Damper

Abstract

To provide a damper that can exhibit a hydraulic lock function, can be manufactured easily and can reduce manufacturing cost.SOLUTION: A damper D includes: a cylinder 1; a piston rod 2 inserted into the cylinder 1; a piston 3 that is coupled to the piston rod 2 and partitions inside of the cylinder 1 into an extension side chamber R1 and a compression side chamber R2; a reservoir R that stores liquid and gas and is communicated with the compression side chamber R2 to compensate a volume of the piston rod 2 entering / leaving inside of the cylinder 1; a movable partition 4 that is accommodated in the reservoir R so as to be vertically movable while a position above a liquid level S in the state where the piston 3 is located at a neutral position relative to the cylinder 1 is set as a movement lower limit and partitions inside of the reservoir R into an upper chamber U and a lower chamber L; a resistance element 5 that applies resistance to a flow of the liquid from the lower chamber L toward the upper chamber U; and a spring element 6 that energizes the movable partition 4 downwardly when the movable partition 4 ascends while abutting on the movable partition 4.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Conventionally, a shock absorber used in a vehicle includes, for example, a cylinder, a piston rod movably inserted into the cylinder, a piston connected to the tip of the piston rod and movably inserted into the cylinder to divide the inside of the cylinder into an extension side chamber and a compression side chamber, and an outer cylinder that covers the cylinder and forms a reservoir between the cylinder and the piston rod to compensate for the volume of the piston rod moving in and out of the cylinder.

[0003] In conventional shock absorbers constructed in this manner, it is common for a bump cushion rubber to be attached to the outer periphery of the piston rod that protrudes outward from the cylinder in order to cushion the impact at the time of maximum compression, and for this to collide with a bump cushion attached to the upper end of the cylinder. However, with the recent boom in sports utility vehicles, vehicle weights have been increasing year by year and the height of the center of gravity of the vehicles has been increasing. In order to reduce the vibration of the vehicle body during sudden braking or steering, there has been a demand for the use of an oil lock that uses hydraulic pressure that does not produce elastic rebound to cushion the impact at the end of the compression stroke.

[0004] In order to meet such demands, a shock absorber has been developed in which a sub-cylinder is provided in the compression side chamber so that when the piston descends within the cylinder, the space between the sub-cylinder and the cylinder functions as an oil lock chamber (see, for example, Patent Document 1).

[0005] In a shock absorber having an oil lock chamber inside the cylinder like this, in addition to the base valve that affects the flow of hydraulic oil from the compression side chamber to the reservoir during contraction, a valve is provided to adjust the characteristics of the oil lock, thereby preventing bottoming out and mitigating impact during maximum contraction. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2017-521618 Summary of the Invention [Problem to be solved by the invention]

[0007] A shock absorber equipped with an oil lock chamber can fully meet the above-mentioned demand for reducing the impact at the stroke end on the contraction side. However, the internal structure of the shock absorber is complex, and the fitting relationships between the parts required to achieve the oil lock function require high-precision dimensional control, and assembly is complicated, resulting in problems of high manufacturing costs and difficulty.

[0008] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a shock absorber that can exhibit a hydraulic lock function, and that can be easily manufactured at low cost. [Means for solving the problem]

[0009] In order to achieve the above object, the shock absorber of the present invention comprises a cylinder, a piston rod movably inserted into the cylinder in the axial direction, a piston connected to the piston rod and movably inserted into the cylinder to divide the inside of the cylinder into an extension side chamber filled with liquid and a compression side chamber, a reservoir that stores liquid and gas and is connected to the compression side chamber to compensate for the volume of the piston rod moving in and out of the cylinder, a movable partition that is housed in the reservoir movably in the vertical direction with a position above the liquid level when the piston is in a neutral position with respect to the cylinder as a lower movement limit, and divides the inside of the reservoir into an upper chamber and a lower chamber, a resistance element that provides resistance to the flow of liquid from the lower chamber to the upper chamber, and a spring element that urges the movable partition downward when the movable partition rises while in contact with the movable partition.

[0010] According to the shock absorber configured in this manner, when the piston moves from the neutral position relative to the cylinder in the contraction direction during contraction, if the liquid level in the reservoir reaches the movable partition, the damping force that impedes contraction is gradually increased as the contraction progresses, making it possible to alleviate the impact at the time of maximum contraction and prevent bottoming out. Also, by simply accommodating the movable partition and the spring element in the reservoir and providing a resistance element, it is possible to alleviate the impact at the time of maximum contraction in the shock absorber and prevent bottoming out, and since there is no need to provide a sub-cylinder within a cylinder and fit other parts into the sub-cylinder as in conventional shock absorbers, there is no need for highly accurate dimensional control, and the structure is simple, making assembly easy.

[0011] In addition, the movable partition may be in sliding contact with one of the cylinder and the outer tube and be movable in the up-down direction, and the resistance element may be formed by a gap between the other of the cylinder and the outer tube and the movable partition. With this shock absorber configured in this way, the movable partition can move smoothly within the reservoir without being interfered with by the cylinder or the outer tube, and even if the contraction continues after the liquid level reaches the movable partition, the damping force increases smoothly without a sudden change, thereby further improving the ride comfort of the vehicle.

[0012] Furthermore, the shock absorber may include an inlet passage and a return passage in which the resistance element is provided on the movable partition and which communicate between the upper chamber and the lower chamber, a valve that allows only the flow of liquid through the inlet passage from the lower chamber to the upper chamber and provides resistance to the flow of liquid, and a check valve that allows only the flow of liquid through the return passage from the upper chamber to the lower chamber. With a shock absorber configured in this manner, the characteristics of the shock absorber when the hydraulic lock function is exercised can be easily tuned by setting the valve, and the liquid that has moved to the upper chamber during the extension operation of the shock absorber can be quickly returned to the lower chamber, so that the liquid level in the lower chamber does not drop even if the shock absorber repeats extension and contraction operations, and the hydraulic lock function can be stably exercised when the shock absorber contracts to the vicinity of the stroke end.

[0013] In addition, the resistance element may be provided on the movable partition to communicate between the upper chamber and the lower chamber and may be formed to include a throttle passage that narrows toward the upper chamber. With this shock absorber configured in this manner, the rate of change in damping force before and after the hydraulic lock function is activated is further mitigated, so that the ride comfort of the vehicle can be further improved even when the hydraulic lock function is activated.

[0014] Furthermore, the movable partition may have a return flow path that communicates between the upper chamber and the lower chamber, that is blocked when it abuts against the spring element and that is opened when it separates from the spring element, and that faces the spring element with a gap in the vertical direction when it is located at the lower limit of movement. With this shock absorber configured in this way, the characteristics of the shock absorber when the hydraulic locking function is exerted can be easily tuned by setting the characteristics of the elastic force generated in response to compression of the spring element, and the liquid that has moved to the upper chamber during the extension operation of the shock absorber can be quickly returned to the lower chamber, so that the liquid level in the lower chamber does not drop even if the shock absorber repeats extension and contraction operations, and the hydraulic locking function can be stably exerted when the shock absorber contracts to the vicinity of the stroke end.

[0015] In addition, the spring element may be a rubber cushion. According to the shock absorber configured in this manner, when the shock absorber abuts against the movable partition, it tightly contacts the movable partition and can block the return flow path without leakage, so that the hydraulic lock function can be stably performed. Effect of the Invention

[0016] According to the shock absorber of the present invention, it is possible to exert a hydraulic locking function, and the manufacturing process is easy and the manufacturing costs can be reduced. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a cross-sectional view of a shock absorber according to one embodiment. [Diagram 2] FIG. 2 is a partially enlarged cross-sectional view of the shock absorber according to the embodiment. [Diagram 3] FIG. 4 is a partially enlarged cross-sectional view of a shock absorber according to a first modified example of an embodiment. [Figure 4]FIG. 11 is a partially enlarged cross-sectional view of a shock absorber according to a second modified example of the embodiment. [Diagram 5] FIG. 13 is a partially enlarged cross-sectional view of a shock absorber according to a third modified example of the embodiment. [Figure 6] FIG. 13 is a plan view of a movable partition of a shock absorber according to a third modified example of an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The shock absorber of the present invention will be described below with reference to the drawings. As shown in Fig. 1, the shock absorber D in one embodiment includes a cylinder 1, a piston rod 2 inserted into the cylinder 1, a piston 3 inserted into the cylinder 1 to divide the inside of the cylinder 1 into an extension side chamber R1 and a compression side chamber R2, a reservoir R for storing liquid and gas, a movable partition 4 housed in the reservoir R so as to be movable in the vertical direction and dividing the inside of the reservoir R into an upper chamber U and a lower chamber L, a resistance element 5 that provides resistance to the flow of liquid from the lower chamber L to the upper chamber U, and a spring element 6 housed in the upper chamber U and facing the upper end of the movable partition 4. The shock absorber D is interposed between the vehicle body and the wheels of a vehicle (not shown) and generates a damping force during expansion and contraction to suppress vibration of the vehicle body.

[0019] Each part of the shock absorber D will be described in detail below. The cylinder 1 is cylindrical, and as described above, the piston rod 2 and the piston 3 are inserted inside so as to be movable in the vertical direction in FIG. 1, which is the axial direction. The inside of the cylinder 1 is divided by the piston 3 into an expansion-side chamber R1 at the top in FIG. 1 and a compression-side chamber R2 at the bottom in FIG. 1. The expansion-side chamber R1 and the compression-side chamber R2 are filled with a liquid, specifically, hydraulic oil, for example. Note that the liquid may be water, an aqueous solution, or the like, in addition to hydraulic oil.

[0020] The cylinder 1 is accommodated in a bottomed cylindrical outer cylinder 7 arranged on the outer periphery, and a reservoir R is formed in the annular gap between the cylinder 1 and the outer cylinder 7. In this case, the reservoir R stores hydraulic oil as a liquid and gas. The gas filled in the reservoir R is an inert gas such as nitrogen to prevent deterioration of the hydraulic oil, but may be other gas. In this embodiment, the reservoir R is formed between the cylinder 1 and the outer cylinder 7, but the reservoir R may be formed by a tank provided separately from the cylinder 1.

[0021] The piston rod 2 is inserted into the cylinder 1 at its tip end through the inner circumference of an annular rod guide 8 that fits into the upper end of the cylinder 1 in FIG. 1, and its upper end in FIG. 1, which is the base end, protrudes outward from the cylinder 1. The rod guide 8 is annular and has a flange 8a on its outer circumference. The outer circumference of the flange 8a fits into the inner circumference of the upper end of the outer tube 7 while a portion with a smaller diameter than the flange 8a fits into the inner circumference of the upper end of the cylinder 1, thereby closing off the upper ends of the cylinder 1 and the outer tube 7. The rod guide 8 also makes sliding contact with the outer circumference of the piston rod 2 to guide the axial movement of the piston rod 2 inserted into the inner circumference side relative to the cylinder 1. An annular seal member 9 that is inserted between the piston rod 2 and the outer tube 7 is stacked above the rod guide 8 in FIG. 1. The seal member 9 seals the gap between the piston rod 2 and the outer tube 7 to prevent leakage of liquid and gas from the cylinder 1 and the outer tube 7.

[0022] The piston 3 is provided with an extension-side passage 3a and a compression-side passage 3b which communicate between the extension-side chamber R1 and the compression-side chamber R2, an extension-side damping valve 3c which is provided in the extension-side passage 3a and which allows only the flow of hydraulic oil from the extension-side chamber R1 to the compression-side chamber R2 and which provides resistance to the flow of hydraulic oil, and a compression-side check valve 3d which is provided in the compression-side passage 3b and which allows only the flow of hydraulic oil from the compression-side chamber R2 to the extension-side chamber R1.

[0023] 1, a valve case 10 is fitted to the lower end of the cylinder 1, which is placed on the bottom of the outer tube 7. The valve case 10 is provided with a flange 10a on the outer periphery of the lower end in FIG. 1, which fits into the inner periphery of the outer tube 7 and abuts against the lower end of the cylinder 1, and is inserted into the outer tube 7 together with the seal member 9, rod guide 8, and cylinder 1, and is fixed inside the outer tube 7 by being sandwiched between a cap 11, which is screwed to the upper end of the outer tube 7, and the bottom of the outer tube 7.

[0024] In addition, the valve case 10 separates the compression side chamber R2 from the reservoir R, and is equipped with a discharge passage 10b and a suction passage 10c that communicate between the compression side chamber R2 and the reservoir R, a compression side damping valve 10d that is provided in the discharge passage 10b and allows only the flow of hydraulic oil from the compression side chamber R2 to the reservoir R and provides resistance to the flow of hydraulic oil, and an extension side check valve 10e that is provided in the suction passage 10c and allows only the flow of hydraulic oil from the reservoir R to the compression side chamber R2.

[0025] 1 relative to the cylinder 1, the hydraulic oil in the extension side chamber R1, which is contracted by the movement of the piston 3, passes through the extension side damping valve 3c and moves to the expansion side chamber R2, and the pressure in the extension side chamber R1 rises as the extension side damping valve 3c applies resistance to the hydraulic oil flow, generating a damping force that impedes the extension operation. Also, during the extension operation of the shock absorber D, the piston rod 2 retreats from the cylinder 1, and the hydraulic oil equivalent to the volume of the piston rod 2 retreating from the cylinder 1 is supplied from the reservoir R to the cylinder 1 via the extension side check valve 10e.

[0026] In addition, in the shock absorber D, during contraction operation in which the piston 3 moves downward in FIG. 1 relative to the cylinder 1, the hydraulic oil in the compression side chamber R2, which is reduced by the movement of the piston 3, moves through the compression side check valve 3d to the expansion side chamber R1, and since the compression side check valve 3d does not provide much resistance to the flow of hydraulic oil, the pressures in the expansion side chamber R1 and the compression side chamber R2 become approximately equal. During contraction operation of the shock absorber D, the piston rod 2 enters the cylinder 1, and the hydraulic oil in the cylinder 1 becomes excessive by the volume of the piston rod 2 entering the cylinder 1, so the excess hydraulic oil passes through the compression side damping valve 10d and is discharged to the reservoir R. In this way, when the hydraulic oil is discharged from the cylinder 1 to the reservoir R, the pressures in the expansion side chamber R1 and the compression side chamber R2 rise approximately equally because the compression side damping valve 10d provides resistance to the flow of hydraulic oil. Here, since the pressure-receiving area receiving the pressure of the compression-side chamber R2 of the piston 3 is larger than the pressure-receiving area receiving the pressure of the extension-side chamber R1 of the piston 3 by the cross-sectional area of ​​the piston rod 2, the force pushing up the piston 3 increases due to the increase in pressure in the extension-side chamber R1 and the compression-side chamber R2, and the shock absorber D generates a damping force that hinders the contraction operation.

[0027] In this way, when shock absorber D expands and contracts due to input of vibration, it generates a damping force that prevents the expansion and contraction. In addition, reservoir R compensates for the volume of piston rod 2 moving in and out of cylinder 1 by exchanging hydraulic oil with cylinder 1 in accordance with the expansion and contraction of shock absorber D.

[0028] 1 within the reservoir R formed between the cylinder 1 and the outer tube 7. The movable partition 4 has an annular shape and is housed therein so as to be movable up and down in Fig. 1. The movable partition 4 has an inner periphery that is in sliding contact with the outer periphery of the cylinder 1 and an outer periphery that faces the inner periphery of the outer tube 7 with a small gap therebetween, thereby dividing the inside of the reservoir R into an upper chamber U and a lower chamber L.

[0029] The movable partition 4 also has a number of grooves 4a on its outer periphery that run from the upper end to the lower end in FIG. 2. The gap between the outer periphery of the movable partition 4 in which the grooves 4a are formed and the inner periphery of the outer cylinder 7 functions as a restricting flow path that connects the upper chamber U and the lower chamber L in the reservoir R, and forms a resistance element 5 that provides resistance to the flow of hydraulic oil moving between the upper chamber U and the lower chamber L. Therefore, the magnitude of the resistance that the resistance element 5 provides to the flow of hydraulic oil passing through it can be tuned by changing the cross-sectional area and the number of grooves 4a installed on the outer periphery of the movable partition 4. Depending on the magnitude of the resistance, the resistance element 5 may be formed in the gap between the movable partition 4 and the outer cylinder 7 without providing the grooves 4a.

[0030] Furthermore, the movable partition 4 is provided with rod-shaped legs 4b extending downward from the lower end. Since the movable partition 4 is provided with the legs 4b, when the legs 4b come into contact with the upper end of the flange 10a of the valve case 10 inside the reservoir R, further movement downward in FIG. 1 with respect to the reservoir R is restricted.

[0031] 1 within the reservoir R, a lower limit of movement is set as the lower limit of the range of movement within the reservoir R by the foot 4b. The lower limit of movement is set to a position above the liquid level S within the reservoir R when the piston 3 is in a neutral position relative to the cylinder 1. The neutral position may be the center of the stroke of the piston 3 relative to the cylinder 1, or may be the position where the piston 3 is located relative to the cylinder 1 when the shock absorber D is installed between the body and wheels of a vehicle.

[0032] The movable partition 4 is expected to prevent further contraction of the shock absorber D by increasing the pressure in the cylinder 1 together with the pressure in the lower chamber L by passing the resistance element 5 from the lower chamber L to the upper chamber U a little before the shock absorber D contracts and the piston 3 reaches the stroke end, so that the lower limit of movement of the movable partition 4 is preferably set at a position where the liquid level S of the hydraulic oil reaches the movable partition 4 a little before the shock absorber D is fully contracted. When the shock absorber D contracts, the piston rod 2 enters the cylinder 1, discharging the hydraulic oil into the reservoir R and the liquid level S of the hydraulic oil rises in the reservoir R, but it is preferable to prevent the liquid level S from reaching the lower limit of movement even if the shock absorber D contracts due to vibration input while the vehicle is traveling on a good road with few bumps.

[0033] In addition, as long as the lower limit of movement of the movable partition 4 can be set by abutting against the outer tube 7 or the flange 10a of the valve case 10, the foot 4b may be annular in shape other than rod-shaped, and the shape and structure can be designed as desired.

[0034] Furthermore, although the movable partition 4 is provided with the legs 4b to set the lower limit of movement of the movable partition 4, a stopper may be provided on the cylinder 1 or the outer tube 7 so that when the movable partition 4 moves downward from above and reaches the lower limit of movement, it comes into contact with the stopper and restricts the movement of the movable partition 4 below the lower limit of movement. The stopper may be formed by providing an annular groove on the outer periphery of the cylinder 1 or the inner periphery of the outer tube 7, and may be constituted by a C-ring or the like that is fitted into the annular groove.

[0035] A spring element 6 is provided in the upper chamber U above the movable partition 4, facing the end of the movable partition 4 on the upper chamber U side in the axial direction. The spring element 6 includes a coil spring 6a and a cylindrical spring bearing 6b disposed between the coil spring 6a and the movable partition 4, and is disposed between the flange 8a of the rod guide 8 and the movable partition 4. As shown in FIG. 1, the spring bearing 6b includes a cylindrical portion 6b1 that slides against the outer periphery of the cylinder 1, and a flange-shaped bearing portion 6b2 that is provided on the outer periphery of the upper end of the cylindrical portion 6b1 and supports the lower end of the coil spring 6a in FIG. 1. The lower end of the cylindrical portion 6b1 is brought into contact with the upper end in FIG. 1, which is the end of the movable partition 4 on the upper chamber U side, to transmit the elastic force generated by the coil spring 6a to the movable partition 4. In addition, the spring element 6 positions the movable partition 4 at the lower limit of movement with the biasing force generated by the coil spring 6a, and when the movable partition 4 is displaced upward from the lower limit of movement toward the upper chamber U in Figure 1, the spring element 6 biases the movable partition 4 in the direction returning it to the lower limit of movement in accordance with the displacement.

[0036] 1, the spring element 6 is arranged in the upper chamber U with the coil spring 6a on top and the spring bearing 6b on the bottom, but it may be arranged with the coil spring 6a on the bottom and the spring bearing 6b on the top. In this embodiment, when the coil spring 6a is maximally compressed to the tight length by the movement of the movable partition 4 upward in FIG. 1, the spring element 6 also functions as a stopper that restricts the movable partition 4 from moving further upward and sets the upper limit of movement. Therefore, the movable partition 4 can move up and down in FIG. 1 within the reservoir R within a range from the lower limit of movement to the upper limit of movement where the coil spring 6a is the tight length.

[0037] In addition, the lower end of the spring element 6 may face the end of the movable partition 4 on the upper chamber U side with a gap therebetween when the movable partition 4 is located at the lower limit of movement, as long as the coil spring 6a can urge the movable partition 4 toward the lower chamber L side by abutting against the movable partition 4 before the movable partition 4 maximally compresses the upper chamber U. The spring bearing 6b functions as a spacer and can transmit the urging force to the movable partition 4 even if the length of the coil spring 6a is insufficient, but can be omitted if unnecessary. Therefore, it is sufficient for the spring element 6 to urge the movable partition 4 downward when the movable partition 4 rises in the reservoir R while in contact with the movable partition 4.

[0038] Moreover, since the spring element 6 only needs to come into contact with the movable partition 4 before the movable partition 4 maximally compresses the upper chamber U and urge the movable partition 4 toward the lower chamber L, it may be a laminate of wave washers or disc springs other than a coil spring, or may be an elastic body such as rubber. Furthermore, although the spring element 6 is housed in the upper chamber U as described above, it may be housed in the lower chamber L and connected to the movable partition 4, and may extend when the movable partition 4 moves upward in FIG. 1 to urge the movable partition 4 downward.

[0039] The shock absorber D is configured as described above, and its operation will be described below. As described above, when the shock absorber D performs an expansion / contraction operation, a damping force is generated, but when the shock absorber D performs a contraction operation in which the piston 3 moves downward in FIG. 1 relative to the cylinder 1, the piston rod 2 enters the cylinder 1, and the hydraulic oil is discharged to the reservoir R through the discharge passage 10b. Therefore, when the shock absorber D performs a contraction operation, the hydraulic oil flows into the reservoir R, and the liquid level S of the hydraulic oil in the reservoir R rises.

[0040] When the piston 3 is in a neutral position in the cylinder 1, the liquid level S in the reservoir R is located below the lower surface of the movable partition 4, which is located at the lower limit of its movement as shown in Figure 1. However, as the piston 3 descends relative to the cylinder 1, the liquid level S rises, and as the piston 3 continues to descend, it eventually reaches the movable partition 4.

[0041] The gas in the reservoir R can move from the lower chamber L to the upper chamber U without encountering much resistance through the resistance element 5 formed by the groove 4a, but the hydraulic oil encounters resistance when passing through the resistance element 5. Therefore, when the liquid level S reaches the movable partition 4 due to the contraction operation of the shock absorber D, the hydraulic oil passes through the resistance element 5 and moves from the lower chamber L separated by the movable partition 4 to the upper chamber U, and the pressure in the lower chamber L increases as the resistance element 5 provides resistance to the flow of the hydraulic oil. Since the pressure in the lower chamber L increases, the pressure in the cylinder 1 also increases, and the shock absorber D generates a higher damping force than before the liquid level S reached the movable partition 4, preventing its own contraction.

[0042] In addition, the pressure in the lower chamber L becomes higher than the pressure in the upper chamber U, and the coil spring 6a contracts until the biasing force of the spring element 6 pressing the movable partition 4 downward in FIG. 1 and the force pressing the movable partition 4 upward in FIG. 1 due to the pressure difference between the pressure in the lower chamber L and the pressure in the upper chamber U are balanced, so that the movable partition 4 moves upward in FIG. 1 in the reservoir R. Therefore, the movable partition 4 rises in the reservoir R while providing resistance to the flow of hydraulic oil by the resistance element 5 according to the amount of downward movement of the piston 3 from the neutral position relative to the cylinder 1. Since the pressure in the lower chamber L increases depending on the biasing force of the spring element 6, when the liquid level S reaches the movable partition 4, the greater the displacement amount of the piston 3 from the neutral position relative to the cylinder 1, the higher the damping force generated by the shock absorber D.

[0043] When the piston 3 is displaced downward relative to the cylinder 1 to the vicinity of the stroke end, the coil spring 6a is fully compressed to the tight length, restricting further rise of the movable partition 4, so that the movable partition 4 cannot be pushed up by an increase in pressure in the lower chamber L to expand the lower chamber L. Then, as the shock absorber D contracts, the entire flow rate of the hydraulic oil that has flowed into the reservoir R passes through the resistance element 5, the pressure in the lower chamber L increases, and the shock absorber D exerts a hydraulic lock function to generate a higher damping force and prevent contraction, thereby reducing the moving speed of the piston 3 relative to the cylinder 1 and mitigating the impact at the time of maximum contraction.

[0044] In this way, during the contraction operation in which the piston 3 moves downward relative to the cylinder 1 in Figure 1, the liquid level S reaches the lower limit of movement of the movable partition 4, and when the piston 3 then moves downward in Figure 1, the hydraulic locking function is exerted, and the damping force is gradually increased by the resistance element 5 as the movement of the piston 3 increases, and when the upward movement of the movable partition 4 becomes restricted, the damping force is increased to its highest level, thereby absorbing impact and preventing bottoming out.

[0045] When the shock absorber D contracts, the movable partition 4 moves upward in the reservoir R, and hydraulic oil moves from the lower chamber L to the upper chamber U through the resistance element 5. Then, when the direction of extension of the shock absorber D changes and the shock absorber D expands, the piston rod 2 retreats from the cylinder 1, and hydraulic oil moves from the reservoir R into the cylinder 1, reducing the pressure in the lower chamber L. In addition, the movable partition 4 is pressed downward by the urging force of the spring element 6, so it moves downward in the reservoir R and returns to its lower limit, and the liquid that flowed into the upper chamber U is returned to the lower chamber L through the resistance element 5.

[0046] Furthermore, if the movable partition 4 is set to reach its upper limit of movement before the shock absorber D fully contracts, the damping force can be maximized before the shock absorber D reaches the stroke end on the contraction side, effectively mitigating the impact of the shock absorber D and preventing bottoming out. However, it is also possible to not restrict the upward movement of the movable partition 4 even when the shock absorber D reaches the stroke end on the contraction side.

[0047] In addition, in the shock absorber D of this embodiment, the coil spring 6a at the tight length is made to function as a stopper to set the upper limit of movement of the movable partition 4, but a stopper may be provided on the cylinder 1 or the outer tube 7 to abut against the movable partition 4 when the movable partition 4 reaches the upper limit of movement, thereby preventing the movable partition 4 from moving upward beyond the upper limit. The stopper may be formed of a ring-shaped groove provided on the outer periphery of the cylinder 1 or the inner periphery of the outer tube 7, and a C-ring or the like that is fitted into the ring-shaped groove.

[0048] As described above, the shock absorber D of this embodiment includes a cylinder 1, a piston rod 2 inserted into the cylinder 1 so as to be axially movable, a piston 3 connected to the piston rod 2 and movably inserted into the cylinder 1 to divide the inside of the cylinder 1 into an extension side chamber R1 filled with hydraulic oil (liquid) and a compression side chamber R2, a reservoir R that stores the hydraulic oil (liquid) and gas and is connected to the compression side chamber R2 to compensate for the volume of the piston rod 2 moving in and out of the cylinder 1, a movable partition 4 that is housed in the reservoir R so as to be movably in the vertical direction with a position above the liquid level S when the piston 3 is in a neutral position with respect to the cylinder 1 as a lower movement limit, and divides the inside of the reservoir R into an upper chamber U and a lower chamber L, a resistance element 5 that provides resistance to the flow of liquid from the lower chamber L to the upper chamber U, and a spring element 6 that urges the movable partition 4 downward when the movable partition 4 rises while in contact with the movable partition 4.

[0049] In the shock absorber D configured as above, when the piston 3 moves from the neutral position to the cylinder 1 in the contraction direction during the contraction operation, when the liquid level S in the reservoir R reaches the movable partition 4, the damping force that prevents the contraction is gradually increased as the contraction progresses, making it possible to alleviate the impact at the time of maximum contraction and prevent bottoming out. In addition, in the shock absorber D of this embodiment, it is possible to alleviate the impact at the time of maximum contraction and prevent bottoming out simply by accommodating the movable partition 4 and the spring element 6 in the reservoir R and providing the resistance element 5, and since it is not necessary to provide a sub-cylinder in the cylinder and fit other parts into the sub-cylinder as in the conventional shock absorber, there is no need for highly accurate dimensional control, and the structure is simple, so assembly is easy, and the manufacturing cost can be reduced and the difficulty of manufacturing is easy. Therefore, according to the shock absorber D of this embodiment, the hydraulic lock function can be exhibited, and the manufacturing cost can be reduced by making the manufacturing easy. Furthermore, in the shock absorber D of this embodiment, when the liquid level S reaches the movable partition 4 and continues to contract, the shock absorber D gradually increases the damping force to suppress the contraction, thereby mitigating the sudden change in damping force generated by the shock absorber D before and after the hydraulic locking function is activated, and the ride comfort of the vehicle is not impaired by the activation of the hydraulic locking function.

[0050] In addition, the movable partition 4 in the shock absorber D of this embodiment is in sliding contact with the outer periphery of the cylinder 1 and can move in the vertical direction, and the resistance element 5 is formed by the gap between the movable partition 4 and the outer cylinder 7. According to the shock absorber D configured in this manner, the movable partition 4 is in sliding contact only with the outer periphery of the cylinder 1, and the resistance element 5 is formed by the gap between the movable partition 4 and the outer cylinder 7. Therefore, the movable partition 4 can move smoothly in the reservoir R without being interfered with by the outer cylinder 7, and even if the liquid level S reaches the movable partition 4 and continues to contract, the damping force does not change suddenly and increases smoothly, which further improves the ride comfort of the vehicle. In this embodiment, the resistance element 5 is formed by the gap between the outer periphery of the movable partition 4 in which the groove 4a is provided and the outer cylinder 7, so the resistance that the resistance element 5 gives to the flow of the hydraulic oil can be easily tuned by the cross-sectional area of ​​the groove 4a and the number of grooves 4a installed. In addition, the groove 4a is provided along the axial direction on the outer periphery of the movable partition 4, but depending on the characteristics when exerting the hydraulic locking function, it may be provided in a spiral shape, a serpentine shape, or an inclined shape in the axial direction.

[0051] As described above, the movable partition 4 is in sliding contact with the outer periphery of the cylinder 1 and can move in the vertical direction, and the resistance element 5 is formed by the gap between the outer tube 7 and the movable partition 4, but the outer periphery of the movable partition 4 may be in sliding contact with the inner periphery of the outer tube 7, and the resistance element 5 may be formed by the gap between the inner periphery of the cylinder 1 and the inner periphery of the movable partition 4.

[0052] As described above, when the movable partition 4 moves upward in the reservoir R in a direction that compresses the upper chamber U, the spring element 6 increases the downward biasing force, so that the characteristics of the damping force when the shock absorber D functions as a hydraulic lock relative to the stroke amount toward the contraction side of the shock absorber D can be tuned by the characteristics of the biasing force of the spring element 6. Therefore, for example, if it is desired to increase the slope of the characteristics of the damping force when the shock absorber D functions as a hydraulic lock when the shock absorber D strokes toward the contraction side, the biasing force of the spring element 6 may be increased from the middle as the compression of the spring element 6 progresses. Specifically, when the biasing force of the spring element 6 is increased from the middle as the compression of the spring element 6 progresses, the coil spring 6a may be a spring with different pitches at the top and bottom, or the spring element 6 may be configured by arranging two springs with different pitches in series, and the spring or portion with the narrower pitch may be set to the solid length first, or the spring element 6 may be configured by two coil springs arranged in parallel with different lengths.

[0053] Furthermore, as in the shock absorber D1 of the first modification shown in Fig. 3, the resistance element 5a may be provided on the movable partition 15, and the upper chamber U and the lower chamber L may be communicated with each other, and the movable partition 15 may be formed including a throttle passage 15a that narrows toward the upper chamber U. In detail, the movable partition 15 is annular, and the inner periphery of the movable partition 15 is in sliding contact with the outer periphery of the cylinder 1 to be movable in the vertical direction in the reservoir R, dividing the reservoir R into the upper chamber U and the lower chamber L. The movable partition 15 is provided with a throttle passage 15a on the outer periphery of the movable partition 15 whose cross-sectional area becomes smaller toward the upper side in Fig. 3 along the axial direction, and the outer periphery of the movable partition 15 is in sliding contact with the inner periphery of the outer cylinder 7. The movable partition 15 has a lower limit of movement set by a stopper 14 fixed to the outer periphery of the cylinder 1, and is biased downward in Fig. 3 by a spring element 6.

[0054] When the movable partition 15 is housed in the reservoir R, the upper chamber U and the lower chamber L are connected through the throttle passage 15a of the movable partition 15, and the throttle passage 15a forms a resistance element 5a that applies a pressure to the flow of hydraulic oil from the lower chamber L to the upper chamber U. The cross-sectional area of ​​the throttle passage 15a becomes smaller toward the upper chamber U, so that the throttle passage 15a becomes narrower toward the upper chamber U. Therefore, when the shock absorber D1 contracts and the liquid level S reaches the movable partition 15 and the contraction continues, the hydraulic oil passes through the throttle passage 15a that forms the resistance element 5a and moves from the lower chamber L to the upper chamber U, but the resistance that the hydraulic oil receives from the throttle passage 15a before moving toward the upper chamber U gradually increases the closer it moves toward the upper chamber U. Therefore, according to the shock absorber D1 of the first modification equipped with the movable partition 15 configured as above, the change rate of the damping force before and after the hydraulic lock function is exercised is further mitigated, so that the ride comfort of the vehicle can be further improved even when the hydraulic lock function is exercised. The throttle passage 15a is easy to process when it is formed on the outer periphery of the movable partition 15, but it may be provided on the inner periphery or inside the movable partition 15. The movable partition 15 is in sliding contact with the cylinder 1 and the outer tube 7, but it may be in sliding contact with one of the cylinder 1 or the outer tube 7 and be in non-contact with the other of the cylinder 1 or the outer tube 7 with a small gap therebetween. Furthermore, if the throttle passage 15a is provided in a spiral shape on the inner or outer periphery of the movable partition 15, the passage length can be secured, the rate of decrease in the cross-sectional area of ​​the passage can be made gentle, and the change rate of the damping force can be further mitigated. As shown in FIG. 3, the throttling passage 15a may have a depth that becomes shallower toward the upper chamber U, so that the cross-sectional area becomes smaller toward the upper chamber U, or the width along the circumferential direction of the movable partition 15 may become narrower toward the upper chamber U, so that the cross-sectional area becomes smaller toward the upper chamber U.

[0055] Furthermore, like the shock absorber D2 of the second modified example shown in FIG. 4, the resistance element 5b may include an inflow passage 16a and a return passage 16b provided in the movable partition 16 and communicating the upper chamber U with the lower chamber L, a valve 17 that allows only the flow of hydraulic oil through the inflow passage 16a from the lower chamber L to the upper chamber U and provides resistance to the flow of hydraulic oil, and a check valve 18 that allows only the flow of hydraulic oil through the return passage 16b from the upper chamber U to the lower chamber L.

[0056] More specifically, the movable partition 16 is annular and housed within the reservoir R, dividing the reservoir R into an upper chamber U and a lower chamber L, and is provided with an inlet passage 16a and a return passage 16b that connect the upper chamber U and the lower chamber L from the upper end to the lower end.

[0057] The valve 17 is formed of multiple annular plates stacked on the upper end of the movable partition 16 in Fig. 4, and the inner periphery is fixed in a stacked state on the movable partition 16 by a holder 19, while the outer periphery is allowed to flex, so that the upper end of the inflow passage 16a in Fig. 4 can be opened and closed. When the valve 17 flexes under pressure from the lower chamber L, it opens the inflow passage 16a, forcing the flow of hydraulic oil from the lower chamber L to the upper chamber U, and providing resistance to the flow of the hydraulic oil. The number of annular plates constituting the valve 17 can be changed as desired.

[0058] The check valve 18 is formed of an annular plate that is stacked on the lower end of the movable partition 16 in Fig. 4, and its inner periphery is fixed in a stacked state on the movable partition 16 by a holder 19, while its outer periphery is allowed to flex, so that the lower end of the return passage 16b in Fig. 4 can be opened and closed. The check valve 18 has a hole 18a that does not block the inflow passage 16a even when the entire check valve 18 abuts against the lower end of the movable partition 16.

[0059] Furthermore, when the check valve 18 is deflected by pressure from the upper chamber U, it opens the return passage 16b to allow the flow of hydraulic oil from the upper chamber U to the lower chamber L, without providing significant resistance to the flow of hydraulic oil. The number of annular plates constituting the check valve 18 can be changed as desired.

[0060] The holder 19 is cylindrical and has a pair of support parts 19a, 19b facing each other in the up-down direction on the outer periphery of the upper and lower ends, and holds the valve 17, movable partition 16, and check valve 18 by sandwiching them between the support parts 19a, 19b. The valve 17 and check valve 18 held by the holder 19 in this manner are fixed on the inner periphery and allowed to flex on the outer periphery, thereby opening and closing the corresponding inlet passage 16a and return passage 16b.

[0061] In this way, the assembly of the integrated valve 17, movable partition 16, check valve 18 and holder 19 is contained within the reservoir R with the inner circumference of the holder 19 in sliding contact with the outer circumference of the cylinder 1 and the outer circumference of the movable partition 16 in sliding contact with the inner circumference of the outer tube 7, and the lower limit of movement is set by a stopper 14 fixed to the outer circumference of the cylinder 1, and the assembly is urged downward in Figure 4 by a spring element 6.

[0062] Then, when the shock absorber D2 contracts and continues to contract even after the liquid level S reaches the movable partition 16, the hydraulic oil pushes open the valve 17 in the resistance element 5b, passes through the inflow passage 16a, and moves from the lower chamber L to the upper chamber U, and the valve 17 provides resistance to the flow of the hydraulic oil. Thus, according to the shock absorber D2 of the second modified example configured in this manner, the valve 17 provides resistance to the flow of the hydraulic oil to provide a hydraulic lock function, and the characteristics of the shock absorber D2 when the hydraulic lock function is provided can be easily tuned by setting the bending stiffness of the valve 17. Also, after the shock absorber D2 contracts and provides the hydraulic lock function, when the direction of expansion and contraction of the shock absorber D2 changes and switches to the extension operation, the pressure in the lower chamber L is reduced and the check valve 18 opens, so that the hydraulic oil that has flowed into the upper chamber U is quickly returned to the lower chamber L with almost no resistance. Therefore, according to the second modified example of the shock absorber D2, the hydraulic oil (liquid) that moves to the upper chamber U during the extension operation of the shock absorber D2 can be quickly returned to the lower chamber L, so that the liquid level S of the hydraulic oil (liquid) in the lower chamber L does not drop even if the shock absorber D2 repeats extension and contraction operations, and the hydraulic locking function can be stably performed when the shock absorber D2 contracts near the stroke end.

[0063] In addition, in the second modified example of shock absorber D2, the movable partition 16, valve 17 and check valve 18 are integrated by holder 19, but the spring element 6 may be formed by a coil spring that sandwiches these from above and below, so that the spring element 6 allows the movable partition 16, valve 17 and check valve 18 to move in the vertical direction without losing their integrity.

[0064] Furthermore, in this embodiment, the return passage 16b is provided in the movable partition 16 and opened and closed by the check valve 18, but the return passage and check valve for returning the hydraulic oil in the upper chamber U to the lower chamber L may have other structures. For example, when the return passage from the upper chamber U to the lower chamber L is the gap between the movable partition 16 and the outer cylinder 7, an annular groove may be provided on the outer periphery of the movable partition 16, and an annular check valve that can move up and down within the annular groove may be accommodated. In this case, the check valve is annular, and the outer periphery is in sliding contact with the inner periphery of the outer cylinder 7, and the check valve is inserted into the annular groove on the outer periphery of the movable partition 16 so as to be movable up and down, and has a passage consisting of a vertical groove on the inner periphery that communicates the upper end and the lower end, and a horizontal groove formed along the radial direction at the lower end that communicates the vertical groove with the outer periphery. When the pressure in the lower chamber L is higher than the pressure in the upper chamber U, the check valve configured in this manner moves to the uppermost position within the annular groove and brings its upper end into contact with the upper side wall of the annular groove, thereby blocking the passage consisting of the vertical groove and horizontal groove and preventing the hydraulic oil from moving from the lower chamber L to the upper chamber U through the space between the movable partition 16 and the outer cylinder 7. When the pressure in the upper chamber U is higher than the pressure in the lower chamber L, the check valve moves to the lowermost position within the annular groove and brings its lower end into contact with the lower side wall of the annular groove, thereby opening the passage consisting of the vertical groove and horizontal groove and allowing the hydraulic oil to move from the upper chamber U to the lower chamber L through the space between the movable partition 16 and the outer cylinder 7.

[0065] Furthermore, as in the third modified example of shock absorber D3 shown in Figure 5, the spring element is a rubber cushion 20, and the movable partition 21 has a return flow path P that connects the upper chamber U and the lower chamber L and is blocked when it abuts against the cushion 20 and is opened when it moves away from the cushion 20, and may face the cushion 20 with a gap in the vertical direction when positioned at the lower limit of movement.

[0066] More specifically, as shown in Figures 5 and 6, the movable partition 21 is annular and has a protrusion 21a provided circumferentially at the center of the outer periphery, a notch 21b formed along the axial direction from the lower end to the center of the protrusion 21a, a groove 21c provided axially on the outer periphery of the protrusion 21a and leading to the notch 21b, six protrusions 21d protruding radially from the inner periphery, and a return flow path P formed by the gaps between the protrusions 21d, and is housed within the reservoir R so as to be movable up and down in Figure 5, dividing the interior of the reservoir R into an upper chamber U and a lower chamber L.

[0067] The movable partition 21 has the tip of each ridge 21d in sliding contact with the outer periphery of the cylinder 1, and the outer periphery of the ridge 21a faces the outer periphery of the outer cylinder 7 through a very small gap, and communicates the upper chamber U with the lower chamber L through the groove 21c and the notch 21b, and also communicates the upper chamber U with the lower chamber L through the return flow path P formed by the gap between the ridges 21d, 21d. The cross-sectional area of ​​the notch 21b is larger than that of the groove 21c, and the hydraulic oil is given a large resistance when passing through the groove 21c when passing between the movable partition 21 and the outer cylinder 7. Therefore, in this case, the resistance element 5c is formed by the groove 21c. The flow path area of ​​the return flow path P is ensured to be sufficient so as not to provide resistance to the flow of the hydraulic oil passing through. The cross-sectional area and number of grooves 21c can be arbitrarily changed in design, and the notches 21b can also be eliminated as long as the upper chamber U and the lower chamber L can be communicated with each other only by the grooves 21c.

[0068] In the case of the shock absorber D3 of the third modification, the outer cylinder 7 has a protrusion 7a that protrudes inward by crimping a portion slightly above the center in the axial direction from the outer periphery, and when the lower side of the protrusion 21a of the movable partition 21 abuts against the protrusion 7a, the further downward movement of the movable partition 21 in FIG. 5 is restricted. In this way, the protrusion 7a on the outer cylinder 7 functions as a stopper that restricts the downward movement of the movable partition 21 and sets the lower limit of the movement of the movable partition 21. In addition, by providing a large number of notches 21b in the movable partition 21 in a circumferential direction, the contact area of ​​the movable partition 21 that abuts against the protrusion 7a can be reduced, and the hitting sound when the movable partition 21 returns to the lower limit of movement and contacts the protrusion 7a can be reduced. In addition, the protrusion 7a may be provided in a ring shape in the circumferential direction of the outer cylinder 7, or may be provided at multiple locations spaced apart in the circumferential direction as shown in the figure, or may be provided at only one location as long as it can function as a stopper.

[0069] Moreover, shock absorber D3 in the third modified example includes a support cylinder 22 that is attached to rod guide 8 and supports the upper end of cushion 20. Support cylinder 22 includes a cylinder portion 22a that is disposed on the outer periphery of cylinder 1 and a receiving portion 22b that is provided at the lower end of cylinder portion 22a, and is attached to rod guide 8 by fitting the upper end of cylinder portion 22a into the outer periphery below flange 8a of rod guide 8. Receiving portion 22b is attached to the lower end of cylinder portion 22a, and the inner diameter increases downward in FIG.

[0070] The cushion 20 is made of rubber and molded into a cylindrical shape, has tapered chamfered portions 20a, 20b on the inner circumference of the upper and lower open ends, and is fitted with a slight tightening margin onto the outer circumference of the cylinder 1. When the cushion 20 is disposed at the lower limit where the movable partition 21 abuts against the protrusion 7a and its downward movement is restricted, the cushion 20 faces the upper end of the movable partition 21 with a small gap in the axial direction.

[0071] Therefore, when the movable partition 21 is positioned at the lower limit of movement, a gap is formed between the cushion 20 and the movable partition 21, and the opening at the upper end of the return flow path P formed by the gap between the protrusions 21d, 21d of the movable partition 21 is opened, communicating the upper chamber U with the lower chamber L. On the other hand, when the movable partition 21 receives pressure from the lower chamber L as the liquid level S rises and moves upward in Fig. 5, the upper end surface of the movable partition 21 comes into contact with the lower end surface of the cushion 20, blocking the return flow path P and cutting off communication between the upper chamber U and the lower chamber L via the return flow path P.

[0072] When the shock absorber D3 of the third modified example configured in this manner contracts and the liquid level S rises, the liquid level S eventually reaches the movable partition 21 located at the lower limit of movement. Then, if the contraction continues even after the liquid level S reaches the movable partition 21, the hydraulic oil passes through the resistance element 5c formed by the return flow path P and the groove 21c and moves from the lower chamber L to the upper chamber U because the cushion 20 and the movable partition 21 are separated. When the cushion 20 and the movable partition 21 are separated, the movable partition 21 does not receive a biasing force from the cushion 20, so that the pressure in the lower chamber L rises slightly higher than the pressure in the upper chamber U due to the resistance given when the hydraulic oil passes through the return flow path P, and the movable partition 21 moves upward in FIG. 5 and comes into contact with the cushion 20.

[0073] When the movable partition 21 abuts against the cushion 20, the return flow path P is blocked, and the liquid in the lower chamber L moves to the upper chamber U through only the resistance element 5c. The resistance that the resistance element 5c provides to the flow of hydraulic oil increases the pressure in the lower chamber L, and the increased pressure in the lower chamber L moves the movable partition 21 upward, compressing the cushion 20.

[0074] As the movable partition 21 rises in Figure 5 and compresses the cushion 20, the spring force of the cushion 20 increases exponentially with the amount of compression, suppressing the rise of the movable partition 21. Meanwhile, the pressure in the lower chamber L also increases in accordance with the spring force of the cushion 20, so that as the contraction of the shock absorber D3 progresses, the damping force due to the hydraulic lock function increases, preventing the contraction of the shock absorber D3.

[0075] Therefore, according to the shock absorber D3 of the third modified example configured in this manner, when the liquid level S in the reservoir R rises and reaches the movable partition 21, the return flow path P is blocked by the cushion (spring element) 20, the resistance element 5c applies resistance to the flow of hydraulic oil, and the hydraulic lock function can be exerted, and the characteristics of the shock absorber D3 when the hydraulic lock function is exerted can be easily tuned by setting the characteristics of the elastic force generated by the cushion (spring element) 20 against compression. Also, after the shock absorber D3 contracts and exerts the hydraulic lock function, when the direction of expansion and contraction of the shock absorber D3 changes and switches to the extension operation, the lower chamber L is depressurized and the movable partition 21 descends with the extension operation of the shock absorber D3 and separates from the cushion (spring element) 20, the return flow path P is opened, and the hydraulic oil that has flowed into the upper chamber U is returned to the lower chamber L quickly with almost no resistance.

[0076] The spring element does not have to be made of rubber as long as it can block the return flow path P when it abuts against the movable partition 21 and open the return flow path P when it separates from the movable partition 21, and may be, for example, a coil spring and an annular spring bearing that can abut the entire upper end surface of the movable partition 21 at the lower end of the coil spring. However, when the spring element is a rubber cushion 20 as in shock absorber D3 of this embodiment, the cushion 20 comes into close contact with the movable partition 21 when it abuts against the movable partition 21 and exhibits a sealing property that blocks the return flow path P without leakage, and is therefore excellent in that it can stably exhibit a hydraulic locking function.

[0077] The cushion 20 is elastic and fitted to the outer periphery of the cylinder 1 with a slight interference, and receives frictional resistance from the cylinder 1 when returning from the compressed state to the original state. On the other hand, the movable partition 21 also slides against the outer periphery of the cylinder 1, and receives frictional resistance between the movable partition 21 and the cylinder 1 when the movable partition 21 descends in the reservoir R. If the movable partition 21 is formed of a material with a smaller frictional resistance between the movable partition 21 and the cylinder 1 than the cushion 20, the movable partition 21 will be more likely to separate from the lower end of the cushion 20, the timing at which the return flow path P is opened will be earlier, and the hydraulic oil that has flowed into the upper chamber U will be more likely to return to the lower chamber L. Therefore, it is preferable that the movable partition 21 is formed of a material with a smaller frictional resistance between the movable partition 21 and the cylinder 1 than the cushion 20, which is made of rubber, and for example, it is preferable that the movable partition 21 is formed of a material with a smaller frictional resistance between the movable partition 21 and the cylinder 1 than the cushion 20, which is made of rubber, and is preferably made of a synthetic resin or metal with self-lubricating properties.

[0078] Therefore, according to the third modified example of the shock absorber D3, the hydraulic oil (liquid) that moves to the upper chamber U during the extension operation of the shock absorber D3 can be quickly returned to the lower chamber L, so that the liquid level S of the hydraulic oil (liquid) in the lower chamber L does not drop even if the shock absorber D3 repeats extension and contraction operations, and the hydraulic locking function can be stably performed when the shock absorber D3 contracts near the stroke end.

[0079] Furthermore, since the inner diameter of the receiving portion 22b in the support tube 22 that supports the cushion 20 and that abuts against the cushion 20 increases toward the cushion 20, and the inner peripheral surface of the lower end of the cushion 20 is a tapered surface, when the cushion 20 is compressed by the rise of the movable partition 21, the upper end of the cushion 20 is prevented from expanding in the radial direction by the receiving portion 22b, and the urging force of the cushion 20 can be efficiently applied to the movable partition 21. Furthermore, in this embodiment, the volume is reduced by providing the chamfered portion 20a at the upper end opening of the cushion 20, so that the upper end of the cushion 20 can easily enter the space on the inner peripheral side of the receiving portion 22b, and the effect of preventing the expansion of the diameter of the cushion 20 during compression can be enhanced, but the chamfered portion 20a may be omitted.

[0080] Furthermore, since the cushion 20 has a tapered chamfered portion 20b on the inner circumference of the lower opening end, when the cushion 20 abuts against the upper end of the movable partition 21, the lower end can abut while avoiding the return flow path P of the movable partition 21, thereby preventing the lower end from being pushed into the return flow path P between the protrusions 21d, 21d and being deteriorated.

[0081] In addition, the movable partition 21 described above has a groove 21c on the outer periphery that functions as the resistance element 5c, but instead of the groove 21c, a groove that runs from the inner periphery to the outer periphery and opens between the protrusions 21d, 21d may be provided at the upper end of the movable partition 21, and the groove may be used as the resistance element. In this case, when the shock absorber D3 contracts and the movable partition 21 abuts against the lower end of the cushion 20, the return flow path P and the groove are in series to communicate the upper chamber U and the lower chamber L, so that when the hydraulic oil passes through the groove, resistance is applied to the flow of the hydraulic oil, and a hydraulic lock function can be exhibited. When the shock absorber D3 expands and the movable partition 21 and the cushion 20 are separated, the return flow path P can quickly return the hydraulic oil from the upper chamber U to the lower chamber L. Furthermore, instead of being formed by a groove provided in the movable partition 21, the resistance element may be formed by a hole provided in the movable partition 21 and communicating the upper chamber U and the lower chamber L. Furthermore, the return flow path P only needs to be closed when the upper end of the movable partition 21 abuts against the lower end of the cushion 20 and opened when the movable partition 21 moves away from the cushion 20, so to that extent it may be installed by forming a groove or hole in the movable partition 21.

[0082] Although the preferred embodiment of the present invention has been described in detail above, modifications, variations and changes can be made without departing from the scope of the appended claims. [Explanation of symbols]

[0083] Reference Signs List 1 cylinder, 2 piston rod, 3 piston, 4, 15, 16, 21 movable partition, 5, 5a, 5b, 5c resistance element, 6 spring element, 7 outer cylinder, 15a throttle passage, 16a inlet passage, 16b return passage, 17 valve, 18 check valve, 20 cushion, D, D1, D2, D3 shock absorber, P return flow passage, R reservoir, R1 expansion side chamber, R2 compression side chamber

Claims

1. A cylinder; A piston rod is inserted into the cylinder so as to be movable in the axial direction; a piston connected to the piston rod and movably inserted into the cylinder to divide the inside of the cylinder into an extension-side chamber and a compression-side chamber filled with liquid; a reservoir that stores liquid and gas and is connected to the pressure-side chamber to compensate for the volume of the piston rod moving in and out of the cylinder; a movable partition that is accommodated in the reservoir and can move in the vertical direction with a lower limit of movement being a position above the liquid level when the piston is in a neutral position with respect to the cylinder, and that divides the reservoir into an upper chamber and a lower chamber; a resistance element providing resistance to the flow of liquid from the lower chamber to the upper chamber; a spring element that urges the movable partition downward when the movable partition rises while in contact with the movable partition; A shock absorber characterized by:

2. The movable partition is in sliding contact with one of the cylinder and the outer cylinder and is movable in the up and down direction, The resistance element is formed by a gap between the other of the cylinder and the outer tube and the movable partition.

2. The shock absorber according to claim 1 .

3. The resistance element is an inlet passage and a return passage provided in the movable partition and communicating between the upper chamber and the lower chamber; a valve that allows liquid to flow only through the inlet passage from the lower chamber to the upper chamber and provides resistance to the flow of liquid; a check valve that allows liquid to flow through the return passage only from the upper chamber to the lower chamber.

2. The shock absorber according to claim 1 .

4. The resistance element is The movable partition is provided with a throttle passage that communicates the upper chamber with the lower chamber and that narrows toward the upper chamber.

2. The shock absorber according to claim 1 .

5. The movable partition has a return flow path that communicates between the upper chamber and the lower chamber, is blocked when it abuts against the spring element, and is opened when it separates from the spring element, and faces the spring element with a gap in the vertical direction when it is located at the lower limit of movement.

2. The shock absorber according to claim 1 .

6. The spring element is a rubber cushion.

6. The shock absorber according to claim 5.

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