Tri-tube hydraulic shock absorber, particularly for vehicle suspension

Abstract

An hydraulic shock absorber with variable damping (10) comprises an inner cylindrical tube (16) and an outer cylindrical tube (18), delimiting a reservoir chamber (20) containing oil; a piston (22), which slidably separates the inner volume of the inner cylindrical tube (16) into a rebound chamber (24) and a compression chamber (26), both containing oil; a first intermediate cylindrical tube (36), arranged around the inner cylindrical tube (16), which, together with the latter, delimits a first intermediate chamber (38) in fluid communication with the compression chamber (26) and the rebound chamber (24); an electronically controlled valve (42), adapted to provide fluid communication between the first intermediate chamber (38) and the reservoir chamber (20); and a shutter (44), slidably housed within the first intermediate chamber (38) and configured to alternately prevent the fluid connection between the first intermediate chamber (38) and the compression chamber (26) and rebound chamber (24), respectively.

Description

[0001] Tri-tube hydraulic shock absorber, particularly for vehicle suspension

[0002] This invention relates to a hydraulic shock absorber with variable damping, designed primarily for use in a vehicle suspension, as specified in the preamble of independent claim 1.

[0003] Variable damping hydraulic shock absorbers are known, incorporating one or two electronically controlled valves, for instance configured as solenoid valves. In configurations with a single valve, it will be designed to adjust the flow of damping fluid (typically oil) during both the compression and rebound phases of the shock absorber. When equipped with a pair of valves, a first valve will be configured to adjust the damping fluid flow of the shock absorber during the compression phase only, while the other valve will be configured to adjust the damping fluid flow during the rebound phase only. This dual-valve setup offers a broader adjustment range compared to single-valve configurations.

[0004] A single-valve shock absorber, as described, is known, for example, from document WO 2020 021500 Al, whereas a dual-valve shock absorber is known in DE 102005 053 394 Al.

[0005] In these known configurations, the shock absorber comprises an outer cylindrical tube, an inner cylindrical tube coaxial to the outer cylindrical tube and defining therewith a reservoir chamber, a rod arranged coaxially with the two cylindrical tubes and partially protruding therefrom, and a piston slidably mounted within the inner cylindrical tube and fixed to the lower end of the rod. The piston separates the inner volume of the inner cylindrical tube into a rebound chamber and a compression chamber, both containing the damping fluid. The piston is provided with a first valve assembly, comprising a pair of one-way valves and precisely a compensation valve, which adjusts the damping fluid flow from the compression chamber to the rebound chamber during the shock absorber compression phase, and a rebound valve, which adjust the damping fluid flow from the rebound chamber to the compression chamber during the shock absorber rebound phase. A second valve assembly, comprising a pair of one-way valves, is mounted at the bottom of the inner cylindrical tube, and precisely a compression valve adjusting the damping fluid flow from the compression chamber to the reservoir chamber during the compression phase, and an intake valve adjusting the damping fluid flow from the reservoir chamber to the compression chamber during the rebound phase. The one-way valve of the first valve group and the second valve group are featured as passive valves.

[0006] A shock absorber known from DE 10 2005 053 394 Al additionally comprises a first and second electronically controlled valve designed to adjust the damping fluid flow during the rebound and compression phases, respectively. More specifically, the first electronically controlled valve is connected on one side to the reservoir chamber and on the other side to a first intermediate chamber defined between the inner cylindrical tube and a first intermediate cylindrical tube radially interposed between the inner cylindrical tube and the outer cylindrical tube, said first intermediate chamber being permanently in fluid communication with the rebound chamber. The first electronically controlled valve is configured to adjust the damping fluid flow from the rebound chamber to the reservoir chamber through the first intermediate chamber during the rebound phase, and thus adjusting the damping force of shock absorber during this phase. The second electronically controlled valve is connected on one side to the reservoir chamber and on the other side to a second intermediate chamber defined between the inner cylindrical tube and a second intermediate cylindrical tube radially interposed between the inner cylindrical tube and the outer cylindrical tube, said second intermediate chamber being permanently in fluid communication with the compression chamber. The second electronically controlled valve is configured to adjust the damping fluid flow from the compression chamber to the reservoir chamber through the second intermediate chamber during the compression phase and thus adjust the damping force of the shock absorber in this phase.

[0007] The valve bodies of both electronically controlled valves in this known shock absorber are mounted externally to the outer cylindrical tube. Therefore, compared to hydraulic shock absorbers with variable damping which have a single electronically controlled valve, the shock absorber known from DE 10 2005 053 394 Al has a larger footprint, thus making it more challenging to install on a vehicle, in particular in limited-space applications.

[0008] Conversely, the use of two electronically controlled valves, instead of one, allows the rebound phase and the compression phase of the shock absorber to be controlled independently from each other, provides greater adjustment flexibility, especially during the compression phase, and improves control of “high”-frequencies typical of vehicle wheels (around 15 Hz), as the shock absorber response is very rapid due to each electronically controlled valve being preset before the beginning of its respective phase (rebound or compression).

[0009] The object of this invention is to provide a hydraulic shock absorber with variable damping that, while retaining the above illustrated advantages associated with the use of two electronically controlled valves, operates with a single valve, offering benefits in terms of space requirements and manufacturing simplicity.

[0010] This and other objects are achieved, according to the present invention, due to a hydraulic shock absorber with variable damping featuring the characteristics defined in the annexed independent claim 1.

[0011] Advantageous embodiments of the invention are specified in the dependent claims, the content of which is to be considered an integral part of the following description.

[0012] In summary, the invention is based on the concept of providing the hydraulic shock absorber with an electronically controlled valve configured to control the damping fluid flow during both the rebound and compression phases, wherein said electronically controlled valve is arranged outside the shock absorber body and is connected on one side to the reservoir chamber and on the other side to a first intermediate chamber defined between the inner cylindrical tube and a first intermediate cylindrical tube radially interposed between the inner cylindrical tube and the outer cylindrical tube.

[0013] The first intermediate chamber is configured to be in fluid communication with both the compression and rebound chambers (and / or possibly the reservoir chamber).

[0014] Inside the first intermediate chamber, a shutter is slidably housed, configured to alternately inhibit the fluid connection between the first intermediate chamber and the compression and rebound chambers, respectively, when the shock absorber is in rebound or in compression.

[0015] In particular, the shock absorber is preferably configured such that, during the rebound, the shutter inhibits the hydraulic connection between the first intermediate chamber and the compression chamber, allowing to adjust the flow of the rebound phase only. In the compression phase, the shutter inhibits instead the hydraulic connection between the first intermediate chamber and the rebound chamber, allowing to adjust the flow of the compression phase only.

[0016] Thanks to such a configuration, the hydraulic shock absorber according to the invention retains the advantages described above with reference to the known art, associated with the use of two electronically controlled valves to manage the damping fluid flow during the compression and rebound phases, and has a reduced size compared to the known art, since only one electronically controlled valve is positioned outside the shock absorber body.

[0017] Further features and advantages of the present invention will become clearer when reading the following detailed description, provided purely by way of a non-limiting example with reference to the accompanying drawings, wherein:

[0018] - figure 1 shows a schematic axial sectional view of a hydraulic shock absorber with variable damping in a neutral condition, according to one embodiment of the present invention;

[0019] - figure 2 shows a schematic axial sectional view of the hydraulic shock absorber in figure 1 during the compression phase; and

[0020] - figure 3 shows a schematic axial sectional view of the hydraulic shock absorber in figure 1 during the rebound phase.

[0021] Detailed description

[0022] Before explaining a plurality of embodiments of the invention in detail, it should be clarified that the invention is not limited in its application to the specific construction details and configuration of the components described in the following description or illustrated in the drawings. The invention can assume other embodiments and can be practically implemented or applied in various ways. It should also be understood that the phraseology and terminology used herein are for descriptive purposes and should not be construed as limiting. With reference to Figure 1, a hydraulic shock absorber with variable damping (hereinafter referred to simply as shock absorber), particularly intended for being used in a vehicle suspension, is generally denoted by 10.

[0023] The shock absorber 10 comprises a cylindrical body 12 (hereinafter referred to simply as body) extending along a longitudinal axis x and a rod 14 that partially protrudes (upwards, according to the observer's point of view in the figure) from the body 12 and is axially movable (i.e. along the direction of the longitudinal axis x) with respect to the body 12.

[0024] The body 12 comprises an inner cylindrical tube 16 and an outer cylindrical tube 18, which are arranged coaxially with respect to each other and delimit a reservoir chamber 20 containing a damping fluid (typically oil, which will henceforth be referred to simply as "oil" for simplicity).

[0025] A piston 22 is slidably mounted within the inner cylindrical tube 16 and is fixed to the lower end of the rod 14. The piston 22 divides the inner volume of the inner cylindrical tube 16 into a rebound chamber 24 and a compression chamber 26, both containing the working fluid (preferably oil).

[0026] The piston 22 can be equipped with a first valve assembly, comprising a pair of one-way valves, and specifically, a compensation valve, which allows oil to flow exclusively from the compression chamber 26 to the rebound chamber 24, and a rebound valve, which only allows oil flow from the rebound chamber 24 to the compression chamber 26.

[0027] At the bottom of the inner cylindrical tube 16, a second valve assembly comprising a pair of one-way valves may be mounted, , and precisely, a compression valve, which allows the oil to flow only from the compression chamber 26 to the reservoir chamber 20, and an intake valve, which only allows the oil to flow from the reservoir chamber 20 to the compression chamber 26.

[0028] The one-way valves in the first valve assembly, as well as the one-way valves in the second valve assembly, are preferably implemented as passive valves. Around the inner cylindrical tube 16, coaxial with it, there is also arranged a first intermediate cylindrical tube 36, which, together with the inner cylindrical tube 16, delimits a first intermediate chamber 38. The first intermediate chamber 38 is in fluid communication with the compression chamber 26 and the rebound chamber 24 (and possibly with the reservoir chamber 20).

[0029] The shock absorber 10 also comprises an electronically controlled valve 42, hereinafter referred to simply as electronic valve.

[0030] The electronic valve 42 is preferably implemented as a two-way solenoid valve and fundamentally comprises, in a per se known manner, a valve body (in which the aforementioned two ways are defined), a shutter (movable with respect to the valve body and capable of selectively occluding one and / or the other way), and a solenoid, electrically powered and configured to control the displacement of the shutter to adjust the flow of oil from one way to the other of the valve.

[0031] However, other implementations of the electronic valve 42 are possible, such as solutions where the valve is of a pilot-operated or bi-stable type. It is clear that this invention is not limited to the use of a particular type of electronic valve.

[0032] The electronic valve 42 may be of a proportional type with continuous control or of an ON / OFF type.

[0033] The electronic valve 42 is arranged outside the body 12 of the shock absorber. More specifically, the electronic valve 42 is arranged outside the outer cylindrical tube 18, by which it can be properly supported.

[0034] The electronic valve 42 is configured to provide fluid communication between the first intermediate chamber 38 and the reservoir chamber 20, and to control the flow of oil from one to the other, preferably operating in parallel with respect to the one-way valves of the second valve assembly, which may be positioned at the bottom of the inner cylindrical tube 16. For this purpose, the electronic valve 42 is connected with its first way to the first intermediate chamber 38 (and, through it, to the compression chamber 26 and rebound chamber 24) and with its second way to the reservoir chamber 20.

[0035] In the first intermediate chamber 38, a shutter 44 is slidably housed, configured to alternately inhibit the fluid connection between the first intermediate chamber 38 and the compression chamber 26 and the rebound chamber 24. In this way, it is possible to selectively inhibit or allow the passage of the fluid between the fluid connection way of the electronic valve 42 with the first intermediate chamber 38, and the compression chamber 26 and rebound chamber 24 (and / or possibly the reservoir chamber 20, according to an embodiment wherein the first intermediate chamber 38 is also in fluid communication with the reservoir chamber 20, independently of the electronic valve 42, as in the illustrated example).

[0036] In particular, the shutter 44 may be configured to alternately prevent the fluid connection between the first intermediate chamber 38 and the compression and rebound chambers 26 and 24 (and / or possibly the reservoir chamber 20, even when the electronic valve 42 is closed), respectively, when the shock absorber 10 is in extension or compression, or respectively when the pressure exerted on the shutter 44 by the fluid from the rebound chamber 24 is greater than the pressure exerted on the shutter 44 by the fluid from the compression chamber 26, and when the pressure exerted on the shutter 44 by the fluid from the compression chamber 26 exceeds the pressure exerted on the shutter 44 by the fluid from the rebound chamber 24 (and / or possibly from the reservoir chamber 20). The shutter 44 is also configured so that, when a predetermined pressure threshold exerted by the fluid from the rebound chamber 24 (and / or possibly from the reservoir chamber 20), or exerted by the fluid from the compression chamber 26, is exceeded, the shutter 44 allows at least partial fluid communication between the first intermediate chamber 38 and the electronic valve 42.

[0037] The first intermediate chamber 38 is preferably configured such that the shutter 44 can move pushed under the pressure of fluid entering alternately from the compression and rebound chambers 26 and 24 (and / or possibly from the reservoir chamber 20) between:

[0038] - a first configuration, wherein the shutter 44 occludes the connection to the first intermediate chamber 38 from the rebound chamber 24 (and / or possibly from the reservoir chamber 20), leaving free the connection to the first intermediate chamber 38 from the compression chamber 26 (when the shock absorber 10 is in compression phase); and

[0039] - a second configuration, wherein the shutter 44 occludes the connection to the first intermediate chamber 38 from the compression chamber 26, leaving free the connection to the first intermediate chamber 38 from the rebound chamber 24 and / or possibly from the reservoir chamber 20 (when the shock absorber 10 is in extension phase).

[0040] Suitably, the first intermediate chamber 38 can be configured so that, at the fluidic connection inlets to the compression chamber 26 and rebound chamber 24 (and / or possibly to the reservoir chamber 20), said first intermediate chamber 38 has respective restricted sections, against which the shutter 44 can abut, selectively preventing the passages of fluid to and from the first intermediate chamber 38 through said inlets.

[0041] In a preferred embodiment, the shutter 44 comprises an annular element 46, such as a bushing or sleeve (made of plastic or metal), housed axially slidable within the first intermediate chamber 38.

[0042] Even more preferably, the shutter 44 comprises a pair of annular elements 46, for instance in the form of metallic sleeves, slidably housed within the first intermediate chamber 38 and separated by an elastic element 48 (such as a helical spring), configured to push the annular elements 46 toward the opposite ends of the first intermediate chamber 38. In such a configuration, the shutter 44 can inhibit the fluid connection between the first intermediate chamber 38 and the compression and rebound chambers 26 and 24 simultaneously, for instance when the pressure exerted on the shutter 44 by the fluid from the rebound chamber 24 (and / or possibly the reservoir chamber 20) is equal to the pressure exerted on the shutter 44 by the fluid from the compression chamber 26 (which may occur in a static or rest condition of the shock absorber). In this manner, when the pressure exerted on the shutter 44 by the fluid from the rebound chamber 24 (and / or possibly the reservoir chamber 20) is equal to the pressure exerted on the shutter 44 by the fluid from the compression chamber 26, and / or these pressures are insufficient to compress the elastic element 48, the shutter 44 would assume a configuration in which the passage of fluid to the first intermediate chamber 38 from the compression and rebound chambers 26 and 24 (and / or possibly from the reservoir chamber 20) is prevented, which would constitute an additional condition to the aforementioned first and second configurations of the shutter 44; when the shock absorber 10 is in extension or compression, one of the annular elements 46 of the shutter 44 remains abutted against one end of the first intermediate chamber 38 (i.e. the end proximal to the rebound chamber 24, when the shock absorber 10 is in compression, or the end distal from the rebound chamber 24 when the shock absorber 10 is in extension), occluding its corresponding outlet to the outside, while the second annular element 46 is compressed toward the first against the force of the elastic element 48.

[0043] The shutter 44 is preferably configured such that, as the pressure exerted by the fluid from the rebound chamber 24 (and / or possibly the reservoir chamber 20) or by the fluid from the compression chamber 26 increases, one of the annular elements 46 is slidable axially to allow at least partial fluid communication between the first intermediate chamber 38 and the electronic valve 42. Preferably, as exemplified in Figures 2 and 3, the shutter 44 is configured such that, in a fully compressed condition of the elastic element 48, both annular elements 46 are positioned on the same side of the first intermediate chamber 38 relative to the axis of the electronic valve 42, thereby avoiding occlusion of the fluid connection path between the electronic valve 42 and the first intermediate chamber 38.

[0044] According to one embodiment, the first intermediate cylindrical tube 36 extends axially to at least partially encompass the inner cylindrical tube 16, thus delimiting, together with the latter, a second intermediate chamber 40 in fluid communication with the rebound chamber 24 (and / or possibly the reservoir chamber 20). This second intermediate chamber 40 being placed in fluid communication with the first intermediate chamber 38.

[0045] According to an alternative embodiment, as exemplified in the figures, the shock absorber 10 comprises a second intermediate cylindrical tube 39, axially coupled to the first intermediate cylindrical tube 36 and arranged around the inner cylindrical tube 16, coaxially with it, thus delimiting, together with the inner cylindrical tube 16, a second intermediate chamber 40, in fluid communication with the rebound chamber 24 (and / or possibly the reservoir chamber 20), said second intermediate chamber 40 being susceptible to be placed in fluid communication with the first intermediate chamber 38. Between the first and second intermediate chambers 36,40, a one-way valve 41 may be arranged, configured, for example, as a deformable gasket or a wave spring associated with a disk, designed to allow the passage of fluid from the second intermediate chamber 40 to the first intermediate chamber 38 in a first configuration. According to one embodiment, the one-way valve 41 can be configured such that, in the position where the passage of fluid from the first intermediate chamber 38 to the second intermediate chamber 40 is inhibited, the passage of fluid from the first intermediate chamber 38 to the reservoir chamber 20, or vice versa, is allowed.

[0046] Conveniently, the first intermediate chamber 38 can be fluidly connected to the compression chamber 26 via one or more first holes 37.

[0047] Conveniently, the second intermediate chamber 40 can be fluidly connected to the rebound chamber 24 via one or more second holes 43.

[0048] The operation of the shock absorber 10, according to one embodiment of the invention, is as follows.

[0049] In a neutral condition, the shutter 44 may optionally occlude all fluid connections among the first intermediate chamber 38, the compression chamber 26, the rebound chamber 24 (and / or possibly the reservoir chamber 20). In this condition, for instance, the annular elements 46 of the shutter 44 are maximally spaced apart by the elastic element 48, and abut against the ends of the first intermediate chamber 38, the electronic valve 42 is fluidly isolated from the compression chamber 26 and the rebound chamber 24.

[0050] During the compression phase of the shock absorber 10, as illustrated in Figure 2, an oil flow occurs from the compression chamber 26 to the first intermediate chamber 38 and from the latter — through the electronic valve 42 — to the reservoir chamber 20, as the shutter 44, under the pressure differential on both ends of the shutter 44, slides axially along the first intermediate chamber 38, establishing fluid communication between the latter and the one way of the electronic valve 42. By appropriately controlling the electronic valve 42, it is thus possible to adjust the oil flow from the compression chamber 26 to the reservoir chamber 20 through the first intermediate chamber 38, and thereby control the damping force exerted on the rod 14 during the compression phase.

[0051] During the rebound (extension) phase of the shock absorber 10, as illustrated in Figure 3, an oil flow occurs from the rebound chamber 24 to the first intermediate chamber 38 (preferably through the second intermediate chamber 40), and from the first intermediate chamber 38 — through the electronic valve 42 — to the reservoir chamber 20 as the shutter 44, under the pressure differential on both ends of the shutter 44, slides axially along the first intermediate chamber 38 (in the opposite direction to compression phase), until establishing fluid communication with one way of the electronic valve 42.

[0052] By appropriately controlling the electronic valve 42, it is thus possible to adjust the oil flow from the rebound chamber 26 to the reservoir chamber 20 and thus adjust the damping force exerted on the rod 14 during the extension phase.

[0053] The advantages achievable by a hydraulic shock absorber with variable damping according to the present invention are made clear in the description provided above.

[0054] Firstly, owing to the shutter that adjusts the oil flow to the electronic valve, the shock absorber according to the invention allows the rebound phase and the compression phase of the shock absorber to be controlled independently from each other as if two electronic valves were used.

[0055] Furthermore, compared to the known art discussed above, a shock absorber according to the present invention has a smaller external footprint since it uses only one electronic valve.

[0056] Finally, a further advantage over the known art is that, with comparable adjustment performance to a solution equipped with two electronic valves, there is a reduction in unsprung masses (i.e. the mass that moves together with the vehicle wheels), as only one electronic valve is mounted on the shock absorber body. A reduction in unsprung masses, as is known, to improve the vehicle dynamic behaviour.

[0057] Of course, without departing from the principle of the invention, the embodiments and spe- cific details of construction be varied with respect to what has been described and illustrated purely as a non-limiting example, without departing from the scope of the invention as defined in the annexed claims.

Claims

CLAIMS1. Hydraulic shock absorber with variable damping ((10)), in particular for being used in a vehicle suspension, comprising:- a cylindrical body (12), extending along a longitudinal axis (x), and a rod (14) which partially protrudes from the body (12) and is movable axially with respect to the cylindrical body (12), which cylindrical body (12) comprises an inner cylindrical tube (16) and an outer cylindrical tube (18), which are arranged coaxially with respect to each other and delimit a reservoir chamber (20) containing a damping fluid;- a piston (22), slidably mounted in the inner cylindrical tube (16) and fixed to the lower end of the piston rod (14), said piston (22) being configured to separate the inner volume of the inner cylindrical tube (16) into a rebound chamber (24) and a compression chamber (26), both containing the damping fluid;- a first intermediate cylindrical tube (36), arranged around the inner cylindrical tube (16) coaxially to the latter, said first intermediate cylindrical tube (36) delimiting together with the inner cylindrical tube (16) a first intermediate chamber (38), in fluid communication with the compression chamber (26) and the rebound chamber (24); and- an electronically controlled valve (42), arranged outside the outer cylindrical tube (18) and configured to bring the first intermediate chamber (38) in fluid communication with the reservoir chamber (20), and control the flow of damping fluid from one to the other; characterised in that in the first intermediate chamber (38) a shutter (44) is slidably accommodated, configured to alternately inhibit the fluid connection between the first intermediate chamber (38) and the compression chamber (26) and rebound chamber (24), respectively.

2. Shock absorber according to claim 1, wherein the shutter (44) is configured to alternately inhibit the fluid connection between the first intermediate chamber (38) and the compression (26) and re-bound (24) chambers, respectively when the shock absorber (10) is in extension or compression, said shutter (44) being configured in such a way that, when a predetermined threshold pressure exerted by the fluid coming from the rebound chamber (24), or exerted by the fluid coming from the compression chamber (26) is exceeded, at least a partial fluid connection is allowed between the first intermediate chamber (38) and theelectronically controlled valve (42).

3. Shock absorber according to claim 1 or 2, wherein the first intermediate chamber (38) is also in fluid communication with the reservoir chamber (20), independently of the electronically controlled valve (42).

4. Shock absorber according to claim 3, wherein the shutter (44) is configured to alternately inhibit the fluid connection between the first intermediate chamber (38) and the compression chambers (26) and rebound chamber (24) and / or the reservoir chamber (20), respectively when the shock absorber (10) is in extension or compression, said shutter (44) being configured such that upon exceeding a predetermined pressure threshold exerted by the fluid coming from the rebound chamber (24) and / or the reservoir chamber (20), or exerted by the fluid coming from the compression chamber (26), at least a partial fluid connection is allowed between the first intermediate chamber (38) and the electronically controlled valve (42).

5. Shock absorber according to any one of the preceding claims, wherein the first intermediate chamber (38) is configured in such a way that the shutter (44) is movable under the pressure of fluid entering alternately from the compression (26) and rebound (24) chambers and / or possibly from the reservoir chamber (20), between:- a first configuration, in which the shutter (44) occludes the connection to the first intermediate chamber (38) from the rebound chamber (24) and / or possibly from the reservoir chamber (20), leaving free the connection to the first intermediate chamber (38) from the compression chamber (26) when the damper (10) is in compression; and- a second configuration, in which the shutter (44) occludes the connection to the first intermediate chamber (38) from the compression chamber (26), leaving free the connection to the first intermediate chamber (38) from the rebound chamber (24) and / or possibly from the reservoir chamber (20), when the shock absorber (10) is in extension.

6. Shock absorber according to any of the preceding claims, wherein the first intermediate chamber (38) is configured such that, at the fluidic connection inlets to the compression (26) and rebound (24) chambers and / or the reservoir chamber (20), said first intermediatechamber (38) has respective restricted sections, against which the shutter (44) is abuttable, so as to selectively prevent fluid passages to and from the first intermediate chamber (38) through said inlets.

7. Shock absorber according to any one of the preceding claims, wherein the shutter (44) comprises an annular element (46), such as a bushing or a sleeve, axially slidably accommodated within the first intermediate chamber (38).

8. Shock absorber according to claim 7, wherein the shutter (44) comprises a pair of annular elements (46) axially slidably received within the first intermediate chamber (38) and separated by an elastic element (48) configured to push the annular elements (46) towards the opposite ends of the first intermediate chamber (38).

9. Shock absorber according to claim 8, wherein the shutter (44) is configured such that, as the pressure exerted by the fluid coming from the rebound chamber (24) and / or possibly from the reservoir chamber (20), or exerted by the fluid coming from the compression chamber (26), increases, one of the annular elements (46) is axially slidable to allow at least a partial fluid connection between the first intermediate chamber (38) and the electronically controlled valve (42).

10. Shock absorber according to claim 9, wherein the shutter (44) is configured such that, in a maximally compressed condition of the elastic element (46), both annular elements (46) are on the same side of the first intermediate chamber (38), relative to the axis of the electronically controlled valve (42), so as to avoid occluding the fluidic connection path between the electronically controlled valve (42) and the first intermediate chamber (38).

11. Shock absorber according to any one of the preceding claims, wherein the first intermediate cylindrical tube (36) extends axially to at least partially embrace the inner cylindrical tube (16), so as to delimit together with the latter a second intermediate chamber (40) in fluid communication with the rebound chamber (24) and / or the reservoir chamber (20), said second intermediate chamber (40) being adapted to be brought in fluid communication with the first intermediate chamber (38).

12. Shock absorber according to any one of claims 1 to 10, wherein the shock absorber (10) comprises a second intermediate cylindrical tube (39), axially coupled to the first intermediate cylindrical tube (36) and arranged around the inner cylindrical tube (16), coaxially therewith, delimiting together with the inner cylindrical tube (16) a second intermediate chamber (40), in permanent fluid communication with the rebound chamber (24) and / or the reservoir chamber (20), said second intermediate chamber (40) being adapted to be brought in fluid connection with the first intermediate chamber (38).

13. Shock absorber according to claim 11 or 12, wherein a one-way valve (41) is arranged between the first and second intermediate chambers (36), (40), for allowing or inhibiting a passage of fluid from the second intermediate chamber (40) to the first intermediate chamber (38) in a first configuration.

14. Shock absorber according to any one of the preceding claims, wherein the first intermediate chamber (38) is fluidly connected to the compression chamber (26) via one or more first holes (37).

15. Shock absorber according to any one of claims 11 to 14, wherein the second intermediate chamber (40) is fluidly connected to the rebound chamber (24) via one or more second holes (43).

16. Shock absorber according to any one of the preceding claims, wherein the electronically controlled valve (42) is connected with a first way thereof to the first intermediate chamber (38), and with a second way thereof to the reservoir chamber (20), so as to selectively inhibit or allow the passage of fluid between the fluidic connection way of the electronically controlled valve (42) with the first intermediate chamber (38), and the compression (26) and rebound (24) chambers.

17. Shock absorber according to claim 16, wherein the electronically controlled valve (42) is configured as a two-way solenoid valve and comprises a valve body in which said two ways are defined, a plug movable with respect to the valve body and capable ofselectively occluding one or both ways, and a solenoid, electrically powered and capable of controlling the displacement of the plug to regulate the oil flow from one way to the other of the electronically controlled valve (42).

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