Filter block of a strut of an automotive vehicle suspension system

Abstract

Title: Filter block of a strut of a motor vehicle suspension system. Filter block (20) of a strut (1) of a motor vehicle suspension system, said filter block (20) being configured to support and filter types of stresses with an axial component and a radial component, characterized in that it comprises a first annular filter portion (24) which forms a central portion of the filter block and a second distinct annular filter portion (26) which forms an external portion of the filter block, said annular filter portions (24, 26) being radially separated from each other by an annular insert (28) interposed between them, to allow the annular filter portions to respectively primarily handle one of the types of stresses. (Figure 2)

Description

Title of the invention: Filter block for a strut of an automotive vehicle suspension system

[0001] The present invention relates to the field of suspension devices for motor vehicles. More particularly, the present invention relates to the field of struts and their upper part connected to the vehicle structure, and the filter blocks that equip these struts.

[0002] A strut is a major structural element of a suspension system equipping a motor vehicle, which allows both to ensure the ride height and to limit the travel of a wheel of the vehicle in order to guarantee optimal comfort for the vehicle's passengers.

[0003] A strut includes, in particular, a shock absorber and a coil spring. The shock absorber comprises a cylinder and a rod mounted telescopically within this cylinder. The shock absorber rod is capable of sliding through a predetermined maximum axial stroke. The coil spring is arranged coaxially with the shock absorber cylinder.

[0004] A strut is, in its upper portion, connected to the chassis of the motor vehicle and, at its opposite end, or lower end, has means for connecting to a wheel of the motor vehicle, for example, via a wheel hub. The free end of the rod contributes to forming this upper portion of the strut and is therefore intended to be connected to a structural element of the vehicle, and a filter block is interposed between this free end of the rod and the body structure of the vehicle on which the strut is mounted.

[0005] On certain vehicles, and in particular those equipped with a MacPherson type suspension, the filter block ensuring the connection of the strut with the body fulfills a function of filtering the solid vibrations which rise from the wheel to the body.

[0006] Among these filter blocks, there are, in particular, load-bearing filter block technologies and non-load-bearing filter block technologies, which are distinguished from one another by the different stresses borne by the filter block and the rubber used to form it. The load-bearing filter block, with the shock absorber's helical spring pre-stressed between a lower cup fixed to the shock absorber cylinder and an upper cup, or spring cup, fixed to the upper end of the shock absorber rod, and with a filter block rubber interposed between the spring cup, the shock absorber rod, and the vehicle structure, is the technology that makes it possible to consider ensuring the best overall filtration, as the solid-borne vibrations that travel from the wheel to the body are transmitted equally through the springs and the shock absorbers.

[0007] However, the filter block carrier in its current construction does not allow a good level of filtration of vibrations with radial components to be achieved because the configuration and position of the rubber are such that it must be flexible enough to filter solid vibrations while being stressed by vertical forces generated by the weight of the car which pass through the spring and the spring cup.

[0008] However, the significant vertical force from the weight of the vehicle pre-stresses the rubber and creates a phenomenon of stiffening of the rubber block, so that it may no longer be flexible enough to ensure the filtering of vibrations with an axial or radial component.

[0009] The present invention falls within this context and aims to provide a filter block for a strut of a motor vehicle suspension system, said filter block being configured to support and filter types of stresses with axial and radial components,

[0010] characterized in that it comprises a first annular filtering portion which forms a central portion of the filter block and a second distinct annular filtering portion which forms an external portion of the filter block, said annular filtering portions being separated radially from each other, by an annular insert interposed between them, to allow the annular filtering portions to respectively treat mainly one of the types of stress.

[0011] In this way, the inventors have imagined a new design of carrier filter blocks in which the filter portion, made in particular of rubber, is no longer made with a single block of material, so that the vertical force of the weight of the vehicle which is supported by the carrier filter block does not generate a stiffening of the whole block of material, and in particular of rubber.

[0012] It is ensured that a portion of the filter material remains flexible and unstressed under the weight of the vehicle. The material, particularly the rubber, forming the filter block is prevented from becoming rigid as a whole and losing its ability to filter given vibrations and contribute to the vibration and acoustic comfort of the vehicle's occupants. Since the ability of rubber to effectively filter vibrations depends on its low stiffness, it is particularly advantageous to preserve, according to the invention, a portion of rubber that is not prestressed by the weight of the vehicle and is capable of filtering vibrations, particularly those with a radial component.

[0013] In the invention, the inventors thus sought to decouple, in terms of force filtration, the rubber portion that cooperates with the spring and through which the vertical force due to the vehicle's weight is transmitted, from the rubber portion that serves to filter the radial forces transmitted by the shock absorber rod and the spring to the body. In other words, the filter block according to the invention allows for a radial separation of two filter portions, particularly rubber, so that the forces axial forces that strongly pre-stress one portion of rubber do not impact the other portion of rubber, and the latter can remain flexible and able to filter solid vibrations passing through it.

[0014] In the filter block according to the invention, the separate annular filter portions are intended to be arranged around a free end of a strut shock absorber rod, concentrically or coaxially, the notions of axiality and radiality being defined with respect to an axis of revolution of the filter block, corresponding to the axis of elongation of this shock absorber rod.

[0015] According to an optional feature of the invention, the annular insert comprises a flat annular ring which has an inner peripheral edge on which the first filtering annular portion is engaged and an outer peripheral edge on which the second filtering annular portion is engaged, the annular insert having a clear portion, which is not covered by either the first or the second filtering annular portion.

[0016] The presence of the open portion ensures that the material used to make the filter portion, in particular the rubber, is properly distributed into two distinct portions, which can be prestressed differently from each other. The radial arrangement of the annular insert between the filtering annular portions makes it possible for radial forces to be transmitted from one portion to the other, and therefore for the entire material of the filter block to participate in absorbing the vibrations corresponding to these radial forces, and for axial forces not to be transmitted from one filtering annular portion to the other, and therefore for only one of the annular filtering portions to be constrained by the weight of the vehicle.

[0017] According to an optional feature of the invention, the filtering annular portions are overmolded onto the annular insert. This ensures that the insert is held securely between the filtering annular portions and that the forces are properly transmitted between a filtering annular portion and the annular insert.

[0018] According to an optional feature of the invention, the annular insert is made of metallic, composite or plastic material.

[0019] According to an optional feature of the invention, the first annular filter portion and / or the second annular filter portion are made of rubber.

[0020] According to an optional feature of the invention, the two annular filter portions have different stiffness characteristics. This takes advantage of the benefits of separating the annular filter portions. Depending on the stresses to be absorbed by the annular filter portions, the stiffness of each of these annular filter portions can be adjusted.

[0021] According to an optional feature of the invention, the second annular filter portion has a stiffness value greater than that of the first annular filter portion. In other words, the annular filter portion, which is arranged across the transmission of axial forces due to the weight of the vehicle, via the shock absorber spring, is originally designed with a greater stiffness than the other annular filter portion, so that it can withstand more forces and so that the other, more flexible annular filter portion can effectively absorb the other forces, essentially radial, generated by the shock absorber.

[0022] According to an optional feature of the invention, the second annular filtering portion has a substantially flat axial end upper face and an axial end lower face equipped with a damping pad.

[0023] According to an optional feature of the invention, the damping pad has a substantially frustoconical shape, with a cross-section, in a plane parallel to the plane of the upper axial end face of the second annular filtering portion, which tends to decrease as one moves away from this upper axial end face.

[0024] As just described, the damping pad is taller than it is wide to properly support the significant axial forces coming from the spring while being not very stiff under radial force so as not to introduce too much stiffness which could impair the proper filtering of radial vibrations traveling up towards the body of the vehicle.

[0025] According to an optional feature of the invention, the damping pad has a larger axial dimension than its radial dimension.

[0026] According to an optional feature of the invention, the filter block comprises a tubular insert bonded to the material of the first annular filter portion in the vicinity of an internal border of this first annular filter portion. In particular, the first annular filter portion is overmolded onto the tubular insert.

[0027] According to an optional feature of the invention, the tubular insert is made of metallic, composite or plastic material.

[0028] According to an optional feature of the invention, the first annular portion has two substantially flat axial end faces, and the tubular insert extends axially from each of the two axial end faces. The tubular insert is in contact with the vehicle's structural elements to contribute to the transmission of axial forces via the shock absorber rod, while the first annular portion is free from axial contact. This is particularly advantageous in the context where this first filtering annular portion is intended to filter vibrations with a radial component without having to withstand axial forces that could alter its stiffness during vehicle operation.

[0029] The invention also relates to a strut of a motor vehicle suspension system comprising at least one shock absorber and a helical spring arranged around the shock absorber, said shock absorber comprising a cylinder and a rod mounted telescopically in this cylinder and whose free end cooperates with a filter block as previously mentioned, said filter block being interposed between the shock absorber and the body of the vehicle.

[0030] According to an optional feature of the invention, the filter block rests on a receiving cup for the helical spring solely via the second annular filter portion. In this way, the transfer of forces due to the vehicle's weight, acting axially through the helical spring, is ensured via the second annular filter portion. The radial separation of the annular portions within the filter block allows the first annular filter portion to remain unaffected by this transfer of axial forces.

[0031] Other features, details and advantages of the invention will become clearer upon reading the following description on the one hand, and the illustrative and non-limiting examples of embodiments given with reference to the accompanying drawings on the other hand, in which:

[0032] [Fig-1] is a schematic side view of the vehicle equipped with a strut according to one aspect of the invention;

[0033] [Fig.2] schematically represents an upper portion of a strut intended to be fixed to a motor vehicle, said [Fig.2] making visible the structure of a filter block equipping according to one aspect of the invention;

[0034] [Fig.3] represents the filter block of [Fig.2] in a perspective view.

[0035] The characteristics, variants and different embodiments of the invention These features can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variants of the invention may include only a selection of features, described hereafter in isolation from the other described features, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from prior art.

[0036] In the figures, the elements common to several figures retain the same reference.

[0037] In the detailed description that follows, the terms "axial" and "radial" refer to the axis of extension of the shock absorber equipping the strut, the term "axial" referring to an orientation parallel to this axis of extension while the term "radial" referring to an orientation perpendicular to this axis of extension and passing through this axis of extension.

[0038] Figure 1 shows the front of a motor vehicle 100 viewed from the side and a strut 1, here on the front left of the vehicle, forming part of the vehicle's suspension system. It should be noted that everything described for this strut can be applied to either side of a wheel assembly of the vehicle.

[0039] The strut 1 includes a shock absorber 2 with an axis of extension A comprising a cylinder 4 in which a rod 6 is mounted telescopically axially along the axis of extension A. A lower end of the cylinder 4 is connected to an associated steering wheel 8 of the vehicle, for example via a yoke (not shown here), while the free upper end 10 of the rod 6 is intended to be connected to a structural element 12 of the vehicle, such as a body panel. The rod 6 more particularly takes the form of a piston moving along the axis of extension A under the stress of compression and rebound forces transmitted by the vehicle's wheels in contact with the road.

[0040] The strut 1 is also equipped with a helical suspension spring 14 which allows for the elastic absorption of shocks. The spring 14 is arranged around the shock absorber rod 6. The spring 14 is mounted under constraint between a lower cup 16 and an upper cup 18. The lower cup 16 is here fixed to the cylinder 4 of the shock absorber 2, while the upper cup 18 is supported by the structural element 12 of the vehicle.

[0041] The strut 1 also includes a filter block 20 which is arranged around the free upper end 10 of the rod 6 and which is also interposed between the structural element 12 and the upper cup 18. This filter block 20 has the particular function of absorbing certain vibrations of the rod 6 to prevent them from being transmitted to the structure of the vehicle, for example to prevent the appearance of parasitic noises.

[0042] The strut 1 is particular according to the invention, as will be described in more detail below, especially in the configuration of the filter block 20 equipping this strut. More particularly, the filter block 20 comprises two specific filter portions which are decoupled, or separated, from each other, so that one of these filter portions can, in particular, absorb the axial forces generated by the weight of the vehicle, by the axial compression of the rod 6 and the helical spring 14, and so that the other of these filter portions can, more particularly, absorb the radial forces generated, in particular, by the helical spring 14.

[0043] Figure 2 schematically illustrates a cross-sectional view of the upper part of the strut 1 according to the invention. Figure 2 makes particularly visible the shock absorber rod 6 and the helical spring 14, extending along the elongation axis A of the shock absorber, as well as various components of the upper part of the strut 1, and the filter block 20.

[0044] As previously mentioned, the helical spring 14 is in contact, at the level of an upper coil, with the upper cup 18, and more particularly with a first face of this upper cup 18, and this upper cup 18 is linked, via a second face opposite to the first face, to an annular portion of the filter block 20.

[0045] The filter block 20 is interposed between this spring cup, or upper cup 18, and the structural element 12 of the vehicle and will be described in more detail below.

[0046] The free end 10 of the rod 6 extends beyond the filter block 20 to cooperate with a nut 21, the tightening of which on a threaded portion of the free end 10 of the rod 6 allows a rebound cup 22 to be clamped and thus the shock absorber rod 6 to be linked to the vehicle structure.

[0047] The filter block 20 according to the invention comprises two annular filter portions 24, 26 and an annular insert 28 which radially separates these two filter portions. It will be described with reference to [Fig. 2], which illustrates more particularly its interaction with the other components of the strut, and with reference to [Fig. 3], which illustrates the filter block alone.

[0048] The two annular filter portions consist of a first annular filter portion 24 and a second annular filter portion 26, distinct from the first annular filter portion 24. The annular insert 28 is connected to both the first annular filter portion 24 and the second annular filter portion 26. More particularly, the two annular filter portions 24, 26 are arranged concentrically around the free end 10 of the rod 6, being separated radially from each other by the annular insert 28 interposed between them.

[0049] The first filtering annular portion 24 is defined as being that arranged closest to the rod 6 and the second filtering annular portion 26 as being that arranged around the first filtering annular portion 24, at a distance from the axis of elongation of the rod 6.

[0050] The two filtering annular portions 24, 26 are overmolded onto the annular insert 28, respectively at a radial end thereof.

[0051] The annular insert 28 comprises a flat annular ring, that is to say, a part of revolution whose axial thickness is much smaller than its radial dimension. The annular insert 28 has an inner peripheral edge 30 which delimits a central opening and on which the first annular filter portion 24 is engaged, and an outer peripheral edge 32 on which the second annular filter portion 26 is engaged.

[0052] The annular insert 28 has an intermediate annular portion, at a distance from the inner peripheral edge 30 and the outer peripheral edge 32, which forms a clear central portion 34, which is not covered by either the first filtering annular portion 24 or the second filtering annular portion 26.

[0053] The distal portion of the annular insert 28, that is to say the portion furthest from the elongation axis A of the damper, is the portion embedded in the second filtering annular portion 26 and it extends radially over a greater distance than a proximal portion of the annular insert corresponding to the portion of this annular insert 28 which is embedded in the first filtering annular portion 24. This allows, as illustrated in [Fig.2] and as explained below, to be axially overlapping of the contact area of ​​the last coil of the helical spring with the upper cup 18, against which the second filtering annular portion 26 is also in support.

[0054] In the illustrated example, without limiting the invention, this proximal portion of the annular insert, embedded in the first filtering annular portion 24, is substantially of the same radial dimension as the radial dimension of the central exposed portion 34, not covered by one of the filtering annular portions 24, 26.

[0055] Furthermore, the filter block 20 includes a tubular insert 36 which is only linked to the first annular filter portion 24.

[0056] Regardless of the orientation of the extension axis of the shock absorber rod 6 relative to the road on which the vehicle rests, the annular insert 28 extends primarily in a plane perpendicular to the extension axis A of the shock absorber, while the tubular insert 36 extends parallel to this extension axis. In the following description, reference will be made to a vertical orientation of the tubular insert 36 and a horizontal orientation of the annular insert 28, resulting from an arbitrary vertical orientation of the extension axis A of the shock absorber.

[0057] The first annular filter portion 24 is a central portion of the filter block 20 with an opening 38 through which the free end 10 of the damper rod 6 passes. This opening is delimited by a first surface of the tubular insert 36. The second surface, opposite the first surface, of the tubular insert 36 is connected to an internal border 40, referenced in [Fig. 3], of the first annular filter portion 24. At the opposite radial end, the first annular filter portion 24 has an external border 42, also referenced in [Fig. 3], which is engaged around a radial end of the annular insert 28, namely its internal peripheral edge.

[0058] The first annular filter portion 24 is substantially flat, insofar as it has two axial end faces, respectively perpendicular to the internal 40 and external 42 edges, which are flat. A first end face axial 44, visible on [Fig.3], is flat and a second axial end face 46, referenced on [Fig.2], is substantially parallel to this first axial end face, the distance between the two faces, defining the height of the first filtering annular portion 24, being constant.

[0059] The tubular insert 36 is engaged in the material of the first annular filter portion 24, in the vicinity of the inner edge 40. More particularly, the first annular filter portion 24 is overmolded on the tubular insert 36.

[0060] As can be seen in [Fig.2], due to the presence of two inserts associated with the first annular filter portion 24, a peripheral portion can be distinguished within it, which is engaged around the annular insert 28, and a central portion 25, which is interposed between the tubular insert 36 and the inner peripheral edge 30 of the annular insert 28. As will be detailed below, this central portion 25 is able to be constrained radially between the tubular insert 36 and the annular insert 28.

[0061] As mentioned, the tubular insert 36 extends axially, that is, substantially parallel to the elongation axis A of the shock absorber. The tubular insert 36 has an axial dimension greater than the corresponding height of the first annular filter portion 24, such that it extends axially beyond both sides of the first annular filter portion 24. [Fig. 3] notably shows that the tubular insert 36 extends axially beyond the first axial end face 44. As shown in [Fig. 2], the tubular insert 36 is supported at one axial end against the second face of the spring cup, or upper cup 18, and at a second axial end against the rebound cup 22.

[0062] We will now describe the second annular filter portion 26 of the filter block 20 which, as previously mentioned, is separated from the first annular filter portion 24, with the annular insert 28 which is interposed radially between these two annular filter portions.

[0063] The second annular filter portion 26 is axially clamped between the structural element 12 and the spring cup, or upper cup 18.

[0064] The second annular filter portion 26 comprises a substantially flat base 48, within which the annular insert 28 is embedded, and a damping pad 50 which protrudes from the base 48, towards the upper cup 18.

[0065] The base 48 has a shape substantially similar to that of the first filtering annular portion 24, with an axial end upper face 52 of the second filtering annular portion 26, formed by the base 48 and intended to be in contact with the structural element 12, which is substantially flat, as seen in the figures and referenced in [Fig.3].

[0066] The damping pad 50 extends outward from the base 48 to define a restricted contact surface with the spring cup, or upper cup 18. The damping pad 50 has a roughly frustoconical shape, with a cross-section, in a plane perpendicular to the elongation axis, that tends to decrease as it approaches the contact surface with the upper cup 18. Providing a reduced contact surface ensures primarily axial force transmission. To further enhance the transmission of these axial forces, it is also worth noting that the damping pad 50 has a larger axial dimension than its radial dimension.

[0067] This is particularly interesting in the context of the invention where we seek to decouple the two annular filtering portions 24, 26 so that one can support the axial stresses due to the weight of the vehicle and the other is able to dampen and filter the solid vibrations rising towards the body via the strut.

[0068] More specifically, the second annular filter portion 26 is configured to essentially support the axial stresses due to the weight of the vehicle and the first annular filter portion 24 is configured to only filter vibrations.

[0069] The portion of the annular insert 28 embedded in the second annular filter portion 26 extends axially, overlapping the damping pad 50 of this second annular filter portion 26, which is in contact with the spring cup, or upper cup 18. In other words, if a line is drawn parallel to the axis of the damper rod 6 and passing through a point of contact between this damping pad 50 and the upper cup 18, this line intersects the annular insert 28. In this way, the annular insert 28 forms a wall to compress the second annular filter portion 26 under axial, in this case vertical, forces. The second annular filter portion 26 is thus configured to absorb shocks and filter a portion of the vibrations with an axial, or vertical, component.

[0070] Vibrations with a radial component are more particularly absorbed by the first annular filter portion 24, due to the presence of the central portion 25 of this first annular filter portion 24 which is arranged between the inner peripheral edge 30 of the annular insert 28 and the tubular insert 36. Under transverse forces, this area of ​​material forming the central portion 25 is crushed between the two inserts, which causes the material of the first annular filter portion 24 to saturate and which therefore allows the filtration of these radial, or transverse, forces.

[0071] The material of the first annular filter portion 24, like that of the second annular filter portion 26, may in particular be rubber. As illustrated in Figures 2 and 3, with a schematic representation of the material with different point densities, the two annular filter portions may respectively be made of rubber with different stiffnesses. In particular, the second The filtering annular portion 26 may advantageously have a stiffness value greater than the stiffness value of the first filtering annular portion 24, the axial forces to be absorbed being greater than the transverse forces.

[0072] Each of the inserts 28, 36 can be made of a metallic material of its own, or be made of a composite or plastic material.

[0073] It follows from the above, and as shown schematically on [Fig.2] with arrows, that the first annular filter portion 24 supports a large part of the transverse forces T without supporting any of the vertical forces, while the second annular filter portion 26 supports all of the vertical forces V and a very small part of the transverse forces T'.

[0074] It is noteworthy that in the filter block according to the invention, the vertical forces are essentially absorbed by the second annular filter portion 26, due to the absence of axial contact between the latter and the spring cup, or upper cup 18, and the radial separation of the two annular filter portions. Thus, the first annular filter portion 24 is solely dedicated to absorbing transverse forces and is therefore not pre-stressed by the weight of the vehicle during vehicle movement, so that it retains its flexibility for handling the structural vibrations transmitted up to the free end rod of the shock absorber.

[0075] The strut just described is more particularly used in a rear axle of a motor vehicle, that is to say, a non-steering axle, with a decoupled filter block as described above. It could be envisaged to apply a strut, with a decoupled filter block equivalent to that just described, to a steering axle of a motor vehicle, and in particular a front axle, in which the strut is connected to the body by means of a rotating ring interposed between the upper cup and the body, provided that this rotating ring is configured to cooperate with a filter block with decoupled portions according to the invention, with a zone that essentially absorbs axial forces and a zone that absorbs radial forces without having to absorb these axial forces.

[0076] The invention, as described above, achieves its objectives and provides a filter block for a motor vehicle strut capable of separating the rubber portion that supports the vehicle and through which the vertical force of the springs is transmitted from the rubber portion that filters the radial spring forces. Variations not described here could be implemented without departing from the scope of the invention, provided that, in accordance with the invention, they comprise a filter block with two annular portions decoupled by the presence of an insert between them.

Claims

Demands

1. Strut (1) of a motor vehicle suspension system comprising at least one shock absorber (2) and a helical spring (14) arranged around the shock absorber (2), said shock absorber comprising a cylinder (4) and a rod (6) mounted telescopically in this cylinder and whose free end (10) cooperates with a filter block (20) according to any one of the preceding claims, said filter block (20) being interposed between a spring cup (18) of the strut (1) in contact with a coil of the helical spring (14) and a structural element (12) of the vehicle. said filter block (20) being configured to support and filter types of stresses with axial and radial components, said filter block (20) comprising a first annular filter portion (24) which forms a central portion of the filter block and a second distinct annular filter portion (26) which forms an external portion of the filter block,said annular filter portions (24, 26) being radially separated from each other by an annular insert (28) interposed between them, to allow the annular filter portions to respectively primarily handle one of the types of stresses, the free end (10) of the rod (6) extending beyond the filter block (20) to cooperate with a nut (21) to allow a rebound cup (22) to be clamped and thus to link the shock absorber rod (6) to the vehicle structure, said filter block comprising a tubular insert (36), bonded to the material of the first annular filter portion (24) in the vicinity of an internal border (40) of this first annular filter portion (24), the tubular insert (36) being at a first axial end bearing against the spring cup (18), and at a second axial end bearing against the rebound cup (22).

2. Strut (1) according to claim 1, characterized in that the annular insert (28) comprises a flat annular ring which has an inner peripheral edge (30) on which the first filtering annular portion (24) is engaged and an outer peripheral edge (32) on which the second filtering annular portion (26) is engaged, the annular insert (28) having a clear portion (34), which is not covered by either the first filtering annular portion (24) or the second filtering annular portion (26).

3. Strut (1) according to claim 1 or 2, characterized in that the filtering annular portions (24, 26) are overmolded onto the annular insert (28).

4. Strut (1) according to any one of claims 1 to 3, characterized in that the annular insert (28) is made of metallic, composite or plastic material.

5. Strut (1) according to any one of claims 1 to 4, characterized in that the first filtering annular portion (24) and / or the second filtering annular portion (26) are made of rubber.

6. Strut (1) according to any one of claims 1 to 5, characterized in that the two filtering annular portions (24, 26) have different stiffness characteristics from each other.

7. Strut (1) according to the preceding claim, characterized in that the second filtering annular portion (26) has a stiffness value greater than the stiffness value of the first filtering annular portion (24).

8. Strut (1) according to any one of claims 1 to 7, characterized in that the second annular filtering portion (26) has a substantially flat axial end upper face (52) and an axial end lower face equipped with a damping pad (50).

9. Strut (1) according to the preceding claim, characterized in that the damping pad (50) has a substantially frustoconical shape, with a cross-section, in a plane parallel to the plane of the upper axial end face (52) of the second annular filter portion (26), which tends to decrease as one moves away from this upper axial end face (52).

10. Strut (1) according to any one of the preceding claims, characterized in that the filter block (20) is supported on the spring cup (18) receiving the helical spring (14), only by means of the second annular filter portion (26).

11. A strut (1) according to any one of the preceding claims, characterized in that the second annular filter portion (26) comprises a substantially flat base (48) in which the annular insert (28) is embedded, and a damping pad (50) projecting from the base 48 towards the upper cup (18), the pad damping (50) extending outward from the base (48) to define a contact surface with the spring cup (18).

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