Damping valve and shock absorber

Abstract

To provide a damping valve capable of generating proper damping force with respect to input of vibration, and to provide a shock absorber capable of improving riding comfort in a vehicle.SOLUTION: A damping valve V includes a first passage P1 of which one end is communicated with one side room R2, a second passage P2 and a third passage P3 which are set in parallel and respectively communicate the other end of the first passage P1 with the other side room, a service valve element 1 which is provided on the first passage P1 and gives resistance to a stream flowing through the first passage P1, a bypass valve element 2 which is provided on the second passage P2 and gives a resistance to a stream of liquid flowing through the second passage P2, a pressure chamber C provided on the third passage P3, a free piston 3 which is stored movably within the pressure chamber C and divides the chamber into one side lateral pressure chamber c1 communicated with one side chamber R2 through the first passage P1 and an other side lateral pressure chamber c2 communicated with the other side chamber R1 via the third passage P3, and a spring element 4 generating energizing force which suppresses a deviation with respect to the pressure chamber C of the free piston 3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to improvements in damping valves and shock absorbers. [Background technology]

[0002] Shock absorbers installed between the body and axle of a vehicle generally exert a damping force with constant damping force characteristics to suppress vibration of the body. In recent years, however, in order to further improve the ride comfort of vehicles, shock absorbers equipped with damping valves that vary the damping force in response to the frequency or amplitude of the input vibration have been developed.

[0003] A shock absorber that changes the damping force in response to frequency includes, for example, a cylinder, a piston that is slidably inserted into the cylinder and divides the inside of the cylinder into an extension side chamber on the piston rod side and a compression side chamber on the piston side, and a damping valve provided on the piston.

[0004] The damping valve includes a main valve that communicates between the expansion-side chamber and the compression-side chamber to generate a damping force, and a frequency sensing portion.

[0005] The frequency sensitive part in the damping valve is configured to include a passage that bypasses the main valve and seemingly connects the expansion side chamber and the compression side chamber, a pressure chamber provided in the middle of the passage, a free piston that is slidably inserted into the pressure chamber and divides the pressure chamber into an expansion side pressure chamber and a compression side pressure chamber, and a coil spring that biases the free piston (see, for example, Patent Document 1).

[0006] In the frequency sensing part, the pressure chamber is divided into an extension side pressure chamber and a compression side pressure chamber by the free piston. When the free piston moves, the volume ratio of the extension side pressure chamber and the compression side pressure chamber changes. As a result, the hydraulic oil appears to bypass the main valve and travels between the extension side chamber and the compression side chamber, changing the flow rate of the hydraulic oil passing through the main valve.

[0007] A shock absorber equipped with such a frequency sensitive part generates a high damping force in response to low frequency vibration input, and on the other hand, exhibits a damping force reduction effect and generates a low damping force in response to high frequency vibration input, thereby improving the ride comfort in the vehicle. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2014-092181 A Summary of the Invention [Problem to be solved by the invention]

[0009] In conventional damping valves, simply bypassing the main valve at the frequency sensing section is not enough to accommodate a variety of vibration inputs, so a control valve is provided midway through the passage in the frequency sensing section.

[0010] However, conventional damping valves have a valve with a throttle passage provided in the frequency sensing section, and so the system generates damping force by selecting either the main valve or the control valve depending on the frequency of the shock absorber. Since only a small amount of hydraulic oil flows through the control valve when high-frequency vibration is input, the control valve cannot be fully utilized.

[0011] Therefore, there are cases where conventional damping valves are unable to exert an appropriate damping force against vibrations, and there is room for improvement in the ride comfort of the vehicle.

[0012] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a damping valve capable of generating an appropriate damping force in response to input of vibration, and a shock absorber capable of improving the ride comfort of a vehicle. [Means for solving the problem]

[0013] In order to achieve the above-mentioned object, the damping valve of the present invention comprises a first passage having one end connected to one chamber, a second passage and a third passage arranged in parallel to each other and connecting the other end of the first passage to the other chamber, a normal valve element provided in the first passage and providing resistance to the flow of liquid flowing through the first passage, a bypass valve element provided in the second passage and providing resistance to the flow of liquid flowing through the second passage, a pressure chamber provided in the third passage, a free piston movably accommodated in the pressure chamber and dividing the pressure chamber into a one-side pressure chamber connected to the one chamber through the first passage and a other-side pressure chamber connected to the other chamber through the third passage, and a spring element that generates a biasing force that suppresses displacement of the free piston with respect to the pressure chamber.

[0014] According to the damping valve configured in this manner, the entire amount of liquid always flows through the normal valve element, and the flow rate of liquid flowing through the bypass valve element and the pressure chamber varies according to the frequency or amplitude of the vibration of the shock absorber. Therefore, according to the shock absorber of this embodiment, unlike conventional damping valves and shock absorbers, a sufficient amount of liquid is passed through the normal valve element, making it possible to actively utilize the damping force characteristics of the normal valve element, so that when high-frequency vibration or small-amplitude vibration is input, the normal valve element can be fully utilized to exhibit damping force characteristics suitable for the vibration, thereby improving the ride comfort of the vehicle.

[0015] In addition, the normal valve element in the damping valve may be configured to provide greater resistance to the flow of liquid than the bypass valve element when a flow rate of liquid less than a predetermined flow rate is passing through, and to provide less resistance to the flow of liquid than the bypass valve element when a flow rate of liquid greater than the predetermined flow rate is passing through.

[0016] With a damping valve configured in this manner, the damping force characteristics of the normal valve element are adapted to be suitable for suppressing vibrations that are input when high-frequency, small-amplitude vibrations are input or when the vehicle is traveling on a relatively smooth road surface, and the damping force characteristics of the bypass valve element are adapted to be suitable for suppressing large-amplitude, low-frequency vibrations, thereby improving the ride comfort of the vehicle.

[0017] Furthermore, the normal valve element may have a valve body that is annular and has one of the inner and outer circumferential sides as a fixed end and the other as a free end, and an annular opposing seat that radially faces the free end of the valve body, and the bypass valve element may have a bypass valve on one side that provides resistance to the flow of liquid from one chamber to the other chamber and has a higher valve opening pressure than the normal valve element, a bypass valve on the other side that provides resistance to the flow of liquid from the other chamber to the one chamber and has a higher valve opening pressure than the normal valve element, and an orifice that provides resistance to the flow of liquid traveling between the one chamber and the other chamber.

[0018] According to the damping valve configured in this manner, a single valve body can exert a damping force while allowing the liquid to flow in both directions between the one chamber and the other chamber, it is compact and easy to apply to a shock absorber, the annular gap between the valve body and the annular opposing seat is made extremely small, so that the damping force can be raised at the beginning of the expansion / contraction of the shock absorber regardless of the frequency or the amplitude of the vibration, thereby improving the ride comfort of the vehicle, when the shock absorber vibrates at a low frequency or large amplitude and the expansion / contraction speed becomes high, the vibration can be suppressed by the bypass valve on one side or the bypass valve on the other side suitable for suppressing the vibration at high speed, so that even if the vibration becomes large, a corresponding damping force can be generated and the ride comfort of the vehicle can be improved. Also, when the shock absorber vibrates at a high frequency or small amplitude, when the expansion / contraction speed of the shock absorber becomes high speed, the valve body does not bend significantly and the damping force does not become excessively high, so that the effect of reducing the damping force using the third passage when high frequency or small amplitude vibration is input is not lost.

[0019] In addition, the shock absorber of the present invention includes a cylinder, a piston slidably inserted into the cylinder to divide the inside of the cylinder into an extension side chamber and a compression side chamber, a piston rod movably inserted into the cylinder and one end connected to the piston, and a damping valve.

[0020] According to a shock absorber configured in this manner, unlike conventional shock absorbers, a sufficient amount of liquid can be passed through the normal valve element, making active use of the damping force characteristics of the normal valve element. Therefore, when high-frequency vibrations or small-amplitude vibrations are input, the normal valve element can be fully utilized to exhibit damping force characteristics suited to the vibrations, thereby improving the ride comfort of the vehicle.

[0021] Furthermore, in the shock absorber, the normal valve element in the damping valve may provide higher resistance to the flow of liquid passing therethrough than the bypass valve element when the moving speed of the piston relative to the cylinder is in the extremely low speed range, and may provide lower resistance than the bypass valve element when the moving speed of the piston relative to the cylinder exceeds the extremely low speed range.

[0022] With a shock absorber configured in this manner, the damping force characteristics of the normal valve element are suitable for suppressing high-frequency, small-amplitude vibrations or vibrations that are input when the vehicle is running on a relatively smooth road surface, and the damping force characteristics of the bypass valve element are suitable for suppressing large-amplitude, low-frequency vibrations, thereby improving the ride comfort of the vehicle. Effect of the Invention

[0023] Therefore, the shock absorber of the present invention provides a damping valve that can generate an appropriate damping force in response to input of vibration, and improves the ride comfort of the vehicle. [Brief description of the drawings]

[0024] [Figure 1] 1 is a vertical sectional view of a shock absorber including a damping valve according to an embodiment of the present invention; [Diagram 2] FIG. 2 is an enlarged vertical cross-sectional view of a damping valve according to one embodiment of the present invention. [Diagram 3] FIG. 2 is an enlarged vertical cross-sectional view of a first example of a specific damping valve. [Figure 4] 11 is a diagram showing the damping force characteristics of a shock absorber having a specific damping valve during low-frequency vibration. FIG. [Diagram 5]FIG. 11 is an enlarged vertical cross-sectional view of a second example of a specific damping valve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The present invention will be described below with reference to the drawings. A damping valve V according to an embodiment of the present invention includes a first passage P1, a second passage P2 and a third passage P3 connected in parallel to the first passage P1, a normal valve element 1 provided in the first passage P1, a bypass valve element 2 provided in the second passage P2, a pressure chamber C provided in the third passage P3, a free piston 3 accommodated in the pressure chamber C, and a spring element 4 for biasing the free piston 3, and is applied to a shock absorber D.

[0026] The damping valve V and the shock absorber D will be described in detail below. First, as shown in Fig. 1, the shock absorber D includes a cylinder 10 as an outer tube, a piston 11 slidably inserted into the cylinder 10 and dividing the inside of the cylinder 10 into an expansion-side chamber R1 and a compression-side chamber R2, a piston rod 12 movably inserted into the cylinder 10 and one end connected to the piston 11, and a damping valve V, and is interposed between the body and the wheels of a vehicle (not shown) to suppress vibration of the vehicle body by the damping force generated by the damping valve V during expansion and contraction.

[0027] The cylinder 10 is a cylindrical shape with a bottom, and a sliding partition 13 is slidably inserted inside the cylinder 10 together with the piston 11. The sliding partition 13 divides the inside of the cylinder 10 into a liquid chamber L filled with liquid and an air chamber G filled with gas, and the piston 11 divides the liquid chamber L in the cylinder 10 into an extension-side chamber R1 and a compression-side chamber R2.

[0028] The piston rod 12 is inserted into the cylinder 10 so as to be movable in the axial direction, with its tip (lower end in Fig. 1) connected to the piston 11 and its base (upper end in Fig. 1) protruding outside the cylinder 10. The gap between the piston rod 12 and the cylinder 10 is sealed by a sealing member (not shown), preventing the liquid in the cylinder 10 from leaking outward.

[0029] In the illustrated example, the shock absorber D is a so-called single-rod type mono-tube shock absorber in which the piston rod 12 penetrates only the extension-side chamber R1, so that the volume of the piston rod 12 moving in and out of the cylinder 10 with the expansion and contraction of the shock absorber D is compensated by the expansion or contraction of the volume of the gas in the air chamber G, and the sliding partition wall 13 moves in the vertical direction in FIG. 1. In this way, the shock absorber D is a mono-tube shock absorber, but instead of providing the air chamber G in the cylinder 10 by providing the sliding partition wall 13 in the cylinder 10, a reservoir may be provided on the outer periphery or outside of the cylinder 10 to compensate the volume of the piston rod 12 by the reservoir. In addition, the shock absorber D may be set as a double-rod type shock absorber instead of a single-rod type shock absorber. In addition, instead of being partitioned by the sliding partition wall 13 housed in the cylinder 10, the air chamber G may be partitioned by an elastic partition wall such as a diaphragm.

[0030] In this embodiment, a damping valve V is provided in the piston 11 and the piston rod 12. The damping valve V is provided in the piston 11, with one chamber serving as a compression side chamber R2 and the other chamber serving as an expansion side chamber R1. More specifically, the damping valve V includes a first passage P1 having one end communicated with the compression side chamber R2 as one chamber, a second passage P2 and a third passage P3 arranged in parallel with each other and communicating the other end of the first passage P1 with the expansion side chamber R1 as the other chamber, a normal valve element 1 provided in the first passage P1 and providing resistance to the flow of liquid flowing through the first passage P1, a bypass valve element 2 provided in the second passage P2 and providing resistance to the flow of liquid flowing through the second passage P2, a pressure chamber C provided in the third passage P3, a free piston 3 movably accommodated in the pressure chamber C and dividing the pressure chamber C into a one-side pressure chamber c1 communicated with the compression side chamber R2 through the first passage P1 and an other-side pressure chamber c2 communicated with the expansion side chamber R1 through the third passage P3, and a spring element 4 generating a biasing force that suppresses displacement of the free piston 3 with respect to the pressure chamber C.

[0031] The first passage P1 opens from the lower end of the piston 11 in FIG. 1 and is connected to the compression-side chamber R2 as one of the chambers. The other end of the first passage P1 opens from the upper end of the piston 11 in FIG. 1 and is connected to the expansion-side chamber R1 as the other chamber. The other end of the first passage P1 is connected to a second passage P2 which opens from the upper end of the piston 11 in FIG. 1 and is connected to the expansion-side chamber R1 as the other chamber, and a third passage P3 which opens from a side portion of the piston rod 12 facing the expansion-side chamber R1 and is connected to the expansion-side chamber R1 as the other chamber.

[0032] The first passage P1 is provided with a normal valve element 1. The normal valve element 1 includes an extension side damping valve 1a and a compression side damping valve 1b that are arranged in parallel with each other in the first passage P1. The extension side damping valve 1a provides resistance to the flow of liquid from the extension side chamber R1 to the compression side chamber R2 through the first passage P1, but prevents the flow of liquid in the opposite direction. On the other hand, the compression side damping valve 1b provides resistance to the flow of liquid from the compression side chamber R2 to the extension side chamber R1 through the first passage P1, but prevents the flow of liquid in the opposite direction. The extension side damping valve 1a and the compression side damping valve 1b may be configured as leaf valves that have elasticity and are seated on and separated from a valve seat, but may also be configured as leaf valves that are seated on and separated from a valve seat and a spring that biases the leaf valve toward the valve seat, or may be configured as valves having a valve body other than a leaf valve. As described above, the normal valve element 1 is configured with the extension side damping valve 1a and the compression side damping valve 1b in parallel, but other than this configuration, for example, the normal valve element 1 may be configured with an orifice or a choke that allows the flow of liquid in both directions and provides resistance to the flow of liquid, or other configurations may be adopted. Also, since the first passage P1 only needs to be connected to the compression side chamber R2, the second passage P2, and the third passage P3, it may be provided in the piston rod 12 other than the piston 11.

[0033] The second passage P2 is provided with a bypass valve element 2. The bypass valve element 2 includes an expansion side bypass damping valve 2a, a compression side bypass damping valve 2b, and an orifice 2c, which are arranged in parallel with each other in the second passage P2. The expansion side bypass damping valve 2a provides resistance to the flow of liquid from the expansion side chamber R1 to the compression side chamber R2 through the second passage P2, but prevents the flow of liquid in the opposite direction. On the other hand, the compression side bypass damping valve 2b provides resistance to the flow of liquid from the compression side chamber R2 to the expansion side chamber R1 through the second passage P2, but prevents the flow of liquid in the opposite direction. Furthermore, the orifice 2c provides resistance to the flow of liquid while allowing the flow of liquid from the expansion side chamber R1 to the compression side chamber R2 and from the compression side chamber R2 to the expansion side chamber R1 through the second passage P2. The extension side bypass damping valve 2a and the compression side bypass damping valve 2b may be configured as leaf valves that have elasticity and move on and off the valve seat, but may also be configured as leaf valves that move on and off the valve seat and springs that urge the leaf valves toward the valve seat, or may be configured as valves having valve bodies other than leaf valves. As described above, the bypass valve element 2 is configured by arranging the extension side bypass damping valve 2a, the compression side bypass damping valve 2b, and the orifice 2c in parallel, but other configurations may be used, for example, a choke may be provided instead of the orifice 2c, or the extension side bypass damping valve 2a and the compression side bypass damping valve 2b may be eliminated and the orifice 2c may be only provided, or other configurations may be adopted. As long as the second passage P2 is connected to the extension side chamber R1 and the first passage P1, it may be provided in the piston rod 12 instead of the piston 11.

[0034] A pressure chamber C is provided in the middle of the third passage P3. In this embodiment, the pressure chamber C is provided in the piston rod 12, but may be provided in the piston 11. A free piston 3 is inserted into the pressure chamber C so as to be movable in the vertical direction in FIG. 1 relative to the piston rod 12. The free piston 3 divides the pressure chamber C into a one-side pressure chamber c1 on the lower side in FIG. 1 and a other-side pressure chamber c2 on the upper side in FIG. 1. The one-side pressure chamber c1 is communicated with the compression-side chamber R2 through the first passage P1 connected to the lower end of the third passage P3, and the other-side pressure chamber c2 is communicated with the expansion-side chamber R1 through a portion of the third passage P3 that is above the pressure chamber C in FIG. 1.

[0035] Therefore, when the free piston 3 is displaced in the pressure chamber C, the volume of one of the one-side pressure chamber c1 and the other-side pressure chamber c2 decreases, and the volume of the other of the one-side pressure chamber c1 and the other-side pressure chamber c2 increases by the amount of the decrease. Therefore, when the free piston 3 is displaced upward in Fig. 1 in the pressure chamber C, the liquid in the compression-side chamber R2 as one chamber apparently moves to the expansion-side chamber R1 as the other chamber via the pressure chamber C in the third passage P3, and when the free piston 3 is displaced downward in Fig. 1 in the pressure chamber C, the liquid in the expansion-side chamber R1 as the other chamber apparently moves to the compression-side chamber R2 as one chamber via the pressure chamber C in the third passage P3.

[0036] The free piston 3 is connected to one end of a spring element 4, the other end of which is connected to the piston rod 12 and housed in one pressure chamber c1. The spring element 4 positions the free piston 3 at a predetermined neutral position in the pressure chamber C, and exerts a biasing force to return the free piston 3 to the neutral position when the free piston 3 is displaced from the neutral position. The neutral position of the free piston 3 is a position at which the free piston 3 is positioned with respect to the pressure chamber C by the spring element 4, and in this embodiment, it is set to the center of the range in which the free piston 3 can stroke in the pressure chamber C, that is, the stroke center, but it does not necessarily have to be set to the stroke center.

[0037] The spring element 4 may be housed in the other side pressure chamber c2, or may be composed of two springs housed in the one side pressure chamber c1 and the other side pressure chamber c2, respectively, and the configuration can be designed and modified as desired as long as it can position the free piston 3 in a neutral position and generate a spring force in a direction returning it to the neutral position when it is displaced from the neutral position.

[0038] The direction of displacement of the free piston 3 coincides with the direction of vibration that the shock absorber D suppresses by expanding and contracting. In order to avoid the upward and downward vibration of the free piston 3 being excited by the entire shock absorber D vibrating in the upward and downward direction in Figure 1, the direction of movement of the free piston 3 may be set perpendicular to the direction of expansion and contraction of the shock absorber D.

[0039] In this embodiment, the third passage P3 is provided with a throttle 5 that is arranged in series with the pressure chamber C, and is capable of providing resistance to the flow of liquid passing therethrough. Although the throttle 5 is considered to be the conduit resistance of the third passage P3 itself, it may be an orifice or a choke, or it may be a variable throttle.

[0040] Next, the operation of the damping valve V and the shock absorber D will be described. When the piston 11 moves up and down in FIG. 1 relative to the cylinder 10 and the shock absorber D performs an expansion / contraction operation, one of the expansion-side chamber R1 and the compression-side chamber R2 is compressed by the piston 11 and the other of the expansion-side chamber R1 and the compression-side chamber R2 is expanded, so that the pressure of the expansion-side chamber R1 or the compression-side chamber R2 that is compressed increases, and at the same time, the pressure of the expansion-side chamber R1 or the compression-side chamber R2 that is expanded decreases, generating a pressure difference between the two.

[0041] When the shock absorber D is expanded, the liquid in the expansion-side chamber R1 is compressed and moves to the compression-side chamber R2 through an apparent passage that includes the expansion-side damping valve 1a in the first passage P1, the expansion-side bypass damping valve 2a and the orifice 2c in the second passage P2, and in addition, the third passage P3 and the pressure chamber C.

[0042] On the other hand, when the shock absorber D is contracting, the liquid in the compression-side chamber R2 being compressed moves to the expansion-side chamber R1 through an apparent passage that is made up of the compression-side damping valve 1b in the first passage P1, the compression-side bypass damping valve 2b and the orifice 2c in the second passage P2, and in addition, the third passage P3 and the pressure chamber C.

[0043] Here, whether the frequency of the vibration input to the shock absorber D, i.e., the frequency of the vibration in the expansion / contraction direction of the shock absorber D, is low frequency or high frequency, when the piston speed in the expansion stroke of the shock absorber D is the same, the amplitude of the shock absorber D when the low frequency vibration is input is larger than the amplitude of the shock absorber D when the high frequency vibration is input. In this way, when the frequency of the vibration input to the shock absorber D is low, the amplitude is large, so the flow rate of the liquid that moves between the expansion-side chamber R1 and the contraction-side chamber R2 in one expansion / contraction cycle is large. The displacement of the free piston 3 also increases in proportion to this flow rate, but since the free piston 3 is biased by the spring element 4, when the displacement of the free piston 3 increases, the biasing force from the spring element 4 that the free piston 3 receives also increases, and accordingly, a pressure difference occurs between the pressure of the one-side pressure chamber c1 and the pressure of the other-side pressure chamber c2, and the pressure difference between the pressure of the contraction-side chamber R2 and the one-side pressure chamber c1 and the pressure difference between the expansion-side chamber R1 and the other-side pressure chamber c2 become smaller, and the flow rate passing through the above-mentioned apparent passage becomes smaller. Since the flow rate of the liquid passing through this apparent passage is small, the flow rate of the liquid passing through the second passage P2 is large.

[0044] Conversely, when high-frequency vibration is input to the shock absorber D, the amplitude is smaller than that when low-frequency vibration is input, so the flow rate of the liquid passing between the expansion-side chamber R1 and the contraction-side chamber R2 in one period of expansion and contraction is small, and the displacement of the free piston 3 is also small. Then, the biasing force from the spring element 4 that the free piston 3 receives is also small. Accordingly, the pressure in the one-side pressure chamber c1 and the pressure in the other-side pressure chamber c2 become almost equal, and the pressure difference between the contraction-side chamber R2 and the one-side pressure chamber c1 and the pressure difference between the expansion-side chamber R1 and the other-side pressure chamber c2 become larger than that when low-frequency vibration is input, and the flow rate passing through the apparent passage is larger than that when low-frequency vibration is input. Therefore, when high-frequency vibration is input, the flow rate passing through the apparent passage is larger than the flow rate through the second passage P2, so that more liquid passes through the third passage P3.

[0045] In this way, when the shock absorber D expands and contracts at a low frequency, the amount of liquid passing through the second passage P2 is relatively greater than the amount of liquid passing through the third passage P3, and when the shock absorber D expands and contracts at a high frequency, the amount of liquid passing through the second passage P2 is relatively less than the amount of liquid passing through the third passage P3.

[0046] Since the first passage P1 is connected in series to the second passage P2 and the third passage P3 which are connected in parallel, the total flow rate of the liquid passing between the compression side chamber R2 and the extension side chamber R1 flows regardless of the frequency of expansion and contraction of the shock absorber D.

[0047] Therefore, during the extension operation of the shock absorber D, all of the liquid flowing from the extension side chamber R1 to the compression side chamber R2 passes through the extension side damping valve 1a in the normal valve element 1, and when the vibration frequency of the shock absorber D is low, the amount of liquid passing through the extension side bypass damping valve 2a and the orifice 2c becomes greater than the amount of liquid passing through the third passage P3, so that the shock absorber D mainly provides resistance to the flow of liquid from the extension side chamber R1 to the compression side chamber R2 by the extension side damping valve 1a, and the extension side bypass damping valve 2a and the orifice 2c connected in series with the extension side damping valve 1a. On the other hand, during the extension operation of the shock absorber D, when the vibration frequency of the shock absorber D is high, the amount of liquid passing through the third passage P3 becomes greater and the amount of liquid passing through the extension side bypass damping valve 2a and the orifice 2c becomes smaller, so that the shock absorber D mainly provides resistance to the flow of liquid from the extension side chamber R1 to the compression side chamber R2 by the extension side damping valve 1a.

[0048] As described above, when the shock absorber D is in an extension operation and the vibration frequency of the shock absorber D is low, a high damping force is generated, and when the shock absorber D is in an extension operation and the vibration frequency of the shock absorber D is high, the liquid bypasses the extension-side bypass damping valve 2a and the orifice 2c and passes through the third passage P3, so that a low damping force is generated compared to the case of the low frequency.

[0049] Also, during contraction of the shock absorber D, all of the liquid flowing from the compression side chamber R2 to the expansion side chamber R1 passes through the compression side damping valve 1b in the normal valve element 1, and when the vibration frequency of the shock absorber D is low, the amount of liquid passing through the compression side bypass damping valve 2b and the orifice 2c becomes greater than the amount of liquid passing through the third passage P3, so that the shock absorber D mainly provides resistance to the flow of liquid from the compression side chamber R2 to the expansion side chamber R1 by the compression side damping valve 1b, and the compression side bypass damping valve 2b and the orifice 2c connected in series with the compression side damping valve 1b. On the other hand, during contraction of the shock absorber D, when the vibration frequency of the shock absorber D is high, the amount of liquid passing through the third passage P3 becomes greater and the amount of liquid passing through the compression side bypass damping valve 2b and the orifice 2c becomes smaller, so that the shock absorber D mainly provides resistance to the flow of liquid from the compression side chamber R2 to the expansion side chamber R1 by the compression side damping valve 1b.

[0050] As described above, when the shock absorber D is in a contracting operation and the vibration frequency of the shock absorber D is low, a high damping force is generated, and when the shock absorber D is in a contracting operation and the vibration frequency of the shock absorber D is high, a low damping force is generated compared to the case of a low frequency because the liquid bypasses the compression side bypass damping valve 2b and the orifice 2c and passes through the third passage P3.

[0051] Therefore, the shock absorber D can reduce the damping force depending on the frequency of the input vibration, and generates a high damping force when the input vibration frequency is low, and generates a low damping force when the input vibration frequency is high. Therefore, the shock absorber D generates a high damping force for the input of vibration in a low sprung resonance frequency band, stabilizing the vehicle posture and preventing the passenger from feeling uneasy when the vehicle turns. Furthermore, the shock absorber D always generates a low damping force when vibration in a high unsprung resonance frequency band is input, insulating the transmission of the vibration on the axle side to the vehicle body side, and improving the ride comfort in the vehicle. In addition, the pressure chamber C functions as an apparent passage when the shock absorber D expands and contracts at a frequency equal to or higher than a predetermined frequency, and the predetermined frequency can be set arbitrarily by the spring constant of the spring element 4, the resistance of the throttle 5, the pressure-receiving area of ​​the free piston 3, and the like, as disclosed in JP 2006-336816 A.

[0052] In addition, if the resistance that the third passage P3 provides to the flow of liquid is minimized, that is, if the throttle 5 is eliminated or the resistance of the throttle 5 is minimized, the liquid will pass through the third passage P3 more easily than through the second passage P2. Then, in a range where the amplitude of vibration of the shock absorber D is small and the free piston 3 does not reach the stroke end in the pressure chamber C, the free piston 3 can move freely in the pressure chamber C and can move between the expansion-side chamber R1 and the compression-side chamber R2 via the apparent passage, bypassing the bypass valve element 2, and the damping force generated by the shock absorber D is reduced. On the other hand, if the amplitude of vibration of the shock absorber D is large and the free piston 3 reaches the stroke end in the pressure chamber C, the movement of the free piston 3 in the same direction is restricted unless the expansion / contraction direction of the shock absorber D is switched, and the free piston 3 cannot move between the expansion-side chamber R1 and the compression-side chamber R2 via the apparent passage, and the shock absorber D generates a high damping force by the normal valve element 1 and the bypass valve element 2. In this way, by minimizing the resistance that the third passage P3 provides to the flow of liquid, the shock absorber D changes its damping force in response to the amplitude of the input vibration rather than its frequency, generating a low damping force for input of small amplitude vibration to insulate the transmission of vibration from the axle side to the vehicle body, and generating a high damping force for input of large amplitude vibration to suppress vibration of the vehicle body, thereby improving the ride comfort of the vehicle. The amplitude of vibration in the shock absorber D at which the liquid passes through the bypass valve element 2 can be set by the volumes of the one-side pressure chamber c1 and the other-side pressure chamber c2 when the free piston 3 is in the neutral position.

[0053] In this way, when the shock absorber D expands or contracts, the entire amount of liquid always flows through the normal valve element 1, and the flow rate of liquid flowing through the bypass valve element 2 and the pressure chamber C varies depending on the frequency or amplitude of the vibration of the shock absorber D. Therefore, the damping force characteristics of the shock absorber D in this embodiment are a superposition of the damping force characteristics of the normal valve element 1 and the damping force characteristics of the bypass valve element 2 when the input vibration has a low frequency or a large amplitude, and are the damping force characteristics of the normal valve element 1 when the input vibration has a high frequency or a small amplitude.

[0054] Therefore, unlike conventional damping valves and buffer devices, a sufficient amount of liquid can be passed through the normal valve element 1, making active use of the damping force characteristics of the normal valve element 1. Therefore, in the damping valve V and buffer device D of this embodiment, when high-frequency vibrations or small-amplitude vibrations are input, the normal valve element 1 can be fully utilized to exhibit damping force characteristics suitable for that vibration.

[0055] In addition, the damping force characteristics of the damping valve V and the shock absorber D can be tuned by combining the characteristics of the normal valve element 1 and the bypass valve element 2. For example, the normal valve element 1 can be set to provide greater resistance to the flow of liquid than the bypass valve element 2 when the liquid passes through at a flow rate less than a predetermined flow rate, and to provide less resistance to the flow of liquid than the bypass valve element 2 when the liquid passes through at a flow rate more than the predetermined flow rate.

[0056] In this case, the situation where the flow rate through the normal valve element 1 is low is the situation where the shock absorber D expands and contracts slowly, and under such a situation, the normal valve element 1 provides a larger resistance to the flow of liquid than the bypass valve element 2. In this way, the flow rate passing through the normal valve element 1 is proportional to the expansion / contraction speed of the shock absorber D. Therefore, when the shock absorber D starts to expand or contracts or when the expansion / contraction speed is extremely slow, the damping valve V generates a damping force by the normal valve element 1, and the shock absorber D can generate a damping force that suppresses the expansion / contraction of the shock absorber D even when it starts to expand or contract. In addition, when the shock absorber D is sensitive to the frequency of the input vibration, even if the frequency of the vibration input to the shock absorber D is low, the bypass valve element 2 can generate a large damping force when the piston speed is in a speed range exceeding the extremely low speed range, and the bypass valve element 2 can generate a damping force for the input of vibration with a large amplitude and low frequency. Furthermore, the shock absorber D can generate a damping force by the normal valve element 1 when a vibration with a high frequency and small amplitude is input, or when the vehicle is running on a relatively smooth road surface. When the shock absorber D is sensitive to the amplitude of the input vibration, if the vibration input to the shock absorber D is large and the piston speed is in a speed range exceeding the extremely low speed range, a large damping force can be generated by the bypass valve element 2, and for input of vibration with large amplitude, a damping force can be generated by the bypass valve element 2. Furthermore, when small, pulsating vibrations are input, or when the vehicle is running on a relatively smooth road surface, the shock absorber D can generate a damping force by the normal valve element 1.

[0057] From the above, if the normal valve element 1 is set so as to provide a greater resistance to the flow of liquid than the bypass valve element 2 when the liquid passes through at a flow rate less than the predetermined flow rate, and to provide a smaller resistance to the flow of liquid than the bypass valve element 2 when the liquid passes through at a flow rate greater than the predetermined flow rate, the damping force characteristics of the normal valve element 1 can be made suitable for suppressing vibrations input when high-frequency, small-amplitude vibrations are input or when the vehicle is running on a relatively smooth road surface, and the damping force characteristics of the bypass valve element 2 can be made suitable for suppressing vibrations with large amplitude and low frequency, thereby improving the ride comfort of the vehicle. Note that the predetermined flow rate can be set arbitrarily, but it is preferable to set it to a flow rate on the boundary between the flow rate region where it is desired to utilize the damping force characteristics of the normal valve element 1 and the flow rate region where it is desired to utilize the damping force characteristics of the bypass valve element 2.

[0058] Furthermore, the normal valve element 1 can be set to provide higher resistance to the flow of liquid passing through it than the bypass valve element 2 when the moving speed of the piston 11 relative to the cylinder 10 is in the extremely low speed range, and to provide lower resistance than the bypass valve element 2 when the moving speed of the piston 11 relative to the cylinder 10 exceeds the extremely low speed range.

[0059] In this case, the situation where the flow rate through the normal valve element 1 is small is the situation where the shock absorber D expands and contracts slowly, and under such a situation, the normal valve element 1 provides a larger resistance to the flow of liquid than the bypass valve element 2. Therefore, when the shock absorber D starts to expand or contract, or when the expansion and contraction speed is extremely slow, the damping valve V generates a damping force by the normal valve element 1, and the shock absorber D can generate a damping force that suppresses the expansion and contraction of the shock absorber D even when it starts to expand or contract. In addition, when the shock absorber D is sensitive to the frequency of the input vibration, even if the frequency of the vibration input to the shock absorber D is low, the bypass valve element 2 can generate a large damping force when the piston speed is in a speed range exceeding the extremely low speed range, and the bypass valve element 2 can generate a damping force for the input of vibration with a large amplitude and low frequency. Furthermore, the shock absorber D can generate a damping force by the normal valve element 1 when a vibration with a high frequency and small amplitude is input, or when the vehicle is running on a relatively smooth road surface, etc. When the shock absorber D is sensitive to the amplitude of the input vibration, if the vibration input to the shock absorber D is large and the piston speed is in a speed range exceeding the extremely low speed range, a large damping force can be generated by the bypass valve element 2, and for input of vibration with large amplitude, a damping force can be generated by the bypass valve element 2. Furthermore, when small, pulsating vibrations are input, or when the vehicle is running on a relatively smooth road surface, the shock absorber D can generate a damping force by the normal valve element 1.

[0060] From the above, even if the normal valve element 1 is set so that it provides a higher resistance to the flow of liquid passing through it than the bypass valve element 2 when the moving speed of the piston 11 relative to the cylinder 10 is in the extremely low speed range, and so that it provides a lower resistance than the bypass valve element 2 when the moving speed of the piston 11 relative to the cylinder 10 exceeds the extremely low speed range, the ride comfort of the vehicle can be improved by making the damping force characteristics of the normal valve element 1 suitable for suppressing vibrations that are input when high-frequency, small-amplitude vibrations are input or when the vehicle is running on a relatively smooth road surface, and by making the damping force characteristics of the bypass valve element 2 suitable for suppressing large-amplitude, low-frequency vibrations.

[0061] The normal valve element 1 and the bypass valve element 2 may be set to have the same damping force characteristics. In this case, the bypass valve element 2 may be set to exert a damping force only when the vehicle vibrates with a large amplitude, and the normal valve element 1 may be set to generate a damping force only when the vehicle is normally traveling on a good road, so that the bypass valve element 2 may generate a damping force in addition to the normal valve element 1 when a large amplitude vibration is input during traveling on a bad road or the like. In this case, the normal valve element 1 and the bypass valve element 2 generate a damping force in response to a vibration input that causes the shock absorber D to be fully extended or fully contracted, so that the vibration of the vehicle body can be suppressed even for a large input vibration, and the vibration can be suppressed by the normal valve element 1 that is set to be suitable for suppressing vibration during normal traveling, thereby improving the ride comfort of the vehicle.

[0062] As described above, the damping valve V of this embodiment includes the first passage P1, one end of which is connected to the compression side chamber (one chamber) R2, the second passage P2 and the third passage P3, which are arranged in parallel with each other and each connect the other end of the first passage P1 to the extension side chamber (other chamber) R1, the normal valve element 1 provided in the first passage P1 and providing resistance to the flow of liquid flowing through the first passage P1, the bypass valve element 2 provided in the second passage P2 and providing resistance to the flow of liquid flowing through the second passage P2, the pressure chamber C provided in the third passage P3, the free piston 3 movably accommodated in the pressure chamber C and dividing the pressure chamber C into a one-side pressure chamber c1 connected to the compression side chamber (one chamber) R2 through the first passage P1 and a other-side pressure chamber c2 connected to the extension side chamber (other chamber) R1 through the third passage P3, and the spring element 4 generating a biasing force that suppresses displacement of the free piston 3 with respect to the pressure chamber C.

[0063] With the damping valve V configured in this manner, the entire amount of liquid always flows through the normal valve element 1, and the flow rate of liquid flowing through the bypass valve element 2 and the pressure chamber C varies depending on the frequency or amplitude of the vibration of the shock absorber D. Thus, with the shock absorber D of this embodiment, unlike conventional damping valves and shock absorbers, a sufficient amount of liquid is allowed to pass through the normal valve element 1, making it possible to actively utilize the damping force characteristics of the normal valve element 1, so that when high-frequency vibration or small-amplitude vibration is input, the normal valve element 1 can be fully utilized to exhibit damping force characteristics suited to that vibration, and the ride comfort of the vehicle can be improved.

[0064] Furthermore, the normal valve element 1 in the damping valve V of this embodiment may be set to provide greater resistance to the flow of liquid than the bypass valve element 2 when the liquid passes through at a flow rate less than a predetermined flow rate, and to provide less resistance to the flow of liquid than the bypass valve element 2 when the liquid passes through at a flow rate greater than the predetermined flow rate. According to the damping valve V configured in this manner, the damping force characteristics of the normal valve element 1 are adapted to suppress vibrations input when high-frequency, small-amplitude vibrations are input or when the vehicle is traveling on a relatively smooth road surface, and the damping force characteristics of the bypass valve element 2 are adapted to suppress vibrations with large amplitudes and low frequencies, thereby improving the ride comfort of the vehicle.

[0065] Furthermore, the shock absorber D of this embodiment includes a cylinder 10, a piston 11 slidably inserted into the cylinder 10 and dividing the inside of the cylinder 10 into an expansion-side chamber R1 and a compression-side chamber R2, a piston rod 12 movably inserted into the cylinder 10 and one end connected to the piston 11, and a damping valve V, with one chamber being the compression-side chamber R2 and the other chamber being the expansion-side chamber R1.

[0066] According to the shock absorber D configured as described above, unlike the conventional shock absorber, a sufficient amount of liquid is passed through the normal valve element 1, and the damping force characteristics of the normal valve element 1 can be actively utilized. Therefore, when high-frequency vibration or small-amplitude vibration is input, the normal valve element 1 can be fully utilized to exhibit damping force characteristics suitable for the vibration, and the ride comfort of the vehicle can be improved. In the shock absorber D of this embodiment, one chamber is the compression side chamber R2 and the other chamber is the expansion side chamber R1, but conversely, one chamber may be the expansion side chamber R1 and the other chamber may be the compression side chamber R2. In addition to being applied to the piston part of the shock absorber D, when the shock absorber D has a reservoir, the damping valve V may be either one of the compression side chamber R2 or the reservoir, and the other chamber may be either the compression side chamber R2 or the reservoir.

[0067] Furthermore, the normal valve element 1 in the damping valve V in the shock absorber D of this embodiment may be set to provide a higher resistance to the flow of liquid passing therethrough than the bypass valve element 2 when the moving speed of the piston 11 relative to the cylinder 10 is in the extremely low speed range, and to provide a lower resistance than the bypass valve element 2 when the moving speed of the piston 11 relative to the cylinder 10 exceeds the extremely low speed range. According to the shock absorber D configured in this manner, the damping force characteristics of the normal valve element 1 are adapted to suppress vibrations input when high-frequency, small-amplitude vibrations are input or when the vehicle is traveling on a relatively smooth road surface, and the damping force characteristics of the bypass valve element 2 are adapted to suppress vibrations with large amplitudes and low frequencies, thereby improving the ride comfort of the vehicle.

[0068] The structure of the shock absorber D has been conceptually explained above, but an example of a shock absorber D1 with a more specific structure will be explained below. As shown in Figures 2 and 3, the shock absorber D1 includes a cylinder 20 as an outer tube, a piston 21 slidably inserted into the cylinder 20 and dividing the inside of the cylinder 20 into an expansion-side chamber R1 and a compression-side chamber R2, a piston rod 22 movably inserted into the cylinder 20 and one end connected to the piston 21, and a damping valve V1, and is interposed between the body and the wheels of a vehicle (not shown) to suppress vibration of the vehicle body with the damping force generated by the damping valve V1 during expansion and contraction.

[0069] The damping valve V1 is applied to a shock absorber D1, with one chamber serving as a compression-side chamber R2 and the other chamber serving as an expansion-side chamber R1. More specifically, the damping valve V includes a first passage P1 having one end communicated with the compression side chamber R2 as one chamber, a second passage P2 and a third passage P3 arranged in parallel with each other and communicating the other end of the first passage P1 with the expansion side chamber R1 as the other chamber, a normal valve element 35 provided in the first passage P1 and providing resistance to the flow of liquid flowing through the first passage P1, a bypass valve element 40 provided in the second passage P2 and providing resistance to the flow of liquid flowing through the second passage P2, a pressure chamber C provided in the third passage P3, a free piston 31 movably accommodated in the pressure chamber C and dividing the pressure chamber C into a one-side pressure chamber c1 communicated with the compression side chamber R2 through the first passage P1 and a other-side pressure chamber c2 communicated with the expansion side chamber R1 through the third passage P3, and a spring element 32 generating a biasing force that suppresses displacement of the free piston 31 with respect to the pressure chamber C.

[0070] Hereinafter, each part of the damping valve V1 and the shock absorber D1 will be described in detail. The upper end of the cylinder 20 is closed by fitting an annular rod guide 24 through which the piston rod 22 is inserted, and the lower end of the cylinder 20 is closed by a bottom cap 25. A piston 21 connected to the piston rod 22 is slidably inserted into the cylinder 20, and the inside of the cylinder 20 is divided into an expansion side chamber R1 and a compression side chamber R2. A sliding partition wall 26 is slidably inserted into the cylinder 20 below the piston 21, and an air chamber G is divided below the compression side chamber R2 in the cylinder 20. The expansion side chamber R1, the compression side chamber R2, and the pressure chamber C above the sliding partition wall 26 in the cylinder 20 are filled with a liquid such as hydraulic oil, and the air chamber G is filled with a gas. The liquid filled in the expansion-side chamber R1, the compression-side chamber R2, and the pressure chamber C may be, other than hydraulic oil, liquid such as water or an aqueous solution.

[0071] A seal member 27 that seals the outer periphery of the piston rod 22 is provided above the rod guide 24 in FIG. 1, so that the inside of the cylinder 20 is liquid-tight. In the illustrated example, the shock absorber D1 is set to be a so-called single rod type. Therefore, the volume of the piston rod 22 that moves in and out of the cylinder 20 with the expansion and contraction of the shock absorber D1 is compensated for by the sliding partition wall 26 moving in the vertical direction in FIG. 2 as the volume of the gas in the air chamber G expands or contracts. In this way, the shock absorber D1 is set to be a single cylinder type, but instead of providing the sliding partition wall 26 and the air chamber G, a reservoir may be provided on the outer periphery or outside of the cylinder 20 to compensate for the volume of the piston rod 22 by the reservoir. Also, the shock absorber D1 may be set to be a double rod type instead of a single rod type.

[0072] The shock absorber D1 provides a pressure chamber C in a piston rod 22. As shown in Fig. 3, the piston rod 22 includes a piston rod body 28, a piston holder 29 to which the piston 21, a normal valve element 35, and a bypass valve element 40 are attached, and a housing portion 30 that connects the piston rod body 28 and the piston holder 29 and in which a pressure chamber C is formed. A free piston 31 and a compression side coil spring 32a and an extension side coil spring 32b serving as spring elements 32 that position the free piston 31 at a neutral position in the housing portion 30 are accommodated in the housing portion 30 provided in the piston rod 22, and the housing portion 30 is partitioned into a one-side pressure chamber c1 and an other-side pressure chamber c2.

[0073] The piston holder 29 in the piston rod 22 includes a piston retaining shaft 29a, and the piston 21, the normal valve element 35, and the bypass valve element 40 are attached to the piston retaining shaft 29a. The piston 21 attached to the piston retaining shaft 29a can move in the vertical direction in Fig. 3 together with the piston rod 22 inside the cylinder 20 with its outer periphery in sliding contact with the inner periphery of the cylinder 20. The piston 21 includes an annular main body portion 21a, a cylindrical portion 21b protruding downward in Fig. 3 from the outer periphery of the main body portion 21a, an expansion-side bypass port 21c and a compression-side bypass port 21d provided in the main body portion 21a and communicating between the expansion-side chamber R1 and the compression-side chamber R2, and a piston ring 21e attached to the outer periphery and in sliding contact with the inner periphery of the cylinder 20.

[0074] In addition, an expansion side bypass damping valve 40a which is a leaf valve that opens and closes an outlet end, which is the lower end in FIG. 3, of the expansion side bypass port 21c is stacked below the piston 21 in FIG. 3, and a compression side bypass damping valve 40b which is a leaf valve that opens and closes an outlet end, which is the upper end in FIG. 3, of the compression side bypass port 21d is stacked above the piston 21 in FIG. 3.

[0075] The extension side bypass damping valve 40a and the compression side bypass damping valve 40b are both formed in an annular shape, and the inner circumference is fixed to the piston holder 29 of the piston rod 22, allowing the outer circumference to bend. The number and thickness of the leaf valves constituting the extension side bypass damping valve 40a and the compression side bypass damping valve 40b can be changed as desired according to the desired damping characteristics. The extension side bypass damping valve 40a and the compression side bypass damping valve 40b may be valves other than leaf valves.

[0076] When the pressure in the expansion-side chamber R1 becomes higher than the pressure in the contraction-side chamber R2 during the expansion operation of the shock absorber D1, and the pressure difference between the expansion-side chamber R1 and the contraction-side chamber R2 reaches or exceeds the valve opening pressure, the expansion-side bypass damping valve 40a bends its outer periphery to open the expansion-side bypass port 21c, and functions as a one-side bypass valve that resists the flow of liquid moving from the expansion-side chamber R1 to the contraction-side chamber R2. The expansion-side bypass damping valve 40a also has an orifice 40c formed by a notch on its outer periphery, and when the shock absorber D1 contracts, the orifice 40c comes into contact with the outlet end of the expansion-side bypass port 21c to communicate between the expansion-side bypass port 21c and the contraction-side chamber R2 only through the orifice 40c. When the pressure in the compression side chamber R2 becomes higher than the pressure in the expansion side chamber R1 during the contraction operation of the shock absorber D1 and the pressure difference between the two chambers reaches or exceeds the valve opening pressure, the compression side bypass damping valve 40b bends its outer periphery to open the compression side bypass port 21d and functions as a bypass valve on the other side that provides resistance to the flow of liquid moving from the compression side chamber R2 to the expansion side chamber R1. Also, the compression side bypass damping valve 40b closes the compression side bypass port 21d during the expansion operation of the shock absorber D1, setting the compression side bypass port 21d as a one-way passage.

[0077] Therefore, in the shock absorber D1 of this example, the second passage P2 is composed of the expansion side bypass port 21c and the compression side bypass port 21d, and the bypass valve element 40 is composed of the expansion side bypass damping valve 40a, the compression side bypass damping valve 40b, and the orifice 40c. As described above, the orifice 40c may be formed by providing a notch on the outer periphery of the expansion side bypass damping valve 40a, or may be formed by a recess provided in a valve seat on the piston 21 where the expansion side bypass damping valve 40a is seated and released. Also, the compression side bypass damping valve 40b may be provided with a notch functioning as an orifice, or the valve seat on which the compression side bypass damping valve 40b is seated and released may be provided with a recess functioning as an orifice.

[0078] The normal valve element 35 includes a valve element 36 whose inner periphery is fixed to the piston retaining shaft 29a and whose outer periphery is allowed to bend, a valve case 37 which is annular and fitted between the piston retaining shaft 29a and the cylindrical portion 21b of the piston 21 and has an annular opposing seat 37c which faces the outer periphery of the valve element 36, a spacer 38 which is interposed between the valve case 37 and the valve element 36 and adjusts the position of the valve element 36 with respect to the annular opposing seat 37c, and a valve stopper 39 which is interposed between the valve element 36 and the spacer 38. The normal valve element 35 is assembled to the outer periphery of the piston retaining shaft 29a together with a compression side bypass damping valve 40b, the piston 21, and the extension side bypass damping valve 40a, and is then fixed to the piston retaining shaft 29a by a nut 41 which is screwed to the lower end of the piston retaining shaft 29a in FIG. 3.

[0079] The valve case 37 is annular and includes a partition wall portion 37a that is stacked below the expansion-side bypass damping valve 40a in FIG. 3 and fits around the outer periphery of the piston retaining shaft 29a and fits around the inner periphery of the cylindrical portion 21b of the piston 21, and a cylindrical case portion 37b that extends downward from the outer periphery of the lower end of the partition wall portion 37a in FIG. 3 and has an annular opposing seat 37c. The partition wall portion 37a includes a plurality of ports 37a1 that penetrate in the axial direction, and the ports 37a1 communicate the compression-side chamber R2 with the expansion-side bypass port 21c and the compression-side bypass port 21d of the piston 21. In this way, the ports 37a1 in the valve case 37 form a first passage P1 that communicates the expansion-side bypass port 21c and the compression-side bypass port 21d as the second passage P2 with the compression-side chamber R2 as one chamber. The partition wall portion 37a is provided with an oblique hole 37a2 that opens from the inner periphery to the piston side end, which is the upper end in FIG.

[0080] The case portion 37b protrudes from the cylindrical portion 21b of the piston 21 toward the downward compression side chamber R2 while expanding its inner and outer diameters, and is provided with an annular opposing seat 37c formed by an annular protrusion protruding inwardly from the inner circumference of the lower end.

[0081] The valve body 36 is annular and is attached to the outer periphery of the piston holder shaft 29a together with a spacer 38 and a valve stopper 39, which are also annular. The inner periphery side is a fixed end and the outer periphery side is a free end, and is allowed to bend. The valve body 36 is configured by laminating an elastic annular plate with a large outer diameter, whose outer periphery face faces the inner periphery face of the annular facing seat 37c with almost no gap, and annular plates each having an outer diameter smaller than the annular plate above and below the annular plate, and the inner periphery is fixed to the piston holder shaft 29a, and each of the outer periphery side is allowed to bend in the up and down directions in FIG. 3. The number of annular plates constituting the valve body 36 can be changed arbitrarily, and the valve body 36 may be configured with a single annular plate.

[0082] The regular valve element 35 is composed of a valve element 36 and an annular opposing seat 37c in a valve case 37, and when the outer peripheral surface of the annular plate having the maximum outer diameter in the valve element 36 faces the inner peripheral surface of the annular opposing seat 37c without bending, the valve is closed, making it difficult for liquid to pass through the first passage P1, and when the outer periphery of the valve element 36 bends in the vertical direction in Fig. 3, the valve is opened, creating an annular gap between the outer periphery of the valve element 36 and the annular opposing seat 37c, allowing liquid to pass through the first passage P1. In this way, the regular valve element 35 generates a damping force that prevents expansion and contraction both when the shock absorber D1 is expanded and when it is contracted, because the valve element 36 can be bent both vertically in Fig. 3.

[0083] When the expansion / contraction speed of the shock absorber D1 is in the extremely low speed range and all of the flow rate of the liquid flowing through the first passage P1 passes through the second passage P2, the difference between the pressure in the expansion side chamber R1 and the pressure in the compression side chamber R2 is small, so the expansion side bypass damping valve 40a and the compression side bypass damping valve 40b do not open and the valve body 36 bends to pass through the normal valve element 35 and the orifice 40c. However, the resistance that the normal valve element 35 provides to the flow of liquid passing through the first passage P1 is set to be greater than the resistance that the orifice 40c provides to the flow of liquid passing through the second passage P2.

[0084] Furthermore, when the valve body 36 in the normal valve element 35 bends upward in FIG. 3, it is supported by a valve stopper 39, preventing it from bending further upward, and when it bends downward in FIG. 3, it is supported by the outer periphery of the upper end of a nut 41, preventing it from bending further downward, thereby protecting it from deterioration due to excessive bending deformation.

[0085] Next, although not shown in Fig. 3, the piston rod main body 28 of the piston rod 22 protrudes outward from the cylinder 20 through the inner periphery of the rod guide 24 provided at the upper end of the cylinder 20, and has a threaded portion 28a on the outer periphery of the lower end. As shown in Fig. 3, the piston holder 29 has a piston retaining shaft 29a, a disk portion 29b provided at the upper end of the piston retaining shaft 29a in Fig. 3, a cylindrical socket 29c rising from the outer periphery of the disk portion 29b, a projection 29d rising from the upper end of the disk portion 29b in Fig. 3, and a hole 29e that opens from the tip of the projection 29d and leads to an oblique hole 37a2 provided in a valve case 37 of the normal valve element 35 on the outer periphery of the piston retaining shaft 29a.

[0086] As described above, the piston 21, the normal valve element 35, and the bypass valve element 40 are assembled to the outer periphery of the piston retaining shaft 29a, and the piston 21, the normal valve element 35, and the bypass valve element 40 are fixed to the piston retaining shaft 29a by being sandwiched between the nut 41, which is screwed to the lower end of the piston retaining shaft 29a in FIG. 3, and the disk portion 29b.

[0087] When the piston 21, normal valve element 35, and bypass valve element 40 are fixed to the piston retaining shaft 29a in this manner, the hole 29e faces the oblique hole 37a2 that opens into the inner circumference of the valve case 37, and the first passage P1 and the second passage P2 are connected to the inside of the housing portion 30 via the oblique hole 37a2 surrounded by the piston 21 and the valve case 37.

[0088] Next, the disk portion 29b has a flange 29b1 on its outer periphery. The socket 29c rises from the outer periphery of the disk portion 29b, which is on the inner periphery side of the flange 29b1, toward the side opposite to the piston holding shaft, and has a threaded portion 29f on its outer periphery. The housing portion 30 is connected to the threaded portion 29f of the socket 29c by threading and is connected to the piston holder 29, and a free piston 31 is accommodated inside. The inside of the housing portion 30 is divided by the free piston 31 into a one-side pressure chamber c1 that is communicated with the compression-side chamber R2 through the first passage P1, the oblique hole 37a2, and the hole 29e, and a second-side pressure chamber c2 that is communicated with the expansion-side chamber R1 through a hole 30f provided in the housing portion 30.

[0089] The projection 29d rises from the axial center of the disk portion 29b toward the side opposite the piston retaining shaft and projects into the one-side pressure chamber c1, and is provided with an annular groove 29d1 provided in the middle portion in the axial direction of the outer periphery, and a port 29d2 that opens from the bottom of the annular groove 29d1 and communicates with the hole 29e. In addition, a groove 29d3 is provided along the vertical direction in FIG. 3 on the outer periphery opposite the piston retaining shaft side of the annular groove 29d1 of the projection 29d.

[0090] Further, an annular compression side check valve 42 is attached to the annular groove 29d1 of the protrusion 29d. The compression side check valve 42 is an O-ring that is elastically attached to the outer periphery of the protrusion 29d and opens and closes the port 29d2. When the compression side check valve 42 receives pressure from the port 29d2 side and expands in diameter, it opens the outlet end of the port 29d2 to communicate the one side pressure chamber c1 with the compression side chamber R2 through the hole 29e, the oblique hole 37a2, and the first passage P1, and closes the port 29d2 when the pressure in the one side pressure chamber c1 is higher than the pressure in the compression side chamber R2. Note that the compression side check valve 42 may be an O-ring or a C-ring made of rubber, synthetic resin, or metal, as long as it has elasticity and can open and close the port 29d2.

[0091] As shown in Figure 3, the housing portion 30 comprises a nut portion 30a having a flange portion 30b on its outer periphery and screwed to the screw portion 28a of the piston rod main body 28, and a tubular portion 30c extending downward in Figure 3 from the outer periphery of the flange portion 30b and screwed to the screw portion 29f of the piston holder 29, and forms a pressure chamber C together with the piston holder 29.

[0092] As shown in Fig. 3, the cylindrical portion 30c has a thick wall thickness and a small inner diameter at the upper end side, and is provided with an annular groove 30d provided along the circumferential direction in the portion with the small inner diameter, a port 30e that opens from the bottom of the annular groove 30d and penetrates the wall thickness, and a hole 30f that penetrates the wall thickness below the annular groove 30d in Fig. 3. In addition, by making the inner diameter on the upper side of the cylindrical portion 30c smaller, a step 30g is formed on the inner circumference.

[0093] The pressure chamber C is connected to the expansion-side chamber R1 through the hole 30f, and is connected to the compression-side chamber R2 through the hole 29e, the oblique hole 37a2, and the first passage P1. Thus, the third passage P3 is formed by the hole 30f, the hole 29e, and the oblique hole 37a2. The third passage P3 is connected to the compression-side chamber R2 through the port 37a1 in the valve case 37 that forms the first passage P1, and is in parallel with the expansion-side bypass port 21c and the compression-side bypass port 21d that function as the second passage P2 provided in the piston 21, and connects the first passage P1 to the expansion-side chamber R1.

[0094] In addition, an annular extension-side check valve 43 is installed in an annular groove 30d provided on the inner circumference of the tubular portion 30c. The extension-side check valve 43 is installed in the annular groove 30d with elasticity and is an O-ring that opens and closes the open end of the port 30e. When the extension-side check valve 43 receives pressure from the port 30e side and contracts in diameter, it opens the port 30e to communicate the other-side pressure chamber c2 with the extension-side chamber R1, and when the pressure in the other-side pressure chamber c2 is higher than the pressure in the extension-side chamber R1, it closes the port 30e. Note that the extension-side check valve 43 may be an O-ring or a C-ring made of rubber, synthetic resin, or metal, as long as it has elasticity and can open and close the port 30e.

[0095] As shown in Figure 3, the free piston 31 is in sliding contact with the inner circumference of the cylindrical portion 30c of the housing portion 30 and can move in the vertical direction in Figure 3 relative to the housing portion 30, dividing the pressure chamber C into one side pressure chamber c1 and the other side pressure chamber c2.

[0096] Specifically, the free piston 31 comprises a partition portion 31a whose outer periphery is in sliding contact with the inner periphery of the cylindrical portion 30c, a cylindrical shutter 31b rising from the end portion of the partition portion 31a on the upper side in Figure 3, which is the other pressure chamber side, and a cylindrical case 31c rising from the end portion of the partition portion 31a on the lower side in Figure 3, which is the one pressure chamber side.

[0097] The shutter 31b is cylindrical, rises from the outer periphery of the upper end of the partition wall portion 31a in Fig. 3, and can be inserted into the inner periphery of the portion of the cylindrical portion 30c with a small inner diameter. A groove 31b1 is provided on the outer periphery of the shutter 31b along the vertical direction in Fig. 3, which is the axial direction. Therefore, when the free piston 31 moves upward in Fig. 3, which is the direction in which the other-side pressure chamber c2 is compressed, the shutter 31b reaches the portion of the cylindrical portion 30c with a small inner diameter and faces the opening of the hole 30f, gradually blocking the opening, and when it completely faces the opening, the flow path area between the other-side pressure chamber c2 and the hole 30f is almost limited to the cross-sectional area of ​​the groove 31b1 on the outer periphery of the shutter 31b. In addition, the outer diameter of the upper end of the shutter 31b in Figure 3 decreases toward the upper end, and even if the shutter 31b is displaced until it faces the extension side check valve 43 attached to the inner circumference of the tubular portion 30c, the shutter 31b does not interfere with the extension side check valve 43 and does not affect the operation of the extension side check valve 43.

[0098] The case 31c is cylindrical and protrudes downward from the lower end of the partition wall 31a in Fig. 3, allowing the projection 29d to be inserted inward. Therefore, when the free piston 31 moves downward in Fig. 3 in a direction compressing the one-side pressure chamber c1, the projection 29d can enter the case 31c, and the free piston 31 can move downward until the lower end of the partition wall 31a in Fig. 3 abuts against the projection 29d. In this way, when the free piston 31 moves in a direction compressing the one-side pressure chamber c1 and the projection 29d is inserted into the case 31c, the flow passage area between the one-side pressure chamber c1 and the third passage P3 is limited to the cross-sectional area of ​​the groove 29d3 on the outer periphery of the projection 29d.

[0099] Furthermore, the inner diameter of the lower end of case 31c in Figure 3 increases as it approaches the bottom end, so that even if partition portion 31a of free piston 31 is displaced until it contacts the upper end of protrusion 29d, case 31c does not interfere with compression side check valve 42 attached to the outer periphery of protrusion 29d, and does not affect the operation of compression side check valve 42.

[0100] The spring element 32 includes a compression side coil spring 32a and an extension side coil spring 32b. The free piston 31 is sandwiched between the compression side coil spring 32a, which is interposed between the inner circumferential side of the shutter 31b of the partition wall portion 31a and the flange portion 30b of the nut portion 30a and housed in the other side pressure chamber c2, and the extension side coil spring 32b, which is interposed between the outer circumferential side of the case 31c of the partition wall portion 31a and the outer circumferential side of the protrusion 29d of the disk portion 29b of the piston holder 29 and housed in the one side pressure chamber c1. The free piston 31 biased by the spring element 32 in this manner is positioned at a neutral position in the pressure chamber C. In this embodiment, the neutral position is set at a position corresponding to the stroke center of the free piston 31 in the pressure chamber C, but the neutral position does not necessarily have to coincide with the stroke center of the free piston 31.

[0101] Furthermore, the compression-side coil spring 32a is inserted into the inner periphery of the shutter 31b of the free piston 31, and does not become eccentric relative to the free piston 31 when it expands and contracts, so that a stable biasing force can be applied to the free piston 31. The extension-side coil spring 32b is fitted into the outer periphery of the case 31c of the free piston 31, and does not become eccentric relative to the free piston 31 when it expands and contracts, so that a stable biasing force can be applied to the free piston 31. Note that the spring constituting the spring element 32 may be an elastic body such as a wave washer, a leaf spring, a disc spring, rubber, etc., other than a coil spring.

[0102] The damping valve V1 and the shock absorber D1 are configured as described above, and the operation of the damping valve V1 and the shock absorber D1 will be described below. When the piston 21 moves up and down in FIG. 3 relative to the cylinder 20 and the shock absorber D1 performs an expansion / contraction operation, one of the expansion-side chamber R1 and the compression-side chamber R2 is compressed by the piston 21, and the other of the expansion-side chamber R1 and the compression-side chamber R2 is expanded. Therefore, the pressure of the expansion-side chamber R1 or the compression-side chamber R2 that is compressed increases, and at the same time, the pressure of the expansion-side chamber R1 or the compression-side chamber R2 that is expanded decreases, generating a pressure difference between the two.

[0103] During the extension operation of the shock absorber D1, the liquid in the expansion-side chamber R1 being compressed moves to the compression-side chamber R2 through the normal valve element 35, which is made up of the valve body 36 and the annular opposing seat 37c in the first passage P1, the expansion-side bypass damping valve 40a and the orifice 40c of the bypass valve element 40 in the second passage P2, and a virtual passage, which is made up of the third passage P3 and the pressure chamber C.

[0104] On the other hand, when the shock absorber D1 is contracted, the liquid in the compression-side chamber R2 to be compressed moves to the expansion-side chamber R1 through the normal valve element 35 consisting of the valve body 36 and the annular opposing seat 37c in the first passage P1, the compression-side bypass damping valve 40b and the orifice 40c of the bypass valve element 40 in the second passage P2, and additionally through an apparent passage consisting of the third passage P3 and the pressure chamber C.

[0105] Here, whether the frequency of the vibration input to the shock absorber D1, i.e., the frequency of the vibration in the expansion / contraction direction of the shock absorber D1, is low or high, when the piston speed in the expansion stroke of the shock absorber D1 is the same, the amplitude of the shock absorber D1 when low-frequency vibration is input is larger than the amplitude of the shock absorber D1 when high-frequency vibration is input. In this way, when the frequency of the vibration input to the shock absorber D1 is low, the amplitude is large, so the flow rate of the liquid going back and forth between the expansion-side chamber R1 and the contraction-side chamber R2 in one expansion / contraction cycle is large. The displacement of the free piston 31 increases in proportion to the flow rate, but since the free piston 31 is biased by the spring element 32, the biasing force from the spring element 32 that the free piston 31 receives increases as the displacement of the free piston 31 increases, and accordingly a pressure difference occurs between the pressure in the one-side pressure chamber c1 and the pressure in the other-side pressure chamber c2, reducing the pressure difference between the pressure-side chamber R2 and the one-side pressure chamber c1 and the pressure difference between the expansion-side chamber R1 and the other-side pressure chamber c2, and the flow rate of the liquid passing through the aforementioned apparent passage decreases. The flow rate of the liquid passing through the second passage P2 increases as the flow rate of the liquid passing through the apparent passage decreases.

[0106] Conversely, when high-frequency vibration is input to the shock absorber D1, the amplitude is smaller than that when low-frequency vibration is input, so the flow rate of the liquid passing between the expansion-side chamber R1 and the contraction-side chamber R2 in one period of expansion and contraction is small, and the displacement of the free piston 31 is also small. Then, the biasing force from the spring element 32 that the free piston 31 receives is also small. Accordingly, the pressure in the one-side pressure chamber c1 and the pressure in the other-side pressure chamber c2 become almost equal, and the differential pressure between the contraction-side chamber R2 and the one-side pressure chamber c1 and the differential pressure between the expansion-side chamber R1 and the other-side pressure chamber c2 become larger than that when low-frequency vibration is input, and the flow rate passing through the apparent passage is larger than that when low-frequency vibration is input. Therefore, when low-frequency vibration is input, the flow rate passing through the apparent passage is larger than the flow rate through the second passage P2, so that more liquid passes through the third passage P3.

[0107] In this way, when the shock absorber D1 expands and contracts at a low frequency, the amount of liquid passing through the second passage P2 becomes relatively greater than the amount of liquid passing through the third passage P3, and when the shock absorber D1 expands and contracts at a high frequency, the amount of liquid passing through the second passage P2 becomes relatively less than the amount of liquid passing through the third passage P3.

[0108] Since the first passage P1 is connected in series to the second passage P2 and the third passage P3 which are connected in parallel, the total flow rate of the liquid passing between the compression side chamber R2 and the expansion side chamber R1 flows regardless of the frequency of expansion and contraction of the shock absorber D1.

[0109] When the shock absorber D1 expands and contracts at a low frequency and the expansion / contraction speed is in the extremely low speed range when the shock absorber D1 starts to move, the valve body 36 in the normal valve element 35 hardly bends and maintains a state in which the outer periphery faces the inner periphery of the annular opposing seat 37c, or even if the valve body 36 bends, the flow path area between the valve body 36 and the annular opposing seat 37c is restricted to an extremely small value, so that liquid does not easily pass between the valve body 36 and the annular opposing seat 37c, and a difference occurs between the pressure in the expansion-side chamber R1 and the pressure in the compression-side chamber R2. As a result, the damping force characteristic of the shock absorber D1 becomes such that the damping force increases significantly as the expansion / contraction speed increases when the expansion / contraction speed is near 0, as shown in FIG. 4. When the shock absorber D1 expands at a low frequency, the liquid passes through the first passage P1 without fail, and mainly through the second passage P2 of the second passage P2 and the third passage P3. However, the pressure in the expansion side chamber R1 does not reach the valve opening pressure, so the expansion side bypass damping valve 40a remains closed, and the liquid passes through the orifice 40c. When the expansion speed of the shock absorber D1 is in the extremely low speed range, the resistance to the liquid flow provided by the normal valve element 35 is greater than the resistance provided by the orifice 40c, so the shock absorber D1 generates a damping force by the normal valve element 35. When the shock absorber D1 contracts at a low frequency, the liquid mainly passes through the second passage P2. However, the pressure in the compression side chamber R2 does not reach the valve opening pressure, so the compression side bypass damping valve 40b remains closed, and the liquid passes through the orifice 40c. When the contraction speed of the shock absorber D1 is in the extremely low speed range, the resistance to the flow of liquid that the normal valve element 35 provides is greater than the resistance that the orifice 40c provides to the flow of liquid, so that the shock absorber D1 generates a damping force by the normal valve element 35.

[0110] When the shock absorber D1 expands and contracts at a low frequency and the expansion / contraction speed of the shock absorber D1 is in a low-speed range exceeding the extremely low speed range, the valve body 36 of the normal valve element 35 bends significantly, the resistance to the liquid flow provided by the orifice 40c becomes greater than the resistance to the liquid flow provided by the normal valve element 35, and neither the extension side bypass damping valve 40a nor the compression side bypass damping valve 40b opens. As a result, the shock absorber D1 exerts a damping force mainly by the orifice 40c, and the damping force characteristic of the shock absorber D1 is proportional to the square of the expansion / contraction speed, as shown in FIG. 4.

[0111] When the shock absorber D1 expands and contracts at a low frequency and the expansion / contraction speed of the shock absorber D1 is in a high-speed range exceeding the low-speed range, the valve body 36 of the normal valve element 35 is largely bent, the expansion-side bypass damping valve 40a opens when the shock absorber D1 expands, and the compression-side bypass damping valve 40b opens when the shock absorber D1 contracts, so that the resistance to the flow of liquid provided by the expansion-side bypass damping valve 40a or the compression-side bypass damping valve 40b becomes greater than the resistance to the flow of liquid provided by the normal valve element 35. Therefore, in this case, the shock absorber D1 exerts a damping force mainly by the expansion-side bypass damping valve 40a or the compression-side bypass damping valve 40b, and therefore the damping force characteristic of the shock absorber D1 is such that the damping force specific to the leaf valve is approximately proportional to the expansion / contraction speed, but the damping coefficient is lower than that of the normal valve element 35 or the orifice 40c, as shown in FIG.

[0112] Next, when the shock absorber D1 expands and contracts at a high frequency and the expansion / contraction speed is in a very low speed range at the beginning of the shock absorber D1 movement, the valve body 36 in the normal valve element 35 hardly bends and maintains a state in which the outer periphery faces the inner periphery of the annular facing seat 37c, or even if the valve body 36 bends, the flow passage area between the valve body 36 and the annular facing seat 37c is limited to an extremely small value, so that the liquid does not easily pass between the valve body 36 and the annular facing seat 37c, and a difference occurs between the pressure in the expansion-side chamber R1 and the pressure in the contraction-side chamber R2, and the damping force characteristic of the shock absorber D1 becomes such that the damping force rises significantly as the expansion / contraction speed increases when the expansion / contraction speed is near 0. Note that when the shock absorber D1 expands and contracts at a high frequency, the liquid always passes through the first passage P1, and mainly passes through the third passage out of the second passage P2 and the third passage P3. Therefore, the shock absorber D1 generates a damping force by the normal valve element 35.

[0113] Furthermore, when the shock absorber D1 expands and contracts at high frequency, and the expansion / contraction speed of the shock absorber D1 is in a speed range that exceeds the extremely low speed range, the shock absorber D1 generates a damping force due to the resistance that the third passage P3 itself and the normal valve element 35 offer to the flow of liquid. However, since the normal valve element 35 opens widely, the damping force characteristics of the shock absorber D1, as shown by the dashed line in FIG. 4, have a smaller damping coefficient compared to the damping force characteristics in the extremely low speed range, and the damping force does not increase significantly even if the expansion / contraction speed increases.

[0114] In this way, whether the shock absorber D1 vibrates at a low frequency or at a high frequency, the entire flow rate of the liquid passing between the expansion-side chamber R1 and the compression-side chamber R2 passes through the normal valve element 35 in the first passage P1, and therefore the normal valve element 35 can raise the damping force at the beginning of the expansion / contraction period to suppress the vibration, thereby improving the ride comfort of the vehicle. Also, when the shock absorber D1 vibrates at a low frequency and the expansion / contraction speed becomes high, the vibration can be suppressed by the bypass valve element 40, which is suitable for suppressing vibration at high speeds, so that even if the vibration becomes large, a corresponding damping force is generated, thereby improving the ride comfort of the vehicle.

[0115] Furthermore, when the shock absorber D1 vibrates at high frequency and the expansion / contraction speed becomes high, the normal valve element 35 opens wide and the damping coefficient becomes small, so that the function of reducing the damping force by bypassing the second passage P2 in the pressure chamber C is not hindered, and the damping force when vibrating at high frequency and high speed can be reduced, thereby improving the ride comfort in the vehicle even in such a situation.

[0116] Furthermore, by minimizing the resistance that the third passage P3 offers to the flow of liquid, the shock absorber D1 changes the damping force in response to the amplitude of the input vibration rather than the frequency of the vibration. In response to input of small amplitude vibration, a low damping force is generated to insulate the transmission of vibration from the axle side to the vehicle body, and in response to input of large amplitude vibration, a high damping force is generated to suppress vibration of the vehicle body, thereby improving the ride comfort of the vehicle.

[0117] The damping valve V1 specifically configured as described above includes a first passage P1 having one end communicated with the compression side chamber (one chamber) R2, a second passage P2 and a third passage P3 arranged in parallel with each other and communicating the other end of the first passage P1 with the extension side chamber (other chamber) R1, a normal valve element 35 provided in the first passage P1 and providing resistance to the flow of liquid flowing through the first passage P1, a bypass valve element 40 provided in the second passage P2 and providing resistance to the flow of liquid flowing through the second passage P2, a pressure chamber C provided in the third passage P3, a free piston 31 movably accommodated in the pressure chamber C and dividing the pressure chamber C into a one-side pressure chamber c1 communicated with the compression side chamber (one chamber) R2 through the first passage P1 and a other-side pressure chamber c2 communicated with the extension side chamber (other chamber) R1 through the third passage P3, and a spring element 32 generating a biasing force that suppresses displacement of the free piston 31 with respect to the pressure chamber C.

[0118] With the damping valve V1 configured in this manner, the entire amount of liquid always flows through the normal valve element 35, and the flow rate of liquid flowing through the bypass valve element 40 and the pressure chamber C varies depending on the frequency or amplitude of the vibration of the shock absorber D1. Therefore, with the shock absorber D1 of this embodiment, unlike conventional damping valves and shock absorbers, a sufficient amount of liquid is allowed to pass through the normal valve element 35, making it possible to actively utilize the damping force characteristics of the normal valve element 35, so that when high-frequency vibration or small-amplitude vibration is input, the normal valve element 35 can be fully utilized to exhibit damping force characteristics suitable for that vibration, thereby improving the ride comfort of the vehicle.

[0119] The normal valve element 35 in the damping valve V1 of this embodiment includes an annular valve body 36 having an inner circumferential side as a fixed end and an outer circumferential side as a free end, and an annular opposing seat 37c radially opposing the free end of the valve body 36. The bypass valve element 40 includes a compression side bypass valve (one side bypass valve) 40b which provides resistance to the flow of liquid from the compression side chamber (one chamber) R2 to the extension side chamber (other chamber) R1 and has a valve opening pressure higher than that of the normal valve element 35, an extension side bypass valve (other side bypass valve) 40a which provides resistance to the flow of liquid from the extension side chamber (other chamber) R1 to the compression side chamber (one chamber) R2 and has a valve opening pressure higher than that of the normal valve element 35, and an orifice 40c which provides resistance to the flow of liquid traveling between the compression side chamber (one chamber) R2 and the extension side chamber (other chamber) R1.

[0120] According to the damping valve V1 configured in this manner, the valve body 36 can be flexed in both directions in the axial direction relative to the annular opposing seat 37c to open the valve, so that one valve body 36 can exhibit damping force while allowing liquid to flow in both directions between the extension-side chamber (the other chamber) R1 and the compression-side chamber (the one chamber) R2. The valve body 36 is compact and can be easily applied to the shock absorber D1. By making the annular gap between the valve body 36 and the annular opposing seat 37c extremely small, the damping force can be raised at the beginning of the expansion / contraction of the shock absorber D1 to suppress vibration regardless of the frequency or the amplitude of the vibration, so that the ride comfort of the vehicle can be improved. When the shock absorber D1 vibrates at a low frequency or with a large amplitude and the expansion / contraction speed becomes high, the vibration can be suppressed by the compression-side bypass valve (the bypass valve on one side) 40b or the extension-side bypass valve (the bypass valve on the other side) 40a, which are suitable for suppressing vibration at high speeds. Therefore, even if the vibration becomes large, a corresponding damping force can be generated, so that the ride comfort of the vehicle can be improved. Furthermore, when the shock absorber D1 vibrates at a high frequency or with a small amplitude and the expansion / contraction speed of the shock absorber D1 reaches a high speed range, the valve body 36 does not bend significantly and the damping force does not become excessively high, so that the effect of reducing the damping force by utilizing the third passage P3 when high frequency or small amplitude vibration is input is not impaired.

[0121] Also, in the specific shock absorber D1, the normal valve element 35 in the damping valve V1 may be set to provide a greater resistance to the flow of liquid than the bypass valve element 40 when the liquid passes through at a flow rate less than a predetermined flow rate, and to provide a smaller resistance to the flow of liquid than the bypass valve element 40 when the liquid passes through at a flow rate greater than the predetermined flow rate. According to the damping valve V1 configured in this manner, the damping force characteristics of the normal valve element 35 are adapted to suppress vibrations input when high-frequency, small-amplitude vibrations are input or when the vehicle is traveling on a relatively smooth road surface, and the damping force characteristics of the bypass valve element 40 are adapted to suppress vibrations with large amplitudes and low frequencies, thereby improving the ride comfort of the vehicle.

[0122] Furthermore, in the shock absorber D1 of this embodiment, the normal valve element 35 in the damping valve V1 is set to provide a higher resistance to the flow of liquid passing therethrough than the bypass valve element 40 when the moving speed of the piston 21 relative to the cylinder 20 is in the extremely low speed range, and to provide a lower resistance than the bypass valve element 40 when the moving speed of the piston 21 relative to the cylinder 20 exceeds the extremely low speed range. According to the shock absorber D1 configured in this manner, the damping force characteristics of the normal valve element 35 are adapted to suppress vibrations input when high-frequency, small-amplitude vibrations are input or when the vehicle is traveling on a relatively smooth road surface, and the damping force characteristics of the bypass valve element 40 are adapted to suppress vibrations with large amplitudes and low frequencies, thereby improving the ride comfort of the vehicle.

[0123] In the shock absorber D1, when the stroke amount toward the extension side is large, the free piston 31 moves from the neutral position toward the direction of compressing the one-side pressure chamber c1 to a large amount. When the free piston 31 moves from the neutral position toward the direction of compressing the one-side pressure chamber c1, the protrusion 29d enters the case 31c from outside. When the protrusion 29d is outside the case 31c, there is a sufficiently large gap between the protrusion 29d and the case 31c, and the flow path is not restricted, so that the liquid can move between the one-side pressure chamber c1 and the hole 29e without much resistance. However, when the protrusion 29d enters the case 31c, the flow path area between the protrusion 29d and the case 31c is reduced to the cross-sectional area of ​​the groove 29d3. Therefore, it becomes difficult for the liquid in the one-side pressure chamber c1 to move to the compression side chamber R2 through the third passage P3, and the pressure in the one-side pressure chamber c1 increases, suppressing the movement of the free piston 31 in the direction of compressing the one-side pressure chamber c1. Furthermore, during expansion of the shock absorber D1, the pressure in the one-side pressure chamber c1 becomes higher than the pressure in the compression-side chamber R2, so that the compression-side check valve 42 attached to the outer periphery of the projection 29d blocks the port 29d2.

[0124] In this way, when the free piston 31 moves from the neutral position in the direction compressing the one-side pressure chamber c1 and moves to the vicinity of the stroke end, the protrusion 29d enters the case 31c, the pressure in the one-side pressure chamber c1 increases, and the movement of the free piston 31 in the direction compressing the one-side pressure chamber c1 is suppressed. Therefore, in the shock absorber D1 of this embodiment, when the free piston 31 moves from the neutral position in the direction compressing the one-side pressure chamber c1 and displaces to the vicinity of the stroke end, the degree of communication between the one-side pressure chamber c1 and the third passage P3 is reduced, the pressure in the one-side pressure chamber c1 increases, and the one-side pressure chamber c1 itself functions as a hydraulic lock chamber, thereby exerting a hydraulic lock function that suppresses further movement of the free piston 31 in the direction compressing the one-side pressure chamber c1.

[0125] In addition, after the free piston 31 increases the pressure in the one-side pressure chamber c1 to perform the hydraulic lock function, when the direction of extension and contraction of the shock absorber D1 changes from the extension operation to the contraction operation, the free piston 31 tries to move upward in FIG. 3 in the direction of compressing the other-side pressure chamber c2. At that time, liquid is supplied from the compression-side chamber R2 through the third passage P3 to the space between the case 31c and the protrusion 29d in the free piston 31. Furthermore, the compression-side check valve 42 receives pressure from the compression-side chamber R2 side through the port 29d2 to expand and open, and opens the port 29d2, so that liquid is quickly supplied from the compression-side chamber R2 through the port 29d2 into the one-side pressure chamber c1, which has limited communication with the third passage P3. In this way, even if the free piston 31 is displaced near the stroke end and the degree of communication between the third passage P3 and the one-side pressure chamber c1 is reduced, when the shock absorber D1 changes from extension to contraction, liquid is supplied from the compression side chamber R2 to the space between the case 31c and the protrusion 29d and to the one-side pressure chamber c1, respectively, without resulting in an excessive drop in pressure. Therefore, the free piston 31 can move smoothly in the direction of compressing the other-side pressure chamber c2 and can quickly return to the neutral position, and the function of reducing the damping force in response to the frequency of the shock absorber D1 or the function of reducing the damping force in response to the amplitude is not impaired.

[0126] As described above, when the free piston 31 is displaced in the pressure chamber C in the direction compressing the one-side pressure chamber c1 to the vicinity of the stroke end during the extension operation of the shock absorber D2, the hydraulic lock function is exerted to suppress the movement of the free piston 31 toward the stroke end on the compression side, and the moving speed of the free piston 31 is gradually reduced to stop the free piston 31 at the stroke end. When the free piston 31 stops, the entire flow of the liquid from the extension side chamber R1 to the compression side chamber R2 passes through the extension side bypass damping valve 40a and the orifice 40c, so that the damping force generated by the shock absorber D1 becomes high. Therefore, if the shock absorber D1 generates a low damping force before the stop of the free piston 31, the damping force generated by the stop of the free piston 31 becomes high, but since the free piston 31 gradually reduces its speed due to the hydraulic lock, the flow rate of the liquid passing through the third passage P3 decreases, and the flow rate of the liquid passing through the extension side bypass valve 40a increases accordingly, and the damping force generated by the shock absorber D1 gradually increases continuously, so that the sudden change in the damping force is mitigated.

[0127] In addition, when the stroke amount of the shock absorber D1 toward the contraction side is large, the free piston 31 moves from the neutral position toward the direction compressing the other-side pressure chamber c2 to a large extent. When the free piston 31 moves from the neutral position toward the direction compressing the other-side pressure chamber c2, the shutter 31b faces the opening of the hole 30f provided in the cylindrical portion 30c of the housing portion 30, and as the movement amount of the free piston 31 increases, the opening of the hole 30f is gradually blocked, and the degree of communication between the third passage P3 and the other-side pressure chamber c2 gradually decreases. Then, when the shutter 31b of the free piston 31 completely faces the opening of the hole 30f, the flow path area between the shutter 31b and the cylindrical portion 30c is limited to the cross-sectional area of ​​the groove 31b1.

[0128] Therefore, as the free piston 31 increases in the movement amount in the direction compressing the other-side pressure chamber c2 from the neutral position, the liquid in the other-side pressure chamber c2 gradually becomes less able to move to the expansion-side chamber R1 through the hole 30f, and the liquid in the other-side pressure chamber c2 becomes less able to move to the expansion-side chamber R1, so that the pressure in the other-side pressure chamber c2 increases and the movement of the free piston 31 in the direction compressing the other-side pressure chamber c2 is suppressed. In addition, since the pressure in the other-side pressure chamber c2 becomes higher than the pressure in the expansion-side chamber R1 during the contraction operation of the shock absorber D1, the expansion-side check valve 43 closes the third passage P3.

[0129] Therefore, when the free piston 31 moves from the neutral position in the direction compressing the other-side pressure chamber c2 and moves to the vicinity of the stroke end, the liquid in the other-side pressure chamber c2 becomes less likely to move to the extension-side chamber R1 as the movement of the free piston 31 progresses, and the pressure of the other-side pressure chamber c2 increases, suppressing the movement of the free piston 31 in the direction compressing the other-side pressure chamber c2. In this way, in the shock absorber D1 of this embodiment, when the free piston 31 moves from the neutral position in the direction compressing the other-side pressure chamber c2 and displaces to the vicinity of the stroke end, the degree of communication between the other-side pressure chamber c2 and the third passage P3 is reduced to increase the pressure of the other-side pressure chamber c2, and the other-side pressure chamber c2 itself functions as a hydraulic lock chamber, thereby exerting a hydraulic lock function that suppresses further movement of the free piston 31 in the direction compressing the other-side pressure chamber c2.

[0130] In addition, after the free piston 31 increases the pressure in the other-side pressure chamber c2 to perform the hydraulic lock function, when the direction of extension and contraction of the shock absorber D1 changes from contraction to expansion, the free piston 31 tries to move downward in FIG. 3 in a direction to compress the one-side pressure chamber c1. At that time, the expansion-side check valve 43 receives the pressure in the expansion-side chamber R1 and contracts to open, opening the port 30e, so that liquid is quickly supplied from the expansion-side chamber R1 through the port 30e into the other-side pressure chamber c2, whose communication with the third passage P3 is restricted. In addition, liquid is supplied from the other-side pressure chamber c2 through the groove 31b1 into the space between the outer periphery of the shutter 31b of the partition wall portion 31a of the free piston 31 and the step portion 30g of the cylindrical portion 30c. In this way, even if the free piston 31 is displaced near the stroke end to reduce the degree of communication between the third passage P3 and the other-side pressure chamber c2, when the shock absorber D1 changes from contraction to extension, liquid is supplied from the extension-side chamber R1 to the other-side pressure chamber c2, which does not result in an excessive pressure drop. Therefore, the free piston 31 can smoothly move in the direction of compressing the one-side pressure chamber c1 and can quickly return to the neutral position, and the function of reducing the damping force in response to the frequency of the shock absorber D1 or the function of reducing the damping force in response to the amplitude is not impaired.

[0131] As described above, when the free piston 31 is displaced in the direction compressing the other-side pressure chamber c2 in the housing portion 30 to the vicinity of the stroke end during the contraction operation of the shock absorber D1, the hydraulic lock function is exerted to suppress the movement of the free piston 31 toward the extension-side stroke end, gradually reducing the moving speed of the free piston 31 to stop the free piston 31 at the stroke end. When the free piston 31 stops, liquid cannot pass through the apparent passage, and the entire flow rate of liquid from the compression-side chamber R2 to the extension-side chamber R1 passes through the compression-side bypass damping valve 40b and the orifice 40c, so that the damping force generated by the shock absorber D1 becomes high. Therefore, if the shock absorber D1 is generating a low damping force before the free piston 31 stops, the damping force generated by the stopping of the free piston 31 increases. However, since the free piston 31 gradually reduces its speed due to hydraulic lock, the flow rate of liquid passing through the third passage P3 decreases. As a result, the flow rate of liquid passing through the compression side bypass valve 40b increases accordingly. As a result, the damping force generated by the shock absorber D1 increases continuously and gradually, thereby mitigating sudden changes in the damping force.

[0132] In the specific shock absorber D1, the free piston 31 moves to the stroke end, so that the other side pressure chamber c2 itself or the one side pressure chamber c1 itself functions as a hydraulic lock chamber, and thus a sudden change in the damping force can be mitigated, and the stroke length of the free piston 31 can be secured without providing a cushion in the pressure chamber C. In addition, since the shock absorber D1 does not require a cushion, the volume in the other side pressure chamber c2 and the one side pressure chamber c1 can be secured large, and the liquid in the other side pressure chamber c2 and the one side pressure chamber c1 can be used during hydraulic lock. Therefore, in the shock absorber D1, a sufficient flow rate of liquid can be flowed from the other side pressure chamber c2 or the one side pressure chamber c1 to the expansion side chamber (other side chamber) R1 or the compression side chamber (compression side chamber) R2 until the hydraulic lock function is exerted, and it is also easy to tune the transient characteristics that transition from a state in which a low damping force is generated by reducing the damping force to a state in which a high damping force is generated by the expansion side bypass damping valve 40a or the compression side bypass damping valve 40b. Therefore, according to the shock absorber D1 of the present embodiment, it is possible to easily tune the transient characteristics when the damping force changes while mitigating a sudden change in the damping force, and to ensure the stroke length of the free piston.

[0133] Furthermore, in the shock absorber D1, the passage area between the one-side pressure chamber c1 and the third passage P3 is reduced by inserting the protrusion 29d into the case 31c, and the passage area between the other-side pressure chamber c2 and the third passage P3 is reduced by facing the shutter 31b to the hole 30f. Therefore, a sufficient flow rate of liquid can be caused to flow into the expansion-side chamber R1 or the compression-side chamber R2 while gradually restricting the degree of communication between the other-side pressure chamber c2 and the third passage P3 or the degree of communication between the one-side pressure chamber c1 and the third passage P3.

[0134] Furthermore, the timing of transition from low to high damping force and the transient characteristics can be easily tuned by setting the area of ​​the opening of the groove 31b1 and the hole 30f of the shutter 31b, the number of grooves 31b1, the inner peripheral shape of the case 31c and the outer peripheral shape of the protrusion 29d, the cross-sectional area of ​​the groove 29d3 of the protrusion 29d, and the number of grooves 29d3. Also, if the cross-sectional area of ​​the groove 31b1 is set to be smaller from the tip side to the base end side of the shutter 31b, the flow path area between the cylindrical part 30c and the shutter 31b can be reduced the more the free piston 31 moves in the direction compressing the other side pressure chamber c2 after starting to block the opening of the hole 30f, and the transient characteristics can also be tuned by the shape of the groove 31b1. Similarly, by setting the cross-sectional area of ​​groove 29d3 to be smaller toward the base end than the tip end of protrusion 29d, the flow path area between protrusion 29d and case 31c can be made to decrease the more the free piston 31 moves in the direction of compressing one side pressure chamber c1 after it begins to block the opening of hole 29e, and the transient characteristics can also be tuned by the shape of groove 29d3.

[0135] Furthermore, in the specific shock absorber D1, the extension side check valve 43 is an annular valve body that has elasticity and is attached to an annular groove 30d provided on the inner circumference of the tubular portion 30c to open and close the open end of the port 30e, and the compression side check valve 42 has an annular valve body that has elasticity and is attached to annular groove 29d1 provided on the outer circumference of the protrusion 29d to open and close the open end of the port 29d2. Therefore, even if the extension side check valve 43 and the compression side check valve 42 are provided in the pressure chamber C, they do not interfere with the movement of the free piston 31, and the stroke length of the free piston 31 can be secured while avoiding the pressure chamber C from becoming larger.

[0136] In the shock absorber D1 described above, the pressure chamber C is provided on the extension side chamber R1 side of the piston rod 22, but may be provided on the compression side chamber R4 side as in the second specific shock absorber D2 shown in Fig. 5. As shown in Fig. 5, the second specific shock absorber D2 includes a cylinder 50 as an outer tube, a piston 51 slidably inserted into the cylinder 50 and dividing the inside of the cylinder 50 into an extension side chamber R3 and a compression side chamber R4, a piston rod 52 movably inserted into the cylinder 50 and one end connected to the piston 51, and a damping valve V2, and is interposed between the vehicle body and the wheels of a vehicle (not shown) to suppress vibration of the vehicle body by the damping force generated by the damping valve V2 during expansion and contraction.

[0137] The damping valve V2 is applied to a shock absorber D2, with one chamber serving as an expansion-side chamber R3 and the other chamber serving as a compression-side chamber R4. More specifically, the damping valve V2 includes a first passage P1 having one end communicated with the expansion-side chamber R3 as one chamber, a second passage P2 and a third passage P3 arranged in parallel with each other and communicating the other end of the first passage P1 with the compression-side chamber R4 as the other chamber, a normal valve element 65 provided in the first passage P1 and providing resistance to the flow of liquid flowing through the first passage P1, a bypass valve element 70 provided in the second passage P2 and providing resistance to the flow of liquid flowing through the second passage P2, a pressure chamber C1 provided in the third passage P3, a free piston 61 movably accommodated in the pressure chamber C1 and dividing the pressure chamber C1 into a one-side pressure chamber c3 communicated with the expansion-side chamber R3 through the first passage P1 and a other-side pressure chamber c4 communicated with the compression-side chamber R4 through the third passage P3, and a spring element 62 generating a biasing force that suppresses displacement of the free piston 61 with respect to the pressure chamber C1.

[0138] Although not shown, a rod guide, through whose inner periphery the piston rod 52 is inserted, and an annular seal member, which seals the outer periphery of the piston rod 52, are provided at the upper end of the cylinder 50, making the inside of the cylinder 50 liquid-tight. Although not shown, similar to shock absorber D1, the lower end of the cylinder 50 is closed by a bottom cap, and an air chamber is provided in the cylinder 50 by a sliding partition wall, which is slidably inserted into the cylinder 50 at the lower part in FIG. 5.

[0139] The piston rod 52 has a small diameter portion 52a formed at its lower end in Fig. 5, and a threaded portion 52b formed at the tip side of the small diameter portion 52a. In addition, a step portion 52c is provided by reducing the diameter of the lower end of the piston rod 52. The piston 51 includes an annular main body portion 51a, a cylindrical portion 51b protruding upward in Fig. 5 from the outer periphery of the main body portion 51a, an expansion-side bypass port 51c and a compression-side bypass port 51d provided in the main body portion 51a and communicating between the expansion-side chamber R3 and the compression-side chamber R4, and a piston ring 51e attached to the outer periphery and in sliding contact with the inner periphery of the cylinder 50.

[0140] In addition, an expansion side bypass damping valve 70a which is a leaf valve that opens and closes an outlet end, which is the lower end of the expansion side bypass port 51c in FIG. 5, is stacked below the piston 51 in FIG. 5, and a compression side bypass damping valve 70b which is a leaf valve that opens and closes an outlet end, which is the upper end of the compression side bypass port 51d in FIG. 5, is stacked above the piston 51 in FIG. 5.

[0141] The expansion side bypass damping valve 70a and the compression side bypass damping valve 70b are both formed in an annular shape, and the inner circumference is fixed to the small diameter portion 52a of the piston rod 52, allowing the outer circumference to bend. The number and thickness of the leaf valves constituting the expansion side bypass damping valve 70a and the compression side bypass damping valve 70b can be changed as desired according to the desired damping characteristics. The expansion side bypass damping valve 70a and the compression side bypass damping valve 70b may be valves other than leaf valves.

[0142] When the pressure in the expansion-side chamber R3 becomes higher than the pressure in the compression-side chamber R4 during the expansion operation of the shock absorber D2 and the pressure difference between the expansion-side chamber R3 and the compression-side chamber R4 reaches or exceeds the valve opening pressure, the expansion-side bypass damping valve 70a bends its outer periphery to open the expansion-side bypass port 51c, and functions as a one-side bypass valve that resists the flow of liquid moving from the expansion-side chamber R3 to the compression-side chamber R4. The expansion-side bypass damping valve 70a also has an orifice 70c formed by a notch on its outer periphery, and when the shock absorber D2 contracts, the orifice 70c comes into contact with the outlet end of the expansion-side bypass port 51c to communicate between the expansion-side bypass port 51c and the compression-side chamber R4 only through the orifice 70c. When the pressure in the compression side chamber R4 becomes higher than the pressure in the expansion side chamber R3 during contraction of the shock absorber D2 and the pressure difference between the two chambers reaches or exceeds the valve opening pressure, the compression side bypass damping valve 70b bends its outer periphery to open the compression side bypass port 51d and functions as a bypass valve on the other side that provides resistance to the flow of liquid moving from the compression side chamber R4 to the expansion side chamber R3. Also, the compression side bypass damping valve 70b closes the compression side bypass port 51d during expansion of the shock absorber D2, setting the compression side bypass port 51d as a one-way passage.

[0143] Therefore, in the shock absorber D2 of this example, the second passage P2 is composed of the expansion side bypass port 51c and the compression side bypass port 51d, and the bypass valve element 70 is composed of the expansion side bypass damping valve 70a, the compression side bypass damping valve 70b, and the orifice 70c.

[0144] The normal valve element 65 includes a valve body 66 whose inner periphery is fixed to the small diameter portion 52a of the piston rod 52 and whose outer periphery is allowed to bend, a valve case 67 which is annular and fitted between the small diameter portion 52a and the cylindrical portion 51b of the piston 51 and has an annular seat 67c which faces the outer periphery of the valve body 66, a spacer 68 which is interposed between the valve case 67 and the valve body 66 and adjusts the position of the valve body 66 with respect to the annular seat 67c, a valve stopper 69 which is interposed between the valve body 66 and the spacer 68, and a valve stopper 71 which is stacked above the valve body 66 in Fig. 5. The normal valve element 65 is assembled to the outer periphery of the small diameter portion 52a of the piston rod 52 together with the compression side bypass damping valve 70b, the piston 51, and the extension side bypass damping valve 70a, and then fixed to the piston rod 52 by a housing 55 which is screwed to the lower end of the piston rod 52 in Fig. 5.

[0145] The valve case 67 is annular and includes a partition wall portion 67a that is stacked above the compression side bypass damping valve 70b in FIG. 5 and fits around the outer periphery of the small diameter portion 52a of the piston rod 52 and fits around the inner periphery of the cylindrical portion 51b of the piston 51, and a cylindrical case portion 67b that extends upward from the outer periphery of the upper end of the partition wall portion 67a in FIG. 5 and has an annular opposing seat 67c. The partition wall portion 67a includes a plurality of ports 67a1 that penetrate in the axial direction, and communicates the expansion side chamber R3 with the expansion side bypass port 51c and the compression side bypass port 51d of the piston 51 through the ports 67a1. In this way, the ports 67a1 in the valve case 67 form a first passage P1 that communicates the expansion side bypass port 51c and the compression side bypass port 51d as the second passage P2 with the expansion side chamber R3 as one chamber. The partition wall portion 67a is provided with an oblique hole 67a2 that opens from the inner periphery to the piston side end, which is the lower end in FIG.

[0146] The case portion 67b protrudes from the cylindrical portion 51b of the piston 51 toward the upward extension side chamber R3 while expanding its inner and outer diameters, and is provided with an annular opposing seat 67c formed by an annular protrusion protruding inwardly from the inner circumference of the lower end.

[0147] The valve body 66 is annular and is attached to the outer periphery of the small diameter portion 52a of the piston rod 52 together with a spacer 68 and valve stoppers 69 and 71, which are also annular. The inner periphery side is a fixed end and the outer periphery side is a free end, and is allowed to bend. The valve body 66 is configured by laminating an elastic annular plate with a large outer diameter, whose outer periphery surface faces the inner periphery surface of the annular opposing seat 67c with almost no gap, and annular plates each having an outer diameter smaller than the annular plate above and below the annular plate, whose inner periphery is fixed to the small diameter portion 52a, and each of the outer periphery side is allowed to bend in the up and down directions in FIG. 5. The number of annular plates constituting the valve body 66 can be changed arbitrarily, and the valve body 66 may be configured with one annular plate.

[0148] The regular valve element 65 is composed of a valve body 66 and an annular seat 67c in a valve case 67, and when the outer peripheral surface of the annular plate having the maximum outer diameter in the valve body 66 faces the inner peripheral surface of the annular seat 67c without bending, the valve is closed, making it difficult for liquid to pass through the first passage P1, and when the outer periphery of the valve body 66 bends in the vertical direction in Fig. 5, the valve is opened, creating an annular gap between the outer periphery of the valve body 66 and the annular seat 67c, allowing liquid to pass through the first passage P1. In this way, the regular valve element 65 generates a damping force that prevents expansion and contraction both when the shock absorber D2 is expanded and when it is contracted, because the valve body 66 can be bent both vertically in Fig. 5.

[0149] When the expansion / contraction speed of the shock absorber D2 is in the extremely low speed range and all of the flow rate of the liquid flowing through the first passage P1 passes through the second passage P2, the difference between the pressure in the expansion side chamber R3 and the pressure in the compression side chamber R4 is small, so the expansion side bypass damping valve 70a and the compression side bypass damping valve 70b do not open and the valve body 66 bends to pass through the normal valve element 65 and the orifice 70c. However, the resistance that the normal valve element 65 offers to the flow of liquid passing through the first passage P1 is set to be greater than the resistance that the orifice 70c offers to the flow of liquid passing through the second passage P2.

[0150] Furthermore, when the valve body 66 in the normal valve element 65 bends upward in FIG. 5, it is supported by a valve stopper 71, which prevents it from bending further upward, and when it bends downward in FIG. 5, it is supported by a valve stopper 69, which prevents it from bending further downward, thereby protecting it from deterioration due to excessive bending deformation.

[0151] The piston rod 52 is provided with a hole 52d that opens from the tip of the small diameter portion 52a and communicates with an oblique hole 67a2 that opens into the inner periphery of the valve case 67. A first passage P1 formed by the port 67a1 and a second passage P2 formed by the expansion side bypass port 51c and the compression side bypass port 51d are connected via the hole 52d to an inside of a housing 55 that is attached to the lower end of the piston rod 52 in FIG. 5 and forms a pressure chamber C1.

[0152] The housing 55 includes a cylindrical nut portion 55a that is screwed to the lower end of the piston rod 52 in Figure 5, a flange portion 55b provided on the outer periphery of the nut portion 55a, a cylindrical portion 55c that extends downward in Figure 5 from the outer periphery of the flange portion 55b, and a lid portion 55d that closes the lower end of the cylindrical portion 55c, thereby forming a pressure chamber C1.

[0153] A hole 55e is provided in the cover portion 55d, and the pressure chamber C1 is connected to the compression side chamber R4. The pressure chamber C1 is connected to the first passage P1 and the second passage P2 through a hole 52d provided in the piston rod 52 and an oblique hole 67a2 in the valve case 67. In this damping valve V2, a third passage P3 is formed by the hole 55e, the hole 52d, and the oblique hole 67a2 in the valve case 67.

[0154] 5 within the pressure chamber C1, and a spring element 62 that biases the free piston 61. The outer periphery of the free piston 61 is in sliding contact with the cylindrical portion 55c to divide the pressure chamber C1 into a one-side pressure chamber c3 that communicates with the expansion-side chamber R3 as one chamber via the hole 52d, the oblique hole 67a2 of the valve case 67, and the first passage P1, and a other-side pressure chamber c4 that communicates with the compression-side chamber R4 as the other chamber via the hole 55e.

[0155] The spring element 62 includes a compression side coil spring 62a interposed between the free piston 61 and the flange portion 55b, and an extension side coil spring 62b interposed between the free piston 61 and the lid portion 55d. The compression side coil spring 62a and the extension side coil spring 62b sandwich the free piston 61 to position it at a neutral position, and generate a biasing force in a direction to return the free piston 61 to the neutral position when the free piston 61 is displaced. The spring element 62 may be formed of an elastic body other than a coil spring. In the shock absorber D2 of this embodiment, the free piston 61 includes a fitting cylinder 61a that fits on the outer periphery of the compression side coil spring 62a and a fitting cylinder 61b that fits on the outer periphery of the extension side coil spring 62b at the top and bottom in FIG. 5, respectively, and the eccentricity of the compression side coil spring 62a and the extension side coil spring 62b with respect to the free piston 61 is restricted, so that a stable biasing force can be applied to the free piston 61.

[0156] In addition, cushions 56 and 57 made of annular elastic bodies are accommodated in the housing 55 at the top and bottom in FIG. 5. When the free piston 61 is displaced from the neutral position to the vicinity of the upper stroke end in FIG. 5, the upper cushion 56 comes into contact with the free piston 61, and when the free piston 61 moves further upward, a resilient force is generated, gradually slowing down and stopping the free piston 61. When the free piston 61 is displaced from the neutral position to the vicinity of the lower stroke end in FIG. 5, the lower cushion 57 comes into contact with the free piston 61, and when the free piston 61 moves further upward, a resilient force is generated, gradually slowing down and stopping the free piston 61. In addition, instead of the cushions 56 and 57, a hydraulic lock chamber forming member that forms a hydraulic lock chamber between the free piston 61 and the cushion 57 may be accommodated in the housing 55.

[0157] The damping valve V2 and the shock absorber D2 are configured as described above, and the operation of the damping valve V2 and the shock absorber D2 will be described below. When the piston 51 moves up and down in FIG. 5 relative to the cylinder 50 and the shock absorber D2 performs an expansion / contraction operation, one of the expansion-side chamber R3 and the compression-side chamber R4 is compressed by the piston 51, and the other of the expansion-side chamber R3 and the compression-side chamber R4 is expanded. Therefore, the pressure of the expansion-side chamber R3 or the compression-side chamber R4 that is compressed increases, and at the same time, the pressure of the expansion-side chamber R3 or the compression-side chamber R4 that is expanded decreases, generating a pressure difference between the two.

[0158] During the extension operation of the shock absorber D2, the liquid in the expansion-side chamber R3 being compressed moves to the compression-side chamber R2 through the normal valve element 65, which is made up of the valve body 66 and the annular opposing seat 67c in the first passage P1, the expansion-side bypass damping valve 70a and the orifice 70c of the bypass valve element 70 in the second passage P2, and additionally through an apparent passage, which is made up of the third passage P3 and the pressure chamber C1.

[0159] On the other hand, when the shock absorber D2 is contracted, the liquid in the compression-side chamber R2 to be compressed moves to the expansion-side chamber R1 through the normal valve element 65 consisting of the valve body 66 and the annular opposing seat 67c in the first passage P1, the compression-side bypass damping valve 70b and the orifice 70c of the bypass valve element 70 in the second passage P2, and additionally through an apparent passage consisting of the third passage P3 and the pressure chamber C1.

[0160] In the shock absorber D2, as in the shock absorber D1, the flow rate passing through the third passage P3 can be selectively set to be increased or decreased depending on the frequency of the vibration input to the shock absorber D2 or depending on the magnitude of the amplitude by setting the pipeline resistance of the third passage P3.

[0161] Therefore, in the damping valve V2 and the shock absorber D2, similarly to the damping valve V1 and the shock absorber D1, when the shock absorber D2 expands and contracts at a low frequency or with a large amplitude, the amount of liquid passing through the second passage P2 is relatively larger than the amount of liquid passing through the third passage P3, and when the shock absorber D2 expands and contracts at a high frequency or with a small amplitude, the amount of liquid passing through the second passage P2 is relatively smaller than the amount of liquid passing through the third passage P3. Since the first passage P1 is connected in series to the second passage P2 and the third passage P3 which are connected in parallel, the total flow rate of liquid passing between the expansion-side chamber R3 and the compression-side chamber R4 flows regardless of the frequency and amplitude of the expansion and contraction of the shock absorber D2.

[0162] Furthermore, when the shock absorber D2 expands and contracts at a low frequency or with a large amplitude, and when the shock absorber D2 starts to move and the expansion / contraction speed is in the extremely low speed range, the valve body 66 in the normal valve element 65 hardly bends and maintains a state in which the outer periphery faces the inner periphery of the annular opposing seat 67c, or even if the valve body 66 bends, the flow path area between the valve body 66 and the annular opposing seat 67c is restricted to an extremely small value, so that liquid does not easily pass between the valve body 66 and the annular opposing seat 67c, and a difference occurs between the pressure in the expansion side chamber R3 and the pressure in the compression side chamber R4. As with the shock absorber D1, the damping force characteristic of the shock absorber D2 is such that the damping force increases significantly as the expansion / contraction speed increases when the expansion / contraction speed is near 0. In addition, when the shock absorber D2 expands at a low frequency or with a large amplitude, the liquid not only necessarily passes through the first passage P1, but also mainly passes through the second passage P2 among the second passage P2 and the third passage P3, and the pressure in the expansion-side chamber R3 does not reach the valve opening pressure, so the expansion-side bypass damping valve 70a remains closed and the liquid passes through the orifice 70c. When the expansion speed of the shock absorber D2 is in the extremely low speed range, the resistance to the liquid flow provided by the normal valve element 65 is greater than the resistance to the liquid flow provided by the orifice 70c, so the shock absorber D2 generates a damping force by the normal valve element 65. When the shock absorber D2 contracts at a low frequency or with a large amplitude, the liquid mainly passes through the second passage P2, but the pressure in the compression-side chamber R4 does not reach the valve opening pressure, so the compression-side bypass damping valve 70b remains closed and the liquid passes through the orifice 70c. When the contraction speed of the shock absorber D2 is in the extremely low speed range, the resistance that the normal valve element 65 provides to the flow of liquid is greater than the resistance that the orifice 70c provides to the flow of liquid, so that the shock absorber D2 generates a damping force by the normal valve element 65.

[0163] When the shock absorber D2 expands and contracts at a low frequency or with a large amplitude, and the expansion / contraction speed of the shock absorber D2 is in a low-speed range exceeding the extremely low speed range, the valve body 66 of the normal valve element 65 bends significantly, and the resistance to the flow of liquid that the orifice 70c offers becomes greater than the resistance to the flow of liquid that the normal valve element 65 offers, and neither the extension side bypass damping valve 70a nor the compression side bypass damping valve 70b opens. As a result, the shock absorber D2 exerts a damping force mainly through the orifice 70c, and therefore the damping force characteristic of the shock absorber D2 is proportional to the square of the expansion / contraction speed, similar to the shock absorber D1.

[0164] When the shock absorber D2 expands and contracts at a low frequency or with a large amplitude, and the expansion / contraction speed of the shock absorber D2 is in a high-speed range exceeding the low-speed range, the valve body 66 in the normal valve element 65 is largely deflected, the extension side bypass damping valve 70a opens when the shock absorber D2 expands, and the compression side bypass damping valve 70b opens when the shock absorber D2 contracts, and the resistance to the flow of liquid provided by the extension side bypass damping valve 70a or the compression side bypass damping valve 70b becomes greater than the resistance to the flow of liquid provided by the normal valve element 65. Therefore, in this case, the shock absorber D2 exerts a damping force mainly by the extension side bypass damping valve 70a or the compression side bypass damping valve 70b, and therefore the damping force characteristic of the shock absorber D2 is, like the shock absorber D1, a characteristic in which the damping force specific to the leaf valve is approximately proportional to the expansion / contraction speed, but the damping coefficient is lower than the characteristics of the normal valve element 65 and the orifice 70c.

[0165] Next, when the shock absorber D2 expands and contracts at a high frequency or with a small amplitude, and when the shock absorber D2 starts to move and the expansion / contraction speed is in a very low speed range, the valve body 66 in the normal valve element 65 hardly bends and maintains a state in which the outer periphery faces the inner periphery of the annular facing seat 67c, or even if the valve body 66 bends, the flow path area between the annular facing seat 67c is limited to an extremely small value, so that the liquid does not easily pass between the valve body 66 and the annular facing seat 67c, and a difference occurs between the pressure in the expansion-side chamber R3 and the pressure in the contraction-side chamber R4. As a result, the damping force characteristic of the shock absorber D2 becomes such that the damping force rises significantly as the expansion / contraction speed increases near 0, similar to the shock absorber D1. Note that when the shock absorber D2 expands and contracts at a high frequency or with a small amplitude, the liquid always passes through the first passage P1, and mainly passes through the third passage out of the second passage P2 and the third passage P3. Therefore, the shock absorber D2 generates a damping force by the normal valve element 65.

[0166] Furthermore, when the shock absorber D2 expands and contracts at a high frequency or with a small amplitude, and the expansion / contraction speed of the shock absorber D2 is in a speed range exceeding the extremely low speed range, the shock absorber D2 generates a damping force due to the resistance that the third passage P3 itself and the normal valve element 65 offer to the flow of liquid. However, since the normal valve element 65 opens widely, the damping force characteristics of the shock absorber D2 have a smaller damping coefficient compared to the damping force characteristics in the extremely low speed range, and the damping force does not increase significantly even if the expansion / contraction speed increases.

[0167] In this way, whether the shock absorber D2 vibrates at a low frequency or large amplitude or at a high frequency or small amplitude, the entire flow rate of the liquid passing between the expansion-side chamber R3 and the compression-side chamber R4 passes through the normal valve element 65 in the first passage P1, and the normal valve element 65 can raise the damping force at the beginning of the expansion / contraction to suppress the vibration, thereby improving the ride comfort of the vehicle. Also, when the shock absorber D2 vibrates at a low frequency or large amplitude and the expansion / contraction speed becomes high, the vibration can be suppressed by the bypass valve element 70, which is suitable for suppressing vibration at high speeds, so that even if the vibration becomes large, a corresponding damping force is generated, thereby improving the ride comfort of the vehicle.

[0168] Furthermore, when the shock absorber D2 vibrates at a high frequency or with a small amplitude and the expansion / contraction speed is high, the normal valve element 65 opens wide and the damping coefficient becomes small, so that the function of reducing the damping force by bypassing the second passage P2 in the pressure chamber C1 is not hindered, and the damping force when vibrating at a high frequency and high speed, or at a small amplitude and high speed, can be reduced, and the ride comfort of the vehicle can be improved even in such situations.

[0169] The damping valve V2 specifically configured as described above includes a first passage P1 having one end communicated with the extension-side chamber (one chamber) R3, a second passage P2 and a third passage P3 arranged in parallel with each other and communicating the other end of the first passage P1 with the compression-side chamber (other chamber) R4, a normal valve element 65 provided in the first passage P1 and providing resistance to the flow of liquid flowing through the first passage P1, a bypass valve element 70 provided in the second passage P2 and providing resistance to the flow of liquid flowing through the second passage P2, a pressure chamber C1 provided in the third passage P3, a free piston 61 movably accommodated in the pressure chamber C1 and dividing the pressure chamber C1 into a one-side pressure chamber c3 communicated with the extension-side chamber (one chamber) R3 through the first passage P1 and a other-side pressure chamber c4 communicated with the compression-side chamber (other chamber) R4 through the third passage P3, and a spring element 62 generating a biasing force that suppresses displacement of the free piston 61 with respect to the pressure chamber C1.

[0170] According to the damping valve V2 configured in this manner, the entire amount of liquid always flows through the normal valve element 65, and the flow rate of liquid flowing through the bypass valve element 70 and the pressure chamber C1 varies depending on the frequency or amplitude of the vibration of the shock absorber D2. Therefore, according to the shock absorber D2 of this embodiment, unlike conventional damping valves and shock absorbers, a sufficient amount of liquid is passed through the normal valve element 65, making it possible to actively utilize the damping force characteristics of the normal valve element 65, so that when high-frequency vibration or small-amplitude vibration is input, the normal valve element 65 can be fully utilized to exhibit damping force characteristics suitable for that vibration, thereby improving the ride comfort of the vehicle.

[0171] The normal valve element 65 in the damping valve V2 of this embodiment includes an annular valve body 66 having an inner circumferential side as a fixed end and an outer circumferential side as a free end, and an annular opposing seat 67c radially opposing the free end of the valve body 66. The bypass valve element 70 includes an extension-side bypass valve (one-side bypass valve) 70a that provides resistance to the flow of liquid from the extension-side chamber (one side chamber) R3 to the compression-side chamber (other side chamber) R4 and has a valve opening pressure higher than that of the normal valve element 65, a compression-side bypass valve (the other side bypass valve) 70b that provides resistance to the flow of liquid from the compression-side chamber (the other side chamber) R4 to the extension-side chamber (one side chamber) R3 and has a valve opening pressure higher than that of the normal valve element 65, and an orifice 70c that provides resistance to the flow of liquid traveling between the extension-side chamber (one side chamber) R3 and the compression-side chamber (other side chamber) R4.

[0172] According to the damping valve V2 configured in this manner, the valve body 66 can be opened by bending in both directions in the axial direction with respect to the annular opposing seat 67c. Therefore, one valve body 66 can exhibit a damping force while allowing a bidirectional flow of liquid between the extension-side chamber (one chamber) R3 and the compression-side chamber (the other chamber) R4. The valve body 66 is compact and can be easily applied to the shock absorber D2. By making the annular gap between the valve body 66 and the annular opposing seat 67c extremely small, the damping force can be raised at the beginning of the expansion / contraction of the shock absorber D2 regardless of the frequency or the amplitude of the vibration, and the vibration can be suppressed, thereby improving the ride comfort of the vehicle. When the shock absorber D2 vibrates at a low frequency or with a large amplitude and the expansion / contraction speed becomes high, the vibration can be suppressed by the extension-side bypass valve (one side bypass valve) 70b or the compression-side bypass valve (the other side bypass valve) 70b, which are suitable for suppressing vibration at high speeds. Therefore, even if the vibration becomes large, a corresponding damping force can be generated, thereby improving the ride comfort of the vehicle. Furthermore, when the shock absorber D2 vibrates at a high frequency or with a small amplitude and the expansion / contraction speed of the shock absorber D2 reaches a high speed range, the valve body 66 does not bend significantly and the damping force does not become excessively high. Therefore, the effect of reducing the damping force by utilizing the third passage P3 when high frequency or small amplitude vibration is input is not impaired.

[0173] Also, in the specific shock absorber D2, the normal valve element 65 in the damping valve V2 may be set to provide a greater resistance to the flow of liquid than the bypass valve element 70 when the liquid passes through at a flow rate less than a predetermined flow rate, and to provide a smaller resistance to the flow of liquid than the bypass valve element 70 when the liquid passes through at a flow rate greater than the predetermined flow rate. According to the damping valve V2 configured in this manner, the damping force characteristics of the normal valve element 65 are adapted to suppress vibrations input when high-frequency, small-amplitude vibrations are input or when the vehicle is traveling on a relatively smooth road surface, and the damping force characteristics of the bypass valve element 70 are adapted to suppress vibrations with large amplitudes and low frequencies, thereby improving the ride comfort of the vehicle.

[0174] Furthermore, in the shock absorber D2 of this embodiment, the normal valve element 65 in the damping valve V2 is set to provide a higher resistance to the flow of liquid passing therethrough than the bypass valve element 70 when the moving speed of the piston 51 relative to the cylinder 50 is in the extremely low speed range, and to provide a lower resistance than the bypass valve element 70 when the moving speed of the piston 51 relative to the cylinder 50 exceeds the extremely low speed range. According to the shock absorber D2 configured in this manner, the damping force characteristics of the normal valve element 65 are made suitable for suppressing vibrations input when high-frequency, small-amplitude vibrations are input or when the vehicle is traveling on a relatively smooth road surface, and the damping force characteristics of the bypass valve element 70 are made suitable for suppressing vibrations with large amplitude and low frequency, thereby improving the ride comfort of the vehicle.

[0175] In the specific damping valves V1, V2, the normal valve elements 35, 65 are structured so that the inner circumference of the valve body 36, 66 is a fixed end and the outer circumference is a free end, and the annular opposing seats 37c, 67c are opposed to the outer circumference of the valve body 36, 66. However, a structure may be adopted in which the outer circumference of the annular valve body is a fixed end and the inner circumference is a free end, and an annular opposing seat is provided on the inside of the valve body to face the inner surface of the valve body.

[0176] In addition, in the specific damping valves V1, V2, the normal valve elements 35, 65 and the bypass valve elements 40, 70 are configured with valves having different structures, but may be configured with valves having the same structure. Therefore, for example, the normal valve elements 35, 65 and the bypass valve elements 40, 70 may both be valves having extension side and compression side leaf valves. Also, the normal valve elements 35, 65 and the bypass valve elements 40, 70 may both be valves other than leaf valves.

[0177] Although the preferred embodiment of the present invention has been described in detail above, modifications, variations and changes can be made without departing from the scope of the appended claims. [Explanation of symbols]

[0178] 1,35,65···service valve element, 2,40,70···bypass valve element, 3,31,61···free piston, 4,32,62···spring element, 10,20,50···cylinder, 11,21,51···piston, 12,22,52···piston rod, 36,66···valve body, 37c,67c···annular counter seat, 40a···rebound side bypass valve (bypass valve on the other side), 40b···compression side bypass valve (bypass valve on one side), 40c,70c···orifice sice, 70a... extension side bypass valve (bypass valve on one side), 70b... compression side bypass valve (bypass valve on the other side), C, C1... pressure chamber, c1, c3... one side pressure chamber, c2, c4... other side pressure chamber, D, D1, D2... shock absorber, P1... first passage, P2... second passage, P3... third passage, R1... extension side chamber (other chamber), R2... compression side chamber (one chamber), R3... extension side chamber (one chamber), R4... compression side chamber (other chamber), V, V1, V2... damping valve

Claims

1. A first passage, one end of which is connected to one of the chambers; a second passage and a third passage arranged in parallel with each other and each communicating the other end of the first passage with the other chamber; a normal valve element disposed in the first passageway to provide resistance to the flow of liquid through the first passageway; a bypass valve element disposed in the second passageway to provide resistance to the flow of liquid through the second passageway; a pressure chamber provided in the third passage; a free piston movably accommodated within the pressure chamber and dividing the pressure chamber into a one-side pressure chamber communicating with the one chamber via the first passage and a other-side pressure chamber communicating with the other chamber via the third passage; a spring element that generates a biasing force that suppresses the displacement of the free piston relative to the pressure chamber. Damping valve.

2. The normal valve element provides a greater resistance to the flow of liquid than the bypass valve element when the liquid is passing through at a flow rate less than a predetermined flow rate, and provides a lesser resistance to the flow of liquid than the bypass valve element when the liquid is passing through at a flow rate greater than a predetermined flow rate.

2. The damping valve according to claim 1 .

3. The normal valve element has an annular valve body with one of an inner peripheral side and an outer peripheral side being a fixed end and the other being a free end, and an annular opposing seat radially opposing the free end of the valve body, The bypass valve element comprises: a bypass valve on one side that provides resistance to the flow of liquid from the one chamber to the other chamber and has a valve opening pressure higher than that of the normal valve element; a bypass valve on the other side that provides resistance to the flow of liquid from the other chamber to the one chamber and has a valve opening pressure higher than that of the normal valve element; and an orifice that provides resistance to the flow of liquid between the one chamber and the other chamber.

2. The damping valve according to claim 1 .

4. A cylinder; a piston slidably inserted into the cylinder and dividing the inside of the cylinder into an expansion-side chamber and a compression-side chamber; a piston rod that is movably inserted into the cylinder and has one end connected to the piston; and a damping valve according to any one of claims 1 to 3, One of the one chamber and the other chamber is the expansion-side chamber, The other of the one chamber and the other chamber is the pressure side chamber. A shock absorber comprising:

5. The normal valve element provides a higher resistance to the flow of the liquid passing therethrough than the bypass valve element when the moving speed of the piston relative to the cylinder is in a very low speed range, and provides a lower resistance than the bypass valve element when the moving speed of the piston relative to the cylinder exceeds the very low speed range.

5. The shock absorber according to claim 4.

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