Shock absorber

Abstract

This shock absorber (D) comprises: a cylinder (1); a cylindrical piston rod (2) which is inserted into the cylinder (1) so as to be movable in the axial direction; a piston (3) which is connected to the piston rod (2) and inserted into the cylinder (1) so as to be movable in the axial direction, and which partitions the interior of the cylinder (1) into an expansion-side chamber (R1) and a compression-side chamber (R2); a cap (10) which closes the end of the cylinder (1) on the compression-side chamber side; a cylindrical inner rod (4) which extends from the cap (10) and is inserted into the compression-side chamber (R2) and slidably fits into the piston rod (2); a main damping passage (M) which imparts resistance to the flow of the liquid going back and forth between the expansion-side chamber (R1) and the compression-side chamber (R2); a bypass passage (B) which bypasses the main damping passage (M) and which establishes communication between the expansion-side chamber (R1) and the compression-side chamber (R2) through the interior of the piston rod (2) and the inner rod (4); and a damping force adjustment valve (21) which is provided to the bypass passage (B).

Description

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

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

[0003] As shown in JP2020-143685A, for example, such a shock absorber includes a cylinder, a piston that is movably inserted into the cylinder and divides the interior of the cylinder into an extension-side chamber and a compression-side chamber filled with hydraulic oil, a piston rod that is movably inserted into the cylinder and connected to the piston, a tank that stores hydraulic oil, a hard-side damping element that is provided on the piston and connects the extension-side chamber and the compression-side chamber and provides resistance to the flow of hydraulic oil passing through it, a bypass path that bypasses the hard-side damping element and connects the extension-side chamber and the compression-side chamber, and a solenoid valve and a soft-side damping element that are provided in series with the bypass path.

[0004] In a shock absorber configured in this manner, the opening area of ​​the bypass passage is adjusted using a solenoid valve, thereby adjusting 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 range of damping force adjustment and outputting a damping force that is optimal for suppressing vehicle vibrations.

[0005] JP2020-143685A

[0006] Conventional shock absorbers have a structure in which an outer shell is provided around the outer periphery of a cylinder, a bypass path 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 path.

[0007] As described above, conventional shock absorbers require a large-diameter outer shell that covers the cylinder to form a bypass path, which increases the shock absorber size, weight, and manufacturing costs. Larger shock absorbers can be difficult to install in some vehicles due to limited mounting space, and increased weight leads to increased fuel consumption, so there is a demand for lighter shock absorbers.

[0008] SUMMARY OF THE INVENTION An object of the present invention is to provide a shock absorber that is small and lightweight, can reduce manufacturing costs, and can be easily mounted on a vehicle.

[0009] In order to solve the above problems, the shock absorber of the present invention includes a cylinder, a cylindrical piston rod that is inserted into the cylinder so as to be axially movably, a piston that is connected to the piston rod, inserted into the cylinder so as to be axially movably, and divides the inside of the cylinder into an extension-side chamber and a compression-side chamber, a cap that closes the end of the cylinder on the side of the compression-side chamber, a cylindrical inner rod that extends from the cap, is inserted into the compression-side chamber, and is slidably fitted into the piston rod, a main damping passage that provides resistance to the flow of liquid moving back and forth between the extension-side chamber and the compression-side chamber, a bypass passage that bypasses the main damping passage and communicates 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 path bypasses the main damping passage and connects the extension-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 path is provided inside the cylinder, a large-diameter outer shell covering the cylinder is not required to form the bypass path.

[0011] Fig. 1 is a cross-sectional view of a shock absorber according to an embodiment, and Fig. 2 is a diagram showing the damping force characteristics of the shock absorber according to an embodiment.

[0012] 1 , a shock absorber D in one embodiment includes a cylinder 1, a cylindrical piston rod 2 axially movably inserted into the cylinder 1, a piston 3 connected to the piston rod 2 and axially movably inserted into the cylinder 1, the piston 3 dividing the interior of 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 fluid between the expansion-side chamber R1 and the compression-side chamber R2, a bypass passage B bypassing the main damping passage M and communicating the expansion-side chamber R1 with 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.

[0013] Although not shown, this shock absorber D is installed between the body and rear wheel of a saddle-ride type vehicle such as a motorcycle to suppress vibrations of the body and rear wheel. Note that the shock absorber D may also be used to suppress vibrations of vehicles other than saddle-ride type vehicles.

[0014] Below, each part of the shock absorber D will be described in detail. As shown in Fig. 1, the cylinder 1 is cylindrical, and its upper end in Fig. 1 is closed by a rod guide 17, and its lower end in Fig. 1 is closed by a cap 10. A threaded portion 1a is provided at a position slightly above the lower end of the cylinder 1 in Fig. 1, and the cap 10 is threadedly coupled to the threaded portion 1a and attached to the lower end of the cylinder 1 in Fig. 1.

[0015] 1 is annular, and includes an annular seal ring 17a on its outer periphery that tightly contacts the inner periphery of the cylinder 1, and an annular seal ring 17b and an annular bush 17c on its inner periphery that slide against the outer periphery of the piston rod 2. The rod guide 17 is restricted from moving upward in FIG. 1 relative to the cylinder 1 by a C-ring 24 that is attached to the inner periphery of the upper end of the cylinder 1 in FIG.

[0016] The piston rod 2, which is movably inserted into the cylinder 1, is inserted through the seal ring 17b and bushing 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 bushing 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 also tightly fits against the inner periphery of the cylinder 1 to 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 of the cylinder 1 in FIG. 1, via the inner periphery of the rod guide 17.

[0017] The piston rod 2 is cylindrical and includes a small-diameter portion 2a at its lower end in Fig. 1, the outer diameter of which is smaller than that of its upper portion, and on whose outer periphery the piston 3 is attached, 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 radially penetrates 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-ride type vehicle is attached to the upper end of the piston rod 2 in Fig. 1.

[0018] A piston 3 attached to a piston rod 2 is inserted into the cylinder 1 so as to be axially movable, and the piston 3 divides the interior of the cylinder 1 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 a liquid other than hydraulic oil, such as water or an aqueous solution. The through-hole 2c of the piston rod 2 opens above the small-diameter portion 2a on which the piston 3 is attached in FIG. 1 and faces the extension-side chamber R1, so that the interior of the piston rod 2 is in communication with the extension-side chamber R1 via the through-hole 2c.

[0019] The piston 3 is annular and attached to the outer periphery of the small diameter portion 2a of the piston rod 2, and is provided with an expansion-side port 3a and a compression-side port 3b that respectively communicate in parallel with the expansion-side chamber R1 and the compression-side chamber R2. An expansion-side main damping valve 13 is annular and attached to the outer periphery of the small diameter portion 2a and opens and closes the expansion-side port 3a, and is stacked at the lower end of the piston 3 in FIG. 1. Also, an expansion-side main damping valve 14 is annular and attached to the outer periphery of the small diameter portion 2a and opens and closes the compression-side port 3b, and 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 onto 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 threaded onto the lower end of the small diameter portion 2a.

[0020] 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 on the lower end of the piston 3 in FIG. 1 , has an inner circumferential side fixed, and opens the expansion-side port 3a when the outer circumferential side is deflected by the pressure in the expansion-side chamber R1. The expansion-side main damping valve 13 is capable of opening and closing the expansion-side port 3a, opens when the shock absorber D expands, and provides resistance to the flow of fluid passing through the expansion-side port 3a from the expansion-side chamber R1 to the compression-side chamber R2, and closes when the shock absorber D contracts, and blocks 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 provides resistance to the flow of fluid from the expansion-side chamber R1 to the compression-side chamber R2 and can exert a damping force that prevents the expansion of the shock absorber D when the shock absorber D expands.

[0021] In contrast, in the shock absorber D of this embodiment, the compression side main damping valve 14 is a laminated leaf valve configured by stacking multiple annular plates on the upper end of the piston 3 in FIG. 1 , with the inner circumferential side fixed and opening the compression side port 3b when the outer circumferential side is deflected by the pressure in the compression side chamber R2. The compression side main damping valve 14 is capable of opening and closing the compression side port 3b, and opens when the shock absorber D contracts to provide resistance to the flow of fluid passing through the compression side port 3b from the compression side chamber R2 to the expansion side chamber R1, and closes to block the compression side port 3b when the shock absorber D expands. 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 fluid 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 it contracts. Also, 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 the annular plate that constitutes the extension side main damping valve 13 and the compression side main damping valve 14, or by a stamping provided in the valve seat of the piston 3 on which the annular plate is seated and released.

[0022] In this way, 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. Furthermore, 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 fluid passing through the expansion-side port 3a and the compression-side port 3b and moving back and forth 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 fluid passing through the expansion-side port 3a, and the compression-side main damping valve 14 provides resistance to the flow of fluid 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 configure a main damping passage M that provides resistance to the flow of fluid 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 fluid reciprocating between the expansion-side chamber R1 and the compression-side chamber R2.

[0023] 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 threaded portion 10a1 on the inner circumference of the cylindrical portion 10a to a threaded portion 1a on the outer circumference of the cylinder 1.

[0024] 1, the cylindrical portion 10a has a threaded portion 10a1 provided on the inner periphery at the upper end, and an annular sealing groove 10a2 provided on the inner periphery below the threaded portion 10a1. A seal ring 20 that fits tightly against the outer periphery of the cylinder 1 is housed in the sealing groove 10a2 provided on the inner periphery of the cylindrical portion 10a, thereby sealing the gap between the cap 10 and the cylinder 1.

[0025] Next, the bottom 10b of the cap 10 has a recess 10b1 in the center of its upper end in Fig. 1, and the lower end of the cylindrical inner rod 4 in Fig. 1 is inserted into this 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 fits tightly against the outer periphery of the inner rod 4 is provided in the recess 10b1, sealing the gap between the cap 10 and the inner rod 4.

[0026] As described above, the inner rod 4 extends from the bottom portion 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 bushing 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 displaces relative to the cylinder 1, the piston rod 2 also displaces relative to the inner rod 4 held in the cap 10. Furthermore, the inner rod 4 is loosely fitted in the recess 10b1 and held in the cap 10 by the retaining ring 5, but a slight radial deflection at its upper end in FIG. 1 is allowed. When inserted into the piston rod 2, the inner rod 4 can smoothly advance and retreat within the piston rod 2, following the piston rod 2. The interior of the inner rod 4 is in communication with the interior of the piston rod 2 and the extension-side chamber R1 via the through-hole 2c, and together with the interior of the piston rod 2, forms an intra-rod passage Pr.

[0027] 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.

[0028] 1, a bracket 10c is provided at the lower end of the bottom 10b of the cap 10, and the lower end of the shock absorber D can be connected via the bracket 10c to a swing arm that holds the rear wheel of a saddle-riding type vehicle. Note that, although the present embodiment has been described in terms of connecting the piston rod 2 to the body of the saddle-riding type vehicle and connecting the cap 10 to the rear wheel of the saddle-riding type vehicle, the piston rod 2 may alternatively 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.

[0029] Furthermore, the cap 10 includes a tank holder 10d that holds a tank 18 that extends radially from the side of the bottom 10b and is disposed parallel to the cylindrical portion 10a. The tank 18 is cylindrical, with its lower end integrally connected to the tank holder 10d, and houses a bladder 19 therein. The tank 18 is divided 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 the air chamber G is at least equal to or greater than atmospheric pressure when the shock absorber D is fully extended. Note that the liquid chamber L and the air chamber G in the tank 18 can be separated by a free piston in addition to using an elastic partition such as the bladder 19 or a diaphragm.

[0030] In addition, in this embodiment, as shown in Figure 1, the cap 10 is provided with an internal cap passage Pc that opens from the lower end of the recess 10b1 in Figure 1 and leads to the end 10b2 of the bottom 10b that faces the pressure side chamber R2, and an exhaust passage EP and an suction passage SP that open from the end 10b2 of the bottom 10b and lead to the liquid chamber L of the tank 18.

[0031] One end of the cap internal passage Pc is connected to the expansion-side chamber R1 through the rod internal passage Pr, and the other end is connected to the compression-side chamber R2, and together with the rod internal passage Pr, 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.

[0032] 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 that constitutes part of the bypass path B, a compression side damping valve 30 arranged in the middle of the discharge passage EP, and an intake check valve 31 as an intake side valve arranged in the middle of the intake passage SP.

[0033] The damping force adjustment valve 21 is installed in series with the extension side low speed valve 22 and the compression side low speed valve 23 with respect to the bypass path B, and the extension side low speed valve 22 and the compression side low speed valve 23 are installed in parallel with each other with respect to the bypass path B.

[0034] In this embodiment, the damping force control valve 21 includes a valve element 21a that can open and close the cap passage Pc that forms part of the bypass path B, a spring 21b that biases the valve element 21a to close it, and a solenoid 21c that is attached to the side of the bottom portion 10b and is capable of generating a thrust that pushes the valve element 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 also be an electromagnetic valve whose valve opening pressure can be adjusted, or a damping force control valve in which the valve opening degree or valve opening pressure is adjusted manually.

[0035] 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 low-speed extension-side valve 22 has a lower valve opening pressure than the main extension-side damping valve 13, and opens prior to the main extension-side damping valve 13 to generate a damping force when the extension speed of the shock absorber D is low.

[0036] 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 before the compression side main damping valve 14 to generate a damping force.

[0037] In this embodiment, the cap intra-passage Pc is provided with the extension-side low speed 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 compression-side low speed 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. These extension-side low speed valve 22 and the compression-side low speed valve 23 are defined as low speed valves, but any valve that allows the flow of liquid reciprocating between the expansion-side chamber R1 and the compression-side chamber R2 and provides resistance to the flow of liquid passing through may also be defined as the low speed valve.

[0038] The compression side damping valve 30 is provided in the discharge passage EP and serves as a damping valve that opens to resist the flow of liquid from the compression side chamber R2 toward the tank 18 and closes to block the discharge passage EP against the flow of liquid from the tank 18 toward the compression side chamber R2. The suction check valve 31 serving as a suction side valve is provided in the suction passage SP and serves as a damping valve that opens to resist the flow of liquid from the tank 18 toward the compression side chamber R2 and allows the liquid to pass with almost no resistance to the flow of liquid, but closes to block the suction passage SP against the flow of liquid from the compression side chamber R2 toward the tank 18. As described above, the suction side valve in this embodiment is the suction check valve 31 that is provided in the suction passage SP and allows only the flow of liquid from the tank 18 toward the compression side chamber R2, but it may also be a damping valve that is provided in the suction passage SP and provides resistance to the flow of liquid from the tank 18 toward the compression side chamber R2.

[0039] The shock absorber D of this embodiment is configured as described above, and operation of the shock absorber D will be described below. When the shock absorber D extends, the piston rod 2 retracts from the cylinder 1, and the piston 3 compresses the extension-side chamber R1. Then, the liquid in the extension-side chamber R1 passes through an orifice (not shown) in the main damping passage M, the extension-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 extension-side low-speed valve 22. Since the amount of liquid in the cylinder 1 is insufficient 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, the suction check valve 31 opens and the shortage of liquid is supplied from the tank 18 into the cylinder 1 via the suction passage SP. As described above, 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, so when the shock absorber D extends, 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.

[0040] Resistance is applied to the flow of fluid 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 expansion-side operation due to this resistance. Regarding the resistance applied when fluid 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 an orifice (not shown) applies resistance to the flow of fluid, whereas when the expansion speed of the shock absorber D is in the high-speed range, the expansion-side main damping valve 13 opens and the expansion-side main damping valve 13 applies resistance to the flow of fluid. Then, changing the amount of current supplied to the damping force control valve 21 changes the distribution ratio of fluid passing through the main damping passage M and the low-speed expansion-side valve 22 during the expansion operation of the shock absorber D.

[0041] 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 path 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. Furthermore, 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 path 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, as shown in Fig. 2, the damping force characteristics generated by the shock absorber D when the extension speed is in the low-speed range during extension operation can be changed within a range from soft characteristics generated mainly by the low-speed extension valve 22, indicated by the dashed line in Fig. 2, to hard characteristics generated mainly by the main damping passage M, indicated by the solid line in Fig. 2, by adjusting the amount of current supplied to the damping force control valve 21. Furthermore, when the extension speed reaches the high-speed range during extension operation, the extension-side main damping valve 13 opens widely regardless of the opening degree of the damping force control valve 21, and the fluid passes preferentially through the main damping passage M, so that the shock absorber D generates damping force by the extension-side main damping valve 13. Note that if the suction-side valve is a damping valve instead of the suction check valve 31, resistance is applied to the flow of fluid as it moves from the tank 18 into the cylinder 1 via the suction passage SP, thereby reducing the pressure in the compression-side chamber R2 and enabling the generation of a higher damping force.

[0042] Conversely, when the shock absorber D is contracting, 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 path B partially formed by the piston rod 2 and the inner rod 4, and moves through the compression-side low-speed valve 23 to the extension-side chamber R1. Furthermore, an 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 excess liquid in the cylinder 1, so the excess liquid passes through the compression-side damping valve 30 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 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. Therefore, when the shock absorber D is contracting, excess liquid always becomes excess liquid in the cylinder 1 and moves from the cylinder 1 to the tank 18.

[0043] Resistance is applied to the flow of fluid 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 fluid 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 the above-mentioned resistances. With regard to the resistance applied when fluid 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 fluid 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 fluid by the compression side main damping valve 14. Then, by changing the amount of current supplied to the damping force control valve 21, the distribution ratio of fluid 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.

[0044] 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 path B is blocked and the liquid cannot pass through the compression side low speed valve 23, but passes only through the main damping passage M and moves from the compression side chamber R2 to the expansion side chamber R1. Furthermore, 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 path 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 compression speed is in the low-speed range during compression, the damping force characteristics generated by the shock absorber D can be 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. Furthermore, when the compression speed reaches the high-speed range during compression, 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 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, so 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 therefore the shock absorber D can generate a higher compression side damping force than conventional shock absorbers.

[0045] In the shock absorber D of this embodiment, the extension side low-speed valve 22 and the compression side low-speed valve 23 are provided as low-speed valves, but it is also possible to eliminate the extension side low-speed valve 22 and the compression side low-speed valve 23 and adjust the damping force by changing the opening degree of the damping force control valve 21.

[0046] 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 movably, the piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be axially movably, and dividing the interior of the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2, the cap 10 closing the end of the cylinder 1 on the compression-side chamber side, the cylindrical inner rod 4 extending from the cap 10, inserted into the compression-side chamber R2, and slidably fitted into the piston rod 2, the main damping passage M providing resistance to the flow of liquid moving back and forth between the extension-side chamber R1 and the compression-side chamber R2, the bypass passage B bypassing the main damping passage M and communicating the extension-side chamber R1 with 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.

[0047] In the shock absorber D configured in this manner, the bypass path B bypasses the main damping path M and connects the expansion-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 inserted into the piston rod 2, and the bypass path B is provided inside the cylinder 1, so that 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 the present embodiment, since an outer shell is not required, the shock absorber D can be made small and lightweight, reducing manufacturing costs, and can be installed in vehicles with limited installation space, thereby improving vehicle mountability.

[0048] Furthermore, in the shock absorber D of this embodiment, 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. According to the shock absorber D configured in this manner, during extension, liquid moves from the expansion-side chamber R1 to the compression-side chamber R2, and during contraction, liquid moves from the compression-side chamber R2 to the expansion-side chamber R1, so the flow of liquid is similar to that of conventional shock absorbers, and it is easy to set the damping force characteristics.

[0049] 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.

[0050] With the shock absorber D configured in this manner, not only can the damping force be adjusted to a high or low level while ensuring a damping force adjustment range by adjusting the flow rate distribution ratio between the main damping passage M and the bypass passage B with the damping force adjustment valve 21, but also, since the discharge 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 conventional shock absorbers. As described above, with the shock absorber D of this embodiment, a high damping force can be generated during contraction while ensuring a damping force adjustment range.

[0051] Furthermore, 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 fluid moving between the extension-side chamber R1 and the compression-side chamber R2. With the shock absorber D configured in this manner, the damping force control valve 21 is opened to activate 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 to generate a damping force that is suitable for when the saddle-ride type vehicle is traveling on good roads with few bumps and no vibrations at high speeds.

[0052] Although the preferred embodiment of the present invention has been described in detail, modifications, variations and changes can be made thereto without departing from the scope of the appended claims.

[0053] 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... discharge passage, M... main damping passage, R1... extension side chamber, R2... compression side chamber, SP... discharge passage

Claims

1. A shock absorber comprising: a cylinder; a cylindrical piston rod inserted into the cylinder so as to be axially movably; a piston connected to the piston rod, 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 an end of the cylinder at a side of the compression-side chamber; 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 a flow of liquid traveling 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 inside the piston rod and inside the inner rod; and a damping force adjustment valve provided in the bypass passage.

2. A shock absorber as claimed in claim 1, wherein the cross-sectional area of ​​the annular gap between the inner circumference of the cylinder and the outer circumference of the piston rod is larger than the cross-sectional area of ​​the inner rod.

3. A shock absorber as claimed in claim 1 or 2, comprising: 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 towards the tank; and a suction side valve provided in the suction passage for allowing the flow of liquid from the tank towards the compression side chamber.

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