Hydraulic shock absorber

Abstract

A hydraulic shock absorber (10) includes: a cylinder (16) extending from a lower end section (13a) of an axle-side tube (13) into a vehicle-body-side tube (11); a first rod (40) extending from an upper end section (11a) of the vehicle-body-side tube (11) into the cylinder (16); a piston (30) linked to the first rod (40); and a second rod (50) extending from the piston (30) to a lower end section (16a) of the cylinder (16). The interior of the cylinder (16) is divided into a first hydraulic chamber (71) by the piston (30) and a first partition (80) and into a second hydraulic chamber (72) by the piston (30) and a second partition (90). The sealability of the first partition (80) is lower than the sealability of the second partition (90).

Description

Hydraulic shock absorber

[0001] The present invention relates to a hydraulic shock absorber that is particularly suitable for use in a saddle-ride type vehicle on which a passenger straddles the vehicle.

[0002] Hydraulic shock absorbers with a telescopic structure between a body tube and an axle tube are used in suspension systems mounted on saddle-ride vehicles such as motorcycles and tricycles. For example, a so-called cartridge-type hydraulic shock absorber is used in a front fork. This shock absorber has a cylinder (cartridge) inside the axle tube, a piston with a valve slidably installed inside the cylinder, and a rod connected to the piston that is attached to the body tube.

[0003] In conventional cartridge-type front forks, two variable damping force devices are required to ensure adjustment ranges for both the extension and compression damping forces, which can lead to increased costs. Therefore, development of so-called double-rod hydraulic shock absorbers, in which two rods are provided on both sides of the piston, has been promoted. With a double-rod hydraulic shock absorber, there is no movement of hydraulic oil within the cylinder due to the volume of the rods moving in and out. This also makes it possible to suppress pressure fluctuations of the hydraulic oil within the cylinder. A double-rod hydraulic shock absorber is known, for example, from Patent Document 1.

[0004] The hydraulic shock absorber known from Patent Document 1 has a cylinder disposed inside an axle-side tube, a piston slidably disposed inside the cylinder, and a first rod and a second rod connected to both ends of the piston. The upper end of the cylinder is partitioned by a first partition wall. The lower end of the cylinder is partitioned by a second partition wall. The first rod extends upward from the piston, penetrates the first partition wall, and is connected to the upper end of the vehicle-side tube. The second rod extends downward from the piston, penetrates the second partition wall. The cylinder has inside it a first oil chamber (upper chamber) partitioned by the piston and the first partition wall, and a second oil chamber (lower chamber) partitioned by the piston and the second partition wall.

[0005] Furthermore, the space (space portion) defined by the outer circumferential surface of the cylinder and the inner circumferential surface of the axle-side tube can store hydraulic oil. In this space portion, the area above the hydraulic oil level is an air chamber. The air stored in this air chamber provides the air reaction force (air spring effect) of the hydraulic shock absorber.

[0006] The oil level of the hydraulic oil stored in the space is set above the first partition. Therefore, the outer surface of the cylinder and the upper surface of the first partition are immersed in hydraulic oil. The first partition is equipped with a check valve. This check valve allows hydraulic oil to flow into the first oil chamber from above the first partition, but conversely, it prevents hydraulic oil from flowing out from the first oil chamber above the first partition. When the hydraulic oil in the first oil chamber is low, the check valve opens, allowing hydraulic oil to be replenished into the first oil chamber.

[0007] JP 2010-230091 A

[0008] In the hydraulic shock absorber known from Patent Document 1, the level of the hydraulic oil stored in the space (space portion) defined by the outer circumferential surface of the cylinder and the inner circumferential surface of the axle-side tube is required to be set above the first partition. If the upper surface of the first partition is not immersed in the hydraulic oil, air entering the first oil chamber can cause poor damping force generation. Therefore, the level of the hydraulic oil stored in the space portion must be such that at least the upper surface of the first partition is immersed in the hydraulic oil. This is disadvantageous because it restricts the degree of freedom in setting the air reaction force (air spring effect) of the hydraulic shock absorber. Therefore, there is room for improvement in properly managing the damping force generated when the hydraulic shock absorber expands or contracts.

[0009] An object of the present invention is to provide a technology that can appropriately manage the damping force generated when a double-rod type hydraulic shock absorber performs an expansion / contraction operation.

[0010] After extensive research, the inventors of the present invention have found that it is possible to prevent air from being trapped in the upper first oil chamber when the hydraulic shock absorber is installed in the vehicle body. They have also found that the air can be bled from the sealing portion of the first bulkhead, thereby preventing air from being trapped in the upper first oil chamber. The present invention was completed based on these findings.

[0011] According to the present disclosure, there is provided a hydraulic system including a telescopic vehicle body side tube and an axle side tube disposed on the vehicle body side and the wheel side, respectively; a cylinder extending from a lower end of the axle side tube into the interior of the vehicle body side tube; a first rod extending from an upper end of the vehicle body side tube into the interior of the cylinder; a piston connected to the first rod and slidable against the inner wall of the cylinder; a second rod extending from the piston to the lower end of the cylinder; and a piston located inside the cylinder and closer to the lower end of the axle side tube than the piston, partitioning and sealing the interior of the cylinder into a second oil chamber. a first partition wall located inside the cylinder and closer to the upper end of the body-side tube than the piston, dividing and sealing the interior of the cylinder into a first oil chamber and having lower sealing properties than the second partition wall; a first reservoir partitioned by the outer surface of the cylinder and the inner surface of the axle-side tube and capable of storing hydraulic oil; a second reservoir partitioned inside the cylinder by the lower end of the cylinder and the second partition wall, capable of storing hydraulic oil; and a connecting passage connecting the first reservoir and the second reservoir.

[0012] The present disclosure can provide a technique that can appropriately manage the damping force generated when a double-rod type hydraulic shock absorber performs an expansion / contraction operation.

[0013] Fig. 4 is a side view in cross section of a main part of a hydraulic shock absorber according to an embodiment. Fig. 5 is a schematic view of the hydraulic shock absorber shown in Fig. 1. Fig. 6 is an enlarged view of part 6 of Fig. 1. Fig. 7 is an enlarged view of part 7 of Fig. 1. Fig. 8 is a perspective view of the second partition wall, the connecting mechanism, and the periphery of the check valve shown in Fig. 4. Fig. 9 is an enlarged view of part 10 of Fig. 1. Fig. 10 is a perspective view of the spring guide shown in Fig. 3. Fig. 11 is a damping force characteristic diagram of the hydraulic shock absorber shown in Fig. 1.

[0014] An embodiment of the present invention will be described below with reference to the accompanying drawings. Note that the embodiment shown in the accompanying drawings is an example of the present invention, and the present invention is not limited to this embodiment. In the description, "up" and "down" refer to the up and down positions based on the state in which the hydraulic shock absorber is mounted on a saddle-ride type vehicle. In addition, in the drawings, "Up" refers to the top and "Dn" refers to the bottom.

[0015] <Embodiment> A hydraulic shock absorber 10 according to an embodiment will be described with reference to Figs.

[0016] 1 and 2, the hydraulic shock absorber 10 is used in a motorcycle, which is a type of saddle-ride vehicle (not shown) on which a rider straddles. Hereinafter, a motorcycle may be referred to as a "saddle-ride vehicle."

[0017] The hydraulic shock absorber 10 is of a telescopic type and includes a cylindrical vehicle body side tube 11 (first tube 11) connectable to a vehicle body side bracket (not shown), and a cylindrical axle side tube 13 (second tube 13) connected to an axle side bracket 12. An axle side bracket 12 can be connected to an axle for a wheel (not shown). The axle side tube 13 is fitted into the vehicle body side tube 11 so as to be movable relative to the vehicle body side tube 11. An upper end 11a of the vehicle body side tube 11 is closed by, for example, a closing member 14 (cap member 14).

[0018] Referring also to FIG. 3, the lower end 13a of the axle side tube 13 is fitted into and fixed to the axle side bracket 12, and is closed by, for example, an annular closing member 15 (bottom member 15).

[0019] Here, the stroke in which the hydraulic shock absorber 10 contracts is referred to as the compression stroke, and the stroke in which the hydraulic shock absorber 10 extends is referred to as the extension stroke. In this embodiment, the hydraulic shock absorber 10 will be described as an inverted type configuration in which the axle-side tube 13 advances and retreats relative to the vehicle-body-side tube 11. However, the hydraulic shock absorber 10 also includes an upright type configuration in which the vehicle-body-side tube 11 advances and retreats relative to the axle-side tube 13.

[0020] 1 and 2, the hydraulic shock absorber 10 further includes a cylinder 16 that extends from a lower end 13a of the axle-side tube 13 (e.g., the axle-side bracket 12) into the inside of the vehicle-side tube 11. As shown in Fig. 3, a lower end 16a of the cylinder 16 is fitted into an annular bottom member 15, extends further downward, and is closed by a bottom cap 17, which also fixes the cylinder 16 to the axle-side bracket 12.

[0021] 3, the hydraulic shock absorber 10 includes a compression coil spring 21 that biases the vehicle body side tube 11 and the axle side tube 13 in a direction separating them from each other, and a cylindrical spring guide 22 that guides the inner peripheral surface 21a of the coil of the compression coil spring 21. The compression coil spring 21 and the spring guide 22 are located between the inner peripheral surface 13b of the axle side tube 13 and the outer peripheral surface 16b of the cylinder 16.

[0022] The spring guide 22 is a pipe-shaped member. A lower end 22a of the spring guide 22 is provided with a flange 22b that supports a lower end surface 21b of the compression coil spring 21. The flange 22b is a flat plate-shaped portion whose diameter increases from the lower end 22a of the spring guide 22. A lower end surface 22c of the flange 22b overlaps the closure member 15 and is supported by the closure member 15. As shown in FIG. 2 , the upper end of the compression coil spring 21 is supported by a pipe-shaped spring bearing portion 23 that extends downward from the cap member 14 at the upper end 11a of the vehicle body tube 11.

[0023] 2, the hydraulic shock absorber 10 has a so-called double-rod configuration, which includes two rods 40, 50 (a first rod 40 and a second rod 50) on both axial sides of the piston 30. The two rods 40, 50 are pipe-shaped members located on the center line CL of the piston 30.

[0024] 4, the piston 30 is slidable relative to the inner circumferential surface 16c of the cylinder 16. The piston 30 includes a piston body 31 that is slidable relative to the inner circumferential surface 16c of the cylinder 16, and a pipe-shaped piston shaft 32 that passes through the piston body 31 and is positioned on the center line CL. The piston shaft 32 is fixed to the piston body 31.

[0025] 2, the first rod 40 extends from the upper end 11a of the vehicle body side tube 11 into the cylinder 16. For example, an upper end 41 of the first rod 40 is connected to a drive unit 140 provided in the cap member 14, and is thereby provided at the upper end 11a of the vehicle body side tube 11. A lower end 42 of the first rod 40 is connected to the upper end 32a of the piston shaft 32 via a control valve 130. Details of the control valve 130 and the drive unit 140 will be described later.

[0026] The second rod 50 extends from the piston 30 to the lower end 16a of the cylinder 16. The lower end 51 of the second rod 50 is a free end that is not fixed to any location. The upper end 52 of the second rod 50 is connected to the lower end 32b of the piston shaft 32 by a connecting mechanism 60 (see FIG. 5) so as to be swingable about the center line CL of the piston 30.

[0027] As shown in Figure 5, the connecting mechanism 60 comprises a connecting base material 61 attached to the lower end 32b of the piston shaft 32, a support part 62 removably attached to the connecting base material 61, and a hook part 63 that hooks the upper end part 52 of the second rod 50 to the support part 62 in a swingable manner.

[0028] The connecting base material 61 is a cylindrical member with a bottom that opens toward the second rod 50, and the bottom 61a is attached to the lower end 32b of the piston shaft 32 by a connecting member 64 such as a nut.

[0029] The support part 62 is a cylindrical member, and is attached by fastening, such as by screwing, to the inner peripheral surface of the cylindrical part 61 a of the connecting base material 61. An annular swing support part 62 b having a smaller diameter than the inner peripheral surface 62 a is integrally formed on the inner peripheral surface 62 a of the support part 62.

[0030] The latch portion 63 protrudes radially from the outer peripheral surface 52 a of the upper end portion 52 of the second rod 50 over the entire circumference of this outer peripheral surface 52 a. For example, the latch portion 63 is formed by a retaining ring fitted onto the outer peripheral surface 52 a of the upper end portion 52 of the second rod 50.

[0031] By hooking the hook portion 63 provided on the second rod 50 to the swing support portion 62b, the upper end surface 53 of the second rod 50 is in contact with or close to the axial end surface 64a of the connecting member 64. Therefore, the upper end portion 52 of the second rod 50 is supported by at least one of the end surface 64a of the connecting member 64 and the swing support portion 62b of the support portion 62 so as to be swingable in all directions about the center line CL of the piston 30, that is, is supported in a floating manner. In this way, the second rod 50 is connected to the piston 30 so as to be swingable about the center line CL of the piston 30.

[0032] As shown in FIG. 2 , the interior of the cylinder 16 is divided by the piston 30 into two oil chambers 71, 72 (an upper first oil chamber 71 and a lower second oil chamber 72). More specifically, the cylinder 16 is provided with a first partition wall 80 and a second partition wall 90 inside. The first partition wall 80 is located closer to the upper end of the body-side tube 11 than the piston 30. The second partition wall 90 is located closer to the lower end of the axle-side tube 13 than the piston 30. The piston 30 and the first partition wall 80 divide and seal the interior of the cylinder 16 into the first oil chamber 71. The piston 30 and the second partition wall 90 divide and seal the interior of the cylinder 16 into the second oil chamber 72.

[0033] 4, the lower end 42 of the first rod 40, the upper end 32a of the piston shaft 32, and the control valve 130 are located in the first oil chamber 71. The upper end 52 of the second rod 50, the lower end 32b of the piston shaft 32, and the connecting mechanism 60 are located in the second oil chamber 72.

[0034] First, the second partition wall 90 will be described. As shown in Figures 3 and 4, the second partition wall 90 is supported by a partition wall support portion 91. This partition wall support portion 91 is formed by a pipe that extends from the lower end portion 16a of the cylinder 16 into the interior of the cylinder 16. The lower end portion 91a of the partition wall support portion 91 is closed by a bottom cap 17, and is fixed to the axle-side bracket 12 by this bottom cap 17.

[0035] As shown in FIG. 5 , the second partition 90 is a cylindrical member fixed to the upper end 91 b of the partition support portion 91. The upper end 52 of the second rod 50 penetrates the interior of the second partition 90 and enters the second oil chamber 72. The second partition 90 supports the second rod 50 so that it can move axially, and can therefore be considered to be configured as a rod guide. In other words, the second partition 90 is configured as a second rod guide that supports the second rod 50. The second partition 90 includes a bushing 92 (bearing 92) that supports the second rod 50 so that it can slide axially, as well as two second seal members 93, 94 (an inner seal member 93 and an outer seal member 94) that partition and seal the interior of the cylinder 16 into the second oil chamber 72.

[0036] The internal seal member 93 is a rubber member, such as an oil seal, that provides a liquid-tight seal between the outer peripheral surface 52 a of the upper end portion 52 of the second rod 50 and the inner peripheral surface 90 a of the second partition wall 90. The external seal member 94 is a rubber member, such as an O-ring, that provides a liquid-tight seal between the inner peripheral surface 16 c of the cylinder 16 and the outer peripheral surface 90 b of the second partition wall 90. The second seal members 93 and 94 provide a seal, so the second partition wall 90 has high sealing performance.

[0037] Next, the first partition 80 will be described. As shown in FIG. 6 , the first partition 80 is fixed to the upper end 16d of the cylinder 16. The first rod 40 passes through the interior of the first partition 80. The first partition 80 supports the first rod 40 so that it can move in the axial direction, and can therefore be considered to be configured as a rod guide. In other words, the first partition 80 is configured as a first rod guide that supports the first rod 40.

[0038] The first partition 80 includes a bushing 83 (bearing 83) that supports the first rod 40 so that it can slide in the axial direction. The first partition 80 also includes a cylindrical partition main body 81 with a bottom that is fixed to the cylinder 16, a lid 82 that closes the open end of the partition main body 81, and an annular holder 84 that is located inside the partition main body 81 and holds the bushing 83. The bottom plate 81a and the lid 82 of the partition main body 81 have holes 81b and 82a that pass through the first rod 40.

[0039] The outer peripheral surface 81c of the partition wall main body 81 and the lid 82 are fitted into the inner peripheral surface 16c of the cylinder 16. There is only a small gap C1 between the outer peripheral surface 81c of the partition wall main body 81 and the inner peripheral surface 16c of the cylinder 16, and this gap is not sealed by a sealing member. The size δ1 of the gap C1 between the outer peripheral surface 81c of the partition wall main body 81 and the inner peripheral surface 16c of the cylinder 16 is set, for example, as follows: It is preferable that the size δ1 of the gap C1 be set to an extent that the hydraulic oil stored in the first oil chamber 71 does not flow out of the gap C1 due to the viscosity of the hydraulic oil, or to an extent that the generation of the damping force by the hydraulic oil in the first oil chamber 71 is not affected.

[0040] It is preferable that the gap C2 between the outer peripheral surface 43 of the first rod 40 and the inner peripheral surface 83a of the bush 83 is set to a small size δ2 within a range in which the first rod 40 can slide smoothly relative to the bush 83.

[0041] The bushing 83 is fitted into the inner peripheral surface 84a of the retaining portion 84. The outer peripheral surface 84b of the retaining portion 84 is supported by the inner peripheral surface 81d of the partition wall main body 81 via an annular elastic body 85 (e.g., an O-ring 85) made of an elastic material. The elastic body 85 is fitted into the inner peripheral surface 84a of the retaining portion 84. The inner peripheral surface 81d of the partition wall main body 81 supports the outer peripheral surface of the elastic body 85 so as to limit movement and elastic deformation of the elastic body 85 in a direction intersecting the center line CL. By using the elastic body 85, the outer peripheral surface 84b of the retaining portion 84 is supported in a manner that does not directly contact the inner peripheral surface 81d of the partition wall main body 81, i.e., is supported in a floating manner. The gap between the inner peripheral surface 81d of the partition wall main body 81 and the outer peripheral surface 84b of the retaining portion 84 is sealed by the elastic body 85.

[0042] As is clear from the above description, the sealing property of the first partition wall 80 is set to be lower than the sealing property of the second partition wall 90. Note that the sealing structures of the first partition wall 80 and the second partition wall 90 are not limited to the above configurations, and it is sufficient that the sealing property of the first partition wall 80 is set to be lower than the sealing property of the second partition wall 90.

[0043] As shown in Figure 3, the hydraulic shock absorber 10 further includes two reservoirs 101, 102 (a first reservoir 101 and a second reservoir 102) capable of storing hydraulic oil, and a communication passage 103 that connects the first reservoir 101 and the second reservoir 102. The first reservoir 101 is defined by the inner circumferential surface 13b of the axle-side tube 13 and the outer circumferential surface 16b of the cylinder 16. The second reservoir 102 is defined inside the cylinder 16 by the lower end 16a of the cylinder 16 and a second partition wall 90 (see Figure 4). The communication passage 103 is formed by a through-hole provided in the cylinder 16. The communication passage 103 may be referred to as the "first through-hole 103" as appropriate.

[0044] 3 and 7, the lower end surface 22c of the flange 22b of the spring guide 22 has at least one groove 22d that can guide the hydraulic oil stored in the first reservoir 101 to the first through-hole 103 (communication passage 103). This groove 22d intersects with the center line CL of the spring guide 22 and penetrates the flange 22b in the radial direction.

[0045] 7, the closure member 15, which is overlapped with the lower end surface 22c of the flange 22b, preferably has a guide recess 15a so as to be able to guide the hydraulic oil flowing from the groove 22d to the first through-hole 103. The guide recess 15a has a shape that tapers, for example, from the lower end surface 22c of the flange 22b toward the opposite side along the center line CL.

[0046] 3, the hydraulic oil stored in the first reservoir 101 flows to the second reservoir 102 through the groove 22d of the spring guide 22, the first through-hole 103, and the second through-hole 91c formed in the lower end 91a of the partition wall support part 91. The hydraulic oil stored in the second reservoir 102 can flow into the interior through the opening 54 at the lower end of the second rod 50.

[0047] As shown in Figures 2 and 5, the second rod 50 has a check valve 105 therein. Furthermore, the second rod 50 has an oil inlet / outlet 55 on the upper end surface 53 side (the piston 30 side) of the check valve 105. This oil inlet / outlet 55 penetrates the second rod 50 radially and communicates with the second oil chamber 72. The check valve 105 is configured to allow hydraulic oil to flow from the second reservoir 102 to the second oil chamber 72 in response to a pressure difference between the second oil chamber 72 and the second reservoir 102, while preventing flow in the reverse direction. For example, the check valve 105 can open in response to a pressure difference between the second oil chamber 72 and the second reservoir 102 that occurs when the pressure of the hydraulic oil in the second oil chamber 72 drops.

[0048] Next, the flow of hydraulic oil in the hydraulic shock absorber 10 will be described with reference to Figure 2. The piston 30 (piston body 31) is equipped with an extension-side check valve 111, an extension-side throttle passage 112, a compression-side check valve 113, and a compression-side throttle passage 114. During the extension stroke of the hydraulic shock absorber 10, hydraulic oil flowing from the first oil chamber 71 to the second oil chamber 72 passes through the extension-side check valve 111 and the extension-side throttle passage 112, thereby enabling the extension-side throttle passage 112 to generate a damping force. During the compression stroke of the hydraulic shock absorber 10, hydraulic oil flowing from the second oil chamber 72 to the first oil chamber 71 passes through the compression-side check valve 113 and the compression-side throttle passage 114, thereby enabling the compression-side throttle passage 114 to generate a damping force.

[0049] When the hydraulic shock absorber 10 is in an extension stroke (when the cylinder 16 extends in the direction of the arrow Re relative to the piston 30), the volume of the upper first oil chamber 71 decreases and the volume of the lower second oil chamber 72 increases. The pressure in the first oil chamber 71 becomes higher than the pressure in the second oil chamber 72. Some of the excess hydraulic oil in the first oil chamber 71 passes through the extension-side check valve 111 and the extension-side throttle passage 112 and flows into the second oil chamber 72. At this time, a damping effect is generated by the extension-side throttle passage 112. Furthermore, some of the excess hydraulic oil in the first oil chamber 71 passes through a bypass passage 120 and a control valve 130 (described later) and flows into the second oil chamber 72. The control valve 130 applies flow resistance to the hydraulic oil passing through the bypass passage 120, thereby generating a damping effect.

[0050] When the hydraulic shock absorber 10 is in a compression stroke (when the cylinder 16 contracts in the direction of arrow Rc relative to the piston 30), the volume of the upper first oil chamber 71 increases and the volume of the lower second oil chamber 72 decreases. The pressure in the second oil chamber 72 becomes higher than the pressure in the first oil chamber 71. Some of the excess hydraulic oil in the second oil chamber 72 passes through the compression side check valve 113 and the compression side throttle passage 114 and flows into the first oil chamber 71. At this time, a damping effect is generated by the compression side throttle passage 114. Furthermore, some of the excess hydraulic oil in the second oil chamber 72 passes through the bypass passage 120 and the control valve 130 and flows into the first oil chamber 71. The control valve 130 applies flow resistance to the hydraulic oil passing through the bypass passage 120, thereby generating a damping effect.

[0051] The hydraulic shock absorber 10 includes a bypass passage 120 that bypasses the piston 30 and connects the first oil chamber 71 and the second oil chamber 72, and a control valve 130 that applies flow resistance to the hydraulic oil flowing through the bypass passage 120 and that is capable of adjusting the applied flow resistance. The control valve 130 is disposed in either the first oil chamber 71 or the second oil chamber 72, for example, in the first oil chamber 71.

[0052] The bypass passage 120 is an oil passage from the oil inlet / outlet 55 of the second rod 50 through the inside of the pipe-shaped piston shaft 32 and the inside of the control valve 130 to the oil inlet / outlet 132 a of the control valve 130 .

[0053] As shown in Figure 4, the control valve 130 functions as a variable throttle valve and is driven by a drive unit 140 (see Figure 2). This drive unit 140 is configured by an actuator or a manually operated mechanism. The drive unit 140 has an operating rod 141 (valve stem 141) that drives and controls the control valve 130. This operating rod 141 passes through the inside of the first rod 40 so as to be able to advance and retreat in the axial direction. The opening degree of the control valve 130 can be adjusted according to the advancement distance of the operating rod 141.

[0054] The control valve 130 is removably attached to the lower end 42 of the first rod 40. The control valve 130 includes a valve disc holder 131 attached to the lower end 42 of the first rod 40 and a cylindrical valve housing 132 with a bottom provided on the underside of the valve disc holder 131. The valve disc holder 131 and the valve housing 132 define a valve storage section 133 inside. The valve disc holder 131 holds a valve disc 134 located on the center line CL of the first rod 40 (on the center line CL of the piston 30). The valve disc 134 is pushed by an operating rod 141 of the drive unit 140, allowing it to move along the center line CL.

[0055] The valve housing 132 has at least one oil inlet / outlet port 132a that can communicate between the valve accommodating portion 133 and the first oil chamber 71. A bottom plate 132b of the valve housing 132 is connected to the upper end portion 32a of the piston shaft 32. The upper end portion 32a of the piston shaft 32 is provided with a valve seat 135 that faces the valve element 134.

[0056] The opening degree of the control valve 130 changes according to the amount of movement of the valve element 134 relative to the valve seat 135. The amount of damping force generated by the control valve 130 can be adjusted by adjusting the amount of movement of the valve element 134 with a drive device 140 (see FIG. 2). The valve element 134 is biased by a coil spring 136 in a direction away from the valve seat 135.

[0057] Next, the damping force characteristics of the hydraulic shock absorber 10 will be described with reference to Figures 2 and 8. Figure 8 shows the adjustment ranges Vw1 and Vw2 of the damping force Df generated by the hydraulic shock absorber 10, with the horizontal axis representing the moving speed Vp of the piston 30 and the vertical axis representing the damping force Df generated by the hydraulic shock absorber 10, which are achieved by providing the bypass path 120 and the control valve 130.

[0058] The characteristic line Df11 indicates the minimum damping force characteristic of the hydraulic shock absorber 10 during the extension stroke (extension side). The characteristic line Df12 indicates the maximum damping force characteristic of the hydraulic shock absorber 10 during the extension stroke. The maximum adjustment range of the damping force Df during the extension stroke is Vw1.

[0059] The characteristic line Df21 indicates the minimum damping force characteristic of the hydraulic shock absorber 10 during the compression stroke (compression side). The characteristic line Df22 indicates the maximum damping force characteristic of the hydraulic shock absorber 10 during the compression stroke. The maximum adjustment range of the damping force Df during the compression stroke is Vw2.

[0060] Although the hydraulic shock absorber 10 of this embodiment uses a single piston 30, by combining the bypass path 120 and the control valve 130, it is possible to set the maximum adjustment range Vw1 of the damping force Df during the extension stroke and the maximum adjustment range Vw2 of the damping force Df during the compression stroke to be the same. In other words, the hydraulic shock absorber 10 of this embodiment can ensure the adjustment range (adjustment range) of both the extension-side damping force and the compression-side damping force. Furthermore, only one control valve 130 (damping force variable device 130) is required. For example, the characteristic line Df21 of the minimum damping force characteristic during the compression stroke can be set to be the same as the characteristic line Df11 of the minimum damping force characteristic during the extension stroke. Furthermore, the characteristic line Df22 of the maximum damping force characteristic during the compression stroke can be set to be the same as the characteristic line Df12 of the maximum damping force characteristic during the extension stroke.

[0061] The hydraulic shock absorber 10 described above can be summarized as follows.

[0062] Referring to Figure 2, according to this embodiment, firstly, the hydraulic shock absorber 10 includes a telescopic body-side tube 11 and an axle-side tube 13 that are arranged on the body side and the wheel side, respectively, and a cylinder 16 that extends from a lower end 13a of the axle-side tube 13 into the interior of the body-side tube 11.

[0063] Furthermore, the hydraulic shock absorber 10 includes a first rod 40 extending from the upper end 11a of the vehicle body side tube 11 into the interior of the cylinder 16, a piston 30 connected to this first rod 40 and capable of sliding against the inner surface 16c of the cylinder 16, and a second rod 50 extending from this piston 30 to the lower end 16a of the cylinder 16.

[0064] Furthermore, the hydraulic shock absorber 10 includes a second partition 90 located inside the cylinder 16 and closer to the lower end of the axle side tube 13 than the piston 30, which divides and seals the inside of the cylinder 16 into a second oil chamber 72, and a first partition 80 located inside the cylinder 16 and closer to the upper end of the body side tube 11 than the piston 30, which divides and seals the inside of the cylinder 16 into a first oil chamber 71, and which has lower sealing properties than the second partition 90.

[0065] Furthermore, the hydraulic shock absorber 10 includes a first reservoir 101 that is partitioned by the outer peripheral surface 16b of the cylinder 16 and the inner peripheral surface 13b of the axle side tube 13 and is capable of storing hydraulic oil, a second reservoir 102 that is partitioned inside the cylinder 16 by the lower end 16a of the cylinder 16 and the second partition wall 90 and is capable of storing hydraulic oil, and a communication passage 103 that connects the first reservoir 101 and the second reservoir 102.

[0066] As described above, the hydraulic shock absorber 10 has a so-called double-rod type configuration, in which two rods 40, 50 are provided on both axial sides of the piston 30. The interior of the cylinder 16 is partitioned into a first oil chamber 71 by the piston 30 and an upper first partition wall 80, and into a second oil chamber 72 by the piston 30 and a second partition wall 90. When the hydraulic shock absorber 10 is attached to a vehicle body (not shown), the first partition wall 80 is located above the second partition wall 90. The sealing ability (hermetic sealing ability) of the first partition wall 80 is set lower than that of the second partition wall 90. When the hydraulic shock absorber 10 performs a compression operation, air (including air bubbles) that has entered the second oil chamber 72 is sent from the second oil chamber 72 to the first oil chamber 71 by the piston 30 together with the hydraulic oil. When the hydraulic shock absorber 10 performs an extending operation, the air that has entered the first oil chamber 71 is discharged to the outside (first reservoir 101) through the first partition wall 80, which has poor sealing properties.

[0067] For example, as shown in FIG. 6 , the sealing portion of the first partition 80 is formed by a minute gap C1 between the outer peripheral surface 81c of the partition body 81 and the inner peripheral surface 16c of the cylinder 16, and a minute gap C2 between the outer peripheral surface 43 of the first rod 40 and the inner peripheral surface 83a of the bushing 83. The sizes δ1 and δ2 of the gaps C1 and C2 are extremely small. The sealing portion (gaps C1 and C2) of the first partition 80 can function as an air bleeder. Therefore, the air accumulation phenomenon that occurs in the first oil chamber 71 and the second oil chamber 72 shown in FIG. 2 can be prevented, and the first oil chamber 71 and the second oil chamber 72 can be filled with hydraulic oil regardless of the oil level of the hydraulic oil stored in the first reservoir 101. The damping force generated when the hydraulic shock absorber 10 extends is not affected by the oil level of the hydraulic oil stored in the first reservoir 101. In other words, the degree of freedom in setting the amount of hydraulic oil stored in the first oil chamber 71 can be increased, making it possible to appropriately manage the damping force generated when the hydraulic shock absorber 10 performs an extension operation. Therefore, in the double-rod type hydraulic shock absorber 10, the damping force generated when the hydraulic shock absorber 10 performs an extension / contraction operation can be appropriately managed. Moreover, because the sealing ability of the first partition 80 is simply set to be lower than the sealing ability of the second partition 90, there is no need to add a separate structure for bleeding air from the first oil chamber 71.

[0068] Therefore, in a double-rod type hydraulic shock absorber 10 having two rods 40, 50 on both axial sides of the piston 30, the damping force generated when the hydraulic shock absorber 10 performs expansion and contraction operations can be appropriately managed.

[0069] In addition, since there is no longer any restriction on the height of the hydraulic oil level stored in the first reservoir 101, it is possible to appropriately set the amount of air stored in the air chamber above this oil level. By setting this amount of air, it is possible to increase the degree of freedom in setting the air reaction force (air spring effect) of the hydraulic shock absorber 10.

[0070] See Fig. 6. Secondly, preferably, in the hydraulic shock absorber 10 described above, the first partition 80 is configured by a first rod guide that supports the first rod 40. This first rod guide 80 (first partition 80) has a first sealing portion that partitions the interior of the cylinder 16 into a first oil chamber 71 and seals it. For example, the sealing portion of the first partition 80 is configured by a gap C1 between an outer peripheral surface 81c of the partition main body 81 and an inner peripheral surface 16c of the cylinder 16, and a gap C2 between an outer peripheral surface 43 of the first rod 40 and an inner peripheral surface 83a of the bushing 83.

[0071] The first sealing portion provided in the first rod guide 80 (first partition wall 80) can seal the first partition wall 80. Therefore, there is no need to provide a separate sealing member for partitioning and sealing the inside of the cylinder 16 into the first oil chamber 71.

[0072] See Figure 5. Thirdly, preferably, in the hydraulic shock absorber 10 described in any one of the first and second aspects, the second partition 90 is configured by a second rod guide that supports the second rod 50. This second rod guide 90 (second partition 90) is equipped with second seal members 93, 94 that partition and seal the interior of the cylinder 16 into the second oil chamber 72.

[0073] The second rod guide 90 (second partition 90) is provided with second seal members 93, 94, which can seal the second partition 90. Therefore, there is no need to provide a separate seal member for partitioning the interior of the cylinder 16 into the second oil chamber 72 and sealing it.

[0074] See Figure 5. Fourth, preferably, in the hydraulic shock absorber 10 according to any one of the first to third aspects, the second rod 50 is configured by a pipe. A check valve 105 is provided inside this pipe 50 (second rod 50). This check valve 105 is configured to allow the flow of hydraulic oil from the second reservoir 102 to the second oil chamber 72 in response to the pressure difference between the second oil chamber 72 and the second reservoir 102.

[0075] As air is discharged from the first oil chamber 71 and the second oil chamber 72, the amount of hydraulic oil stored inside each oil chamber 71, 72 decreases. However, the check valve 105 opens in response to the pressure difference between the second oil chamber 72 and the second reservoir 102 that occurs when the hydraulic shock absorber 10 performs an extension operation. Therefore, the decrease in hydraulic oil stored in the second oil chamber 72 can be quickly replenished from the second reservoir 102 to the second oil chamber 72.

[0076] See Fig. 5. Fifth, preferably, in the hydraulic shock absorber 10 according to any one of the first to fourth embodiments, the second rod 50 is coupled to the piston 30 so as to be swingable about the center line CL of the piston 30. In other words, the second rod 50 is coupled to the piston 30 by a coupling mechanism 60.

[0077] In this way, the second rod 50 is configured to be swingable relative to the center line CL of the piston 30 (so-called floating support configuration), and is therefore able to absorb misalignment, parallelism accuracy, and tilt relative to the center line CL of the piston 30. This makes it possible to alleviate the fit tolerance of the second rod 50 with respect to the piston 30 and the second partition wall 90 and reduce frictional resistance.

[0078] See Figures 2 and 5. Sixth, preferably, the hydraulic shock absorber 10 according to any one of the first to fifth embodiments further includes a bypass passage 120 that connects the first oil chamber 71 and the second oil chamber 72, and a control valve 130 that applies flow resistance to the hydraulic oil flowing through the bypass passage 120 and that is capable of adjusting the applied flow resistance.

[0079] Therefore, the control valve 130 can impart flow path resistance to the hydraulic oil flowing from the first oil chamber 71 to the second oil chamber 72 via the bypass path 120, and can also impart flow path resistance to the hydraulic oil flowing from the second oil chamber 72 to the first oil chamber 71 via the bypass path 120. Therefore, both the damping force generated when the hydraulic shock absorber 10 performs an extension operation and the damping force generated when the hydraulic shock absorber 10 performs a compression operation can be adjusted within a sufficient adjustment range by using one control valve 130.

[0080] See Fig. 2. Seventh, preferably, in the hydraulic shock absorber 10 according to any one of the first to sixth aspects, the communication passage 103 is configured by a through hole provided in the cylinder 16.

[0081] The cylinder 16, together with the vehicle body side tube 11 and the axle side tube 13, is a main structure that constitutes the hydraulic shock absorber 10. This cylinder 16 is effectively utilized to provide a through hole 103 (first through hole 103) that communicates between the first reservoir 101 and the second reservoir 102. This through hole 103 makes it possible to provide a communication passage with a simple configuration.

[0082] See Fig. 3. Eighth, preferably, the hydraulic shock absorber 10 according to the seventh aspect includes a compression coil spring 21 that biases the vehicle-body-side tube 11 and the axle-side tube 13 in a direction separating them from each other, and a cylindrical spring guide 22 that guides the inner peripheral surface 21b of the coil of the compression coil spring 21. The compression coil spring 21 and the spring guide 22 are located between the outer peripheral surface 16b of the cylinder 16 and the inner peripheral surface 13b of the axle-side tube 13. A lower end 22a of the spring guide 22 includes a flange 22b that supports the lower end surface 21b of the compression coil spring 21. A lower end surface 22c of the flange 22b has a groove 22d that can guide the hydraulic oil stored in the first reservoir 101 to the through-hole 103.

[0083] As described above, the spring guide 22 has a groove 22d in the lower end surface 22c of the flange 22b that supports the lower end surface 21b of the compression coil spring 21. This groove 22d makes it possible to guide the hydraulic oil that has accumulated in the first reservoir 101 to the through-hole 103. By effectively utilizing the spring guide 22, the hydraulic oil that has accumulated in the first reservoir 101 is guided to the second reservoir 102 via the through-hole 103. This increases the degree of freedom in the arrangement of the spring guide 22.

[0084] The hydraulic shock absorber 10 according to the present invention is not limited to the above embodiment as long as it exhibits the functions and effects of the present invention. For example, the control valve 130 may be configured to impart flow resistance to the hydraulic oil passing through the bypass passage 120.

[0085] The hydraulic shock absorber 10 of the present invention is suitable for application to a front fork mounted on a saddle-ride type vehicle.

[0086] DESCRIPTION OF SYMBOLS 10...hydraulic shock absorber, 11...vehicle body side tube, 11a...upper end portion, 13...axle side tube, 13a...lower end portion, 13b...inner peripheral surface, 16...cylinder, 16a...lower end portion, 16b...outer peripheral surface, 16c...inner peripheral surface, 21...compression coil spring, 21a...inner peripheral surface of coil, 22...spring guide, 22a...lower end portion, 22b...flange, 22c...lower end surface of flange, 22d...groove, 30...piston, 40...first rod, 50...second rod, 71...first oil chamber, 72...second oil chamber, 80...first partition wall (first rod guide), 90...second partition wall (second rod guide), 93, 94...second seal member, 101...first reservoir, 102...second reservoir 103...communication passage (through hole), 105...check valve, 120...bypass passage, 130...control valve, CL...center line of piston.

Claims

1. A telescopic type vehicle body side tube and axle side tube arranged on the vehicle body side and wheel side, respectively; a cylinder extending from the lower end of the axle side tube into the vehicle body side tube; a first rod extending from the upper end of the vehicle body side tube into the cylinder; a piston connected to the first rod and capable of sliding against the inner wall of the cylinder; a second rod extending from the piston to the lower end of the cylinder; a second partition located inside the cylinder and closer to the lower end of the axle side tube than the piston, dividing and sealing the inside of the cylinder into a second oil chamber; a first partition located inside the cylinder and closer to the upper end of the vehicle body side tube than the piston, dividing and sealing the inside of the cylinder into a first oil chamber, the first partition having a lower sealing ability than the second partition; a first reservoir partitioned by the outer circumferential surface of the cylinder and the inner circumferential surface of the axle side tube, and capable of storing hydraulic oil; a second reservoir partitioned by the lower end of the cylinder and the second partition wall inside the cylinder, capable of storing hydraulic oil; and a communication passage connecting the first reservoir and the second reservoir.

2. A hydraulic shock absorber as described in claim 1, wherein the first partition is constituted by a first rod guide that supports the first rod, and the first rod guide is provided with a first seal portion that separates and seals the inside of the cylinder into the first oil chamber.

3. A hydraulic shock absorber as described in claim 1, wherein the second partition is constituted by a second rod guide that supports the second rod, and the second rod guide is provided with a second sealing member that partitions and seals the inside of the cylinder into the second oil chamber.

4. A hydraulic shock absorber as described in claim 1, wherein the second rod is constituted by a pipe, and a check valve is provided inside the pipe to allow the flow of hydraulic oil from the second reservoir to the second oil chamber in response to the pressure difference between the second oil chamber and the second reservoir.

5. The hydraulic shock absorber according to claim 1, wherein said second rod is connected to said piston so as to be pivotable about a center line of said piston.

6. A hydraulic shock absorber as described in claim 1, further comprising a bypass passage connecting the first oil chamber and the second oil chamber, and a control valve that imparts a flow resistance to the hydraulic oil flowing through the bypass passage and is capable of adjusting the applied flow resistance.

7. The hydraulic shock absorber according to claim 1, wherein the communication passage is constituted by a through hole provided in the cylinder.

8. A hydraulic shock absorber as described in claim 7, further comprising a compression coil spring that biases the vehicle body side tube and the axle side tube in a direction separating them from each other, and a cylindrical spring guide that guides the inner surface of the coil of the compression coil spring, wherein the compression coil spring and the spring guide are located between the outer surface of the cylinder and the inner surface of the axle side tube, the lower end of the spring guide is provided with a flange that supports the lower end surface of the compression coil spring, and the lower end surface of the flange has a groove that is capable of guiding hydraulic oil accumulated in the first reservoir to the through hole.

Images