Buffer

Abstract

To provide a shock absorber which is small and lightweight, can reduce manufacturing costs, and can be easily mounted on a vehicle. [Solution] A shock absorber D of the present invention includes a cylinder 1, a cylindrical piston rod 2 inserted into the cylinder 1 so as to be axially movably, a piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be axially movably and dividing the inside of the cylinder 1 into an extension side chamber R1 and a compression side chamber R2, a cap 10 closing the compression side chamber end of the cylinder 1, a cylindrical inner rod 4 extending from the cap 10 and inserted into the compression side chamber R2 to slidably fit into the piston rod 2, a main damping passage M providing resistance to the flow of liquid traveling between the extension side chamber R1 and the compression side chamber R2, a bypass passage B bypassing the main damping passage and communicating between the extension side chamber R1 and the compression side chamber R2 via the piston rod 2 and the inner rod 4, and a damping force adjustment valve 21 provided in the bypass passage B.

Description

[Technical field]

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

[0002] A shock absorber is used, for example, by being interposed between the body and wheels of a saddle-type vehicle, and suppresses vibration between the body and wheels by the damping force generated when the shock absorber expands or contracts.

[0003] Such a shock absorber includes, for example, a cylinder, a piston movably inserted into the cylinder to divide the inside of the cylinder into an extension-side chamber and a compression-side chamber filled with hydraulic oil, a piston rod movably inserted into the cylinder and connected to the piston, a tank for storing hydraulic oil, a hard-side damping element provided on the piston to communicate between the extension-side chamber and the compression-side chamber and to provide resistance to the flow of hydraulic oil passing through, a bypass path that bypasses the hard-side damping element to communicate between the extension-side chamber and the compression-side chamber, and a solenoid valve and a soft-side damping element provided in series to the bypass path (for example, see Patent Document 1).

[0004] In a shock absorber configured in this manner, the opening area of ​​the bypass passage can be adjusted using a solenoid valve to adjust the distribution ratio of the flow rate of hydraulic oil passing through the hard damping element and the soft damping element, thereby providing a wide damping force adjustment range and outputting a damping force optimal for suppressing vehicle vibrations. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-143685 A Summary of the Invention [Problem to be solved by the invention]

[0006] Conventional shock absorbers have a structure in which an outer shell is provided around the outer periphery of a cylinder, a bypass passage is provided between the cylinder and the outer shell to connect the expansion side chamber and the compression side chamber outside the cylinder, and a solenoid valve and a soft side damping element are provided in the bypass passage.

[0007] As described above, conventional shock absorbers require a large-diameter outer shell to cover the cylinder when forming a bypass path, which increases the shock absorber size, weight, and manufacturing costs. If the shock absorber is made larger, it may be difficult to install it in some vehicles due to the limited mounting space, and the increased weight leads to increased fuel consumption, so there is a demand for lighter shock absorbers.

[0008] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a shock absorber which is small and lightweight, can reduce manufacturing costs, and can be easily mounted on a vehicle. [Means for solving the problem]

[0009] In order to solve the above problems, the shock absorber of the present invention includes a cylinder, a cylindrical piston rod inserted into the cylinder so as to be axially movably, a piston connected to the piston rod and inserted into the cylinder so as to be axially movably, and dividing the inside of the cylinder into an extension-side chamber and a compression-side chamber, a cap closing the compression-side chamber end of the cylinder, a cylindrical inner rod extending from the cap, inserted into the compression-side chamber, and slidably fitted into the piston rod, a main damping passage providing resistance to the flow of liquid moving between the extension-side chamber and the compression-side chamber, a bypass passage bypassing the main damping passage and communicating between the extension-side chamber and the compression-side chamber via the inside of the piston rod and the inside of the inner rod, and a damping force adjustment valve provided in the bypass passage.

[0010] In a shock absorber configured in this manner, the bypass passage bypasses the main damping passage and connects the expansion side chamber and the compression side chamber via the inside of the piston rod and the inside of the inner rod inserted into the piston rod, and since the bypass passage is provided inside the cylinder, a large-diameter outer shell covering the cylinder is not required to form the bypass passage.

[0011] In addition, the cross-sectional area of ​​the annular gap between the inner circumference of the cylinder and the outer circumference of the piston rod may be made larger than the cross-sectional area of ​​the inner rod. According to the shock absorber configured in this manner, the liquid moves from the expansion-side chamber to the compression-side chamber during the extension operation, and the liquid moves from the compression-side chamber to the expansion-side chamber during the contraction operation, so that the flow of the liquid is the same as that of a conventional shock absorber, and it is easy to set the damping force characteristics.

[0012] Furthermore, the shock absorber may include a tank for storing liquid, a discharge passage connecting the compression side chamber and the tank, a suction passage connecting the tank and the compression side chamber, a compression side damping valve provided in the discharge passage for providing resistance to the flow of liquid from the compression side chamber to the tank, and a suction side valve provided in the suction passage for allowing the flow of liquid from the tank to the compression side chamber.

[0013] With a shock absorber configured in this manner, not only can the damping force be adjusted to a high or low level while securing a damping force adjustment range by adjusting the flow distribution ratio between the main damping passage and the bypass passage using the damping force adjustment valve, but since the discharge passage is provided with a compression side damping valve and the suction passage is provided with an suction side valve, the pressure in the compression side chamber can be increased to above the tank pressure during contraction, thereby generating a higher damping force than before. Effect of the Invention

[0014] According to the shock absorber of the present invention, it is possible to reduce manufacturing costs due to its small size and light weight, and it is possible to improve mountability on a vehicle. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view of a shock absorber according to one embodiment. [Diagram 2] FIG. 2 is a diagram showing the damping force characteristics of the shock absorber in one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention will be described below based on the embodiment shown in the drawings. As shown in Fig. 1, a shock absorber D in one embodiment includes a cylinder 1, a cylindrical piston rod 2 inserted into the cylinder 1 so as to be axially movable, a piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be axially movable and dividing the cylinder 1 into an expansion side chamber R1 and a compression side chamber R2, a cap 10 closing the compression side chamber end of the cylinder 1, a cylindrical inner rod 4 extending from the cap 10 and inserted into the compression side chamber R2 to be slidably fitted into the piston rod 2, a main damping passage M providing resistance to the flow of liquid moving between the expansion side chamber R1 and the compression side chamber R2, a bypass passage B bypassing the main damping passage and communicating the expansion side chamber R1 and the compression side chamber R2 via the piston rod 2 and the inner rod 4, and a damping force adjustment valve 21 provided in the bypass passage B.

[0017] Although not shown, this shock absorber D is used by being interposed between the body and the rear wheel of a saddle-type vehicle such as a motorcycle, and suppresses vibrations of the body and the rear wheel. Note that the shock absorber D may be used to suppress vibrations of vehicles other than saddle-type vehicles.

[0018] Below, each part of the shock absorber D will be described in detail. As shown in Fig. 1, the cylinder 1 is cylindrical, with the upper end in Fig. 1 closed by a rod guide 17 and the lower end in Fig. 1 closed by a cap 10. A screw portion 1a is provided at a position slightly above the lower end of the cylinder 1 in Fig. 1, and the cap 10 is screwed to the screw portion 1a and attached to the lower end of the cylinder 1 in Fig. 1.

[0019] 1 is annular and includes an annular seal ring 17a on its outer periphery which closely contacts the inner periphery of the cylinder 1, and an annular seal ring 17b and annular bush 17c on its inner periphery which slide against the outer periphery of the piston rod 2. The rod guide 17 is restricted from moving upward in FIG. 1 with respect to the cylinder 1 by a C-ring 24 attached to the inner periphery of the upper end of the cylinder 1 in FIG.

[0020] The piston rod 2, which is movably inserted into the cylinder 1, is inserted through the seal ring 17b and bush 17c of the rod guide 17 attached to the inner periphery of the cylinder 1 in this manner. The rod guide 17 supports the piston rod 2 with the bush 17c to guide the axial movement of the piston rod 2 relative to the cylinder 1, and seals the outer periphery of the piston rod 2 with a seal ring 17b. A seal ring 17a is tightly attached to the inner periphery of the cylinder 1 to seal and prevent leakage of liquid from between the rod guide 17 and the cylinder 1. The upper end in FIG. 1, which is the tip of the piston rod 2, protrudes outward from the upper end in FIG. 1 of the cylinder 1 via the inner periphery of the rod guide 17.

[0021] The piston rod 2 is cylindrical and includes a small diameter portion 2a at its lower end in Fig. 1 whose outer diameter is smaller than that of its upper portion, and a piston 3 is attached to its outer periphery, a threaded portion 2b at the outer periphery of the small diameter portion 2a at its lower end in Fig. 1, and a through hole 2c that penetrates radially through a side portion above the small diameter portion 2a in Fig. 1. A bracket 6 that can be connected to the body of a saddle-type vehicle is attached to the upper end of the piston rod 2 in Fig. 1.

[0022] A piston 3 attached to a piston rod 2 is inserted in the cylinder 1 so as to be movable in the axial direction, and the inside of the cylinder 1 is divided by the piston 3 into an extension-side chamber R1 above the piston 3 and a compression-side chamber R2 below the piston 3. The extension-side chamber R1 and the compression-side chamber R2 are filled with a liquid such as hydraulic oil. In this embodiment, the liquid is hydraulic oil, but it may be liquid other than hydraulic oil, such as water or an aqueous solution. The through hole 2c of the piston rod 2 opens upward in FIG. 1 from the small diameter portion 2a on which the piston 3 is attached and faces the extension-side chamber R1, so that the inside of the piston rod 2 is communicated with the extension-side chamber R1 via the through hole 2c.

[0023] The piston 3 is annular and is attached to the outer periphery of the small diameter portion 2a of the piston rod 2, and has an expansion side port 3a and a compression side port 3b that communicate the expansion side chamber R1 and the compression side chamber R2 in parallel, respectively. An expansion side main damping valve 13 that is annular and is attached to the outer periphery of the small diameter portion 2a and opens and closes the expansion side port 3a is stacked at the lower end of the piston 3 in FIG. 1. Also, a compression side main damping valve 14 that is annular and is attached to the outer periphery of the small diameter portion 2a and opens and closes the compression side port 3b is stacked at the upper end of the piston 3 in FIG. 1. The piston 3, the expansion side main damping valve 13, and the compression side main damping valve 14 are fitted to the outer periphery of the small diameter portion 2a of the piston rod 2, and are fixed to the piston rod 2 by a piston nut 15 that is screwed to the lower end of the small diameter portion 2a.

[0024] In the shock absorber D of this embodiment, the expansion-side main damping valve 13 is a laminated leaf valve that is configured by stacking a plurality of annular plates at the lower end of the piston 3 in FIG. 1, and is fixed at the inner circumferential side and opens the expansion-side port 3a when the outer circumferential side is deflected by the pressure of the expansion-side chamber R1. The expansion-side main damping valve 13 can open and close the expansion-side port 3a, and opens the valve when the shock absorber D expands to provide resistance to the flow of liquid passing through the expansion-side port 3a from the expansion-side chamber R1 to the compression-side chamber R2, and closes the valve when the shock absorber D contracts to block the expansion-side port 3a. Note that the expansion-side main damping valve 13 may be a damping valve other than a laminated leaf valve as long as it is a damping valve that provides resistance to the flow of liquid from the expansion-side chamber R1 to the compression-side chamber R2 and exerts a damping force that hinders the expansion of the shock absorber D when the shock absorber D expands.

[0025] On the other hand, in the shock absorber D of this embodiment, the compression side main damping valve 14 is a laminated leaf valve that is configured by laminating a plurality of annular plates on the upper end of the piston 3 in FIG. 1, and is fixed on the inner circumferential side, and opens the compression side port 3b when the outer circumferential side is deflected by the pressure of the compression side chamber R2. The compression side main damping valve 14 can open and close the compression side port 3b, and opens the valve when the shock absorber D contracts to provide resistance to the flow of liquid passing through the compression side port 3b from the compression side chamber R2 to the expansion side chamber R1, and closes the valve when the shock absorber D expands to block the compression side port 3b. Note that the compression side main damping valve 14 may be a damping valve other than a laminated leaf valve as long as it can provide resistance to the flow of liquid from the compression side chamber R2 to the expansion side chamber R1 and exert a damping force that prevents the shock absorber D from contracting when the shock absorber D contracts. Although not shown, an orifice is provided in parallel with the expansion side main damping valve 13 and the compression side main damping valve 14. The orifice is formed, for example, by a notch provided in an annular plate constituting the expansion side main damping valve 13 and the compression side main damping valve 14, or by a stamping provided on the valve seat of the piston 3 on which the annular plate sits and leaves.

[0026] In this manner, the expansion side port 3a and the compression side port 3b of the piston 3 communicate with the expansion side chamber R1 and the compression side chamber R2. When the expansion side main damping valve 13 and the compression side main damping valve 14 are closed, the orifice provides resistance to the flow of liquid passing through the expansion side port 3a and the compression side port 3b to move between the expansion side chamber R1 and the compression side chamber R2. When the expansion side main damping valve 13 and the compression side main damping valve 14 are open, the expansion side main damping valve 13 provides resistance to the flow of liquid passing through the expansion side port 3a, and the compression side main damping valve 14 provides resistance to the flow of liquid passing through the compression side port 3b. In this embodiment, the expansion side port 3a, the compression side port 3b, the orifice, the expansion side main damping valve 13, and the compression side main damping valve 14 constitute a main damping passage M that provides resistance to the flow of liquid moving between the expansion side chamber R1 and the compression side chamber R2. The main damping passage M may be configured to include only a single passage and a bidirectional valve, such as an orifice or a choke, that is provided in the passage and provides resistance to the flow of liquid reciprocating between the expansion-side chamber R1 and the compression-side chamber R2.

[0027] The cap 10 is cylindrical with a bottom, and has a cylindrical portion 10a and a bottom portion 10b that closes the lower end of the cylindrical portion 10a. The lower end of the cylinder 1 is inserted into the cylindrical portion 10a, and the cap 10 is fixed to the cylinder 1 by screwing a screw portion 10a1 on the inner circumference of the cylindrical portion 10a to a screw portion 1a on the outer circumference of the cylinder 1.

[0028] 1, the cylindrical portion 10a has a threaded portion 10a1 provided on the inner circumference of the upper end, and an annular sealing groove 10a2 provided on the inner circumference below the threaded portion 10a1. A seal ring 20 that comes into close contact with the outer periphery of the cylinder 1 is housed in the sealing groove 10a2 provided on the inner circumference of the cylindrical portion 10a, and the gap between the cap 10 and the cylinder 1 is sealed.

[0029] Next, the bottom 10b of the cap 10 has a recess 10b1 in the center of the upper end in Fig. 1, and the lower end of the cylindrical inner rod 4 in Fig. 1 is inserted into the recess 10b1. A retaining ring 5 that prevents the inner rod 4 from slipping out of the recess 10b1 is provided in the recess 10b1, and the inner rod 4 is held by the cap 10. Also, a seal ring 16 that comes into close contact with the outer periphery of the inner rod 4 is provided in the recess 10b1, and the gap between the cap 10 and the inner rod 4 is sealed.

[0030] In this way, the inner rod 4 extends from the bottom 10b of the cap 10 and is inserted into the compression side chamber R2, and is slidably inserted into the piston rod 2. More specifically, the outer diameter of the inner rod 4 is smaller than the inner diameter of the piston rod 2, and the inner rod 4 is slidably inserted into a cylindrical bush 2d attached to the inner periphery of the lower end of the small diameter portion 2a of the piston rod 2 in FIG. 1. Therefore, when the piston rod 2 is displaced relative to the cylinder 1, the piston rod 2 is also displaced relative to the inner rod 4 held by the cap 10. In addition, the inner rod 4 is loosely fitted in the recess 10b1, and although it is held by the cap 10 by the retaining ring 5, a small radial deflection at the upper end in FIG. 1 is allowed, and when inserted into the piston rod 2, it can smoothly advance and retreat into the piston rod 2 following the piston rod 2. The inside of the inner rod 4 is communicated with the extension side chamber R1 through the inside of the piston rod 2 and the through hole 2c, and forms an inner rod passage Pr together with the inside of the piston rod 2.

[0031] The cross-sectional area of ​​the annular gap between the inner periphery of the cylinder 1 and the outer periphery of the piston rod 2 is larger than the cross-sectional area of ​​the inner rod 4, i.e., the cross-sectional area of ​​the cross section obtained by cutting the inner rod 4 horizontally.

[0032] 1, a bracket 10c is provided at the lower end of the bottom portion 10b of the cap 10, and the lower end of the shock absorber D can be connected to a swing arm that holds the rear wheel of a saddle-riding type vehicle via the bracket 10c. Note that, although the present embodiment has been described in which the piston rod 2 is connected to the body of the saddle-riding type vehicle and the cap 10 is connected to the rear wheel of the saddle-riding type vehicle, the piston rod 2 may be connected to the rear wheel of the saddle-riding type vehicle and the cap 10 may be connected to the body of the saddle-riding type vehicle.

[0033] Furthermore, the cap 10 includes a tank holding portion 10d that holds a tank 18 that extends radially from the side of the bottom portion 10b and is disposed parallel to the cylindrical portion 10a. The tank 18 is cylindrical, with its lower end integrally connected to the tank holding portion 10d, and houses a bladder 19 therein. The tank 18 is partitioned by the bladder 19 into a liquid chamber L that is filled with liquid and an air chamber G that is filled with gas. Note that gas is sealed in the air chamber G so that the pressure in at least the air chamber G is equal to or higher than atmospheric pressure when the shock absorber D is fully extended. Note that the partition between the liquid chamber L and the air chamber G in the tank 18 may be formed by using an elastic partition such as the bladder 19 or a diaphragm, or by using a free piston.

[0034] In addition, in this embodiment, as shown in Figure 1, the cap 10 is provided with an intra-cap passage Pc that opens from the lower end of the recess 10b1 in Figure 1 and leads to the end 10b2 facing the pressure side chamber R2 of the bottom 10b, and a discharge passage EP and a suction passage SP that open from the end 10b2 of the bottom 10b and lead to the liquid chamber L of the tank 18.

[0035] One end of the cap inner passage Pc is connected to the expansion-side chamber R1 through the rod inner passage Pr, and the other end is connected to the compression-side chamber R2. Together with the rod inner passage Pr, the cap inner passage Pc forms a bypass path B that bypasses the main damping passage M and connects the expansion-side chamber R1 and the compression-side chamber R2.

[0036] Furthermore, the bottom 10b of the cap 10 is provided with a damping force adjustment valve 21, an extension side low speed valve 22, and a compression side low speed valve 23, which are arranged in the middle of the cap internal passage Pc constituting part of the bypass path B, a compression side damping valve 30 arranged in the middle of the exhaust passage EP, and an suction check valve 31 as an suction side valve arranged in the middle of the suction passage SP.

[0037] The damping force control valve 21 is installed in series with the low speed extension side valve 22 and the low speed compression side valve 23 on the bypass path B, and the low speed extension side valve 22 and the low speed compression side valve 23 are installed in parallel with each other on the bypass path B.

[0038] In this embodiment, the damping force control valve 21 includes a valve body 21a capable of opening and closing the cap inner passage Pc forming a part of the bypass path B, a spring 21b for biasing the valve body 21a to close, and a solenoid 21c attached to the side of the bottom 10b and capable of generating a thrust for pushing the valve body 21a in the valve opening direction against the biasing force of the spring 21b, and is an electromagnetic valve whose degree of opening can be adjusted according to the amount of current supplied to the solenoid 21c and which closes when the current to the solenoid 21c is cut off. Note that the damping force control valve 21 is an electromagnetic valve whose degree of opening can be adjusted in this way, but it may be an electromagnetic valve whose valve opening pressure can be adjusted, or it may be a damping force control valve whose valve opening degree or valve opening pressure is adjusted manually.

[0039] The low speed extension side valve 22 is a damping valve that opens to provide resistance to the flow of liquid from the extension side chamber R1 to the compression side chamber R2, and closes to block the passage of liquid from the compression side chamber R2 to the extension side chamber R1. The opening pressure of the low speed extension side valve 22 is lower than that of the main extension side damping valve 13, and when the extension speed of the shock absorber D is low, the valve opens prior to the main extension side damping valve 13 to generate a damping force.

[0040] The compression side low speed valve 23 is a damping valve that opens to provide resistance to the flow of liquid from the compression side chamber R2 to the expansion side chamber R1, and closes to block the passage of liquid from the expansion side chamber R1 to the compression side chamber R2. The valve opening pressure is lower than that of the compression side main damping valve 14, and when the contraction speed of the shock absorber D is low, the valve opens prior to the compression side main damping valve 14 to generate a damping force.

[0041] In this embodiment, the low speed extension valve 22, which allows only the flow of liquid from the expansion side chamber R1 to the compression side chamber R2 and provides resistance to the flow of liquid passing through, and the low speed compression valve 23, which allows only the flow of liquid from the compression side chamber R2 to the expansion side chamber R1 and provides resistance to the flow of liquid passing through, are provided in the cap inner passage Pc. These low speed extension valve 22 and low speed compression valve 23 are defined as low speed valves. However, any valve that allows the flow of liquid back and forth between the expansion side chamber R1 and the compression side chamber R2 and provides resistance to the flow of liquid passing through may be defined as the low speed valve.

[0042] The compression side damping valve 30 is provided in the discharge passage EP and serves as a damping valve that opens against the flow of liquid from the compression side chamber R2 toward the tank 18 to provide resistance to the flow of the liquid, and closes against the flow of liquid from the tank 18 toward the compression side chamber R2 to block the discharge passage EP. The suction check valve 31 as the suction side valve is provided in the suction passage SP and serves as a damping valve that opens against the flow of liquid from the tank 18 toward the compression side chamber R2 to allow the liquid to pass without providing almost no resistance to the flow of the liquid, but closes against the flow of liquid from the compression side chamber R2 toward the tank 18 to block the suction passage SP. As described above, the suction side valve in this embodiment is the suction check valve 31 provided in the discharge passage SP to allow only the flow of liquid from the tank 18 toward the compression side chamber R2, but may be a damping valve provided in the discharge passage SP to provide resistance to the flow of liquid from the tank 18 toward the compression side chamber R2.

[0043] The shock absorber D of this embodiment is configured as described above, and the operation of the shock absorber D will be described below. When the shock absorber D is expanded, the piston rod 2 retracts from the cylinder 1 and the piston 3 compresses the expansion-side chamber R1. Then, the liquid in the expansion-side chamber R1 passes through an orifice (not shown) in the main damping passage M, the expansion-side main damping valve 13 in the main damping passage M, or passes through the bypass passage B partially formed by the piston rod 2 and the inner rod 4 and moves to the compression-side chamber R2 through the expansion-side low speed valve 22. In addition, the amount of liquid obtained by subtracting the displacement volume of the inner rod 4 retracted from the piston rod 2 from the displacement volume of the piston rod 2 retracted from the cylinder 1 is insufficient in the cylinder 1, so the suction check valve 31 opens and the insufficient liquid is supplied from the tank 18 to the cylinder 1 through the suction passage SP. As described above, the cross-sectional area of ​​the annular gap between the inner circumference of the cylinder 1 and the outer circumference of the piston rod 2 is larger than the cross-sectional area of ​​the inner rod 4. Therefore, when the shock absorber D expands, the liquid always moves from the expansion-side chamber R1 to the compression-side chamber R2 through the main damping passage M or the bypass passage B.

[0044] Resistance is applied to the flow of liquid from the expansion-side chamber R1 to the compression-side chamber R2 by the main damping passage M or the low-speed expansion-side valve 22, and the shock absorber D generates a damping force that hinders the expansion-side operation due to the resistance. Regarding the resistance applied when the liquid passes through the main damping passage M, when the expansion speed of the shock absorber D is in the low-speed range, the expansion-side main damping valve 13 does not open and resistance is applied to the flow of the liquid by an orifice not shown, and when the expansion speed of the shock absorber D is in the high-speed range, the expansion-side main damping valve 13 opens and resistance is applied to the flow of the liquid by the expansion-side main damping valve 13. When the amount of electricity to the damping force adjustment valve 21 is changed, the distribution ratio of the liquid passing through the main damping passage M and the low-speed expansion-side valve 22 during the expansion operation of the shock absorber D changes.

[0045] Specifically, during the extension operation of the shock absorber D, when the damping force control valve 21 is open, the liquid passes through the main damping passage M and the low speed extension side valve 22, but when the damping force control valve 21 is closed, the bypass passage B is blocked and the liquid cannot pass through the low speed extension side valve 22, but passes only through the main damping passage M and moves from the extension side chamber R1 to the compression side chamber R2. In addition, when a current is supplied to the damping force control valve 21 to open it and the amount of current supplied is increased, the degree of opening of the damping force control valve 21 increases and the flow rate of liquid passing through the bypass passage B increases, so that the proportion of liquid passing through the low speed extension side valve 22 increases and the proportion of liquid passing through the main damping passage M decreases. Therefore, the damping force characteristic generated by the shock absorber D during the extension operation when the extension speed is in the low speed range is changed in the range from the soft characteristic generated mainly by the low speed extension valve 22 shown by the dashed line in Fig. 2 to the hard characteristic generated mainly by the main damping passage M shown by the solid line in Fig. 2 by adjusting the amount of current supplied to the damping force control valve 21, as shown in Fig. 2. Also, during the extension operation when the extension speed is in the high speed range, the extension side main damping valve 13 opens widely regardless of the opening degree of the damping force control valve 21, and the liquid passes preferentially through the main damping passage M, so that the shock absorber D generates a damping force by the extension side main damping valve 13. Note that, when the suction side valve is a damping valve instead of the suction check valve 31, resistance is applied to the flow of the liquid when the liquid moves from the tank 18 to the cylinder 1 through the suction passage SP, thereby reducing the pressure in the compression side chamber R2 and generating a higher damping force.

[0046] On the other hand, when the shock absorber D is contracted, the piston rod 2 enters the cylinder 1 and the piston 3 compresses the compression side chamber R2. Then, the liquid in the compression side chamber R2 passes through an orifice (not shown) in the main damping passage M, the compression side main damping valve 14 in the main damping passage M, or passes through a bypass passage B partially formed by the piston rod 2 and the inner rod 4, and moves to the extension side chamber R1 through the compression side low speed valve 23. Also, since the amount of liquid obtained by subtracting the displacement volume of the inner rod 4 entering the piston rod 2 from the displacement volume of the piston rod 2 entering the cylinder 1 becomes excessive in the cylinder 1, the excess liquid passes through the compression side damping valve 30 from the compression side chamber R2 and is discharged from the compression side chamber R2 to the tank 18. As described above, the cross-sectional area of ​​the annular gap between the inner circumference of the cylinder 1 and the outer circumference of the piston rod 2 is larger than the cross-sectional area of ​​the inner rod 4. Therefore, when the shock absorber D contracts, excess liquid always forms in the cylinder 1 and moves from the cylinder 1 to the tank 18.

[0047] Resistance is applied to the flow of liquid from the compression side chamber R2 to the expansion side chamber R1 by the main damping passage M or the compression side low speed valve 23, and resistance is applied to the flow of liquid from the compression side chamber R2 to the tank 18 by the compression side damping valve 30, and a compression side damping force is generated due to each of the resistances described above. Regarding the resistance applied when the liquid passes through the main damping passage M, when the contraction speed of the shock absorber D is in the low speed range, the compression side main damping valve 14 does not open and resistance is applied to the flow of the liquid by an orifice not shown, and when the contraction speed of the shock absorber D is in the high speed range, the compression side main damping valve 14 opens and resistance is applied to the flow of the liquid by the compression side main damping valve 14. When the amount of electricity to the damping force adjusting valve 21 is changed, the distribution ratio of the liquid passing through the main damping passage M and the compression side low speed valve 23 during the contraction operation of the shock absorber D changes.

[0048] Specifically, during the contraction operation of the shock absorber D, when the damping force control valve 21 is open, the liquid passes through the main damping passage M and the compression side low speed valve 23, but when the damping force control valve 21 is closed, the bypass passage B is blocked and the liquid cannot pass through the compression side low speed valve 23, and passes only through the main damping passage M to move from the compression side chamber R2 to the expansion side chamber R1. In addition, when a current is supplied to the damping force control valve 21 to open it and the amount of current supplied is increased, the degree of opening of the damping force control valve 21 increases and the flow rate of liquid passing through the bypass passage B increases, so that the proportion of liquid passing through the compression side low speed valve 23 increases and the proportion of liquid passing through the main damping passage M decreases. Therefore, when the contraction speed is in the low-speed range during contraction, the damping force characteristics generated by the shock absorber D are changed within a range from a soft characteristic in which resistance is applied to the fluid flowing from the compression side chamber R2 to the expansion side chamber R1 by the compression side low speed valve 23 shown by the dashed line in Fig. 2 to a hard characteristic in which resistance is applied by the main damping passage M shown by the solid line in Fig. 2, by adjusting the amount of current supplied to the damping force control valve 21, as shown in Fig. 2. Also, when the contraction speed is in the high-speed range during contraction, the compression side main damping valve 14 opens widely regardless of the opening degree of the damping force control valve 21, and the fluid flowing from the compression side chamber R2 to the expansion side chamber R1 passes preferentially through the compression side main damping valve 14, so that the shock absorber D generates a damping force by the compression side main damping valve 14. Furthermore, when the shock absorber D is contracting, excess liquid in the cylinder 1 passes through the compression side damping valve 30 and flows from the compression side chamber R2 to the tank 18. Therefore, the pressure in the compression side chamber R2 can be increased to a pressure higher than the tank pressure by the compression side damping valve 30, and the shock absorber D can generate a higher compression side damping force than conventional shock absorbers.

[0049] In addition, in the shock absorber D of this embodiment, the low speed extension side valve 22 and the low speed compression side valve 23 are provided as low speed valves, but it is also possible to eliminate the low speed extension side valve 22 and the low speed compression side valve 23 and adjust the damping force by changing the opening degree of the damping force control valve 21.

[0050] As described above, the shock absorber D of this embodiment includes the cylinder 1, the cylindrical piston rod 2 inserted into the cylinder 1 so as to be axially movable, the piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be axially movable and dividing the inside of the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2, the cap 10 closing the compression-side chamber end of the cylinder 1, the cylindrical inner rod 4 extending from the cap 10 and inserted into the compression-side chamber R2 to be slidably fitted into the piston rod 2, the main damping passage M providing resistance to the flow of liquid moving between the extension-side chamber R1 and the compression-side chamber R2, the bypass passage B bypassing the main damping passage and communicating the extension-side chamber R1 and the compression-side chamber R2 via the inside of the piston rod 2 and the inside of the inner rod 4, and the damping force adjustment valve 21 provided in the bypass passage B.

[0051] In the shock absorber D configured in this manner, the bypass path B bypasses the main damping passage M and communicates the expansion-side chamber R1 and the compression-side chamber R2 via the piston rod 2 and the inner rod 4 inserted into the piston rod 2, and since the bypass path B is provided in the cylinder 1, a large-diameter outer shell that covers the cylinder 1 is not required to form the bypass path B. Therefore, according to the shock absorber D of this embodiment, since an outer shell is not required, the shock absorber D is small and lightweight, and the manufacturing cost can be reduced, and the shock absorber D can be installed in a vehicle with a limited installation space, so that the mountability on the vehicle can be improved.

[0052] In addition, in the shock absorber D of this embodiment, the cross-sectional area of ​​the annular gap between the inner circumference of the cylinder 1 and the outer circumference of the piston rod 2 is larger than the cross-sectional area of ​​the inner rod 4. According to the shock absorber D configured in this manner, liquid moves from the expansion-side chamber R1 to the compression-side chamber R2 during the extension operation, and liquid moves from the compression-side chamber R2 to the expansion-side chamber R1 during the contraction operation, so that the flow of liquid is the same as that of a conventional shock absorber, and it is easy to set the damping force characteristics.

[0053] Furthermore, the shock absorber D of this embodiment is equipped with a tank 18 for storing liquid, a discharge passage EP connecting the compression side chamber R2 and the tank 18, a suction passage SP connecting the tank 18 and the compression side chamber R2, a compression side damping valve 30 provided in the discharge passage EP to provide resistance to the flow of liquid from the compression side chamber R2 to the tank 18, and a suction check valve (suction side valve) 31 provided in the suction passage SP to allow the flow of liquid from the tank 18 to the compression side chamber R2.

[0054] According to the shock absorber D configured in this manner, not only can the damping force be adjusted high and low while securing the damping force adjustment range by adjusting the flow distribution ratio between the main damping passage M and the bypass passage B with the damping force adjustment valve 21, but also, since the exhaust passage EP is provided with the compression side damping valve 30 and the suction passage SP is provided with the suction check valve (suction side valve) 31, the pressure in the compression side chamber R2 can be increased to above the tank pressure during contraction, thereby generating a higher damping force than before. As described above, according to the shock absorber D of this embodiment, a high damping force can be generated during contraction while securing the damping force adjustment range.

[0055] Moreover, the shock absorber D of this embodiment is provided with an extension-side low speed valve 22 and a compression-side low speed valve 23 that are provided in series with the damping force control valve 21 in the bypass path B and provide resistance to the flow of liquid moving between the extension-side chamber R1 and the compression-side chamber R2. According to the shock absorber D configured in this manner, the damping force control valve 21 is opened to enable the extension-side low speed valve 22 and the compression-side low speed valve 23 in the bypass path B, thereby making it possible to adjust the damping force in the low extension / contraction speed range and generate a damping force suitable for driving a saddle-type vehicle on a good road with few bumps and no vibration at high speed.

[0056] 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]

[0057] 1 Cylinder, 2 Piston rod, 3 Piston, 4 Inner rod, 10 Cap, 18 Tank, 30 Compression side damping valve, 31 Suction check valve (suction side valve), B Bypass path, D Shock absorber, EP Exhaust passage, M Main damping passage, R1 Rebound side chamber, R2 Compression side chamber, SP Exhaust passage

Claims

1. A cylinder; A cylindrical piston rod is inserted into the cylinder so as to be axially movable; a piston connected to the piston rod and inserted into the cylinder so as to be axially movably therein, the piston dividing the interior of the cylinder into an expansion-side chamber and a compression-side chamber; A cap that closes a compression side chamber end of the cylinder; a cylindrical inner rod extending from the cap, inserted into the compression-side chamber, and slidably fitted into the piston rod; a main damping passage that provides resistance to the flow of liquid between the expansion-side chamber and the compression-side chamber; a bypass passage that bypasses the main damping passage and communicates between the expansion-side chamber and the compression-side chamber via the piston rod and the inner rod; A damping force adjusting valve provided in the bypass path. A shock absorber characterized by:

2. The cross-sectional area of ​​an annular gap between the inner periphery of the cylinder and the outer periphery of the piston rod is larger than the cross-sectional area of ​​the inner rod.

2. The shock absorber according to claim 1 .

3. A tank for storing liquid; a discharge passage communicating the compression side chamber with the tank; a suction passage communicating between the tank and the compression side chamber; a compression side damping valve provided in the discharge passage to provide resistance to a flow of liquid from the compression side chamber toward the tank; a suction side valve provided in the suction passage to allow liquid to flow from the tank toward the pressure side chamber; 3. The shock absorber according to claim 1 or 2.

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