Shock absorber

Abstract

A shock absorber (D) according to the present invention comprises: a cylinder (1); a hollow piston rod (2) that is inserted into the cylinder (1) so as to be movable in the axial direction; a piston (3) that is connected to the piston rod (2), is inserted into the cylinder (1) so as to be movable in the axial direction, and partitions the inside of the cylinder (1) into an extension chamber (R1) and a compression chamber (R2); a main damping passage (M) that imparts resistance to the flow of liquid going back and forth between the extension chamber (R1) and the compression chamber (R2); an extension passage (P1) provided in the piston rod (2) and communicating with the extension chamber (R1); a compression passage (P2) provided in the piston rod (2) and communicating with the compression chamber (R2); a bracket (6) connected to the tip of the piston rod (2) on the side opposite to the cylinder and having a communication passage (P3) connecting the extension passage (P1) and the compression passage (P2); and a damping force adjustment valve (20) provided to the bracket (6) and disposed partway through the communication passage (P3).

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 disclosed 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 hollow 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 main damping passage that provides resistance to the flow of liquid moving between the extension-side chamber and the compression-side chamber, an extension-side passage provided in the piston rod and connected to the extension-side chamber, a compression-side passage provided in the piston rod and connected to the compression-side chamber, a bracket connected to the tip of the piston rod on the side opposite to the cylinder and having a connecting passage that connects the extension-side passage and the compression-side passage, and a damping force adjustment valve provided on the bracket and arranged midway through the connecting passage.

[0010] The shock absorber configured in this manner has an extension-side passage and a compression-side passage that bypass the main damping passage over the entire length of the piston rod and connect the extension-side chamber and the compression-side chamber, and a damping force adjustment valve is provided in the connecting passage provided in the bracket, so that a large-diameter outer shell covering the cylinder is not required to form the extension-side passage and the compression-side passage that bypass the main damping passage.

[0011] Fig. 1 is a cross-sectional view of a shock absorber according to one embodiment. Fig. 2 is an enlarged cross-sectional view of a bracket portion of the shock absorber according to one embodiment. Fig. 3 is a diagram showing damping force characteristics of the shock absorber according to one embodiment. Fig. 4 is a cross-sectional view of a shock absorber according to a modified example of one embodiment. Fig. 5 is a cross-sectional view of a shock absorber according to another embodiment. Fig. 6 is a cross-sectional view of a shock absorber according to a modified example of another embodiment.

[0012] 1, a shock absorber D in one embodiment includes a cylinder 1, a hollow piston rod 2 movably inserted into the cylinder 1 in the axial direction, a piston 3 connected to the piston rod 2 and movably inserted into the cylinder 1 in the axial direction, the piston 3 dividing the interior of the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2, a main damping passage M providing resistance to the flow of fluid between the extension-side chamber R1 and the compression-side chamber R2, an extension-side passage P1 provided in the piston rod 2 and communicating with the extension-side chamber R1, a compression-side passage P2 provided in the piston rod 2 and communicating with the compression-side chamber R2, a bracket 6 connected to the tip of the piston rod 2 on the side opposite to the cylinder and having a connecting passage P3 connecting the extension-side passage P1 and the compression-side passage P2, and a damping force control valve 20 provided on the bracket 6 and arranged midway along the connecting passage P3.

[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] Hereinafter, a detailed description will be given of each part of the shock absorber D. 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.

[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 bush 17b and an annular seal ring 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 30 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 bushing 17b and seal ring 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 17b 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 17c. A seal ring 17a tightly fits against the inner periphery of the cylinder 1 to prevent liquid leakage from between the rod guide 17 and the cylinder 1. A free piston 19 is housed within the cylinder 1, at the lower side in Figure 1, and slides against the inner periphery of the cylinder 1 to divide the interior of the cylinder 1 into a liquid chamber L and an air chamber G.

[0017] Furthermore, an annular bump stopper 18 is attached by press fitting or the like to the inner periphery of the open end at the upper end of the cylinder 1 in Fig. 1, and is positioned above the rod guide 17. The upper end of the piston rod 2 in Fig. 1 passes through the inside of the rod guide 17 and the bump stopper 18 and protrudes outward from the upper end of the cylinder 1 in Fig. 1.

[0018] The piston rod 2 is hollow and includes a cylindrical interior pipe 25 and a cylindrical exterior pipe 26 that houses the interior pipe 25 therein. 1, a small-diameter portion 26a provided at the lower end in FIG. 1, having an outer diameter smaller than that of an upper portion, on whose outer circumference the piston 3 is attached; a base-end thread portion 26b provided on the outer circumference of the base end of the small-diameter portion 26a, which is the lower end in FIG. 1 of the small-diameter portion 26a; a through-hole 26c radially penetrating a side portion above the small-diameter portion 26a in FIG. 1; a tip-end thread portion 26d provided on the outer circumference of the tip end, which is the upper end in FIG. 1; a small-inner-diameter portion 26e on the inner periphery, which is formed so that the inner diameter below the through-hole 26c in FIG. 1 is smaller than that above; a medium-inner-diameter portion 26f on the inner periphery, which is provided between the through-hole 26c and the small-inner-diameter portion 26e and has an inner diameter larger than that of the small-inner-diameter portion 26e; and a large-inner-diameter portion 26g on the inner periphery, which is above the medium-inner-diameter portion 26f in FIG. 1 and has an inner diameter larger than that of the medium-inner-diameter portion 26f.

[0019] The interior pipe 25 is cylindrical and has an outer diameter large enough to fit into the medium inner diameter portion 26f, and is fitted into the medium inner diameter portion 26f of the exterior pipe 26, with its lower end in Fig. 1 abutting tightly against the step at the boundary between the small inner diameter portion 26e and the medium inner diameter portion 26f, and is housed within the exterior pipe 26. The overall length of the interior pipe 25 is longer than the axial length from the lower end of the medium inner diameter portion 26f of the exterior pipe 26 to the tip, which is the upper end, of the exterior pipe 26, and when the interior pipe 25 is housed in the exterior pipe 26 as described above, its upper end, which is the tip, protrudes upward from the tip of the exterior pipe 26.

[0020] Furthermore, when the interior pipe 25 is fitted onto the inner periphery of the medium inner diameter portion 26f and accommodated within the exterior pipe 26, an annular gap is formed between the inner periphery of the large inner diameter portion 26g of the exterior pipe 26 and the outer periphery of the interior pipe 25. This annular gap between the exterior pipe 26 and the interior pipe 25 is communicated with the expansion-side chamber R1 by the through hole 26c. Furthermore, the interior of the interior pipe 25 is communicated with the compression-side chamber R2 via the interior of the small inner diameter portion 26e of the exterior pipe 26.

[0021] 1, the piston 3 is mounted on the small-diameter portion 26a at the lower end of the piston rod 2, which serves as the base end of the piston rod 2. The piston 3 is axially movably accommodated within the cylinder 1 and divides the fluid chamber L within the cylinder 1 into an extension-side chamber R1 on the upper side in FIG. 1 and a compression-side chamber R2 on the lower side in FIG. 1. The extension-side chamber R1 and the compression-side chamber R2, which are divided within the cylinder 1 by the piston 3, are filled with a liquid such as hydraulic oil. Note that although the liquid is hydraulic oil in this embodiment, it may be a liquid other than hydraulic oil, such as water or an aqueous solution. The through-hole 26c of the piston rod 2 opens above the small-diameter portion 26a on which the piston 3 is mounted 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 26c.

[0022] The piston 3 is annular and attached to the outer periphery of the small diameter portion 26a of the outer pipe 26 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 26a 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 26a 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 26a of the piston rod 2, and are fixed to the piston rod 2 by a piston nut 15 that is threadedly attached to the lower end of the small diameter portion 26a.

[0023] 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.

[0024] 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.

[0025] 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 throttle passage 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.

[0026] 1, which is the tip of the piston rod 2 on the side opposite the cylinder, is attached with a bracket 6 that can connect the shock absorber D to the body of a saddle-ride type vehicle (not shown). The bracket 6 is equipped with a connecting portion 6a that can be connected to the vehicle body (not shown), a valve holding portion 6b that is connected to the lower part of the connecting portion 6a in FIG. 1 and to which the damping force control valve 20 is attached, and a rod mounting portion 6c that is connected to the lower part of the valve holding portion 6b in FIG. 1 and to which the tip of the piston rod 2 is attached.

[0027] The connecting portion 6a is annular and has an inner circumference through which an axle attached to the vehicle body (not shown) is inserted to hold the outer periphery of the axle, and is provided with a mounting eye that can swing around the axle relative to the vehicle body.

[0028] The valve holding portion 6b is tubular and extends in the left-right direction in Fig. 1, and accommodates a valve portion of the damping force control valve 20 inside. As shown in Fig. 2, the rod mounting portion 6c is provided with: a piston rod insertion hole 6c1 that opens from the lower end and extends upward, into which the tip of the piston rod 2 is inserted and screwed; a vertical hole 6c2 that connects the upper end of the piston rod insertion hole 6c1 to the inside of the valve holding portion 6b; and an oblique hole 6c3 that connects the piston rod insertion hole 6c1 to the valve holding portion 6b.

[0029] The piston rod insertion hole 6c1 has an inner diameter larger on the lower side in Fig. 1 than on the upper side, and the larger inner diameter portion is provided with a threaded portion 6c11 into which the tip threaded portion 26d of the exterior pipe 26 of the piston rod 2 is screwed. The tip of the interior pipe 25 is fitted into the upper side of the threaded portion 6c11 of the piston rod insertion hole 6c1 in Fig. 1. Therefore, when the tip threaded portion 26d of the exterior pipe 26 is screwed into the threaded portion 6c11 of the piston rod insertion hole 6c1 while the piston rod 2 is inserted into the piston rod insertion hole 6c1, the upper end of the interior pipe 25, which protrudes above the tip of the exterior pipe 26, is fitted into the upper side of the threaded portion 6c11 of the piston rod insertion hole 6c1 in Fig. 1.

[0030] When the rod mounting portion 6c of the bracket 6 is mounted on the outer periphery of the tip of the piston rod 2 in this manner, the upper end of the inner pipe 25 in FIG. 1 fits into the piston rod insertion hole 6c1, and the inner pipe 25 is clamped between the rod mounting portion 6c and the outer pipe 26 and fixed to the outer pipe 26 and the bracket 6.

[0031] 1, the inside of the interior pipe 25 is communicated with the inside of the valve holding portion 6b via the vertical hole 6c2 without passing through the annular gap between the interior pipe 25 and the exterior pipe 26. Furthermore, by attaching the piston rod 2 to the rod attachment portion 6c, the annular gap between the interior pipe 25 and the exterior pipe 26 is communicated with the inside of the valve holding portion 6b via the oblique hole 6c3 without passing through the interior of the interior pipe 25.

[0032] Therefore, the inside of the valve holding portion 6b is communicated with the compression-side chamber R2 via the inside of the small inner diameter portion 26e of the exterior pipe 26, the interior of the interior pipe 25, and the vertical hole 6c2, and a compression-side passage P2 is formed by the interior pipe 25. Furthermore, the inside of the valve holding portion 6b is communicated with the expansion-side chamber R1 via the through-hole 26c, the annular gap between the interior pipe 25 and the exterior pipe 26, and the oblique hole 6c3, and an expansion-side passage P1 is formed by the annular gap between the interior pipe 25 and the exterior pipe 26. Furthermore, as shown in FIG. 2 , the vertical hole 6c2, the interior of the valve holding portion 6b, and the oblique hole 6c3 form a connecting passage P3 that connects the expansion-side passage P1 and the compression-side passage P2.

[0033] The damping force control valve 20 includes a cylindrical valve housing 21 that is accommodated in the valve holding portion 6 b of the bracket 6 and attached to the valve holding portion 6 b, a spool 22 that serves as a valve body that is accommodated in the valve housing 21 so as to be movable in the axial direction, a solenoid 23 that is attached to the right end of the valve housing 21 in Figure 2 and serves as an actuator that drives the spool 22, and a spring 24 that biases the spool 22.

[0034] The valve housing 21 is cylindrical, inserted into the valve holding portion 6 b, and attached to the valve holding portion 6 b by being screwed in. As shown in Fig. 2 , the valve housing 21 includes a compression-side port 21 a that radially penetrates the wall near the center to communicate between the inside and outside of the valve housing 21, an expansion-side port 21 b that radially penetrates the wall to the right of the position where the compression-side port 21 a is provided to communicate between the inside and outside of the valve housing 21, and a step 21 c provided on the inner periphery on the left end side, which is closer to the tip end in Fig. 2 than the compression-side port 21 a.

[0035] When the valve housing 21 is accommodated in the valve holding portion 6b, the compression-side port 21a faces the vertical hole 6c2, and the expansion-side port 21b faces the oblique hole 6c3. Therefore, the inside of the valve housing 21 is connected to the compression-side passage P2 via the compression-side port 21a and the vertical hole 6c2, and to the expansion-side passage P1 via the expansion-side port 21b and the oblique hole 6c3. In this manner, the valve housing 21 is connected to the connection passage P3 from the inside and is disposed midway along the connection passage P3. Note that the vertical hole 6c2 and the oblique hole 6c3 are not connected through the gap between the valve housing 21 and the valve holding portion 6b, and the gap between the valve housing 21 and the valve holding portion 6b is sealed to prevent fluid from leaking from the valve holding portion 6b.

[0036] A plug 40 is detachably attached to the inner periphery of the tip of the valve housing 21, and the tip side of the valve housing 21 is sealed by the plug 40. The inside of the valve housing 21 is connected to the expansion-side chamber R1 via the expansion-side passage P1 and to the compression-side chamber R2 via the compression-side passage P2, so that with the plug 40 removed from the valve housing 21, hydraulic oil can be injected into the cylinder 1 from the tip of the valve housing 21. In this way, oil can be injected into the shock absorber D using the valve housing 21, bracket 6, and piston rod 2 of the damping force control valve 20, making the oil injection operation easy.

[0037] The spool 22 is inserted toward the solenoid 23, which is to the right of the stepped portion 21c of the valve housing 21 in Figure 2, and can move left and right in Figure 2, which is the axial direction, relative to the valve housing 21. The spool 22 is cylindrical and has a control port 22a that penetrates the valve housing 21 in the radial direction and can face the extension-side port 21b. Therefore, the spool 22, together with the valve housing 21, is provided midway through the connecting passage P3.

[0038] The spool 22 can open and close the expansion-side port 21b by moving relative to the valve housing 21. Specifically, when the spool 22 is positioned so that its outer periphery faces the expansion-side port 21b, it closes the expansion-side port 21b, blocks the connecting passage P3, and cuts off communication between the expansion-side passage P1 and the compression-side passage P2. On the other hand, when the spool 22 is positioned so that its control port 22a faces the expansion-side port 21b, it opens the expansion-side port 21b, brings the connecting passage P3 into a communicating state, connects the expansion-side passage P1 and the compression-side passage P2, and can adjust the resistance to the flow of hydraulic oil passing through the connecting passage P3 depending on the degree of communication between the control port 22a and the expansion-side port 21b.

[0039] The solenoid 23 is attached to the right end of the valve housing 21 in Figure 2. Although not shown in detail, the solenoid 23 includes a fixed iron core housed in a frame 23a, a coil, a movable iron core that is attracted to the fixed iron core when current is passed through the coil, and a push rod 23b that is attached to the movable iron core and protrudes outward from the frame 23a. The push rod 23b abuts against the right end of the spool 22 in Figure 2 and can transmit the thrust of the solenoid 23 to the spool 22.

[0040] 2 of the spool 22 and the stepped portion 21c of the valve housing 21. The spring 24 biases the spool 22 to position the spool 22 at a position where the control port 22a and the extension-side port 21b are most closely opposed to each other when the solenoid 23 is not energized.

[0041] On the other hand, when the solenoid 23 is energized and the push rod 23b moves in a direction protruding from the frame 23a to the left in FIG. 2, moving the spool 22 against the biasing force of the spring 24, the damping force control valve 20 reduces the degree of communication between the control port 22a of the spool 22 and the extension-side port 21b. Then, the thrust of the solenoid 23 is increased to compress the spring 24, and when the control port 22a of the spool 22 and the extension-side port 21b can no longer face each other, the outer periphery of the spool 22 closes the extension-side port 21b, and the damping force control valve 20 closes and blocks the connection passage P3. In this way, the damping force control valve 20 can open and close the connection passage P3 depending on the amount of current supplied to the solenoid 23, and can adjust the degree of communication between the control port 22a and the extension-side port 21b to adjust the resistance to the flow of hydraulic oil through the connection passage P3.

[0042] In addition, while the pressure of the compression side chamber R2 acts on the left end of the spool 22 in Figure 2 via the compression side passage P2, a hole 22b that penetrates radially is provided on the right side of the spool 22 in Figure 2, and the pressure of the compression side chamber R2 also acts on the right end of the spool 22 in Figure 2 through the spool 22 and the hole 22b, so the spool 22 does not move axially within the valve housing 21 due to the pressure of the compression side chamber R2.

[0043] In this embodiment, the damping force control valve 20 can reduce the flow area of ​​the connecting passage P3 when the solenoid 23 is energized, and the damping force control valve 20 opens the connecting passage P3 to its maximum when the solenoid 23 is not energized. However, the damping force control valve 20 may increase the flow area of ​​the connecting passage P3 when the solenoid 23 is energized, and may close the connecting passage P3 when the solenoid 23 is not energized. Furthermore, when minimizing the flow area of ​​the connecting passage P3, the damping force control valve 20 may not completely close the connecting passage P3, but may keep the connecting passage P3 in communication. Furthermore, it goes without saying that the solenoid 23 may have a configuration other than that described above as long as it can drive the spool 22.

[0044] 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 expansion-side chamber R1. The fluid in the expansion-side chamber R1 then passes through an orifice (not shown) in the main damping passage M and the expansion-side main damping valve 13 in the main damping passage M. When the damping force control valve 20 is open, the fluid moves to the compression-side chamber R2 via the expansion-side passage P1, the connecting passage P3, the damping force control valve 20, and the compression-side passage P2. When the shock absorber D extends, the piston rod 2 retracts from the cylinder 1, and the displacement of the piston rod 2 retracting from the cylinder 1 decreases. However, the free piston 19 rises within the cylinder 1 in FIG. 1 by the amount of the reduced displacement, expanding the volume of the air chamber G, thereby compensating for the fluctuation in the displacement of the piston rod 2 within the cylinder 1.

[0045] 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 damping force control valve 20, and due to this resistance, the shock absorber D generates a damping force that hinders the extension operation. With regard to the resistance applied when fluid passes through the main damping passage M, when the extension speed of the shock absorber D is in the low-speed range, the extension-side main damping valve 13 does not open and an orifice (not shown) applies resistance to the flow of fluid, and when the extension speed of the shock absorber D is in the high-speed range, the extension-side main damping valve 13 opens and the extension-side main damping valve 13 applies resistance to the flow of fluid. When the amount of current supplied to the damping force control valve 20 is changed to change the degree of opening of the damping force control valve 20, the resistance applied to the flow of fluid when the fluid passes through the damping force control valve 20 changes.

[0046] Specifically, during the extension operation of the shock absorber D, when the damping force control valve 20 is open, the fluid passes through the main damping passage M and the damping force control valve 20, but when the damping force control valve 20 is closed, the connecting passage P3 is blocked and the bypass passage consisting of the expansion-side passage P1, the connecting passage P3, and the compression-side passage P2 that bypasses the main damping passage M is blocked, so the fluid cannot pass through the bypass passage and moves from the expansion-side chamber R1 to the compression-side chamber R2 only through the main damping passage M. Furthermore, when the amount of current supplied to the damping force control valve 20 is reduced, the degree of opening of the damping force control valve 20 increases and the flow rate of fluid passing through the bypass passage increases, so the proportion of fluid passing through the bypass passage increases and the proportion of fluid passing through the main damping passage M decreases. Therefore, as shown in Fig. 3, 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 by adjusting the amount of current supplied to the damping force control valve 20 within a range from soft characteristics indicated by the dashed line in Fig. 3 when the damping force control valve 20 is at its maximum opening to hard characteristics indicated by the solid line in Fig. 3 when the damping force control valve 20 is closed and generated mainly by the main damping passage M. Furthermore, when the extension speed reaches a 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 20, causing the fluid to preferentially pass through the main damping passage M, and the shock absorber D generates damping force by the extension-side main damping valve 13.

[0047] 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 and the compression-side main damping valve 14 in the main damping passage M, and when the damping force control valve 20 is open, moves to the extension-side chamber R1 via the compression-side passage P2, the connecting passage P3, the damping force control valve 20, and the extension-side passage P1. Furthermore, when the shock absorber D is contracting, the piston rod 2 enters the cylinder 1 and the displacement volume of the piston rod 2 entering the cylinder 1 increases, but the free piston 19 descends within the cylinder 1 in FIG. 1 by the amount of the increased displacement volume, reducing the volume of the air chamber G, thereby compensating for the fluctuation in the displacement volume of the piston rod 2 within the cylinder 1.

[0048] 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 damping force control valve 20, and the shock absorber D generates a damping force that hinders the contraction operation due to this resistance. With regard to the resistance applied when the 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 an orifice (not shown) applies resistance to the flow of fluid, 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 applies resistance to the flow of fluid by the compression side main damping valve 14. When the amount of current supplied to the damping force control valve 20 is changed to change the degree of opening of the damping force control valve 20, the resistance applied to the flow of fluid when the fluid passes through the damping force control valve 20 changes.

[0049] Specifically, during the contraction operation of the shock absorber D, when the damping force control valve 20 is open, the liquid passes through the main damping passage M and the damping force control valve 20, but when the damping force control valve 20 is closed, the connecting passage P3 is blocked and the bypass passage consisting of the compression-side passage P2, the connecting passage P3, and the extension-side passage P1 that bypasses the main damping passage M is blocked, so the liquid cannot pass through the bypass passage and moves from the compression-side chamber R2 to the extension-side chamber R1 only through the main damping passage M. Furthermore, when the amount of current supplied to the damping force control valve 20 is reduced, the degree of opening of the damping force control valve 20 increases and the flow rate of liquid passing through the bypass passage increases, so the proportion of liquid passing through the bypass passage increases and the proportion of liquid passing through the main damping passage M decreases. Therefore, as shown in Fig. 3, the damping force characteristics generated by the shock absorber D when the contraction speed is in the low-speed range during contraction can be changed by adjusting the amount of current supplied to the damping force control valve 20 within a range from soft characteristics indicated by the dashed line in Fig. 3 when the damping force control valve 20 is at its maximum opening to hard characteristics generated mainly by the main damping passage M indicated by the solid line in Fig. 3 when the damping force control valve 20 is closed. Furthermore, when the contraction speed reaches a 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 20, and the fluid preferentially passes through the main damping passage M, so that the shock absorber D generates damping force by the compression side main damping valve 14.

[0050] As described above, the shock absorber D of this embodiment includes: the cylinder 1; the hollow piston rod 2 inserted into the cylinder 1 so as to be axially movably; the piston 3 connected to the piston rod 2, 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 main damping passage M that provides resistance to the flow of liquid moving back and forth between the extension-side chamber R1 and the compression-side chamber R2; the extension-side passage P1 provided in the piston rod 2 and connected to the extension-side chamber R1; the compression-side passage P2 provided in the piston rod 2 and connected to the compression-side chamber R2; the bracket 6 connected to the tip of the piston rod 2 on the opposite side to the cylinder and having the connecting passage P3 that connects the extension-side passage P1 and the compression-side passage P2; and the damping force control valve 20 provided on the bracket 6 and arranged midway along the connecting passage P3.

[0051] In the shock absorber D configured as described above, the expansion-side passage P1 and the compression-side passage P2 that bypass the main damping passage M and communicate between the expansion-side chamber R1 and the compression-side chamber R2 are provided over the entire length of the piston rod 2, and the damping force control valve 20 is provided in the connecting passage P3 provided in the bracket 6. Therefore, a large-diameter outer shell that covers the cylinder 1 is not required to form the expansion-side passage P1 and the compression-side passage P2 that bypass the main damping passage M. 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 installability.

[0052] Furthermore, in the shock absorber D of this embodiment, the direction of movement of the spool 22 in the damping force adjustment valve 20 is perpendicular to the direction of expansion and contraction of the shock absorber D, and vibrations are less likely to be input to the spool 22 even when the shock absorber D is expanding and contracting, allowing for stable and precise damping force adjustment.

[0053] In the shock absorber D of this embodiment, the piston rod 2 includes an interior pipe 25 that forms the compression-side passage P2 therein, and an exterior pipe 26 that covers the outer periphery of the interior pipe 25 and forms the extension-side passage P1 between the interior pipe 25 and the exterior pipe 26. According to the shock absorber D configured in this manner, the extension-side passage P1 and the compression-side passage P2 can be easily formed by the interior pipe 25 and the exterior pipe 26 while ensuring sufficient flow path areas for the extension-side passage P1 and the compression-side passage P2. Although not shown, the compression-side passage P2 may be formed by a hole that penetrates the piston rod 2 in the axial direction from the tip to the base end, and the extension-side passage P1 may be formed by a vertical hole that is formed in the axial direction from the tip to partway along the piston rod 2 and a horizontal hole that opens from a side of the piston rod 2 and communicates with the vertical hole. However, by forming the piston rod 2 from the interior pipe 25 and the exterior pipe 26, it is not necessary to process a long hole in the piston rod 2, and therefore costs can be reduced accordingly.

[0054] The damping force control valve 20 also includes a spool (valve element) 22 arranged in the connecting passage P3, and a solenoid (actuator) 23 attached to the bracket 6 for driving the spool (valve element) 22. According to the shock absorber D configured in this manner, the solenoid (actuator) 23 is provided on the bracket 6 attached to the tip of the piston rod 2, so that even if the solenoid (actuator) 23 is installed, the radial size can be reduced compared to conventional shock absorbers in which the solenoid (actuator) 23 is provided on the cylinder 1 side. Note that an actuator other than a solenoid may be used to drive the spool (valve element) 22 of the damping force control valve 20, and the position of the spool (valve element) 22 can also be adjusted manually without installing an actuator.

[0055] Furthermore, the configuration of the damping force adjustment valve 20 is one example, and if a valve capable of adjusting the flow path area is adopted, it may be a variable needle valve or a rotary valve capable of adjusting the flow path area by rotating the valve body.

[0056] In the above description, the bracket 6 is provided at the tip of the piston rod 2, and the valve holder 6b on the bracket 6 that houses the damping force control valve 20 is disposed on the axis of the piston rod 2, between the rod attachment portion 6c that is attached to the piston rod 2 and the connecting portion 6a, but as shown in Fig. 4, the valve holder 6b may be provided between the rod attachment portion 6c and the connecting portion 6a so that its axis is disposed at an eccentric position that is shifted in a direction perpendicular to the axis of the piston rod 2. When the valve holder 6b is provided on the bracket 6 in this way so that its axis is eccentric from the axis of the piston rod 2, the distance between the rod attachment portion 6c that is attached to the tip of the piston rod 2 on the bracket 6 and the connecting portion 6a that is connected to the vehicle body is shortened in the axial direction of the piston rod 2. Therefore, even when the damping force control valve 20 is mounted, the overall length of the shock absorber D can be shortened while ensuring the stroke length of the shock absorber D, and the mountability of the shock absorber D on a saddle-ride type vehicle is improved. In FIG. 4, the damping force adjusting valve 20 housed in the valve holding portion 6b is omitted for ease of understanding.

[0057] Furthermore, as described above, the damping force control valve 20 is a valve that allows the flow of liquid from the expansion-side chamber R1 to the compression-side chamber R2 and the flow of liquid from the compression-side chamber R2 to the expansion-side chamber R1 through the bypass path that bypasses the main damping path M and that is made up of the expansion-side passage P1, the compression-side passage P2, and the connecting passage P3, and that is capable of adjusting the resistance to the liquid flow. However, the damping force control valve 20 may be a valve that allows the flow of liquid only from the expansion-side chamber R1 to the compression-side chamber R2 through the bypass path and is capable of adjusting the resistance to the liquid flow, or may be a valve that allows the flow of liquid only from the compression-side chamber R2 to the expansion-side chamber R1 through the bypass path and is capable of adjusting the resistance to the liquid flow. In this way, when the bypass path is set as a one-way path, the damping force control valve 20 may be a pressure control valve that is capable of adjusting the upstream pressure.

[0058] Therefore, if the damping force adjustment valve 20 is a valve that allows liquid to flow through the bypass path only from the expansion side chamber R1 to the compression side chamber R2 and is capable of adjusting the resistance to the liquid flow, it becomes possible to adjust the damping force during the extension operation of the shock absorber D by adjusting the current supplied to the damping force adjustment valve 20.If the damping force adjustment valve 20 is a valve that allows liquid to flow through the bypass path only from the compression side chamber R2 to the expansion side chamber R1 and is capable of adjusting the resistance to the liquid flow, it becomes possible to adjust the damping force during the contraction operation of the shock absorber D by adjusting the current supplied to the damping force adjustment valve 20.

[0059] Furthermore, shock absorber D provides an air chamber G in cylinder 1 by means of a free piston 19 to compensate for the displacement of piston rod 2 moving in and out of cylinder 1 during extension and contraction, but as in shock absorber D1 of another embodiment shown in Figure 5, the displacement of piston rod 2 moving in and out of cylinder 1 may be compensated for by a tank 50 having an air chamber G1 and a liquid chamber L. In addition, in the description of shock absorber D1, members common to shock absorber D will be assigned common reference numerals and detailed description thereof will be omitted to avoid duplication of explanation.

[0060] Specifically, as shown in FIG. 5, the shock absorber D1 does not include the free piston 19 and the air chamber G in the cylinder 1 of the shock absorber D, and instead includes a tank 50 for storing liquid, a discharge passage 51 that connects the compression side chamber R2 to the tank 50, an intake passage 52 that connects the tank 50 to the compression side chamber R2, a compression side damping valve 53 that is provided in the discharge passage 51 and provides resistance to the flow of liquid from the compression side chamber R2 toward the tank 50, and an intake side valve 54 that is provided in the intake passage 52 and allows the flow of liquid from the tank 50 toward the compression side chamber R2.

[0061] The tank 50 is formed of a cylinder having a top and a bottom and a sealed interior, and houses a free piston 55 inside. The tank 50 is divided into a tank liquid chamber L1, which is filled with liquid by the free piston 55, and an air chamber G1, which is filled with gas. Note that gas is sealed in the air chamber G1 so that the pressure in the air chamber G is at least equal to or higher than atmospheric pressure when the shock absorber D1 is fully extended. Note that the partition between the liquid chamber L and the air chamber G1 inside the tank 50 may be formed by an elastic partition such as a bladder or a diaphragm, other than the free piston 55.

[0062] A discharge passage 51, one end of which is connected to the tank fluid chamber L1, and a suction passage 52, one end of which is also connected to the tank fluid chamber L1, are provided at the bottom of the tank 50. The other end of the discharge passage 51 and the other end of the suction passage 52 are connected to the compression-side chamber R2 in the cylinder 1 via piping 56, such as a flexible hose.

[0063] In this way, the discharge passage 51 and the suction passage 52 are arranged in parallel to connect the compression side chamber R2 and the tank fluid chamber L1 in the tank 50. A compression side damping valve 53 is provided in the discharge passage 51, and a suction side valve 54 is provided in the suction passage 52.

[0064] The compression side damping valve 53 is provided in the discharge passage 51 and serves as a damping valve that opens to resist the flow of liquid from the compression side chamber R2 toward the tank 50 and closes to block the flow of liquid from the tank fluid chamber L1 of the tank 50 toward the compression side chamber R2, thereby blocking the discharge passage 51. The suction side valve 54 is provided in the suction passage 52 and serves as a check valve that opens to permit the flow of liquid from the tank fluid chamber L1 of the tank 50 toward the compression side chamber R2 with almost no resistance to the flow of liquid, but closes to block the suction passage 52 against the flow of liquid from the compression side chamber R2 toward the tank 50. As described above, the suction side valve 54 in the other embodiments is a check valve that is provided in the suction passage 52 and allows only the flow of liquid from the tank 50 toward the compression side chamber R2, but may also be a damping valve that is provided in the suction passage 52 and provides resistance to the flow of liquid from the tank 50 toward the compression side chamber R2.

[0065] The exhaust passage 51, the suction passage 52, the compression side damping valve 53 and the suction side valve 54 are provided at the bottom of the tank 50, but they may also be provided in a valve case installed at the lower end of the cylinder 1.

[0066] The shock absorber D1 of another embodiment is configured as described above. The operation of the shock absorber D1 will be described below. When the shock absorber D1 extends, the piston rod 2 retracts from the cylinder 1, and the piston 3 compresses the expansion-side chamber R1. The fluid in the expansion-side chamber R1 then 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 through the bypass path formed by the expansion-side passage P1, the compression-side passage P2, and the connecting passage P3, and then passes through the damping force control valve 20 and moves to the compression-side chamber R2. Furthermore, because there is a shortage of fluid in the cylinder 1 due to the decrease in the displacement of the piston rod 2 retracting from the cylinder 1, the suction-side valve 54 opens, and the shortage of fluid is supplied from the tank 50 to the cylinder 1 via the suction passage 52. Therefore, when the shock absorber D1 extends, fluid moves from the expansion-side chamber R1 to the compression-side chamber R2 through the main damping passage M or the bypass path.

[0067] 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 damping force control valve 20, and the shock absorber D1 generates a damping force that hinders the extension operation due to this resistance. Regarding the resistance applied to the fluid passing through the main damping passage M, when the extension speed of the shock absorber D1 is in the low-speed range, the extension-side main damping valve 13 does not open and an orifice (not shown) applies resistance to the flow of fluid, whereas when the extension speed of the shock absorber D1 is in the high-speed range, the extension-side main damping valve 13 opens and the extension-side main damping valve 13 applies resistance to the flow of fluid. When the amount of current supplied to the damping force control valve 20 is changed to change the degree of opening of the damping force control valve 20, the resistance applied to the flow of fluid as it passes through the damping force control valve 20 changes.

[0068] Specifically, during the extension operation of the shock absorber D1, when the damping force control valve 20 is open, the fluid passes through the main damping passage M and the damping force control valve 20, but when the damping force control valve 20 is closed, the connecting passage P3 is blocked and the bypass passage that bypasses the main damping passage M is blocked, so the fluid cannot pass through the bypass passage and passes only through the main damping passage M to move from the expansion-side chamber R1 to the compression-side chamber R2. Furthermore, when the amount of current supplied to the damping force control valve 20 is reduced, the degree of opening of the damping force control valve 20 increases and the flow rate of fluid passing through the bypass passage increases, so the proportion of fluid passing through the bypass passage increases and the proportion of fluid passing through the main damping passage M decreases. Therefore, the damping force characteristics generated by the shock absorber D when the extension speed is in the low-speed range during an extension operation can be changed within a range from soft characteristics when the damping force adjustment valve 20 is at its maximum opening degree to hard characteristics generated mainly by the main damping passage M when the damping force adjustment valve 20 is closed, by adjusting the amount of current supplied to the damping force adjustment valve 20. Furthermore, when the extension speed reaches a high-speed range during an extension operation, the extension-side main damping valve 13 opens widely regardless of the opening degree of the damping force adjustment valve 20, and the fluid preferentially passes 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 54 is a damping valve instead of a check valve, resistance is applied to the flow of fluid as it moves from the tank 50 into the cylinder 1 via the suction passage 52, thereby reducing the pressure in the compression-side chamber R2 and enabling a higher damping force to be generated.

[0069] Conversely, when the shock absorber D1 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 moves through an orifice (not shown) in the main damping passage M, the main damping passage M, or a bypass passage, and then through the damping force control valve 20 to the expansion-side chamber R1. Furthermore, the liquid in the cylinder 1 increases in displacement due to the piston rod 2 entering the cylinder 1, and the excess liquid passes through the compression-side damping valve 53 and is discharged from the compression-side chamber R2 to the tank 50. When the shock absorber D1 is contracting, the excess liquid always becomes excess in the cylinder 1 and moves from the cylinder 1 to the tank 50.

[0070] 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 damping force control valve 20, and resistance is applied to the flow of fluid from the compression-side chamber R2 to the tank 50 by the compression-side damping valve 53, 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 D1 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 D1 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. When the amount of current supplied to the damping force control valve 20 is changed to change the degree of opening of the damping force control valve 20, the resistance applied to the flow of fluid when the fluid passes through the damping force control valve 20 changes.

[0071] Specifically, during the contraction operation of the shock absorber D1, when the damping force control valve 20 is open, the fluid passes through the main damping passage M and the damping force control valve 20. However, when the damping force control valve 20 is closed, the bypass passage is blocked, and the fluid cannot pass through the damping force control valve 20, 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 20 to open it and the amount of current supplied is increased, the degree of opening of the damping force control valve 20 increases, and the flow rate of fluid passing through the bypass passage increases, thereby reducing the proportion of fluid passing through the main damping passage M. Therefore, during the contraction operation when the contraction speed is in the low-speed range, the damping force characteristics generated by the shock absorber D1 can be changed within a range from soft characteristics when the damping force control valve 20 is at its maximum opening to hard characteristics generated mainly by the main damping passage M and the compression-side damping valve 53 when the damping force control valve 20 is closed, by adjusting the amount of current supplied to the damping force control valve 20. Furthermore, when the shock absorber D1 is contracting, excess liquid in the cylinder 1 passes through the compression side damping valve 53 and flows from the compression side chamber R2 to the tank 50. 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 53. Therefore, the shock absorber D1 can generate a higher compression side damping force than the shock absorber D, which has an air chamber G separated by a free piston 19 inside the cylinder 1.

[0072] As described above, the shock absorber D1 in another embodiment includes a tank 50 for storing liquid, a discharge passage 51 connecting the compression side chamber R2 and the tank 50, an intake passage 52 connecting the tank 50 and the compression side chamber R2, a compression side damping valve 53 provided in the discharge passage 51 to provide resistance to the flow of liquid from the compression side chamber R2 to the tank 50, and an intake side valve 54 provided in the intake passage 52 to allow the flow of liquid from the tank 50 to the compression side chamber R2.

[0073] According to the shock absorber D1 configured in this manner, the discharge passage 51 is provided with the compression side damping valve 53, and the suction passage 52 is provided with the suction side valve 54, so that the pressure in the compression side chamber R2 can be increased to a level equal to or higher than the tank pressure during the contraction operation, thereby generating a high damping force. As described above, according to the shock absorber D1 of the other embodiment, a high damping force can be generated during the contraction operation while ensuring a wide damping force adjustment range.

[0074] 5, the tank 50 is provided independently of the cylinder 1. However, although not shown in detail, an outer tube may be provided that is disposed on the outer periphery of the cylinder 1 and forms an annular tank between the cylinder 1 and the outer tube, and the tank may be filled with liquid and gas. In this case, the liquid and gas do not need to be separated by an elastic partition wall or the like, and the discharge passage 51, the suction passage 52, the compression side damping valve 53, and the suction side valve 54 may be provided in a valve case that is installed at the lower end of the cylinder 1. In this way, the tank 50 may be provided independently of the cylinder 1, or may be formed by the cylinder 1 and the outer tube.

[0075] Furthermore, in this embodiment, the connection passage P3 is always connected to the compression-side passage P2 regardless of the open / close state of the damping force control valve 20, and the tank 50 is only required to be connected to the compression-side chamber R2. Therefore, as in the shock absorber D2 of another embodiment shown in FIG. 6 , the connection passage P3 provided in the bracket 6 and the tank 50 may be connected by a discharge passage 51 and a suction passage 52, and a compression-side damping valve 53 may be provided in the discharge passage 51, and a suction-side valve 54 may be provided in the suction passage 52. Therefore, the tank 50 may be provided integrally with the bracket 6, or may be connected to the bracket 6 through piping. Like the shock absorber D1, the shock absorber D2 configured in this manner can generate a high damping force by increasing the pressure in the compression-side chamber R2 to or above the tank pressure during compression. As described above, the shock absorbers D1 and D2 of the other embodiments can generate a high damping force during compression while ensuring a wide damping force adjustment range. Furthermore, in the shock absorber D2, the tank 50 communicates with the compression-side chamber R2 via the connection passage P3, so when the bracket 6 is connected to the body of a saddle-riding type vehicle, the piping connecting the tank 50 and the bracket 6 can be shortened, or the tank 50 can be installed integrally with the bracket 6, making it easier to adopt a layout in which the tank 50 is disposed on the vehicle body side, improving the mountability of the shock absorber D2 to saddle-riding type vehicles. Note that the valve housing 21 is cylindrical and is open not only at the base end where the spool 22 is accommodated but also at the tip end where the plug 40 is attached and detached. Therefore, when connecting the tank 50 to the connection passage P3, a joint of the piping connected to the tank 50 can be attached to the inner periphery of the tip end of the valve housing 21 instead of the plug 40, and the tank 50 can be easily connected to the connection passage P3.

[0076] 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.

[0077] 1... cylinder, 2... piston rod, 3... piston, 6... bracket, 20... damping force adjustment valve, 22... spool (valve body), 23... solenoid (actuator), 25... inner pipe, 26... outer pipe, 50... tank, 51... discharge passage, 52... discharge passage, 53... compression side damping valve, 54... suction side valve, D, D1... shock absorber, M... main damping passage, P1... extension side passage, P2... compression side passage, P3... connecting passage, R1... extension side chamber, R2... compression side chamber

Claims

1. A shock absorber comprising: a cylinder; a hollow 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 main damping passage that provides resistance to a flow of liquid moving between the extension-side chamber and the compression-side chamber; an extension-side passage provided in the piston rod and connected to the extension-side chamber; a compression-side passage provided in the piston rod and connected to the compression-side chamber; a bracket connected to the tip of the piston rod on the side opposite to the cylinder, and having a connecting passage that connects the extension-side passage and the compression-side passage; and a damping force adjustment valve provided on the bracket and positioned midway along the connecting passage.

2. A shock absorber according to claim 1, wherein the piston rod has an inner pipe that forms the compression-side passage inside, and an outer pipe that covers the outer periphery of the inner pipe and forms the extension-side passage between the inner pipe and the outer pipe.

3. A shock absorber according to claim 1, wherein the damping force control valve has a valve body arranged in the connecting passage, and an actuator attached to the bracket for driving the valve body.

4. A shock absorber as claimed in claim 1, wherein the bracket has a rod mounting portion connected to the piston rod, a connecting portion connectable to a saddle-ride type vehicle, and a valve holding portion to which the damping force adjustment valve is attached, and the valve holding portion is located between the rod mounting portion and the connecting portion and at a position eccentric to the axis of the piston rod.

5. A shock absorber as claimed in any one of claims 1 to 4, comprising: a tank for storing liquid; a discharge passage communicating the compression side chamber with the tank; a suction passage communicating the tank with the compression side chamber; a compression side damping valve provided in the discharge passage to provide resistance to the flow of liquid from the compression side chamber towards the tank; and a suction side valve provided in the suction passage to allow the flow of liquid from the tank towards the compression side chamber.

6. A shock absorber as set forth in claim 6, wherein the connecting passage is always in communication with the compression side chamber, and the tank is in communication with the compression side chamber via the connecting passage in the bracket.

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