Hydraulic shock absorber for vehicle suspension with hydraulic end stop members operating during the compression stroke

Abstract

The hydraulic shock absorber 10 includes a first cylindrical tube 14, a piston rod 18 disposed coaxially relative to the first cylindrical tube 14 and projecting from an upper side of the first cylindrical tube 14, a main piston 20 attached to the piston rod 18 and slidably mounted within the first cylindrical tube 14 to divide the interior volume of the first cylindrical tube 14 into a compression chamber 24 containing a damping fluid and a compression chamber 24 containing a compression fluid, and hydraulic end stop members 36, 38, 58 disposed within the compression chamber 24 and operative to hydraulically dissipate the kinetic energy of the piston rod 18 during the final section of the compression stroke of the shock absorber 10. The hydraulic end stop member 36, 38, 58 comprises a cup-shaped body 36 attached to the piston rod 18 below the main piston 20 and arranged to be open at its bottom, a secondary piston 38 arranged to slide within the cup-shaped body 36 during the final section of the compression stroke of the shock absorber 10 to compress damping fluid contained in a working chamber 52 defined between the cup-shaped body 36 and the secondary piston 38, and a pin 58 attached to the bottom region of the first cylindrical tube 14 and extending coaxially relative to the cup-shaped body 36, the pin 58 associated with the secondary piston 38 to enable the secondary piston 38 to slide within the cup-shaped body 36 during the final section of the compression stroke of the shock absorber 10.

Description

[Technical Field]

[0001] The present invention relates generally to hydraulic shock absorbers for vehicle suspensions, and more particularly to hydraulic shock absorbers having compression-actuated hydraulic end stop members positioned to damp relative motion between a piston rod and the shock absorber body during the final portion of the compression stroke. [Background technology]

[0002] The present invention will be described herein with particular reference to hydraulic shock absorbers for vehicle suspensions of the so-called twin-tube type, but is intended to be applicable to any other type of hydraulic shock absorber for vehicle suspensions.

[0003] A twin-tube hydraulic shock absorber for a vehicle suspension typically includes an outer cylindrical tube, an inner cylindrical tube coaxial with the outer cylindrical tube and defining an annular chamber with the outer cylindrical tube, a piston rod positioned coaxially with the two cylindrical tubes and partially projecting therefrom, and a main piston slidably mounted within the inner cylindrical tube and secured to the lower end of the piston rod. The main piston separates the inner cylindrical tube's internal volume into a rebound chamber and a compression chamber, which contain a damping fluid, typically oil. The main piston includes a first pair of one-way valves: a compensation valve that controls the flow of damping fluid from the compression chamber to the rebound chamber during the shock absorber's compression phase, and a rebound valve that controls the flow of damping fluid from the rebound chamber to the compression chamber during the shock absorber's extension phase. The valve assembly is located at the bottom of the shock absorber and has a second pair of one-way valves, namely, a compression valve which controls the flow of damping fluid from the compression chamber to the annular chamber during the compression phase, and an intake valve which controls the flow of damping fluid from the annular chamber to the compression chamber during the extension phase.

[0004] It is known to provide hydraulic shock absorbers of this type with hydraulic end stop members which are actuated on compression.

[0005] A hydraulic shock absorber for a vehicle suspension with a hydraulic end stop member that operates during compression is described, for example, in WO 2016 / 146660. This document, in particular, discloses a hydraulic shock absorber for a vehicle suspension, in which the hydraulic end stop member has a cup-shaped body coaxially mounted within the shock absorber's compression chamber and a secondary piston coaxially mounted on the shock absorber's piston rod and below the main piston, so that the secondary piston slides within the cup-shaped body during the compression stroke as the shock absorber approaches its end-stroke position. The cup-shaped body has side walls and a bottom wall that, together with the secondary piston, define an operating chamber in which damping fluid is compressed by the secondary piston as it slides within the operating chamber toward the bottom wall of the cup-shaped body. Additionally, an axial groove or channel is provided in the inner surface of the side wall of the cup-shaped body to allow damping fluid to flow axially out of the working chamber as the secondary piston slides within the working chamber toward the bottom wall of the cup-shaped body. In such hydraulic shock absorbers, damping of the shock absorber piston rod movement during the final section of the compression stroke is therefore achieved by damping fluid flowing out of the cup-shaped body of the hydraulic end stop member through the axial channel in the cylindrical side wall of the body.

[0006] This known solution has several drawbacks.

[0007] First, the cup-shaped body must be manufactured with high precision to ensure a perfect fit with the inner surface of the inner cylindrical tube. This, along with the need to provide multiple axial channels on the inner surface of the side wall of the cup-shaped body, which preferably have a cross-section whose area continuously decreases axially toward the bottom wall of the cup-shaped body, makes the cup-shaped body rather complex and expensive to manufacture. Furthermore, calibration of the hydraulic end stop member, i.e., adjusting the damping force acting on the shock absorber's piston rod, requires changing the cross-section of the axial channels in the cup-shaped body and therefore removing and replacing them, operations that are by no means quick or easy to perform. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2016 / 146660 Summary of the Invention

[0009] SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydraulic shock absorber for a vehicle suspension having hydraulic end stop members that operate on compression, thereby overcoming the above-mentioned drawbacks of the prior art.

[0010] This and other objects are fully achieved according to the invention by a hydraulic shock absorber for a vehicle suspension having the features defined in independent claim 1.

[0011] Advantageous embodiments of the invention are defined in the dependent claims, the subject matter of which is intended to form an integral part of the following description. In summary, the invention is based on the idea of ​​providing a hydraulic end stop member which, as in the prior art, also comprises a cup-shaped body and a secondary piston, but unlike the prior art, the cup-shaped body is fixed to the piston rod of the shock absorber, in particular below the main piston, and the secondary piston is configured to slide within the cup-shaped body in the final section of the shock absorber's compression stroke due to relative movement between the cup-shaped body, which is drivingly connected to the shock absorber's piston rod, and a valve assembly at the bottom of the shock absorber. According to the invention, the hydraulic end stop member further comprises a pin attached to the valve assembly at the bottom of the shock absorber and extending coaxially relative to the cup-shaped body, said pin being associated with the secondary piston so that the pin can slide within the cup-shaped body in the final section of the shock absorber's compression stroke. This configuration of the hydraulic end stop member offers the advantage of being easily adaptable to existing hydraulic shock absorbers, since it does not require any special modifications to the existing shock absorber. Indeed, the cup-shaped body can be easily attached to the lower end of the shock absorber's piston rod using the threaded portion typically provided on its end for attaching a nut, and the shock absorber's main piston is attached to the piston rod using the nut. Similarly, the pin can be easily attached to the valve assembly at the bottom of the shock absorber using the threaded pin typically provided for attaching a nut, and the valve assembly is attached to the bottom of the shock absorber using the nut.

[0012] Calibrating the hydraulic end stop members is also very quick and easy, as it is sufficient to remove the shock absorber piston rod, dismantle the attached cup body and replace it with a new one.

[0013] According to one embodiment, the secondary piston is mounted within the cup-shaped body so as to be biased by the elastic means towards a rest position situated at a maximum distance from the bottom wall of the cup-shaped body, and a pin mounted on a valve assembly at the bottom of the shock absorber is configured to penetrate into the cup-shaped body in the final section of the shock absorber's compression stroke, thus biasing the secondary piston along the cup-shaped body towards the bottom wall of the cup-shaped body.

[0014] According to another embodiment, the secondary piston is mounted on the outside of the cup-shaped body, specifically on the end of a pin attached to the valve assembly at the bottom of the shock absorber, so that it penetrates into the cup-shaped body during the final section of the shock absorber compression stroke.

[0015] Further characteristics and advantages of the invention will become apparent from the following detailed description, given purely by way of non-limiting example.

[0016] In the following detailed description of the present invention, reference is made to the accompanying drawings. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram of a hydraulic shock absorber for a vehicle suspension, particularly a hydraulic shock absorber having a twin tube architecture with hydraulic end stop members that operate during compression, according to one embodiment of the present invention. [Figure 2] 2A to 2C are axial cross-sectional views of the hydraulic shock absorber for a vehicle suspension according to the embodiment of FIG. 1 in different operating positions; [Figure 3] 2A to 2C are axial cross-sectional views of the hydraulic shock absorber for a vehicle suspension according to the embodiment of FIG. 1 in different operating positions; [Figure 4] 2A to 2C are axial cross-sectional views of the hydraulic shock absorber for a vehicle suspension according to the embodiment of FIG. 1 in different operating positions; [Figure 5]2 is an axial cross-sectional view on an enlarged scale of the assembly formed by the cup-shaped body of the shock absorber of FIG. 1 and the secondary piston of the hydraulic end stop member; [Figure 6] 2 is an axial cross-sectional view on an enlarged scale of the assembly formed by the pin of the hydraulic end stop member and the bottom valve assembly of the shock absorber of FIG. 1; [Figure 7] 1 is a schematic diagram of a hydraulic shock absorber for a vehicle suspension according to a further embodiment of the present invention, in particular a hydraulic shock absorber having a twin tube architecture with hydraulic end stop members that operate during compression. [Figure 8] 8A to 8C are axial cross-sectional views of the shock absorber for a vehicle according to the embodiment of FIG. 7 in different operating positions. [Figure 9] 8A to 8C are axial cross-sectional views of the shock absorber for a vehicle according to the embodiment of FIG. 7 in different operating positions. [Figure 10] 8A to 8C are axial cross-sectional views of the shock absorber for a vehicle according to the embodiment of FIG. 7 in different operating positions. [Figure 11] 8 is an axial cross-sectional view on an enlarged scale of the cup-shaped body of the hydraulic end stop member of the shock absorber of FIG. [Figure 12] 8 is an axial cross-sectional view on an enlarged scale of the assembly formed by the pin and secondary piston of the hydraulic end stop member and the valve assembly at the bottom of the shock absorber of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] In the following description and claims, the terms "axially" and "axially" identify the direction of the longitudinal axis of the shock absorber and the longitudinal axis of the hydraulic end stop member. Furthermore, the terms "upper" and "lower" are intended to refer to the shock absorber arrangements shown in Figures 1 and 7 with reference to the first and second embodiments of the invention proposed herein, respectively, where the main piston of the shock absorber is attached to the lower end of the piston rod, and therefore the piston rod and main piston move downward during the compression stroke of the shock absorber and move upward during the extension stroke of the shock absorber.

[0019] As noted above, this description of the invention relates to hydraulic shock absorbers having a twin-tube architecture. However, the invention is not intended to be limited to such shock absorber architectures, as it is equally applicable to single-tube hydraulic shock absorbers.

[0020] 1, a twin-tube hydraulic shock absorber for a vehicle suspension is generally designated 10 and comprises, in a manner known per se, an outer cylindrical tube 12, an inner cylindrical tube 14 coaxial with the outer cylindrical tube 12 and defining, together with the outer cylindrical tube 12, an annular chamber 16 at its upper portion which is filled with gas, a piston rod 18 arranged coaxially with the cylindrical tubes 12 and 14 and projecting partially from the upper side of the shock absorber, and a piston 20 (hereinafter referred to as the main piston) slidably mounted within the inner cylindrical tube 14 and fixed to the lower end of the piston rod 18. The longitudinal axis of the shock absorber 10 is designated by z.

[0021] The main piston 20 separates the interior volume of the inner cylindrical tube 14 into an upper chamber 22 or extension chamber and a lower chamber 24 or compression chamber which contains a damping fluid, typically oil.

[0022] The main piston 20 is provided, in a manner known per se, with a valve assembly having a pair of one-way valves, i.e. compensation valves 26, which control the flow of damping fluid from the compression chamber 24 to the rebound chamber 22 during the compression phase of the shock absorber, and a rebound valve 28, which controls the flow of damping fluid from the rebound chamber 22 to the compression chamber 24 during the rebound phase of the shock absorber.

[0023] At the bottom of the shock absorber 10, i.e., at the bottom of the inner cylindrical tube 14, there is provided, in a manner known per se, a valve assembly 30 (hereinafter referred to as the bottom valve assembly) having a pair of one-way valves, namely a rebound valve 32 which controls the flow of damping fluid from the annular chamber 16 to the compression chamber 24 during the extension phase, and a rebound valve 34 which controls the flow of damping fluid from the compression chamber 24 to the annular chamber 16 during the compression phase.

[0024] The shock absorber 10 also includes a hydraulic end stop member that is disposed within the compression chamber 24 and operates to hydraulically dissipate the kinetic energy of the suspension during the shock absorber's compression stroke during the final section of the shock absorber's compression stroke, i.e., as the shock absorber approaches its end-of-compression position.

[0025] The hydraulic end stop member first has a cup-shaped body 36 attached to the lower end of the piston rod 18 below the main piston 20 and extending coaxially relative to the main piston, and a piston 38 (hereinafter referred to as the secondary piston to distinguish it from the main piston 20) mounted within the cup-shaped body 36 so as to slide along the longitudinal axis z.

[0026] The cup-shaped body 36 has a bottom wall 40 and a cylindrical side wall 42 and is arranged upside down, i.e., with the bottom wall 40 facing upwards, i.e., open at the bottom towards the main piston 20. The cylindrical side wall 42 of the cup-shaped body 36 has a plurality of holes 44 through which the damping fluid contained in the cup-shaped body 36 flows outward, i.e., towards the compression chamber 24, during the compression stroke of the shock absorber, and through which the damping fluid flows from the compression chamber 24 into the cup-shaped body 36 during the extension stroke of the shock absorber.

[0027] The secondary piston 38 also has a cup-shaped configuration in the illustrated example, with a bottom wall 46 and a cylindrical side wall 48. In this case, the bottom wall 46 faces the open end, i.e., the lower end, of the cup-shaped body 36. Advantageously, the secondary piston 38 is provided with sealing means (not shown), for example formed by a sealing ring, to ensure a tight seal between the cylindrical side wall 48 of the secondary piston 38 and the cylindrical side wall 42 of the cup-shaped body 36. In the illustrated example, the secondary piston 38 has a through hole 50 provided in the bottom wall 46 to allow the flow of damping fluid in a direction from the compression chamber 24 to the interior of the cup-shaped body 36.

[0028] A working chamber 52 is therefore defined within the cup-shaped body 36, the working chamber 52 being bounded at its top by the bottom wall 40 of the cup-shaped body 36, laterally by the cylindrical side wall 42 of the cup-shaped body 36, and at its bottom by the bottom wall 46 of the secondary piston 38.

[0029] Resilient means are provided within the cup-shaped body 36, for example formed by a conical spring 54, which acts on the secondary piston 38 to exert a downward resilient force thereon, thereby tending to hold the secondary piston 38 in a downward end-stroke position in which the secondary piston 38 abuts against a stop ring 56 attached to the lower end of the cup-shaped body 36.

[0030] The hydraulic end stop member further includes a pin 58 that is attached to the bottom valve assembly 30 of the shock absorber and extends upward, i.e., toward the assembly formed by the cup-shaped body 36 and the secondary piston 38. The pin 58 is arranged coaxially with respect to the shock absorber, i.e., its axis is substantially coincident with the longitudinal axis z.

[0031] As shown in Figure 1, the pin 58 is normally positioned some distance from the secondary piston 38. In this condition, the hydraulic end stop member is not activated and therefore the damping force generated thereby is zero, or substantially zero.

[0032] Referring now to Figures 2 to 4, the operation of the hydraulic end stop member is described during the final section of the shock absorber's compression stroke (Figures 2 and 3), and in the next stage when the operation is reversed, and thus during the first section of the shock absorber's extension stroke (Figure 4).

[0033] 2, at a certain point during the compression stroke of the shock absorber, the secondary piston 38, which is housed within the cup-shaped body 36 and is held by the conical spring 24 at the lower end of the cup-shaped body 36 as described above, comes into contact with a pin 58 attached to the bottom of the shock absorber. As a result, the through hole 50 provided in the secondary piston 38 is closed by the pin 58.

[0034] As the shock absorber continues its compression stroke (FIG. 3), the secondary piston 38 penetrates further and further into the cup-shaped body 36, thereby increasingly urging the secondary piston 38 toward the bottom wall 40 of the cup-shaped body 36, i.e., upward against the action of the conical spring 24. As a result, the volume of the working chamber 52 of the cup-shaped body 36 gradually decreases, thereby forcing the damping fluid contained therein to flow out through the holes 44 provided in the cylindrical side wall 42 of the cup-shaped body 36. However, as the secondary piston 38 moves toward the bottom wall 40 of the cup-shaped body 36, the number of holes 44 in the cylindrical side wall 42 of the cup-shaped body 36 through which the damping fluid can flow out of the working chamber 52 of the cup-shaped body 36 decreases, thus reducing the overall cross-sectional flow area for the outflow of damping fluid from the working chamber 52 of the cup-shaped body 36. This results in greater resistance to the downward movement of the shock absorber piston rod 18, and therefore an increase in damping force. The relationship between the increase in damping force and the displacement of the secondary piston 38 in the cup-shaped body 36 toward the bottom wall 40 (a displacement that coincides with the displacement of the piston rod 18 toward the bottom of the shock absorber) can be set by appropriately selecting the number, location, and / or shape of the holes 44 in the cylindrical side wall 42 of the cup-shaped body 36.

[0035] In order to limit the maximum pressure in the working chamber 52 of the cup-shaped body 36 and therefore the maximum force transmitted to the shock absorber piston rod 18 and thus to the vehicle, the cup-shaped body 36 is provided with a pressure limiting valve, generally designated 60. The pressure limiting valve 60 essentially comprises a set of discs 62 (or, more generally, at least one disc 62) arranged against the upper surface of the bottom wall 40 of the cup-shaped body 36, i.e., the surface facing the main piston 20, so as to prevent damping fluid from leaving the working chamber 52 through a through-hole 64 provided in the bottom wall 40 of the cup-shaped body 36 up to a predetermined limit value of the pressure in the working chamber 52. If the pressure in the working chamber 52 exceeds this limit value, the discs 62 undergo elastic deformation, thereby leaving a free passage between them and the upper surface of the bottom wall 40 of the cup-shaped body 36. Thus, damping fluid can flow from the working chamber 52 of the cup-shaped body 36 through the through-hole 64 and the free passage between the bottom wall 40 and the disc 62, thereby avoiding a further increase in pressure in the working chamber 52 and, consequently, a further increase in the damping force on the piston rod 18.

[0036] Starting from the state of FIG. 3 (or from a similar state in which the secondary piston 38 is displaced towards the bottom wall 40 of the cup-shaped body 36 relative to its initial position abutting the stop ring 56), when the piston rod 18 changes direction of movement, i.e., moves upward (extension movement), the pin 58 gradually moves away from the working chamber 52 of the cup-shaped body 36 and the secondary piston 38 gradually moves away from the bottom wall 40 of the cup-shaped body 36, thereby increasing the volume of the working chamber 52 and thus allowing damping fluid to enter the working chamber 52 from the compression chamber 24 of the shock absorber through the through-hole 50 in the secondary piston 38 and through the hole 44 in the cylindrical side wall 42 of the cup-shaped body 36, which gradually re-communicates with the working chamber 52 as a result of the downward movement of the secondary piston 38. This operating state is shown in FIG. 4.

[0037] 5, the cup-shaped body 36 is preferably fixed to the lower end of the shock absorber piston rod 18 by means of a thread, indicated at 66, usually provided at the end for the attachment of a nut, by means of which the shock absorber's main piston 20 is fixed to the piston rod 18. In this case, the bottom wall 40 of the cup-shaped body 36 therefore has an axial threaded hole 68 into which the aforementioned threaded portion 66 of the piston rod 18 can be screwed. Of course, if necessary, one or more spacers 70 can also be mounted on the piston rod 18 between the main piston 20 and the cup-shaped body 36 in order to accurately position the cup-shaped body 36 relative to the main piston 20 so as to avoid interference between said components, in particular between the disk 62 of the pressure limiting valve mounted on the bottom wall 40 of the cup-shaped body 36 and the main piston 20. In this way, the cup-shaped body 36 can be easily mounted onto the piston rod 18 of a normal shock absorber without requiring any special modification of the same piston rod.

[0038] As shown in the enlarged view of FIG. 6, the pin 58 is preferably secured to the shock absorber bottom valve assembly 30 by a nut using the threads of a bolt 72 normally provided for fastening the bottom valve assembly 30 to the shock absorber bottom. Therefore, in this case, the pin 58 has a blind threaded hole 74 at its lower end to allow it to be screwed onto the bolt 72. In this way, the pin 58 can be easily installed on a conventional shock absorber bottom valve assembly 30 without requiring any special modifications to the same valve assembly. To ensure good stability of the pin 58, it may be necessary to replace the bolt provided for mounting the conventional shock absorber bottom valve assembly 30 with a new, longer bolt 72, but this replacement can obviously be carried out in this case as a very simple and inexpensive operation.

[0039] Further embodiments of hydraulic shock absorbers according to the invention are shown in Figures 7 to 12, in which parts or elements that are identical to or correspond to those of the shock absorber according to the embodiment of Figures 1 to 6 are designated by the same reference numerals.

[0040] This further embodiment differs substantially from the previous embodiment in that the secondary piston 38 is not slidably mounted within the cup-shaped body 36 but is fixed to the free (upper) end of the pin 58, and in that the cup-shaped body 36 does not have a stop ring 56 such that during the compression stroke of the shock absorber, starting at a certain point until the end of the compression stroke, the secondary piston 38 penetrates into the cup-shaped body 36 and begins to slide within it, thereby reducing the volume of the working chamber 52 of the cup-shaped body 36. In this regard, Figure 8 shows the secondary piston 38 beginning to enter the cup-shaped body 36 during the compression stroke of the shock absorber, thereby closing the working chamber 52, Figure 9 shows the secondary piston 38 still completely inside the cup-shaped body 36 during the compression stroke of the shock absorber, while Figure 10 shows the secondary piston 38 still inside the cup-shaped body 36 but moving downward relative to the cup-shaped body 36 during the extension stroke of the shock absorber.

[0041] Furthermore, according to this embodiment, the secondary piston 38 is provided with a check valve 76 whose function is to allow damping fluid to enter the working chamber 52 of the cup-shaped body 36 during the extension stroke of the shock absorber. The check valve 76 basically includes one or more disks 78 arranged on an upper surface of the secondary piston 38 and adapted to close a plurality of axial through-holes 80 extending through the secondary piston 38 parallel to its axis (i.e., parallel to the longitudinal axis z). The disks 78 keep the axial through-holes 80 closed during the compression stroke, while during the extension stroke, the axial through-holes 80 deflect or move relative to the upper surface of the secondary piston 38 (e.g., tend to hold the disks 78 against the action of elastic means (not shown)) to allow fluid to flow through the axial through-holes 80. Thus, during the shock absorber extension stroke, when the secondary piston 38 is still inside the cup-shaped body 35 (as shown in FIG. 10 ), the check valve 76 allows damping fluid to flow from the shock absorber's compression chamber 24 through the axial through-hole 80 in the secondary piston 38 and through the hole 44 in the cylindrical side wall 42 of the cup-shaped body 36 to the working chamber 52 of the cup-shaped body 36.

[0042] 1 to 6 also applies in all other respects. In particular, in this case too, the cup-shaped body 36 is preferably fixed to the lower end of the shock absorber piston rod 18 by a threaded portion 66 provided at its end, possibly with one or more spacers 70 interposed between the main piston 20 and the cup-shaped body 36, as shown in the enlarged scale view of FIG. 11. It is further preferably fixed to the shock absorber bottom valve assembly 30 by a bolt 72 provided for locking the bottom valve assembly 30 to the bottom of the shock absorber by a nut, as shown in the enlarged scale view of FIG. 12.

[0043] As is clear from the above description, by using the hydraulic end stop member according to the present invention, it is possible to realize an increased damping force on the shock absorber piston rod in the final section of the shock absorber's compression stroke, without changing the behavior of the shock absorber under other operating conditions. The hydraulic end stop member can be easily installed on existing shock absorbers without requiring any modifications to the shock absorber's cylinder or piston rod. Furthermore, in the case of the hydraulic end stop member according to the present invention, the calibration operation of the end stop member can be performed very simply and quickly, since the cup-shaped body and the secondary piston (if not located in the cup-shaped body) can be easily removed from the shock absorber.

[0044] Furthermore, experiments carried out by the applicant have shown that the hydraulic end stop member according to the invention is able to increase the damping force acting on the piston rod in the final section of the shock absorber's compression stroke, even at low speeds, ensuring good progressivity in the force increase and avoiding discontinuities at the start of the final section of the shock absorber's compression stroke and also avoiding delays in the increase of the damping force.

[0045] The present invention has been described herein with reference to preferred embodiments thereof. It is to be understood that other embodiments may be envisioned that share the same inventive core as described herein, as defined by the following claims.

Claims

1. A hydraulic shock absorber (10), in particular for a vehicle suspension, comprising: a first cylindrical tube (14), a piston rod (18) arranged coaxially with respect to said first cylindrical tube (14) and projecting from the upper side of said first cylindrical tube (14); a main piston (20) attached to said piston rod (18), said main piston (20) slidably mounted within said first cylindrical tube (14) so ​​as to divide the internal volume of said first cylindrical tube (14) into a tension chamber (22) and a compression chamber (24) containing a damping fluid; a hydraulic end stop member (36, 38, 58) disposed within the compression chamber (24), the hydraulic end stop member (36, 38, 58) configured to operate during the final section of the compression stroke of the shock absorber (10) to hydraulically dissipate the kinetic energy of the piston rod (18); and a hydraulic shock absorber (10) wherein the hydraulic end stop member (36, 38, 58) has a cup-shaped body (36) and a secondary piston (38), the secondary piston (38) being arranged to slide within the cup-shaped body (36) during the final section of the compression stroke of the shock absorber (10) to compress damping fluid contained in a working chamber (52) defined between the cup-shaped body (36) and the secondary piston (38); the cup-shaped body (36) is attached to the piston rod (18) below the main piston (20) and is positioned so as to be open at its bottom; and the hydraulic end stop member (36, 38, 58) further comprises a pin (58) attached to a bottom region of the first cylindrical tube (14) and extending coaxially with the cup-shaped body (36), the pin (58) being associated with the secondary piston (38) to allow the secondary piston (38) to slide within the cup-shaped body (36) during the final section of the compression stroke of the shock absorber (10); A hydraulic shock absorber (10) characterized by:

2. 2. The shock absorber of claim 1, wherein the cup-shaped body has a bottom wall facing the main piston and a cylindrical side wall, the cylindrical side wall having a plurality of first holes for fluidly connecting the working chamber of the cup-shaped body with the compression chamber of the shock absorber, the first holes being configured such that as the secondary piston slides within the cup-shaped body toward the bottom wall, an overall cross-sectional flow area for the outflow of the damping fluid from the working chamber through the first holes decreases.

3. 3. The shock absorber of claim 2, wherein the bottom wall of the cup-shaped body has a plurality of second holes arranged to fluidly connect the working chamber of the cup-shaped body with the compression chamber of the shock absorber, and the cup-shaped body includes a pressure limiting valve arranged to limit a maximum value of pressure in the working chamber of the cup-shaped body during the final section of the compression stroke of the shock absorber, thereby allowing the damping fluid to exit the working chamber through the second holes when the pressure in the working chamber exceeds a predetermined limit.

4. 4. The shock absorber according to claim 1, wherein the cup-shaped body (36) is twisted onto a threaded portion (66) of the piston rod (18) at the lower end of the piston rod (18).

5. 5. The shock absorber according to claim 1, further comprising: a second cylindrical tube (12) disposed outside the first cylindrical tube (14) and coaxially relative to the first cylindrical tube (14), thereby defining an annular chamber (16) with the first cylindrical tube (14) at an upper portion thereof, the annular chamber (16) being filled with gas; and a valve assembly (30) disposed at a bottom of the first cylindrical tube (14), the valve assembly (30) having a compression valve (34) that controls the flow of the damping fluid from the compression chamber (24) to the annular chamber (16) during the compression phase, and an intake valve (32) that controls the flow of the damping fluid from the annular chamber (16) to the compression chamber (24) during the extension phase.

6. 6. The shock absorber of claim 5, wherein the valve assembly (30) is attached to the bottom of the first cylindrical tube (14) by a bolt (72), and the pin (58) of the hydraulic end stop member (36, 38, 58) is threadably mounted onto the bolt (72).

7. 7. The shock absorber of claim 2, wherein the secondary piston is mounted within the cup-shaped body, the cup-shaped body comprising elastic means configured to exert an elastic force on the secondary piston tending to urge the secondary piston towards a rest position located at a predetermined distance from the bottom wall of the cup-shaped body, and the pin is configured to penetrate into the cup-shaped body in the final section of the compression stroke of the shock absorber, thereby urging the secondary piston along the cup-shaped body towards the bottom wall against the action of the elastic means.

8. 8. The shock absorber of claim 7, wherein the cup-shaped body (36) comprises a stop means (56) configured to prevent the secondary piston (38) from being biased by the resilient means (54) beyond the rest position.

9. 9. The shock absorber of claim 7, wherein the secondary piston has at least one axial through-hole for fluidly connecting the working chamber of the cup-shaped body with the compression chamber of the shock absorber, the at least one axial through-hole being closed by the pin when the pin abuts against the secondary piston in the final section of the compression stroke of the shock absorber.

10. 7. The shock absorber according to claim 2, wherein the secondary piston (38) is mounted on the pin (58), in particular at the end of the pin (58) facing the main piston (20), so as to penetrate into the cup-shaped body (36) in the final section of the compression stroke of the shock absorber (10).

11. 11. The shock absorber of claim 10, wherein the secondary piston has at least one axial through-hole and includes a check valve arranged to prevent the damping fluid from exiting the working chamber of the cup-shaped body through the at least one axial through-hole during the final section of the compression stroke of the shock absorber, but to allow the damping fluid to enter the working chamber of the cup-shaped body through the at least one axial through-hole during the extension stroke of the shock absorber as long as the secondary piston is inside the cup-shaped body.

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