Multipurpose transverse leaf spring with motor-driven stiffness regulator for motor vehicles

Abstract

Motor vehicle suspension system comprising a transverse leaf spring carrying at its ends (1) respective wheel supports (2), characterised in that it is provided with a motor-driven stiffness regulator (6, 12) arranged between each end (1) of the transverse leaf spring and the structure (S) of the motor vehicle.

Description

[0001] “Multipurpose transverse leaf spring with motor-driven stiffness regulator for motor vehicles”

[0002] ****

[0003] Field of the invention

[0004] The present invention generally relates to motor vehicle suspension systems comprising a pair of wheel supports, a multipurpose transverse leaf spring formed by a plate arranged orthogonally with respect to the longitudinal direction of the motor vehicle and carrying at its ends the wheel supports, and connecting members for coupling the transverse leaf spring to the structure of the motor vehicle arranged near said ends.

[0005] State of the prior art

[0006] Multipurpose transverse leaf springs for motor vehicle suspensions are for example disclosed by the documents KR102453786 B1 as well as by the Italian patent applications numbers 102023000009723 and 102023000021240, not published at the priority date of this application.

[0007] Leaf springs thus made, which can be used both for the front suspension and for the rear suspension, integrate in the same component the functions of transversal arm, suspension spring and stabiliser bar. Varying the profile and / or the shape, and / or the suspension and / or the materials (steel or composites) of the leaf spring may allow to obtain various effects both in terms of elasticity and in terms stabilisation, depending on the weights and the performance of the motor vehicle to which the transverse leaf spring is designed to be applied. For example, the transverse leaf spring may be used as a substitute for MacPherson strut suspensions in which the arm, spring and stabiliser bar consist of components that are distinct and separated from each other.

[0008] At the ends of the transverse leaf spring, which as mentioned integrates the functions of transversal arm, spring and stabiliser bar, there may be applied various types of connections such as for example spherical heads, cylindrical hinges and / or joints so as to be interfaced to the nearby components of the suspension such as a mounting, shock absorber, etc.

[0009] Typically, the connecting members for coupling the transverse leaf spring to the structure of the motor vehicle are arranged symmetrically at two respective intermediate areas between the centre of the leaf spring and the wheel supports.

[0010] Summary of the invention

[0011] The object of the present invention is to provide a suspension system with an improved transverse leaf spring, in particular as regards the possibility of obtaining a gradual stiffness curve and ideal as much as possible in the stroke motion of the suspension system, and which can also be regulated in an efficient and practical manner.

[0012] According to the invention, this object is attained thanks to a suspension system having the characteristics indicated in the attached claims, and more particularly due to the fact that it is provided with a motor- driven stiffness regulator fitted between each end of the transverse leaf spring and the structure of the motor vehicle and which can be controlled from a remote position.

[0013] In embodiments of the invention, each stiffness regulator comprises at least one rigid bracket connected cantilevered to the structure of the vehicle and bearing a respective elastic pad facing the corresponding end of the transverse leaf spring and whose position is variable parallel to the longitudinal direction of the transverse leaf spring.

[0014] Each bracket conveniently supports an actuator mechanism which can be controlled from a remote position including a worm screw and nut screw assembly engaged with said screw and carrying the elastic pad, in which the screw is driven in rotation by an electric motor to translate the nut screw with the elastic pad along a longitudinal slot of the bracket.

[0015] The invention allows to obtain, in a practical and functional manner, an "ideal" and gradual stiffness curve in the stroke motion of the transverse leaf spring and therefore of the suspension system, so as to be able to adapt it to the various travel conditions in a practical and easy manner, even directly by the driver of the vehicle.

[0016] Brief description of the drawings

[0017] The invention will now be described in detail, purely by way of nonlimiting example, with reference to the attached drawings, wherein:

[0018] - figure 1 is a schematic perspective view of an end part of a multipurpose transverse leaf spring with stiffness regulator which forms an embodiment of the motor vehicle suspension system according to the invention,

[0019] - figure 2 is a front elevational view of figure 1 ,

[0020] - figure 3 is a view similar to figure 2 which exemplifies the regulation mode of the stiffness regulator,

[0021] - figure 4 is a perspective view of the actuator mechanism of the stiffness regulator,

[0022] - figure 5 is a longitudinal cross-sectional view of a part of figures 1 - 3,

[0023] - figure 6 is a perspective view and in larger scale of a part of figure 5, and

[0024] - figure 7 is an exploded perspective view of figure 5.

[0025] Detailed description of the invention

[0026] In the following description there are shown the various specific details aimed at a deeper understanding of an embodiment of the invention. Other embodiments may be obtained without one or more of the specific details, or with other methods, components, materials, etc.

[0027] The reference numerals described herein with reference to the drawings are indicated only for the sake of simplicity and do not delimit the scope of protection of the invention.

[0028] Initially with reference to figures 1 and 2, indicated with 1 is an end of a transverse leaf spring of the generally known type, which can be used in a motor vehicle suspension system with three functions: transversal arm, spring and stabiliser bar of the suspension.

[0029] The transverse leaf spring conventionally consists in an elongated and shaped body made of steel with constant and / or variable thickness, or also made of composite material with single plate or multiple plates.

[0030] The transverse leaf spring is designed to be arranged orthogonally with respect to the longitudinal direction of the motor vehicle and at its end 1 there is fixed a coupling element 2 for example a spherical head 3 (or a cylindrical hinge and / or a joint of the known type) adapted to be interfaced to the nearby components of the suspension of one of the wheels, whether front or rear, such as a mounting, a shock absorber, etc. The other end of the transverse leaf spring, not shown in the drawings for the sake of simplicity, has a configuration that is entirely symmetrical and arranged in a mirror-like fashion with respect to the one described herein: therefore, the following identically applies to both the ends of the transverse leaf spring.

[0031] The coupling of the transverse leaf spring to the structure of the motor vehicle, schematically shown with S in figures 2 and 3, is obtained in the end area 1 (same case applying to the opposite end) through connecting members which in the case of the shown embodiment consist of two pairs of bushes 4 bearing respective vertical pins 5, for example threaded, for fixing to the structure S. The structure of the bushes 4 is not described in detail herein, and it should be observed that the conformation of the connnecting members of the transverse leaf spring could be of a different type, even conventional.

[0032] According to the peculiar characteristic of the invention with the transverse leaf spring there is operatively associated a motor-driven stiffness regulator, more particularly interposed between the end 1 and the structure S of the motor vehicle. An identical stiffness regulator is also applied on the other end of the transverse leaf spring, regarding which the description below identically applies as specified above.

[0033] In the embodiment described herein, the stiffness regulator comprises a substantially rigid bracket 6, fixed cantilevered to the structure

[0034] 5 of the vehicle above the end 1 of the transverse leaf spring and bearing an elastic pad 7, typically made of a generally conical-shaped elastomeric material, which is normally spaced vertically from the upper face of the transverse leaf spring. The distance is such that when the end 1 of the transverse leaf spring is deformed bending upwards by an extent greater than the pre-established value, it is brought into contact with the elastic pad 7 which counteracts a further deformation thereof.

[0035] It should be observed that, in an embodiment not shown, the bracket

[0036] 6 with the elastic pad 7 could also be positioned below the transverse leaf spring, and in a further embodiment not shown there could also be provided for two brackets 6 with respective elastic pads 7 arranged on opposite sides, that is above and below, of the end 1 (as well as of the opposite end) of the leaf spring. The stiffness regulator according to the invention may therefore operate on the transverse leaf spring only in the damping stroke (like in the shown case for example) or only in the shock stroke of the suspension, or even in both damping and shock strokes.

[0037] The bracket 6 has a generally triangular configuration with a base 8 provided with a pair of holes 9 for fixing to the structure S of the vehicle through pins 5 of the couplings 4. The elastic pad 7 is carried on the side of the vertex 10 of the bracket 6 opposite to the base 8 and, as observable below, its position can be modified parallel to the longitudinal direction of the transverse leaf spring.

[0038] Now, with greater detailed reference to figures 4 to 7, the bracket 6 has a central longitudinal slot 1 , normally closed by a lid 18, along which the elastic pad 7 can translate for example between the distal position shown in the upper part of figure 3 and the proximal position shown in the lower part of the same figure. The translation which can be controlled from a remote position through an actuator mechanism indicated in its entirety with 12 and including an irreversible worm screw 13 extending axially through the slot 11 , and a nut screw 14 engaged with the screw 13 and carrying the elastic pad 7. More particularly, the nut screw 14 is laterally provided with wheels 15 in rolling contact with respective tracks 16 located on sides opposite to the slot 11 . The tracks 16 are obtained with different wave-like profiles and of harmonic / flexible material so as to always ensure the contact and in any position between the minimum and maximum stroke carried out by the pad 7.

[0039] An electric motor 17, which can be controlled from a remote position as mentioned, drives in rotation the screw 13 to translate the nut screw 14, and therefore the elastic pad 7, between the distal and proximal positions of figure 3.

[0040] In operation, as mentioned above, the elastic pad 7 is normally spaced vertically from the end 1 of the transverse leaf spring: when such end 1 is deformed bending beyond a certain value, it is brought into contact with the elastic pad 7, which limits further bending thereof: depending on the position of the elastic pad 7 set from a remote position through the actuator mechanism 12, such limitation may be more or less significant, which evidently increases as the pad 7 nears the vertex 10 of the bracket 6 and therefore the wheel of the vehicle. It should be observed that the actuator mechanism 12 could be different from the one shown with reference to the example, and for example use a rack and toothed sprocket assembly, in any case driven by a remote- controlled electric motor. Also the system for fixing the bracket 6 to the structure S of the vehicle can be obtained differently and even directly, instead of through the bushes 4.

[0041] Obviously, the construction details and the embodiments may widely vary with respect to what has been described and illustrated, without departing from the scope of protection of the present invention as defined in the claims that follow.

Claims

CLAIMS1. Motor vehicle suspension system comprising:- a transverse leaf spring formed by a plate spring arranged orthogonally with respect to the longitudinal direction of the motor vehicle and carrying at its ends (1 ) respective wheel supports (2),- connecting members (4) for coupling the transverse leaf spring to the structure (S) of the motor vehicle arranged near said ends (1 ), characterised in that it is provided with a motor-driven stiffness regulator (6, 12) arranged between each end (1 ) of the transverse leaf spring and the structure (S) of the motor vehicle.

2. Suspension system according to claim 1 , characterised in that each stiffness regulator comprises at least one rigid bracket (6) connected cantilevered to the structure (S) of the vehicle and bearing a respective elastic pad (7) facing the corresponding end (1 ) of the transverse leaf spring and whose position is variable parallel to the longitudinal direction of the transverse leaf spring.

3. Suspension system according to claim 2, characterised in that said elastic pad (7) is normally spaced vertically from the end (1 ) of the transverse leaf spring.

4. Suspension system according to claim 2 or claim 3, characterised in that said bracket (6) is arranged above said end (1 ) of the transverse leaf spring.

5. Suspension system according to claim 2 or claim 3, characterised in that said bracket (6) is arranged below said end (1 ) of the transverse leaf spring.

6. Suspension system according to any one of claims 2 to 5, characterised in that said bracket (6) has a longitudinal slot (11 ) along which said elastic pad (7) is displaceable.

7. Suspension system according to claim 6, characterised in that said bracket (6) supports an actuator mechanism (12) which can be remotely controlled and including an irreversible worm screw (13) and nut screw (14) assembly engaged with said screw (13) and carrying said elastic pad (7), wherein the screw (13) is rotated by an electric motor (17) to translate said nut (14) along said slot (11 ).

8. Suspension system according to claim 7, characterised in that said nut screw (14) is provided with lateral wheels (15) in rolling contact on respective tracks (16) of said bracket (6).

9. Suspension system according to claim 8, characterised in that the tracks (16) are made with different wave profiles and of harmonic / flexible material to always guarantee contact in any position of the elastic pad (7).

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