Hydraulic shock absorber, particularly for vehicle suspension

Abstract

A hydraulic shock absorber (10) comprises an inner cylindrical tube (16) and an outer cylindrical tube (18), which delimit a reservoir chamber (20) containing a damping fluid; a first intermediate cylindrical tube (36), which delimits, with the inner cylindrical tube (16), a first intermediate chamber (38), and a first electronically controlled valve (42), adapted to put the first intermediate chamber (38) in fluid communication with the reservoir chamber (20); and a valve assembly (48) located within the reservoir chamber (20) between the first intermediate cylindrical tube (36) and the first electronically controlled valve (42), which valve assembly is configured so as to allow a passage of fluid from the first intermediate chamber (38) to the first electronically controlled valve (42) in a rebound condition of the shock absorber (10), and a passage of fluid from the reservoir chamber (20) to the first intermediate chamber (38) in a compression condition.

Description

[0001] Hydraulic shock absorber, particularly for vehicle suspension

[0002] The present invention relates to a hydraulic shock absorber with variable damping, intended to be used in particular in a vehicle suspension, as specified in the preamble of the independent claim 1.

[0003] Variable damping hydraulic shock absorbers comprising two electronically controlled valves, made for example as solenoid valves, are known.

[0004] In these solutions, a first valve will be arranged to regulate the flow of the damping fluid of the shock absorber during the compression phase only, while the other valve will be arranged to regulate the flow of the damping fluid during the rebound phase only.

[0005] A shock absorber of the aforesaid type is known for example from DE 102005 053 394 Al.

[0006] According to such known solutions, 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 to the two cylindrical tubes and partially protruding therefrom, and a piston which is slidably mounted in the inner cylindrical tube and is 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, wherein the damping fluid is contained. The piston is provided with a first valve assembly comprising a pair of one-way valves, namely a compensation valve, which during the compression phase of the shock absorber regulates the flow of the damping fluid from the compression chamber to the rebound chamber, and a rebound valve, which during the rebound phase of the shock absorber regulates the flow of the damping fluid from the rebound chamber to the compression chamber. At the bottom of the inner cylindrical tube, a second valve assembly is mounted, comprising a pair of one-way valves, namely a compression valve, which during the compression phase adjusts the flow of the damping fluid from the compression chamber to the reservoir chamber, and a suction valve, which during the rebound phase regulates the flow of the damping fluid from the reservoir chamber to the compression chamber. The oneway valves of both the first valve assembly and the second valve assembly are made as passive valves.

[0007] A shock absorber known from DE 102005053 394 Al further comprises a first and a second electronically controlled valve arranged to regulate the flow of the damping fluid during the rebound phase and during the compression phase, 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 in permanent fluid communication with the rebound chamber. The first electronically controlled valve is arranged to regulate, during the rebound phase, the flow of the damping fluid from the rebound chamber to the reservoir chamber through the first intermediate chamber, and thus to adjust the damping force of the shock absorber during said 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 in permanent fluid communication with the compression chamber. The second electronically controlled valve is arranged to regulate, during the compression phase, the flow of the damping fluid from the compression chamber to the reservoir chamber through the second intermediate chamber, and thus to adjust the damping force of the shock absorber during this phase.

[0008] However, in such a configuration the first intermediate cylindrical tube (radially interposed between the inner cylindrical tube and the outer cylindrical tube) is made in two parts, in order to house a valve that allows for the correct sorting of the flow rates in the rebound and compression conditions, from and to the relevant intermediate chamber.

[0009] Such an intermediate tube is complex to manufacture, as is the valve to be housed therein.

[0010] An object of the present invention is to provide a hydraulic shock absorber with variable damping that has a simplified architecture, maintaining the advantages of using two electronically controlled valves. This and other objects are achieved, according to the present invention, by virtue of a variable damping hydraulic shock absorber having the features defined in the accompanying independent claim 1.

[0011] 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 description that follows.

[0012] In short, the invention is based on the idea of constructing an electronic shock absorber equipped with two proportional valves, connected to the rebound chamber and compression chamber, respectively, by means of two respective bypass tubes which create, with the inner cylinder, a rebound bypass chamber and a compression bypass chamber, respectively.

[0013] With respect to the known solutions mentioned above, the architecture of a shock absorber according to the present invention provides for the suction valve (from the reservoir to the rebound chamber) to be adjacent to the proportional rebound valve, rather than inside the rebound bypass chamber.

[0014] This suction valve is preferably formed of two metal shells with a disk and a wave spring interposed.

[0015] The preassembled valve block is interposed between the proportional valve and the rebound bypass tube.

[0016] This solution has considerable geometric advantages, since it makes it possible to reduce the radial dimensions of the rebound bypass tube, which no longer has to accommodate the valve assembly. Furthermore, this bypass tube also has a simplified structure, as it is no longer formed of two separate parts, but rather of a single tube.

[0017] Further features and advantages of the present invention will become clearer from the detailed description that follows, given purely by way of non-limiting example with reference to the accompanying drawings, wherein: - Fig. 1 is a schematic view in axial cross-section of a hydraulic shock absorber according to one embodiment of the invention;

[0018] - Fig. 2 and 3 are schematic views in axial cross-section of a portion of the hydraulic shock absorber in Fig. 1, during a rebound and compression phase, respectively; and

[0019] - Fig. 4 and 5 are views showing respective enlargements of portions of Fig. 2 and 3, depicting the directions of the flows of the working fluid in the two operating conditions of the shock absorber.

[0020] Detailed description

[0021] Before explaining in detail a plurality of embodiments of the invention, it should be clarified that the invention is not limited in its application to the construction details and configuration of the components presented in the following description or illustrated in the drawings. The invention is capable of assuming other embodiments and of being implemented or manufactured in practice in different ways. It should also be understood that the phraseology and terminology have a descriptive purpose and should not be understood as limiting.

[0022] With reference to Fig. 1, a hydraulic shock absorber with variable damping (hereinafter referred to simply as the shock absorber), intended in particular to be used in a vehicle suspension, is indicated as a whole by reference sign 10.

[0023] The shock absorber 10 essentially comprises a cylindrical body 12 (hereinafter referred to simply as the body) extending along a longitudinal axis x, and a rod 14 that protrudes (upwards, according to the point of view of the observer of the figure) partially from the body 12 and is movable axially (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 (which is typically oil and will therefore, for simplicity, be referred to hereinafter as oil). A piston 22 is slidably mounted in the inner cylindrical tube 16 and is fixed to the lower end of the rod 14. The piston 22 separates 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).

[0025] The piston 22 may be provided with a first valve assembly comprising a pair of one-way valves, namely a compensation valve, which allows the oil to flow only in the direction from the compression chamber 26 to the rebound chamber 24, and a rebound valve, which allows the oil to flow only in the direction from the rebound chamber 24 to the compression chamber 26.

[0026] A first intermediate cylindrical tube 36 is also arranged around the inner cylindrical tube 16, coaxially thereto, which first intermediate cylindrical tube delimits, together with the inner cylindrical tube 16, a first intermediate chamber 38 in fluid communication with the rebound chamber 24.

[0027] There is also a first electronically controlled valve 42, arranged in such a way to protrude radially outward from the outer cylindrical tube 18 and configured so as to put the first intermediate chamber 38 in fluid communication with the reservoir chamber 20 and to control the flow of the damping fluid from one to the other.

[0028] The shock absorber 10 further comprises a second intermediate cylindrical tube 39, arranged around the inner cylindrical tube 16 coaxially thereto, which second intermediate cylindrical tube delimits a second intermediate chamber 40 in fluid communication with the compression chamber 26, and a second electronically controlled valve 44, arranged in such a way as to protrude radially outward from the outer cylindrical tube 18 and configured so as to put the second intermediate chamber 40 in fluid communication with the reservoir chamber 20 and to control the flow of the damping fluid from one to the other.

[0029] A valve assembly 48 is located within the reservoir chamber 20 in a position interposed between the first intermediate cylindrical tube 36 and the first electronically controlled valve 42, this valve assembly 48 being configured in such a way that, in a rebound condition of the shock absorber 10 (as illustrated by way of example in Fig. 2), a passage of fluid is allowed from the first intermediate chamber 38 to the first electronically controlled valve 42 (and preferably a fluid connection between the first intermediate chamber 38 and the reservoir chamber 20 is prevented, except for by means of the first electronically controlled valve 42), while in a compression condition of the shock absorber 10 (as illustrated by way of example in Fig. 3), a passage of fluid is allowed from the reservoir chamber 20 to the first intermediate chamber 38, and a fluid connection between the first intermediate chamber 38 and the first electronically controlled valve 42 is prevented.

[0030] According to a preferred embodiment, the valve assembly 48 comprises a valve body, comprising a cylindrical portion 49 (e.g., in the form of a cylindrical shell made of plastics or metal material) which is coupled to the first intermediate cylindrical tube 36 and comprises a first axial cavity 49a, in fluid connection with the first intermediate chamber 38, and a second annular cavity 49b, concentric and radially external to the first axial cavity 49a, this second annular cavity 49b being in fluid connection with the reservoir chamber 20.

[0031] The valve assembly 48 may further comprise a closure portion 50 (e.g., in the form of a shell or cylindrical cap made of plastics or metal material), coupled at one side to the first electronically controlled valve 42 and including a through cavity 50a in fluid connection with said electronically controlled valve 42, said closure portion 50 being coupled at the other side to the cylindrical portion 49 of the valve body, so as to identify within said valve body an intermediate chamber 50b in fluid connection with said through cavity 50a and with the first axial cavity 49a and the second annular cavity 49b of the cylindrical portion 49.

[0032] In such an embodiment, the valve assembly 48 further comprises an annular shutter 51 slidably accommodated (expediently, in the direction of the axis of the valve body) in the intermediate chamber 50b in a movable manner between a closed position, in which said annular shutter 51 is configured to prevent the fluid connection between said intermediate chamber 50b and the second annular cavity 49b of the cylindrical portion 49 (and to allow a passage of fluid from the first intermediate chamber 38 to the first electronically controlled valve 42 through the first axial cavity 49a of the cylindrical portion 49, the intermediate chamber 50b and the through cavity 50a of the closure portion 50, when the shock absorber 10 is in a rebound condition, as illustrated by way of example in Fig. 4), and an open position, wherein said annular shutter 51 is configured to allow fluid to pass from the reservoir chamber 20 to the first intermediate chamber 38 through the second annular cavity 49b, the intermediate chamber 50b and the first axial cavity 49a of the cylindrical portion 49, when the shock absorber 10 is in a compression condition (as illustrated by way of example in Fig. 5).

[0033] Preferably, the annular shutter 51 is pushed towards the closed position by elastic means 52, which may be arranged to abut against the closure portion 50, on the side opposite the side that engages the annular shutter 51.

[0034] The elastic means 52 preferably comprise one or more wave springs. These springs are known to be formed of corrugated washers, angularly offset from each other and axially overlapping so that the valleys of one washer are joined to the ridges of the underlying washer.

[0035] Preferably, the second annular cavity 49b of the cylindrical portion 49 is configured as an annular groove formed in the radial thickness of said cylindrical portion, between the radially outer surface of said cylindrical portion 49 and the relevant first axial cavity 49a. Expediently, the annular shutter 51 may be configured to abut, in the closed condition, against the open annular edge of the groove from which the second annular cavity 49b is formed, so as to occlude said open annular edge and create a barrier that prevents the fluid connection between the second annular cavity 49b and the intermediate chamber 50b and / or the first axial cavity 49a of the cylindrical portion 49.

[0036] The cylindrical portion 49 may comprise one or more radial holes 49c, adapted to put the second annular cavity 49b in fluid connection with the reservoir chamber 20.

[0037] Preferably, the radial holes 49c have respective axes parallel to the longitudinal axis x of the cylindrical body 12, and the first axial cavity 49a of the cylindrical portion 49 has an axis perpendicular to said longitudinal axis x. Preferably, the first intermediate cylindrical tube 36 and the second intermediate cylindrical tube 39 are axially separated and spaced apart from each other.

[0038] According to a preferred embodiment, the first electronic valve 42 is connected by a first way thereof to the through cavity 50a of the closure portion 50, and by a second way thereof to the reservoir chamber 20, so as to selectively prevent or allow the passage of fluid between said ways of the first electronic valve 42.

[0039] According to a preferred embodiment, the second electronic valve 44 is connected by a first way thereof to the second intermediate chamber 40, and by a second way thereof to the reservoir chamber 20, so as to selectively prevent or allow the passage of fluid between said ways of the second electronic valve 44.

[0040] By suitably controlling the second electronic valve 44, it is therefore possible to regulate the flow of oil from the compression chamber 26 to the reservoir chamber 20 and, in this way, to regulate the damping force exerted on the rod 14 during the compression phase.

[0041] The operation of the shock absorber 10 according to a preferred embodiment of the invention is as follows.

[0042] During the rebound (extension) phase of the shock absorber 10, as illustrated by way of example in Fig. 2 and 4, there is a flow of oil from the rebound chamber 24 to the first intermediate chamber 38, and from the first intermediate chamber 38 — through the valve assembly 48 and the first electronic valve 42 — to the reservoir chamber 20. The working fluid flows from the first intermediate chamber 38 through the first axial cavity 49a of the cylindrical portion 49 of the valve assembly 48, without acting on the annular shutter 51, which continues to prevent the fluid connection between the intermediate chamber 50b and the second annular cavity 49b of the cylindrical portion 49; thus, the fluid flows through the through cavity 50a of the closure portion 50 up to the first electronically controlled valve 42.

[0043] By suitably controlling the first electronic valve 42, it is therefore possible to regulate the flow of oil from the rebound chamber 26 to the reservoir chamber 20 and, in this way, to regulate the damping force exerted on the rod 14 during the extension phase.

[0044] During the compression phase of the shock absorber 10, as illustrated by way of example in Fig. 3 and 5, there is a flow of oil from the reservoir chamber 20 to the rebound chamber 24 through the valve assembly 48 — bypassing the first electronic valve 42. In particular, the working fluid flows from the reservoir chamber 20 through the second annular cavity 49b of the cylindrical portion 49, exerting a pressure on the annular shutter 51, which involves compression of the elastic means 52 until a fluid communication is opened between said second annular cavity 49b and the intermediate chamber 50b, from which the fluid may pass to the first axial cavity 49a of the cylindrical portion 49 of the valve assembly 48, and finally to the rebound chamber 24.

[0045] A hydraulic shock absorber with variable damping according to the invention has been described.

[0046] Naturally, without prejudice to the principle of the invention, the embodiments and the details of construction may be varied with respect to that which has been described and illustrated purely by way of non-limiting example, without thereby departing from the scope of the invention as defined by the accompanying claims.

Claims

CLAIMS1. A hydraulic shock absorber with variable damping (10), particularly 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 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 rebound chamber (24);- a first electronically controlled valve (42), arranged in such a way as to protrude radially outward from the outer cylindrical tube (18) and configured so as to put the first intermediate chamber (38) in fluid communication with the reservoir chamber (20), and to control the flow of damping fluid from one to the other;- a second intermediate cylindrical tube (39), arranged around the inner cylindrical tube (16) coaxially to the latter, said second intermediate cylindrical tube (39) delimiting together with the inner cylindrical tube (16) a second intermediate chamber (40), in fluid communication with the compression chamber (26);- a second electronically controlled valve (44), arranged in such a way as to protrude radially outward from the outer cylindrical tube (18) and configured to put the second intermediate chamber (40) in fluid communication with the reservoir chamber (20), and to control the flow of damping fluid from one to the other; characterized in that it comprises a valve assembly (48) located within the reservoir chamber (20) in an interposed position between the first intermediate cylindrical tube (36) and the first electronically controlled valve (42), said valve assembly (48) being configured in sucha way that- in a rebound condition of the shock absorber (10), a passage of fluid is allowed from the first intermediate chamber (38) to the first electronically controlled valve (42); and- in a compression condition of the shock absorber (10), a passage of fluid is allowed from the reservoir chamber (20) to the first intermediate chamber (38), and a fluid connection between the first intermediate chamber (38) and the first electronically controlled valve (42) is prevented.

2. A shock absorber according to claim 1, wherein the valve assembly (48) comprises:- a valve body, comprising a cylindrical portion (49), coupled to the first intermediate cylindrical tube (36) and comprising a first axial cavity (49a), in fluid connection with the first intermediate chamber (38), and a second annular cavity (49b), concentric and radially external to the first axial cavity (49a), said second annular cavity (49b) being in fluid connection with the reservoir chamber (20); and- a closure portion (50), coupled at one side to said first electronically controlled valve (42) and including a through cavity (50a) in fluid connection with said electronically controlled valve (42), and coupled at the other side to the cylindrical portion (49) of said valve body so as to identify within said valve body an intermediate chamber (50b) in fluid connection with said through cavity (50a) and with the first axial cavity (49a) and the second annular cavity (49b) of said cylindrical portion 49; the valve assembly (48) additionally comprising an annular shutter (51), which is slidably accommodated in the intermediate chamber (50b) in a movable manner between:- a closed position, in which said annular shutter (51) is configured to prevent a fluid connection between said intermediate chamber (50b) and said second annular cavity (49b) of said cylindrical portion (49) and to allow a passage of fluid from the first intermediate chamber (38) to the first electronically controlled valve (42) through the first axial cavity (49a) of the cylindrical portion (49), the intermediate chamber (50b) and the through cavity (50a) of the closure portion 50, when the shock absorber (10) is in a rebound condition; and- an open position, in which said annular shutter (51) is configured to allow fluid to pass from the reservoir chamber (20) to the first intermediate chamber (38) through the second annular cavity (49b), the intermediate chamber (50b) and the first axial cavity (49a) of the cylindrical portion (49), when the shock absorber (10) is in a compression condition.

3. Shock absorber according to claim 2, wherein the annular shutter (51) is pushed towards the closed position by elastic means (52).

4. A shock-absorber according to claim 3, wherein the elastic means (52) are arranged abutting against the closure portion (50), on the side opposite the side engaging the annular shutter (51).

5. A shock absorber according to claim 3 or 4, wherein the elastic means (52) comprise one or more wave springs.

6. A shock absorber according to any one of the preceding claims, wherein the second annular cavity (49b) of the cylindrical portion (49) is configured as an annular groove formed in the radial thickness thereof, between the radially outer surface of said cylindrical portion (49) and the relevant first axial cavity (49a).

7. A shock-absorber according to claim 6, wherein the cylindrical portion (49) comprises one or more radial holes (49c), adapted to put the second annular cavity (49b) in fluid communication with the reservoir chamber (20).

8. A shock absorber according to claim 7, wherein the radial holes (49c) have respective axes parallel to the longitudinal axis x of the cylindrical body (12), and the first axial cavity (49a) of the cylindrical portion (49) has an axis perpendicular to said longitudinal axis x.

9. A shock absorber according to any one of the preceding claims, wherein the first intermediate cylindrical tube (36) and the second intermediate cylindrical tube (39) are axially separated and spaced apart from each other.

10. A shock absorber according to any one of the preceding claims, wherein the first electronic valve (42) is connected by a first way thereof to the through cavity (50a) of the closure portion (50), and by a second way thereof to the reservoir chamber (20), so as to selectively prevent or allow the passage of fluid between said ways of the first electronicvalve (42).

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