Shock absorber

Abstract

This shock absorber (D) comprises: a cylinder (1); a piston rod (2); a piston (3) which partitions the inside of the cylinder (1) into an extension-side chamber (R1) and a compression-side chamber (R2); a tank (T); a free piston (40) or an elastic partition wall which partitions the inside of the tank (T) into a liquid chamber (R3) and an air chamber (G); a valve case (20) which separates the compression-side chamber (R2) and the liquid chamber (R3); an inner cylinder (10) which is accommodated in the compression-side chamber (R2); a fixed member (11) which is fixed to the cylinder (1), is supported by the valve case (20), and holds the inner cylinder (10); a locking piece (12) that penetrates into either the inside or the outside of the inner cylinder (10) and forms a hydraulic locking chamber (L); a damping passage (DP) that connects the extension-side chamber (R1) and the compression-side chamber (R2); a compression-side damping valve (21) that opens and closes a discharge port (20c) that connects the compression-side chamber (R2) and the liquid chamber (R3); and an extension-side check valve (22) that opens and closes a suction port (20d) that connects the compression-side chamber (R2) and the liquid chamber (R3).

Description

Shock absorber

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

[0002] For example, a shock absorber includes a cylinder, a piston rod movably inserted into the cylinder, a piston connected to the piston rod, movably inserted into the cylinder, and dividing the interior of the cylinder into an extension-side chamber and a compression-side chamber filled with hydraulic oil, and further includes a piston rod movably inserted into the cylinder and connected to the piston, and is used by being interposed between the vehicle body and a rear wheel of a vehicle.

[0003] In a conventional shock absorber, a damping force is generated when the shock absorber expands and contracts as the vehicle travels, so that vibration of the vehicle body can be suppressed. However, when the vehicle is forced to travel on a rough road such as a cobblestone road with severe irregularities or in an area where road maintenance is underdeveloped, when the shock absorber contracts to the vicinity of the stroke end, there are cases where a large compression-side damping force is required for the shock absorber.

[0004] In order to meet such demands, a hydraulic lock mechanism that hinders the contraction operation when vibration input that causes the shock absorber to contract to the maximum position is sometimes provided. A shock absorber provided with a hydraulic lock mechanism, for example, as disclosed in JP2023-505692A, includes an inner cylinder housed in the compression-side chamber within the cylinder, an annular fixing member that is press-fitted and fixed to the inner circumference of the lower end of the cylinder and holds the outer circumference of the inner cylinder, and a slotted cylindrical lock piece with a C-shaped cross-section that is connected to the piston, forms a hydraulic lock chamber between the inner cylinder and the cylinder when fitted onto the outer circumference of the inner cylinder, and further includes a bottomed cylindrical outer cylinder that forms a reservoir between itself and the cylinder on the outer circumference of the cylinder.

[0005] When this shock absorber contracts and the lock piece engages with the outer circumference of the inner cylinder, the lock piece receives pressure from the hydraulic lock chamber from the outer circumference side, closing the split portion and restricting the movement of hydraulic fluid from the hydraulic lock chamber into the chamber inside the inner cylinder. This increases the pressure inside the hydraulic lock chamber, thereby generating a large force that hinders the contraction operation and exhibiting a hydraulic lock function. Furthermore, the fixing member is supported by a valve case sandwiched between the cylinder and the bottom of the outer cylinder, and even when high pressure acts on it in the hydraulic lock chamber, it is supported by the valve case and can support the inner cylinder without shifting in the axial direction.

[0006] JP2023-505692A

[0007] Conventional shock absorbers are configured as so-called twin-cylinder shock absorbers, with an outer cylinder surrounding the outer circumference of the cylinder. The valve case, fixed by the cylinder and outer cylinder, supports the fixing member, allowing for stable hydraulic locking. However, the twin-cylinder configuration makes it difficult to reduce the outer diameter, and improved vehicle mounting is desired.

[0008] However, in a monotube type shock absorber, which does not have an outer cylinder on the outer circumference of the cylinder, the structure is such that a free piston inserted into the cylinder so as to be movable in the axial direction forms an air chamber inside the cylinder. This necessitates the installation of a fixed member in the middle of the cylinder, which often results in insufficient support for the fixed member and makes it difficult to install the inner cylinder. Furthermore, the upper limit of the damping force during contraction depends on the pressure inside the air chamber, and there is a problem that the damping force tends to be insufficient when expanding and contracting at high speeds.

[0009] Therefore, the present invention aims to provide a shock absorber that can stably support the inner cylinder, exhibit a good hydraulic locking function, and exert a high damping force during contraction.

[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 to divide the inside of the cylinder into an extension chamber and a compression chamber, a cylindrical tank, a free piston or elastic partition housed in the tank to divide the inside of the tank into a liquid chamber and an air chamber, a valve case fixed inside the cylinder to separate the compression chamber and the liquid chamber, an inner cylinder housed inside the cylinder and within the compression chamber, a fixing member fixed to the inner circumference of the cylinder to hold the inner cylinder and supported in the axial direction by the valve case, and The device comprises a lock piece connected to a stone rod and capable of penetrating either the inside or outside of the inner cylinder, and which, upon penetrating either the inside or outside of the inner cylinder, forms a hydraulic lock chamber on that side; a damping passage provided on the piston that connects the extension chamber and the compression chamber; a discharge port and a suction port provided on the valve case that connect the compression chamber and the liquid chamber; a compression damping valve that opens and closes the discharge port and resists the flow of liquid from the compression chamber to the liquid chamber; and an extension check valve that opens and closes the suction port and allows only the flow of liquid from the liquid chamber to the compression chamber.

[0011] With this type of buffer, the fixed member is supported by a valve case fixed to the cylinder, so even when the hydraulic lock chamber becomes high pressure, the fixed member does not shift axially relative to the cylinder, and the inner cylinder can be stably supported. In addition, since a pressure-side damping valve is provided that opens and closes the discharge port in the valve case that separates the pressure-side chamber and the liquid chamber, a high damping force can be generated regardless of the pressure setting of the air chamber, thereby preventing the contraction operation.

[0012] Figure 1 is a cross-sectional view of a buffer in one embodiment. Figure 2 is an enlarged cross-sectional view of a part of the buffer in one embodiment. Figure 3 is a cross-sectional view of the buffer in one embodiment in a contracted state. Figure 4 is an enlarged cross-sectional view of the valve case portion in a first modified example of the buffer in one embodiment. Figure 5 is an enlarged cross-sectional view of the valve case portion in a second modified example of the buffer in one embodiment.

[0013] The present invention will be described based on the embodiments shown in the figures. As shown in Figures 1 and 2, 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 piston 3 connected to the piston rod 2 and inserted into the cylinder 1 to divide the inside of the cylinder 1 into an extension chamber R1 and a compression chamber R2, a cylindrical tank T, a free piston 40 housed in the tank T to divide the inside of the tank T into a liquid chamber R3 and an air chamber G, a valve case 20 fixed inside the cylinder 1 to separate the compression chamber R2 and the liquid chamber R3, an inner cylinder 10 housed inside the cylinder 1 and in the compression chamber R2, and a fixing member fixed to the inner circumference of the cylinder 1 to hold the inner cylinder 10 and supported in the axial direction by the valve case 20. The device is configured to include: 11; a lock piece 12 connected to the piston rod 2 and capable of penetrating to the outside of the inner cylinder 10, and which, upon penetrating to the outside of the inner cylinder 10, forms a hydraulic lock chamber L on the outside of the inner cylinder 10; a damping passage DP provided on the piston 3 that connects the extension chamber R1 and the compression chamber R2; a discharge port 20c and a suction port 20d provided on the valve case 20 that connect the compression chamber R2 and the liquid chamber R3; a compression damping valve 21 that opens and closes the discharge port 20c and resists the flow of liquid from the compression chamber R2 to the liquid chamber R3; and an extension check valve 22 that opens and closes the suction port 20d and allows only the flow of liquid from the liquid chamber R3 to the compression chamber R2.

[0014] Although not shown in the diagram, shock absorber D is, for example, installed between the vehicle body and the wheels in a vehicle to generate damping force during expansion and contraction, thereby suppressing vibrations of the vehicle body. Note that shock absorber D may be used in vehicles other than automobiles, such as saddle-type vehicles, or in equipment other than vehicles, buildings, etc.

[0015] The following describes the various parts of the buffer D. The cylinder 1 is cylindrical and has a piston 3 inserted inside so as to be movable in the axial direction. Below the piston 3 inside the cylinder 1, a fixing member 11 and a valve case 20 are fixed in order from top to bottom in Figure 1, and below the valve case 20 of the cylinder 1 a bottomed cylindrical tank T is connected. In this embodiment, the tank T is integrated with the lower side of the cylinder 1, and the cylinder 1 and the cylindrical tank T are formed by a single cylinder and are inseparable from each other. A free piston 40 is inserted inside the tank T so as to be movable in the axial direction, and the inside of the tank T is divided by the free piston 40 into a liquid chamber R3 filled with liquid and a gas chamber G filled with gas. By moving the free piston 40 in the axial direction inside the tank T, the free piston 40 can expand one of the liquid chamber R3 and the gas chamber G and contract the other. In this embodiment, the inside of the tank T is divided into a liquid chamber R3 and an air chamber G by a free piston 40. However, instead of the free piston 40, an elastic partition such as a diaphragm or a metal bellows may be used to form the liquid chamber R3 and the air chamber G inside the tank T. Furthermore, the tank T may be formed by a cylinder different from the cylinder 1 and connected to the lower end of the cylinder 1, or it may be formed by a cylinder spaced apart from the cylinder 1, with piping connecting the inside of the cylinder 1 and the liquid chamber R3 inside the tank T.

[0016] The inside of cylinder 1 is divided by piston 3 into an extension chamber R1 above piston 3 in Figure 1 and a compression chamber R2 below piston 3 in Figure 1. The valve case 20, when fixed inside cylinder 1, separates the compression chamber R2 and the fluid chamber R3.

[0017] Thus, the buffer D in this embodiment is configured as a monotube, so-called single-cylinder type buffer. Furthermore, the extension chamber R1, compression chamber R2, and liquid chamber R3 within the cylinder 1 are filled with a liquid such as hydraulic oil, and the gas chamber G is filled with gas. In addition to hydraulic oil, water, aqueous solution, etc. may be used as the liquid. When a liquid is used as hydraulic oil, the gas filled in the gas chamber G should preferably be an inert gas such as nitrogen to prevent deterioration of the hydraulic oil.

[0018] A rod guide 30 is fitted to the upper end of cylinder 1 in Figure 1, which slidably supports the piston rod 2. This rod guide 30 is fitted to the inner circumference of the upper end of cylinder 1 and fixed to cylinder 1 by crimping the upper end of cylinder 1 together with a sealing member 31 that seals the space between cylinder 1 and piston rod 2.

[0019] 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.

[0020] Furthermore, a bracket (not shown) is provided at the base end of the piston rod 2, which is the upper end in Figure 1, and the piston rod 2 is connected to one of the vehicle body and the wheel of a vehicle (not shown) via the aforementioned bracket (not shown). Also, a bracket (not shown) is provided at the bottom of the tank T connected to the lower end of the cylinder 1, and the cylinder 1 is connected to the other of the vehicle body and the wheel via the aforementioned bracket (not shown).

[0021] In this embodiment, the shock absorber D is interposed between the vehicle body and the wheel, with the piston rod 2 connected to the vehicle body and the cylinder 1 connected to 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.

[0022] 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 7 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 1, an extension port 3c that penetrates the piston body 3a in the axial direction, and a compression port 3d that penetrates the piston body 3a in the axial direction.

[0023] 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, which slides 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 in the axial direction, connecting the extension chamber R1 and the compression chamber R2.

[0024] Next, a compression damping valve 5, which opens and closes the outlet end of the compression port 3c, is stacked on the lower part of the piston body 3a of the piston 3 in Figure 1. The compression damping valve 5 is a laminated leaf valve composed of multiple annular plates stacked together, and after being mounted on the outer circumference of the piston fitting portion 2a together with the piston 3, it is fixed to the piston rod 2 by a piston nut 7. The compression damping valve 5 has its inner circumference fixed to the piston rod 2 and is allowed to flex on its outer circumference. When the outer circumference is in contact with the piston body 3a, it closes the compression port 3c, and when the outer circumference is flexed and separated from the piston body 3a, it opens the compression port 3c while providing resistance to the flow of liquid passing through the compression port 3c from the compression chamber R1 to the compression chamber R2. The outer diameter of the compression damping valve 5 is set such that even when the compression damping valve 5 is stacked 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 compression port 3c, is not blocked.

[0025] On the other hand, a pressure-side check valve 6, which opens and closes the outlet end of the pressure-side port 3d, is stacked on the upper part of the piston body 3a in Figure 1. The pressure-side check valve 6 is constructed by stacking multiple annular plates and 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 piston nut 7. The inner circumference of the pressure-side check valve 6 is fixed to the piston rod 2 and the outer circumference is allowed to bend. When the outer circumference is in contact with the piston body 3a, it closes the pressure-side port 3d, and when the outer circumference is bent and separated from the piston body 3a, it opens the pressure-side port 3d. The pressure-side check valve 6 allows liquid to pass through the pressure-side port 3d from the pressure-side chamber R2 to the extension-side chamber R1 with almost no resistance, but conversely, when liquid attempts to pass through the pressure-side port 3d from the extension-side chamber R1 to the pressure-side chamber R2, it closes the valve and prevents the passage of the liquid. Furthermore, the inlet end of the extension port 3c is connected to the outer circumference of the piston body 3a, and care has been taken to ensure that the extension port 3c is not blocked by the compression check valve 6 even if the compression check valve 6 is stacked on the upper end of the piston body 3a in Figure 1.

[0026] As described above, the damping passage DP provided in the piston 3 is composed of an extension port 3c and an extension damping valve 5. In this embodiment, the shock absorber D generates an extension damping force by applying resistance only to the flow of liquid from the extension chamber R1 to the compression chamber R2 when the shock absorber D is extended. Alternatively, instead of the compression check valve 6, a damping valve that applies resistance when liquid passes through the compression port 3d may be provided, and the damping passage DP may be composed of the extension port 3c and extension damping valve 5, and the compression port 3d and damping valve, thereby applying resistance to the flow of liquid moving between the extension chamber R1 and the compression chamber R2. Alternatively, a throttling passage that allows bidirectional flow of liquid may be provided in the piston 3 as the damping passage DP.

[0027] As shown in Figure 2, the valve case 20 has an annular case body 20a with a threaded portion 20b on its outer circumference that is screw-connected to a threaded portion 1a provided on the inner circumference of the cylinder 1, and a discharge port 20c and an intake port 20d that pass through the case body 20a and connect the pressure chamber R2 and the liquid chamber R3. The valve case 20 is fixed to the threaded portion 1a provided on the inner circumference of the cylinder 1 and divides the inside of the cylinder 1 into a pressure chamber R2 and a liquid chamber R3.

[0028] A compression damping valve 21, which opens and closes the outlet end of the discharge port 20c, is stacked on the lower side of the case body 20a in Figure 2. The compression damping valve 21 is a laminated leaf valve composed of multiple annular plates stacked together, and is mounted on the outer circumference of a center rod 23, which is inserted through the inner circumference of the case body 20a together with the valve case 20. The center rod 23 is axial in shape and has a flange 23a at its base end and a threaded portion 23b at its tip to which a nut 24 is screwed. The valve case 20 and the compression damping valve 21 are sandwiched between the flange 23a and the nut 24 and fixed to the center rod 23. The compression damping valve 21 has its inner circumference fixed to the center rod 23 and is allowed to flex on its outer circumference. When the outer circumference is in contact with the case body 20a, it closes the discharge port 20c. When the outer circumference is flexed and separated from the case body 20a, it opens the discharge port 20c while resisting the flow of liquid passing through the discharge port 20c from the pressure chamber R2 to the liquid chamber R3. The outer diameter of the compression damping valve 21 is set such that even when the compression damping valve 21 is stacked on the lower end of the case body 20a, it does not block the inlet end of the suction port 20d, which is located on the outer circumference of the discharge port 20c.

[0029] On the other hand, an extension check valve 22, which opens and closes the outlet end of the suction port 20d, is stacked on the upper side of the case body 20a in Figure 2. The extension check valve 22 is constructed by stacking multiple annular plates and, together with the valve case 20, is mounted on the outer circumference of the center rod 23, and then fixed to the center rod 23 by a nut 24 and a flange 23a. The extension check valve 22 has its inner circumference fixed to the center rod 23 and is allowed to bend on its outer circumference. When the outer circumference is in contact with the case body 20a, it closes the suction port 20d, and when the outer circumference is bent and separated from the case body 20a, it opens the suction port 20d. The extension check valve 22 allows liquid to pass through the suction port 20d from the liquid chamber R3 to the pressure chamber R2 with almost no resistance, but conversely, if liquid attempts to pass through the suction port 20d from the pressure chamber R2 to the liquid chamber R3, it closes to prevent the passage of that liquid. The extension check valve 22 is equipped with a hole 22a that penetrates axially, and even when stacked on the upper end of the case body 20a in Figure 2, it does not block the inlet end of the discharge port 20c, allowing liquid to pass through the discharge port 20c.

[0030] Furthermore, a relief valve 25 is fixed to the outer circumference of the center rod 23, on the side of the extension check valve 22 that is closer to the nut 24, and includes a valve retaining member 26 and an annular relief valve body 27 that is stacked on the valve retaining member 26.

[0031] The valve retaining member 26 is annular in shape and has a plurality of through holes 26a provided at equal intervals in the circumferential direction. The relief valve body 27 is annular in shape and has a C-shaped through hole 27a that communicates with the through holes 26a, and its outer diameter is set to be sufficiently larger than the outer diameter of the valve retaining member 26.

[0032] The fixing member 11 comprises an annular fixing member body 11a, an annular skirt 11b extending downward from the outer circumference of the lower end of the fixing member body 11a, a plurality of relief ports 11c that penetrate the fixing member body 11a, and a holding portion 11d formed by increasing the inner diameter on the upper side of the inner circumference of the fixing member body 11a in Figure 2, into which the lower end of the inner cylinder 10 in Figure 2 is press-fitted. The fixing member 11 is fixed to the cylinder 1 by press-fitting the outer circumference of the annular fixing member body 11a onto the inner surface of the cylinder 1.

[0033] Furthermore, the lower outer circumference of the fixing member body 11a of the fixing member 11 abuts against the upper outer circumference of the valve case 20 in Figure 2, and the fixing member 11 is supported from the lower side in Figure 2 by the valve case 20, thereby restricting its downward movement relative to the cylinder 1 in Figure 2. The relief port 11c opens from the upper end of the fixing member body 11a in Figure 2 and leads to the lower end of the fixing member body 11a, which is on the inner circumference side of the skirt 11b.

[0034] The lower outer circumference of the inner cylinder 10 is inserted into the retaining portion 11d formed on the inner circumference side of the fixed member 11 configured in this way. The outer diameter of the lower end of the inner cylinder 10 is larger than the inner diameter of the retaining portion 11d of the fixed member 11, and the inner cylinder 10 inserted into the retaining portion 11d is press-fitted into the inner circumference of the fixed member 11 and firmly fixed in place.

[0035] Thus, the inner cylinder 10 is housed within the cylinder 1 and in the pressure chamber R2, and is fixed to the cylinder 1 by the fixing member 11. The outer diameter of the inner cylinder 10 is smaller than the inner diameter of the cylinder 1, and an annular gap is formed between the outer circumference of the inner cylinder 10 and the inner circumference of the cylinder 1. When the lock piece 12 enters this annular gap, the lock piece 12 forms a hydraulic lock chamber L between the inner cylinder 10 and the cylinder 1. The annular gap between the inner cylinder 10 and the cylinder 1 is axially opposite to the relief port 11c, and is connected to the space between the fixing member 11 and the valve case 20 via the relief port 11c, and further connected to the liquid chamber R3 in the tank T via the discharge port 20c and the suction port 20d. In addition, the space within the pressure chamber R2 on the inner circumference side of the inner cylinder 10 is connected to the liquid chamber R3 in the tank T via the inner circumference of the fixing member 11 and the discharge port 20c and suction port 20d of the valve case 20.

[0036] Furthermore, when the fixing member 11 is fixed to the inner circumference of the cylinder 1, and the lower end of the skirt 11b of the fixing member 11 comes into contact with the outer circumference of the case body 20a of the valve case 20, the middle portion of the relief valve body 27 is sandwiched between the upper outer circumference of the valve retaining member 26 and the inner circumference of the lower end of the fixing member body 11a, and the outer circumference of the relief valve body 27 comes into contact with the outer circumference of the lower surface of the fixing member body 11a, thereby closing the outlet end of the lower end of the relief port 11c by the relief valve body 27.

[0037] Furthermore, the inner diameter and height of the skirt 11b are set so that the skirt 11b does not interfere with the relief valve body 27 and the extension check valve 22, and care is taken to ensure that the skirt 11b does not obstruct the operation of the relief valve body 27 and the extension check valve 22.

[0038] The relief valve body 27 is allowed to deflect downward in the outer circumference as shown in Figure 2, with the intermediate portion, which is sandwiched between the valve retaining member 26 and the inner circumference of the lower end of the fixing member body 11a, acting as a fulcrum. When it is in contact with the outer circumference of the lower end of the fixing member body 11a, it is given an initial deflection and is pressed against the fixing member body 11a by the elastic force it exerts. The opening pressure when the relief valve 25 opens the relief port 11c is set by the amount of initial deflection given to the relief valve body 27.

[0039] When the pressure of the liquid attempting to pass through the relief port 11c from the pressure side chamber R2 to the liquid side reaches or exceeds the opening pressure, the outer circumference of the relief valve body 27 flexes with the intermediate portion as a fulcrum, opening the valve and allowing the liquid to pass through the relief port 11c from the pressure side chamber R2 to the liquid side. The opening pressure of the relief valve 25 can be set not only by the initial amount of flexure applied to the relief valve body 27 as described above, but also by the flexural rigidity of the relief valve body 27.

[0040] Next, the lock piece 12 is a cylindrical C-shaped cross-section with elasticity, connected to the piston rod 2 via the piston 3 and fitted onto the outer circumference of the inner cylinder 10. More specifically, the lock piece 12 is a cylindrical C-shaped cross-section made of synthetic resin, and has a slit 12a along the axial direction at one location in the circumferential direction, and a number of semicircular grooves 12b formed at both ends in the circumferential direction, facing each other in the circumferential direction and arranged in the axial direction. The lock piece 12 also has three annular reinforcing ribs 12c provided along the circumferential direction on the outer circumference and projecting outward, an annular guide rib 12d on the outer circumference that project outward from near the lower end in Figure 1 below the reinforcing ribs 12c and slides against the inner circumferential surface of the cylinder 1, and an annular fitting rib 12e provided along the circumferential direction at the upper end in Figure 1 on the inner circumference and projecting inward.

[0041] The thus-configured lock piece 12 is connected to the piston 3 by fitting a fitting rib 12e into an annular groove 3f provided on the outer periphery of the lower end, in FIG. 1, of the cylindrical portion 3b of the piston 3. In this way, the lock piece 12 is connected to the piston rod 2 via the piston 3, and by bringing the guide rib 12d into sliding contact with the inner peripheral surface of the cylinder 1, the lock piece 12 can move together with the piston rod 2 and the piston 3 in the axial direction relative to the cylinder 1 without axial runout.

[0042] Further, the inner diameter of the lock piece 12 is slightly larger than the outer diameter of the inner cylinder 10, and the lock piece 12 allows insertion of the inner cylinder 10 thereinto when the piston rod 2 moves downward in FIG. 1.

[0043] Furthermore, when the lock piece 12 receives pressure from the outer peripheral side and reduces its diameter, the split 12a is closed, and a circular orifice is formed by the grooves 12b, 12b opposed in the circumferential direction. Since a plurality of the grooves 12b are provided axially side by side at both circumferential ends of the lock piece 12, when the split 12a is closed, a plurality of orifices arranged axially side by side are formed in the lock piece 12. The inner diameter of the orifice formed by the grooves 12b, 12b opposed in the circumferential direction is set to become smaller as going from the lower side to the upper side of the lock piece 12 in FIG. 1. That is, the diameter of the semicircular groove 12b becomes smaller as going toward the upper side of the lock piece 12.

[0044] When the shock absorber D performs a contraction operation and the piston rod 2 moves downward in FIG. 1 relative to the cylinder 1, and as shown in FIG. 3, the lock piece 12 comes to fit onto the outer periphery of the inner cylinder 10 and the inner cylinder 10 enters the inside of the lock piece 12, the lock piece 12 forms a hydraulic lock chamber L in the annular gap between the inner cylinder 10 and the cylinder 1.

[0045] The relief port 11c, which connects the hydraulic lock chamber L to the liquid chamber R3, is closed by the relief valve 25 until the pressure in the hydraulic lock chamber L reaches the opening pressure of the relief valve 25. As a result, as the shock absorber D contracts, the volume of the hydraulic lock chamber L decreases and the pressure in the hydraulic lock chamber L increases due to the intrusion of the lock piece 12 into the annular gap. Then, the pressure in the hydraulic lock chamber L acts on the lock piece 12 from the outer circumference, causing the lock piece 12 to shrink in diameter, close the split 12a, and fit onto the outer circumference of the inner cylinder 10. Therefore, the liquid that has intruded into the annular gap of the lock piece 12 passes through the orifice formed by the grooves 12b, 12b of the lock piece 12, which has shrunk in diameter and closed the split 12a, and moves into the inner cylinder 10. As the lock piece 12 moves downward in Figure 3, the orifices formed by grooves 12b, 12b are sequentially closed on the outer circumference of the inner cylinder 10 from the lower side. As a result, the effective area of ​​the orifice connecting the hydraulic lock chamber L and the inside of the inner cylinder 10 decreases, the pressure inside the hydraulic lock chamber L becomes high, and the downward movement of the lock piece 12 relative to the inner cylinder 10 is prevented. In this way, when the lock piece 12 enters the annular gap between the inner cylinder 10 and the cylinder 1, the hydraulic lock mechanism composed of the lock piece 12 and the inner cylinder 10 exerts a force that prevents the shock absorber D from contracting.

[0046] Furthermore, when the pressure in the hydraulic lock chamber L reaches the opening pressure of the relief valve 25, the relief valve 25 opens, allowing the liquid in the hydraulic lock chamber L to move to the liquid chamber R3 through the relief port 11c and the discharge port 20c. This prevents the pressure in the hydraulic lock chamber L from becoming excessive, which would create an excessive force that hinders the contraction operation of the buffer D generated by the hydraulic lock mechanism.

[0047] When the shock absorber D is extended from the state where the lock piece 12 has entered the annular gap between the inner cylinder 10 and the cylinder 1, the volume in the hydraulic lock chamber L expands, so the pressure inside the hydraulic lock chamber L is reduced, the diameter of the lock piece 12 expands, the split 12a opens, and the inside of the inner cylinder 10 communicates with the hydraulic lock chamber L via the split 12a. In this state, the liquid in the inner cylinder 10 can move through the split 12a into the hydraulic lock chamber L with almost no resistance, so the shock absorber D can perform extension operation with almost no resistance.

[0048] The shock absorber D is configured as described above, and the operation of the shock absorber D will be described below. First, when the shock absorber D performs extension operation, the piston rod 2 and the piston 3 move upward relative to the cylinder 1 in FIG. 1, the extension side chamber R1 is reduced and the compression side chamber R2 is expanded. The liquid in the reduced extension side chamber R1 pushes open the extension side damping valve 5, passes through the extension side port 3c, and moves to the expanded compression side chamber R2. The extension side damping valve 5 provides resistance to the flow of liquid passing through the extension side port 3c, so the pressure in the extension side chamber R1 rises and acts on the piston 3, and the shock absorber D generates a damping force that hinders the extension operation. It should be noted that during the extension operation of the shock absorber D, the piston rod 2 withdraws from the cylinder 1, resulting in a shortage of liquid corresponding to the volume that the piston rod 2 withdrew from the cylinder 1. For this shortage of liquid, the extension side check valve 22 opens, the free piston 40 moves upward in FIG. 1 to expand the air chamber G, the liquid is supplied from the liquid chamber R3 into the cylinder 1, and compensation for the volume of the piston rod 2 withdrawing from the cylinder 1 is performed.

[0049] Furthermore, even when the lock piece 12 is inserted between the inner cylinder 10 and the cylinder 1 to partition the hydraulic lock chamber L during the extension operation of the shock absorber D, the diameter of the lock piece 12 expands as described above, and the hydraulic lock chamber L communicates with the inside of the inner cylinder 10 via the split 12a. Therefore, the hydraulic lock mechanism allows the lock piece 12 to move upward relative to the cylinder 1 in FIG. 1 without resistance.

[0050] On the other hand, when the shock absorber D contracts, the piston rod 2 and piston 3 move downward relative to the cylinder 1 in Figure 1, causing the compression chamber R2 to shrink and the extension chamber R1 to expand. The liquid in the shrinking compression chamber R2 pushes open the compression check valve 6, passes through the compression port 3d, and moves into the expanding extension chamber R1.

[0051] 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 21, passes through the discharge port 20c, and moves from the cylinder 1 to the liquid chamber R3. The liquid that has moved to the liquid chamber R3 causes the free piston 40 to move downward within the tank T, thereby reducing the size of the air chamber G.

[0052] The compression damping valve 21 resists the flow of liquid passing through the discharge port 20c, 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 retracting. Thus, when the shock absorber D retracts, the pressure inside the cylinder 1 rises due to the compression damping valve 21 and becomes higher than that of the air chamber G, so the shock absorber D can generate a high damping force regardless of the pressure setting of the air chamber G and prevent it from retracting.

[0053] Furthermore, when the shock absorber D is contracting, if the lock piece 12 enters the annular gap between the inner cylinder 10 and the cylinder 1, the pressure in the hydraulic lock chamber L increases, and the shock absorber D generates a damping force as the sum of the damping force generated by the pressure damping valve 21 and the force generated by the hydraulic lock mechanism in response to the pressure rise in the hydraulic lock chamber L, thereby hindering the contraction operation of the shock absorber D.

[0054] As the hydraulic locking mechanism exerts a force that inhibits the contraction of the buffer D, and as the buffer D continues to contract, the number of orifices in the lock piece 12 that are blocked by the inner cylinder 10 increases, the pressure in the hydraulic locking chamber L gradually rises, and the force inhibiting the contraction of the buffer D increases. When the buffer D contracts to near the end of the stroke on the contraction side, the lock piece 12 penetrates deeply into the annular gap, greatly reducing the volume of the hydraulic locking chamber L, and almost all of the orifices of the lock piece 12 are blocked. As a result, the pressure in the hydraulic locking chamber L increases rapidly, and the force that the hydraulic locking mechanism exerts to inhibit the contraction of the buffer D increases rapidly. Furthermore, as the buffer D contracts toward the end of the stroke on the contraction side, the pressure in the hydraulic locking chamber L reaches the opening pressure of the relief valve 25, and the liquid in the hydraulic locking chamber L is discharged to the liquid chamber R3 through the relief port 11c and the discharge port 20c. Therefore, the hydraulic lock mechanism exerts a large force when the buffer D contracts near the end of its stroke, preventing the buffer D from contracting. This allows the buffer D to mitigate the impact during contraction and prevents the pressure in the hydraulic lock chamber L from exceeding the opening pressure of the relief valve 25. Furthermore, even if the pressure in the hydraulic lock chamber L becomes high, the fixing member 11 is supported from below in Figure 2 by the valve case 20, so the fixing member 11 does not shift downward relative to the cylinder 1, and the buffer D can stably perform its hydraulic lock function.

[0055] When the shock absorber D configured in this way is applied to a vehicle, it is interposed between the vehicle body and the wheels together with the suspension spring. However, when the load on the vehicle increases, it compresses together with the suspension spring, so that even when the vehicle is stationary, the lock piece 12 is inserted between the inner cylinder 10 and the cylinder 1. In this situation, the shock absorber D increases the force that opposes compression during the compression operation, so that the damping force generated during the compression operation can be automatically increased in response to the load on the vehicle.

[0056] 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 to divide the inside of the cylinder 1 into an extension chamber R1 and a compression chamber R2, a cylindrical tank T, a free piston 40 housed in the tank T and dividing the inside of the tank T into a liquid chamber R3 and an air chamber G, a valve case 20 fixed inside the cylinder 1 and separating the compression chamber R2 and the liquid chamber R3, an inner cylinder 10 housed inside the cylinder 1 and in the compression chamber R2, a fixing member 11 fixed to the inner circumference of the cylinder 1 and holding the inner cylinder 10 and supported in the axial direction by the valve case 20, and a piston The system comprises a lock piece 12 connected to the ton rod 2 and capable of penetrating to the outside of the inner cylinder 10, and which forms a hydraulic lock chamber L on the outside of the inner cylinder 10 when it penetrates to the outside of the inner cylinder 10; a damping passage DP provided on the piston 3 that connects the extension chamber R1 and the compression chamber R2; a discharge port 20c and a suction port 20d provided on the valve case 20 that connect the compression chamber R2 and the liquid chamber R3; a compression damping valve 21 that opens and closes the discharge port 20c and resists the flow of liquid from the compression chamber R2 to the liquid chamber R3; and an extension check valve 22 that opens and closes the suction port 20d and allows only the flow of liquid from the liquid chamber R3 to the compression chamber R2.

[0057] With the buffer D configured in this way, the fixing member 11 is supported by the valve case 20 fixed to the cylinder 1, so even if the hydraulic lock chamber L becomes high pressure, the fixing member 11 does not shift axially relative to the cylinder 1 and can stably support the inner cylinder 10. In addition, since a pressure-side damping valve 21 is provided that opens and closes the discharge port 20c provided in the valve case 20 that separates the pressure-side chamber R2 and the liquid chamber R3, a high damping force can be generated regardless of the pressure setting of the air chamber G, thereby preventing the contraction operation.

[0058] Based on the above, the shock absorber D of this embodiment can stably support the inner cylinder 10, exhibit a good hydraulic locking function, and exert a high damping force during contraction.

[0059] Furthermore, in the shock absorber D of this embodiment, when the lock piece 12 enters the outside of the inner cylinder 10, a hydraulic lock chamber L is formed on the outside of the inner cylinder 10. In this way, since the lock piece 12 is positioned on the outer circumference of the inner cylinder 10, the inner and outer diameters of the lock piece 12 are increased, and a larger pressure-receiving area is secured in the lock piece 12 that receives the pressure in the hydraulic lock chamber L, thereby increasing the force that prevents the shock absorber D from contracting due to the hydraulic lock function. Therefore, with the shock absorber D of this embodiment, even a single-cylinder type shock absorber, which is difficult to increase the compression damping force, can efficiently exert a higher damping force during contraction. In addition, since the pressure-receiving area of ​​the lock piece 12 can be increased, the damping force due to the hydraulic lock function can be secured even if the maximum pressure in the hydraulic lock chamber L is lowered, so the load on the lock piece 12, inner cylinder 10, fixing member 11 and relief valve 25 can be reduced and durability can be improved, and the pressure resistance requirements for the lock piece 12, inner cylinder 10, fixing member 11 and relief valve 25 can be lowered and costs can be reduced.

[0060] Furthermore, in the buffer D of this embodiment, the lock piece 12 is a cylindrical shape with a C-shaped cross-section that is elastic, connected to the piston rod 2 via the piston 3 and can be fitted onto the outer circumference of the inner cylinder 10. When fitted onto the outer circumference of the inner cylinder 10, it forms a hydraulic lock chamber L between the cylinder 1 and the inner cylinder 10. The fixing member 11 has an annular fixing member body 11a and a plurality of relief ports 11c that penetrate the fixing member body 11a in the axial direction. It is equipped with a relief valve 25 that is stacked on the anti-pressure side chamber of the fixing member body 11a and opens and closes the outlet end of the relief port 11c.

[0061] With the buffer D configured in this way, a cylindrical lock piece 12 with a C-shaped cross-section is inserted between the inner cylinder 10 and the cylinder 1 to form a hydraulic lock chamber L. During contraction, the pressure in the hydraulic lock chamber L causes the lock piece 12 to shrink in diameter and fit onto the outer circumference of the inner cylinder 10, increasing the pressure in the hydraulic lock chamber L. The relief valve 25 prevents the pressure in the hydraulic lock chamber L from becoming excessive. During extension, even if the lock piece 12 is inserted between the cylinder 1 and the inner cylinder 10, the lock piece 12 expands in diameter, allowing liquid to quickly flow from the inner cylinder 10 into the hydraulic lock chamber L without hindering the extension operation. Furthermore, since the cylindrical lock piece 12 is mounted on the piston 3, when partitioning the hydraulic lock chamber L between the inner cylinder 10 and the cylinder 1, communication between the extension port 3c and compression port 3d provided on the piston 3 and the compression chamber R2 can be ensured through the inner circumference of the lock piece 12, so the lock piece 12 does not get in the way. Furthermore, when the lock piece 12 is brought into sliding contact with the inner circumference of the cylinder 1, the cylinder 1 can be used as a guide to allow the lock piece 12 to smoothly move in and out between the cylinder 1 and the inner cylinder 10, which is aligned with the cylinder 1 via a fixing member 11.

[0062] In this embodiment, the lock piece 12 penetrates the outside of the inner cylinder 10, forming a hydraulic lock chamber L on the outside of the inner cylinder 10. However, instead of the cylindrical lock piece 12 described above, a lock piece that can be inserted into the inner cylinder 10 may be installed at the tip of the piston rod 2, forming a hydraulic lock chamber that is closed inside the inner cylinder 10 when the lock piece is inserted inside the inner cylinder 10. In this case, to form a closed hydraulic lock chamber, the lower end of the inner cylinder 10 should be closed. If a relief valve is provided, the relief valve should be installed on the member that closes the lower end of the inner cylinder 10 or on the inner cylinder 10. In this case, the compression damping valve and the extension check valve should be installed on the fixing member 11.

[0063] Furthermore, in the shock absorber D of this embodiment, the cylinder 1 and the tank T are formed from a single cylinder. With the shock absorber D configured in this way, by forming the cylinder 1 and the tank T from a single cylinder, it is not necessary to form the cylinder 1 and the tank T from separate cylinders, which reduces the number of parts and lowers manufacturing costs.

[0064] As described above, the valve case 20 is fixed to the cylinder 1 by screwing it to the inner circumference of the cylinder 1. However, as shown in Figure 4, an annular groove 20e may be provided on the outer circumference of the valve case 20, and the valve case 20 may be fixed to the cylinder 1 by crimping the cylinder 1 from the outer circumference and elastically deforming it, thereby causing the formed protrusion 1b to enter the annular groove 20e. Alternatively, as shown in Figure 5, when a threaded portion 1c is formed on the outer circumference of the cylinder 1, and a threaded portion 50 formed on the inner circumference of a bottomed cylindrical tank T, which is different from the cylinder 1, is screwed to the threaded portion 1c to connect the cylinder 1 and the tank T, a stepped portion 51 may be provided inside the upper end of the tank T, and the valve case 20 may be fixed to the cylinder 1 by sandwiching it between the lower end of the cylinder 1 in Figure 5 and the stepped portion 51. Although not shown in the diagram, a stepped portion and a threaded portion may be provided on the inner circumference of the cylinder 1, and a threaded portion may be formed on the outer circumference of the bottomed cylindrical tank T, so that the valve case 20 is sandwiched between the stepped portion of the cylinder 1 and the upper end of the tank T.

[0065] 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.

[0066] 1...Cylinder, 2...Piston rod, 3...Piston, 10...Inner cylinder, 11...Fixing member, 11a...Fixing member body, 11c...Relief port, 12...Lock piece, 20...Valve case, 20c...Discharge port, 20d...Suction port, 21...Compression damping valve, 22...Extension check valve, 25...Relief valve, D...Buffer, DP...Damping passage, G...Air chamber, L...Hydraulic lock chamber, R1...Extension chamber, R2...Compression chamber, R3...Liquid chamber, T...Tank

Claims

1. A shock absorber 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 to divide the inside of the cylinder into an extension chamber and a compression chamber; a cylindrical tank; a free piston or elastic partition housed in the tank to divide the inside of the tank into a liquid chamber and an air chamber; a valve case fixed in the cylinder to separate the compression chamber and the liquid chamber; an inner cylinder housed in the cylinder and within the compression chamber; a fixing member fixed to the inner circumference of the cylinder to hold the inner cylinder and supported in the axial direction by the valve case; a locking piece connected to the piston rod and capable of penetrating either the inside or outside of the inner cylinder, and which, upon penetrating either the inside or outside of the inner cylinder, forms a hydraulic locking chamber on either the inside or outside of the inner cylinder; and a damping passage provided in the piston to connect the extension chamber and the compression chamber. A buffer comprising: a discharge port and an intake port provided in the valve case and connecting the pressure chamber and the liquid chamber; a pressure-side damping valve that opens and closes the discharge port and resists the flow of liquid from the pressure chamber to the liquid chamber; and an extension-side check valve that opens and closes the intake port and allows only the flow of liquid from the liquid chamber to the pressure chamber.

2. A buffer according to claim 1, wherein the lock piece, when it enters the outside of the inner cylinder, forms a hydraulic lock chamber on the outside of the inner cylinder.

3. A shock absorber according to claim 1, wherein the lock piece is a cylindrical shape with a C-shaped cross-section and elastic, connected to the piston rod via the piston and fitted onto the outer circumference of the inner cylinder, and when fitted onto the outer circumference of the inner cylinder, forms the hydraulic lock chamber between the cylinder and the inner cylinder, and the fixing member has a plurality of relief ports that penetrate the fixing member body in the axial direction, and the shock absorber is equipped with a relief valve that is stacked on the anti-pressure side chamber of the fixing member body and opens and closes the outlet ends of the relief ports.

4. A shock absorber according to claim 1, wherein the cylinder and the tank are formed from a single cylindrical structure.

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