Shock absorbers with hydraulic rebound stops

Abstract

A hydraulic shock absorber (10), in particular for vehicle suspensions, comprises a cylindrical tube (14), a rod (18), a primary piston (20) and a hydraulic stopper (30), the hydraulic stopper (30) comprising a cup-shaped body (32) and an auxiliary piston (34), the auxiliary piston (34) comprising a cylindrical body (50) made of plastic, a sealing ring (54) also made of plastic and an annular body (60) made of a metallic material, suitable for forming a support surface or an axial support seat for the cylindrical body (50).

Description

[0001] The present invention generally relates to hydraulic end-of-travel stops on hydraulic shock absorbers (e.g., monotube or twin-tube types) used in vehicle suspensions. More particularly, the present invention relates to hydraulic stops that operate during the extension motion of the shock absorber.

[0002] Conventionally, a hydraulic shock absorber for a vehicle suspension has a first end-of-stroke buffer disposed inside the shock absorber and configured to act during an extension stroke of the shock absorber, and a second end-of-stroke buffer disposed outside the shock absorber and configured to act during a compression stroke of the shock absorber.

[0003] End-of-stroke buffers can be of elastic or hydraulic type.

[0004] Elastic end-of-stroke bumpers are made of a high-stiffness elastomeric material (such as polyurethane). Their function is to ensure that when the shock absorber reaches the end of its stroke, both during the extension and compression phases, there is an elastic impact between the contacting surfaces, thereby preventing these impacts from occurring between metal surfaces. Thus, the elastic end-of-stroke bumper behaves like a spring, acting in parallel with the suspension's mechanical springs (main springs) at the end of the stroke and having a much higher stiffness than the suspension's mechanical springs. However, the elastic end-of-stroke bumper does not act at any intermediate points in the shock absorber's travel.

[0005] Elastic end-of-travel dampers have the following disadvantages, among other things. When a damper is subjected to a violent impact, such as tension or compression caused by an obstacle (pothole or bump) on the road, the kinetic energy of the suspension is converted into elastic deformation energy of the associated damper. The elastic energy stored in the damper is completely (or almost) released in the next phase of the reversal of motion. Consequently, after the impact, the suspension continues to vibrate without being adequately damped, and these vibrations worsen the contact conditions between the road and the tires, thereby deteriorating the vehicle's grip on the road.

[0006] In order to overcome the above-mentioned disadvantages of elastic buffers, it is known to use hydraulic stops alone or in combination with elastic buffers.

[0007] Hydraulic brakes are dissipative devices that, depending on the speed of the shock absorber's movement, allow the suspension's kinetic energy to be dissipated hydraulically when the end-of-stroke position is reached. This involves forcing a certain volume of oil contained in the shock absorber through appropriately calibrated channels. In this way, the energy generated by an impact is hydraulically dissipated and cannot be returned to the suspension in the subsequent reversal of movement. Suspension vibrations are thus dampened, improving the grip conditions between the road and the tires, and consequently, the vehicle's grip on the road.

[0008] Furthermore, since the hydraulic stop acts in parallel with its respective elastic buffer, part of the energy generated by the impact is absorbed hydraulically, thereby allowing the size of the elastic buffer and its support to be reduced.

[0009] Finally, while elastic buffers react only to the deformation they undergo, hydraulic stops act in direct proportion to the speed at which the shock absorber rod reaches its end-of-travel position. Therefore, hydraulic stops can better handle the impact that occurs when the shock absorber reaches its end-of-travel position, resulting in lower noise levels.

[0010] Hydraulic stops are commonly used as end-of-stroke devices. Automotive hydraulic stops include a cup-shaped body adapted to be attached to the rebound chamber of a shock absorber, and a piston adapted to be attached to the shock absorber's rod. The piston slides along the cylindrical sidewall of the cup-shaped body. This wall conveniently has a series of channels to allow oil to escape when the piston is pushed toward the cup-shaped body during the shock absorber's extension stroke, thereby compressing the oil contained in the cup-shaped body's working chamber.

[0011] In a shock absorber thus constructed, the movement of the piston and the shock absorber rod is damped during the shock absorber extension stroke because oil leaks out of the cup-shaped body through passages provided in the cylindrical sidewall of the cup-shaped body. These passages have a decreasing cross-section in the direction of the shock absorber extension stroke, which increases the damping effect of the device as the piston moves toward the interior of the cup-shaped body.

[0012] The object of the present invention is to provide a hydraulic damper operating during extension of a hydraulic shock absorber for a vehicle suspension, which combines strength, low inertia and an optimum coefficient of friction at the interface between piston and cup.

[0013] Another object of the present invention is to provide a hydraulic damper which can be manufactured in a simple and economical manner.

[0014] These and other objects are fully achieved according to the present invention by a hydraulic stop having the characteristics defined in the appended claims.

[0015] In summary, the present invention is based on the idea of ​​manufacturing the piston components (i.e. the cylinder and / or the sealing ring, as defined below) and / or the cup-shaped body from plastic material, whereby these components can be shaped in a manner that improves the mechanical and structural properties of the device. This allows the device to be lighter from a structural point of view and simplifies manufacturing.

[0016] Advantageous embodiments of the invention are specified in the dependent claims, the content of which is to be understood as an integral part of the following description.

[0017] BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The functions and structural features of some preferred embodiments of a shock absorber with a hydraulic rebound buffer according to the present invention will now be described with reference to the accompanying drawings, in which:

[0019] - Figure 1 is an axial cross-sectional view of a shock absorber including a rebound stop according to one embodiment of the present invention;

[0020] - Figure 2 is an axial cross-sectional view of a hydraulic rebound stopper incorporated in a shock absorber according to one embodiment of the present invention;

[0021] - Figure 3 is a longitudinal sectional exploded view of a hydraulic rebound stopper according to one embodiment of the present invention;

[0022] 4A and 4B are two perspective views of a piston for a hydraulic stopper during an extension stroke of a shock absorber and during a compression stroke of the shock absorber, respectively, according to one embodiment of the present invention;

[0023] 5A and 5B are respectively a side view and a perspective view from below of a piston for a hydraulic stopper according to one embodiment of the present invention; and

[0024] 6A and 6B are side and top perspective views, respectively, of a piston for a hydraulic stopper according to another embodiment of the present invention.

[0025] Detailed description

[0026] Before describing in detail various embodiments of the present invention, it should be clarified that the present invention is not limited in its application to the construction details and configurations of components presented in the following description or illustrated in the accompanying drawings. The present invention may adopt other embodiments and be implemented or constructed in practice in various ways. It should also be understood that the phraseology and terminology are for descriptive purposes only and should not be interpreted as limiting.

[0027] By way of example, refer to Figure 1 The hydraulic shock absorber 10, in particular for a vehicle suspension, comprises a cylindrical tube 14; a rod 18; the rod 18 is coaxially arranged with the cylindrical tube 14 and partially protrudes from it; and a primary piston 20, which is attached to a first end of the rod 18 and is slidably mounted in the cylindrical tube 14, thereby dividing the internal volume of the cylindrical tube 14 into an extension chamber 22 and a compression chamber 24.

[0028] The hydraulic shock absorber 10 further includes a hydraulic stopper 30 disposed in the extension chamber 22 and adapted to operate during the extension stroke of the shock absorber 10 to hydraulically dissipate kinetic energy as the shock absorber 10 approaches an end position of the extension stroke.

[0029] The hydraulic stopper 30 includes a cup 32 mounted coaxially in the extension chamber 24 of the shock absorber 10 and an auxiliary piston 34 mounted coaxially to the first end of the rod 18 of the shock absorber 10 and above the primary piston 20 of the shock absorber.

[0030] The cup-shaped body 32 in turn comprises a side wall 36 which, together with the auxiliary piston 34 of the hydraulic stop 30, defines a working chamber 52 which coincides appropriately with the end portion of the extension chamber 24. Said working chamber 52 is thus contained within the internal volume of the cup-shaped body 32 and is configured such that the damping fluid coming from the shock absorber 10 is compressed by the auxiliary piston 34 of the hydraulic stop 30 during the extension stroke of the shock absorber.

[0031] The auxiliary piston 34 includes a cylindrical body 50 attached to the rod 18 of the shock absorber 10 and having an outer diameter smaller than the inner diameter of the side wall 36 of the cup-shaped body 32; a sealing ring 54 axially slidably mounted about the cylindrical body 50 and adapted to seal against the inner surface of the side wall 36 of the cup-shaped body 32; and first and second annular support members 56, 58 axially constrained to the cylindrical body 50 and configured to axially limit axial sliding of the sealing ring 54 along the cylindrical body 50 in either direction. In short, the first annular support member 56 (i.e., an axial lower end support seat for the sealing ring 54, as shown in FIG. 5 ) is provided. Figure 3 and 4B ) is formed by the upper surface of a ring which is integrally formed with a portion of the cylindrical body 50.

[0032] The sealing ring 54, the first support element 56, and the second support element 58 are configured so that during an extension stroke of the shock absorber 10, when the sealing ring 54 runs along the inner surface of the side wall 36 of the cup-shaped body 32, the sealing ring 54 abuts against the first support element 56 and does not allow the damping fluid to flow from one side of the sealing ring 54 to the other side, while during a compression stroke of the shock absorber 10, the sealing ring 54 abuts against the second support element 58 and allows the damping fluid to flow from one side of the sealing ring 54 to the other side.

[0033] The cylindrical body 50 and the sealing ring 54 are made of plastic material, and the auxiliary piston 34 further includes an annular body 60 made of metal material, which is suitable for forming a supporting surface or an axial supporting seat for the cylindrical body 50 .

[0034] In practice, the annular body 60 is coupled to the cylindrical body 50 on the side of the auxiliary piston 34 axially opposite to the side facing the working chamber 52. The auxiliary piston 34 is thus configured so that, when the cylindrical body 50 reaches the end position of the extension stroke of the hydraulic shock absorber 10, the annular body 60 forms an axial support seat for said cylindrical body 50, preventing it from sliding in the opposite direction along the rod 18 and axially locking the auxiliary piston 34 on the rod 18. To this end, the cup-shaped body 32 is preferably provided with a shoulder 38 which projects radially inwardly from the cup-shaped body 32 and is suitable for forming a support seat against which the auxiliary piston 34 will come to rest when the hydraulic shock absorber 10 is in the end position of the extension stroke (e.g., Figure 2 shown).

[0035] According to one embodiment (in Figure 2 ), the rod 18 comprises a coupling seat having a profile complementary to the inner profiles of the cylinder 50 and the annular body 60, whereby said cylinder 50 and the annular body 60 are attached to the rod 18 by shape-coupling of their respective profiles.

[0036] Preferably, the rod 18 has two circumferential grooves at the axially outermost edges of the cylindrical body 50 and the annular body 60, said outermost edges being radially recessed toward the axis of the rod 18, whereby they abut within their respective circumferential recesses. Thus, an optimally shaped coupling of the auxiliary piston 34 to the piston rod 18 is achieved.

[0037] The annular body 60 is in turn connected to the cylindrical body 50 by a form coupling between at least one hook 62 projecting axially from the cylindrical body 50 and a projection projecting radially from the annular body 60 .

[0038] The coupling may be achieved by configuring the hook 62 to engage with the protrusion of the ring body 60 by externally surrounding the protrusion of the ring body 60 (eg, as shown in FIG. 5A and FIG. 5B ).

[0039] Alternatively (eg, as shown in FIG. 6A and FIG. 6B ), the protrusion radially projecting from the annular body 60 may include at least one radial seat 64 configured as a groove into which the hook 64 is inserted and secured.

[0040] According to one embodiment, the sealing ring 54 has an open annular shape.

[0041] According to a preferred embodiment, the cup-shaped body 32 is made of plastic material.

[0042] According to a preferred embodiment, the plastic material of the cylindrical body 50 and / or the sealing ring 54 and / or the cup-shaped body 32 is a composite material reinforced with glass fibers or carbon fibers.

[0043] According to a preferred embodiment, the hydraulic shock absorber 10 is configured as a double-tube hydraulic shock absorber for a vehicle suspension. In this configuration, the hydraulic shock absorber 10 includes an outer cylindrical tube (coinciding with the main body tube 15 of the hydraulic shock absorber 10) and an inner cylindrical tube (in this embodiment, coinciding with the above-mentioned cylindrical tube 14, with the cup-shaped body 32 radially abutting against the cylindrical tube 14). The inner cylindrical tube is coaxial with the outer cylindrical tube and defines an annular chamber filled with gas at its upper portion, and the rod 18 is arranged coaxially with the two cylindrical tubes and partially extends therefrom. The main piston 20 is slidably mounted in the inner cylindrical tube and attached to the lower end of the rod 18. The main piston 20 divides the internal volume of the inner cylindrical tube 14 into an extension chamber and a compression chamber, which contain a damping fluid (oil).

[0044] According to one aspect of the present invention (not shown), the hydraulic shock absorber 10 is configured as a single-tube hydraulic shock absorber for a vehicle suspension, i.e., it comprises only an outer cylindrical tube (coinciding with the main body tube 15 in the hydraulic shock absorber 10, which in turn coincides with the cylindrical tube 14 in this embodiment, and the cup-shaped body 32 radially abuts against the cylindrical tube 14).

[0045] Preferably, an axial passage 44 is provided on the inner surface of the side wall 36 of the cup 32, extending parallel to the longitudinal axis (z) of the cup 32, and adapted to allow damping fluid to flow axially out of the working chamber 52 as the auxiliary piston 34 flows through the working chamber 52 toward the end position of the extension stroke of the shock absorber 10 (e.g., toward the shoulder 38 of the cup 32).

[0046] The axial channel 44 has a cross-section whose area decreases continuously along the longitudinal axis (z) toward the end position of the extension stroke of the shock absorber 10 .

[0047] According to the invention, the cup-shaped body 32 is made of plastic material and the entire outer surface of the side wall 36 of the cup-shaped body 32 is in direct contact with the cylindrical tube 14 forming the outer cylindrical tube 10 of the shock absorber. More precisely, the purpose is to provide a portion of the cup-shaped body 32 (axially) along which the auxiliary piston 34 slides, with which substantially the entire surface of the side wall 36 corresponding to said portion and facing the inner wall of the cylindrical tube 15 is in contact.

[0048] Throughout the present description and claims, terms and expressions indicating position and orientation, such as “longitudinal”, “transverse”, “vertical” or “horizontal”, refer to the longitudinal axis (z) of the hydraulic shock absorber 10 .

[0049] Various aspects and embodiments of a hydraulic shock absorber with a hydraulic rebound stop according to the present invention have been described. It will be appreciated that each embodiment can be combined with any other embodiment. Furthermore, the present invention is not limited to the described embodiments but may be varied within the scope of the appended claims.

Claims

1. A hydraulic shock absorber (10), comprising Cylindrical tube (14), a rod (18) arranged coaxially with the cylindrical tube (14) and partially projecting therefrom, a main piston (20) fixed to the first end of the rod (18) and slidably mounted in the cylindrical tube (14) so ​​as to divide the interior volume of the cylindrical tube (14) into an extension chamber (22) and a compression chamber (24), and a hydraulic damper (30) disposed in the extension chamber (22) and adapted to operate during the extension stroke of the shock absorber (10) to hydraulically dissipate kinetic energy as the shock absorber (10) approaches an end-of-stroke position; in, The hydraulic buffer (30) includes a cup-shaped body (32) mounted in and coaxial with the extension chamber (22) of the shock absorber (10), and an auxiliary piston (34) mounted at the first end of the rod (18) of the shock absorber (10) and coaxial with the rod (18) above the main piston (20) of the shock absorber, and The cup-shaped body (32) includes a side wall (36), and the side wall (36) and the auxiliary piston (34) of the hydraulic buffer (30) together define a working chamber (52). During the extension stroke of the shock absorber (10), the damping fluid of the shock absorber (10) is compressed in the working chamber (52) by the auxiliary piston (34) of the hydraulic buffer (30). The auxiliary piston (34) comprises a cylindrical body (50) fixed to the rod (18) of the shock absorber (10) and having an outer diameter smaller than the inner diameter of the side wall (36) of the cup-shaped body (32); a sealing ring (54) axially slidably mounted around the cylindrical body (50) and adapted to seal against the inner surface of the side wall (36) of the cup-shaped body (32); and a first support element (56) and a second support element (58) axially constrained to the cylindrical body (50) and configured to axially limit the sealing ring (54) along the cylindrical body (50) in two directions. The sealing ring (54), the first support element (56) and the second support element (58) are configured so that when the sealing ring (54) slides along the inner surface of the side wall (36) of the cup-shaped body (32) during the extension stroke of the shock absorber (10), the sealing ring abuts against the first support element (56) and no damping fluid passes from one side of the sealing ring (54) to the other side, while during the compression stroke of the shock absorber (10), the sealing ring (54) abuts against the second support element (58) and allows the damping fluid to pass from one side of the sealing ring (54) to the other side, The cylinder (50) and the sealing ring (54) are made of plastic. And wherein the auxiliary piston (34) further comprises an annular body (60) made of a metal material, said annular body (60) being coupled to the cylindrical body (50) on the side of the auxiliary piston (34) axially opposite to the side facing the working chamber (52), said annular body (60) being adapted to form a support surface or an axial support seat for the cylindrical body (50), It is characterized by: The annular body (60) is connected to the cylindrical body (50) by a form coupling between at least one hook (62) protruding axially from the cylindrical body (50) and a protrusion protruding radially from the annular body (60).

2. The hydraulic shock absorber according to claim 1, characterized in that: The rod (18) comprises a coupling seat having a profile complementary to the inner profiles of the cylinder (50) and the annular body (60), so that the cylinder (50) and the annular body (60) are fixed to the rod (18) by the shape coupling of their respective profiles.

3. The hydraulic shock absorber according to claim 2, characterized in that: The rod (18) has two circumferential recesses at the axially outermost edges of the cylindrical body (50) and the annular body (60), and the outer edges are radially recessed toward the axis of the rod (18) so as to abut against the corresponding circumferential recesses.

4. The hydraulic shock absorber according to claim 1, characterized in that: The protrusion radially protruding from the annular body (60) includes at least one radial seat (64) configured as a groove for inserting and fixing the hook (62).

5. The hydraulic shock absorber according to any one of claims 1 to 4, characterized in that: The plastic material from which the sealing ring (54) is made is a composite material which is reinforced with glass fibers or carbon fibers.

6. The hydraulic shock absorber according to any one of claims 1 to 4, characterized in that: The cup (32) is provided with a shoulder (38) which projects radially towards the inside of the cup (32) and is suitable for forming a stop against the auxiliary piston (34) when the hydraulic shock absorber (10) is in the end position of the extension stroke.

7. The hydraulic shock absorber according to any one of claims 1 to 4, characterized in that: The sealing ring (54) has an open ring shape.

8. The hydraulic shock absorber according to any one of claims 1 to 4, characterized in that: The hydraulic shock absorber (10) is configured as a double-tube hydraulic shock absorber for a vehicle suspension, comprising an outer cylindrical tube coinciding with a main body tube (15) of the hydraulic shock absorber (10), and an inner cylindrical tube coinciding with the cylindrical tube (14), a cup-shaped body (32) radially abutting against the cylindrical tube (14), the inner cylindrical tube being coaxial with the outer cylindrical tube and defining an annular chamber filled with gas at its upper portion between the inner cylindrical tube and the outer cylindrical tube, and a rod (18) being coaxially arranged with the cylindrical tube and partially extending therefrom.

9. The hydraulic shock absorber according to any one of claims 1 to 4, characterized in that: The hydraulic shock absorber (10) is configured as a single-tube hydraulic shock absorber for vehicle suspension, comprising only a main body tube (15) of the hydraulic shock absorber (10), the main body tube (15) coinciding with a cylindrical tube (14), and the cylindrical tube (14) radially abutting against a cup-shaped body (32).

10. The hydraulic shock absorber according to any one of claims 1 to 4, characterized in that: An axial channel (44) is provided on the inner surface of the side wall (36) of the cup-shaped body (32), extending parallel to the longitudinal axis (z) of the cup-shaped body (32) and adapted to allow the damping fluid to flow axially out of the working chamber (52) when the auxiliary piston (34) slides into the working chamber (52) toward the end of the extension stroke of the shock absorber (10), the axial channel (44) having a cross-section whose area continuously decreases along the longitudinal axis (z) toward the end of the extension stroke of the shock absorber (10).

11. The hydraulic shock absorber according to any one of claims 1 to 4, characterized in that: The cup-shaped body (32) is made of plastic material.

12. The hydraulic shock absorber according to any one of claims 1 to 4, characterized in that: The hydraulic shock absorber (10) is used for vehicle suspension.

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