Subframe for a rear axle of a motor vehicle

[0001] This application claims the priority, under 35 U.S.C. §119, of German application DE 10 2008 010 551.1, filed Feb. 22, 2008; the prior application is herewith incorporated by reference in its entirety.

[0002] The invention relates to a subframe for a rear axle of a motor vehicle. The subframe has two cross members, which are spaced apart from each other, between two longitudinal members, and the end sides of the longitudinal members each have connecting bearings toward the vehicle body. A differential is held on the cross members, and the longitudinal members have link bearings for wheel guiding elements.

[0003] German patent DE 199 09 945 C1, corresponding to U.S. Pat. No. 6,511,090, discloses a subframe for a rear axle of a motor vehicle. The subframe contains a framework which is fastened to the vehicle body and has cross members and longitudinal members connected to the latter. A transmission unit is mounted between the longitudinal members and cross members, and mountings for wheel guiding elements are provided on the longitudinal members. Furthermore, Japanese patent JP 64-40773 discloses a subframe which has longitudinal members and cross members, and connecting bearings toward the vehicle body are arranged at the free ends of the longitudinal members.

[0004] It is accordingly an object of the invention to provide a subframe for a rear axle of a motor vehicle that overcomes the above-mentioned disadvantages of the prior art devices of this general type, which subframe is configured such that it is light in terms of weight and is nevertheless stable in terms of strength, and can be fitted into the vehicle in a simple manner in the form of a preassembled unit together with wheel suspensions and with a differential.

[0005] With the foregoing and other objects in view there is provided, in accordance with the invention, a subframe for a rear axle of a motor vehicle. The subframe contains a framework cast as a single part and has corners. The framework contains profiled hollow members including: two longitudinal members containing link bearings for wheel guiding elements and end sides each having connecting bearings toward a vehicle body; and two cross members being spaced apart from each other, between the two longitudinal members, the cross members provided for supporting a differential. Connecting bearings and supporting pillars are disposed at the corners of the framework. Each of the longitudinal members has a curved passage opening between the supporting pillars. On the supporting pillars, the end sides of the longitudinal members and the cross members are integrally formed. The supporting pillar contains arms integrally formed thereon in a protruding manner for the connecting bearings. The cross members include a front cross member disposed between the supporting pillars and have—with respect to a direction of travel—a curved rounded portion with a bearing receptacle for the differential, and a rear cross member disposed between the supporting pillars and have a rectilinear extent.

[0006] The advantages primarily obtained with the invention are that the framework which is produced in a single-part configuration, for example by casting, obviates the need for any welds and other types of connection associated with the disadvantages of distortion and finishing work. In addition, all of the bearing receptacles are advantageously integrally formed at the same time, and therefore the bearing receptacles only have to be subjected to machining for dimensional accuracy. In particular, each longitudinal member of the subframe has a curved passage opening between supporting pillars at the corners of the framework, on which supporting pillars the end sides of the longitudinal members and cross members are integrally formed, and the supporting pillars have outwardly protruding arms with the connecting bearings. The front cross member between the supporting pillars has a curved rounded portion with a bearing receptacle for a differential, and the rear cross member between the supporting pillars has a rectilinear extent. The supporting pillars provide stable connecting points toward the vehicle body, in which connecting points the longitudinal members and cross members are connected optimally in terms of strength.

[0007] The connecting bearings are arranged at the respective free ends of the arms on the supporting pillars of the framework, with the two front connecting bearings being arranged in a lower horizontal plane than the two other, rear connecting bearings which lie in a higher horizontal plane. This permits adaptation of the connecting bearings to the circumstances of the vehicle body.

[0008] A reinforcing junction element for the bearing receptacle for a front region of the differential is arranged in the curved rounded portion of the front cross member, and a further bearing receptacle for a mounting on both sides of the rear region of the differential is arranged in each case between the rear cross member and the supporting pillars. The bearing receptacle is embedded between side walls within the front cross member, wherein the junction element of the bearing receptacle has outer, profile-forming impressions molded into the cross member on both sides of the bearing receptacle. This results in a stable mounting of the differential, in which the bearing is supported by side walls of the cross member.

[0009] The rear cross member is integrally formed in a lower region of the supporting pillars of the framework, and the protruding arms for the connecting bearings are connected to the supporting bearings as an extension of the cross member. An optimum strength bond between the supporting pillars and the cross member is therefore produced, with the cross member having a rectangular cross section which is oriented with the edge uppermost between the supporting pillars.

[0010] Other features which are considered as characteristic for the invention are set forth in the appended claims.

[0011] Although the invention is illustrated and described herein as embodied in a subframe for a rear axle of a motor vehicle, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

[0012] The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

[0019] Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a subframe 1 that has a framework with two lateral longitudinal members 2, 3 and two cross members 4, 5 which are arranged at a distance from each other and are connected to the longitudinal members 2, 3 via supporting pillars 6, 7, 8 and 9 at the corners, or are integrally formed with the supporting pillars. Protruding arms 10, 11, 12 and 13 have end sides with connecting bearings 10a, 11a, 12a and 13a disposed toward the vehicle body and are connected to the supporting pillars 6-9 (FIG. 2).

[0020] The longitudinal members 2, 3 have a curved passage opening 15 for a shaft 28 of a differential 17 between the respective supporting pillars 6, 9 and 7, 8 (FIGS. 2 and 3). In a curved rounded portion 19, the front cross member 5 has—with respect to a direction of travel F—a bearing receptacle 18 for a front region of the differential 17. A further, rear mounting of the differential 17 is provided in mountings 20, 21 between the rear cross member 4 and the supporting pillars 7 and 6.

[0021] The bearing receptacle 18 is provided within the cross member 5 and is embedded between side walls S1 and S2. Profile-forming impressions 22 are molded onto the rear side of the bearing receptacle 18.

[0022] Two front connecting bearings 12, 13 are arranged in a horizontal plane x-x which is positioned lower than the rear connection bearings 10a, 11a, which are arranged in the horizontal plane y-y, in arms 10, 11 of the supporting pillars 6 and 7 (see FIGS. 4-6).

[0023] The rear cross member 4 is integrally formed in a lower region of the supporting pillars 6, 7 of the framework, and the arms 10, 11, which protrude to both sides and have the connecting bearings 10a, 11a, are provided as an extension of the cross member 4. The cross member 4 is of a rectangular configuration in cross section and is oriented with the edge uppermost between the supporting pillars 6 and 7.

[0024] The supporting pillars 6, 7 between the rear cross member 4 and the adjoining longitudinal members 2, 3 have a respective bearing receptacle 25 for a wheel guiding link at the lower, free end (FIG. 3). At the upper end remote therefrom, a bearing receptacle 26 for a transverse link and a fastening plate 27 for a stabilizer are provided on the protruding arm 10, 11.

[0025] Between the supporting pillars 6, 9 and 7, 8, a stiffening bolt 29 can be arranged below the curved passage opening 15.

[0026] The subframe has a connection 30 for an upper transverse link and a connection 31 for a track rod.