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Abstract

The present invention provides a shock absorber that can reduce fatigue in the sub-valve and suppress the occurrence of phenomena such as insufficient compression damping force and the generation of abnormal noise and shock when the valve contracts at high speed. [Solution] The shock absorber D comprises a cylinder 1, a partition member 6 that separates the working chamber W and the reservoir R, a piston rod 2, a piston 3 connected to the piston rod 2 and inserted into the cylinder 1 to divide the working chamber W into an extension chamber R1 and a compression chamber R2, an extension main valve 4 that provides resistance to the flow of liquid from the extension chamber R1 to the compression chamber R2, a compression main valve 5 that provides resistance to the flow of liquid from the compression chamber R2 to the extension chamber R1, an extension sub-valve 7 that provides resistance to the flow of liquid from the reservoir R to the compression chamber R2 and generates a damping force when extending at a very low speed, and a compression sub-valve 8 that provides resistance to the flow of liquid from the compression chamber R2 to the reservoir R and generates a damping force when contracting at a very low speed.

Description

Technical Field

[0001] The present invention relates to a shock absorber.

Background Art

[0002] A shock absorber is interposed between a vehicle body and wheels in a vehicle, for example, for the purpose of improving the ride comfort of the vehicle, and suppresses the vibrations of the vehicle body and wheels by the damping force exerted during expansion and contraction.

[0003] Such a shock absorber includes, for example, a cylinder, a rod movably inserted into the cylinder, a piston slidably inserted into the cylinder and partitioning the inside of the cylinder into an extension chamber and a compression chamber, a free piston slidably inserted into the cylinder and partitioning an air chamber below the compression chamber inside the cylinder, a damping passage provided in the piston and communicating the extension chamber and the compression chamber, and a damping valve provided in the damping passage.

[0004] In recent years, for vehicle shock absorbers, in order to improve the ride comfort of the vehicle, in the very low speed range where the expansion and contraction speed is lower than the low speed, the damping coefficient is increased, the damping force is quickly raised with respect to the switching of the expansion and contraction stroke, in the low speed range, the damping coefficient is made smaller than that in the very low speed range, and further, in the medium to high speed range exceeding the low speed, although it is proportional to the expansion and contraction speed, it is desired to exhibit a damping force characteristic with a smaller damping coefficient than in the low speed range.

[0005] In order to meet such demands, in addition to a main valve that mainly generates a damping force when the shock absorber expands and contracts in the medium to high speed range, a shock absorber equipped with a damping valve having a sub-valve that generates a damping force when expanding and contracting in the very low speed range has been developed. The sub-valve for the very low speed range mounted on this shock absorber includes a leaf valve that is annular and has its inner peripheral side fixed and its outer peripheral side allowed to deflect, an annular opposing seat portion that is annular and faces the outer periphery of the leaf valve without contact, and a valve seat member having a port on the inner peripheral side of the opposing seat portion, and gives resistance to the flow of the working oil flowing back and forth between the extension chamber and the compression chamber.

[0006] In a damping valve configured in this way, when the expansion and contraction speed of the shock absorber is in the very low speed range, the leaf valve does not flex much, limiting the flow area between it and the opposing seat to an extremely small size. As a result, a damping force characteristic that rises sharply in accordance with the expansion and contraction speed can be obtained, and a damping force characteristic suitable for a vehicle can be realized (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2019-183918 [Overview of the project] [Problems that the invention aims to solve]

[0008] In the aforementioned shock absorber, the piston, which is fitted to the outer circumference of the small-diameter tip of the piston rod, receives lateral force. Therefore, it is difficult to reduce the outer diameter of the small-diameter portion of the piston rod in order to ensure strength. Furthermore, it is difficult to increase the outer diameter of the valve seat member due to constraints on the cylinder diameter from the standpoint of strength and mountability. Consequently, it is difficult to increase the difference between the inner and outer diameters of the leaf valve in the sub-valve.

[0009] On the other hand, if the buffer is of the single-cylinder type, the flow rate passing through the sub-valve during extension and retraction is equal to the value obtained by multiplying the extension and retraction speed by the area obtained by subtracting the cross-sectional area of ​​the piston rod from the cross-sectional area of ​​the cylinder.

[0010] Therefore, in conventional shock absorbers, the passage of a large flow rate of hydraulic fluid during expansion and contraction must be permitted by a sub-valve for very low speed ranges. However, as mentioned above, it is difficult to ensure a large difference in the inner and outer diameters of the leaf valve, so the sub-valve must allow the leaf valve to bend significantly during the expansion and contraction of the shock absorber to allow the passage of a large flow rate of hydraulic fluid.

[0011] Thus, in conventional shock absorbers, the amount of deflection of the leaf valve in the sub-valve tends to increase during expansion and contraction, resulting in significant stress on the leaf valve and raising concerns about fatigue.

[0012] Furthermore, in conventional shock absorbers, the large volume of hydraulic fluid passing through the damping valve increases the viscosity of the hydraulic fluid during winter when the outside temperature is low, thus increasing the resistance exerted on the flow of hydraulic fluid through the damping valve. As a result, when the shock absorber contracts at high speed, the pressure in the extension chamber decreases significantly, leading to insufficient compression damping force to prevent the shock absorber from contracting, and potentially causing abnormal noise and shock. This phenomenon is more likely to occur as the resistance to the flow of hydraulic fluid during shock absorber contraction increases, and when this phenomenon occurs, abnormal noise or shock may occur.

[0013] Therefore, the objective is to provide a shock absorber that can reduce fatigue in the sub-valve and suppress the occurrence of phenomena such as insufficient compression damping force and the generation of abnormal noise and shock when the valve contracts at high speed. [Means for solving the problem]

[0014] To solve the aforementioned problem, the shock absorber of the present invention comprises a cylinder, a partition member that divides the inside of the cylinder into an operating chamber and a reservoir, a piston rod that is axially movable into the operating chamber, a piston connected to the piston rod and axially movable into the cylinder that divides the operating chamber into an extension chamber and a compression chamber filled with liquid, an extension main valve that provides resistance to the flow of liquid from the extension chamber to the compression chamber, a compression main valve that provides resistance to the flow of liquid from the compression chamber to the extension chamber, an extension sub-valve that provides resistance to the flow of liquid from the reservoir to the compression chamber and generates a damping force when the piston speed is in the very low speed range during extension operation, and a compression sub-valve that provides resistance to the flow of liquid from the compression chamber to the reservoir and generates a damping force when the piston speed is in the very low speed range during contraction operation.

[0015] With a buffer configured in this way, since the extension sub-valve and compression sub-valve are placed between the compression chamber and the reservoir, the flow rate of liquid passing through the extension sub-valve and compression sub-valve can be reduced, thereby reducing fatigue of the extension sub-valve and compression sub-valve. Furthermore, even when the buffer contracts at high speed, it is possible to prevent the phenomenon of insufficient compression damping force that hinders the buffer's contraction, as well as the generation of abnormal noise and shock.

[0016] Furthermore, the partition member in the buffer has an extension port and a compression port that connect the compression chamber and the reservoir, and the extension sub-valve and compression sub-valve may be provided on the partition member. With a buffer configured in this way, if a partition member equipped with the extension sub-valve and compression sub-valve is provided, the compression chamber and the reservoir can be partitioned within the cylinder, and the extension sub-valve and compression sub-valve can be easily installed between the compression chamber and the reservoir within the cylinder, improving ease of assembly, and since the extension sub-valve and compression sub-valve can be housed within the cylinder, it does not lead to an increase in the size of the buffer.

[0017] Furthermore, the partition member in the buffer may have an extension valve seat surrounding the outlet of the extension port and a compression valve seat surrounding the outlet of the compression port, the extension sub-valve may be an annular leaf valve that opens and closes the extension port by seating away from the extension valve seat, and the compression sub-valve may be an annular leaf valve that opens and closes the compression port by seating away from the compression valve seat.

[0018] With a buffer configured in this way, the flow rate of liquid passing through the extension sub-valve and compression sub-valve can be reduced, and the amount of deflection of the extension sub-valve and compression sub-valve when they are open can be reduced, thus further reducing fatigue of the extension sub-valve and compression sub-valve. Furthermore, by increasing the difference in inner and outer diameters between the extension sub-valve and compression sub-valve, a larger flow area can be secured when they are open, so that the extension sub-valve and compression sub-valve do not affect situations where damping force is to be generated by the extension main valve and compression main valve.

[0019] Furthermore, when the extension-side sub-valve and the compression-side sub-valve in the shock absorber are composed of a single valve, the cost can be reduced, and since the flow rate passing through the extension-side sub-valve and the compression-side sub-valve is small, fatigue can be reduced even if the extension-side sub-valve and the compression-side sub-valve are composed of a single valve that requires bending on both sides.

[0020] Also, in the shock absorber, the extension-side main valve may be an annular leaf valve, the compression-side main valve may be an annular leaf valve, the inner diameter of the extension-side sub-valve may be smaller than the inner diameter of the extension-side main valve, and the inner diameter of the compression-side sub-valve may be smaller than the inner diameter of the compression-side main valve. According to the shock absorber configured in this way, the difference between the inner and outer diameters of the extension-side sub-valve and the compression-side sub-valve can be increased, and a flow passage area larger than that of the extension-side main valve and the compression-side main valve can be ensured after the valve is opened. Therefore, there is no risk that the extension-side sub-valve will generate a damping force larger than that of the extension-side main valve, and there is no risk that the compression-side sub-valve will generate a damping force larger than that of the compression-side main valve.

Advantages of the Invention

[0021] According to the shock absorber of the present invention, fatigue in the sub-valve can be reduced, and the occurrence of a phenomenon in which the compression-side damping force is insufficient and abnormal noise and impact occur when contracting at high speed can be suppressed. [[ID=!3]]

Brief Description of the Drawings

[0022] [Figure 1] It is a longitudinal sectional view of a shock absorber in an embodiment of the present invention. [Figure 2] It is a partially enlarged longitudinal sectional view of a shock absorber in an embodiment of the present invention. [Figure 3] It is a diagram showing the damping force characteristics of a shock absorber in an embodiment of the present invention.

Modes for Carrying Out the Invention

[0023] Hereinafter, the present invention will be described based on the embodiments shown in the drawings. As shown in FIGS. 1 and 2, in one embodiment, the shock absorber D includes a cylinder 1, a partition member 6 that divides the inside of the cylinder 1 into a working chamber W and a reservoir R, a piston rod 2 that is inserted into the cylinder 1 so as to be axially movable, a piston 3 that is connected to the piston rod 2 and is inserted into the cylinder 1 so as to be axially movable and divides the working chamber W filled with liquid into an extension chamber R1 and a compression chamber R2, an extension main valve 4 that provides resistance to the flow of liquid from the extension chamber R1 to the compression chamber R2, a compression main valve 5 that provides resistance to the flow of liquid from the compression chamber R2 to the extension chamber R1, an extension sub - valve 7 that provides resistance to the flow of liquid from the reservoir R to the compression chamber R2, and a compression sub - valve 8 that provides resistance to the flow of liquid from the compression chamber R2 to the reservoir R. The shock absorber D is interposed between the vehicle body and the vehicle axle (not shown) and generates a damping force during expansion and contraction to suppress the vibration of the vehicle body.

[0024] Hereinafter, each part of the shock absorber D will be described in detail. The cylinder 1 is cylindrical, the bottom is closed by a cap 13, and the piston 3 is inserted into the inside thereof so as to be movable freely as described above. The inside of the cylinder 1 is partitioned by the partition member 6 into a working chamber W above the partition member 6 in FIG. 1 and a reservoir R. Also, on the side of the anti - piston below the partition member 6 inside the cylinder 1, a free piston 14 that is axially movable with respect to the cylinder 1 by making the outer periphery slide - contact with the inner periphery of the cylinder 1 and divides the reservoir R into a liquid chamber L and a gas chamber G is inserted. The free piston 14 can change the ratio of the volume of the liquid chamber L and the volume of the gas chamber G in the reservoir R by moving in the vertical direction (axial direction in FIG. 1) inside the cylinder 1. The reservoir R only needs to be partitioned into a liquid chamber L and a gas chamber G, and an elastic partition such as a diaphragm or a bellows may be used instead of the free piston 14 for partitioning the liquid chamber L and the gas chamber G. The inner diameter of the lower side of the cylinder 1 is larger than that of the upper side, and a step portion 1a is formed on the inner periphery of the cylinder 1.

[0025] Furthermore, the inside of cylinder 1 is divided by piston 3 into an extension chamber R1 above piston 3 in Figure 1 and a compression chamber R2 below piston 3 in Figure 1. The extension chamber R1 and compression chamber R2, which are the working chambers W inside cylinder 1, and the liquid chamber L inside reservoir R are filled with a liquid, such as hydraulic oil. In addition to hydraulic oil, water, aqueous solutions, etc., may also be used as the liquid. When hydraulic oil is used as the liquid filling inside reservoir R, it is preferable to use an inert gas such as nitrogen as the gas to prevent deterioration of the hydraulic oil.

[0026] Furthermore, a rod guide 10 is fitted to the upper end of the cylinder 1 in Figure 1, which slidably supports the piston rod 2. The rod guide 10 is fixed to the cylinder 1 by crimping the upper end of the cylinder 1, together with a sealing member 11 which is stacked above the rod guide 10 in Figure 1 and seals the space between the cylinder 1 and the piston rod 2.

[0027] The piston rod 2 is cylindrical in shape, with a reduced outer diameter at the tip, and includes a piston fitting portion 2a with the smallest diameter at the tip, a larger diameter portion 2b which has a larger outer diameter than the piston fitting portion 2a and is located above the piston fitting portion 2a in Figure 2, a stepped portion 2c provided at the boundary between the piston fitting portion 2a and the larger diameter portion 2b, and a threaded portion (not shown) provided on the outer circumference of the tip of the piston fitting portion 2a.

[0028] A bracket (not shown) is provided at the base end of the piston rod 2, which is the upper end in Figure 1, and the piston rod 2 is connected to one of the vehicle body and the wheel via this bracket (not shown). A bracket (not shown) is also provided at the bottom of the cylinder 1, and the cylinder 1 is connected to the other of the vehicle body and the wheel via this bracket (not shown).

[0029] In this way, the shock absorber D is interposed between the vehicle body and the wheels. When the vehicle travels on an uneven road surface, causing the wheels to vibrate vertically relative to the vehicle body, the piston rod 2 moves in and out of the cylinder 1, causing the shock absorber D to expand and contract, and the piston 3 moves vertically (axially) within the cylinder 1.

[0030] The piston 3 is annular and, as shown in Figure 1, has an extension main port 3a connecting the extension chamber R1 and the compression chamber R2, and a compression main port 3b connecting the compression chamber R2 and the extension chamber R1. An annular extension main valve 4 is superimposed on the lower part of the piston 3 in Figure 1, and an annular compression main valve 5 is superimposed on the upper part of the piston 3 in Figure 1. The compression main valve 5, piston 3, and extension main valve 4 are sequentially fitted onto the outer circumference of the piston fitting portion 2a of the piston rod 2, and are fixed to the piston rod 2 by being clamped between a piston nut 12, which is screw-connected to a threaded portion (not shown) at the tip of the piston rod 2, and a stepped portion 2c.

[0031] The extension-side main valve 4 is a laminated leaf valve constructed by stacking multiple annular plates, and is superimposed on the compression-side chamber side, which is the lower side in Figure 1 of the piston 3, and opens and closes the outlet end of the extension-side main port 3a. Furthermore, an orifice 4a formed by a notch is provided on the outer circumference of the annular plate of the extension-side main valve 4 that abuts against the piston 3. Note that the orifice 4a may be formed by a recess made by stamping or the like on a valve seat (not shown) surrounding the extension-side main port 3a on the piston 3, or it may be provided on a valve seat (not shown) on which the compression-side main valve, which will be described later, is seated.

[0032] Furthermore, the extension main valve 4 has its inner circumference fixed to the piston rod 2 and is allowed to flex on its outer circumference. When the pressure in the extension chamber R1 becomes higher than the pressure in the compression chamber R2 and the pressure difference between the two reaches the valve opening pressure, the extension main valve 4 flexes and opens in response to the pressure in the extension chamber R1 acting through the extension main port 3a, opening the extension main port 3a and connecting the extension chamber R1 and the compression chamber R2. The extension main valve 4 then resists the flow of liquid passing through the extension main port 3a, increasing the pressure in the extension chamber R1.

[0033] Conversely, if the pressure in the compression chamber R2 is higher than the pressure in the extension chamber R1, the extension main valve 4 is pressed against the piston 3 by the pressure in the compression chamber R2 acting from the rear side, thereby closing the extension main port 3a. When the extension main valve 4 is closed, the extension main port 3a is in communication with the compression chamber R2 only through the orifice 4a.

[0034] Furthermore, the number of stacked annular plates in the extension main valve 4 can be arbitrarily changed according to the desired damping force. In addition, although the extension main valve 4 is a leaf valve, it may be a valve other than a leaf valve as long as it can provide resistance to the flow of liquid passing through the extension main port 3a.

[0035] On the other hand, the compression-side main valve 5 is a laminated leaf valve constructed by stacking multiple annular plates, and is superimposed on the upper side of the piston 3 in Figure 1, on the extension-side chamber side, and opens and closes the outlet end of the compression-side main port 3b. The compression-side main valve 5 has its inner circumference fixed to the piston rod 2 and is allowed to bend on its outer circumference. When the pressure in the compression-side chamber R2 becomes higher than the pressure in the extension-side chamber R1 and the pressure difference between the two reaches the valve opening pressure, it bends and opens due to the pressure from the compression-side chamber R2 acting through the compression-side main port 3b, opening the compression-side main port 3b and connecting the compression-side chamber R2 and the extension-side chamber R1. The compression-side main valve 5 then resists the flow of liquid passing through the compression-side main port 3b, increasing the pressure in the compression-side chamber R2.

[0036] Conversely, if the pressure in the extension chamber R1 is higher than the pressure in the compression chamber R2, the compression main valve 5 is pressed against the piston 3 by the pressure from the extension chamber R1 acting from the rear side, thereby closing the compression main port 3b. The number of stacked annular plates in the compression main valve 5 can be arbitrarily changed according to the desired damping force. Furthermore, although the compression main valve 5 is a leaf valve, it may be a valve other than a leaf valve as long as it can provide resistance to the flow of liquid passing through the compression main port 3b.

[0037] Next, the partition member 6, the extension sub-valve 7, and the compression sub-valve 8 will be described. As shown in Figure 2, the extension sub-valve 7 and the compression sub-valve 8 are provided in the partition member 6.

[0038] The partition member 6 is fixed to the cylinder 1 and, as described above, divides the inside of the cylinder 1 into an operating chamber W consisting of an extension chamber R1 and a compression chamber R2, and a reservoir R. More specifically, the partition member 6 is annular and has an extension port 6a and a compression port 6b that open from the upper end to the lower end along the axial direction, and has a stepped portion 6c on its outer circumference.

[0039] As shown in Figure 2, the partition member 6 is fitted with its outer circumference to the inner circumference of the cylinder 1 below the stepped portion 1a, and the stepped portion 6c is in contact with the stepped portion 1a of the cylinder 1. It is fixed to the inner circumference of the cylinder 1 by being sandwiched between the stop ring 15, which is fixed to the inner circumference of the cylinder 1 and in contact with the lower end outer circumference, and the stepped portion 1a. In addition to fixing the partition member 6 to the cylinder 1 by sandwiching it between the stepped portion 1a and the stop ring 15, the outer circumference of the cylinder 1 may be crimped to form a protrusion, and this protrusion may be made to protrude into an annular groove provided on the outer circumference of the partition member 6 to fix the partition member 6 to the cylinder 1, or the partition member 6 may be fixed to the cylinder 1 by other means.

[0040] The extension ports 6a and compression ports 6b provided on the partition member 6 are both provided in multiples on the partition member 6 and are installed alternately in the circumferential direction on the same circumference. One end of both the extension ports 6a and compression ports 6b is connected to the compression chamber R2 above the partition member 6, and the other end is connected to the liquid chamber L in the reservoir R below the partition member 6, thus connecting the compression chamber R2 and the liquid chamber L.

[0041] Furthermore, at the upper end of the partition wall member 6, which is on the pressure side chamber side in Figure 2, a petal-shaped extension valve seat 6d is provided, projecting toward the pressure side chamber side and surrounding the outlet end of the extension port 6a. At the lower end of the partition wall member 6, which is on the reservoir side in Figure 2, a petal-shaped pressure valve seat 6e is provided, projecting toward the reservoir side and surrounding the outlet end of the pressure port 6b.

[0042] The extension sub-valve 7 is an annular laminated leaf valve constructed by stacking multiple annular plates, and is superimposed on the pressure chamber side, which is the upper side in Figure 1 of the partition member 6. It opens and closes the outlet end of the extension port 6a by seating and unseating with the extension valve seat 6d. The extension sub-valve 7 is fixed to the outer circumference of a mounting shaft 16 whose inner circumference is inserted through the inner circumference of the partition member 6, and is allowed to deflect on its outer circumference with the outer edge of the spacer 17, which is stacked on the upper side in Figure 2, which is the opposite side of the partition member, as the fulcrum. When the pressure in the liquid chamber L becomes higher than the pressure in the pressure chamber R2 due to the extension of the buffer D, and the pressure difference between the two reaches the valve opening pressure, it deflects and opens due to the pressure from the liquid chamber L acting through the extension port 6a, opening the extension port 6a and connecting the liquid chamber L and the pressure chamber R2.

[0043] The extension sub-valve 7 resists the flow of liquid through the extension port 6a, reducing the pressure in the compression chamber R2 and increasing the pressure difference between the extension chamber R1 and the compression chamber R2, thereby generating a damping force that hinders the extension of the buffer D. The extension sub-valve 7 does not have an orifice, and the partition member 6 also does not have an orifice parallel to the extension sub-valve 7. Therefore, when the extension sub-valve 7 is seated on the extension valve seat 6d, it does not open the extension port 6a, completely blocking the compression chamber R2 and the liquid chamber L. Furthermore, the opening pressure of the extension sub-valve 7 is lower than the opening pressure of the extension main valve 4, and the extension sub-valve 7 is a valve that generates a damping force when the extension speed of the buffer D is in the very low speed range.

[0044] Conversely, when the shock absorber D contracts, the extension sub-valve 7 is pressed against the partition member 6 by the pressure from the compression chamber R2 acting from the rear side, thereby closing the extension port 6a. The extension sub-valve 7 and the extension main valve 4 open when the shock absorber D is extended, but the opening pressure of the extension sub-valve 7 is lower than that of the extension main valve 4, so the extension sub-valve 7 opens earlier than the extension main valve 4 when the shock absorber D expands and contracts. The number of stacked annular plates in the extension sub-valve 7 can be arbitrarily changed according to the desired damping force when the shock absorber D is extended in the very low speed range.

[0045] The pressure-side sub-valve 8 is an annular laminated leaf valve constructed by stacking multiple annular plates, and is superimposed on the reservoir side, which is the lower side in Figure 1 of the partition member 6. It seats and dissipates from the pressure-side valve seat 6e to open and close the outlet end of the pressure-side port 6b. The pressure-side sub-valve 8 is fixed to the outer circumference of a mounting shaft 16, the inner circumference of which is inserted through the inner circumference of the partition member 6. The outer edge of an annular spacer 20, which is positioned in the lower part of Figure 2 on the opposite side of the partition member and mounted on the outer circumference of the mounting shaft 16, is used as a fulcrum to allow for lateral deflection. When the pressure in the pressure-side chamber R2 becomes higher than the pressure in the liquid chamber L due to the contraction of the buffer D, and the pressure difference between the two reaches the valve opening pressure, the sub-valve 8 deflects and opens due to the pressure in the pressure-side chamber R2 acting through the pressure-side port 6b, opening the pressure-side port 6b and connecting the pressure-side chamber R2 and the liquid chamber L.

[0046] The compression sub-valve 8 resists the flow of liquid through the compression port 6b, increasing the pressure in the compression chamber R2 and widening the pressure difference between the compression chamber R2 and the extension chamber R1, thereby generating a damping force that prevents the shock absorber D from contracting. The compression sub-valve 8 does not have an orifice, and the partition member 6 also does not have an orifice parallel to the compression sub-valve 8. Therefore, when the compression sub-valve 8 is seated on the compression valve seat 6e, it does not open the compression port 6b, completely blocking the compression chamber R2 from the liquid chamber L. In addition, the opening pressure of the extension sub-valve 7 is lower than the opening pressure of the extension main valve 4, and the extension sub-valve 7 is a valve that generates a damping force when the extension speed of the shock absorber D is in the very low speed range.

[0047] Conversely, when the buffer D extends and the pressure in the liquid chamber L becomes higher than the pressure in the pressure chamber R2, the compression sub-valve 8 is pressed against the partition member 6 by the pressure from the liquid chamber L acting from the rear side, thereby closing the compression port 6b. The compression sub-valve 8 and the compression main valve 5 open when the buffer D contracts, but the opening pressure of the compression sub-valve 8 is lower than the opening pressure of the compression main valve 5, so the compression sub-valve 8 opens earlier than the compression main valve 5 when the buffer D contracts. The number of stacked annular plates in the compression sub-valve 8 can be arbitrarily changed according to the desired damping force when the buffer D contracts in the very low speed range.

[0048] The mounting shaft 16 comprises a shaft portion 16a that is inserted into the inner circumference of the spacer 17, the extension sub-valve 7, the partition member 6, and the compression sub-valve 8, a flange 16b provided at the lower end of the shaft portion 16a in Figure 2, and a threaded portion 16c formed at the upper end of the shaft portion 16a in Figure 2. The mounting shaft 16 holds the spacer 17, the extension sub-valve 7, the partition member 6, and the compression sub-valve 8, which are fitted onto the outer circumference of the shaft portion 16a, by clamping them with a nut 18 that is screw-connected to the flange 16b and the threaded portion 16c. Thus, the spacer 17, the extension sub-valve 7, the partition member 6, and the compression sub-valve 8 are fixed to the outer circumference of the shaft portion 16a of the mounting shaft 16.

[0049] Unlike the piston rod 2, the mounting shaft 16, to which the inner circumferences of the extension sub-valve 7 and compression sub-valve 8 are fixed, is not connected to the vehicle body. Therefore, even if a bending moment is applied to the shock absorber D, it does not experience any moment. For this reason, the diameter of the mounting shaft 16 can be smaller than the diameter of the piston fitting portion 2a of the piston rod 2, and is therefore smaller than the diameter of the piston fitting portion 2a of the piston rod 2.

[0050] Therefore, compared to mounting the extension sub-valve 7 and compression sub-valve 8 on the outer circumference of the piston fitting portion 2a of the piston rod 2, the inner diameters of the extension sub-valve 7 and compression sub-valve 8 can be made smaller, while the outer diameters of the extension sub-valve 7 and compression sub-valve 8 can be made the same as the outer diameters of the extension main valve 4 and compression main valve 5 mounted on the outer circumference of the piston fitting portion 2a. As described above, in the buffer D of this embodiment, the difference between the inner and outer diameters of the extension sub-valve 7 and compression sub-valve 8 can be made large, so the bending rigidity of the extension sub-valve 7 and compression sub-valve 8 can be reduced, and the resistance that the extension sub-valve 7 and compression sub-valve 8 exert on the liquid flow passing through the extension port 6a and compression port 6b can be reduced.

[0051] Furthermore, the extension sub-valve 7 and the compression sub-valve 8 may be poppet valves or the like, in addition to leaf valves, as long as they can completely block communication between the compression chamber R2 and the reservoir R when closed without having any throttling such as orifices or chokes, and can open and generate damping force from the time the piston speed of the shock absorber D is in the very low speed range when it is expanding and contracting. When the extension sub-valve 7 and the compression sub-valve 8 are poppet valves, the mounting shaft 16 required for leaf valves is not necessary, and since the extension sub-valve 7 and the compression sub-valve 8 are provided on the piston part, they are not obstructed by the piston rod 2, so a large flow area can be secured between the extension port 6a and the compression port 6b, and thus the resistance that the extension sub-valve 7 and the compression sub-valve 8 impart to the liquid flow passing through the extension port 6a and the compression port 6b can be reduced.

[0052] The operation of the shock absorber D, configured as described above, will now be explained. First, the operation of the shock absorber D when it is extended, with the piston 3 moving upward relative to the cylinder 1 in Figure 1, will be explained.

[0053] As piston 3 moves upward relative to cylinder 1 in Figure 1, the extension chamber R1 is reduced and the compression chamber R2 is expanded as piston 3 moves. When the piston speed, which is the speed at which piston 3 moves relative to cylinder 1 during the extension of buffer D, is in the very low speed range, the difference between the pressure in the extension chamber R1 and the pressure in the compression chamber R2 does not reach the opening pressure of the extension main valve 4. Therefore, the extension main valve 4 does not deflect and remains closed, and the liquid in the reduced extension chamber R1 moves to the compression chamber R2 through the extension main port 3a and the orifice 4a. When the piston speed is in the very low speed range, the flow rate of liquid through the orifice 4a is extremely small, so the resistance that the orifice 4a exerts on the liquid flow is also extremely small.

[0054] When the buffer D extends, the piston rod 2 moves upward in Figure 1 and exits the cylinder 1. As the volume pushed aside by the piston rod 2 within the cylinder 1 decreases, the extension-side sub-valve 7 opens, connecting the liquid chamber L and the pressure-side chamber R2 through the extension-side port 6a, and liquid moves from the liquid chamber L to the pressure-side chamber R2. The extension-side sub-valve 7 then resists the flow of liquid through the extension-side port 6a, causing the pressure-side chamber R2 to be depressurized and become lower than the pressure in the extension-side chamber R1. Furthermore, as the buffer D extends, the volume of liquid that moves from the liquid chamber L to the pressure-side chamber R2 corresponds to the volume of liquid that moves out of the cylinder 1. As a result, the free piston 14 moves upward in Figure 1 within the cylinder 1, expanding the air chamber G by the volume of the moved liquid. In this way, the reservoir R compensates for the volume of the piston rod 2 that exits the cylinder 1.

[0055] Therefore, when the shock absorber D is extended and the piston speed is in the very low speed range, as shown in Figure 3, the resistance exerted by the extension-side sub-valve 7 on the liquid flow generates a damping force that hinders the extension of the shock absorber D. The damping force characteristic, which is the characteristic of the damping force with respect to piston speed, has a high damping coefficient and the damping force rises rapidly in response to the increase in piston speed.

[0056] Furthermore, the amount of liquid passing through the extension sub-valve 7 is equal to the volume of the piston rod 2 exiting the cylinder 1, and the amount of liquid passing through can be reduced compared to when the extension sub-valve 7 is provided on the piston. When the extension sub-valve 7 is provided on the piston, the extension sub-valve 7 must allow the passage of a liquid amount equal to the value obtained by multiplying the displacement of the piston 3 by the area obtained by subtracting the cross-sectional area of ​​the piston rod 2 from the cross-sectional area of ​​the piston 3. However, in a single-tube type buffer D, in order to generate a high damping force when extended, the cross-sectional area of ​​the piston rod 2 needs to be reduced to a extent that does not cause problems in terms of strength. Therefore, by providing the extension sub-valve 7 between the compression chamber R2 and the reservoir R instead of on the piston, the amount of liquid passing through the extension sub-valve 7 when the buffer D is extended can be reduced. In this way, the flow rate passing through the extension sub-valve 7 can be reduced, and the amount of deflection of the extension sub-valve 7 when it opens can be reduced, thus reducing the fatigue of the extension sub-valve 7.

[0057] Furthermore, because a bending moment is applied to the shock absorber D, it is not necessary to provide an extension sub-valve 7 at the piston fitting portion 2a of the piston rod 2, which cannot have its diameter reduced due to strength issues. This allows for a larger difference between the inner and outer diameters of the extension sub-valve 7. Therefore, the bending rigidity of the extension sub-valve 7 can be reduced, and the resistance that the extension sub-valve 7 exerts on the liquid flow can be reduced compared to the case where an extension sub-valve is provided on the piston portion.

[0058] Next, when the piston speed of the buffer D extends beyond the very low speed range and enters the low speed range, the pressure difference between the extension chamber R1 and the pressure in the compression chamber R2 increases, but it has not yet reached the opening pressure of the extension main valve 4. Therefore, the extension main valve 4 does not flex and remains closed, and the liquid in the contracted extension chamber R1 moves to the compression chamber R2 through the extension main port 3a and the orifice 4a. As the piston speed enters the low speed range, the flow rate of the liquid flowing through the orifice 4a increases, so the resistance that the orifice 4a exerts on the liquid flow becomes greater.

[0059] When the piston speed of the buffer D is in the low-speed range during extension, the extension sub-valve 7 is farther away from the extension valve seat 6d of the partition member 6. As a result, the resistance exerted by the extension sub-valve 7 on the liquid flow is smaller than the resistance exerted by the orifice 4a on the liquid flow.

[0060] Therefore, when the shock absorber D is extended and the piston speed is in the low-speed range, as shown in Figure 3, a damping force is generated that hinders the extension operation of the shock absorber D, mainly due to the resistance that the orifice 4a exerts on the liquid flow. Thus, when the shock absorber D is extended and the piston speed is in the low-speed range, the shock absorber D generates a damping force that is proportional to the square of the piston speed, which is characteristic of orifices, and the damping force characteristics are such that the damping coefficient is lower than in the very low-speed range.

[0061] Furthermore, when the piston speed of the buffer D extends beyond the low-speed range and reaches the high-speed range, the pressure difference between the extension chamber R1 and the compression chamber R2 becomes large enough to exceed the opening pressure of the extension main valve 4. As a result, the liquid in the contracted extension chamber R1 pushes open the extension main valve 4 and moves through the extension main port 3a to the compression chamber R2.

[0062] When the piston speed of the shock absorber D is in the high-speed range during extension operation, the extension sub-valve 7 is separated from the extension valve seat 6d of the partition member 6, so the resistance exerted by the extension sub-valve 7 on the liquid flow is smaller than the resistance exerted by the extension main valve 4 on the liquid flow.

[0063] Therefore, when the shock absorber D is extended and the piston speed is in the high-speed range, as shown in Figure 3, a damping force is generated that hinders the extension operation of the shock absorber D, mainly due to the resistance that the extension-side main valve 4 exerts on the liquid flow. Thus, when the shock absorber D is extended and the piston speed is in the high-speed range, the damping force characteristics are such that the damping coefficient is lower than at low speeds, but the damping force generally increases linearly with the piston speed.

[0064] Next, we will explain the operation of the shock absorber D when the piston 3 moves downward relative to the cylinder 1 in Figure 1. When the piston 3 moves downward relative to the cylinder 1 in Figure 1, the compression chamber R2 is reduced and the extension chamber R1 is expanded as the piston 3 moves. In the very low speed range, the piston speed, which is the speed at which the piston 3 moves relative to the cylinder 1 during the contraction of the shock absorber D, does not reach the opening pressure of the extension main valve 4. Therefore, the extension main valve 4 does not bend and remains closed, and the liquid in the reduced extension chamber R1 moves to the compression chamber R2 through the extension main port 3a and the orifice 4a. In the very low speed range, the flow rate of the liquid flowing through the orifice 4a is extremely small, so the resistance that the orifice 4a exerts on the liquid flow is also extremely small.

[0065] Furthermore, as the piston 3 moves downward relative to the cylinder 1 in Figure 1, the piston rod 2 enters the cylinder 1. When the piston speed is in the very low speed range during the contraction of the buffer D, the difference between the pressure in the pressure chamber R2 and the pressure in the reservoir R is small. However, the pressure sub-valve 8 opens, opening the pressure port 6b and connecting the pressure chamber R2 and the liquid chamber L, causing an amount of liquid equal to the volume of the piston rod 2 entering the cylinder 1 to move from the pressure chamber R2 to the liquid chamber L.

[0066] Therefore, when the piston speed is in the very low speed range during the contraction operation of the shock absorber D, the compression-side sub-valve 8 opens and resists the flow of liquid passing through the compression-side port 6b. As a result, the pressure in the compression-side chamber R2 rises to become higher than the pressure in the extension-side chamber R1, increasing the force pushing the piston 3 upwards, and the shock absorber D generates a damping force that hinders contraction.

[0067] Therefore, when the shock absorber D is contracting and the piston speed is in the very low speed range, as shown in Figure 3, the resistance exerted by the compression-side sub-valve 8 on the liquid flow generates a damping force that hinders the contraction of the shock absorber D. The damping force characteristic, which is the characteristic of the damping force with respect to piston speed, has a high damping coefficient and the damping force rises rapidly in response to the increase in piston speed.

[0068] Furthermore, the amount of liquid passing through the compression sub-valve 8 is equal to the volume that the piston rod 2 enters into the cylinder 1, and the amount of liquid passing through can be reduced compared to when the compression sub-valve 8 is provided on the piston. When the compression sub-valve 8 is provided on the piston, the compression sub-valve 8 must allow the passage of a liquid amount equal to the value obtained by multiplying the area obtained by subtracting the cross-sectional area of ​​the piston rod 2 from the cross-sectional area of ​​the piston 3 by the displacement of the piston 3. However, in a single-cylinder type buffer D, in order to generate a high damping force when it contracts, the cross-sectional area of ​​the piston rod 2 needs to be reduced to a extent that does not cause problems in terms of strength. Therefore, by providing the compression sub-valve 8 between the compression chamber R2 and the reservoir R instead of on the piston, the amount of liquid passing through the compression sub-valve 8 when the buffer D contracts can be reduced. In this way, the flow rate passing through the compression sub-valve 8 can be reduced, and the amount of deflection of the compression sub-valve 8 when it opens can be reduced, thus reducing the fatigue of the compression sub-valve 8.

[0069] Furthermore, because a bending moment is applied to the shock absorber D, it is not necessary to provide a compression sub-valve 8 at the piston fitting portion 2a of the piston rod 2, which cannot have its diameter reduced due to strength issues. This allows for a larger difference between the inner and outer diameters of the compression sub-valve 8. Therefore, the bending rigidity of the compression sub-valve 8 can be reduced, and the resistance that the compression sub-valve 8 exerts on the liquid flow can be reduced compared to the case where a compression sub-valve is provided on the piston portion.

[0070] Next, when the piston speed of buffer D contracts, if it goes beyond the very low speed range and enters the low speed range, the pressure difference between the pressure in the compression chamber R2 and the pressure in the expansion chamber R1 increases, but it has not yet reached the opening pressure of the compression main valve 5. Therefore, the compression main valve 5 does not flex and remains closed, and the liquid in the contracting compression chamber R2 moves to the expansion chamber R1 through the compression main port 3b and the orifice 4a. When the piston speed enters the low speed range, the flow rate of the liquid flowing through the orifice 4a increases, so the resistance that the orifice 4a exerts on the liquid flow increases.

[0071] When the piston speed of the buffer D is in the low-speed range during contraction, the pressure-side sub-valve 8 is separated from the pressure-side valve seat 6e in the partition member 6, so the resistance that the pressure-side sub-valve 8 exerts on the liquid flow is smaller than the resistance that the orifice 4a exerts on the liquid flow.

[0072] Therefore, when the shock absorber D is contracting and the piston speed is in the low-speed range, as shown in Figure 3, a damping force is generated that hinders the contraction of the shock absorber D, mainly due to the resistance that the orifice 4a exerts on the liquid flow. Thus, when the shock absorber D is contracting and the piston speed is in the low-speed range, the shock absorber D generates a damping force that is proportional to the square of the piston speed, which is characteristic of orifices, and the damping force characteristics are such that the damping coefficient is lower than in the very low-speed range.

[0073] Furthermore, when the piston speed of the buffer D contracts exceeds the low-speed range and reaches the high-speed range, the pressure difference between the compression chamber R2 and the expansion chamber R1 becomes large enough to exceed the opening pressure of the compression main valve 5. As a result, the liquid in the compression chamber R2 pushes open the compression main valve 5 and moves through the compression main port 3b to the expansion chamber R1.

[0074] When the piston speed of the buffer D is in the high-speed range during contraction, the pressure-side sub-valve 8 also opens. However, because the pressure-side sub-valve 8 is far away from the pressure-side valve seat 6e, the resistance exerted by the pressure-side sub-valve 8 on the liquid flow is smaller than the resistance exerted by the pressure-side main valve 5 on the liquid flow.

[0075] Therefore, when the shock absorber D is contracting and the piston speed is in the high-speed range, as shown in Figure 3, a damping force is generated that hinders the contraction operation of the shock absorber D, mainly due to the resistance that the compression-side main valve 5 exerts on the liquid flow. Thus, when the shock absorber D is contracting and the piston speed is in the high-speed range, the damping force characteristics are such that the damping coefficient is lower than at low speeds, but the damping force generally increases linearly with the piston speed.

[0076] Even when the buffer D contracts at high speed, the presence of the compression-side sub-valve 8 between the compression-side chamber R2 and the reservoir R prevents the flow rate through the compression-side sub-valve 8 from becoming too high, suppressing a significant pressure drop in the extension-side chamber R1 and a pressure rise in the liquid chamber L. This prevents insufficient compression damping force that would hinder the contraction of the buffer D, thus preventing the occurrence of abnormal noises and shocks. Furthermore, the contraction speed of the buffer D when such phenomena occur can be made higher than the practical speed range in which the buffer D is used, thereby improving the practicality of the buffer D.

[0077] As described above, the shock absorber D of this embodiment comprises a cylinder 1, a partition member 6 that divides the inside of the cylinder 1 into an operating chamber W and a reservoir R, a piston rod 2 that is inserted into the operating chamber W so as to be movable in the axial direction, a piston 3 that is connected to the piston rod 2 and inserted into the cylinder 1 so as to be movable in the axial direction and divides the operating chamber W into an extension chamber R1 and a compression chamber R2 that are filled with liquid, an extension main valve 4 that provides resistance to the flow of liquid from the extension chamber R1 to the compression chamber R2, a compression main valve 5 that provides resistance to the flow of liquid from the compression chamber R2 to the extension chamber R1, an extension sub-valve 7 that provides resistance to the flow of liquid from the reservoir R to the compression chamber R2 and generates a damping force when the piston speed is in the very low speed range during extension, and a compression sub-valve 8 that provides resistance to the flow of liquid from the compression chamber R2 to the reservoir R and generates a damping force when the piston speed is in the very low speed range during contraction.

[0078] In the buffer D configured in this way, when the piston speed is in the very low speed range, a damping force can be generated by the extension sub-valve 7 or compression sub-valve 8 provided between the compression chamber R2 and the reservoir R. Since the extension sub-valve 7 and compression sub-valve 8 do not need to be provided on the piston rod 2, the amount of liquid passing through the buffer D during expansion and contraction can be reduced.

[0079] Therefore, according to the shock absorber D of this embodiment, since the extension sub-valve 7 and the compression sub-valve 8 are provided between the compression chamber R2 and the reservoir R, the flow rate of liquid passing through the extension sub-valve 7 and the compression sub-valve 8 can be reduced, fatigue of the extension sub-valve 7 and the compression sub-valve 8 can be reduced, and even when contracted at high speed, it is possible to prevent the phenomenon in which there is insufficient compression damping force that hinders the contraction of the shock absorber D, as well as the generation of abnormal noise and shock. Furthermore, the contraction speed of the shock absorber D when this phenomenon occurs can be made higher than the practical speed range in which the shock absorber D is used, thereby improving the practicality of the shock absorber D.

[0080] Furthermore, in the buffer D of this embodiment, the partition member 6 has an extension port 6a and a compression port 6b that connect the compression chamber R2 and the reservoir R, and an extension sub-valve 7 and a compression sub-valve 8 are provided on the partition member 6.

[0081] With the buffer D configured in this way, by providing a partition member 6 equipped with an extension sub-valve 7 and a compression sub-valve 8, the compression chamber R2 and the reservoir R can be partitioned within the cylinder 1. Furthermore, the extension sub-valve 7 and the compression sub-valve 8 can be easily installed between the compression chamber R2 and the reservoir R within the cylinder 1, improving ease of assembly. Additionally, since the extension sub-valve 7 and the compression sub-valve 8 can be housed within the cylinder 1, the buffer D does not become larger. Alternatively, a passage connecting the compression chamber R2 and the reservoir R may be provided in addition to the partition member 6, and the extension sub-valve 7 and the compression sub-valve 8 may be installed in parallel in this passage.

[0082] Furthermore, in the buffer D of this embodiment, the partition member 6 has an extension valve seat 6d surrounding the outlet of the extension port 6a and a compression valve seat 6e surrounding the outlet of the compression port 6b, the extension sub-valve 7 is an annular leaf valve that opens and closes the extension port 6a by seating away from the extension valve seat 6d, and the compression sub-valve 8 is an annular leaf valve that opens and closes the compression port 6b by seating away from the compression valve seat 6e.

[0083] With the shock absorber D configured in this way, the extension-side sub-valve 7 and the compression-side sub-valve 8 close the corresponding extension-side port 6a and compression-side port 6b, so that the damping force can be built up even at extremely low piston speeds. Furthermore, since the piston rod 2 receives a lateral force input from a lateral direction perpendicular to the axial direction of the shock absorber D, it is difficult to reduce the outer diameter of the small-diameter section 2a on which the piston 3 is mounted. In conventional shock absorbers, the difference between the inner and outer diameters of the leaf valves in the sub-valves cannot be made large. However, in the shock absorber D of this embodiment, the extension-side sub-valve 7 and the compression-side sub-valve 8 are provided between the compression-side chamber R2 and the reservoir R. This reduces the amount of liquid passing through when the shock absorber D expands and contracts. Additionally, since it is not necessary to provide the extension-side sub-valve 7 and the compression-side sub-valve 8 in the small-diameter section 2a of the piston rod 2, which cannot have its outer diameter reduced for strength reasons due to receiving the moment input to the shock absorber D, the difference between the inner and outer diameters of the extension-side sub-valve 7 and the compression-side sub-valve 8 can be made larger, reducing the bending rigidity and ensuring a large flow area with a small amount of bending.

[0084] Therefore, according to the buffer D of this embodiment, the flow rate of liquid passing through the extension sub-valve 7 and the compression sub-valve 8 can be reduced, and the amount of deflection of the extension sub-valve 7 and the compression sub-valve 8 when they are open can be reduced. Thus, even if leaf valves that are prone to fatigue due to deflection are used, the fatigue of the extension sub-valve 7 and the compression sub-valve 8 can be further reduced. Furthermore, even if the extension sub-valve 7 and the compression sub-valve 8 are leaf valves with their inner circumferences fixed, since the extension sub-valve 7 and the compression sub-valve 8 are provided between the compression chamber R2 and the reservoir R, the difference between the inner and outer diameters can be increased. This allows for a large flow area to be secured when the valves are open, and the extension sub-valve 7 and the compression sub-valve 8 do not affect situations where damping force is to be generated by the extension main valve 4 and the compression main valve 5.

[0085] Furthermore, in the shock absorber D of this embodiment, the extension-side main valve 4 is an annular leaf valve, the compression-side main valve 5 is an annular leaf valve, the inner diameter of the extension-side sub-valve 7 is smaller than the inner diameter of the extension-side main valve 4, and the inner diameter of the compression-side sub-valve 8 is smaller than the inner diameter of the compression-side main valve 5. With shock absorber D configured in this way, the difference between the inner and outer diameters of the extension-side sub-valve 7 and the compression-side sub-valve 8 can be made large, and a larger flow area than that of the extension-side main valve 4 and the compression-side main valve 5 can be secured after the valves are opened. As a result, there is no risk that the extension-side sub-valve 7 will generate a greater damping force than the extension-side main valve 4, and there is no risk that the compression-side sub-valve 8 will generate a greater damping force than the compression-side main valve 5.

[0086] In this embodiment, the extension sub-valve 7 and the compression sub-valve 8 are both annular leaf valves in the shock absorber D, with their inner circumference fixed to the mounting shaft 16 and their outer circumference allowing for deflection. However, they may also be composed of a leaf valve whose inner circumference is not fixed to the mounting shaft 16 and whose entire structure can move toward and away from the partition member 6, and a spring that biases the leaf valve to seat on the corresponding extension valve seat 6d or compression valve seat 6e. In this case, when the extension sub-valve 7 and the compression sub-valve 8 are open, their entire structures move away from the partition member 6, opening the extension port 6a and the compression port 6b. This allows for a larger flow area than with leaf valves that have their inner circumferences fixed, thus reducing the influence of the extension sub-valve 7 and the compression sub-valve 8 on the damping force when the shock absorber D expands and contracts at speeds exceeding the low-speed range, and also facilitating tuning of the damping force characteristics.

[0087] Furthermore, the extension sub-valve 7 and the compression sub-valve 8 may be decarbon valves, as disclosed in Japanese Patent Application Publication No. 2004-225834 (though not shown in the figures), comprising an inner valve seat and an outer valve seat of different diameters, and an annular leaf valve that opens both ways, with one end face seated on the inner valve seat and the other end face seated on the outer valve seat. Furthermore, the extension sub-valve 7 and the compression sub-valve 8 may be a single valve, as disclosed in Japanese Patent Application Publication No. 2019-116902, comprising an annular valve body having one of its inner or outer circumferences fixed and the other of which is allowed to flex axially to both sides, and an annular opposing portion facing the other of the inner or outer circumferences of the annular valve body, thereby allowing the flow of liquid from the compression chamber R2 to the reservoir R and from the reservoir R to the compression chamber R2, while also providing resistance to the liquid flow. In this way, if the extension sub-valve 7 and the compression sub-valve 8 are configured as a single valve, costs can be reduced, and fatigue can be reduced even if the extension sub-valve 7 and the compression sub-valve 8 are configured as a single valve that requires flexing on both sides because the flow rate passing through the extension sub-valve 7 and the compression sub-valve 8 is small.

[0088] Although preferred embodiments of the present invention have been described in detail above, modifications, alterations, and changes are permitted as long as they do not deviate from the scope of the claims. [Explanation of Symbols]

[0089] 1...Cylinder, 2...Piston rod, 3...Piston, 4...Extension main valve, 5...Compression main valve, 6...Partition member, 6a...Extension port, 6b...Compression port, 6d...Extension valve seat, 6e...Compression valve seat, 7...Extension sub-valve, 8...Compression sub-valve, D...Buffer, R...Reservoir, R1...Extension chamber, R2...Compression chamber, W...Actuating chamber

Claims

1. Cylinder and A partition member divides the inside of the cylinder into an operating chamber and a reservoir, A piston rod is inserted into the aforementioned operating chamber so as to be movable in the axial direction, A piston connected to the piston rod and inserted into the cylinder so as to be movable in the axial direction, dividing the working chamber into an extension chamber and a compression chamber, both filled with liquid; An extension main valve that provides resistance to the flow of liquid from the extension chamber to the compression chamber, A compression-side main valve that provides resistance to the flow of liquid from the compression-side chamber to the extension-side chamber, An extension sub-valve provides resistance to the flow of liquid from the reservoir to the compression chamber, thereby generating a damping force when the piston speed during extension is in the very low speed range. It is equipped with a compression sub-valve that provides resistance to the flow of liquid from the compression chamber to the reservoir, thereby generating a damping force when the piston speed during contraction is in the very low speed range. A buffer characterized by the following features.

2. The partition wall member is It has an extension port and a compression port that connect the compression chamber and the reservoir, The extension sub-valve and the compression sub-valve are provided in the partition member. The shock absorber according to feature 1.

3. The partition member has an extension valve seat surrounding the outlet of the extension port and a compression valve seat surrounding the outlet of the compression port. The extension sub-valve is an annular leaf valve that seats away from the extension valve seat to open and close the extension port, The compression-side sub-valve is an annular leaf valve that seats away from the compression-side valve seat to open and close the compression-side port. The buffer according to feature 2.

4. The extension sub-valve and the compression sub-valve are composed of a single valve. The shock absorber according to feature 1.

5. The extension side main valve is an annular leaf valve, The compression-side main valve is an annular leaf valve, The inner diameter of the extension sub-valve is smaller than the inner diameter of the extension main valve. The inner diameter of the compression-side sub-valve is smaller than the inner diameter of the compression-side main valve. A buffer according to any one of claims 1 to 4.

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