rear cross member 14, which for this purpose forms corresponding plate-shaped support surfaces 34 in its apex region for supporting mounting brackets of the gearbox 32, as well as associated through-openings. Since the rear cross member 14 is vertically divided, increased stiffness can be easily achieved by forming corresponding tabs 34a and 34b on its half-shells 14a and 14b at the support points P2 and P3.

[0042] The invention has been explained in more detail above with reference to an exemplary embodiment. However, it is not limited to this embodiment. It is expressly pointed out that subcombinations of the described features, even those not explicitly explained, are possible as long as they are technically feasible. The invention includes, in particular, all embodiments defined by the claims. Reference symbol list 10 subframes 11 longitudinal beams, right 12 longitudinal beams, left 13 front crossmember 14 rear crossmember 15 Final section 16 Final section 17 Connection point 18 Transition section 19 Transition section 20 Middle section 21 Longitudinal beam end section 22 Longitudinal beam end section 23 Connection point 24 console 24a front console half 24b rear console half 25 Eccentric Exhibition 26 Opening 27 console 27a front console half 27b rear console half 28 Opening 29 Opening 30 rounds 31 Exclusion 32 Rear axle gearbox 33 console 34 plates 34a tab 34b tab 36 sheets x Vehicle longitudinal direction y vehicle transverse direction z Vehicle lifting direction E vertical vehicle longitudinal center plane O1 Handlebar mount, upper and front Q L Lateral stiffness, left Q R Transverse stiffness, right S1 handlebar mount, lower and front U3 handlebar mount rear and bottom V Forward direction X Vehicle longitudinal center axis

Claims

[1] Auxiliary frame (10) for a motor vehicle, comprising: two longitudinal beams (11, 12), a front cross member (13) and a rear cross member (14), each connecting the two longitudinal members (11, 12) in the transverse direction of the vehicle, wherein the cross-sectional profile of the front cross member (13) is asymmetrical with respect to a vertical longitudinal center plane of the vehicle, characterized by , that the front cross member (13) has a symmetrical lateral stiffness in the transverse direction of the vehicle. [2] Auxiliary frame (10) according to claim 1, characterized by , that the front cross member (13) is formed by two half-shells (13a, 13b). [3] Auxiliary frame (10) according to claim 2, characterized by , that the front crossbeam (13) is vertically divided into the two half-shells (13a, 13b) and has a box-shaped cross-sectional profile. [4] Auxiliary frame (10) according to claim 2 or 3, characterized by, that the front cross member (13) has a top and a bottom and the half shells (13a, 13b) are welded together at the top and the bottom. [5] Auxiliary frame (10) according to any one of claims 1 to 4, characterized by , that a console (27) for attaching a wheel guide arm is provided on each of the longitudinal members (11, 12), which extends downwards from the respective longitudinal member (11, 12) with respect to the vehicle's vertical direction and is partially supported on the front cross member (13) or is arranged directly next to it, wherein the transverse stiffness of the subframe (10) in the vehicle's transverse direction is the same at the consoles (27) opposite each other with respect to the vehicle's longitudinal median plane. [6] Auxiliary frame (10) according to any one of claims 1 to 5, characterized by, that the front crossbeam (13) has a symmetrical central section (20), to which two transition sections (18, 19) with asymmetrical cross-sectional profiles are attached on both sides, which at their ends each transition into symmetrical end sections (15, 16). [7] Auxiliary frame (10) according to claim 6, characterized by , that the asymmetrical cross-sectional profile is maintained by a different profile height in the transverse direction of the vehicle. [8] Auxiliary frame (10) according to claim 7, characterized by , that the front cross member (13) has at least one area where, when viewed from the center of the vehicle outwards, the profile height rises later, but then more sharply, on one side than on the opposite side. [9] Auxiliary frame (10) according to any one of claims 1 to 8, characterized by , that the rear cross member (14) is designed as a downwardly open, double-shell profile with two profile halves (14a, 14b) and has two connection points (U3) for two wheel guide arms, which engage from below into the open profile between the two profile halves (14a, 14b), and / or the longitudinal beams (11, 12) are designed as formed tubular elements, each of which is connected to the front crossbeam (13) at a front end, and / or A console (33) for supporting a gearbox is provided on the front cross member (13), which is located outside the center of the vehicle. [10] Rear axle arrangement comprising a subframe (10) according to one of the preceding claims and a transmission (32), characterized by, that the gearbox (32) is supported in a three-point mounting with three support points (P1, P2, P3) on the subframe (10), such that a first support point (P1) is provided outside the center of the vehicle on the front cross member (13) and the two further support points (P2, P3) are located on the rear cross member (14) and / or the longitudinal members (11, 12).

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