Shock absorber

Abstract

To provide a shock absorber capable of appropriately exhibiting an impact absorption function.SOLUTION: A shock absorber 2 includes: a cylinder 6 connected to one of a suspension and a vehicle body; and a piston P fixed to a rod 5 connected to the other of the suspension and the vehicle body, sliding with an inner surface of the cylinder 6, and dividing an internal space of the cylinder 6 into a first chamber R1 and a second chamber R2. The piston P includes a cylindrical body 4 sliding on the inner surface of the cylinder 6, a valve V sliding in the cylindrical body 4 in accordance with acceleration applied to the valve V, and an energizing member F energizing the valve V to return to a basic position of the cylindrical body 4. A first flow passage W1 through which fluid flows from the first chamber R1 to the second chamber R2 and a second flow passage W2 through which the fluid flows from the second chamber R2 to the first chamber R1 are formed of the cylindrical body 4 and the valve V. Cross sectional areas of the first flow passage W1 and the second flow passage W2 vary on the basis of a relative position of the cylindrical body 4 and the valve V.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a shock absorber having a cylinder connected to one of a suspension and a vehicle body, and a piston connected to the other and dividing the internal space of the cylinder into a first chamber and a second chamber, and equipped with a valve that can change the flow rate of a flow path formed in the piston to connect the first chamber and the second chamber. [Background technology]

[0002] Conventionally, such a shock absorber is disclosed in, for example, Patent Document 1 (see

[0012] to

[0013] and FIG. 1).

[0003] A conventional shock absorber includes a cylinder 1 filled with a liquid such as hydraulic oil, and a piston 2 that divides the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2. The piston 2 is formed with a damping passage 3 that connects the extension-side chamber R1 and the compression-side chamber R2, and is configured so that the piston 2 can reciprocate inside the cylinder 1 at a low speed.

[0004] A pressure chamber R3 is formed inside the piston 2, and a free piston 9 is installed inside this pressure chamber R3, dividing the pressure chamber R3 into an extension-side pressure chamber 7 and a compression-side pressure chamber 8. The free piston 9 is biased by a spring element 10 so as to remain in the basic position of the pressure chamber R3.

[0005] The expansion-side pressure chamber 7 communicates with the expansion-side chamber R1 via an expansion-side flow path 5, and the compression-side pressure chamber 8 communicates with the compression-side chamber R2 via a compression-side flow path 6. A pair of bypasses 11 is formed between the compression-side chamber R2 and the compression-side pressure chamber 8. One of the bypasses 11 is provided with a compression-side bypass valve 15 that allows only a flow from the compression-side chamber R2 to the compression-side pressure chamber 8, and the other bypass 11 is provided with an expansion-side bypass valve 16 that allows only a flow from the compression-side pressure chamber 8 to the compression-side chamber R2. In particular, in this device, the flow resistance of the compression-side bypass valve 15 is set smaller than the flow resistance of the expansion-side bypass valve 16.

[0006] The effect of this configuration is described in prior art documents as follows: For example, when the frequency of vibration input to the shock absorber D is low, the amplitude is large, and therefore the flow rate of liquid flowing back and forth between the expansion-side chamber R1 and the contraction-side chamber R2 during one cycle of expansion / contraction increases. The displacement of the free piston 9 also increases in proportion to this flow rate. However, because the free piston 9 is biased by the spring element 10, as the displacement of the free piston 9 increases, the biasing force from the spring element 10 that the free piston 9 receives also increases. This generates a pressure difference between the pressure in the expansion-side pressure chamber 7 and the pressure in the contraction-side pressure chamber 8, reducing the pressure difference between the expansion-side chamber R1 and the expansion-side pressure chamber 7 and the pressure difference between the contraction-side chamber R2 and the contraction-side pressure chamber 8. As a result, the flow rate through the apparent flow path caused by the movement of the free piston 9 decreases. As the flow rate through this apparent flow path decreases, the flow rate through the passage 3a increases, and the damping force generated by the shock absorber D remains large.

[0007] Conversely, when high-frequency vibration is input to the shock absorber D, the amplitude is smaller than when low-frequency vibration is input, so the flow rate of fluid flowing between the expansion-side chamber R1 and the compression-side chamber R2 during one cycle of expansion / contraction is small, and the displacement of the free piston 9 is also small. Accordingly, the biasing force from the spring element 10 that the free piston 9 receives is also smaller. Therefore, the pressure in the expansion-side pressure chamber 7 and the pressure in the compression-side pressure chamber 8 become approximately equal, and the pressure difference between the expansion-side chamber R1 and the expansion-side pressure chamber 7 and the pressure difference between the compression-side chamber R2 and the compression-side pressure chamber 8 are larger than when low-frequency vibration is input, and the flow rate passing through the apparent flow path is larger than when low-frequency vibration is input. This increase in the flow rate passing through the apparent flow path reduces the flow rate in the expansion-side damping passage 3a, and the damping force generated by the shock absorber D is smaller than the damping force when low-frequency vibration is input.

[0008] In this way, in the prior art, it is possible to generate a large damping force for vibrations in the low frequency range and a small damping force for vibrations in the high frequency range, and it is possible to make the change in the damping force of the shock absorber D dependent on the input vibration frequency. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-185628 Summary of the Invention [Problem to be solved by the invention]

[0010] The above-mentioned prior art describes that when the frequency of vibration input to shock absorber D is low, the amplitude is large. However, the vibration frequency input to shock absorber D and the amplitude of piston 2 are not necessarily synchronized. For example, if the amplitude of piston 2 is constant, the higher the vibration frequency, the greater the flow rate of liquid flowing through passages 3a and 3b. Conversely, even if the vibration frequency is high, the flow rate may be reduced if the amplitude of piston 2 is small. In other words, the above-mentioned effect can only be achieved when one of the parameters is fixed.

[0011] The flow rate of the liquid passing through the piston 2 is proportional to the speed at which the piston 2 moves. The flow rate is also proportional to the pressure difference between the extension-side chamber R1 and the compression-side chamber R2. The operating state of the free piston 9 is determined by the pressure difference between the extension-side chamber R1 and the compression-side chamber R2. For example, the balance between the pressure difference and the load of the spring element 10 connected to the free piston 9 is Differential pressure < set load of spring element 10 / pressure-receiving area (pressure) of free piston 9 In this case, the free piston 9 does not operate. In this case, when the piston 2 operates, the liquid passes through the narrow passage 3a, and the damping force increases.

[0012] From this state, the pressure difference increases, Differential pressure = Set load of spring element 10 / Pressure-receiving area of ​​free piston 9 (pressure) This allows the free piston 9 to operate.

[0013] moreover, Differential pressure > Set load of spring element 10 / Pressure-receiving area (pressure) of free piston 9 As a result, the free piston 9 moves to the balanced position, and when the piston 9 moves, the liquid flows not only through the passages 3a and 3b but also through the extension-side passage 5 and the compression-side passage 6. As a result, the flow rate through the passages 3a and 3b is smaller than before the liquid is dispersed, and the damping force is smaller than when the liquid flows only through the passages 3a and 3b. As such, the effect of the obtained damping force cannot be explained by comparing frequencies.

[0014] Regarding the specific structure, the conventional shock absorber described above achieves low damping (softening) by releasing hydraulic oil based on the initial damping state when the piston 2 starts to move, which means that the initial state has to be set to a high damping state, i.e., a hard setting.

[0015] In addition, the free piston 9 of the pressure chamber R3 is actuated by the pressure difference between the expansion-side pressure chamber 7 and the compression-side pressure chamber 8, and this pressure difference depends on the speed of the piston 2. However, the discomfort felt by the passenger depends on the acceleration. Naturally, the acceleration and the speed of the piston 2 change in different ways, so there is a limit to how much discomfort can be eliminated by mechanical control based on the speed of the piston 2.

[0016] Furthermore, damping the suspension requires a response time associated with the movement of the free piston 9, resulting in poor response to high-frequency vibrations such as sudden bumps from the road surface. This can be improved by reducing the inertia of the free piston 9. However, the pressure chamber R3 becomes smaller, reducing the allowable stroke of the free piston 9, narrowing the adjustable range of the damping effect.

[0017] In addition, by providing the independent pressure chamber R3, the size of the piston 2 increases and the stroke becomes shorter, which reduces the damping effect on vibrations with high frequency and high amplitude.

[0018] As described above, conventional shock absorbers still have various problems to be solved, and there is a demand for shock absorbers that can properly perform their shock absorbing function. [Means for solving the problem]

[0019] (Features and configuration) The shock absorber according to the present invention has the following characteristic configuration: A shock absorber used in a vehicle suspension that expands and contracts along an axis, a cylinder connected to either the suspension or the vehicle body; a piston that is fixed to a rod connected to either the suspension or the vehicle body and slides on the inner surface of the cylinder, dividing the internal space of the cylinder into a first chamber and a second chamber; the piston has a cylindrical body that slides on the inner surface of the cylinder, a valve that slides inside the cylindrical body in response to acceleration applied to the valve, and a biasing member that biases the valve to return to its basic position in the cylindrical body, a first flow path through which a fluid flows from the first chamber to the second chamber, and a second flow path through which the fluid flows from the second chamber to the first chamber, are formed by the cylindrical body and the valve; The cross-sectional areas of the first flow path and the second flow path are configured to change based on the relative positions of the cylindrical body and the valve.

[0020] (effect) As in this configuration, the cross-sectional areas of the first and second flow paths change, which changes the manner in which the piston moves relative to the cylinder. For example, if the cross-sectional area increases and the fluid flow rate increases, the piston moves easily relative to the cylinder. On the other hand, if the cross-sectional area decreases and the fluid flow rate decreases, the piston moves less easily relative to the cylinder.

[0021] Changes in the cross-sectional area of ​​the first and second flow paths affect the hard and soft characteristics of the suspension. In this configuration, the valve's cross-sectional area is determined not by the pressure difference between the fluid in the first and second chambers, but by the vertical acceleration acting on the valve due to the vertical vibration of the suspension's sprung mass. This acceleration is felt by the occupant, and the function required of a suspension is to improve the occupant's physical sensation. Therefore, a shock absorber with this configuration allows for suspension settings that are linked to the occupant's physical sensation. Furthermore, by appropriately selecting the weight and dimensions of the valve and the spring constant of the biasing member, the degree of freedom in setting the damping characteristics according to the acceleration acting on the valve is increased. This allows for a suspension that provides optimal damping effect depending on road conditions.

[0022] (Features and configuration) In the shock absorber according to the present invention, the cylinder is connected to the suspension, the rod is connected to the vehicle body, the first chamber is provided on the suspension side with respect to the piston, and the second chamber is provided on the vehicle body side with respect to the piston, the first flow path includes a first port provided in a wall portion of the cylindrical body and communicating with the first chamber, and a second port communicating with the second chamber; the valve includes a first opening that can communicate with the first port, a second opening that can communicate with the second port, and a first communication passage that extends between the first opening and the second opening, the second flow path includes a third port provided in a wall portion of the cylindrical body and communicating with the second chamber, and a fourth port communicating with the first chamber; the valve includes a third opening that is communicable with the third port, a fourth opening that is communicable with the fourth port, and a second communication passage that extends between the third opening and the fourth opening, The valve may be configured such that, when the valve is in the basic position, the smaller of the communication area between the first port and the first opening and the communication area between the second port and the second opening, and the smaller of the communication area between the third port and the third opening and the communication area between the fourth port and the fourth opening, are maximized.

[0023] (effect) In this embodiment, the valve is configured so that fluid flows easily through the first and second flow paths when the valve is in the basic position. The flow rate of the fluid varies based on, for example, the communication area of ​​the first port and the first opening and the communication area of ​​the second port and the second opening. These communication areas are the smallest of the cross-sectional areas of the first or second flow path, and the value of this communication area largely determines the flow characteristics of the fluid. In particular, the smaller of these two communication areas is highly dependent.

[0024] Therefore, when comparing the smaller of the two communication areas at each valve position, the smaller value is set so that it is greatest when the valve is in the home position. This ensures sufficient fluid flow when the valve is in the home position, minimizes the damping coefficient, and facilitates piston movement. This configuration also applies to the relationship between the communication area between the third port and the third opening and the communication area between the fourth port and the fourth opening.

[0025] With this configuration, for example, when a vehicle travels over an uneven road and the wheel is impacted by the road surface, the valve's inertia tends to keep it in place. This allows the maximum amount of fluid to flow through the first and second flow paths formed by the cylinder and the valve, allowing the piston to move easily relative to the cylinder. This allows the shock absorber's damping force to be set low, allowing the wheel impact to be appropriately released and reducing the transmission of vibration to the occupants.

[0026] As the upward thrust against the wheel continues, the valve moves relative to the cylinder as the piston moves up and down, reducing the value of the communication area, thereby enhancing the effect of damping subsequent wheel vibrations.

[0027] (Features and configuration) In the shock absorber according to the present invention, the first opening and the second opening have the same groove shape extending along the circumferential direction of the axis, the first port includes a first lateral groove provided elongated along the circumferential direction and a first longitudinal groove extending from a center position of the first lateral groove toward the first chamber, the second port includes a second lateral groove provided elongated along the circumferential direction and a second longitudinal groove extending from a center position of the second lateral groove toward the second chamber, The first transverse groove is formed to be longer than the second transverse groove, The first longitudinal groove and the second longitudinal groove have the same length along the extension direction of the axis, and the width of the first longitudinal groove along the circumferential direction is narrower than the width of the second longitudinal groove, the third opening has the same shape as the first opening, the fourth opening has the same shape as the second opening, The third port and the first port, and the fourth port and the second port, may have the same shape, and the third vertical groove of the third port may extend from the third lateral groove toward the second chamber, and the fourth vertical groove of the fourth port may extend from the fourth lateral groove toward the first chamber.

[0028] (effect) This configuration facilitates setting for damping vertical vibrations of the vehicle. For example, when the valve is displaced toward the second chamber, the first opening maintains communication with the first lateral groove of the first port, while the second opening communicates with the second longitudinal groove of the second port. Because the width of the second longitudinal groove is narrower than the width of the second lateral groove, the communication area between the second opening and the second longitudinal groove is rapidly reduced. In other words, when acceleration acts on the valve and the valve is displaced significantly, the flow of fluid is significantly reduced, making it difficult for the piston to move.

[0029] By controlling the fluid flow in this way, for example, the wheel thrust immediately after the wheel hits a bump can be appropriately released, reducing the thrust acting on the vehicle's sprung mass. If the valve subsequently begins to displace due to the acceleration of the thrust, the fluid resistance is increased, increasing the damping coefficient and enabling repeated vibrations in the sprung mass to be attenuated quickly.

[0030] Furthermore, by making the width of the first longitudinal groove different from the width of the second longitudinal groove, it is possible to make the damping effect when the wheel moves up and down different. For example, in this configuration, the width of the first longitudinal groove is formed narrower than the width of the second longitudinal groove. Looking at the first flow path, when the valve is raised and the second opening is connected to the second longitudinal groove, the communication area becomes larger than the communication area when the valve is lowered and the first opening is connected to the first longitudinal groove. In other words, in the first flow path that flows fluid from the first port to the second port, the damping effect is large when the valve is in the lower position and the damping effect is small when the valve is in the upper position.

[0031] Specifically, consider the case where a wheel hits a bump, causing the absorber to compress instantaneously, then begin to extend. When the absorber extends, fluid flows from the second chamber to the first chamber, so it is the second flow path that contributes to the damping effect. When the absorber begins to extend, the valve is displaced downward. For the second flow path, when the valve descends and the fourth opening communicates with the fourth longitudinal groove, the communication area becomes larger than when the valve ascends and the third opening communicates with the third longitudinal groove. Therefore, the damping coefficient value becomes slightly suppressed when the absorber begins to extend, and although the absorber extends, the rise in sprung mass is suppressed, reducing the feeling of being pushed up by the occupant.

[0032] Furthermore, as the absorber continues to expand and its expansion rate decreases, the valve begins to displace upward from its reference position. The communication area of ​​the second flow path becomes smaller, and the damping coefficient value increases. This rapidly suppresses further expansion of the absorber, preventing the spring mass from rising. As a result, upward overshoot of the spring mass is suppressed, further enhancing the damping effect. In this way, by making the width of the first longitudinal groove different from that of the second longitudinal groove, optimal damping effect can be achieved even when the valve is subjected to repeated up and down acceleration.

[0033] (Features and configuration) In the shock absorber of the present invention, the fluid is filled in the internal space of the cylindrical body, and the valve divides the internal space into a first chamber and a second chamber along the extension direction of the axis, and is provided with a through passage connecting the first chamber and the second chamber, and it is advantageous if a throttling portion is formed in the through passage to restrict the flow rate of the fluid.

[0034] (effect) By filling the interior of the cylinder with fluid as in this configuration, excessive vibration of the valve due to the applied acceleration is prevented. Furthermore, by providing a through-passage in the valve, allowing fluid to flow between the first and second chambers, the up and down movement of the valve is smooth. Furthermore, by providing a throttle portion in the through-passage, the flow of fluid is restricted, significantly reducing the up and down wobble of the valve. These features make it easier to set the movement characteristics of the valve inside the cylinder, and increase the degree of freedom in setting the damping characteristics of the shock absorber. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 is an explanatory diagram showing the configuration of a suspension according to a first embodiment; [Figure 2] FIG. 1 is a cross-sectional view showing a main configuration of a shock absorber according to a first embodiment; [Figure 3] FIG. 1 is an exploded perspective view showing a configuration of a shock absorber according to a first embodiment; [Figure 4]FIG. 1 is an explanatory diagram showing the damping characteristics of a shock absorber according to a first embodiment; [Figure 5] FIG. 10 is an explanatory diagram showing the vibration damping effect of a shock absorber according to a conventional configuration. [Figure 6] FIG. 1 is an explanatory diagram showing an operation mode of the shock absorber according to the first embodiment; [Figure 7] Graph showing changes in sprung displacement and the like according to the first embodiment [Figure 8] FIG. 10 is an explanatory diagram showing the configuration and damping characteristics of a cylindrical body according to a second embodiment. [Figure 9] FIG. 10 is a cross-sectional view showing a main configuration of a shock absorber according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0036] [First embodiment] (overview) The configuration of a suspension according to a first embodiment of the present invention is shown in Figure 1. Here, a typical one-wheel, two-degree-of-freedom model for a four-wheel vehicle will be described as an example. That is, a sprung structure such as a body frame (hereinafter referred to as "sprung") and an unsprung structure such as wheels and various support arms (hereinafter referred to as "unsprung") are connected by a spring 1 and a shock absorber 2 (hereinafter referred to as "absorber 2"). A spring 3 is shown below the unsprung structure, but this spring 3 is the elastic element of the wheel, etc.

[0037] The absorber 2 of this configuration quickly damps sprung vibrations when the vehicle is traveling, and includes a cylinder 4 with a piston P on the outside and a valve V that slides up and down inside the cylinder 4. The cylinder 4 is filled with hydraulic oil, and a flow path for the hydraulic oil is formed by the cylinder 4 and the valve V. When the vehicle is traveling, vertical acceleration acts on the valve V, and the cross-sectional area of ​​the flow path changes as the relative position of the valve V with respect to the cylinder 4 changes, and the damping characteristics of the absorber 2 are adjusted according to road conditions.

[0038] (piston) The configuration of the absorber 2 according to the first embodiment is shown in Figures 2 and 3. In this embodiment, a rod 5 that holds a piston P at its tip end of the absorber 2 is connected to the vehicle body, and a cylinder 6 that slidably houses the piston P is connected to the suspension side that includes the wheels. A narrow diameter portion 51 is formed at the tip of the rod 5, and the piston P is fitted onto the narrow diameter portion 51 and secured in place by a nut 52.

[0039] The piston P divides the internal space of the cylinder 6 into a first chamber R1 on the wheel side and a second chamber R2 on the vehicle body side. The piston P includes a cylindrical body 4 and a valve V that slides relative to one another inside the cylindrical body 4. When the vehicle is running, the absorber 2 expands and contracts, and as a result, the hydraulic oil held inside the cylinder 6 flows back and forth between the first chamber R1 and the second chamber R2 via the flow path formed by the cylindrical body 4 and the valve V.

[0040] (cylindrical body) 2 and 3, the cylindrical body 4 is primarily composed of a cylindrical wall portion 41, and is provided on one side, facing the vehicle body, with an upper cover 71, a first valve 81, a valve spring 811, and a spring retainer 812. Similarly, on the other side, facing the wheel, is provided with a lower cover 72, a second valve 82, a valve spring 821, and a spring retainer 822. These components are inserted into the small-diameter portion 51 of the rod 5, so that the inner diameter portions of the upper cover 71 and the lower cover 72 abut against the small-diameter portion 51, and the cylindrical body 4 is fitted onto the upper cover 71 and the lower cover 72. The upper surface of the flange 711 of the upper cover 71 and the end face 42 of the cylindrical body 4 are flush with the lower surface of the flange 721 of the lower cover 72 and the end face 42 of the cylindrical body 4, and the annular first valve 81 and the second valve 82 abut against the respective end faces 42.

[0041] The first valve 81 and the second valve 82 have, for example, four spring holes 813, 823 formed on the surface of each valve, in which coil-shaped valve springs 811 are disposed, and the four valve springs 811 are further held down by spring retainers 812, 822 formed from annular plate members. As a result, the first valve 81 and the second valve 82 are normally pressed against the end face 42 of the cylindrical body 4. Furthermore, the relative rotational positions of the first valve 81 and the second valve 82 with respect to the cylindrical body 4 are restricted in order to form a flow path, which will be described later. For this purpose, first locking protrusions 44 are formed on the respective step portions 43 of the cylindrical body 4 that house the upper cover 71 and the lower cover 72, and notched first locking recesses 712, 722 are formed on the upper cover 71 and the lower cover 72 at positions facing the first locking protrusions 44.

[0042] Furthermore, second locking protrusions 713, 723 are formed on the surfaces of the bosses of the top cover 71 and the bottom cover 72, and notched second locking recesses 814, 824 are formed on the inner edge portions of the first valve 81 and the second valve 82 facing these protrusions. These determine the relative rotational phases of the top cover 71, the bottom cover 72, the first valve 81, and the second valve 82 with respect to the cylindrical body 4. Notches 815, 825 having a predetermined length along the circumferential direction are formed on the outer edges of the first valve 81 and the second valve 82, and these notches 815, 825 face a port passage Pa communicating with a third port 3P, which will be described later, and a port passage Pa communicating with the first port 1P.

[0043] With this configuration, the first flow path W1 and the second flow path W2 formed by the cylindrical body 4 and the valve V each serve as a one-way flow path for hydraulic oil. When hydraulic oil flows through the first flow path W1, the first valve 81, which is normally closed by the valve spring 811, is pushed by the hydraulic pressure and displaced toward the second chamber R2, and the second port 2P communicates with the second chamber R2 through three port passages Pa in FIG. 3 . On the first chamber R1 side, the notch 825 formed in the second valve 82 faces the three port passages Pa leading to the first port 1P, and these port passages Pa are always open. The same configuration applies to the second flow path W2, which allows hydraulic oil to flow one-way from the second chamber R2 to the first chamber R1.

[0044] The wall 41 of the cylindrical body 4 is formed with a pair of a first port 1P and a second port 2P, and a pair of a third port 3P and a fourth port 4P, positioned 180 degrees apart. The first port 1P and the third port 3P have the same shape, and the second port 2P and the fourth port 4P have the same shape. That is, two different ports are arranged side by side in the same order along the flow direction of the hydraulic oil. The first port 1P includes a first lateral groove 1PH extending elongatedly along the circumferential direction and a first longitudinal groove 1PV extending from the center of the first lateral groove 1PH toward the first chamber R1. The second port 2P includes a second lateral groove 2PH extending elongatedly along the circumferential direction and a second longitudinal groove 2PV extending from the center of the second lateral groove 2PH toward the second chamber R2. In this embodiment, the lateral grooves PH and longitudinal grooves PV penetrate the wall 41.

[0045] The circumferential length of the first lateral groove 1PH of the first port 1P is shorter than the circumferential length of the second lateral groove 2PH of the second port 2P. On the other hand, the length of the first longitudinal groove 1PV along the axis X is the same as the length of the second longitudinal groove 2PV in the same direction. However, the circumferential width of the first longitudinal groove 1PV is wider than the width of the second longitudinal groove 2PV. These differences in shape are intended to appropriately set the damping coefficient, which will be described later.

[0046] The first lateral groove 1PH and the first longitudinal groove 1PV communicate with the first chamber R1 via, for example, three port passages Pa that penetrate the interior of the wall portion 41, and the second lateral groove 2PH and the second longitudinal groove 2PV communicate with the second chamber R2 via three port passages Pa that also penetrate the interior of the wall portion 41. The total cross-sectional area of ​​the port passages Pa is set so as to ensure the maximum flow rate of hydraulic oil expected during relative displacement between the cylindrical body 4 and a valve V (described later).

[0047] A disk-shaped partition plate 10 is provided at the lower end of the first chamber R1 of the cylindrical body 4 so as to be slidable along the direction of the axis X relative to the inner wall of the cylindrical body 4. The space below the partition plate 10 serves as an air chamber r3 filled with air rather than hydraulic oil. With this configuration, when the wheel rises and the piston P is pushed into the cylinder 6, causing the rod 5 to enter the cylinder 6, the partition plate 10 descends by an amount equivalent to the volume of the rod 5, compressing the air chamber r3. This absorbs the change in the spatial volume of the cylinder 6 relative to the amount of hydraulic oil sealed inside the cylinder 6.

[0048] (valve) As shown in Figures 2 and 3, the valve V that slides back and forth inside the cylindrical body 4 is also cylindrical. The wall portion 41 has a first opening 1s and a second opening 2s arranged side by side along the direction of extension of the axis X. Identical openings, a third opening 3s and a fourth opening 4s, are formed at opposite radial positions. Each opening is an elongated groove extending in the circumferential direction. However, each opening only opens outward toward the cylindrical body 4, not toward the rod 5 inside.

[0049] The first opening 1s and the second opening 2s, and the third opening 3s and the fourth opening 4s are connected to each other via, for example, three communication passages sa formed inside the wall portion 41 of the valve V. The total cross-sectional area of ​​the communication passages sa is set to an area that can maintain the maximum amount of hydraulic oil flowing when the valve V is displaced relative to the cylindrical body 4.

[0050] The valve V does not rotate circumferentially relative to the cylindrical body 4. To achieve this, for example, a locking screw 45 is threaded into the wall portion 41 of the cylindrical body 4, with its tip protruding toward the valve V. Meanwhile, a locking groove Va into which the end of the locking screw 45 engages is formed on the surface of the valve V, extending along the axis X. Note that instead of using the locking screw 45, a locking protrusion may be integrally formed on the inner surface of the cylindrical body 4.

[0051] 2, the center of the valve V faces the small diameter portion 51 of the rod 5 across a gap. This gap is filled with hydraulic oil, and both ends of the valve V along the extension direction of the axis X are connected by the hydraulic oil. In other words, the valve V is free to reciprocate inside the cylindrical body 4, and slides relative to the inner surface of the cylindrical body 4 in response to the acceleration acting on it.

[0052] The valve V divides the internal space of the cylindrical body 4 into a first small chamber r1 and a second small chamber r2 along the direction of extension of the axis X, and has a through passage Vr at the center of the valve that connects the first small chamber r1 and the second small chamber r2. A throttle portion Vo that restricts the flow rate of the fluid is formed in this through passage Vr.

[0053] A stepped spring bearing portion Vb is formed around the entire circumference on the inner surface of the valve V, approximately in the center in the direction along the axis X. A biasing member F, for example, composed of a coil spring, is attached to this portion. Both ends of the biasing member F are fixed to the spring bearing portion Vb and the lower cover 72, and the biasing member F supports the weight of the valve V and biases it so that the valve V returns to an approximately central position along the axis X with respect to the cylindrical body 4. If the valve V is displaced downward, the biasing member F will try to push the valve V up, and if the valve V is displaced upward, the biasing member F will try to pull the valve V down. This position is the home position of the valve V.

[0054] In this embodiment, the hydraulic fluid flow rate in the first flow path W1 and the second flow path W2 is increased when the valve V is in the home position. The hydraulic fluid flow rate varies based on, for example, the communication area between the first port 1P and the first opening 1s and the communication area between the second port 2P and the second opening 2s. The flow rate is particularly dependent on the smaller of the two communication areas. Therefore, the smaller of the two communication areas is set to be the largest when the valve V is in the home position, comparing the values ​​at each position of the valve V. This allows hydraulic fluid to flow more easily from the first chamber R1 to the second chamber R2, minimizing the damping coefficient. This configuration also applies to the relationship between the communication area between the third port 3P and the third opening 3s and the communication area between the fourth port 4P and the fourth opening 4s.

[0055] With this configuration, for example, when a vehicle is traveling on an uneven road and a wheel is impacted by the road surface, the first flow path W1 and the second flow path W2 formed by the cylindrical body 4 and the valve V are communicated so that the maximum amount of hydraulic oil flows through them. At this moment, the movement of the valve V is small, and the piston P moves easily relative to the cylinder 6. As a result, the damping force of the absorber 2 is set low, and the absorber easily compresses when the wheel is impacted, reducing the transmission of vibration to the occupant.

[0056] Thereafter, for example, when the absorber elongates and the vehicle, which is in the sprung state, begins to rise, the valve V is subjected to downward acceleration and moves downward relative to the cylindrical body 4, and the fourth opening 4s comes into communication with the fourth longitudinal groove 4PV of the fourth port 4P, and the communication area that controls the flow rate of the second flow path W2 suddenly decreases. This suppresses the relative movement between the piston P and the cylinder 6, thereby enhancing the subsequent wheel vibration damping effect.

[0057] The above configuration forms the absorber 2 that damps sprung vibrations that occur when the vehicle is traveling. In the present invention, the valve V is displaced in accordance with the acceleration acting on itself while the vehicle is traveling, and successively changes the cross-sectional areas of the first flow path W1 and the second flow path W2. As a result, for example, when the vehicle runs over a bump, the large upward thrust caused by the bumping reduces the damping effect of the absorber 2, causing the absorber to quickly contract, and when the up-and-down vibrations in the sprung mass continue after that, the damping effect is increased, quickly damping the vibrations.

[0058] (Setting the damping coefficient) Fig. 4 shows the damping characteristics of the absorber 2 used in this embodiment. Fig. 5 shows how sprung displacement and other changes occur when a vehicle equipped with a conventional absorber goes over a step that is one step higher. Fig. 6 shows how sprung displacement and other changes occur when the absorber 2 of this embodiment is used on a road surface with the same one-step step. Fig. 7 shows how the valve V operates immediately after going over the step in Fig. 6.

[0059] FIG. 4 shows the damping characteristics of the absorber 2 of this embodiment. The horizontal axis represents the displacement of the valve V relative to the cylindrical body 4, with the right representing the top and the left representing the bottom. The vertical axis represents the absolute value of the damping coefficient, with the top representing the case where the absorber 2 expands and the bottom representing the case where the absorber 2 contracts. When the absorber 2 contracts, as shown by the solid line in FIG. 2, hydraulic oil flows from the first chamber R1 through the first port 1P and the second port 2P into the second chamber R2. Conversely, when the absorber 2 expands, as shown by the dashed line in FIG. 2, hydraulic oil flows from the second chamber R2 through the third port 3P and the fourth port 4P into the first chamber R1. The arrows attached to each port in FIG. 4 indicate the hydraulic oil flow direction, and the length of the arrow indicates the maximum hydraulic oil flow rate.

[0060] As shown in Figure 4, as the displacement of valve V increases vertically, the maximum flow rate of hydraulic oil decreases, the damping coefficient increases, and the damping effect improves. In this regard, the shapes of third port 3P, fourth port 4P, etc. are set so that when absorber 2 expands, the damping coefficient increases more when valve V is displaced downward than when it is displaced upward. Conversely, when absorber 2 contracts, the shapes of first port 1P, second port 2P, etc. are set so that the damping coefficient increases more when valve V is displaced upward than when it is displaced downward.

[0061] This is based on, for example, the shapes of the first transverse groove 1PH and the first longitudinal groove 1PV of the first port 1P and the second transverse groove 2PH and the second longitudinal groove 2PV of the second port 2P. When the valve V moves up and down, the first opening 1s and the second opening 2s of the valve V move up and down relative to the first port 1P and the second port 2P of the cylindrical body 4, and the communication area between them changes appropriately, as shown in black in FIG. 4. For example, when the valve V moves downward, the first longitudinal groove 1PV and the first opening 1s communicate with each other to a smaller extent, while the second transverse groove 2PH and the second opening 2s maintain a relatively wide communication state. Conversely, when the valve V moves upward, the communication between the second longitudinal groove 2PV and the second opening 2s becomes smaller than when the valve V moves downward, and the communication between the first transverse groove 1PH and the first opening 1s becomes even smaller than when the valve V moves downward. In this way, for the first port 1P and the second port 2P, the flow rate of hydraulic oil is less when the valve V moves upward than when it moves downward, and for the third port 3P and the fourth port 4P, the flow rate of hydraulic oil is less when the valve V moves downward than when it moves upward.

[0062] When valve V is in the upper position, the absolute value of the compression-side damping coefficient is greater than the absolute value of the extension-side damping coefficient. On the other hand, when valve V is in the lower position, the absolute value of the extension-side damping coefficient is greater than the absolute value of the compression-side damping coefficient. With this configuration, as will be described later, sprung vibration can be quickly damped.

[0063] Figure 5 shows the calculation results for vibration damping using two types of valves with conventional structures. These valves also move up and down with acceleration, but the area of ​​the hydraulic oil passage that passes through the piston is constant regardless of their position. The graph on the left in Figure 5 is for a damping coefficient of 1000, and the graph on the right is for a damping coefficient of 300.

[0064] The sprung displacement is determined based on the unsprung displacement. However, to do so, several parameters must be set. Specifically, as shown in Figure 1, the unsprung mass m1, sprung mass m2, tire spring constant k1, coil spring constant k2, absorber damping coefficient c2, etc. are set, and then the road surface displacement input X0 and unsprung displacement X1 are input to determine the sprung displacement X2. Because the road acceleration can be determined from the unsprung displacement X1, the change in sprung acceleration can be determined by determining the sprung displacement X2 and taking the road surface acceleration into account.

[0065] The road surface in Figure 5 changes from a low road surface height H1 to a high road surface height H2 across a step, which causes the vertical displacement of the wheel, or essentially the unsprung displacement, to rise sharply when passing over the step.

[0066] Regarding wheel displacement, slight up and down movement remains immediately after going over a bump due to deformation of the rubber portion, but then quickly subsides. Meanwhile, the length of the absorber 2 expands and contracts as the sprung portion of the vehicle begins to vibrate due to being pushed up by the road surface. Therefore, the vibration mode of the absorber 2 is approximately the same as that of the sprung portion.

[0067] The damping effect of the sprung displacement is greater with a damping coefficient of 1000 than with a damping coefficient of 300. During damping, the sprung mass is subjected to vertical acceleration due to the spring characteristics of spring 1, the sprung mass weight, etc. The phase of the change in this acceleration is opposite to the same phase as the sprung displacement.

[0068] Valve displacement is calculated from the difference between the sprung displacement and the valve displacement. When going over a step, the inertia of the valve V delays its ascent. Therefore, the valve V initially displaces downward relative to the piston P. After that, the valve V reverses its displacement direction due to the biasing member F that supports the valve V, and follows the sprung displacement with a certain delay.

[0069] Furthermore, since there are many literature on this type of single-wheel, two-degree-of-freedom suspension model (Kagawa University doctoral dissertation, Research on optimal design and component technology development for automobile suspension control systems, March 2009, Takema Shuichi, etc.), the specific calculation process will be omitted here.

[0070] Figure 6 shows the damping behavior using the valve of this embodiment for the same road surface. A characteristic feature of this configuration is that the valve V moves up and down in response to acceleration depending on the vehicle's driving state, changing the flow area of ​​the hydraulic oil passage. The valve V is biased so as to be stable in its basic position relative to the cylindrical body 4, and moves relative to the cylindrical body 4 in response to the up and down movement of the sprung mass. The discomfort felt by vehicle occupants is due to the magnitude of acceleration caused by road surface conditions. Therefore, by quickly adjusting the damping characteristics of the absorber 2 in response to changes in acceleration, it is possible to set the suspension in accordance with the occupant's physical sensation, significantly improving the ride comfort of the vehicle.

[0071] Specifically, first, the resonant frequency Hz2 of the valve V is made to approach the resonant frequency Hz1 of the sprung mass. The resonant frequency Hz1 is, for example, 1 Hz. This is set based on the mass of the valve V, the spring constant of the biasing member F, and the viscosity of the hydraulic oil filled around the valve V. This allows, for example, Valve resonance frequency Hz2 < 5 × sprung resonance frequency Hz1 This makes it easier to suppress the vibration of the sprung mass.

[0072] According to the action of the valve V, when the vehicle approaches an uneven road surface and the sprung mass is strongly pushed up, the flow path area of ​​the first flow path W1 is set large to allow the unsprung mass to rise. On the other hand, when the sprung mass subsequently vibrates up and down repeatedly, the flow path areas of the first flow path W1 and the second flow path W2 are set small to restrict the up and down movement of the unsprung mass and reduce the sprung mass displacement.

[0073] (Valve operation mode) Figure 7 shows a specific example of valve V. As shown in Figure 6, the sprung acceleration, sprung displacement, and valve relative displacement are plotted for the changes occurring immediately after the vehicle goes over a step, as enclosed by the dashed line.

[0074] Point A on the solid line showing sprung displacement in Figure 7 is the position where the vehicle begins to enter an uneven road surface. The sprung mass begins to rise from this point. The suspension spring 1 and absorber 2 suddenly compress the moment the vehicle runs over a step, and absorber 2 begins to extend from point A. When running over a step, inertia acts on valve V. For this reason, the moment the wheel runs over the step, valve V is in its basic position relative to cylinder 4. The opening areas of first flow path W1 and second flow path W2, through which hydraulic oil flows, are at their maximum. In this state, the damping effect of absorber 2 is small, allowing the wheel to rise suddenly and suppressing upward displacement of the sprung mass. In other words, the feeling of being pushed up by the occupant is reduced.

[0075] The state of the valve V in each state after point A of the sprung displacement in Figure 7 is shown in Figure 4. The lower column in Figure 7 shows whether the absorber 2 is in the extension stroke or compression stroke, and whether the relative displacement of the valve is up or down.

[0076] At point B, the sprung mass gradually displaces upward due to the biasing force of spring 1, and the rising speed becomes approximately constant. Due to its own inertia, valve V lags behind the movement of the sprung mass and is displaced downward at its maximum relative to cylinder 4. The absorber 2 is in the midst of extending, shorter than its neutral length, and hydraulic oil flows from the second chamber R2 to the first chamber R1 via the second flow path W2. At point B, valve V's downward displacement is at its maximum, and the displacement at this time is, for example, "-3." The communication area between the fourth longitudinal groove 4PV and the fourth opening 4s, i.e., the opening area of ​​the second flow path W2, is reduced, increasing the damping coefficient and enhancing the damping effect. This weakens the force of spring 1 that tends to raise the sprung mass, suppressing excessive rise of the sprung mass.

[0077] Point C is the state where the sprung displacement is nearly maximum. The sprung mass exceeds the stable height BH2 after vibration damping, and the spring 1 is in an extended state. Here, the downward sprung mass acceleration is nearly maximum. The upward velocity of the sprung mass becomes nearly zero, and the occupant no longer feels the upward thrust they had felt up until then; instead, they feel a floating sensation. The extension of absorber 2 reaches the end, reaching point C'. As the extension velocity of absorber 2 decreases, valve V begins to displace upward from its reference position. The communication area of ​​second flow path W2 becomes smaller, and the value of the damping coefficient increases. Therefore, further extension of absorber 2 is rapidly suppressed, and the rise of the sprung mass is stopped. As a result, upward overshoot of the sprung mass is suppressed, and the damping effect is further enhanced.

[0078] The upward displacement of the sprung mass is suppressed by the function of this absorber 2 from point A to point C'. Therefore, the floating sensation felt by the occupant at point C and other points is smaller than with conventional absorbers. After this, the sprung mass begins to descend, and absorber 2 moves into the compression stroke. The hydraulic oil flow path switches from second flow path W2 to first flow path W1. The relative displacement of valve V is "0", allowing the hydraulic oil to flow easily, and the operation of first valve 81 and second valve 82 becomes agile, resulting in rapid switching of the flow path.

[0079] At point D, the sprung mass, which has started to descend, is descending at a constant speed. The flow path has switched from the second flow path W2 to the first flow path W1. The relative displacement of the valve V, which is lagging behind due to inertia, is "+2" upward, and the communication area between the second longitudinal groove 2PV and the second opening 2s is reduced. This reduces the flow rate of hydraulic oil, increasing the damping coefficient and suppressing further sprung mass downward.

[0080] When the sprung displacement passes point D and drops to point E, the length of spring 1 falls below its basic length, and the spring's force toward the extension side increases, further reducing the sprung's descent speed. At point E, the relative displacement of valve V becomes "0" and the opening area of ​​first flow path W1 becomes maximum again. This allows the hydraulic oil to flow easily and reduces the operating resistance of piston P. The spring's force functions effectively, and the piston's descent speed decreases quickly. The difference in height from stable height BH2 to point E is smaller than the same difference in height at point C.

[0081] As the sprung mass passes point E and heads toward the next lowest point, it descends and absorber 2 is still in the compression stroke. The relative displacement of valve V shifts downward, and the damping coefficient of valve V increases. This suppresses further compression of absorber 2.

[0082] Point F is the state after the sprung mass has passed its lowest point and started to rise. At this point, the sprung mass acceleration is slightly upward, but the deviation from the stable height BH2 is already small, and the biasing force trying to return the sprung mass to the stable height BH2 is small.

[0083] The flow path switches again from the first flow path W1 to the second flow path W2. The relative displacement of the valve is "-1," and the communication area between the fourth longitudinal groove 4PV and the fourth opening 4s decreases, increasing the damping coefficient. However, compared to the state at point B, the communication area between the third longitudinal groove 3PV and the third opening 3s and the communication area between the fourth longitudinal groove 4PV and the fourth opening 4s at point F are larger, so the absolute value of the damping coefficient is smaller than at point B, and the damping effect is also smaller. After this, the sprung mass repeatedly moves up and down, but the deviation from the stable height BH2 gradually decreases due to the effect of the throttle portion Vo formed on the inner surface of the valve V, and the vibration ends.

[0084] As described above, the absorber 2 of this configuration, which can adjust the flow characteristics of the hydraulic oil in accordance with the acceleration acting on the valve V, can temporarily tolerate sudden contraction of the absorber 2, and then enhance the damping effect in the subsequent vibration damping process. Therefore, it is possible to obtain an absorber 2 with high damping effect, which makes it difficult for the occupant to feel uncomfortable vibrations due to vertical movement. Moreover, the damping characteristics can be set as desired by appropriately selecting the weight and dimensions of the valve V, the spring constant of the biasing member F, etc.

[0085] Second Embodiment 8(a) and 8(b) show another embodiment of the first port 1P and the second port 2P (both shown with dashed lines) provided in the cylindrical body 4. Note that the third port 3P and the fourth port 4P (shown with solid lines) have the same configuration but are provided inverted, so their explanation will be omitted. Also, in FIG. 8, the curves in FIG. 4 are shown with thin lines.

[0086] In the example of Figure 8(a), the first port 1P is roughly square-shaped, and the second port 2P is shaped like the Japanese katakana character "e." The graph also shows how the damping coefficient changes. The graph showing the damping coefficient is simplified, but the vertical and horizontal axes are the same as in Figure 4.

[0087] In this example, the change in the damping coefficient is reversed from that of the first embodiment shown in Figure 4. In this configuration, the hydraulic oil is less likely to flow in response to an upward thrust, for example, when approaching a road surface, and the sprung mass tends to rise together with the unsprung mass. Therefore, a strong damping effect can be expected from the beginning. This setting is suitable for cases where the vehicle often travels on roads without large bumps, such as ordinary roads or expressways.

[0088] On the other hand, in the example of Fig. 8(b), a substantially rectangular area is provided as the first port 1P, and a narrow vertical groove is connected to this area so that the opening width of the first port 1P narrows as the vertical displacement of the valve V increases. The second port 2P has the same "E" shape as in Fig. 8(a).

[0089] In this configuration, when the valve V is near its home position, a large opening area is ensured between the first port 1P and the first opening 1s. On the other hand, when the valve V is displaced significantly up or down, a large opening area is ensured between the second port 2P and the second opening 2s. In other cases, the opening area between the first port 1P and the first opening 1s and the opening area between the second port 2P and the second opening 2s are small. Therefore, when the valve V is near its home position, the damping coefficient is increased, and then temporarily decreased when the valve V has displaced a predetermined amount. Thereafter, the damping coefficient is increased again as the valve V is displaced.

[0090] When the valve V is in the base position, the biasing force of the biasing member F is small, and the valve V easily vibrates up and down. This causes the damping coefficient to change sensitively, which can lead to a deterioration in ride comfort depending on road conditions. However, the configuration shown in FIG. 8(b) can eliminate disturbances in the damping characteristics, particularly when the suspension is in the standard state, and improve the ride comfort of the vehicle. Third Embodiment

[0091] As shown in Figure 9, in the absorber 2 according to the present invention, a solenoid valve E can be provided on the piston P. For example, the top cover 71 can be made of a magnetic material, and a cable 9 from the vehicle body can be laid thereto to switch between energized and de-energized states, making it possible to switch between a state in which a magnetic force is generated and a state in which a magnetic force is not generated. On the other hand, the first valve 81 can also be made of a magnetic material, and when the top cover 71 is in an energized state, the top cover 71 and the first valve 81 are attracted to each other, preventing the valve from opening.

[0092] For example, when road conditions are recognized by an acceleration sensor (not shown) mounted on the vehicle, or when road conditions are known in advance by a position sensor or the like, the solenoid valve E is operated to actively adjust the flow rate of hydraulic oil in the first flow path W1 and the second flow path W2. This further reinforces the initial damping function set based on the inertial movement of the valve V, improving the ride comfort of the vehicle. Although not shown in FIG. 9, a similar configuration can be provided on the lower cover 72 to enable control of the second flow path W2 as well, thereby achieving a more precise damping function.

[0093] 9, the valve V can be made of a magnetic material and can be switched between an attracted state and a separated state relative to the upper cover 71 by energizing or de-energizing the upper cover 71. By adjusting the energizing voltage, etc., it is also possible to precisely determine the vertical position of the valve V. Even with this configuration, it is possible to control the flow rate of the hydraulic oil in the first flow path W1 and the second flow path W2, and the damping coefficient can be changed as desired. [Industrial Applicability]

[0094] The shock absorber of the present invention can be widely used in shock absorbers that have a cylinder connected to one of the suspension and the vehicle body, and a piston connected to the other to divide the internal space of the cylinder into a first chamber and a second chamber, and are equipped with a valve that can change the flow rate of a flow path formed in the piston to connect the first chamber and the second chamber. [Explanation of symbols]

[0095] 1P 1st port 1PH First Horizontal Groove 1PV 1st vertical groove 1s 1st opening 2 shock absorbers 2P 2nd port 2PH Second Horizontal Groove 2PV Second vertical groove 2s 2nd opening 3P 3rd port 3PH 3rd Yokogyo 3PV 3rd vertical groove 3s 3rd opening 4 cylinder 4P 4th port 4PH 4th horizontal groove 4PV 4th vertical groove 4s 4th opening 41 Wall 5 rods 6 cylinders E Solenoid Valve F. Biasing member P piston R1 Room 1 R2 2nd room sa communication path V-valve Vo throttle section W1 First flow path W2 Second flow path

Claims

1. A shock absorber used in a vehicle suspension that expands and contracts along an axis, a cylinder connected to either the suspension or the vehicle body; a piston that is fixed to a rod connected to either the suspension or the vehicle body and slides on an inner surface of the cylinder, dividing an internal space of the cylinder into a first chamber and a second chamber; the piston has a cylindrical body that slides on the inner surface of the cylinder, a valve that slides inside the cylindrical body in response to acceleration applied to the valve, and a biasing member that biases the valve to return to its basic position in the cylindrical body, a first flow path through which a fluid flows from the first chamber to the second chamber, and a second flow path through which the fluid flows from the second chamber to the first chamber, are formed by the cylindrical body and the valve; A shock absorber configured such that the cross-sectional areas of the first flow path and the second flow path change based on the relative positions of the cylindrical body and the valve.

2. the cylinder is connected to the suspension, the rod is connected to the vehicle body, the first chamber is provided on the suspension side with respect to the piston, and the second chamber is provided on the vehicle body side with respect to the piston, the first flow path includes a first port provided in a wall portion of the cylindrical body and communicating with the first chamber, and a second port communicating with the second chamber; the valve includes a first opening that can communicate with the first port, a second opening that can communicate with the second port, and a first communication passage that connects the first opening and the second opening, the second flow path includes a third port provided in a wall portion of the cylindrical body and communicating with the second chamber, and a fourth port communicating with the first chamber; the valve includes a third opening that is communicable with the third port, a fourth opening that is communicable with the fourth port, and a second communication passage that extends between the third opening and the fourth opening, 2. The shock absorber according to claim 1, wherein when the valve is in the basic position, the smaller of the communication area between the first port and the first opening and the communication area between the second port and the second opening, and the smaller of the communication area between the third port and the third opening and the communication area between the fourth port and the fourth opening, are maximized.

3. the first opening and the second opening have the same groove shape extending along the circumferential direction of the axis, the first port includes a first lateral groove provided elongated along the circumferential direction and a first longitudinal groove extending from a center position of the first lateral groove toward the first chamber; the second port includes a second lateral groove provided elongated along the circumferential direction and a second longitudinal groove extending from a center position of the second lateral groove toward the second chamber, The first transverse groove is formed to be longer than the second transverse groove, the first longitudinal groove and the second longitudinal groove have the same length along the direction in which the axis extends, and the width of the first longitudinal groove along the circumferential direction is narrower than the width of the second longitudinal groove, the third opening has the same shape as the first opening, the fourth opening has the same shape as the second opening, 3. The shock absorber according to claim 2, wherein the third port and the first port, and the fourth port and the second port, have the same shape, the third longitudinal groove of the third port extends from the third lateral groove toward the second chamber, and the fourth longitudinal groove of the fourth port extends from the fourth lateral groove toward the first chamber.

4. The internal space of the cylindrical body is filled with the fluid, 4. A shock absorber as described in any one of claims 1 to 3, wherein the valve divides the internal space into a first chamber and a second chamber along the extension direction of the axis, and has a through passage connecting the first chamber and the second chamber, and a throttle portion is formed in the through passage to restrict the flow rate of the fluid.

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