Shock absorber
Patent Information
- Application Number
- PCT/JP2026/005821
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-25
- Filing Date
- 2026-02-18
- Publication Date
- 2026-10-01
Smart Images
Figure JP2026005821_01102026_PF_FP_ABST
Abstract
Description
Shock absorber
[0001] The present invention relates to a shock absorber.
[0002] As disclosed in, for example, JP2015-117812A, a shock absorber includes a cylinder, a piston rod movably inserted into the cylinder, a piston connected to the piston rod and movably inserted into the cylinder that divides the interior of the cylinder into an extension-side chamber and a compression-side chamber both filled with hydraulic oil, a reservoir filled with hydraulic oil and gas, a valve case attached to an end of the cylinder that separates the compression-side chamber from the reservoir, an extension-side leaf valve provided on the piston that opens and closes an extension-side port to apply resistance to the flow of hydraulic oil flowing from the extension-side chamber toward the compression-side chamber, and a compression-side leaf valve provided on the valve case that opens and closes a discharge port to apply resistance to the flow of hydraulic oil flowing from the compression-side chamber toward the reservoir.
[0003] A conventional shock absorber configured as described above is used, for example, installed between a vehicle body and wheels of a vehicle. During extension operation where the piston moves relative to the cylinder in a direction that reduces the volume of the extension-side chamber, the extension-side leaf valve applies resistance to the flow of hydraulic oil from the extension-side chamber toward the compression-side chamber, generating an extension-side damping force that impedes the extension operation. During compression operation where the piston moves relative to the cylinder in a direction that reduces the volume of the compression-side chamber, the compression-side leaf valve applies resistance to the flow of hydraulic oil from the compression-side chamber toward the reservoir, generating a compression-side damping force that impedes the compression operation, thereby damping vibration of the vehicle body.
[0004] Furthermore, in a conventional shock absorber, when the piston is displaced to the vicinity of the compression-side stroke end during compression operation, a bump cushion rubber formed of urethane rubber or the like mounted on the outer circumference of the piston rod abuts against a bump stopper attached to the rod-side end of the cylinder and is compressed, generating a progressive force that suppresses further displacement of the shock absorber toward the compression side. Therefore, in a conventional shock absorber, when the compression operation proceeds to the vicinity of the compression-side stroke end, the progressive force generated by the bump cushion rubber is added to the compression-side damping force generated by the compression-side leaf valve to impede the compression operation, thereby mitigating the impact at full compression.
[0005] JP2015-117812A
[0006] In conventional shock absorbers, as mentioned above, when the shock absorber is in a state where it is about to fully compress, the step-release force of the bump cushion rubber is added to the compression damping force to prevent the compression operation. However, even when the shock absorber compresses to near the end of the compression stroke, the compression damping force itself does not increase.
[0007] Therefore, with conventional shock absorbers, if a vehicle to which the shock absorber is applied travels on rough roads and the vehicle body vibrates at high speed, causing it to contract near the end of the compression stroke, even if the bump cushion rubber exerts a step-up force, the force to suppress the contraction operation may be insufficient, and the contraction operation may not be adequately suppressed. Thus, a greater damping force on the compression side than before is required.
[0008] To meet these demands, the pressure in the compression chamber should be increased when the shock absorber is contracting. However, this would increase the damping force generated when the vehicle is traveling on a smooth road surface with few irregularities, resulting in a small stroke on the contraction side of the shock absorber and the piston being displaced near the neutral position relative to the cylinder. This would compromise the ride comfort of the vehicle.
[0009] Therefore, the present invention aims to provide a shock absorber that can generate high damping force near the compression stroke end without compromising ride comfort in a vehicle.
[0010] To solve the aforementioned problems, the buffer of the present invention comprises a cylinder, a piston rod inserted into the cylinder so as to be movable in the axial direction, a movable body which is allowed to move in the axial direction relative to the cylinder and includes a piston connected to the piston rod and inserted into the cylinder so as to be movable in the axial direction, and which divides the inside of the cylinder into an extension chamber and a compression chamber, a reservoir for storing liquid, a compression damping valve which provides resistance to the flow of liquid from the compression chamber to the reservoir, a partition wall body which is housed in the compression chamber so as to be movable in the axial direction of the cylinder and has a communication hole which is closed by the movable body when it comes into contact with the movable body, and together with the movable body it forms a pressure chamber in the compression chamber that leads to the compression damping valve, and a supply passage which enables the supply of liquid from the reservoir to the extension chamber when the movable body is positioned on the compression stroke end side of the position where it comes into contact with the partition wall, wherein the pressure-receiving area which receives pressure in the pressure chamber in a direction that prevents the movable body and the partition wall from moving toward the compression stroke end side when the movable body and the partition wall are in contact is larger than the cross-sectional area of the piston rod.
[0011] With a shock absorber configured in this way, when the moving body comes into contact with the bulkhead during the compression operation, the damping force generated by the shock absorber increases, creating a greater force that hinders the shock absorber's compression operation, thereby sufficiently suppressing the compression operation. Furthermore, the damping force during compression operation does not become excessive until near the end of the compression stroke, so that the ride comfort in the vehicle is not compromised.
[0012] Figure 1 is a cross-sectional view of a buffer in one embodiment. Figure 2 is a partially enlarged cross-sectional view of a buffer in one embodiment. Figure 3 is a partially enlarged cross-sectional view of a buffer in one embodiment with the moving body in contact with the partition wall. Figure 4 is a partially enlarged cross-sectional view of a buffer in one embodiment with the moving body in contact with the partition wall and the contraction operation progressing.
[0013] The present invention will be described based on the embodiments shown in the figures. As shown in Figure 1, the buffer D in one embodiment includes a cylinder 1, a piston rod 2 inserted into the cylinder 1 so as to be movable in the axial direction, a movable body M having a piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be movable in the axial direction, and dividing the inside of the cylinder 1 into an extension chamber R1 and a compression chamber R2, a reservoir R for storing liquid, a compression damping valve 12 that provides resistance to the flow of liquid from the compression chamber R2 to the reservoir R, a partition wall 20 housed in the compression chamber R2 so as to be movable in the axial direction of the cylinder 1, and when it comes into contact with the movable body M, together with the movable body M, it forms a pressure chamber PR in the compression chamber R2 that leads to the compression damping valve 12, and a supply passage SP that enables the supply of liquid from the reservoir R to the extension chamber R1 when the movable body M is positioned on the compression stroke end side of the position where it comes into contact with the partition wall 20.
[0014] Although not shown in the diagram, shock absorber D is installed between the vehicle body and the rear wheels in a saddle-type vehicle, for example, to generate damping force during expansion and contraction and suppress vibrations of the vehicle body. Note that shock absorber D may also be used in vehicles other than saddle-type vehicles, such as automobiles, or in equipment other than vehicles, buildings, etc.
[0015] The following describes the various parts of the shock absorber D. The cylinder 1 is cylindrical and has a piston 3 inserted inside so as to be movable in the axial direction. The inside of the cylinder 1 is divided by the piston 3 into an extension chamber R1 above the piston 3 in Figure 1 and a compression chamber R2 below the piston 3 in Figure 1. The cylinder 1 also has a through hole 1a near the lower end in Figure 1 that connects the inside and outside of the cylinder 1, and a stopper 21 is provided below and above the through hole 1a.
[0016] The stopper 21 comprises an annular base 21a and an annular stopper portion 21b rising from the inner circumference of the base 21a. The cylinder 1 is formed by connecting an upper portion 1b and a lower portion 1c having a through hole 1a via the stopper 21. Specifically, the lower end of the upper portion 1b in Figure 1 is fitted to the inner circumference of the base 21a of the stopper 21 above the stopper portion 21b, and the upper portion 1b and the base 21a are joined by welding or press-fitting, and the upper end of the lower portion 1c in Figure 1 is fitted to the inner circumference of the base 21a of the stopper 21 below the stopper portion 21b, and the lower portion 1c and the base 21a are joined by welding or press-fitting, thereby integrating the upper portion 1b and the lower portion 1c together with the stopper 21 to form the cylinder 1.
[0017] Furthermore, a bottomed cylindrical outer cylinder 4 is provided on the outer circumference of the cylinder 1, covering the cylinder 1. An annular gap is provided between the outer cylinder 4 and the cylinder 1, and the reservoir R described above is formed by this annular gap. Thus, the buffer D of this embodiment is configured as a double-cylinder type buffer. In addition, the extension chamber R1 and the compression chamber R2 inside the cylinder 1 are filled with a liquid such as hydraulic oil, and the reservoir R is filled with the same liquid as the liquid filled inside the cylinder 1, as well as a gas. Note that in addition to hydraulic oil, water, aqueous solution, etc. may be used as the liquid. When the liquid is hydraulic oil, the gas filled inside the reservoir R should preferably be an inert gas such as nitrogen to prevent deterioration of the hydraulic oil. The through hole 1a provided in the cylinder 1 opens at a position that is always below the liquid surface facing the gas in the reservoir R, and connects the reservoir R and the compression chamber R2.
[0018] Next, a valve case 10 is fitted to the lower end of the cylinder 1 in Figure 1, which is placed on the bottom 4a of the outer cylinder 4 and separates the pressure chamber R2 inside the cylinder 1 from the reservoir R between the cylinder 1 and the outer cylinder 4. Furthermore, a rod guide 15 is fitted to the upper end of the cylinder 1 in Figure 1, which slidably supports the piston rod 2. The outer circumference of the rod guide 15, on the lower side in Figure 1, has a smaller diameter and is fitted to the inner circumference of the upper end of the cylinder 1, while the outer circumference of the rod guide 15, on the upper side in Figure 1, is fitted to the inner circumference of the outer cylinder 4. The rod guide 15 is housed in the inner circumference of the upper end of the outer cylinder 4 together with an annular sealing member 16 and a bump stopper 17 formed by an annular plate, which are stacked above the rod guide 15 in Figure 1. The rod guide 15 is fixed inside the outer cylinder 4 together with the sealing member 16 and the bump stopper 17 by crimping the upper end of the outer cylinder 4 in Figure 1. The sealing member 16 seals the space between the outer cylinder 4, the cylinder 1, and the piston rod 2, preventing liquid leakage from inside the buffer D. When the rod guide 15 is fixed to the outer cylinder 4 in this way, the cylinder 1 is held together with the bump stopper 17, the sealing member 16, the rod guide 15, and the valve case 10 by being sandwiched between the crimped upper end and the bottom 4a of the outer cylinder 4, and is fixed inside the outer cylinder 4.
[0019] Alternatively, instead of crimping the upper opening of the outer cylinder 4, a cylindrical cap with a top that also functions as a bump stopper may be screwed onto the upper opening of the outer cylinder 4, and the sealing member 16, rod guide 15, cylinder 1, and valve case 10 may be sandwiched between this cap and the bottom portion 4a of the outer cylinder 4, thereby fixing these members inside the outer cylinder 4. Furthermore, if the upper end of the outer cylinder 4 is crimped, or if the cylindrical cap with a top is screwed onto the outer cylinder 4, the stopper 21 may not be welded or press-fitted when forming the cylinder 1, but rather the cylinder 1 and the stopper 21 may be held integrally by the axial force generated by the crimping of the outer cylinder 4 or the screwing of the cap onto the outer cylinder 4, which sandwiches the stopper portion 21b between the upper portion 1b and the lower portion 1c of the cylinder 1.
[0020] 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 provided on the upper side of the piston fitting portion 2a in Figure 1, a stepped portion 2c provided at the boundary between the piston fitting portion 2a and the larger diameter portion 2b, and a threaded portion 2d provided on the outer circumference of the tip of the piston fitting portion 2a.
[0021] A bracket 18 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 the vehicle body via this bracket (not shown). A bracket 19 is also provided at the bottom 4a of the outer cylinder 4, and the outer cylinder 4 is connected to the wheel via brackets 18 and 19.
[0022] In this embodiment, the shock absorber D has a piston rod 2 connected to the vehicle body, and a cylinder 1 interposed between the vehicle body and the wheel. When the vehicle travels on an uneven road surface, causing the wheel 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.
[0023] In Figure 1, the outer circumference of the upper end of the piston rod 2 is fitted with a rod-side spring receiver 30 and a cylindrical bump cushion rubber 31 held by the rod-side spring receiver 30, while the outer circumference of the outer cylinder 4 is fitted with an outer cylinder-side spring receiver 32. Between the rod-side spring receiver 30 and the outer cylinder-side spring receiver 32, a suspension spring 33 made of a coil spring is provided. Therefore, when the shock absorber D is installed between the vehicle body and the wheels, the suspension spring 33 compresses and generates an elastic force, and the vehicle body is elastically supported by the suspension spring 33. Furthermore, when the shock absorber D exhibits a contraction operation in which the piston rod 2 enters the cylinder 1 and contracts to near the compression stroke end, the bump cushion rubber 31 abuts against the bump stopper 17 and is compressed, generating an elastic force that hinders the contraction of the shock absorber D.
[0024] Next, the piston 3 is annular in shape and fitted onto the outer circumference of the piston fitting portion 2a of the piston rod 2, and is fixed to the piston rod 2 by a piston nut 9 that is screwed onto the threaded portion 2d of the piston rod 2. More specifically, as shown in Figure 1, the piston 3 is composed of an annular piston body 3a, a cylindrical portion 3b provided on the outer circumference of the lower end of the piston body 3a in Figure 2, an extension port 3c that passes through the piston body 3a in the axial direction, and a compression port 3d that passes through the piston body 3a in the axial direction and functions as a piston passage.
[0025] As described above, the piston 3 is a bottomed cylindrical shape comprising a piston body 3a and a cylindrical portion 3b, and a piston ring 3e is mounted on its outer circumference, sliding against the inner circumference of the cylinder 1, allowing it to move axially relative to the cylinder 1. The extension port 3c and compression port 3d pass through the piston body 3a axially, connecting the extension chamber R1 and the compression chamber R2. The stroke range of the piston 3 relative to the cylinder 1 is limited to the inner circumference of the upper portion 1b of the cylinder 1 above the stopper 21, so the stopper 21 does not interfere with the axial movement of the piston 3.
[0026] Next, in the lower part of the piston body 3a of the piston 3 in Figure 1, an extension damping valve 5 is stacked to open and close the outlet end of the extension port 3c. The extension damping valve 5 is composed of a stacked leaf valve 5a made by stacking multiple annular plates, a spring receiver 5b stacked on the back side of the stacked leaf valve 5a opposite the piston, and a coil spring 5c that biases the stacked leaf valve 5a in the direction of seating it on the piston 3 via the spring receiver 5b.
[0027] The laminated leaf valve 5a is mounted on the outer circumference of the piston fitting portion 2a together with the piston 3, and then fixed to the piston rod 2 by a cylindrical piston nut 9 that is screw-connected to the threaded portion 2d. The extension damping valve 5 is fixed to the piston rod 2 on its inner circumference by the piston nut 9, and deflection of the outer circumference is permitted.
[0028] The piston nut 9 is cylindrical and has a screw groove on its inner circumference, and comprises a cylindrical portion 9a that abuts against the inner circumference of the extension damping valve 5, and a flange 9b provided on the outer circumference of the lower end of the cylindrical portion 9a in Figure 1, which faces the partition wall 20 in the axial direction and can abut against the partition wall 20. The outer diameter of the outer circumference of the cylindrical portion 9a at the upper end in Figure 1 is smaller than the outer diameter of the lower side.
[0029] A spring retainer 5b is slidably mounted on the outer circumference of the smaller diameter portion of the piston nut 9. The spring retainer 5b is cylindrical and comprises a guide portion 5b1 that slides against the outer circumference of the piston nut 9, and a flange-shaped spring retainer portion 5b2 that extends outward from the upper end of the guide portion 5b1. It abuts against the back side of the laminated leaf valve 5a, and when the laminated leaf valve 5a flexes, it moves axially along the outer circumference of the piston nut 9 in accordance with the amount of flexure of the laminated leaf valve 5a.
[0030] The coil spring 5c is supported at one end by the spring receiving portion 5b2 of the spring receiving 5b and at the other end by the flange 9b of the piston nut 9, and is assembled in a compressed state on the outer circumference side of the piston nut 9 between the spring receiving 5b and the piston nut 9, constantly biasing the laminated leaf valve 5a toward the piston 3.
[0031] The extension damping valve 5 closes the extension port 3c when the outer circumference of the laminated leaf valve 5a is in contact with the piston body 3a, and when the outer circumference of the laminated leaf valve 5a flexes and separates from the piston body 3a, it opens the extension port 3c while resisting the flow of liquid passing through the extension port 3c from the extension chamber R1 to the compression chamber R2. The outer diameter of the laminated leaf valve 5a in the extension damping valve 5 is set such that even when the extension damping valve 5 is laminated on the lower end of the piston body 3a of the piston 3, the compression port 3d, which is located on the outer circumference of the extension port 3c, is not blocked.
[0032] Furthermore, in the extension damping valve 5, the opening pressure at which the outer circumference of the laminated leaf valve 5a flexes and separates from the piston 3, opening the extension port 3c, is set by the biasing force of the coil spring 5c, and the resistance to the flow of liquid passing through the extension port 3c can be adjusted by adjusting the biasing force of the coil spring 5c.
[0033] Furthermore, the extension damping valve 5 may not be configured as described above; it may be a valve equipped only with a laminated leaf valve 5a, or it may be composed of a throttle valve such as an orifice or choke. In addition, the number of stacked annular plates in the laminated leaf valve 5a can be arbitrarily designed and changed according to the desired damping force characteristics.
[0034] On the other hand, a compression-side check valve 6, which opens and closes the outlet end of the compression-side port 3d, is stacked on the upper part of the piston body 3a of the piston 3 in Figure 1. The compression-side check valve 6 is composed of an annular valve body 6a that opens and closes the compression-side port 3d, a spring retainer 6b that is fitted onto the outer circumference of the piston fitting portion 2a of the piston rod 2, and a conical coil spring 6c that is positioned between the valve body 6a and the spring retainer 6b.
[0035] The valve body 6a is annular in shape and is stacked on the extension chamber R1 side of the piston body 3a of the piston 3, allowing the entire valve body to move in and out of reach of the piston body 3a. When seated on the piston body 3a, it closes the compression port 3d, which serves as the piston passage, and when separated from the piston body 3a, it opens the compression port 3d. The valve body 6a also has several notches on its inner circumference (not shown), which allow the extension port 3c to always communicate with the extension chamber R1 through these notches even when seated on the piston body 3a.
[0036] The spring retainer 6b comprises a cylindrical portion 6b1 that fits onto the outer circumference of the piston fitting portion 2a of the piston rod 2 and abuts against the inner circumference of the piston body 3a, and a flange-shaped spring retainer portion 6b2 that extends from the upper end of the cylindrical portion 6b1 toward the outer circumference in Figure 1. It is sandwiched between the piston 3 and the stepped portion 2c of the piston rod 2 and fixed to the outer circumference of the piston rod 2. The valve body 6a slides against the outer circumference of the cylindrical portion 6b1 and can move axially relative to the piston 3 using the cylindrical portion 6b1 as a guide.
[0037] The conical coil spring 6c is also positioned in a compressed state between the valve body 6a and the spring receiving portion 6b2 of the spring receiving 6b, constantly biasing the valve body 6a toward the piston body 3a. Furthermore, the biasing force of the conical coil spring 6c is weak, and it presses the valve body 6a toward the piston body 3a with a weak force.
[0038] The compression-side check valve 6 closes the compression-side port 3d when the valve body 6a is in contact with the piston body 3a, and when the valve body 6a compresses the conical coil spring 6c and moves away from the piston body 3a, it opens the compression-side port 3d, allowing the flow of liquid passing through the compression-side port 3d from the compression-side chamber R2 to the extension-side chamber R1 with almost no resistance.
[0039] Furthermore, in the case of the compression-side check valve 6, the opening pressure at which the valve body 6a separates from the piston 3 and opens the compression-side port 3d can be adjusted by setting the biasing force of the conical coil spring 6c. In addition, the compression-side check valve 6 may be constructed not by the above-described configuration, but by stacking one annular plate or multiple annular plates, and the design can be changed as appropriate.
[0040] Thus, the piston rod 2, the piston 3 assembled to the piston rod 2, the extension damping valve 5, the compression check valve 6, and the piston nut 9, together with the piston rod 2, form a movable body M that is allowed to move axially relative to the cylinder 1.
[0041] As shown in Figure 2, the valve case 10 has an annular fitting portion 10a fitted to the inner circumference of the lower end of the cylinder 1, with a flange 10b on its outer circumference that abuts against the lower end of the cylinder 1 in Figure 2; a plurality of legs 10c provided at equal intervals in the circumferential direction at the lower end of the fitting portion 10a in Figure 2, extending downward and seating on the bottom 4a of the outer cylinder 4; and a discharge port 10d and a suction port 10e that pass through the fitting portion 10a and connect the pressure side chamber R2 and the reservoir R. Even when the valve case 10 is placed on the bottom 4a of the outer cylinder 4, the discharge port 10d and the suction port 10e are connected to the reservoir R via the spaces between the legs 10c, 10c.
[0042] A compression-side damping valve 12 that opens and closes the outlet end of a discharge port 10d is stacked on the lower side of the fitting portion 10a in FIG. 2. The compression-side damping valve 12 is a laminated leaf valve configured by laminating a plurality of annular plates, and is mounted on the outer circumference of a center rod 11 inserted into the inner circumference of the fitting portion 10a together with a valve case 10. The center rod is shaft-shaped, has a flange 11a at the base end, and has a screw portion 11b at the distal end to which a nut 14 is screw-coupled. The valve case 10 and the compression-side damping valve 12 are clamped by the flange 11a and the nut 14 and fixed to the center rod 11. The inner circumferential side of the compression-side damping valve 12 is fixed to the center rod 11, allowing deflection of the outer circumferential side. The compression-side damping valve 12 closes the discharge port 10d in a state where the outer circumferential side is in contact with the fitting portion 10a; when the outer circumferential side is deflected and separated from the fitting portion 10a, the discharge port 10d is opened, and resistance is applied to the flow of liquid passing through the discharge port 10d from the compression-side chamber R2 toward the reservoir R. The outer diameter of the compression-side damping valve 12 is set to a diameter that does not block the inlet end of the suction port 10e arranged on the outer circumferential side of the discharge port 10d even when the compression-side damping valve 12 is stacked on the lower end of the fitting portion 10a.
[0043] On the other hand, an extension-side check valve 13 that opens and closes the outlet end of the suction port 10e is stacked on the upper side of the fitting portion 10a in FIG. 2. The extension-side check valve 13 includes a valve body 13a that is entirely stackably disposed on the upper end of the fitting portion 10a in FIG. 2 to open and close the suction port 10e, and a conical coil spring 13b that biases the valve body 13a toward the fitting portion 10a side.
[0044] After the extension-side check valve 13 is mounted on the outer circumference of the center rod 11 together with the valve case 10, it is fixed to the center rod 11 by the nut 14 and the flange 11a. The valve body 13a of the extension-side check valve 13 is in sliding contact with the outer circumference of the center rod 11 and is movable axially relative to the valve case 10. The valve body 13a closes the suction port 10e in a state where it abuts against the fitting portion 10a, and opens the suction port 10e when the entire valve body is separated from the fitting portion 10a.
[0045] The conical coil spring 13b is assembled in a compressed state between the valve body 13a and the flange 11a of the center rod 11, and constantly biases the valve body 13a toward the fitting portion 10a. The biasing force of the conical coil spring 13b is weak, and the conical coil spring 13b presses the valve body 13a toward the fitting portion 10a of the valve case 10 with a weak force.
[0046] In the extension-side check valve 13 configured as described above, the valve body 13a is separated from the fitting portion 10a to open the valve against the flow of liquid passing through the suction port 10e from the reservoir R toward the compression side chamber R2, allowing the liquid to pass through with almost no resistance. On the contrary, when the liquid tries to pass through the suction port 10e from the compression side chamber R2 toward the reservoir R, the valve closes to block the passage of the liquid. Note that the valve body 13a of the extension-side check valve 13 is provided with an axially penetrating hole 13a1, and even when stacked on the upper end of the fitting portion 10a in FIG. 2, it does not block the inlet end of the discharge port 10d, and allows liquid to pass through the discharge port 10d.
[0047] As shown in FIG. 2, the partition body 20 is slidably in contact with the inner circumference of the lower portion 1c of the cylinder 1, which is located below the stopper 21 of the cylinder 1, and is accommodated in the compression side chamber R2. The partition body 20 is annular and includes: a cylindrical portion 20a facing the inner peripheral surface of the cylinder 1; an annular opposing portion 20b protruding inward from the upper end of the cylindrical portion 20a in FIG. 2 and axially opposing the flange 9b of the piston nut 9 in the moving body M; and a communication hole 20c formed on the inner circumference of the opposing portion 20b.
[0048] The cylindrical portion 20a has a larger outer diameter on the lower side in FIG. 2. The outer peripheral surface of the large-diameter portion 20a1 on the lower side is in sliding contact with the inner peripheral surface of the cylinder 1, and the outer peripheral surface of the small-diameter portion 20a2 on the upper side faces the inner peripheral surface of the cylinder 1 via an annular gap G.
[0049] Since the large-diameter portion 20a1 of the cylindrical portion 20a of the partition wall 20 is in sliding contact with the inner circumferential surface of the cylinder 1, the partition wall 20 can move vertically in the axial direction without axial wobble relative to the cylinder 1. When the upper end of the cylindrical portion 20a of the partition wall 20 comes into contact with the annular stopper portion 21b of the stopper 21, the partition wall 20 is restricted from moving any further upward towards the anti-pressure side stroke end in Figure 2.
[0050] Furthermore, a coil spring 22 is provided between the partition wall 20 and the outer circumference of the fitting portion 10a of the valve case 10, on the outer circumference side of the suction port 10e. The coil spring 22 biases the partition wall 20 toward the stopper 21, which is at the top in Figure 2, and positions the partition wall 20 in an initial position where it abuts against the stopper portion 21b of the stopper 21.
[0051] In this initial position, when the partition wall 20 is positioned such that the cylindrical portion 20a abuts against the stopper portion 21b of the stopper 21, the small diameter portion 20a2 of the cylindrical portion 20a faces the through hole 1a, but the communication between the through hole 1a and the pressure side chamber R2 is cut off by the cylindrical portion 20a and the stopper portion 21b. On the other hand, when the shock absorber D is contracted as the piston rod 2 enters the cylinder 1, as shown in Figure 3, the movable body M is displaced to the vicinity of the pressure side stroke end, and when the flange 9b of the piston nut 9 on the movable body M abuts against the opposing portion 20b of the partition wall 20, the communication hole 20c on the inside of the opposing portion 20b of the partition wall 20 is closed by the movable body M, and a pressure chamber PR leading to the pressure side damping valve 12 via the discharge port 10d is formed in the pressure side chamber R2 of the cylinder 1 by the movable body M and the partition wall 20. Furthermore, when the partition wall 20 is separated from the moving body M, it is positioned in its initial position by the coil spring 22, and communicates with chamber A, which is above the partition wall 20 in Figure 1, and chamber B, which is below the partition wall 20 in Figure 1 and communicates with the discharge port 10d and suction port 10e where the pressure-side damping valve 12 is provided, and becomes the pressure chamber PR when the partition wall 20 and the moving body M come into contact, via a communication hole 20c.
[0052] Furthermore, both the opposing surface of the flange 9b of the piston nut 9 that faces the partition body 20 and the opposing surface of the opposing portion 20b of the partition body 20 that faces the flange 9b are flat surfaces. When the flange 9b and the opposing portion 20b come into contact, the inner circumference of the partition body 20 can be tightly closed by the moving body M. The partition body 20 is annular in shape as a whole, so as to prevent interference with the tip of the piston rod 2, the opposing portion 20b is in contact with the flange 9b, allowing the tip of the piston rod 2 to be inserted into the communication hole 20c.
[0053] Then, when the movable body M and the partition wall 20 come into contact, and the movable body M is further displaced toward the vicinity of the compression stroke end as shown in Figure 4, both the movable body M and the partition wall 20 reduce the pressure chamber PR, and the cylindrical portion 20a of the partition wall 20 separates downward from the stopper portion 21b, so that the chamber A above the pressure chamber PR in the compression chamber R2 is connected to the reservoir R through the space between the partition wall 20 and the stopper portion 21b and through the through hole 1a.
[0054] When the movable body M is separated from the partition wall 20, the partition wall 20 is positioned by the coil spring 22 to abut against the stopper portion 21b, and the pressure in the pressure chamber R2 pushes the partition wall 20 toward the stopper portion 21b, thereby cutting off communication between the through-hole 1a and the pressure chamber R2. In this way, the partition wall 20 can open and close the through-hole 1a, and when it is pushed down by the movable body M in Figure 2 and separated from the stopper portion 21b, it opens the through-hole 1a. Therefore, the partition wall 20, the stopper 21, and the coil spring 22 constitute a mechanical check valve Mc that opens and closes the through-hole 1a.
[0055] The shock absorber D is configured as described above, and the operation of the shock absorber D will be explained below. First, when the shock absorber D extends within a range in which the movable body M does not come into contact with the bulkhead body 20, the movable body M, including the piston rod 2 and the piston 3, moves upward in Figure 1 relative to the cylinder 1, causing the extension chamber R1 to contract and the compression chamber R2 to expand. The liquid in the contracted extension chamber R1 pushes open the extension damping valve 5, passes through the extension port 3c, and moves into the expanded compression chamber R2. The extension damping valve 5 resists the flow of liquid passing through the extension port 3c, causing the pressure in the extension chamber R1 to rise and act on the piston 3, and the shock absorber D generates a damping force that hinders the extension operation. Furthermore, the movable body M and the partition body 20 are separated, and the upper chamber A and the lower chamber B of the partition body 20 within the pressure-side chamber R2 are in communication via the communication hole 20c. As a result, no pressure chamber PR is formed within the pressure-side chamber R2, and the entire pressure-side chamber R2 is in communication with the suction port 10e. Therefore, when the buffer D extends, the piston rod 2 retracts from the cylinder 1, and the amount of liquid in the cylinder 1 decreases by the volume of the piston rod 2 that has retracted. However, the liquid shortage is compensated for by the extension-side check valve 13 opening and supplying liquid from the reservoir R into the cylinder 1 through the suction port 10e, thereby compensating for the volume of the piston rod 2 that retracts from the cylinder 1.
[0056] On the other hand, when the shock absorber D contracts within a range where the moving body M does not come into contact with the bulkhead 20, the piston rod 2 and piston 3 move downward relative to the cylinder 1 in Figure 1, causing the pressure chamber R2 to shrink and the extension chamber R1 to expand. As a result, the liquid in the shrinking pressure chamber R2 moves through the pressure check valve 6, passing through the pressure port 3d to the expanding extension chamber R1.
[0057] Furthermore, since the movable body M and the partition body 20 are separated, the upper chamber A and the lower chamber B of the partition body 20 within the pressure side chamber R2 are connected via the communication hole 20c, so that no pressure chamber PR is formed within the pressure side chamber R2, and the entire pressure side chamber R2 is connected to the discharge port 10d.
[0058] When the shock absorber D contracts, the piston rod 2 enters the cylinder 1, resulting in an excess of liquid in the cylinder 1 equivalent to the volume of liquid the piston rod 2 enters. This excess liquid, corresponding to the volume of liquid the piston rod 2 enters the cylinder 1, pushes open the pressure damping valve 12, passes through the discharge port 10d, and moves from the cylinder 1 to the reservoir R.
[0059] The pressure-side damping valve 12 resists the flow of liquid passing through the discharge port 10d, causing the pressure inside the cylinder 1 to rise and act on the piston 3, generating a damping force that prevents the shock absorber D from contracting. Until the movable body M contacts the partition wall 20, the partition wall 20 is biased toward the stopper portion 21b by the pressure inside the pressure-side chamber R2 and the biasing force of the coil spring 22. As a result, the partition wall 20 does not separate from the stopper portion 21b, the mechanical check valve Mc is kept closed, and the liquid inside the cylinder 1 does not leak to the reservoir R through the through hole 1a when the shock absorber D contracts.
[0060] Then, when the shock absorber D is contracting, if the movable body M is displaced to the vicinity of the compression stroke end, which is the limit of movement on the contraction side, the lower end of the flange 9b of the piston nut 9 on the movable body M in Figure 3 comes into contact with the upper end of the cylindrical portion 20a of the partition wall 20 in Figure 3. When the movable body M and the partition wall 20 come into contact, the communication hole 20c is closed by the movable body M, so the communication between the upper chamber A and the lower chamber B of the compression chamber R2 is severed, and a pressure chamber PR is formed within the compression chamber R2 by the movable body M and the chamber B that is closed by the partition wall 20. As described above, the pressure chamber PR is isolated from the upper chamber A of the compression chamber R2 when the movable body M comes into contact with the partition wall 20.
[0061] From this state, when the movable body M moves further toward the compression stroke end side to the state shown in Figure 4, the partition wall 20 moves downward toward the inner circumference of the lower part 1c of the cylinder 1, reducing the volume of the pressure chamber PR by the movable body M and the partition wall 20, and the partition wall 20 moves away from the stopper part 21b, causing the mechanical check valve Mc to open, and the chamber A above the pressure chamber PR in the compression side chamber R2 and the reservoir R to communicate through the through hole 1a.
[0062] As the movable body M and the partition body 20 move in a direction that reduces the pressure chamber PR, the volume of the pressure chamber PR is reduced by a volume equal to the value obtained by multiplying the distance the movable body M and the partition body 20 have moved within the cylinder 1 since they first came into contact with each other by the area of a circle whose diameter is the inner diameter of the cylinder 1. As a result, the liquid equivalent to the volume reduction in the pressure chamber PR moves to the reservoir R via the discharge port 10d and the pressure-side damping valve 12.
[0063] The pressure in the pressure chamber PR acts on the movable body M and the partition wall 20 in a direction that opposes the downward movement of the movable body M and the partition wall 20 in Figure 4. Thus, the pressure-receiving area of the movable body M and the partition wall 20 that are subjected to the pressure of the pressure chamber PR is equal to the area of a circle with the outer diameter of the partition wall 20 as its diameter.
[0064] In contrast, when the shock absorber D contracts within a range where the moving body M does not come into contact with the bulkhead 20, the compression check valve 6 opens, connecting the compression chamber R2 and the extension chamber R1. As a result, the pressure in the compression chamber R2 and the pressure in the extension chamber R1 become approximately equal. This generates a force in which the pressure inside the cylinder 1 acts on the area of the moving body M facing the compression chamber R2, pushing the moving body M upward in Figure 1, and a force in which the pressure inside the cylinder 1 acts on the area of the piston 3 facing the extension chamber R1, pushing the moving body M downward in Figure 1. The area of the moving body M facing the compression chamber R2 is equal to the area of the large-diameter portion 2b of the piston rod 2 when the area of a circle with the outer diameter of the piston 3 as its diameter is subtracted from the area of the piston 3 facing the extension chamber R1. Therefore, when the shock absorber D contracts in a manner that prevents the moving body M from contacting the bulkhead 20, the effective pressure-receiving area of the moving body M, where the pressure inside the cylinder 1 acts in a direction that prevents the moving body M from moving downward within the cylinder 1, is the area of the large-diameter portion 2b of the piston rod 2.
[0065] As mentioned above, when the movable body M and the partition body 20 come into contact and compress the pressure chamber PR as a single unit, the effective pressure-receiving area of the movable body M and the partition body 20 that receive the pressure of the pressure chamber PR is the area of a circle with the outer diameter of the partition body 20 as its diameter. Therefore, it is larger than the cross-sectional area of the large-diameter portion 2b of the piston rod 2, which is the effective pressure-receiving area of the movable body M that receives the pressure of the cylinder 1 when the movable body M is not in contact with the partition body 20.
[0066] Therefore, during the contraction operation of the shock absorber D, when the moving body M changes from a state where it does not contact the bulkhead 20 to a state where it contacts the bulkhead 20, the effective pressure-receiving area that receives pressure acting to hinder the contraction operation of the shock absorber D increases. Consequently, when the moving body M changes from a state where it does not contact the bulkhead 20 to a state where it contacts the bulkhead 20 during the contraction operation of the shock absorber D, the damping force generated by the shock absorber D increases, and the force hindering the contraction operation of the shock absorber D increases.
[0067] Furthermore, when the movable body M is not in contact with the partition wall 20, liquid moves from the pressure chamber R2 to the extension chamber R1, so only liquid equivalent to the volume of liquid that the piston rod 2 enters the cylinder 1 passes through the pressure damping valve 12 and moves to the reservoir R. However, when the movable body M comes into contact with the partition wall 20, all of the liquid equivalent to the volume reduction in the pressure chamber PR passes through the pressure damping valve 12. Therefore, compared to the flow rate that passes through the pressure damping valve 12 when the buffer D contracts while the movable body M is not in contact with the partition wall 20, the flow rate that passes through the pressure damping valve 12 when the movable body M and the partition wall 20 are in contact and the buffer D contracts is greater. Specifically, if we let X be the value obtained by dividing the cross-sectional area of the piston 3 by the cross-sectional area of the large-diameter portion 2b of the piston rod 2, then the flow rate passing through the pressure-side damping valve 12 when the movable body M and the partition wall 20 are in contact will be X times the flow rate passing through the pressure-side damping valve 12 when the movable body M is not in contact with the partition wall 20. Therefore, if the contraction speed of the buffer D is the same, the pressure in the pressure chamber PR when the movable body M and the partition wall 20 are in contact will be higher than the pressure inside the cylinder 1 when the movable body M is not in contact with the partition wall 20.
[0068] Therefore, in the shock absorber D of this embodiment, when the movable body M is displaced to near the end of the compression stroke during the contraction stroke, it comes into contact with the partition wall 20 and forms a pressure chamber PR. Furthermore, as the contraction operation continues, the effective pressure receiving area increases, and the pressure in the pressure chamber PR can be increased as the flow rate through the compression damping valve 12 increases, allowing the shock absorber D to significantly increase its damping force and suppress the contraction operation. Furthermore, as the contraction of the shock absorber D progresses, the bump cushion rubber 31 abuts against the bump stopper 17, generating an elastic force. This elastic force is added to the damping force generated by the shock absorber D, further increasing the force that hinders the contraction of the shock absorber D and reducing the contraction speed. It should be noted that the bump cushion rubber 31 may be set to abut against the bump stopper 17 before the movable body M abuts against the partition wall 20 during the contraction operation of the shock absorber D.
[0069] As the movable body M remains in contact with the bulkhead 20 and the buffer D continues to contract, the bulkhead 20 moves away from the stopper 21, causing the mechanical check valve Mc to open and connecting the reservoir R with the upper chamber A, which is isolated from the pressure chamber PR in the pressure-side chamber R2, through the through-hole 1a. As the movable body M remains in contact with the bulkhead 20 and the buffer D continues to contract, a liquid equal to the area of a circle with the outer diameter of the bulkhead 20 multiplied by the distance the bulkhead 20 moves downward is discharged from the pressure chamber PR to the reservoir R through the pressure-side damping valve 12. However, since the volume of the piston rod 2 entering the cylinder 1 is less than the amount of liquid discharged from the pressure chamber PR, the insufficient liquid is supplied to the extension-side chamber R1 through the through-hole 1a and the pressure-side port 3d. As described above, in the buffer D of this embodiment, the supply passage SP is composed of a through hole 1a and a pressure-side port 3d. The through hole 1a is provided in the cylinder 1 and functions as a cylinder passage connecting the reservoir R and the pressure-side chamber R2. The pressure-side port 3d is provided in the piston 3 and functions as a piston passage connecting the pressure-side chamber R2 and the extension-side chamber R1. The partition wall 20, stopper 21, and coil spring 22 can open and close the through hole 1a as the cylinder passage, and when the movable body M is positioned on the pressure-side stroke end side of the position where it contacts the partition wall 20, it opens to supply liquid from the reservoir R to the extension-side chamber R1, forming a mechanical check valve Mc.
[0070] Thus, in the buffer D of this embodiment, once the movable body M comes into contact with the partition body 20, the mechanical check valve Mc opens and liquid is supplied into the extension chamber R1 via the supply passage SP, allowing for smooth contraction operation.
[0071] Furthermore, if the shock absorber D contracts after the moving body M contacts the partition wall 20, eliminating the through-hole 1a would allow liquid from chamber A (excluding pressure chamber PR) of the pressure-side chamber R2 to move to the extension-side chamber R1 through the pressure-side port 3d. However, the pressure-side chamber R2 would only supply less liquid than is needed in the extension-side chamber R1. Therefore, if the through-hole 1a is eliminated, a supply passage should be provided that connects the reservoir R and the extension-side chamber R1, enabling the supply of liquid from the reservoir R to the extension-side chamber R1. Additionally, a mechanical check valve should be provided in the supply passage that closes when the moving body M does not contact the partition wall 20, but opens when the moving body M contacts the partition wall 20. In this case, the partition wall 20, stopper 21, and coil spring 22 do not need to function as a mechanical check valve. Even when the shock absorber D is configured in this way, the shock absorber D can still contract smoothly even if the shock absorber D contracts after the moving body M contacts the bulkhead 20. Furthermore, if the bulkhead 20, stopper 21, and coil spring 22 do not need to function as a mechanical check valve Mc, the stopper 21 only needs to restrict the upward movement of the bulkhead 20. Therefore, the structure and shape of the stopper 21 can be arbitrarily designed to that extent, and it may have a shape other than an annular one.
[0072] Furthermore, in this embodiment, the stopper 21 is equipped with a base portion 21a to connect the upper portion 1b and the lower portion 1c of the cylinder 1, making it easy to install on the cylinder 1. A stopper portion 21b having a uniform surface that closely adheres to the upper end of the cylindrical portion 20a of the partition wall 20 can be provided. By using the stopper portion 21b as the valve seat of the mechanical check valve Mc, when the pressure in the pressure chamber R2 rises, it tightly contacts the partition wall 20 and closes the through-hole 1a, preventing leakage of liquid from the through-hole 1a and allowing the buffer D to generate damping force as intended when it contracts. The through-hole 1a may function as an orifice that provides resistance to the flow of liquid moving from the reservoir R into the cylinder 1, or it may be a hole with an opening area that does not provide resistance to the flow of the liquid. If the through-hole 1a is an orifice, even if the mechanical check valve Mc fails to close properly when the buffer D contracts while the partition wall 20 and the movable body M are separated, the buffer D can still generate a compression damping force by increasing the pressure inside the cylinder 1 through the through-hole 1a.
[0073] In the cylinder 1, the piston 3 of the movable body M slides against the upper portion 1b and is positioned radially, while the partition wall 20 slides against the lower portion 1c of the cylinder 1 and is positioned radially. However, since the pressure chamber PR is formed when the partition wall 20 abuts against the movable body M, even if the movable body M and the partition wall 20 are radially eccentric relative to each other, the pressure chamber PR can be formed without any problems when the movable body M and the partition wall 20 abut against each other, and the movable body M and the partition wall 20 do not interfere with each other's axial movement and can move smoothly together within the cylinder 1.
[0074] In the shock absorber D of this embodiment, the piston nut 9 in the movable body M is in contact with the partition wall 20, so that the partition wall 20 does not interfere with the extension damping valve 5 stacked on the piston 3, and the load due to the pressure in the pressure chamber PR does not act on the extension damping valve 5 and cause fatigue of the extension damping valve 5. Alternatively, a flat surface that contacts the partition wall 20 may be provided at the tip of the piston rod 2, or a part having a flat surface that contacts the partition wall 20 may be attached, so that the opposing portion 20b of the partition wall 20 faces the flat surface, and the pressure chamber PR is formed by the contact between the piston rod 2 and the partition wall 20. In this case as well, the partition wall 20 does not interfere with the extension damping valve 5 stacked on the piston 3, and the load due to the pressure in the pressure chamber PR does not act on the extension damping valve 5 and cause fatigue of the extension damping valve 5. Thus, when the moving body M closes the communication hole 20c of the partition wall 20 by abutting the tip of the piston rod 2 or a part attached to the tip against the partition wall 20 to form a pressure chamber PR, the partition wall 20 may be composed of a cylindrical portion 20a, a lid that closes the upper end of the cylindrical portion 20a, and a communication hole provided in the lid that is closed by the tip of the piston rod 2 or a part attached to the tip. Therefore, the partition wall 20 does not have to be annular in shape as a whole, and it is sufficient that when it is not in contact with the moving body M, the upper and lower chambers of the partition wall 20 in Figure 1 in the pressure side chamber R2 are connected via the communication hole 20c, and when the communication hole 20c is closed by contact with the moving body M, the upper and lower chambers of the pressure side chamber R2 are blocked together with the moving body M, thereby forming a pressure chamber PR.
[0075] In addition, when providing a stopper on the cylinder 1 to restrict the movement of the partition wall 20 instead of the stopper 21, the cylinder 1 may be crimped from the outside to plastically deform a part of the cylinder 1 so that its inner diameter becomes smaller, and the stopper may be formed in the part of the cylinder 1 whose inner diameter has been reduced. Alternatively, an annular groove may be provided on the inner circumference of the cylinder 1 and a snap ring fitted into the annular groove may be used as the stopper. When using a snap ring as a stopper, since the snap ring is C-shaped with a split at one point in the circumferential direction, the outer circumference of the partition wall 20 may be brought into sliding contact with the inner circumference of the cylinder 1, and the movement of the partition wall 20 may be restricted by the stopper. In this state, a groove may be provided on the outer circumference of the partition wall 20 that opens from the upper end and faces the through hole 1a, and the partition wall 20 may be positioned so that the groove does not face the split of the snap ring, so that when the partition wall 20 comes into contact with the snap ring, the groove is closed by the snap ring.
[0076] Furthermore, in the buffer D of the embodiment described above, the partition wall 20 is in sliding contact with the inner circumference of the cylinder 1. When the movable body M and the partition wall 20 come into contact to form a pressure chamber PR, the effective pressure-receiving area where the partition wall 20 and the movable body M receive the pressure of the pressure chamber PR can be made approximately equal to the area of a circle with the inner diameter of the cylinder 1, thereby maximizing the effective pressure-receiving area. Alternatively, an inner cylinder may be provided that is connected to the valve case 10 and housed in the pressure-side chamber R2 of the cylinder 1, with an inner diameter larger than the outer diameter of the piston rod 2 and its inner side communicating with the discharge port 10d. An annular partition wall 20 is then in sliding contact with the inside of this inner cylinder, so that when the partition wall 20 and the movable body M come into contact, a pressure chamber PR is formed inside the inner cylinder. Even when an inner cylinder is provided in this manner, when the movable body M abuts against the partition wall 20 and a pressure chamber PR is formed inside the inner cylinder, the effective pressure-receiving area of the partition wall 20 and the movable body M that receives the pressure from the pressure chamber PR becomes approximately equal to the area of a circle with the inner diameter of the inner cylinder as its diameter. Therefore, even when an inner cylinder is provided and the partition wall 20 is slidably inserted into the inner cylinder in this manner, when the movable body M and the partition wall 20 are in contact, the effective pressure-receiving area that receives the pressure in the pressure chamber PR in a direction that prevents the movable body M and the partition wall 20 from moving toward the compression stroke end becomes larger than the cross-sectional area of the piston rod. Therefore, even when the shock absorber D is configured in this manner, when the movable body M and the partition wall 20 come into contact during the contraction operation of the shock absorber D, the compression damping force generated by the shock absorber D is increased, and the contraction operation of the shock absorber D can be suppressed.
[0077] As described above, the buffer D of this embodiment includes a cylinder 1, a piston rod 2 inserted into the cylinder 1 so as to be movable in the axial direction, a piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be movable in the axial direction, and a movable body M that is allowed to move in the axial direction relative to the cylinder 1 and divides the inside of the cylinder 1 into an extension chamber R1 and a compression chamber R2, a reservoir R for storing liquid, a pressure damping valve 12 that provides resistance to the flow of liquid from the compression chamber R2 to the reservoir R, and a movable body that is allowed to move in the axial direction relative to the cylinder 1 within the compression chamber R2 The device includes a partition body 20 that is housed within the device and, when it comes into contact with the movable body M, forms a pressure chamber PR within the pressure-side chamber R2 that leads to the pressure-side damping valve 12 together with the movable body M, and a supply passage SP that enables the supply of liquid from the reservoir R to the extension-side chamber R1 when the movable body M is positioned on the pressure-side stroke end side of the position where it comes into contact with the partition body 20. When the movable body M and the partition body 20 are in contact, the pressure-receiving area that receives pressure in the pressure chamber PR in a direction that prevents the movable body M and the partition body 20 from moving toward the pressure-side stroke end side is larger than the cross-sectional area of the piston rod 2.
[0078] With the shock absorber D configured in this embodiment, when the movable body M comes into contact with the bulkhead 20 during the contraction operation, the damping force generated by the shock absorber D increases, and the force hindering the contraction operation of the shock absorber D becomes greater. Therefore, with the shock absorber D in this embodiment, the compression damping force is increased when the shock absorber D is contracted to near the compression stroke end, so the contraction operation of the shock absorber D can be sufficiently suppressed, and the damping force during the contraction operation of the shock absorber D does not become excessive until it reaches near the compression stroke end, so the ride comfort in the vehicle is not impaired. As described above, with the shock absorber D in this embodiment, a high damping force can be generated near the compression stroke end without impairing the ride comfort in the vehicle.
[0079] Furthermore, in the buffer D of this embodiment, when the pressure chamber PR is reduced while the movable body M and the partition body 20 are in contact, the entire flow rate corresponding to the volume of the reduced pressure chamber PR passes through the pressure-side damping valve 12.
[0080] With the buffer D configured in this way, if the contraction speed is the same, the flow rate passing through the pressure-side damping valve 12 when the movable body M and the partition body 20 are in contact increases compared to when the buffer D contracts when the movable body M and the partition body 20 are not in contact. As a result, the pressure in the pressure chamber PR when the movable body M and the partition body 20 are in contact becomes higher than the pressure inside the cylinder 1 when the movable body M and the partition body 20 are not in contact, significantly increasing the damping force and suppressing the contraction operation.
[0081] Furthermore, in the buffer D of this embodiment, the supply passage SP includes a through hole (cylinder passage) 1a provided in the cylinder 1 that connects the reservoir R and the pressure side chamber R2, a pressure side port (piston passage) 3d provided in the piston 3 that connects the pressure side chamber R2 and the extension side chamber R1, and a mechanical check valve Mc that can open and close the through hole (cylinder passage) 1a and opens when the movable body M is positioned on the pressure side stroke end side of the position where it contacts the partition wall 20, thereby supplying liquid from the reservoir R to the extension side chamber R1.
[0082] With the buffer D of this embodiment configured as described above, when the movable body M contacts the partition wall 20, the mechanical check valve Mc opens, and the liquid that is insufficient in the extension chamber R1 can be supplied from the reservoir R to the extension chamber R1 via the supply passage SP. Therefore, even if the liquid that exceeds the volume of the piston rod 2 entering the cylinder 1 from the pressure chamber PR is discharged to the reservoir R when the movable body M contacts the partition wall 20, liquid is supplied from the reservoir R to the extension chamber R1 via the supply passage SP. This allows for smooth contraction operation while increasing the damping force, and since the supply passage SP is closed until the movable body M contacts the partition wall 20, the damping force can be exerted as in the conventional manner.
[0083] Furthermore, the buffer D of this embodiment is provided with a stopper on the cylinder 1 that, when it comes into contact with the partition wall 20, restricts the movement of the partition wall 20 toward the anti-pressure side stroke end. The cylinder 1 has a through hole 1a that connects the reservoir R and the pressure side chamber R2. The partition wall 20 is annular in shape and can move axially within the pressure side chamber R2 by sliding its outer circumference against the inner circumference of the cylinder 1. When it comes into contact with the stopper 21, it prevents the passage of liquid through the through hole 1a together with the stopper 21, and when it comes into contact with the movable body M and moves toward the pressure side stroke end relative to the stopper 21 together with the movable body M, it opens the through hole 1a.
[0084] With the buffer D configured in this way, when the moving body M comes into contact with the partition wall 20, the partition wall 20 is separated from the stopper 21, and the inside of the cylinder 1 and the reservoir R are connected through the through hole 1a. Therefore, even if the volume of liquid exceeding the volume of the piston rod 2 entering the cylinder 1 from the pressure chamber PR is discharged to the reservoir R when the moving body M comes into contact with the partition wall 20, liquid is supplied from the reservoir R to the extension chamber R1 through the through hole 1a. This allows for smooth contraction operation while increasing the damping force, and since the through hole 1a is closed until the moving body M comes into contact with the partition wall 20, the damping force can be exerted as in the conventional manner. Furthermore, according to the buffer D of this embodiment, the stopper 21 and the partition wall 20 used in the pressure chamber PR constitute a mechanical check valve Mc that opens and closes the through hole 1a. By moving the partition wall 20 away from the stopper 21 with the movable body M, the through hole 1a can be opened and the pressure chamber PR can be formed. This simplifies the structure of the buffer D and minimizes the increase in the number of parts.
[0085] Furthermore, in the buffer D of this embodiment, the partition wall 20 is configured to form a pressure chamber PR within the compression chamber R2 together with the movable body M when it comes into contact with the piston nut 9 which is screw-connected to the outer circumference of the piston rod 2. With the buffer D of this embodiment configured in this way, since the piston nut 9 on the movable body M comes into contact with the partition wall 20, the partition wall 20 does not interfere with the extension damping valve 5 which is stacked on the piston 3, and the load due to the pressure in the pressure chamber PR does not act on the extension damping valve 5 and cause fatigue of the extension damping valve 5. Alternatively, a flat surface that contacts the partition body 20 may be provided at the tip of the piston rod 2, or a component having a flat surface that contacts the partition body 20 may be attached, so that the opposing portion 20b of the partition body 20 faces the flat surface, and the pressure chamber PR is formed by the contact between the piston rod 2 and the partition body 20. In this case as well, the partition body 20 will not interfere with the extension damping valve 5 stacked on the piston 3, and the load due to the pressure of the pressure chamber PR will not act on the extension damping valve 5 and cause fatigue of the extension damping valve 5.
[0086] Furthermore, in the buffer D of this embodiment, the outer circumference of the partition wall 20 is in sliding contact with the inner circumference of the cylinder 1. With the buffer D configured in this way, since the partition wall 20 is in sliding contact with the inner circumference of the cylinder 1, when the movable body M and the partition wall 20 come into contact to form a pressure chamber PR, the effective pressure-receiving area on the partition wall 20 and the movable body M that receives the pressure of the pressure chamber PR can be made approximately equal to the area of a circle with the inner diameter of the cylinder 1, thereby maximizing the effective pressure-receiving area. This further increases the compression damping force when the partition wall 20 and the movable body M are in contact and the buffer is contracting, allowing the contraction operation to be suppressed more efficiently.
[0087] 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.
[0088] 1...Cylinder, 1a...Through hole (cylinder passage), 2...Piston rod, 3...Piston, 3d...Compression port (piston passage), 9...Piston nut, 12...Compression damping valve, 20...Partition body, 20c...Communication hole, 21...Stopper, D...Buffer, M...Moving body, Mc...Mechanical check valve, PR...Pressure chamber, R...Reservoir, R1...Extension chamber, R2...Compression chamber, SP...Supply passage
Claims
1. A movable body that is allowed to move axially relative to the cylinder, including a cylinder; a piston rod inserted into the cylinder 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, and which divides the inside of the cylinder into an extension chamber and a compression chamber; a reservoir for storing liquid; a compression damping valve that provides resistance to the flow of liquid from the compression chamber to the reservoir; a partition wall body housed in the compression chamber so as to be movable in the axial direction of the cylinder, having a communication hole that is closed by the movable body when it comes into contact with the movable body, and together with the movable body, forming a pressure chamber in the compression chamber that leads to the compression damping valve; and a supply passage that enables the supply of liquid from the reservoir to the extension chamber when positioned on the compression stroke end side of the position where the movable body comes into contact with the partition wall body. A shock absorber characterized in that, when the movable body and the partition body are in contact, the pressure-receiving area that receives pressure in the pressure chamber in a direction that prevents the movable body and the partition body from moving toward the compression stroke end is larger than the cross-sectional area of the piston rod.
2. The buffer according to claim 1, characterized in that when the pressure chamber is reduced in a state in which the movable body and the partition body are in contact, the entire flow rate of the volume of the reduced pressure chamber passes through the pressure-side damping valve.
3. The buffer according to claim 1, characterized in that the supply passage comprises a cylinder passage provided in the cylinder and connecting the reservoir and the pressure chamber, a piston passage provided in the piston and connecting the pressure chamber and the extension chamber, and a mechanical check valve that can open and close the cylinder passage and opens when positioned on the pressure stroke end side of the position where the moving body abuts the partition wall, thereby supplying liquid from the reservoir to the extension chamber.
4. The buffer according to claim 1, comprising a stopper provided on the cylinder that, when in contact with the partition wall, restricts the movement of the partition wall toward the anti-pressure side stroke end, the cylinder having a through hole connecting the reservoir and the pressure side chamber, the partition wall being movable in the axial direction within the pressure side chamber with its outer circumference sliding against the inner circumference of the cylinder, preventing the passage of liquid through the through hole together with the stopper when in contact with the stopper, and opening the through hole when in contact with the movable body and moving toward the pressure side stroke end relative to the stopper together with the movable body.
5. The buffer according to claim 1, characterized in that when the partition wall comes into contact with the tip of the piston rod, a component attached to the tip of the piston rod, or a piston nut screw-connected to the outer circumference of the piston rod, it together with the moving body forms the pressure chamber within the pressure chamber.
6. The buffer according to claim 1, characterized in that the outer circumference of the partition wall is in sliding contact with the inner circumference of the cylinder.