Hydraulic shock absorber with two electronically controlled valves, particularly for vehicle suspension

Abstract

A hydraulic shock absorber (10) comprises a cylindrical body (12), including an inner cylindrical tube (16) and an outer cylindrical tube (18), which define a reservoir chamber (20) containing a damping fluid; a piston (22), slidably mounted in the inner cylindrical tube (16) to separate the internal volume of the latter into a rebound chamber (24) and a compression chamber (26); a pair of electronically controlled valves (42, 44), configured to put in fluid communication the rebound and compression chambers (24, 26) with the reservoir chamber (20); an auxiliary duct (46), designed to put in fluid communication the compression chamber (26) and the second electronically controlled valve (44), bypassing the reservoir chamber (20); and a valve assembly (48), mounted at the bottom of the inner cylindrical tube (16), and comprising at least a first and a second passageway (50, 52), configured to put in fluid communication the compression chamber (26) and the reservoir chamber (20) with the compression chamber (26) and the auxiliary duct (46), respectively.

Description

[0001] Hydraulic shock absorber with two electronically controlled valves, particularly for vehicle suspension

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

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

[0004] In such solutions, a first valve is designed to adjust the flow of the damping fluid of the shock absorber during the compression phase only, while the other valve is designed to adjust the flow of the damping fluid during the rebound phase only.

[0005] A shock absorber of this type is known, for instance, from DE 10 2005 053 394 Al.

[0006] According to these known solutions, the shock absorber includes an outer cylindrical tube, an inner cylindrical tube coaxial to the outer cylindrical tube and defining with it a reservoir chamber, a rod arranged coaxially to the two cylindrical tubes and partially protruding therefrom, and a piston slidably mounted in the inner cylindrical tube and fixed to the lower end of the rod. The piston separates the internal volume of the inner cylindrical tube into a rebound chamber and a compression chamber, both containing the damping fluid. The piston is equipped with a first valve assembly comprising a pair of one-way valves, and precisely a compensation valve, which adjust the flow of the damping fluid from the compression chamber to the rebound chamber during the compression phase, and a rebound valve, which adjust the flow of the damping fluid from the rebound chamber to the compression chamber during the rebound phase. 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 adjust the flow of the damping fluid from the compression chamber to the reservoir chamber during the compression phase, and an intake valve, which adjusts the flow of the damping fluid from the reservoir chamber to the compression chamber during the rebound phase. The one-way valves in both valve assemblies are implemented as passive valves. A shock absorber as known from DE 10 2005 053 394 Al also includes a first and a second electronically controlled valves designed to adjust the flow of a damping fluid during the rebound phase, and respectively during the compression phase. More specifically, the first electronically controlled valve is connected on one side to the reservoir chamber and on the other 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 designed to adjust, during the rebound phase, the flow of damping fluid from the rebound chamber to the reservoir chamber through the first intermediate chamber and thereby adjust the damping force of the shock absorber during this phase. The second electronically controlled valve is connected on one side to the reservoir chamber and on the other 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 designed to adjust, during the compression phase, the flow of the damping fluid from the compression chamber to the reservoir chamber through the second intermediate chamber and thereby adjust the damping force of the shock absorber during this phase.

[0007] The valve bodies of both electronically controlled valves of this known shock absorber are located outside the outer cylindrical tube in axially offset positions. As a result, the shock absorber exhibits a shape that is difficult to install in a vehicle, in particular in cases where the available space is limited, or when a symmetrical section is required.

[0008] The object of the present invention is to provide a variable damping hydraulic shock absorber that, while maintaining the advantages of using two electronically controlled valves in terms of adjustment range and efficiency of the damping characteristics, offers at the same time an i proved architecture .

[0009] This and other objects are achieved, according to the present invention, through a variable damping hydraul c shock absorber having the features defined in the appended independent claim 1 .

[0010] .Advantageous embodiments of the invention are specified in the dependent claims, whose content is considered as an integral part of the following description.

[0011] In essence, the invention is based on the idea of equipping the hydraulic shock absorber with a bypass duct, formed in the terminal section of the outer tube and designed to connect the compression chamber to one of the electronically controlled valves via a valve assembly, which preferably includes a wave spring.

[0012] Furthermore, thanks to the above solutions, the shock absorber can be conveniently configured so that the electronic valves are coaxial, which makes the shape of the shock absorber symmetrical, facilitating its installation on the vehicle.

[0013] Further features and advantages of the present invention will become clearer from the following detailed description, provided purely by way of non-limiting example with reference to the accompanying drawings, wherein:

[0014] - figure l is a schematic sectional view of the hydraulic shock absorber during a rebound phase, according to an embodiment of the invention;

[0015] - figure 2 is an enlargement of the terminal section of the shock absorber, in the configuration shown in Figure 1;

[0016] - figure 3 is a schematic sectional axial view of the hydraulic shock absorber in Figure 1 during a compression phase; and

[0017] - figure 4 is an enlargement of the terminal section of the shock absorber, in the configuration shown in Figure 3.

[0018] Detailed description

[0019] Before explaining in detail multiple embodiments of the invention, it should be clarified that the invention is not limited in its application to the construction details and the component configurations disclosed in the following description or illustrated in the drawings. The invention can adopt other embodiments and be implemented or carried out practically in various ways. It should also be understood that the phraseology and terminology have a descriptive purpose and should not be interpreted as limiting.

[0020] With reference to Figure 1, a hydraulic shock absorber with variable damping (hereinafter referred to simply as "shock absorber"), particularly designed for use in a vehicle suspension, is generally indicated by 10.

[0021] 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 (upward, from the observer's viewpoint of 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.

[0022] The body 12 comprises an inner cylindrical tube 16 and an outer cylindrical tube 18, which are arranged coaxially to each other and define a reservoir chamber 20 containing a damping fluid (typically oil, which will hereinafter be indicated simply as oil only).

[0023] 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 separates the internal volume of the inner cylindrical tube 16 into a rebound chamber 24 and a compression chamber 26, both containing the damping fluid (preferably oil).

[0024] The piston 22 may be provided with a first valve assembly comprising a pair of one-way valves, and precisely a compensation valve, which allows oil to flow only in the direction from the compression chamber 26 to the rebound chamber 24, and a rebound valve, which allows oil to flow only in the direction from the rebound chamber 24 to the compression chamber 26.

[0025] Around the inner cylindrical tube 16, and coaxially to it, a first intermediate cylindrical tube 36 is arranged, delimiting, together with the inner cylindrical tube 16, a first intermediate chamber 38 in fluid communication exclusively with the rebound chamber 24. Furthermore, a first electronically controlled valve 42 (hereinafter indicated as electronic valve) is configured to put in fluid communication the first intermediate chamber 38 and the reservoir chamber 20 and to control the flow of damping fluid between the two chambers, and a second electronically controlled valve 44, configured to put in fluid communication the compression chamber 26 and the reservoir chamber 20 and to control the flow of the damping fluid from one to the other. Both electronic valves 42, 44 are arranged to protrude radially outward from the outer cylindrical tube 18 and are preferably supported by it.

[0026] An auxiliary duct 46 is also present, designed to put in fluid communication the compression chamber 26 and the second electronically controlled valve 44, bypassing the reservoir chamber 20.

[0027] At the bottom of the inner cylindrical tube 16, a valve assembly 48 is moreover mounted, comprising at least a first passageway 50, designed to put in fluid communication the compression chamber 26 with the reservoir chamber 20, and a second passageway 52, designed to put in fluid communication the compression chamber 26 with the auxiliary duct 46.

[0028] This valve assembly 48 includes at least one valve 54, configured to allow a flow rate of damping fluid to pass from the reservoir chamber 20 to the compression chamber 26 through the first passageway 50, (inhibiting the fluid communication between the compression chamber 26 and the auxiliary duct 46 through the second passageway 52) when the shock absorber 10 is in a rebound condition (extension) and to allow a flow rate of damping fluid to pass from the compression chamber 26 to the auxiliary duct 46 through the second passageway 52 (inhibiting the fluid communication between the reservoir chamber 20 and the compression chamber 26 through the first passageway 50), when the shock absorber 10 is in a compression condition.

[0029] One or more one-way valves of the valve assembly 48, associated with the respective passageways 50, 52, are preferably implemented as passive valves.

[0030] According to a preferred embodiment, the at least one valve 54 of the valve assembly 48 comprises a wave spring. Said springs are typically formed by wave-shaped washers, angularly offset from one another and axially stacked so that the valleys of one washer align with the peaks of the underlying washer.

[0031] According to a preferred embodiment, the auxiliary duct 46 is at least partially provided in the radial thickness of a terminal section 19 of the outer cylindrical tube 18, opposite to the side of the shock absorber body 12 from which the rod 14 protrudes.

[0032] Said terminal section 19 of the outer cylindrical tube 18, opposite to the side of the shock absorber body 12 from which the rod 14 protrudes, may be configured as a cap fitted onto the end of the outer cylindrical tube 18, so as to delimit the reservoir chamber 20 together with the inner cylindrical tube 16.

[0033] The terminal section 19 of the outer cylindrical tube 18 may protrude radially outwards of at least part of the remaining outer cylindrical tube 18.

[0034] According to a preferred embodiment, the first and second electronically controlled valves 42, 44 are arranged in a mutually coaxial manner.

[0035] The shock absorber 10 may comprise a second intermediate cylindrical tube 39, axially coupled to the first intermediate cylindrical tube 36 and arranged around the inner cylindrical tube 16, coaxially to it, delimiting, together with the inner cylindrical tube 16, 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 susceptible of being placed in fluid communication with the first intermediate chamber 38.

[0036] According to a preferred embodiment, a one-way valve 41 is arranged between the first and second intermediate chambers 38, 40, designed to allow fluid passage from the second intermediate chamber 40 to the first intermediate chamber 38 when the shock absorber 10 is in a rebound condition. The one-way valve 41 may be configured, for example, as a deformable seal or a wave spring. According to a preferred embodiment, the first 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 fluid flow between said ways of the first electronically controlled valve 42.

[0037] According to a preferred embodiment, the second electronically controlled valve 44 is connected, with a first way thereof, to the auxiliary duct 46, and with a second way thereof, to the reservoir chamber 20 (e.g., via one or more openings 37, provided in the terminal section 19 of the outer cylindrical tube 18), so as to selectively inhibit or allow fluid flow between said ways of the second electronically controlled valve 44.

[0038] The operation of the shock absorber 10, according to one embodiment of the invention, is the following.

[0039] During the rebound phase (extension) of the shock absorber 10, as illustrated in Figure 1, oil flows 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 first electronically controlled valve 42- into the reservoir chamber 20, from which the fluid enters the compression chamber 26 through the first passageway(s) 50 of the valve assembly 48. According to one embodiment, the pressure difference between the reservoir chamber 20 and the compression chamber 26 causes axial compression of the wave spring 54, thereby opening the first passageway 50 and closing the second passageway 52, inhibiting the fluid communication between the compression chamber 26 and the auxiliary duct 46 (so that the second electronically controlled valve 44 is not fed).

[0040] By appropriately piloting the first electronically controlled valve 42, it is therefore possible to adjust the flow of oil from the rebound chamber 26 to the reservoir chamber 20, thereby adjusting the damping force exerted on the rod 14 during the extension phase.

[0041] During the compression phase of the shock absorber 10, as illustrated in Figure 3, the valve assembly 48 is configured to close the first passageway(s) 50, inhibiting the fluid communication between the compression chamber 26 and the reservoir chamber 20, while simultaneously opening the second passageway 52, putting in fluid communication the compression chamber 26 and the second electronically controlled valve 44 through the auxiliary duct 46 (e.g., due to the axial divergence of the possible wave spring 54 caused by the greater pressure exerted on said spring 54 by the fluid contained in the compression chamber 26 compared to the pressure of the fluid in the reservoir chamber 20 so that the spring 54 closes the first passageway(s) 50 and opens the second passageway 52).

[0042] By appropriately piloting the second electronically controlled valve 44, it is therefore possible to adjust the flow of oil from the compression chamber 26 to the reservoir chamber 20 and, thereby, adjust the damping force exerted on the rod 14 during the compression phase.

[0043] A hydraulic shock absorber with variable damping has been described, according to the invention.

[0044] Naturally, without departing from the principle of the invention, the embodiments and details of the embodiment may be modified from what has been described and illustrated purely by way of non-limiting example, without thereby departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS1. Hydraulic shock absorber with variable damping (10), particularly for use 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 rebound chamber (24) only;- a first electronically controlled valve (42), arranged so as to protrude radially outside 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 control the flow of the damping fluid from one to the other;- a second electronically controlled valve (44), arranged so as to protrude radially outside the outer cylindrical tube (18) and configured so as to put the compression chamber (26) in fluid communication with the reservoir chamber (20), and control the flow of the damping fluid from one to the other; wherein there is an auxiliary duct (46), designed to connect the compression chamber (26) with the second electronically controlled valve (44), bypassing the reservoir chamber (20); and wherein a valve assembly (48) is mounted at the bottom of the inner cylindrical tube (16) comprising at least a first passageway (50), designed to put the compression chamber (26) in fluid communication with the reservoir chamber (20), and a second passageway (52), adapted to put the compression chamber (26) in fluid communication with the auxiliary duct(46), said valve assembly (48) comprising at least one valve (54) configured to allow a flow rate of the damping fluid to flow from the reservoir chamber (20) to the compression chamber (26) through the first passageway (50), preventing a fluid communication between the compression chamber (26) with the auxiliary duct (46) through the second passageway (52) when the shock absorber (10) is in a rebound condition, and to allow a flow rate of the damping fluid to flow from the compression chamber (26) to the auxiliary duct (46) through the second passageway (52), preventing a fluid communication between the reservoir chamber (20) and the compression chamber (26) through the first passageway (50), when the shock absorber (10) is in a rebound condition.

2. Shock absorber according to claim 1, wherein the auxiliary duct (46) is made at least partially in the radial thickness of the end section (19) of the outer cylindrical tube (18), opposite to the side of the body (12) of the shock absorber from which the rod (14) protrudes.

3. Shock absorber according to claim 1 or 2, wherein the end section (19) of the outer cylindrical tube (18), opposite to the side of the body (12) of the shock absorber from which the rod (14) protrudes, is configured as a plug fitted onto the end of the outer cylindrical tube(18), so as to delimit the reservoir chamber (20) with the inner cylindrical tube (16).

4. Shock absorber according to any of the preceding claims, wherein the end section(19) of the outer cylindrical tube (18) radially protrudes outside of at least part of the remaining outer cylindrical tube (18).

5. Shock absorber according to any of the preceding claims, wherein the first and second electronically controlled valves (42), (44) are arranged in a mutually coaxial manner.

6. Shock absorber according to any one of the preceding claims, wherein the at least one valve (54) of the valve assembly (48) comprises a wave spring.

7. Shock absorber according to any of the preceding claims, 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 fluid communication with the rebound chamber (24) and / or the reservoir chamber (20), said second intermediate chamber (40) being adapted to be put in fluid communication with the first intermediate chamber (38).

8. Shock absorber according to claim 7, wherein a one-way valve (41) is interposed between the first and second intermediate chambers (36), (40), suitable for allowing a passage of fluid from the second intermediate chamber (40) to the first intermediate chamber (38) when the shock absorber (10) is in a rebound condition.

9. Shock absorber according to any of the preceding claims, wherein the first electronic 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 prevent or allow the passage of fluid between said ways of the first electronic valve (42).

10. Shock absorber according to any one of the preceding claims, wherein the second electronic valve (44) is connected with a first way thereof to the auxiliary duct (46), and with a second way thereof to the reservoir chamber (20), so as to selectively prevent or allow fluid passage between said ways of the second electronic valve (44).

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