Shock absorber

Abstract

A shock absorber (D) according to the present invention is provided with: a cylinder (1); a piston rod (2) that is inserted into the cylinder (1) so as to be movable in the axial direction; a piston (3) that partitions the inside of the cylinder (1) into an extension-side room (R1) and a compression-side room (R2), and that has a port (3b) connecting the extension-side room (R1) and the compression-side room (R2); a tank (T) that has a liquid chamber (L) filled with a liquid and a gas chamber (G) pressurizing the liquid chamber (L); a compensation passage (10d) that connects the liquid chamber (L) and the compression-side room (R2); a valve element (V) that applies resistance to the flow of a liquid passing through the compensation passage (10d) from the compression-side room (R2) toward the liquid chamber (L); and a shutter (20) that is accommodated in the compression-side room (R2), that is movable in the axial direction with respect to the cylinder (1), that has an annular shape closing at least a portion of the port (3b) when in contact with the piston (3), and the outer diameter of which is larger than the outer diameter of the piston rod (2).

Description

Shock absorber

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

[0002] The shock absorber includes, for example, a cylinder, a piston rod movably inserted into the cylinder, a piston connected to the piston rod, movably inserted into the cylinder and partitioning the interior of the cylinder into an extension-side chamber and a compression-side chamber both filled with hydraulic oil, a tank having a liquid chamber communicated with the compression-side chamber and filled with hydraulic oil and an air chamber filled with gas for pressurizing the liquid chamber, an extension-side leaf valve mounted on the piston rod and provided on the piston for opening and closing an extension-side port communicating the extension-side chamber with the compression-side chamber, and a compression-side damping valve provided in a passage communicating the compression-side chamber with the liquid chamber and applying resistance to the flow of hydraulic oil passing through the passage.

[0003] The conventional shock absorber configured as described above is used, for example, installed between a vehicle body and wheels of a vehicle. During an extension operation in which 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 to generate an extension-side damping force that impedes the extension operation. During a compression operation in which the piston moves relative to the cylinder in a direction that reduces the volume of the compression-side chamber, the compression-side damping valve applies resistance to the flow of hydraulic oil from the compression-side chamber toward the liquid chamber of the tank to generate a compression-side damping force that impedes the compression operation, thereby damping vibration of the vehicle body.

[0004] Furthermore, in a conventional shock absorber, as disclosed in, for example, JP2021-148282A, when the piston is displaced to the vicinity of the compression-side stroke end during a 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 rod guide mounted on the rod-side end of the cylinder and is compressed, generating an elastic force that suppresses further displacement of the shock absorber toward the compression side. Therefore, in the conventional shock absorber, when the compression operation proceeds to the vicinity of the compression-side stroke end, the elastic force generated by the bump cushion rubber is added to the compression-side damping force generated by the compression-side damping valve to impede the compression operation, thereby mitigating the impact at the maximum compression.

[0005] JP2021-148282A

[0006] In conventional shock absorbers, as mentioned above, when the shock absorber is in a state where it is about to fully compress, the elastic 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 elastic force, there is a possibility that the force to suppress the contraction operation will 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 piston connected to the piston rod and inserted into the cylinder so as to be movable in the axial direction, having a port that divides the inside of the cylinder into an extension chamber and a compression chamber and connects the extension chamber and the compression chamber, a tank having a liquid chamber filled with liquid and a gas chamber filled with gas, a compensating passage connecting the liquid chamber and the compression chamber, and a shutter that slides against the inside of the cylinder and is movable in the axial direction relative to the cylinder, and closes at least a part of the opening end of the port when it comes into contact with the piston.

[0011] With a shock absorber configured in this way, when the piston and shutter come into contact 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 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 the buffer in one embodiment. Figure 3 is a partially enlarged cross-sectional view of the buffer in one embodiment when the shutter is in contact with the piston. Figure 4 is a partially enlarged cross-sectional view of the buffer in one embodiment when the piston is in contact with the shutter and has reached its limit of movement.

[0013] The present invention will be described based on the embodiments shown in the figures. As shown in Figure 1, the shock absorber 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 piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be movable in the axial direction, dividing the inside of the cylinder 1 into an extension chamber R1 and a compression chamber R2, a tank T having a liquid chamber L filled with liquid and an air chamber G that pressurizes the liquid chamber L, a compensation passage 10d connecting the liquid chamber L and the compression chamber R2, a valve element V that provides resistance to the flow of liquid passing through the compensation passage 10d from the compression chamber R2 to the liquid chamber L, and a shutter 20 that slides against the cylinder 1 and is movable in the axial direction relative to the cylinder 1. The shock absorber D, although not shown, is interposed between the vehicle body and the rear wheels in a saddle-type vehicle, for example, to generate a damping force during expansion and contraction to suppress vibrations of the vehicle body. The shock absorber D may be used in vehicles other than saddle-type vehicles, such as automobiles, or in equipment other than vehicles, buildings, etc.

[0014] 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 below the piston 3 in Figure 1 and a compression chamber R2 above the piston 3 in Figure 1. Both the extension chamber R1 and the compression chamber R2 inside the cylinder 1 are filled with hydraulic fluid as a liquid.

[0015] The upper end of cylinder 1 in Figure 1 is closed by a head cap 10, and an annular rod guide 11, an annular sealing member 12, and an annular bump stopper 13 are housed on the inner circumference of the lower end of cylinder 1 in Figure 1, through which the piston rod 2 is inserted inward.

[0016] The head cap 10 includes a top-shaped cylindrical cap portion 10a that is screw-connected to the outer circumference of the upper end of the cylinder 1 and fixed to the cylinder 1 with its upper end closed, a top-shaped cylindrical tank holding portion 10b that is positioned to the side of the cap portion 10a and holds the tank T, a connecting portion 10c that extends laterally from the side of the top of the cap portion 10a and connects to the top of the tank holding portion 10b, a compensation passage 10d that opens from the top of the cap portion 10a, passes through the connecting portion 10c and leads to the lower end of the tank holding portion 10b, and a bracket 10e that is attached to the upper end of the top of the cap portion 10a.

[0017] A cylindrical tank housing 15 is attached to the outer circumference of the lower end of the tank holding portion 10b by screw connection. A tank cap 16 that airtightly seals the inside of the tank housing 15 is attached to the inner circumference of the lower end of the tank housing 15, and a bladder 17 that divides the inside of the tank housing 15 into a liquid chamber L and an air chamber G is housed inside the tank housing 15. Thus, the tank T is formed by the tank housing 15, the tank cap 16 and the bladder 17, and its interior is divided by the bladder 17 into a liquid chamber L filled with hydraulic fluid as a liquid and an air chamber G filled with gas. The liquid chamber L and air chamber G in the tank T may be separated by a free piston slidably inserted into the tank housing 15, or by an elastic partition or a metal bellows. The liquid chamber L in the tank T is filled with the same hydraulic fluid as the hydraulic fluid that fills the extension chamber R1 and compression chamber R2 in the cylinder 1. The liquids filling the extension chamber R1 and compression chamber R2 in cylinder 1 and the liquid chamber L in tank T may be liquids other than hydraulic oil. Furthermore, a gas at atmospheric pressure or higher may be sealed in the gas chamber G to pressurize the inside of cylinder 1 via the liquid chamber L. Pressurizing the inside of cylinder 1 increases the rigidity of the oil column and improves the damping force generation response. The tank T may also be configured with an open gas chamber G to the atmosphere, a free piston separating the liquid chamber L from the gas chamber G, and an elastic body such as a spring that biases an elastic partition or metal bellows in the direction of compression of the liquid chamber L. Configuring the tank T in this way eliminates the need to secure the volume of the gas chamber G, thus shortening the overall length of the tank T.

[0018] When the head cap 10 is attached to the upper end of the cylinder 1 in Figure 1, the pressure chamber R2 inside the cylinder 1 is connected to the liquid chamber L inside the tank T via the compensation passage 10d. A valve element V, which is an orifice, is provided in the middle of the compensation passage 10d. In addition to the orifice, the valve element V may also consist of, for example, a valve that provides resistance to the flow of hydraulic fluid from the pressure chamber R2 to the liquid chamber L in the compensation passage 10d, and a check valve placed in parallel with the valve that allows the flow of hydraulic fluid from the liquid chamber L to the pressure chamber R2 in the compensation passage 10d with almost no resistance, but blocks the flow of hydraulic fluid in the reverse direction.

[0019] The rod guide 11 is housed on the inner circumference of the lower end of the cylinder 1 in Figure 1, together with a bump stopper 13 formed by an annular sealing member 12 and an annular plate stacked below the rod guide 11 in Figure 1. The rod guide 11 is fixed to the cylinder 1 by crimping the portion of the cylinder 1 that faces the rod guide 11 from the outer circumference of the cylinder 1. The sealing member 12 and the bump stopper 13 are fixed inside the cylinder 1 by being sandwiched between the rod guide 11 and the crimped portion of the lower end of the cylinder 1 by crimping the lower end of the cylinder 1. The sealing member 12 seals the space between the cylinder 1 and the piston rod 2, preventing leakage of hydraulic fluid from inside the buffer D.

[0020] Alternatively, instead of crimping the lower end opening of the cylinder 1, a top-shaped cylindrical cap that also functions as a bump stopper may be screwed onto the lower end opening of the cylinder 1, and the sealing member 12 may be sandwiched between the rod guide 11 and the cap, thereby fixing these members inside the cylinder 1.

[0021] The piston rod 2 is cylindrical with a reduced outer diameter at the tip, and includes a piston fitting portion 2a with the smallest diameter at the tip, a large-diameter portion 2b which has a larger outer diameter than the piston fitting portion 2a and is located below the piston fitting portion 2a in Figure 1, a stepped portion 2c provided at the boundary between the piston fitting portion 2a and the large-diameter portion 2b, and a locking portion 2d which is formed by crimping an annular projection provided on the outer circumference of the tip of the piston fitting portion 2a to expand its diameter toward the outer circumference.

[0022] A bracket 18 is provided at the base end of the piston rod 2, which is the lower end in Figure 1, and the piston rod 2 is connected to a wheel of a saddle-type vehicle (not shown) via the aforementioned bracket (not shown). In addition, a bracket 10e provided on the head cap 10 that closes the upper end of the cylinder 1 is connected to the vehicle body of a saddle-type vehicle (not shown).

[0023] As described above, the shock absorber D of this embodiment is interposed between the vehicle body and the wheel in a saddle-type vehicle by connecting the piston rod 2 to the wheel and the cylinder 1 to the vehicle body. When the saddle-type vehicle travels on an uneven road surface, causing the wheel to vibrate up and down 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 up and down (axially) within the cylinder 1. As described above, the piston rod 2 is connected to the wheel and the cylinder 1 is connected to the vehicle body, but the piston rod 2 may be connected to the vehicle body and the cylinder 1 may be connected to the wheel, and the shock absorber D may be interposed between the vehicle body and the wheel in a saddle-type vehicle.

[0024] In Figure 1, the outer circumference of the lower end of the piston rod 2 is fitted with a rod-side spring receiver 30, a nut 34 that is screw-connected to the lower end of the piston rod 2 to fix the rod-side spring receiver 30, and a cylindrical bump cushion rubber 31 that is mounted on the outer circumference of the piston rod 2 and stacked on the nut 34. A cylindrical cylinder-side spring receiver 32 is fitted on the outer circumference of the cylinder 1. A suspension spring 33 made of a coil spring is provided between the rod-side spring receiver 30 and the cylinder-side spring receiver 32. Therefore, when the shock absorber D is installed between the vehicle body and the wheels, the suspension spring 33 compresses and generates elastic force, and the vehicle body is elastically supported by the suspension spring 33. Furthermore, when the shock absorber D undergoes 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 13 and is compressed between the bump stopper 13 and the nut 34, generating an elastic force that prevents the shock absorber D from contracting.

[0025] Next, the piston 3 is annular in shape and, together with the annular valve stopper 4 and the annular insertion member 5, is fitted onto the outer circumference of the piston fitting portion 2a of the piston rod 2. It is held in place by the stepped portion 2c and the locking portion 2d of the piston rod 2 and fixed to the piston rod 2, dividing the inside of the cylinder 1 into an extension chamber R1 and a compression chamber R2.

[0026] More specifically, as shown in Figures 1 and 2, the piston 3 comprises an annular piston body 3a and a plurality of ports 3b that penetrate the piston body 3a axially and connect the extension chamber R1 and the compression chamber R2. The outer circumferential surface of the piston body 3a slides against the inner circumferential surface of the cylinder 1, and the piston 3 can move together with the piston rod 2 in the vertical direction in Figure 1, which is the axial direction of the cylinder 1, using the cylinder 1 as a guide.

[0027] Furthermore, as shown in Figure 2, the piston 3 is equipped with an annular recess 3c formed on the inner circumference of the lower end of the piston body 3a and an annular window 3d which is an annular groove provided at the lower end of the piston body 3a. Multiple ports 3b are provided on the same circumference of the piston body 3a at equal intervals along the circumferential direction, and each opens from the bottom of the annular window 3d and leads to the upper end of the piston body 3a.

[0028] The valve stopper 4 comprises a cylindrical portion 4a that fits onto the outer circumference of the piston fitting portion 2a of the piston rod 2, a flange 4b ​​that protrudes radially from the outer circumference of the cylindrical portion 4a from the lower end to near the center in Figure 2 and faces the lower end of the piston body 3a in the axial direction in Figure 2, and an annular projection 4c that protrudes toward the piston side from the outer circumference of the upper end in Figure 2 of the flange 4b, and is stacked on the lower side of the piston 3 in Figure 2.

[0029] The valve stopper 4 is stacked on the piston 3 with the upper end of its cylindrical portion 4a inserted into the annular recess 3c of the piston 3 and in contact with the bottom of the annular recess 3c. Together with the piston 3, it is fitted onto the outer circumference of the piston fitting portion 2a and is held together with the piston 3 by the stepped portion 2c and the locking portion 2d, thereby being fixed immovably to the piston rod 2.

[0030] A valve 40 for opening and closing a port 3b is provided in the lower part of Figure 2, which is on the extension chamber side of the piston body 3a of the piston 3. As shown in Figure 2, the valve 40 comprises an annular spacer 41 stacked on the lower end of the inner circumference side of the piston body 3a, an annular extension valve body 42 stacked on the opposite side of the spacer 41 and having an outer diameter larger than the spacer 41, larger than the inner diameter of the annular window 3d of the piston 3, and smaller than the outer diameter of the annular window 3d, an annular extension valve body 42 stacked on the opposite side of the extension valve body 42 and having an outer diameter larger than the outer diameter of the annular window 3d and smaller than the outer diameter of the piston 3, and a spring 44 that biases the spacer 41, the extension valve body 42, and the compression valve body 43 toward the piston 3.

[0031] The spacer 41 is annular in shape and is fitted to the outer circumference of the cylindrical portion 4a of the valve stopper 4 so as to be movable in the axial direction, and can seat between the annular recess 3c of the piston body 3a and the annular window 3d. The extension valve body 42 is annular in shape and is fitted to the outer circumference of the cylindrical portion 4a of the valve stopper 4, and when its inner circumference is supported by the spacer 41 when seated between the annular recess 3c of the piston body 3a and the annular window 3d, the pressure of the extension chamber R1 can cause its outer circumference to bend towards the back of the annular window 3d, towards the upper side in Figure 2.

[0032] As described above, the compression valve body 43 has an outer diameter larger than the outer diameter of the annular window 3d and is stacked on the side opposite the piston of the extension valve body 42. When viewed from the piston body 3a, the height of the outer circumference side of the annular window 3d of the piston body 3a is higher than the height of the inner circumference side of the annular window 3d of the piston body 3a and is slidably fitted to the outer circumference of the cylindrical portion 4a together with the spacer 41 and the extension valve body 42. The compression valve body 43 is also provided with a hole 43a that faces the annular window 3d of the piston body 3a in the axial direction and is opened and closed by the extension valve body 42.

[0033] The spring 44 is an annular wave washer interposed between the flange 4b ​​of the valve stopper 4 and the compression valve body 43, biasing the spacer 41, the extension valve body 42, and the compression valve body 43 toward the piston 3. Note that the spring 44 only needs to be able to bias the spacer 41, the extension valve body 42, and the compression valve body 43; therefore, it may be a coil spring or other elastic body in addition to a wave washer.

[0034] Then, when the spacer 41, extension valve body 42, and compression valve body 43 are stacked together and the outer circumferences of the spacer 41 and compression valve body 43 seat on the piston body 3a, the valve 40 closes and blocks the port 3b in the piston 3.

[0035] Furthermore, when the spacer 41, extension valve body 42, and compression valve body 43 are stacked and the pressure in the extension chamber R1 becomes higher than the pressure in the compression chamber R2, the extension valve body 42, whose inner circumference is supported by the piston body 3a, bends its outer circumference upward in Figure 2 due to the pressure of the extension chamber R1 acting through the hole 43a of the compression valve body 43, separating it from the compression valve body 43 and opening the hole 43a, thereby allowing the hydraulic fluid to move from the extension chamber R1 to the compression chamber R2, while the extension valve body 42 also provides resistance to the flow of the hydraulic fluid. In this way, the valve 40 opens the valve by bending the extension valve body 42 in response to the flow of hydraulic fluid from the extension chamber R1 to the compression chamber R2 through port 3b, while also providing resistance to the flow of the hydraulic fluid.

[0036] On the other hand, when the spacer 41, extension valve body 42, and compression valve body 43 are stacked and the pressure in the compression chamber R2 becomes higher than the pressure in the extension chamber R1, the extension valve body 42 and the compression valve body 43 are pushed downward in Figure 2 by the pressure in the compression chamber R2 acting through port 3b, and the spring 44 is compressed as the extension valve body 42 and the compression valve body 43 come into contact with each other, separating them from the piston body 3a and opening port 3b. In this way, the valve 40 allows the flow of hydraulic fluid from the compression chamber R2 to the extension chamber R1 through port 3b by separating the extension valve body 42 and the compression valve body 43 from the piston body 3a to a position where they contact the annular projection 4c of the valve stopper 4, forming a large gap between them and the piston body 3a, thereby allowing the flow of hydraulic fluid. Therefore, the valve 40 opens port 3b wide to allow the flow of hydraulic fluid from the compression chamber R2 to the extension chamber R1, thereby allowing the flow of hydraulic fluid with almost no resistance.

[0037] As described above, the valve 40 is stacked on the extension chamber side of the piston 3, and functions as a damping valve that allows the flow of hydraulic fluid from the extension chamber R1 to the compression chamber R2 while providing resistance to the flow, and functions as a check valve that allows the flow of hydraulic fluid from the compression chamber R2 to the extension chamber R1 with almost no resistance to the flow.

[0038] Furthermore, an annular insertion member 5 is stacked above the piston 3 in Figure 2. The insertion member 5 is annular and is 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 being sandwiched between the piston 3 and the valve stopper 4 by the stepped portion 2c and the locking portion 2d. Since the insertion member 5 has a tapered portion 5a on the outer circumference of its lower end, when it is stacked on the upper end of the piston body 3a in Figure 2, it does not interfere with the opening end of the port 3b and does not block the port 3b. Note that the insertion member 5 does not need to have the tapered portion 5a if it does not block the port 3b. Alternatively, the insertion member 5 may be integrated with the piston 3 at the compression chamber side end and constitute a single part together with the piston 3.

[0039] Next, as shown in Figure 2, the shutter 20 includes an annular guide portion 20a that slides against the inner circumference of the cylinder 1, a cylindrical portion 20b that rises downward from the inner circumference side of the guide portion 20a toward the piston 3 side, an annular shutter portion 20c provided at the piston-side end of the cylindrical portion 20b that closes the port 3b when it comes into contact with the piston 3, and a hole 20d that penetrates the cylindrical portion 20b and communicates the inside and outside of the cylindrical portion 20b.

[0040] The guide portion 20a has its outer circumferential surface sliding in contact with the inner circumferential surface of the upper end of the cylinder 1 in Figure 1. Since the guide portion 20a is guided by the cylinder 1, the shutter 20 can move in the vertical direction in Figure 1, which is the axial direction, without axial wobble relative to the cylinder 1.

[0041] As shown in Figure 2, the cylindrical portion 20b is connected to the lower end of the guide portion 20a, has an outer diameter smaller than the outer diameter of the guide portion 20a and a larger diameter than the inner diameter of the guide portion 20a, and an inner diameter smaller than the inner diameter of the guide portion 20a, and faces the inner circumferential surface of the cylinder 1 radially with an annular gap between them. Since the shutter 20 is equipped with the guide portion 20a and cylindrical portion 20b configured in this way, it has an outer circumferential step portion 20e on its outer circumference between the guide portion 20a and the cylindrical portion 20b, and an inner circumferential step portion 20f on its inner circumference between the guide portion 20a and the cylindrical portion 20b.

[0042] The shutter portion 20c is annular in shape and is connected to the lower end in Figure 2, which is the piston-side end of the cylindrical portion 20b. Its inner diameter is smaller than the inner diameter of the cylindrical portion 20b and slightly larger than the outer diameter of the insertion member 5, and its outer surface is flush with the outer surface of the cylindrical portion 20b. As shown in Figure 3, the lower end surface of the shutter portion 20c is a flat surface and faces the port 3b on the upper end surface of the piston body 3a in Figure 3 in the axial direction. When it comes into contact with the piston body 3a, it makes close contact with the piston body 3a and closes the open end of the port 3b.

[0043] Furthermore, as shown in Figure 3, when the piston 3 approaches the shutter 20 and the insertion member 5 is inserted into the shutter portion 20c of the shutter 20, a restricting passage 50 is formed in the narrow gap between the shutter portion 20c and the insertion member 5. Therefore, from the time the piston 3 approaches the shutter 20 and the insertion member 5 is inserted into the shutter portion 20c until the shutter portion 20c comes into contact with the piston body 3a and closes the port 3b, the pressure chamber R2 and the port 3b are connected via a passage 51 consisting of the restricting passage 50, the hole 20d, and the annular gap between the cylindrical portion 20b and the cylinder 1.

[0044] Further, a stopper ring 21 serving as a stopper is mounted on the inner circumference near the upper end of cylinder 1 in FIG. 2. When the outer peripheral stepped portion 20e of the shutter 20 abuts against the stopper ring 21, further movement of the shutter 20 toward the piston side, which is the lower side in FIG. 2, is restricted. In the shock absorber D of the present embodiment, the stopper is the stopper ring 21; however, any structure is acceptable as long as it can abut against the shutter 20 and restrict movement of the shutter 20 toward the extension chamber side. Therefore, in addition to a stopper ring, the stopper may be formed of a projection that projects toward the inner circumferential side by plastically deforming the cylinder 1, or may be formed of a component other than a stopper ring.

[0045] Further, a coil spring 22 serving as a spring member is provided between the shutter 20 and the top of the cap portion 10a of the head cap 10. The coil spring 22 biases the shutter 20 toward the stopper ring 21 side, which is the lower side in FIG. 2, and positions the shutter 20 at an initial position where the shutter 20 abuts against the stopper ring 21. Any spring member is acceptable as long as it can bias the shutter 20 so that the shutter 20 can be placed at the initial position, and within this range, a spring or elastic body other than the coil spring 22 may be used.

[0046] When the shock absorber D contracts and the piston 3 moves upward relative to the cylinder 1 and just abuts against the shutter 20 at the initial position as shown in FIG. 3, the port 3b of the piston 3 is closed by the shutter 20. The extension chamber volume A, which is the volume inside the extension chamber R1 when the piston 3 is just in contact with the shutter 20, is a value obtained by multiplying the difference between the cross-sectional area of the piston 3 and the cross-sectional area of the large-diameter portion 2b of the piston rod 2 by the distance from the upper end of the rod guide 11 to the lower end of the piston 3. The extension chamber volume A can be set by the cross-sectional area of the piston 3, the cross-sectional area of the large-diameter portion 2b of the piston rod 2, and the initial position of the shutter 20 relative to the cylinder 1.

[0047] When the shock absorber D performs a contraction operation, and after the piston 3 exactly abuts against the shutter 20, the shock absorber D further continues the contraction operation, the piston 3 and the shutter 20 integrally reduce the compression side chamber R2. Eventually, after the bump cushion rubber 31 mounted on the outer periphery of the piston rod 2 abuts against the bump stopper 13 mounted on the cylinder 1, the bump cushion rubber 31 is maximally compressed, and further contraction of the shock absorber D is restricted. As shown in Fig. 4, the piston 3 reaches the upward movement limit in Fig. 4, and the shutter 20 and the piston 3 cannot move upward any further. In other words, the shock absorber D is maximally contracted, the piston 3 reaches the compression-side stroke end, and the shock absorber D cannot contract any further. The movement of the shutter 20 is restricted when the outer peripheral step 20e between the guide portion 20a and the cylindrical portion 20b abuts against the stopper ring 21 serving as a stopper. Since the shutter 20 includes the cylindrical portion 20b, a sufficient axial distance between the piston 3 and the stopper ring 21 can be secured in a state where the shutter 20 and the piston 3 exactly abut against each other. Even when the piston 3 reaches the movement limit, the piston 3 does not abut against the stopper ring 21, so that consideration is given to prevent an unnecessary load from the stopper ring 21 from being applied to the outer peripheral portion of the piston 3. In the present embodiment, the movement limit of the piston 3 may be set by the piston 3 abutting against the stopper ring 21, the movement of the shutter 20 in the direction of compressing the compression side chamber R2 may be restricted together with the shutter 20 by the abutment between the guide portion 20a of the shutter 20 and the head cap 10, or alternatively, the movement of the shutter 20 may be restricted by the coil spring 22 reaching its solid length.

[0048] The volume increment of the extension side chamber R1, resulting from the contraction operation of the shock absorber D during the period from when the piston 3 abuts against the shutter 20 arranged at the initial position abutting against the stopper ring 21 to when the piston 3 reaches the movement limit where movement toward the compression side chamber is restricted, is defined as volume change amount B. The volume change amount B is equal to the product of the movement distance H from the position where the piston 3 abuts against the shutter 20 arranged at the initial position to the movement limit, and the cross-sectional area difference obtained by subtracting the cross-sectional area of the large diameter portion 2b of the piston rod 2 from the cross-sectional area of the piston 3.

[0049] In the shock absorber D of this embodiment, the cross-sectional area of ​​the piston 3, the cross-sectional area of ​​the piston rod 2, the travel distance H, and the volume of the extension chamber A are set so that the volume change amount B is 10% or less of the volume of the extension chamber A. In other words, in the shock absorber D of this embodiment, the volume change amount B is set to one-tenth or less of the volume of the extension chamber A.

[0050] As described above, the shock absorber D is configured, and the operation of the shock absorber D will be explained below. First, when the shock absorber D extends within the range in which the piston 3 does not contact the shutter 20, the piston rod 2 and the piston 3 move downward 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 moves through the hole 43a and port 3b in the valve 40, which pushes open the extension valve body 42, and moves into the expanded compression chamber R2. The extension valve body 42 resists the flow of hydraulic fluid through port 3b, 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. When the shock absorber D extends, the piston rod 2 retracts from the cylinder 1, causing a shortage of liquid in the cylinder 1 equivalent to the volume of liquid the piston rod 2 retracts. However, the shortage of liquid is supplied from the liquid chamber L of the tank T into the cylinder 1 via the compensation passage 10d and valve element V, thereby compensating for the volume of liquid lost when the piston rod 2 retracts from the cylinder 1.

[0051] On the other hand, when the shock absorber D retracts within a range where the piston 3 does not contact the shutter 20, the piston rod 2 and piston 3 move upward relative to the cylinder 1 in Figure 1, causing the compression chamber R2 to shrink and the extension chamber R1 to expand. As a result, the hydraulic fluid in the shrinking compression chamber R2 moves through the port 3b to the expanding extension chamber R1, where the extension valve body 42 and the compression valve body 43 move away from the piston body 3a, the valve 40 opens, and the fluid moves through the port 3b.

[0052] When the shock absorber D retracts, the piston rod 2 enters the cylinder 1, resulting in an excess of hydraulic fluid in the cylinder 1 equivalent to the volume of the piston rod 2 entering the cylinder 1. The hydraulic fluid corresponding to the volume of the piston rod 2 entering the cylinder 1 moves from the cylinder 1 to the reservoir R through the compensation passage 10d and the valve element V. The valve element V resists the flow of hydraulic fluid, increasing the pressure inside the cylinder 1. Therefore, when the shock absorber D retracts within a range where the piston 3 does not contact the shutter 20, the valve element V increases the pressure inside the cylinder 1, generating a damping force that hinders the retraction operation. In this embodiment of the shock absorber D, a valve element V is provided in the compensation passage 10d to generate a damping force that hinders the retraction operation of the shock absorber D, but the valve element V in the compensation passage 10d may be omitted. Furthermore, if the valve element V is eliminated, the shock absorber D will not generate a damping force that hinders the contraction operation when the piston 3 does not come into contact with the shutter 20. Instead, it will only generate a reaction force due to the increase in pressure within the air chamber G, as the piston rod 2 penetrates the cylinder 1 to compress the air chamber G.

[0053] Furthermore, when the shock absorber D is contracting, if the piston 3 is displaced to the vicinity of the compression stroke end, which is the limit of movement on the contraction side, the insertion member 5 is inserted into the inner circumference of the shutter portion 20c of the shutter 20, forming a restricting passage 50. When the shutter 20 is not in contact with the piston body 3a, the compression chamber R2 and the port 3b are in communication with the restricting passage 50 and the passage 51 which consists of the hole 20d and the annular gap. When the insertion member 5 is positioned outside the shutter portion 20c, the area of ​​the gap between the insertion member 5 and the shutter portion 20c is larger than the combined area of ​​the restricting passage 50 and the passage 51. Therefore, when the insertion member 5 is inserted into the shutter portion 20c, the flow area between the compression chamber R2 and the port 3b is reduced to the combined area of ​​the flow area of ​​the restricting passage 50 and the flow area of ​​the passage 51. Therefore, when the insertion member 5 is inserted into the shutter 20, the resistance applied to the flow of hydraulic fluid from the pressure chamber R2 to the port 3b increases, resulting in a higher damping force that hinders the contraction operation of the shock absorber D. By providing a restricting passage 50 between the insertion member 5 and the shutter portion 20c, and preventing them from contacting each other, the insertion member 5, which is assembled to the piston rod 2, and the shutter 20, which slides against the cylinder 1, are slightly misaligned, allowing the insertion member 5 to smoothly enter the shutter 20. Furthermore, even when the insertion member 5 is inserted into the shutter portion 20c of the shutter 20 with almost no gap, resistance is applied by the passage 51, so when the insertion member 5 is inserted into the shutter 20, the damping force that hinders the contraction operation of the shock absorber D can be increased.

[0054] Next, when the shutter 20 comes into contact with the piston 3 and the port 3b in the piston 3 is closed by the shutter 20, and then the buffer D further contracts, the hydraulic fluid cannot move from the compression chamber R2 to the extension chamber R1 because the port 3b is closed. In this state, when the piston 3 and shutter 20 move together toward the compression stroke end relative to the cylinder 1 with the port 3b closed, the hydraulic fluid cannot move from the compression chamber R2 to the extension chamber R1, so the amount of hydraulic fluid that moves from the compression chamber R2 through the compensation passage 10d and valve element V to the fluid chamber L increases.Therefore, when the piston 3 and shutter 20 move toward the compression stroke end relative to the piston 3 with the port 3b closed, the amount of hydraulic fluid passing through the valve element V increases, the pressure loss generated in the valve element V increases, and the pressure in the compression chamber R2 becomes higher than when the port 3b is not closed. In the extension chamber R1, where no hydraulic fluid is supplied, the volume of the extension chamber R1 expands, causing a decrease in pressure. Therefore, when the piston 3 and shutter 20 move toward the compression stroke end with port 3b closed, the pressure in the compression chamber R2 increases further, while the pressure in the extension chamber R1 decreases due to the pressure reduction. This increases the pressure difference between the compression chamber R2 and the extension chamber R1, and the pressure in the compression chamber R2 acts on both the piston 3 and the shutter 20, pushing them downwards in Figure 4. Consequently, when the piston 3 and shutter 20 come into contact, the shock absorber D increases the compression damping force to a very high level, hindering the compression operation of the shock absorber D.

[0055] In the buffer D of the embodiment described above, the shutter 20 is in sliding contact with the inner circumference of the cylinder 1. When the piston 3 and the shutter 20 come into contact, the pressure-receiving area of ​​the shutter 20 and the piston 3 that receives the pressure of the compression chamber R2 becomes approximately equal to the area of ​​a circle with the inner diameter of the cylinder 1 as its diameter. Therefore, the effective pressure-receiving area that receives the pressure of the compression chamber R2 can be maximized, and the compression damping force can be efficiently increased.

[0056] Therefore, in the shock absorber D of this embodiment, when the piston 3 is displaced to near the end of the compression stroke during the contraction stroke, it contacts the shutter 20, increasing the pressure in the compression chamber R2 while decreasing the pressure in the extension chamber R1, thereby significantly increasing the compression damping force and suppressing the contraction operation. When the valve element V in the compensation passage 10d is eliminated, when the piston 3 contacts the shutter 20, the pressure-receiving area of ​​the shutter 20 and the piston 3 that receives the pressure in the compression chamber R2 becomes approximately equal to the area of ​​a circle with the inner diameter of the cylinder 1 as its diameter. Furthermore, when the piston 3 contacts the shutter 20 and moves toward the contraction side, the flow rate of the hydraulic fluid moving from the compression chamber R2 through the compensation passage 10d to the liquid chamber L increases, and the compensation passage 10d itself provides resistance to this hydraulic fluid flow. As a result, the pressure in the compression chamber R2 increases, and the pressure in the air chamber G also increases, allowing the shock absorber D to generate a compression damping force that hinders the contraction operation and suppress the contraction operation. If a valve element V is not provided in the compensation passage 10d, and the flow area of ​​the compensation passage 10d is increased so that the compensation passage 10d provides almost no resistance to the flow of hydraulic fluid even when the piston 3 contacts the shutter 20 and moves to the contraction side, increasing the amount of hydraulic fluid passing through the compensation passage 10d, the amount of hydraulic fluid flowing from the pressure side chamber R2 into the liquid chamber L increases, which increases the compression amount of the air chamber G and thus increases the elastic force generated in the air chamber G. Therefore, even if the compensation passage 10d is set to provide almost no resistance to the flow of hydraulic fluid, when the piston 3 contacts the shutter 20, the elastic force of the air chamber G is increased, and the pressure-receiving area of ​​the shutter 20 and piston 3 that receives the pressure of the pressure side chamber R2 increases, so the shock absorber D can increase the force that suppresses the contraction operation and suppress the contraction operation.

[0057] Furthermore, as the shock absorber D contracts and the bump cushion rubber 31 strikes the bump stopper 13, the bump cushion rubber 13 generates elastic force. This further increases the force that hinders the contraction of the shock absorber D by adding the elastic force to the damping force it generates, thereby reducing the contraction speed. It is also possible to set the shock absorber D so that the bump cushion rubber 31 strikes the bump stopper 13 before the piston 3 contacts the shutter 20 during the contraction operation of the shock absorber D.

[0058] Furthermore, even when the port 3b of the piston 3 is closed by the shutter 20 and the piston 3 and shutter 20 move together toward the compression stroke end, the positional relationship between the piston 3 and the shutter 20 does not change, so the volume of the annular gap between the shutter 20 and the cylinder 1 does not change. Therefore, the hole 20d provided in the cylindrical portion 20b of the shutter 20 can be eliminated, but in this embodiment, the shutter 20 is provided with a hole 20d that connects the inside and outside of the shutter 20, so that the pressure difference between the inside and outside of the shutter 20 is eliminated and no pressure that would expand the diameter of the shutter 20 is applied. By providing the hole 20d in this way, the pressure difference between the inside and outside of the shutter 20 is eliminated, the stress applied to the shutter 20 is suppressed, and the deterioration of the shutter 20 can be suppressed. If the hole 20d is not provided, when the port 3b is closed with the shutter 20, the pressure inside the shutter 20 will rise along with the contraction of the buffer D, but the pressure outside the shutter 20 will not change. This will create a pressure difference between the inside and outside of the shutter 20, generating stress that causes the shutter 20 to expand in diameter. Therefore, if the hole 20d is not provided, the strength of the shutter 20 will have to be set to withstand the aforementioned stress. Thus, by providing the hole 20d in the shutter 20, the strength of the shutter 20 can be reduced, which improves the design flexibility of the shutter 20 and allows for cheaper manufacturing.

[0059] Furthermore, in the shock absorber D of this embodiment, the volume change B, which is the change in volume in the extension chamber R1 from when the piston 3 just contacts the shutter 20 in its initial position until the shock absorber D is fully retracted and the piston 3 reaches its limit of movement, is set to be one-tenth or less of the volume inside the extension chamber R1 when the piston 3 just contacts the shutter 20 in its initial position, which is the volume inside the extension chamber R1, A. Therefore, even when the shock absorber D exhibits a retraction operation and the piston 3 is fully retracted from just contacting the shutter 20 in its initial position, the volume change inside the extension chamber R1 will be 10% or less of the volume inside the extension chamber A. Here, under atmospheric pressure, the amount of air contained in the hydraulic fluid is about 10% by volume, and it is expected that the hydraulic fluid inside the cylinder 1 of the shock absorber D, which is under higher pressure than atmospheric pressure, will contain more than 10% air by volume. Therefore, if the volume change amount B is set to be one-tenth or less of the extension chamber volume A, even if the volume of the extension chamber R1 increases after the port 3b of the piston 3 is closed by the shutter 20, it is possible to prevent the gas contained in the hydraulic fluid from precipitation as bubbles in the expanded extension chamber R1, and cavitation is prevented. As a result, even when the buffer D is contracted to near its most contracted state, it can exhibit stable extension operation when it turns to extension.

[0060] As described above, when the shutter 20 contacts the piston 3, the lower end surface of the shutter portion 20c of the shutter 20 comes into close contact with the piston 3, closing the entire opening end of the port 3b. However, when the shutter 20 contacts the piston 3, it may be configured so that the shutter 20 closes at least a portion of the opening end of the port 3b. In this way, when the shutter 20 blocks not all but part of the opening end of port 3b, if the resistance due to the shutter 20 limiting the flow area of ​​port 3b is set to be greater than the resistance that the valve 40 imposes on the flow of hydraulic fluid from the compression chamber R2 to the extension chamber R1 through port 3b, then when the shutter 20 contacts the piston 3, the resistance imposes on the flow of hydraulic fluid from the compression chamber R2 to the extension chamber R1 through port 3b becomes greater. As a result, the shock absorber D can increase the damping force generated after the shutter 20 contacts the piston 3 during contraction operation compared to the damping force generated before the shutter 20 contacts the piston 3, thereby increasing the force that suppresses the contraction operation and suppressing the contraction operation. To set the system such that the resistance exerted by the shutter 20 in restricting the flow area of ​​port 3b is greater than the resistance exerted by the valve 40 on the flow of hydraulic fluid from the pressure chamber R2 to the extension chamber R1 through port 3b, for example, the flow area when the shutter 20 closes a portion of the opening end of port 3b can be set to be smaller than the flow area when the valve 40 opens port 3b.

[0061] As described above, the buffer D of this embodiment comprises 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, which divides the inside of the cylinder 1 into an extension chamber R1 and a compression chamber R2 and has a port 3b that connects the extension chamber R1 and the compression chamber R2, a tank T having a liquid chamber L filled with hydraulic fluid (liquid) and a gas chamber G filled with gas, a compensation passage 10d that connects the liquid chamber L and the compression chamber R2, and a shutter 20 that slides in contact with the inside of the cylinder 1 and is movable in the axial direction relative to the cylinder 1, and when it comes into contact with the piston 3 it closes at least a part of the open end of the port 3b.

[0062] With the shock absorber D configured in this embodiment, when the piston 3 and shutter 20 come into contact after the piston 3 has not contacted the shutter 20 during the retraction operation, the damping force generated by the shock absorber D increases, and the force hindering the retraction operation of the shock absorber D becomes larger. Therefore, with the shock absorber D in this embodiment, the compression damping force is increased when the shock absorber D is retracted to near the compression stroke end, so the retraction operation of the shock absorber D can be sufficiently suppressed, and the damping force during the retraction 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.

[0063] Furthermore, the shutter 20 in the buffer D of this embodiment is configured to close the entire opening end of the port 3c when it comes into contact with the piston 3. With the buffer D configured in this way, the shutter 20 completely closes the port 3c, thereby cutting off communication between the extension chamber R1 and the compression chamber R2, maximizing the effective pressure-receiving area that receives pressure from the compression chamber R2, and increasing the elastic force of the air chamber G, thereby efficiently and very greatly increasing the force that suppresses the contraction operation and suppressing the contraction operation.

[0064] Furthermore, in the shock absorber D of this embodiment, the shutter 20 is annular, and an insertion member 5 is provided which is attached to the outer circumference of the tip of the piston rod 2 and, when inserted into the inner circumference of the shutter 20, forms a restricting passage 50 between the insertion member 5 and the shutter 20. With the shock absorber D of this embodiment configured in this way, the insertion member 5 is inserted into the shutter 20 to form a restricting passage 50, and the compression damping force is increased during the time until the shutter 20 closes the port 3b and the compression damping force becomes significantly higher, thereby mitigating sudden changes in compression damping force and improving ride comfort in the vehicle.

[0065] Furthermore, in the buffer D of this embodiment, the shutter 20 includes an annular guide portion 20a that slides against the inner circumference of the cylinder 1, a cylindrical portion 20b that rises from the inner circumference side of the guide portion 20a toward the piston side, an annular shutter portion 20c provided at the piston-side end of the cylindrical portion 20b that closes the port 3b when it comes into contact with the piston 3, and a hole 20d that penetrates the cylindrical portion 20b and communicates the inside and outside of the cylindrical portion 20b.

[0066] With the buffer D configured in this way, since the shutter 20 has a hole 20d that connects the inside and outside of the shutter 20, even when the shutter 20 moves toward the compression stroke end side together with the piston 3 while the port 3b of the piston 3 is closed, the pressure difference between the inside and outside of the shutter 20 becomes small. This suppresses large stresses acting on the shutter 20, suppresses deterioration of the shutter 20, and also improves the design flexibility of the shutter 20 and reduces manufacturing costs.

[0067] Furthermore, the buffer D of this embodiment is stacked on the extension chamber side of the piston 3 and includes a valve 40 that provides resistance to the flow of hydraulic fluid (liquid) from the extension chamber R1 to the compression chamber R2 through port 3b, while allowing the flow of hydraulic fluid (liquid) from the compression chamber R2 to the extension chamber R1 through port 3b.

[0068] With the shock absorber D configured in this way, the valve 40 functions as both an extension-side damping valve during extension operation and a check valve during contraction operation. Therefore, there is no need to place the extension-side damping valve on the side of the compression chamber that contacts the piston 3 for the shutter 20 to close port 3b, making it easier for the shutter 20 to close port 3b. It is also possible to provide an extension-side port on the piston 3, and provide an extension-side damping valve on the compression chamber side of the piston 3 to open and close the extension-side port, while also providing port 3b on the outer circumference of the extension-side damping valve that is not closed by the extension-side damping valve. In this configuration, the shutter 20 can close port 3b while avoiding the extension-side damping valve. However, adopting such a structure would increase the diameter of the piston 3, cylinder 1, and shutter 20, resulting in a larger shock absorber D and higher manufacturing costs. Therefore, with the shock absorber D of this embodiment, in which the valve 40 is concentrated on the extension chamber side of the piston 3 and no valves are stacked on the compression chamber side of the piston 3, the shock absorber D can be made smaller, reducing manufacturing costs and improving ease of mounting on vehicles.

[0069] Furthermore, the buffer D of this embodiment includes a stopper ring (stopper) 21 provided on the cylinder 1 to restrict the movement of the shutter 20 toward the extension chamber side, and a coil spring (spring member) 22 that biases the shutter 20 toward the extension chamber side. The liquid filling the cylinder 1 and the liquid chamber L is hydraulic fluid. The volume change amount B is defined as the product of the movement distance H from the position where the piston 3 contacts the shutter 20, which is initially positioned to contact the stopper ring (stopper) 21, until it reaches the limit of movement toward the compression chamber side, and the difference in cross-sectional area obtained by subtracting the cross-sectional area of ​​the piston rod 2 from the cross-sectional area of ​​the piston 3. If the volume inside the extension chamber R1 when the piston 3 is just contacting the shutter 20 in the initial position is defined as the volume inside the extension chamber A, then the volume change amount B is set to be one-tenth or less of the volume inside the extension chamber A.

[0070] With the buffer D configured in this way, even if the volume of the extension chamber R1 increases after the port 3b of the piston 3 is closed by the shutter 20, it is possible to prevent the gas contained in the hydraulic fluid from precipitation as bubbles in the expanded extension chamber R1, thereby preventing cavitation. As a result, even when the buffer D is contracted to near its most contracted state, it can exhibit stable extension operation when it begins to extend.

[0071] Furthermore, the buffer D may be equipped with a valve element V that provides resistance to the flow of hydraulic fluid (liquid) passing through the compensation passage 10d from the pressure chamber R2 to the liquid chamber L. Since the buffer D configured in this way is equipped with a valve element V, it can generate a pressure-side damping force that hinders the contraction operation during contraction operation. Moreover, when the piston 3 and the shutter 20 come into contact, the pressure-receiving area of ​​the shutter 20 and the piston 3 that receives the pressure from the pressure chamber R2 becomes approximately equal to the area of ​​a circle with the inner diameter of the cylinder 1 as its diameter. This maximizes the effective pressure-receiving area that receives the pressure from the pressure chamber R2, and efficiently increases the pressure-side damping force.

[0072] Therefore, in the shock absorber D of this embodiment, when the piston 3 is displaced to near the end of the compression stroke during the contraction stroke, it comes into contact with the shutter 20, increasing the pressure in the compression chamber R2 while decreasing the pressure in the extension chamber R1, thereby significantly increasing the compression damping force and suppressing the contraction operation.

[0073] Furthermore, the buffer D may be configured such that, without a valve element V in the compensation passage 10d, when the piston 3 moves in the direction of compressing the pressure chamber R2 by contacting the shutter 20, or when it moves in the contraction direction, the compensation passage 10d itself provides resistance to the flow of liquid from the pressure chamber R2 to the liquid chamber L. With the buffer D configured in this way, when the buffer D contracts while the piston 3 is in contact with the shutter 20, and the piston 3 moves in the direction of compressing the pressure chamber R2, the flow rate of hydraulic fluid moving from the pressure chamber R2 through the compensation passage 10d to the liquid chamber L increases, and the compensation passage 10d itself provides resistance to this flow of hydraulic fluid. As a result, the pressure in the pressure chamber R2 increases, and the pressure in the air chamber G also increases, generating a pressure-side damping force that hinders the contraction operation near the stroke end on the contraction side, even without a valve element V in the compensation passage 10d, thereby suppressing the contraction operation. Furthermore, in the buffer D configured in this way, the flow rate of liquid passing through the compensation passage 10d is small until the piston 3 contacts the shutter 20, so the resistance that the compensation passage 10d itself exerts on the liquid flow is very small. Therefore, when the buffer D exhibits a contraction operation within the range where the piston 3 does not contact the shutter 20, it does not generate a damping force that hinders the contraction operation, and only generates a reaction force due to the increase in pressure inside the air chamber G as the piston rod 2 enters the cylinder 1. Thus, with the buffer D configured in this way, a spring reaction force can be generated when the piston 3 contracts within the range where it does not contact the shutter 20, and a damping force can be generated to suppress the contraction operation when the piston 3 contacts the shutter 20 and contracts.

[0074] 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.

[0075] 1...Cylinder, 2...Piston rod, 3...Piston, 3b...Port, 5...Insertion member, 10d...Compensation passage, 20...Shutter, 20a...Guide part, 20b...Cylinder part, 20c...Shutter part, 20d...Hole, 21...Stopper ring (stopper), 40...Valve, 50...Limiting passage, D...Buffer, G...Air chamber, L...Liquid chamber, R1...Expansion side chamber, R2...Compression side chamber, T...Tank, V...Valve element

Claims

1. A buffer comprising: 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, having a port that divides the inside of the cylinder into an extension chamber and a compression chamber and connects the extension chamber and the compression chamber; a tank having a liquid chamber filled with liquid and a gas chamber filled with gas; a compensating passage connecting the liquid chamber and the compression chamber; and a shutter that slides in contact with the inside of the cylinder and is movable in the axial direction relative to the cylinder, and that closes at least a part of the opening end of the port when it comes into contact with the piston.

2. The buffer according to claim 1, characterized in that the shutter closes the entire opening end of the port when it comes into contact with the piston.

3. The buffer according to claim 1, characterized in that the shutter is annular, and it comprises an insertion member that is attached to the outer circumference of the tip of the piston rod and, when inserted into the inner circumference of the shutter, forms a restricting flow path between itself and the shutter.

4. The buffer according to claim 1, characterized in that the shutter has an annular guide portion that slides against the inner circumference of the cylinder, a cylindrical portion that rises from the inner circumference side of the guide portion toward the piston side, an annular shutter portion provided at the piston-side end of the cylindrical portion that closes the port when it comes into contact with the piston, and a hole that penetrates the cylindrical portion and communicates the inside and outside of the cylindrical portion.

5. The buffer according to claim 1, further comprising a valve stacked on the extension chamber side of the piston, which resists the flow of liquid from the extension chamber to the compression chamber and allows the flow of liquid from the compression chamber to the extension chamber.

6. The buffer according to claim 1, further comprising a valve element that provides resistance to the flow of liquid passing through the compensation passage from the pressure chamber to the liquid chamber.

7. The buffer according to claim 1, characterized in that when the piston moves in a direction that compresses the pressure chamber while in contact with the shutter, the compensation passage itself provides resistance to the flow of liquid from the pressure chamber to the liquid chamber.

8. The shock absorber according to claim 2, comprising: a stopper provided in the cylinder for restricting the movement of the shutter toward the extension chamber side; and a spring member for biasing the shutter toward the extension chamber side, wherein the liquid filling the cylinder and the liquid chamber is hydraulic fluid, and the volume change is defined as the product of the distance traveled from the position where the piston contacts the shutter, which is positioned in an initial position to contact the stopper, until the piston reaches its limit of movement toward the compression chamber side, and the difference in cross-sectional area obtained by subtracting the cross-sectional area of ​​the piston rod from the cross-sectional area of ​​the piston, and the volume of the extension chamber when the piston is in the initial position to contact the shutter, which is defined as the volume of the extension chamber, wherein the volume change is set to be one-tenth or less of the volume of the extension chamber.

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