Suspension system for a motor vehicle including a pair of oscillating arms, a transverse leaf spring, and related connection units

Abstract

Suspension system (1) for a motor vehicle, comprising a transverse leaf spring (2) configured to be arranged transversely with respect to the longitudinal direction of the vehicle, wherein each end portion (2'') of the leaf spring (2) is connected to an outer end portion of the oscillating arm (3) by means of a connection unit (10) comprising: - a spherical joint (11) comprising a spherical body (12) and a first stem (13) rigidly connected to the oscillating arm (3), - an auxiliary coupling body (14) comprising a receptacle (15) engaged on the spherical body (12) and a second stem (16) rigidly connected to the end portion (2'') of the leaf spring (2).

Description

[0001] Suspension system for a motor vehicle including a pair of oscillating arms, a transverse leaf spring, and related connection units

[0002] TEXT OF THE DESCRIPTION

[0003] Field of the invention

[0004] The present invention relates to motor vehicle suspension systems, of the type comprising,

[0005] - a pair of wheel carriers,

[0006] - a pair of suspension oscillating arms respectively connected to a lower connection portion of the wheel carrier, by means of at least one attachment element,

[0007] - a transverse leaf spring arranged transversely with respect to the longitudinal direction of the vehicle,

[0008] - wherein each end portion of the leaf spring is connected to an outer end portion of the oscillating arm by means of a connection unit.

[0009] Prior art

[0010] Suspension systems of the aforementioned type have been in use since long time. Solutions currently adopted for connecting the end portions of the transverse leaf spring with the oscillating arms involve rigid elements associated with elastomeric material elements suitable for realizing an independent wheel suspension, making it necessary to use an anti-roll system, for example a conventional anti-roll bar or active-type systems. These solutions are not considered fully satisfactory, both from the point of view of the suspension's dynamic response and from the point of view of the overall durability of the elastomeric material connection elements.

[0011] Object of the invention

[0012] The object of the present invention is to provide a suspension system of the aforementioned type that is particularly effective, both from the point of view of vehicle dynamics and from the point of view of overall durability, while minimizing the number of components required to meet these needs.

[0013] Summary of the invention

[0014] According to the invention, one or more of the aforementioned objects are achieved by means of a suspension system for a motor vehicle, comprising:

[0015] - a pair of wheel carriers,

[0016] - a pair of suspension oscillating arms respectively connected to a lower connection portion of the wheel carrier, by means of at least one attachment element,

[0017] - an auxiliary frame,

[0018] - a transverse leaf spring arranged transversely with respect to the longitudinal direction of the vehicle, connected to the auxiliary frame by means of two elastic bushings arranged symmetrically at respective intermediate portions between the center of the leaf spring and its end portions, - wherein each end portion of the leaf spring is connected to an outer end portion of the oscillating arm, by means of a connection unit comprising:

[0019] - a spherical joint comprising a spherical body and a first stem rigidly connected to the oscillating arm,

[0020] - an auxiliary coupling body comprising a receptacle engaged on the spherical body and a second stem rigidly connected to the end portion of the leaf spring.

[0021] Brief description of the drawings

[0022] The invention will now be described in detail with reference to the accompanying drawings, provided purely by way of non-limiting example, in which:

[0023] Figure 1 is a perspective view of a suspension system according to one embodiment of the invention, including a transverse leaf spring,

[0024] Figure 2 is a further perspective view of the transverse leaf spring illustrated in the previous figures,

[0025] - Figure 3 is an enlarged scale sectional view of a connection unit arranged to connect a suspension oscillating arm and an end portion of the leaf spring, in accordance with possible embodiments of the invention, and

[0026] - Figure 4 is a perspective view highlighting a deformed dynamic condition of the suspension leaf spring incorporating the aforementioned connection units, compared to a prior art suspension.

[0027] Detailed description of the invention

[0028] In the following description, various specific details are illustrated for the purpose of providing an in-depth understanding of examples of one or more embodiments. The embodiments may be implemented without one or more of the specific details, or with other methods, components, materials, etc.

[0029] In other instances, known structures, materials or operations are not shown or described in detail to avoid obscuring various aspects of the embodiments.

[0030] The reference to "one embodiment" in the context of this description indicates that a particular configuration, structure or characteristic described in relation to the embodiment is included in at least one embodiment.

[0031] Therefore, phrases such as "in one embodiment", possibly present in various places in this description, do not necessarily refer to the same embodiment. Furthermore, particular configurations, structures or characteristics may be suitably combined in one or more embodiments and / or associated with the embodiments in a different manner from that illustrated here, so that for example a characteristic exemplified here in relation to one figure may be applied to one or more embodiments exemplified in a different figure.

[0032] The references illustrated here are for convenience only and therefore do not delimit the scope of protection or the extent of the embodiments.

[0033] In Figure 1, reference number 1 indicates, as a whole, a possible embodiment of a suspension system according to the invention, comprising a transverse leaf spring 2 extending along a transverse axis with respect to the longitudinal direction of the vehicle, below the body.

[0034] The suspension system 1 illustrated in Figure 1 represents an example of a vehicle rear suspension, incorporating the principles underlying the invention. However, the present invention is similarly applicable to different archetypes of motor vehicle suspension with transverse leaf spring, for front axle or rear axle. In a per se known manner, the suspension system 1 comprises for each wheel a wheel carrier (not shown) and a suspension oscillating arm 3. Each oscillating arm 3 comprises an outer end portion arranged to be connected to a lower connection portion of the wheel carrier, by means of at least one attachment element 4, and an inner end portion connected to an auxiliary suspension frame 5 rigidly connected to the vehicle floor.

[0035] In accordance with the embodiment illustrated in the accompanying figures, the aforementioned attachment elements 4 are connecting levers having an inner end connected to the arm 3 and an outer end connected to the wheel carrier. Naturally, the aforementioned attachment elements may also be configured differently from what is illustrated, so as to interface effectively with the neighboring suspension components.

[0036] As indicated above, the suspension 1 comprises a transverse leaf spring 2 extending along a transverse axis with respect to the longitudinal direction of the vehicle, below the body. The leaf spring 2 thus comprises two opposing main faces, in particular an upper face facing towards the vehicle floor and an opposite lower face.

[0037] Preferably, the leaf spring 2 is made as a single piece of steel. In other embodiments, the leaf spring 2 is made as a single piece of composite material, including a plastic matrix reinforced with fibers, for example carbon fibers.

[0038] The leaf spring 2 comprises a central portion 2' and two end portions 2". The leaf spring 2 is connected to the auxiliary frame 5 by means of two elastic bushings 6 arranged symmetrically at intermediate portions of the leaf spring 2, between the central portion 2' and the end portions 2"

[0039] According to possible embodiments, the transverse leaf spring 2 is configured as a leaf spring that counteracts the vertical movements of the two wheel carriers. The width of the leaf spring - i.e. the distance along the longitudinal direction of the vehicle between a front edge and a rear edge of the leaf spring - may vary along the longitudinal extension of the leaf spring.

[0040] In some embodiments, note that the end portions 2" of the leaf spring 2 have a tapered shape with width in the longitudinal direction of the vehicle that decreases towards the wheel carriers. Note that by appropriately varying the profile and / or shape and / or thickness in the central area of the leaf spring 2, it is possible to obtain different stabilization effects depending on the weights and performance of the vehicle on which the previously described suspension system is to be applied.

[0041] The above-described configuration of the leaf spring 2 allows it to effectively perform both kinematic guiding functions and vertical wheel control functions during vertical jounce travel.

[0042] As previously indicated, the leaf spring 2 is connected to the auxiliary frame 5 by means of two elastic bushings 6 arranged symmetrically at intermediate portions of the leaf spring 2, between the central portion 2' and the respective end portion 2". Each elastic bushing 6 comprises an external housing 7 preferably made of metallic material and an elastomeric material portion 8 inside the housing 7 surrounding the leaf spring 2 on all its sides at said intermediate portion. Note that the presence of elastomeric material 8 inside the housing 7 is necessary to provide adequate damping of the leaf spring's oscillations, particularly along the vertical direction of the vehicle.

[0043] According to a further characteristic, each elastic bushing 6 comprises at least two seats 9 for receiving respective fastening elements connectable to the auxiliary frame 5. Observing Figure 2, note that said seats 9 are formed on the external housing 7, spaced apart and aligned in the longitudinal direction of the vehicle, and are also formed along respective end flanges 7' of the housing 7, on the sides of the leaf spring 2. It will therefore be appreciated that the bushings 6 secure the leaf spring 2 below the body, effectively distributing the weight of the leaf spring and related stresses, while also helping to effectively counteract leaf spring translations during vehicle dynamics, mainly along its longitudinal direction (i.e., along the transverse direction of the vehicle), but also along its transverse direction (i.e., along the longitudinal direction of the vehicle).

[0044] Note also that the elastomeric material 8 inside the housing 7 may engage with respective parts of the leaf spring, allowing small movements of the leaf spring 2 along its longitudinal direction (i.e., along the transverse direction of the vehicle)

[0045] As previously indicated, each oscillating arm 3 comprises an outer end portion connected to a lower connection portion of the wheel carrier by means of at least one attachment element 4.

[0046] According to a further characteristic, each end portion 2" of the leaf spring 2 is connected to the outer end portion of the oscillating arm 3 by means of a connection unit 10 described below.

[0047] As illustrated in Figure 3, the connection unit 10 comprises:

[0048] - a spherical joint 11 comprising a spherical body 12 and a first stem 13 rigidly connected to the oscillating arm 3,

[0049] - an auxiliary coupling body 14 comprising a receptacle 15 engaged on the spherical body 12 and a second stem 16 rigidly connected to the end portion 2" of the leaf spring 2.

[0050] It will therefore be appreciated that the connection unit 10 comprises a doublestem spherical joint for connecting with the leaf spring 2 and the oscillating arm 3.

[0051] According to a further characteristic, the first stem 13 is also connected to said attachment element 4. More specifically, in the final assembled configuration, a first portion of the first stem 13 passes through a corresponding connection point of the oscillating arm 3, and a second portion of the first stem 13 passes through a corresponding connection point of the attachment element 4. The resulting connection is tightened by means of a first locking nut 17 tightened along an end portion of the first stem 13.

[0052] Similarly, with reference to the auxiliary coupling body 14, the second stem 16 passes through a corresponding connection point of the end portion 2" of the leaf spring 2. The resulting connection is tightened by means of a second locking nut 18 tightened along an end portion of the second stem 14.

[0053] With reference to Figure 3, note that in the final assembled configuration on the vehicle suspension, the end portions 2" of the leaf spring 2 extend along a main plane that is at a higher level than the oscillating arms 3. It will therefore be appreciated that each connection unit 10 has the spherical body 12 spaced between the lower face of the leaf spring 2 and an upper face of the oscillating arm 3, such that the first stem 13 extends downward from the spherical body 12 and the second stem 16 extends upward from the spherical body 12 to realize said connections.

[0054] The attachment position of the connection unit relative to the oscillating arm and the leaf spring - with reference to the transverse horizontal direction of the vehicle - affects the transfer of vertical loads to the opposite wheel.

[0055] The suspension system with connection unit 10 as described above guarantees only three degrees of freedom (i.e., rotations about three axes). Thanks to the adoption of such connection units 10, the suspension can ultimately be realized without an anti -roll bar, considering that in vehicle dynamics (especially under asymmetric jounce conditions) a semi -independent wheel dynamic behavior is obtained, since the compression condition on one side of the leaf spring can have positive effects on the rebound condition on the opposite side, effectively implementing the functions of an antiroll bar in the leaf spring itself.

[0056] Figure 4 illustrates a deformed condition of the leaf spring 2 (in response to relative stresses) equipped with connection units 10 as described above (three degrees of freedom), compared to a leaf spring 2' with traditional connections (six degrees of freedom). Note that with equal jounce of the outer wheel in a curve, the oscillating arms 3 related to the leaf spring 2 equipped with connection units 10 - under asymmetric jounce conditions - exhibit less rebound travel than arm 3', producing an anti-roll bar-like effect.

[0057] Naturally, while maintaining the principle of the invention, construction details and embodiments may vary widely from what has been described and illustrated purely by way of example, without thereby departing from the scope of the present invention.

Claims

CLAIMS1. Suspension system (1) for a motor vehicle, comprising:- a pair of wheel carriers,- a pair of suspension oscillating arms (3) respectively connected to a lower connection portion of the wheel carrier by means of at least one attachment element (4),- an auxiliary frame (5),- a transverse leaf spring (2) configured to be arranged transversely with respect to the longitudinal direction of the vehicle, connected to the auxiliary frame (5) by means of two elastic bushings (6) arranged symmetrically at respective intermediate portions between the center of the leaf spring (2) and its end portions (2"),- wherein each end portion (2") of the leaf spring (2) is connected to an outer end portion of the oscillating arm (3) by means of a connection unit (10) comprising:- a spherical joint (11) comprising a spherical body (12) and a first stem (13) rigidly connected to the oscillating arm (3),- an auxiliary coupling body (14) comprising a receptacle (15) engaged on the spherical body (12) and a second stem (16) rigidly connected to the end portion (2") of the leaf spring (2).

2. Suspension system (1) according to claim 1, wherein the first stem (13) is also connected to said attachment element (4).

3. Suspension system (1) according to claim 2, wherein a first portion of the first stem (13) passes through a corresponding connection point of the oscillating arm (3), and a second portion of the first stem (13) passes through a corresponding connection point of the attachment element (4).

4. Suspension system (1) according to claim 3, wherein the connection unit (10) comprises a first locking nut (17) tightened along an end portion of the first stem (13).

5. Suspension system (1) according to claim 2, wherein the spherical body (12) is spaced between the lower face of the leaf spring (2) and an upper face of the oscillating arm (3), such that the first stem (13) extends downward from the spherical body (12) and the second stem (16) extends upward from the spherical body (12), with reference to the assembled condition on the vehicle.

6. Suspension system (1) according to claim 1, wherein each attachment element (4) is a connecting lever having an inner end connected to the arm (3) and an outer end connected to the wheel carrier.

7. Suspension system (1) according to claim 1, wherein the end portions (2") of the leaf spring (2) have a tapered shape with width in the longitudinal direction of the vehicle that decreases towards the wheel carriers.

8. Suspension system (1) according to claim 1, wherein each elastic bushing (6) comprises an external housing (7) and an elastomeric material portion (8) inside the housing (7) surrounding the leaf spring (2) on all its sides at said intermediate portion, wherein each elastic bushing (6) comprises at least two seats (9) for receiving respective fastening elements connectable to the auxiliary frame (5).

9. Suspension system (1) according to claim 8, wherein said seats (9) are formed on the external housing (7), spaced apart and aligned in the longitudinal direction of the vehicle, and are also formed along respective end flanges (7') of the housing (7), on the sides of the leaf spring (2).

10. Vehicle comprising a suspension system (1) according to any one of the preceding claims.

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