Patent Description:
Suspensions of the so-called twist axle type are old and well known; they comprise a pair of longitudinal arms of the above indicated type and a cross-member which connects respective portions of the two longitudinal arms with each other, which portions are located at intermediate positions between the front ends and the rear ends of the longitudinal arms.

Rigid axle suspensions with longitudinal arms are also well known, in which the wheel supports are rigidly connected to the ends of a rigid axle. A suspension of this type is known from <CIT>.

In the modern production of motor-vehicles, such as in particular in the production of light-duty vehicles, the need is felt of a suspension system having a modular structure which enables the suspension to be configured as a twist axle suspension or as a rigid axle suspension, as a function of design needs. For example, there may be a need to design the same vehicle model both in a version for traction with an internal combustion engine, and in a version for electric traction, in which the necessity of providing sufficient space for housing the supply electric batteries may involve a change in the configuration of the suspension.

It is therefore an object of the invention that of providing a motor-vehicle rear suspension system having a modular structure adapted to be configured as a twist axle suspension or as a rigid axle suspension.

A further object of the invention is that of providing a motor-vehicle suspension system which is able to achieve the above indicated purpose with an extremely simple and inexpensive structure.

In view of achieving one or more of the above indicated objects, the invention provides a motor-vehicle rear suspension system having the features which have been indicated at the beginning of the present description and further characterized in that said main tubular element and said longitudinal arms are configured in such a way that the tubular element can be rigidly connected to the longitudinal arms in any of two selectable mounting positions:.

In one exemplary embodiment, said main body of each longitudinal arm has its rear portion extending substantially in a horizontal plane, with reference to the condition of use, and configured to act as a support for a helical spring of the suspension system. Furthermore, said main body of each longitudinal arm has a front portion extending substantially in a vertical plane, with reference to the condition of use, and welded to the body of an elastic bushing for the articulated connection to the supporting structure of the motor-vehicle.

Also in the case of an exemplary embodiment, the above mentioned auxiliary tubular elements are provided with brackets for connection to the rear ends of two shock-absorber units. Furthermore, the suspension system according to the invention comprises a stabilizing bar which is used only in the rigid axle suspension configuration, having one end provided with an attachment for articulation to a motor-vehicle supporting structure and an opposite end provided with an attachment for articulation to one of said auxiliary tubular elements.

Further features and advantages of the invention will become apparent from the description which follows with reference to the annexed drawings, given purely by way of non-limiting example, in which:.

Referring to the drawings, the suspension system according to the invention includes a pair of longitudinal arms <NUM> having front ends, each connected to the body of an elastic bushing <NUM>, for the articulated connection to a supporting structure <NUM> of the vehicle (see <FIG>, <FIG>) around an axis <NUM> which is substantially horizontal and transversal relative to the longitudinal direction of the vehicle (in <FIG>, <FIG>, the direction of advancement of the vehicle is indicated by arrow A).

With reference to <FIG>, <FIG>, the embodiment of the suspension system which is shown herein is applied to a light-duty vehicle in which the supporting structure <NUM> is constituted by the vehicle frame, including a pair of longitudinal beams <NUM> (only one of which is visible in the drawings) connected to each other by cross-member elements (not visible in the drawings), according to a technique which is conventional and known per se. However, it is clearly understood that the present invention is of general application and that in particular it can be applied on any type of vehicle, with any type of configuration of the vehicle supporting structure. In particular, the invention could be applied also to the case of a motor car, in which the supporting structure for the suspension may for example be constituted by a supporting auxiliary frame which on its turn is rigidly connected to the car body.

In the case of the example shown in <FIG>, <FIG>, each longitudinal beam <NUM> is provided with a bracket <NUM> for the articulated support around axis <NUM> of the respective longitudinal arm <NUM>.

With reference in particular to <FIG> and <FIG>, in the rigid axle suspension configuration, each longitudinal arm <NUM> may for example have the configuration which is clearly visible in <FIG>. In this case, each longitudinal arm <NUM> is constituted only by a main body 10A, formed by a single element of pressed sheet-metal. The element 10A has a rear portion extending substantially in a horizontal plane, with reference to the condition of use, and surrounded by a cylindrical wall 11A, projecting upwardly, for defining a supporting seat for the lower end of a helical spring <NUM> (see <FIG>) of the suspension.

Also with reference to the illustrated specific example, the main body 10A of each longitudinal arm constituted by the above mentioned element of pressed sheet-metal, comprises a front portion <NUM> which extends substantially in a vertical plane and ends with a front end edge defining a semi-circular cavity 12A in which the metal body <NUM> of the elastic bushing <NUM> is welded.

With reference to the drawings, the suspension system comprises a pair of wheel supports <NUM> rigidly connected to the two longitudinal arms <NUM>. In the specific illustrated example (see <FIG>, <FIG>), the two wheel supports <NUM> are rigidly connected to the two longitudinal arms <NUM> through two auxiliary tubular elements <NUM>. Each element <NUM> has a metal body welded to the main body 10A of the respective longitudinal arm <NUM> and has an outer end 70A projecting from an outer lateral surface of the respective longitudinal arm <NUM>, and an inner end 70B projecting from the inner lateral surface of the respective longitudinal arm <NUM>. In the illustrated example (<FIG>) the inner end 70B is shaped with an enlarged mouth. Also in the case of the illustrated example, each auxiliary element <NUM> is received and welded within semi-circular seats 11B defined by the lateral walls of the longitudinal arm <NUM>.

Also with reference to the specific illustrated example, each wheel support <NUM> has a lower portion <NUM> with a cup-like cylindrical shape, which is mounted and welded above the inner end 70A of the respective auxiliary tubular element <NUM>. Naturally, these details of construction are provided herein purely by way of example, since it is clearly understood that the present invention is of general application and may therefore be used also with a configuration of the suspension elements different from that described herein.

Also with reference to the specific illustrated example, above the auxiliary elements <NUM>, there are welded two brackets <NUM> (<FIG>) for the articulated connection of the lower ends of two shock-absorber units <NUM>, whose upper ends are to be connected to the vehicle structure.

An essential component of the present invention is constituted by a cross-member <NUM> in the form of a main tubular element which is configured to rigidly connect the auxiliary tubular elements <NUM> to each other in the rigid axle suspension configuration (<FIG>) or for rigidly connecting the two longitudinal arms <NUM> to each other at intermediate positions between the front ends and the rear ends of these arms, in the twist axle suspension configuration (<FIG>).

With reference to the rigid axle suspension configuration shown in <FIG>, for the main tubular element <NUM> a first mounting position is selected, in which the opposite ends of element <NUM> are received and welded within the inner ends 70B of the auxiliary tubular elements <NUM>.

In this configuration, therefore, the element <NUM> is arranged coaxially to the two auxiliary elements <NUM> carrying the wheel supports <NUM>.

Furthermore, with reference in particular to <FIG>, in the rigid axle suspension configuration, there is provided an auxiliary element <NUM> in form of a stabilizing rod having one end 100A provided with an attachment for the articulated connection to a bracket <NUM> welded on one of the two auxiliary elements <NUM>. At the opposite end, the stabilizing bar <NUM> has an attachment 100B for the articulated connection to the vehicle structure. The stabilizing bar <NUM> is configured for extending transversely with respect to the longitudinal direction of the vehicle.

In the twist axle suspension configuration shown in <FIG>, the main tubular element <NUM> is not engaged within the auxiliary tubular elements <NUM>, which therefore have their inner ends 70B completely free, while element <NUM> has its ends welded to the two longitudinal arms <NUM> at intermediate positions between the front ends and the rear ends of the arms <NUM>. However, in this case the structure of each longitudinal arm <NUM> comprises, in addition to the main body 10A which has been described above, also an auxiliary body 10B comprising an element of pressed sheet-metal welded to the main body 10A. The auxiliary body 10B has a vertical wall <NUM> which is arranged at a position substantially parallel and spaced apart with respect to wall <NUM> of the main body 10A and terminating with a front end 13A having a semi-circular cavity, similar to that provided at the end 12A of wall <NUM>, for receiving the metal body <NUM> which surrounds the body <NUM> of elastomeric material of an elastic bushing <NUM>. The body <NUM> is welded within its seat to the end 12A.

The walls <NUM>, <NUM>, which are spaced apart from each other, define thereby an outer lateral wall and an inner lateral wall of the longitudinal arm <NUM>.

The auxiliary body 10B also has an upper wall <NUM> which is supported on a horizontal flange of the vertical wall <NUM> of the main body 10A, as well a further horizontal flange 12C of a vertical tab defined by the main body 10A. Finally, the upper wall <NUM> of the auxiliary body 10B has a rear end with appendages <NUM> which rest on an upper circumferential flange of wall 11A of the main body 10A.

At the overlapped walls of the main body 10A and the auxiliary body 10B, these walls are rigidly connected to each other by welding, so that the structure of each longitudinal arm acquires a box-like configuration suitable to a twist axle suspension. In the coupled condition, the main body 10A and the auxiliary body 10B leave seats 11B free for receiving the auxiliary tubular body <NUM>.

In the case of the illustrated example, each auxiliary body 10B has a circular aperture <NUM> through which there can be introduced the respective end of the main tubular body <NUM>. At the aperture <NUM>, to the auxiliary body 10B there is welded (at two slots 17B) a further element <NUM> of sheet-metal, located on the side of the wall of body 10B opposite to the side from which the element <NUM> is introduced, so that this element <NUM> forms an integral part of the inner lateral wall of the longitudinal arm. The corresponding end of element <NUM> is inserted through aperture <NUM> up to come in contact with element <NUM>. In this condition, the element <NUM> is welded to the inner lateral wall of the longitudinal arm, defined by the body 10B and the element <NUM>.

Apart from the above, the structure of the suspension system in the twist axle suspension configuration shown in <FIG> is identical to that shown with reference to <FIG>, except for that in this case the stabilizing bar <NUM> is eliminated. In other words, all the elements of the suspension system which are shown in <FIG>, except for the stabilizing bar <NUM>, constitute common parts of the suspension system in the rigid axle suspension configuration and in the twist axle suspension configuration. In the case of a rigid axle suspension configuration, the element constituted by the stabilizing bar <NUM> is added, whereas in the case of the twist axle suspension configuration, the elements 10B and <NUM> are added, which complete the structure of each longitudinal arm.

Due to the above described features, the suspension system according to the invention may be configured as a rigid axle suspension or a twist axle suspension without implying complicated and expensive operations for shifting from one type of configuration to the other. In this way, the producer can simplify the production process and can rationalize and further standardize the suspension components.

In the case of a light-duty vehicle, it can be provided for example that the rigid axle suspension configuration is adopted for a vehicle model with electric traction, in order to leave a greater space free between the longitudinal arms of the suspension for housing the supply electric batteries.

In the illustrated example, the main tubular element <NUM> and the auxiliary tubular elements <NUM> each have a transverse cross-section having a circular shape. However it is possible to adopt cross-section of any different shape, for example of oval shape for elements <NUM>, <NUM>.

Claim 1:
Motor-vehicle rear suspension system, comprising:
- a pair of longitudinal arms (<NUM>), having front ends carrying swivel joints (<NUM>) for the articulated connection to a vehicle supporting structure (<NUM>) and rear ends carrying respective wheel supports (<NUM>),
- a cross-member in the form of a main tubular element (<NUM>), having opposite ends configured to be rigidly connected to the two longitudinal arms (<NUM>),
wherein said main tubular element (<NUM>) and said longitudinal arms (<NUM>) are configured in such a way that said main tubular element (<NUM>) can be rigidly connected to the longitudinal arms (<NUM>) in any of two selectable mounting positions:
- a first mounting position, in which said main tubular element (<NUM>) is rigidly connected to the longitudinal arms (<NUM>) at a position substantially coaxial with the wheel supports (<NUM>) so as to define a rigid axle suspension,
- a second mounting position, in which said main tubular element (<NUM>) is rigidly connected to the longitudinal arms (<NUM>) at positions intermediate between the front ends and the rear ends of the longitudinal arms (<NUM>), so as to define a twist axle suspension,
wherein each wheel support (<NUM>) is rigidly connected to the respective longitudinal arm (<NUM>) through a respective auxiliary tubular element (<NUM>), having an outer end projecting from an outer lateral surface of the longitudinal arm (<NUM>) and rigidly connected to the wheel support (<NUM>) and an inner end projecting from an inner lateral surface of the longitudinal arm (<NUM>),
wherein said first mounting position said main tubular element (<NUM>) has its opposite ends rigidly connected to the inner ends (70B) of the two auxiliary tubular elements (<NUM>),
wherein each longitudinal arm (<NUM>) has a main body (10A) of sheet-metal and an auxiliary body (10B) also made of sheet-metal and configured to be welded to the main body (10A) only in the twist axle suspension configuration, so that said main body (10A) and said auxiliary body (10B) respectively define an outer lateral wall (<NUM>) of the longitudinal arm and an inner lateral wall (<NUM>) of the longitudinal arm, which are spaced apart from each other, and wherein in said second mounting position of the main tubular element (<NUM>) corresponding to the twist axle suspension configuration, said main tubular element (<NUM>) has end portions each welded to the inner lateral wall (<NUM>) of the respective longitudinal arm (<NUM>).