SHOCK ABSORBERS

Abstract

A shock absorber (D) of the present invention comprises: a cylinder (1); a piston (2) movably inserted into the cylinder (1) and dividing an interior of the cylinder (1) into an extension-side chamber (R1) and a compression-side chamber (R2) filled with a fluid; a piston rod (3) inserted into the cylinder (1) and connected to the piston (2); an outer tube (4) arranged on an outer peripheral side of the cylinder (1) and forming a fluid storage chamber (R3) filled internally only with a fluid; a damping passage (P) allowing communication between the extension-side chamber (R1) and the fluid storage chamber (R3); a variable damping valve (V) provided in the damping passage (P) and capable of adjusting a resistance exerted on a flow of fluid from the extension-side chamber (R1) to the fluid storage chamber (R3);and a tank (6) arranged outside the outer tube (4) and communicating with the liquid storage chamber (R3) for storing a liquid;

Description

Technical area

[0001] The present invention relates to a shock absorber. State of the art

[0002] In some shock absorbers that apply damping force to suppress vibration, the damping force can be adjusted. For example, as such a shock absorber, a shock absorber in which damping force can be adjusted by using a solenoid valve as a damping valve is well known. Here, in a case where adjustment of the damping force can be performed both at the time of rebound operation and at the time of contraction operation, if both a damping valve that applies damping force at the time of rebound operation and a damping valve that applies damping force at the time of contraction operation are provided, the cost becomes high.

[0003] Therefore, a shock absorber has been developed which uses a structure in which a damping passage through which hydraulic oil flows even when the shock absorber is rebounding or contracting, a damping valve is installed in the damping passage, and the adjustment of the damping force can be performed both at the time of the rebounding operation and at the time of the contracting operation.

[0004] Specifically, as disclosed in JP 2014-231912 A, the shock absorber includes a cylinder; a piston slidably inserted into the cylinder; a piston rod movably inserted into the cylinder and connected to the piston; a rod-side chamber and a piston-side chamber separated from each other by the piston inserted into the cylinder; an intermediate tube covering an outer periphery of the cylinder and forming a damping passage between the cylinder and the intermediate tube; an outer tube covering an outer periphery of the intermediate tube and forming a reservoir between the intermediate tube and the outer tube; a suction passage allowing only hydraulic oil to flow from the reservoir to the piston-side chamber; a piston passage provided in the piston and allowing only hydraulic oil to flow from the piston-side chamber to the rod-side chamber.and a damping valve provided between the damping passage and the reservoir.; List of known publicationsPatent literature

[0005] Patent Literature 1: JP 2014-231912 A Brief description of the inventionTechnical problem

[0006] In a conventional shock absorber configured as described above, when the hydraulic oil that has passed through the damping valve forms a jet and violently flows into the reservoir, the jet swirls the hydraulic oil in the reservoir facing the gas, and the gas is entrained and mixed with the hydraulic oil in the reservoir, whereby a waveform (damping waveform) of a damping force generated with respect to the displacement of the shock absorber is disturbed, and it is difficult to exert an intended damping force.

[0007] Therefore, in the conventional shock absorber, it is necessary to increase the amount of oil in the reservoir to keep the oil level in the reservoir as far away as possible from the fluid outlet of the damping valve. Thus, the axial length of the outer tube forming the reservoir and the base length of the shock absorber become long. As described above, if the base length of the shock absorber becomes long, the mountability of the shock absorber on the mounting target deteriorates.

[0008] Therefore, an object of the present invention is to provide a shock absorber that can exert a desired damping force without impairing mountability on a mounting target. Solution to the problem

[0009] To achieve the above-mentioned object, a shock absorber of the present invention comprises: a cylinder; a piston movably inserted into the cylinder and dividing an interior of the cylinder into an extension-side chamber and a compression-side chamber filled with a fluid; a piston rod inserted into the cylinder and connected to the piston; an outer tube disposed on an outer peripheral side of the cylinder and forming a fluid storage chamber filled internally only with a fluid; a damping passage allowing communication between the extension-side chamber and the fluid storage chamber; a variable damping valve provided in the damping passage and capable of adjusting a resistance exerted on a flow of fluid from the extension-side chamber to the fluid storage chamber;and a tank disposed outside the outer tube and communicating with the liquid storage chamber for storing a liquid;

[0010] In the shock absorber configured as described above, since the tank is provided outside the outer tube, the liquid storage chamber can be filled only with the liquid, and even if the liquid flows into the liquid storage chamber through the variable damping valve during the operation of extension / contraction, a liquid can be prevented from entraining gas in the liquid storage chamber. Short description of the drawings Fig. 1 is a cross-sectional view of a shock absorber according to an embodiment. Fig. 2 is a graph of damping force characteristics of the shock absorber according to the embodiment. Fig. 3 is a cross-sectional view of a shock absorber according to a modification of the embodiment. Description of embodiments

[0011] Hereinafter, a shock absorber D according to the present invention will be described with reference to the drawings. As shown in Fig. 1, the shock absorber D according to one embodiment includes: a cylinder 1; a piston 2 movably inserted into the cylinder 1 and dividing an interior of the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2 filled with a fluid; a piston rod 3 inserted into the cylinder 1 and connected to the piston 2; an outer tube 4 disposed on an outer peripheral side of the cylinder 1 and forming a fluid storage chamber R3 filled internally only with a fluid; a damping passage P allowing communication between the extension-side chamber R1 and the fluid storage chamber R3; a variable damping valve V provided in the damping passage P and capable of adjusting a resistance exerted on a flow of fluid from the extension-side chamber R1 to the fluid storage chamber R3;and a tank 6 disposed outside the outer tube 4 and communicating with the liquid storage chamber R3 to store a liquid;

[0012] Each unit of the shock absorber D is described in more detail below. The cylinder 1 has a tubular shape, and the piston 2 is movably inserted into an interior of the cylinder 1 as described above, and the rebound-side chamber R1 is formed on an upper side of the piston 2 in Fig. 1, and the compression-side chamber R2 is on a lower side of the piston 2 in Fig. 1. The rebound-side chamber R1 and the compression-side chamber R2 are each filled with a fluid, in particular, for example, hydraulic oil. Instead of hydraulic oil, the rebound-side chamber R1 and the compression-side chamber R2 can also be filled with water or an aqueous solution as a fluid.

[0013] The cylinder 1 is housed in the outer tube 4, which has a bottomed tubular shape and is arranged on an outer peripheral side thereof. An intermediate tube 7 is inserted between the cylinder 1 and the outer tube 4, a damping passage P is formed through an annular gap between the cylinder 1 and the intermediate tube 7, and a fluid storage chamber R3 is formed through an annular gap between the intermediate tube 7 and the outer tube 4. Near an upper end of the cylinder 1, an opening 1a is provided, allowing communication between the rebound-side chamber R1 and the damping passage P. Further, the outer tube 4 covers an outer periphery of the cylinder 1 over the entire length of the cylinder 1, and the entire cylinder 1 is housed therein. The damping passage P and the fluid storage chamber R3 are filled with hydraulic oil, similar to the cylinder 1.

[0014] A valve housing 8 is mounted at the lower ends of the cylinder 1 and the intermediate pipe 7 in Fig. 1, and a rod guide 9, which supports the piston rod 3 slidingly and axially, is mounted on the upper ends of the cylinder 1 and the intermediate tube 7 in Fig. 1. The cylinder 1 and the intermediate tube 7 are clamped between the valve housing 8 and the rod guide 9 and positioned so that they are concentric in the radial direction. Both the lower end of the cylinder 1 and the lower end of the intermediate tube 7 are closed by the valve housing 8, and the compression-side chamber R2 in the cylinder 1 and the fluid storage chamber R3 located outside the cylinder 1 and formed in the outer tube 4 are partitioned by the valve housing 8.

[0015] In this way, the valve housing 8 and the rod guide 9, which clamp the cylinder 1 and the intermediate pipe 7, are inserted into an inner periphery of the outer pipe 4. When an upper end of the outer pipe 4 is caulked, the cylinder 1, the intermediate pipe 7, the valve housing 8, and the rod guide 9 are clamped between the caulked portion and the bottom portion of the outer pipe 4 and fixed in the outer pipe 4. A sealing member (not shown) seals between the rod guide 9 and the piston rod 3 and between the rod guide 9 and the outer pipe 4 to prevent fluid leakage from the inside of the shock absorber D.Instead of caulking an upper end of the opening end of the outer tube 4, a cap may be screwed to the upper edge of the opening end of the outer tube 4, and the rod guide 9, the cylinder 1, the intermediate tube 7, and the valve body 8 may be clamped between the cap and the bottom portion of the outer tube 4, thereby fixing these members in the outer tube 4.

[0016] The piston 2 has an annular shape and is connected to the piston rod 3 and comprises a rebound-side channel 2a which leads the interior of the cylinder 1 into a rebound-side chamber R1 in the upper part of Fig. 1 and a compression-side chamber R2 in the lower part of Fig. 1, and allows communication between the rebound-side chamber R1 and the compression-side chamber R2, and a compression-side channel 2b, which allows communication between the compression-side chamber R2 and the rebound-side chamber R1.

[0017] A compression-side check valve 12 formed by stacking a plurality of annular plates is provided on the side of the rebound-side chamber located in Fig. 1 forms an upper side of the piston 2. In the compression-side check valve 12, an inner periphery thereof is fixed to an outer periphery of the piston rod 3, and deflection on the outer periphery side is permitted. When a pressure of the compression-side chamber R2 becomes higher than a pressure of the rebound-side chamber R1 and the compression-side check valve 12 is deflected by receiving the pressure of the compression-side chamber R2 acting via the compression-side passage 2b, the compression-side check valve 12 opens the compression-side passage 2b to allow communication between the compression-side chamber R2 and the rebound-side chamber R1, thereby allowing the flow of hydraulic oil from the compression-side chamber R2 to the rebound-side chamber R1.

[0018] On the other hand, when the pressure of the rebound-side chamber R1 is higher than the pressure of the compression-side chamber R2, the compression-side check valve 12 is pushed by the pressure of the rebound-side chamber R1 acting from a rear side to close the compression-side passage 2b, thereby blocking the communication between the compression-side chamber R2 and the rebound-side chamber R1. The compression-side check valve 12 can exert resistance on the flow of hydraulic oil flowing in a state where the compression-side passage 2b is opened so much that the pressure in the rebound-side chamber R1 does not become negative.

[0019] On the other hand, an extension-side damping valve 13 formed by stacking a plurality of annular plates is provided on the side of the compression-side chamber located in Fig. 1 forms the lower side of the piston 2. In the rebound-side damping valve 13, an inner periphery thereof is fixed to the outer periphery of the piston rod 3, deflection on the outer periphery side is allowed, and initial deflection is applied. An orifice 13a formed by a notch is provided on the outer periphery of the annular plate of the rebound-side damping valve 13, the annular plate being seated on and separated from the piston 2. The rebound-side damping valve 13 maintains the state of being seated on the piston 2 until a difference between the pressure of the rebound-side chamber R1 and the pressure of the compression-side chamber R2 reaches a valve opening pressure determined by the initial deflection, even if the pressure of the rebound-side chamber R1 becomes higher than the pressure of the compression-side chamber R2.Therefore, in this state, the hydraulic oil moves only via the opening 13a from the extension-side chamber R1 to the compression-side chamber R2, and the opening 13a exerts resistance on the flow of the hydraulic oil.When the pressure of the rebound-side chamber R1 becomes higher than the pressure of the compression-side chamber R2 and the difference between the pressure of the rebound-side chamber R1 and the pressure of the compression-side chamber R2 reaches the valve opening pressure, the rebound-side damping valve 13 is deflected by receiving the pressure of the rebound-side chamber R1 acting via the rebound-side passage 2a to open the rebound-side passage 2a and allows communication between the rebound-side chamber R1 and the compression-side chamber R2, thereby allowing the flow of the hydraulic oil from the rebound-side chamber R1 to the compression-side chamber R2 and exerting resistance on the flow of the hydraulic oil.On the other hand, when the pressure of the compression-side chamber R2 is higher than the pressure of the rebound-side chamber R1, the rebound-side damping valve 13 is pushed by the pressure of the compression-side chamber R2 acting from a rear side to close the rebound-side passage 2a, thereby allowing communication between the rebound-side chamber R1 and the compression-side chamber R2 only via the orifice 13a.

[0020] Then, as in Fig. 1, the valve body 8 comprises: a small diameter portion 8a having an annular shape and a small diameter to be fitted at the lower end of the cylinder 1; a medium diameter portion 8b arranged below the small diameter portion 8a in Fig. 1, has a larger outer diameter than the small diameter portion 8a and is fitted at the lower end of the intermediate pipe 7; an annular skirt 8c arranged below the intermediate diameter portion 8b and has a larger outer diameter than the intermediate diameter portion 8b; a notch 8d provided in the skirt 8c and allowing communication between the inside and the outside of the skirt 8c; and a damping channel 8e and a suction channel 8f leading from one end of the compression-side chamber which is in Fig. 1 forms an upper end and faces the compression-side chamber R2, communicate with an opposite end of the compression-side chamber facing the interior of the skirt 8c.

[0021] The valve body 8 is fixed to the outer tube 4 by being clamped between the outer tube 4 and the cylinder 1, with the small diameter portion 8a at the lower end of the cylinder 1 in Fig. 1, the section 8b with medium diameter at the lower end of the intermediate pipe 7 in Fig. 1, and the lower end of the skirt 8c abuts the bottom portion of the outer tube 4. The interior of the skirt 8c communicates with the fluid storage chamber R3 via the notch 8d and communicates with the compression-side chamber R2 via the damping channel 8e and the suction channel 8f. Therefore, the compression-side chamber R2 and the fluid storage chamber R3 communicate with each other via the notch 8d, the interior of the skirt 8c, the damping channel 8e, and the suction channel 8f.

[0022] An extension-side check valve 14 formed by stacking a plurality of annular plates is provided on the side of the compression-side chamber located in Fig. 1 forms the upper side of the valve housing 8. In the extension-side check valve 14, an inner periphery thereof is fixed to an outer periphery of a center rod 15 inserted into an inner periphery of the valve housing 8, and deflection on the outer periphery side is permitted. When the pressure of the fluid storage chamber R3 becomes higher than the pressure of the compression-side chamber R2, the extension-side check valve 14 is deflected by receiving the pressure of the fluid storage chamber R3 acting via the suction passage 8f to open the suction passage 8f, thereby allowing the flow of hydraulic oil from the fluid storage chamber R3 to the compression-side chamber R2.On the other hand, when the pressure of the compression-side chamber R2 is higher than the pressure of the fluid storage chamber R3, the rebound-side check valve 14 is pushed by the pressure of the compression-side chamber R2 acting from the rear to close the suction passage 8f, thereby blocking the communication between the compression-side chamber R2 and the fluid storage chamber R3. The rebound-side check valve 14 can exert resistance on the flow of hydraulic oil flowing in a state where the suction passage 8f is opened so much that the pressure in the cylinder 1 does not become negative.

[0023] On the other hand, a compression-side damping valve 13 formed by stacking a plurality of annular plates is provided on the opposite side of the compression-side chamber located in Fig. 1 forms the lower side of the valve housing 8. In the compression-side damping valve 16, an inner periphery thereof is fixed to the outer periphery of the center rod 15, deflection on the outer periphery side is allowed, and initial deflection is applied. An orifice 16a formed by a notch is provided on the outer periphery of the annular plate of the compression-side damping valve 16, which is seated on and separated from the valve housing 8. The compression-side damping valve 16 maintains the state of being seated on the valve housing 8 until a difference between the pressure of the compression-side chamber R2 and the pressure of the liquid storage chamber R3 reaches a valve opening pressure determined by the initial deflection, even if the pressure of the compression-side chamber R2 becomes higher than the pressure of the liquid storage chamber R3.Therefore, in this state, the hydraulic oil moves only via the opening 16a from the compression-side chamber R2 to the liquid storage chamber R3, and the opening 16a exerts resistance on the flow of the hydraulic oil.In addition, when the pressure of the compression-side chamber R2 becomes higher than the pressure of the fluid storage chamber R3 and the difference between the pressure of the compression-side chamber R2 and the pressure of the fluid storage chamber R3 reaches a valve opening pressure, the compression-side damping valve 16 is deflected by receiving the pressure of the compression-side chamber R2 acting via the damping passage 8e to open the damping passage 8e and allows communication between the compression-side chamber R2 and the fluid storage chamber R3, thereby allowing the flow of the hydraulic oil from the compression-side chamber R2 to the fluid storage chamber R3 and exerting resistance on the flow of the hydraulic oil.On the other hand, when the pressure of the fluid storage chamber R3 is higher than the pressure of the compression-side chamber R2, the compression-side damping valve 16 is pushed by the pressure of the fluid storage chamber R3 acting from the rear to close the damping passage 8e, thereby allowing communication between the compression-side chamber R2 and the fluid storage chamber R3 only via the opening 16a.

[0024] As described above, the intermediate pipe 7 covers the outer periphery of the cylinder 1 and is clamped between the rod guide 9 and the valve housing 8, forming the annular damping passage P between the intermediate pipe 7 and the cylinder 1. The damping passage P communicates with the rebound-side chamber R1 via an orifice 1a provided in the cylinder 1 and communicates with the fluid storage chamber R3 via the variable damping valve V. The intermediate pipe 7 separates the cylinder 1 and the outer pipe 4 and forms the annular fluid storage chamber R3 between the intermediate pipe 7 and the outer pipe 4.

[0025] The intermediate pipe 7 includes an opening 7a at the bottom and a bushing 7b surrounding the opening 7a on the outer periphery and projecting in the radial direction. A valve housing 17 housing the variable damping valve V is fitted into the bushing 7b. The bushing 7b and the valve housing 17 are sealed by a sealing member (not shown), and the damping passage P and the fluid storage chamber R3 are prevented from communicating with each other via the valve housing 17 and the bushing 7b.Although the opening 1a provided in the cylinder 1 is used when the damping passage P in the intermediate pipe 7 communicates with the rebound-side chamber R1, a passage may be provided in the rod guide 9 instead of the opening 1a, which allows communication between the rebound-side chamber R1 and the annular gap between the cylinder 1 and the intermediate pipe 7 to allow communication between the damping passage P and the rebound-side chamber R1.

[0026] The outer tube 4 includes an opening 4a provided at a position radially facing the opening 7a and the bushing 7b of the intermediate tube 7, and a valve fixing tube 4b surrounding the opening 4a on the outer periphery and projecting in the radial direction. The valve housing 17 is fitted into the valve fixing tube 4b, and an opening edge of the valve fixing tube 4b is closed by a cap 19 having a bottomed tubular shape and screwed to the outer periphery of the valve fixing tube 4b. A sealing member (not shown) is provided between the valve housing 17 and the valve fixing tube 4b to prevent the hydraulic oil in the fluid storage chamber R3 from leaking out of the outer tube 4 between the valve housing 17 and the valve fixing tube 4b.

[0027] The valve housing 17 has a distal end inserted into the bushing 7b of the intermediate tube 7 and a rear end inserted into the valve mounting tube 4b of the outer tube 4, with the distal end facing the damping passage P and a lateral portion facing the fluid storage chamber R3. The valve housing 17 includes a flow path 18 opening from the distal end, communicating in the lateral direction, and allowing communication between the damping passage P in the intermediate tube 7 and the fluid storage chamber R3 in the outer tube 4, and the variable damping valve V installed in the center of the flow path 18.The flow path 18 in the valve housing 17 allows communication between the annular gap formed between the intermediate pipe 7 and the outer pipe 4 and communicating with the rebound-side chamber R1 and the liquid storage chamber R3, and forms the damping passage P together with the annular gap. Therefore, the variable damping valve V is provided in the center of the damping passage P.

[0028] The variable damping valve V allows the flow of hydraulic oil from the rebound-side chamber R1 to the fluid storage chamber R3 only through the damping passage P and provides resistance to the flow of hydraulic oil flowing through the damping passage P. Specifically, the variable damping valve V, which is a solenoid-equipped solenoid valve, is configured to provide resistance to the hydraulic oil flowing through the damping passage P from the rebound-side chamber R1 to the fluid storage chamber R3 and adjusts a valve opening pressure by means of a current applied to the solenoid. The variable damping valve V, configured as described above, acts as a pressure control valve that adjusts a valve opening pressure according to the current amount to the solenoid and can adjust a damping force generated by the shock absorber.In addition to the damping valve that makes the damping force variable by adjusting the valve opening pressure, a damping valve having any configuration as long as it can adjust a damping force can be used for the variable damping valve V.

[0029] Then, the tank 6 is provided outside the outer tube 4 and includes a tubular container 6a and a free piston 6b movably inserted into the container 6a and dividing an interior of the container 6a into a liquid chamber L filled with hydraulic oil and a gas chamber G filled with gas. The gas is enclosed in a compressed state in the gas chamber G, and the interior of the liquid chamber L in the tank 6 is pressurized by the pressure of the gas chamber G. The liquid chamber L of the tank 6 and the liquid storage chamber R3 in the outer tube 4 communicate with each other via a pipe 5, and the hydraulic oil can reciprocate between the liquid chamber L and the liquid storage chamber R3.

[0030] The piping 5 is formed of a flexible hose, one end of which is connected to a lower end of the container 6a and the other end of which is connected to an outer periphery of the outer tube 4 at a position not interfering with the valve housing 17. The piping 5 may be formed of a material that has no flexibility, such as a steel pipe, in addition to the flexible hose. Note that the liquid chamber L and the gas chamber G in the tank 6 are separated from each other by the free piston 6b, but may also be separated from each other by a partition member such as a bladder, a diaphragm, or a bellows, which can separate the liquid chamber L and the gas chamber G from each other and change the distribution of a volume of the liquid chamber L and a volume of the gas chamber G in the container 6a.In addition, for example, a partition member that separates the liquid chamber L and the gas chamber G from each other may be omitted as long as the gas can be prevented from moving from the container 6a in the tank 6 to the liquid storage chamber R3 by disposing a connecting portion to the piping 5 of the container 6a on the lower side. Further, a structure may be adopted in which one end of the container 6a is opened to the atmosphere, and a spring for biasing the free piston 6b in the direction of pressurizing the liquid chamber L is housed in the container 6a. In this case, the gas chamber G in which gas is sealed may not be provided in the container 6a.

[0031] The other end of the pipe 5 only needs to be connected to a position separate from the valve body 17 and does not interfere with the valve body, as long as it is a lateral portion of the outer pipe 4, and can therefore be connected to any portion over the entire elongated range in the axial direction of the outer pipe 4. The other end of the pipe 5 may be connected to the rod guide 9, and the rod guide 9 may be provided with a passage to allow communication between the interior of the pipe 5 and the liquid storage chamber R3.

[0032] The following describes the operation of the shock absorber D configured as described above. First, a case is described where the shock absorber D rebounds. When the piston 2 is in Fig. 1 moves upward with respect to the cylinder 1 and the shock absorber D is in an extension stroke, the rebound-side chamber R1 is compressed and the compression-side chamber R2 is enlarged. When the piston speed, which is the moving speed of the piston 2 with respect to the cylinder 1, is low, the pressure in the rebound-side chamber R1 becomes higher than the pressure in the compression-side chamber R2, but a differential pressure between the two chambers does not reach the valve opening pressure of the rebound-side damping valve 13. Therefore, since the rebound-side damping valve 13 maintains a closed valve state, the hydraulic oil moves from the rebound-side chamber R1 to the compression-side chamber R2 through the orifice 13a.

[0033] Here, when the valve opening pressure of the variable damping valve V is made lower than the valve opening pressure of the rebound-side damping valve 13, the variable damping valve V opens at a piston speed lower than the piston speed at which the rebound-side damping valve 13 opens, so that the hydraulic oil moves from the rebound-side chamber R1 to the fluid storage chamber R3 through the damping passage P in addition to the orifice 13a. When the valve opening pressure of the variable damping valve V is made higher than the valve opening pressure of the rebound-side damping valve 13, the variable damping valve V remains closed, so that the hydraulic oil moves from the rebound-side chamber R1 to the compression-side chamber R2 only through the orifice 13a.

[0034] If the piston speed during the extension stroke is in a high speed range, as in Fig. 2, the shock absorber D can adjust the damping force within a range of one damping force (dashed line in Fig. 2), where the valve opening pressure of the variable damping valve V is set to a minimum value, up to a damping force (solid line in Fig. 2) which is only created by the opening 13a.

[0035] Since the piston rod 3 moves out from the inside of the cylinder 1 during the extension stroke of the shock absorber D, an amount of hydraulic oil corresponding to the volume of the piston rod 3 moving out of the cylinder 1 is insufficient in the cylinder 1. The extension-side check valve 14 is opened to supply the hydraulic oil corresponding to the insufficient volume in the cylinder 1 from the liquid chamber L of the tank 6 to the cylinder 1 via the liquid storage chamber R3 and the pipe 5. As the hydraulic oil in the tank 6 is discharged from the liquid chamber L, the free piston 6b moves in the reservoir 6a, thereby reducing the volume of the liquid chamber L while increasing the volume of the gas chamber G. As described above, during the extension stroke of the shock absorber D, the hydraulic oil is supplied from the tank 6 to the cylinder 1 to compensate for the volume of the piston rod 3 that has moved out from the inside of the cylinder 1.

[0036] As the piston speed increases during the extension stroke, the differential pressure between the rebound-side chamber R1 and the compression-side chamber R2 increases. The pressure in the rebound-side chamber R1 can be controlled by adjusting the valve opening pressure of the variable damping valve V until the differential pressure between the rebound-side chamber R1 and the compression-side chamber R2 reaches the valve opening pressure of the rebound-side damping valve 13. When the differential pressure between the rebound-side chamber R1 and the compression-side chamber R2 reaches the valve opening pressure of the rebound-side damping valve 13, the rebound-side damping valve 13 is opened to open the rebound-side passage 2a.Then, the hydraulic oil flows through the annular gap formed between the rebound-side damping valve 13 and the piston 2 and moves from the rebound-side chamber R1 to the compression-side chamber R2.

[0037] If the piston speed during the extension stroke is in a high speed range, as in Fig. 2, the shock absorber D can adjust the damping force within a range of the damping force (dashed line in Fig. 2), where the valve opening pressure of the variable damping valve V is set to the minimum value, up to the damping force (solid line in Fig. 2) which is generated by the rebound side damping valve 13.

[0038] In addition, when the variable damping valve V is opened during the extension stroke, the hydraulic oil flows through the damping passage P and the variable damping valve V and flows out of the rebound-side chamber R1 to the liquid storage chamber R3, but the interior of the liquid storage chamber R3 is filled only with the hydraulic oil, and the hydraulic oil having a high flow rate and having passed through the variable damping valve V does not come into contact with the gas in the liquid storage chamber R3 at all, so that the gas can be prevented from being entrained. In the shock absorber D of the present embodiment, the interior of the container 6a of the tank 6 is divided into the liquid chamber L and the gas chamber G by the free piston 6b. Therefore, no problem occurs because the hydraulic oil itself in the tank 6 does not come into direct contact with the gas even when the hydraulic oil flows into the tank 6.However, even if the free piston 6b and other separating members that separate the gas and the hydraulic oil are omitted, and even if the hydraulic oil that has passed through the variable damping valve V flows to the liquid chamber L in the tank 6, the flow becomes smooth when passing through the piping 5, so that the hydraulic oil can be prevented from entraining the gas in the tank 6.

[0039] Next, a case is described where the shock absorber D contracts. When the piston 2 is in Fig. 1 moves downward relative to the cylinder 1 and the shock absorber D is in a retraction stroke, the compression-side chamber R2 is compressed and the rebound-side chamber R1 is enlarged. When the piston speed is low, the pressure of the compression-side chamber R2 becomes higher than the pressure of the rebound-side chamber R1. Then, the compression-side check valve 12 is opened, and the hydraulic oil moves from the compression-side chamber R2 to the rebound-side chamber R1.

[0040] In addition, since the piston rod 3 is inserted into the cylinder 1 during the retraction stroke of the shock absorber D, the amount of hydraulic oil corresponding to the volume of the piston rod 3 inserted into the cylinder 1 becomes excessive in the cylinder 1. When the piston speed is low, the differential pressure between the compression-side chamber R2 and the fluid storage chamber R3 is small, and thus the compression-side damping valve 16 maintains the closed state of the valve, so that the hydraulic oil moves from the compression-side chamber R2 through the orifice 16a to the fluid storage chamber R3.

[0041] Here, when the valve opening pressure of the variable damping valve V is made lower than the valve opening pressure of the compression-side damping valve 16, the variable damping valve V opens at a piston speed lower than the piston speed at which the compression-side damping valve 16 opens, so that the hydraulic oil moves from the inside of the cylinder 1 to the fluid storage chamber R3 through the damping passage P in addition to the orifice 16a. When the valve opening pressure of the variable damping valve V is made higher than the valve opening pressure of the compression-side damping valve 16, the variable damping valve V remains closed, so that the hydraulic oil moves from the compression-side chamber R2 to the fluid storage chamber R3 only through the orifice 16a.

[0042] If the piston speed during the retraction stroke is in the low speed range as in Fig. 2, the shock absorber D can adjust the damping force within a range of the damping force (dashed line in Fig. 2), where the valve opening pressure of the variable damping valve V is set to the minimum value, up to a damping force (solid line in Fig. 2) which is only created by the opening 16a.

[0043] As the piston speed increases during the retraction stroke, the differential pressure between the compression-side chamber R2 and the fluid storage chamber R3 increases. When the differential pressure between the compression-side chamber R2 and the fluid storage chamber R3 reaches the valve opening pressure of the compression-side damping valve 16, the compression-side damping valve 16 opens the damping channel 8e. Until the differential pressure between the compression-side chamber R2 and the fluid storage chamber R3 reaches the valve opening pressure of the compression-side damping valve 16, the pressure in the cylinder 1 can be controlled by adjusting the valve opening pressure of the variable damping valve V.

[0044] If the piston speed during the retraction stroke is in the high speed range as in Fig. 2, the shock absorber D can adjust the damping force within a range of the damping force (dashed line in Fig. 2), where the valve opening pressure of the variable damping valve V is set to the minimum value, up to the damping force (solid line in Fig. 2) which is generated by the compression-side damping valve 16.

[0045] In addition, when the variable damping valve V is opened during the retraction stroke, the hydraulic oil flows through the damping passage P and the variable damping valve V and flows out of the rebound-side chamber R1 to the liquid storage chamber R3, but the interior of the liquid storage chamber R3 is filled only with the hydraulic oil, and the hydraulic oil having a high flow rate that has passed through the variable damping valve V does not come into contact with the gas in the liquid storage chamber R3 at all, so that the gas can be prevented from being entrained. In the shock absorber D of the present embodiment, the interior of the container 6a of the tank 6 is divided into the liquid chamber L and the gas chamber G by the free piston 6b. Therefore, no problem occurs because the hydraulic oil itself in the tank 6 does not come into direct contact with the gas even when the hydraulic oil flows into the tank 6.However, even if the free piston 6b and other separating members that separate the gas and the hydraulic oil are omitted, and even if the hydraulic oil that has passed through the variable damping valve V flows to the liquid chamber L in the tank 6, the flow becomes smooth when passing through the piping 5, so that the hydraulic oil can be prevented from entraining the gas in the tank 6.

[0046] As can be seen from the above description, the shock absorber D behaves essentially like a direct-flow type shock absorber in which hydraulic oil flows from the interior of the cylinder 1 to the fluid storage chamber R3 via the variable damping valve VV, regardless of whether the shock absorber D1 is extending or contracting. When the pressure in the extension-side chamber R1 becomes too high, the extension-side damping valve 13 acts as a relief valve to move the hydraulic oil from the extension-side chamber R1 to the compression-side chamber R2, and when the pressure in the compression-side chamber R2 becomes too high, the compression-side damping valve 16 acts as a relief valve to move the hydraulic oil from the compression-side chamber R2 to the fluid storage chamber R3.

[0047] As described above, the shock absorber D includes the cylinder 1; the piston 2 movably inserted into the cylinder 1 and dividing the interior of the cylinder 1 into the rebound-side chamber R1 and the compression-side chamber R2 filled with hydraulic oil (fluid); the piston rod 3 inserted into the cylinder 1 and connected to the piston 2; the outer tube 4 disposed on the outer peripheral side of the cylinder 1 and forming a fluid storage chamber R3 filled internally only with hydraulic oil (fluid); the damping passage P allowing communication between the rebound-side chamber R1 and the fluid storage chamber R3; the variable damping valve V provided in the damping passage P and capable of adjusting a resistance exerted on a flow of hydraulic oil (fluid) from the rebound-side chamber R1 to the fluid storage chamber R3;and the tank 6, which is arranged outside the outer tube 4 and communicates with the liquid storage chamber R3 via the piping 5 to store hydraulic oil (liquid);

[0048] In the shock absorber D configured as described above, since the tank 6 is provided outside the outer tube 4, the interior of the fluid storage chamber R3 can be filled only with the hydraulic oil (liquid), and even if the hydraulic oil (liquid) flows into the fluid storage chamber R3 through the variable damping valve V during the extension / contraction operation, the hydraulic oil (liquid) can be prevented from entraining the gas in the fluid storage chamber R3. Even if the interior of the tank 6 is not divided into the gas and the liquid by the partition member, since the fluid storage chamber R3 communicates with the tank 6 via the piping 5, the flow rate of the hydraulic oil (liquid) is reduced, so that the gas can also be prevented from being entrained into the hydraulic oil (liquid) in the tank 6.

[0049] Therefore, according to the shock absorber D of the present embodiment, since there is no fear of gas entrainment in the liquid storage chamber R3, the entire length of the outer tube 4 can be shortened. This not only shortens the base length of the shock absorber D and does not affect the mountability at the mounting destination, but also prevents gas entrainment into the hydraulic oil (liquid), so that the gas can be prevented from mixing into the cylinder 1, and the intended damping force can be exerted.

[0050] In the shock absorber D of the present embodiment, since only the hydraulic oil (liquid) is filled in the liquid storage chamber R3 in the outer tube 4, the shock absorber main body including the cylinder 1, the piston 2, the piston rod 3, and the outer tube 4 can be used in an inverted arrangement with the cylinder 1 facing upward and the piston rod 3 facing downward, or in a horizontal arrangement, and the shock absorber main body can be installed according to the specification of the installation position of the shock absorber D, so that the mountability of the shock absorber D is also improved in this respect.

[0051] In the shock absorber D of the present embodiment, since the interior of the fluid storage chamber R3 is filled only with the hydraulic oil (fluid), the gas can be prevented from being entrained in the hydraulic oil (fluid) regardless of where the variable damping valve V is installed in the outer tube 4. Therefore, according to the shock absorber D of the present embodiment, a degree of freedom in designing the shock absorber D is improved because the installation position of the variable damping valve V with respect to the outer tube 4 can be freely determined. The variable damping valve V can be installed in the rod guide 9 or the valve housing 8 in addition to the outer tube 4.

[0052] Furthermore, in the shock absorber D of the present embodiment, the outer tube 4 covers the cylinder 1 over the entire length in the axial direction. According to the shock absorber D configured as described above, since the outer tube 4 covers the entire length of the cylinder 1, the installation position of the variable damping valve V with respect to the outer tube 4 can be set to any position within the range of the entire length of the outer tube 4 in the axial direction, thereby improving a degree of freedom in designing the installation position of the variable damping valve V.

[0053] In the shock absorber D of the present embodiment, the intermediate tube 7 is provided, which is arranged between the cylinder 1 and the outer tube 4 and forms the damping passage P between the intermediate tube 7 and the cylinder 1, and the liquid storage chamber R3 is formed between the intermediate tube 7 and the outer tube 4. According to the shock absorber D configured as described above, since the damping passage P and the liquid storage chamber R3 can be easily formed by installing the intermediate tube 7 between the cylinder 1 and the outer tube 4 with a simple structure, the manufacturing cost can be reduced and the assembly work can be facilitated.When forming the damping passage P, the intermediate pipe 7 may be omitted, and a piping may be provided, one end of which is attached to the rod guide 9 and accommodated between the cylinder 1 and the outer pipe 4, the inside of which may communicate with the rebound-side chamber R1 through the passage provided in the rod guide 9, and the other end of which may communicate with the liquid storage chamber R3 formed by the annular gap between the cylinder 1 and the outer pipe 4, to form the damping passage P through the piping. The variable damping valve V may be provided in the middle of the piping.

[0054] Furthermore, the intermediate pipe 7 may be omitted, the rebound-side chamber R1 may communicate with the fluid storage chamber R3 formed by the annular gap between the cylinder 1 and the outer pipe 4 through the passage provided in the rod guide 9, and the variable damping valve V may be incorporated in the rod guide 9. In this case, since the intermediate pipe 7 and the piping are not required, the number of parts of the shock absorber D can be reduced.

[0055] Further, in the shock absorber D of the present embodiment, the outer tube 4 covers the cylinder 1 and the intermediate tube 7 over the entire length in the axial direction, but the axial length of the outer tube 4 may be shorter than those of the cylinder 1 and the intermediate tube 7, under the condition that the liquid storage chamber R3 can be formed so that the hydraulic oil (liquid) can be prevented from entraining the gas in the outer tube 4, and that the variable damping valve V is accommodated in the region of the entire length in the axial direction of the outer tube 4.

[0056] When the connection position of the piping 5 to the outer pipe 4 or the rod guide 9 is set in a position separated from the installation position of the variable damping valve V in the circumferential direction and the vertical direction, the hydraulic oil having a high flow rate that has passed through the variable damping valve V and flowed from the inside of the cylinder 1 into the liquid storage chamber R3 can be prevented from flowing into the tank 6, and it is possible to smoothly send the hydraulic oil that is insufficient inside the cylinder 1 from the inside of the tank 6 at the time of the rebound operation of the shock absorber D, and it is expected that a more stable damping force occurs.

[0057] In the above description, the compression-side check valve 12 and the rebound-side damping valve 13 are provided in the piston 2, and the rebound-side check valve 14 and the compression-side damping valve 16 are provided in the valve housing 8. However, the shock absorber D may be a direct-flow type shock absorber in which the piston 2 includes only the compression-side passage 2b and the compression-side check valve 12, the valve housing 8 includes only the suction passage 8f and the rebound-side check valve 14, and a damping force is generated only by the variable damping valve V.

[0058] Furthermore, in the above-described shock absorber D, the tank 6 and the liquid storage chamber R3 are communicated with each other via the pipe 5. However, in a case where the container 6a forming the tank 6 is integrally formed in the outer tube 4, as in a shock absorber D1 in a Fig.3, the piping 5 can be omitted, and the liquid storage chamber R3 and the liquid chamber L of the tank 6 can communicate with each other through an opening 20 penetrating the outer tube 4 and the reservoir 6a. In the shock absorber D1 configured as described above, since the tank 6 is provided outside the outer tube 4, the interior of the liquid storage chamber R3 can be filled with only the hydraulic oil (liquid), and even if the hydraulic oil (liquid) flows into the liquid storage chamber R3 through the variable damping valve V during the extension / contraction operation, the hydraulic oil (liquid) can be prevented from entraining the gas in the liquid storage chamber R3.Even if the interior of the tank 6 is not divided into gas and liquid by the partition member, since the liquid storage chamber R3 communicates with the tank 6 via the orifice 20, the flow rate of the hydraulic oil (liquid) is reduced, so that the gas can be prevented from being entrained into the hydraulic oil (liquid) in the tank 6. Therefore, according to the shock absorber D1 configured as described above, since there is no fear of gas entrainment in the liquid storage chamber R3, the entire length of the outer tube 4 can be shortened. This not only shortens the base length of the shock absorber D1 and does not affect the mountability at the mounting destination, but also prevents the gas from being entrained into the hydraulic oil (liquid), so that the gas can be prevented from mixing with the cylinder 1, and the intended damping force can be exerted.

[0059] Although a preferred embodiment of the present invention has been described in detail above, modifications, variations and changes may be made without departing from the claims. List of reference symbols 1 cylinder 2 pistons 3 piston rod 4 Outer tube 6 tanks 7 Intermediate pipe D Shock absorber P Damping passage R1 Rebound side chamber R2 Compression-side chamber R3 Liquid storage chamber V Variable damping valve QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2014-231912 A [0004, 0005]

Claims

[1] Shock absorber, which includes: a cylinder; a piston movably inserted into the cylinder and dividing an interior of the cylinder into an extension-side chamber and a compression-side chamber filled with a fluid; a piston rod inserted into the cylinder and connected to the piston; an outer tube arranged on an outer peripheral side of the cylinder and forming a liquid storage chamber filled internally with only a liquid; a damping passage allowing communication between the rebound-side chamber and the fluid storage chamber; a variable damping valve provided in the damping passage and capable of adjusting a resistance exerted on a flow of a fluid from the rebound-side chamber to the fluid storage chamber; and a tank disposed outside the outer tube and communicating with the liquid storage chamber to store a liquid. [2] A shock absorber according to claim 1, wherein the outer tube covers the cylinder over an entire length in the axial direction. [3] Shock absorber according to claim 1, comprising: an intermediate tube arranged between the cylinder and the outer tube and forming the damping passage between the intermediate tube and the cylinder, wherein the liquid storage chamber is formed between the intermediate tube and the outer tube.

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