Shock absorber

Abstract

To provide a shock absorber which can ease rapid extending action caused by kick back.SOLUTION: A shock absorber D of the invention includes: a cylinder 1; a rod member 2 having a piston 4 which is inserted into the cylinder 1 in a manner that allows movement in an axial direction and partitions the inside of the cylinder 1 into an extending side chamber R1 and a pressure side chamber R2; an extending side attenuation passage 5 which is provided at the rod member 2 and allows communication between the extending side chamber R1 and the pressure side chamber R2; an extending side damping valve EV which is provided at the rod member 2, has a leaf valve (a valve body) 7 which opens or closes the extending side attenuation passage 5, and provides resistance to flow of liquid that passes from the extending side chamber R1 to the pressure side chamber R2; and a coil spring (an elastic body) 8 which biases the leaf valve (the valve body) 7 in a direction in which the extending side attenuation passage 5 is closed when the rod member 2 moves a predetermined distance H or longer relative to the cylinder 1 from a neutral position toward a contraction side stroke end.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] A shock absorber includes, for example, a cylinder, a piston rod movably inserted into the cylinder, a piston connected to the piston rod and movably inserted into the cylinder, dividing the inside of the cylinder into an extension side chamber and a compression side chamber filled with hydraulic oil, a reservoir tank that is installed to the side of the cylinder to compensate for the volume of the piston rod moving in and out of the cylinder and stores liquid and gas inside, and a cylindrical rebound cushion attached to the outer periphery of the tip of the piston rod, and is interposed between the body and rear wheel of a saddle-type vehicle to generate a damping force that suppresses vibration of the body when the body expands and contracts (see, for example, Patent Document 1).

[0003] In addition, in conventional shock absorbers, when the piston rod enters the cylinder during the contraction operation and contracts to near the stroke end on the contraction side, the rebound cushion comes into contact with the rod guide or rebound stopper that closes the open end of the cylinder on the rod side and is compressed, exerting a resilient force, which absorbs the impact when the shock absorber is fully contracted. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-248679 A Summary of the Invention [Problem to be solved by the invention]

[0005] Since conventional shock absorbers are incorporated into saddle-type vehicles together with suspension springs, when fully compressed, the suspension springs are fully compressed and generate a large elastic force in addition to the elastic force of the rebound cushion, so that when the shock absorbers are fully compressed or compressed to the vicinity of the stroke end and then start to extend, a phenomenon called kickback occurs in which the shock absorbers rapidly extend when the shock absorbers rapidly extend after being compressed while the saddle-type vehicle is traveling over an uneven road surface with a large difference in elevation, causing a sudden change in the vehicle body posture of the saddle-type vehicle, and therefore there is a demand for mitigating such a sudden change in the vehicle body posture.

[0006] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a shock absorber capable of mitigating the sudden extension action caused by kickback. [Means for solving the problem]

[0007] In order to solve the above problems, the shock absorber of the present invention includes a cylinder, a rod member having a piston that is inserted into the cylinder so as to be axially movably and that divides the inside of the cylinder into an extension side chamber and a compression side chamber, an extension side damping passage provided in the rod member and communicating between the extension side chamber and the compression side chamber, an extension side damping valve provided in the rod member and having a valve body that opens and closes the extension side damping passage and provides resistance to the flow of liquid passing from the extension side chamber to the compression side chamber, and an elastic body that urges the valve body in a direction to close the extension side damping passage when the rod member moves a predetermined distance or more from the neutral position toward the contraction side stroke end relative to the cylinder.

[0008] In the shock absorber configured in this manner, when the shock absorber begins to extend after the distance moved from the neutral position of the rod member toward the stroke end on the contraction side reaches or exceeds a predetermined distance, the extension-side damping valve receives the biasing force of the elastic body and provides a large resistance to the flow of liquid, generating a high damping force that hinders the extension operation. Therefore, according to the shock absorber, even in a situation in which the suspension spring is greatly compressed as the shock absorber contracts and generates a large elastic force in the direction to extend the shock absorber, or in a situation in which the cushion is compressed in addition to the suspension spring and generates a large elastic force in the direction to extend the shock absorber, the shock absorber can generate a high damping force that hinders the extension operation.

[0009] Also, the extension-side damping passage in the shock absorber may be a port provided in the piston, and a leaf valve in which a valve body is stacked on the piston and an inner periphery is fixed to a rod member. According to the shock absorber configured in this way, compared to a shock absorber having a typical configuration equipped with an extension-side damping valve in which a valve body that opens and closes a port of the piston is a leaf valve, the addition of an elastic body can mitigate the sudden extension action caused by the kickback of the shock absorber, so that kickback countermeasures can be implemented inexpensively even in existing shock absorbers.

[0010] Furthermore, the shock absorber may include a cushion that is attached to the rod member and is compressed between the rod member and the cylinder when the rod member moves a predetermined distance or more from the neutral position toward the contraction side stroke end relative to the cylinder. With this shock absorber configured in this manner, when the cushion is compressed and a sudden extension action occurs due to kickback, the damping force exerted by the extension side damping valve is increased by the bias of the coil spring, while in the normal use range where the shock absorber does not contract to the vicinity of the contraction side stroke end and kickback does not occur, the bias of the coil spring is not generated and the damping force exerted by the extension side damping valve does not become excessive, so that a ride comfort in the normal use range can be ensured.

[0011] Furthermore, the elastic body in the shock absorber may bias the outer periphery of the leaf valve toward the piston. According to the shock absorber configured in this manner, the elastic body biases the outer periphery of the leaf valve toward the piston, and therefore a biasing force that biases the leaf valve in a direction to close the extension-side damping passage can be efficiently applied, so that the force that biases the rod member in the extension direction by the elastic body can be kept small, and the sudden extension operation caused by kickback can be effectively mitigated.

[0012] Furthermore, the shock absorber may include an annular guide member attached to the rod member and disposed on the compression side chamber side of the leaf valve, and an annular plunger attached to the outer periphery of the guide member so as to be axially movable and facing the leaf valve, and an elastic body may be attached to the cylinder and bias the leaf valve via the plunger. In the shock absorber configured in this manner, even if the leaf valve side end of the coil spring swings in the radial direction due to vibration input to the shock absorber, the plunger is guided by the guide member so that it always abuts on the leaf valve at the same position and the biasing force of the elastic body can be applied to the leaf valve. Therefore, when the coil spring biases the leaf valve, the resistance that the extension side damping valve provides to the flow of liquid is stable, and the variation in the damping force at each extension operation can be suppressed, and the function of mitigating sudden extension due to kickback can be stably generated.

[0013] The elastic body in the shock absorber may have one end attached to the cylinder and the other end having an annular slider that is in sliding contact with the inner periphery of the cylinder and faces the leaf valve in the axial direction. With this shock absorber configured in this way, the slider always abuts against the leaf valve at the same position and can apply the biasing force of the elastic body to the leaf valve, so that when the coil spring biases the leaf valve, the resistance that the extension damping valve provides to the flow of liquid is stable, and the variation in damping force at each extension operation can be suppressed, and the function of mitigating sudden extension due to kickback can be stably generated.

[0014] Furthermore, the elastic body in the shock absorber may be a coil spring with one end attached to the cylinder, the plunger may have a tubular portion on the compression side chamber side that can be inserted into the inner periphery of the coil spring, and the tubular portion may have a tapered surface with a tapered outer periphery. According to the shock absorber configured in this manner, the tapered surface on the outer periphery of the tip of the tubular portion allows the tubular portion to smoothly enter and exit the coil spring, so that there is no need to worry about the eccentricity of the leaf valve side end of the coil spring causing it to ride up on the tubular portion and apply excessive biasing force to the leaf valve, which would promote kickback, and kickback can be mitigated stably.

[0015] Furthermore, the shock absorber may include a holder that holds one end of the elastic body, and the holder may have a fixing member that is in close contact with the inner periphery of the cylinder and is fixed to the cylinder. With a shock absorber configured in this manner, the elastic body can be fixed in a state in which it is suspended from the cylinder by the holder, and even if the shock absorber is installed on a saddle-ride type vehicle by connecting the cylinder to the vehicle body side of the saddle-ride type vehicle, the function of mitigating sudden extension due to kickback is not lost. Effect of the Invention

[0016] According to the shock absorber of the present invention, it is possible to mitigate the sudden extension action caused by kickback. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view of a shock absorber according to one embodiment. [Diagram 2] FIG. 2 is a partially enlarged cross-sectional view of the shock absorber according to one embodiment. [Diagram 3] FIG. 3 is a partially enlarged cross-sectional view of a shock absorber according to a first modified example of the embodiment. [Figure 4] FIG. 4 is a partially enlarged cross-sectional view of a shock absorber according to a second modified example of the embodiment. [Diagram 5] FIG. 5 is a partially enlarged cross-sectional view of a shock absorber according to a third modified example of the embodiment. [Figure 6] FIG. 6 is a partially enlarged cross-sectional view of a shock absorber according to a fourth modified example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The present invention will be described based on the embodiment shown in the drawings. As shown in Fig. 1, a shock absorber D in one embodiment includes a cylinder 1, a rod member 2 having a piston 4 inserted axially movably into the cylinder 1 and dividing the cylinder 1 into an expansion side chamber R1 and a compression side chamber R2, an expansion side damping passage 5 provided in the rod member 2 and communicating the expansion side chamber R1 and the compression side chamber R2, an expansion side damping valve EV provided in the rod member 2 and having a leaf valve 7 as a valve body for opening and closing the expansion side damping passage 5 and providing resistance to the flow of liquid passing from the expansion side chamber R1 to the compression side chamber R2, and a coil spring 8 as an elastic body for biasing the leaf valve 7 in a direction to close the expansion side damping passage 5 when the rod member 2 moves from the neutral position toward the stroke end on the contraction side relative to the cylinder 1 by a predetermined distance H or more. Although not shown, the shock absorber D is, for example, interposed between the vehicle body and the rear wheel of a saddle-type vehicle such as a motorcycle, and generates a damping force during expansion and contraction to suppress vibration of the vehicle body.

[0019] Each part of the shock absorber D will be described below. The cylinder 1 is cylindrical, with its upper end opening closed by an upper bracket 10 attached to the upper end in Fig. 1, and an annular rod guide 11 attached to the inner periphery of the lower end in Fig. 1. A screw portion 1a into which an annular upper suspension spring bearing 20 and a nut 21 are screwed is provided on the outer periphery of the cylinder 1 on the upper end side in Fig. 1. The upper suspension spring bearing 20 can move up and down relative to the cylinder 1 by rotating it in the manner of a feed screw relative to the screw portion 1a, and is fixed to the screw portion 1a by tightening the nut 21.

[0020] The rod member 2 includes a piston rod 3 that is inserted into the cylinder 1 so as to be movable in the vertical direction in FIG. 1, which is the axial direction, and a piston 4 that is attached to the outer periphery of the upper end of the piston rod 3, which is the tip end in FIG.

[0021] The piston rod 3 has at its upper end a small diameter portion 3a that is smaller in diameter than the lower side, and at its lower end a bracket 3b that can be connected to a swing arm that holds the rear wheel of a saddle-type vehicle (not shown), and an annular lower suspension spring bearing 3c that is stacked above the bracket 3b. A cylindrical cushion 12 that abuts against the upper end of the bracket 3b is attached to the outer periphery of the lower end of the piston rod 3 in FIG.

[0022] The piston rod 3 is inserted into the cylinder 1 through the inner circumference of the rod guide 11, and its outer circumference is in sliding contact with the inner circumference of a cylindrical bush 11a fixed to the inner circumference of the rod guide 11, so that the piston rod 3 can move in the axial direction while being guided by the rod guide 11. In addition to the bush 11a, an annular seal member 11b that is in sliding contact with the outer circumference of the piston rod 3 is provided on the inner circumference of the rod guide 11, and the inside of the cylinder 1 is sealed by the seal member 11b. In this embodiment, the seal member 11b is provided on the inner circumference of the rod guide 11, but a seal member that seals between the cylinder 1 and the piston rod 3 may be provided below the rod guide 11 independently of the rod guide 11.

[0023] A suspension spring S, which is a coil spring disposed on the outer periphery of the cylinder 1 and the rod member 2, is interposed between the upper suspension spring bearing 20 and the lower suspension spring bearing 3c, and the suspension spring S always biases the rod member 2 outwardly from the cylinder 1, that is, in the direction of extending the shock absorber D. When the shock absorber D having the suspension spring S is interposed between the body and the rear wheel of a saddle-type vehicle not shown in the figure, the suspension spring S elastically supports the body, and the rod member 2 is positioned at a neutral position relative to the cylinder 1, as shown in FIG. 1. The position of the piston 4 relative to the cylinder 1 when the rod member 2 is disposed at the neutral position relative to the cylinder 1 may be the center of the cylinder 1 or may be other than the center, but is set at least on the lower side in FIG. 1 from the position where the coil spring 8 as an elastic body described later starts biasing the leaf valve 7 as a valve body. FIG. 2 shows the shock absorber D in a state where the rod member 2 has moved a predetermined distance H from the neutral position to the contraction side relative to the cylinder 1.

[0024] Furthermore, when the piston rod 3 penetrates deeply into the cylinder 1 and the shock absorber D contracts to the vicinity of the stroke end on the contraction side, the cushion 12 attached to the outer periphery of the piston rod 3 comes into contact with the rod guide 11 and is compressed, generating a resilient force that suppresses the contraction of the shock absorber D. Note that, although the shock absorber D of this embodiment employs a structure in which the cushion 12 comes into contact with the rod guide 11, a structure in which an annular stopper facing the cushion 12 is provided below the rod guide 11 in FIG. 1 and the cushion 12 comes into contact with the stopper and is compressed may also be employed.

[0025] In addition, an annular piston 4 is attached to the small diameter portion 3a at the upper end of the piston rod 3. The piston 4 is annular, and is attached to the outer periphery of the small diameter portion 3a of the piston rod 3 by a piston nut 15 together with the extension side damping valve EV, a guide member 13, a plunger 14, and a compression side damping valve CV.

[0026] When the piston 4 is inserted into the cylinder 1, the piston 4 divides the inside of the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2 filled with liquid, and can move in the axial direction within the cylinder 1 together with the piston rod 3. Note that the liquid filled in the extension-side chamber R1 and the compression-side chamber R2 is, for example, hydraulic oil, but may be a liquid other than hydraulic oil.

[0027] As shown in FIG. 2, the piston 4 is provided with ports 4a and 4b formed along the axial direction, a valve seat 4c protruding in the axial direction from the upper end in FIG. 2 to surround the outlet end of the port 4a, and a valve seat 4d protruding in the axial direction from the lower end in FIG. 2 to surround the outlet end of the port 4b. The port 4a forms an extension side damping passage 5, and the port 4b forms a compression side damping passage 6.

[0028] In the shock absorber D of this embodiment, the extension side damping valve EV is provided with a leaf valve 7 which is formed by stacking a plurality of annular plates, and whose inner periphery is fixed to the outer periphery of the small diameter portion 3a of the piston rod 3 in the rod member 2 and is stacked on the upper end of the piston 4 in FIG. 2, and the inner periphery is fixed to the piston rod 3 to allow the outer periphery to bend. Thus, the extension side damping valve EV has the leaf valve 7, whose outer periphery is a free end, as a valve body, and can open and close the extension side damping passage 5 by seating on and off the valve seat 4c of the piston 4, and provides resistance to the flow of liquid from the extension side chamber R1 to the compression side chamber R2 while opening the extension side damping passage 5, and closes the extension side damping passage 5 against the flow of liquid from the compression side chamber R2 to the extension side chamber R1 to prevent the flow of the liquid.

[0029] More specifically, the leaf valve 7 is constructed by stacking multiple annular plates with gradually decreasing outer diameters above a group of multiple annular plates 7a having the largest outer diameter in FIG. 2, and the outer diameter of the group of annular plates 7a is set to a size that enables it to abut against the valve seat 4c and close the port 4a.

[0030] As shown in FIG. 2, the guide member 13 is stacked via a small diameter spacer 17 on the upper side in FIG. 2, which is the compression side chamber side of the leaf valve 7 in the extension side damping valve EV, and is provided with a stopper portion 13a which is annular and fits onto the outer periphery of the small diameter portion 3a so as to restrict the deflection of the leaf valve 7 when the amount of deflection of the outer periphery of the leaf valve 7 becomes large by abutting against the outer periphery of the back surface, which is the upper surface in FIG. 2 of the annular plate stacked at the top of the annular plate group 7a which has the largest outer diameter of the leaf valve 7, and a guide tube 13b which is connected to the upper side of the outer periphery of the stopper portion 13a.

[0031] The annular stopper portion 13a has a through hole 13a1 penetrating in the axial direction, so that even if the leaf valve 7 bends and abuts against the uppermost annular plate of the annular plate group 7a, the space between the leaf valve 7 is not closed and is always connected to the compression side chamber R2.

[0032] The plunger 14 includes a cylindrical portion 14a which is in sliding contact with the outer periphery of the guide tube 13b of the guide member 13, a flange-shaped spring bearing portion 14b which is provided at the lower end of the cylindrical portion 14a in FIG. 2 and which faces the outer periphery of the annular plate group 7a in the axial direction, and an annular protrusion portion 14c which protrudes radially from the inner periphery of the lower end of the cylindrical portion 14a to the inner periphery and is in sliding contact with the outer periphery of the stopper portion 13a.

[0033] The cylinder portion 14a is provided on the upper side in FIG. 2, which is the compression side chamber side of the plunger 14, and has a tapered surface 14a1 on the outer periphery of the tip end, which is the upper end in FIG. 2, whose outer diameter gradually decreases as it goes upward, and a through hole 14a2 on the lower end side in FIG. 2, slightly above the annular protrusion 14c, which faces the outer periphery of the stopper portion 13a. The plunger 14 slides the inner periphery of the cylinder portion 14a on the outer periphery of the guide tube 13b in the guide member 13, slides the annular protrusion 14c on the outer periphery of the stopper portion 13a, and communicates the space B between the lower end of the guide tube 13b and the annular protrusion 14c with the compression side chamber R2 through the through hole 14a2. In this way, the plunger 14 does not seal the space B between the lower end of the guide tube 13b and the annular protrusion 14c, so that it can move smoothly in the up and down direction in FIG. 2, which is the axial direction, relative to the guide member 13. In addition, as the plunger 14 moves upward relative to the guide member 13 in Figure 2, the annular protrusion 14c eventually comes into contact with the lower end of the guide tube 13b of the guide member 13, restricting its upward movement relative to the guide member 13 in Figure 2, and preventing it from falling off the guide member 13.

[0034] The spring bearing portion 14b is a ring having an outer diameter larger than that of the cylindrical portion 14a, and is provided at the lower end of the cylindrical portion 14a, and includes an annular pressing portion 14b1 protruding from the outer periphery of the lower end in FIG. 2 toward the leaf valve 7. The inner diameter of the pressing portion 14b1 is larger than the outer diameter of the annular plate stacked above the annular plate group 7a of the leaf valve 7, and smaller than the outer diameter of the annular plate group 7a, and the lower end surface of the pressing portion 14b1 faces the upper end surface of the annular plate group 7a in the axial direction, that is, the outer periphery avoiding the annular plates above the annular plate group 7a. Therefore, when the plunger 14 moves downward relative to the guide member 13, the pressing portion 14b1 can abut against the outer periphery of the annular plate group 7a. Even if the plunger 14 abuts against the annular plate group 7a, the space A between the leaf valve 7 and the guide member 13 is connected to the compression side chamber R2 by the through hole 13a1, so that the space A is not closed by the plunger 14 abutting against the leaf valve 7.

[0035] In addition, the plunger 14 in this embodiment has a through hole 14a2 in the cylindrical portion 14a to prevent the closure of space B between the lower end of the guide tube 13b and the annular convex portion 14c. However, since the space A between the stopper portion 13a and the leaf valve 7 is connected to the compression side chamber R2 by the through hole 13a1, a groove may be provided on the inner circumference of the annular convex portion 14c or on the outer circumference of the guide tube 13b of the guide member 13 to connect space B and space A and prevent the closure of space B.

[0036] Next, in the shock absorber D of this embodiment, the compression side damping valve CV is a laminated leaf valve that is configured by laminating a plurality of annular plates, and the inner periphery is fixed to the outer periphery of the small diameter portion 3a of the piston rod 3 in the rod member 2 to allow deflection on the outer periphery side, and is laminated at the lower end of the piston 4 in FIG. 2 and can open and close the compression side damping passage 6 by seating on and off the valve seat 4d. Therefore, the compression side damping valve CV provides resistance to the flow of liquid from the compression side chamber R2 to the expansion side chamber R1 while opening the compression side damping passage 6, and closes the compression side damping passage 6 against the flow of liquid that attempts to flow from the expansion side chamber R1 to the compression side chamber R2, thereby preventing the flow of the liquid.

[0037] The compression side damping valve CV, piston 4, extension side damping valve EV, guide member 13 and plunger 14 configured in this manner are assembled in this order to the outer periphery of the small diameter portion 3a of the piston rod 3, and then fixed to the piston rod 3 by a piston nut 15 which is screwed to the tip of the small diameter portion 3a.

[0038] Returning to the above, the upper bracket 10, which closes the upper part of the cylinder 1 in Figure 1, is equipped with a topped cylindrical cap 10a that closes the upper end of the cylinder 1 in Figure 1, a valve housing 10b extending laterally from the cap 10a, and a tank 10c that is connected to the tip of the valve housing 10b and is positioned to the side of the cylinder 1 to form a reservoir for storing gas and liquid therein.

[0039] The cap 10a is cylindrical with a top, and is screwed to the screw portion 1a formed on the outer periphery of the upper end of the cylinder 1 in Figure 1 above the upper suspension spring bearing 20 in Figure 1 to close the upper end of the cylinder 1, and is provided with a bracket 10a1 for connecting the shock absorber D to the body of the saddle-type vehicle.

[0040] The tank 10c is cylindrical and accommodates a free piston 10c1 that is movable inwardly in the axial direction and divides the inside of the tank 10c into an air chamber G filled with gas and a liquid chamber L filled with liquid.

[0041] The valve housing 10b is provided with a passage 10b1 that opens from above the tank 10c to the lower end of the top of the cap 10a and connects the liquid chamber L and the compression side chamber R2, a compression side main damping valve MV that is provided in the passage 10b1 and provides resistance to the flow of liquid from the compression side chamber R2 to the liquid chamber L, and a suction check valve SV that is provided in parallel with the compression side main damping valve MV with respect to the passage 10b1 and allows only the flow of liquid from the liquid chamber L to the compression side chamber R2.

[0042] The coil spring 8 as an elastic body is fixed to the cylinder 1 via a holder 16. The holder 16 includes a cylindrical main body 16a with a top, an annular flange 16b provided on the outer periphery of the lower end of the main body 16a and facing the inner periphery of the cylinder 1, and a rubber ring 16c as a fixing member accommodated in an annular groove 16b1 provided on the outer periphery of the flange 16b and in close contact with the inner periphery of the cylinder 1.

[0043] The main body 16a has an annular seat portion 16a2 that supports one end of the coil spring 8 on the outer periphery of the lower end of the top portion 16a1, and a hole 16a3 provided in the center of the top portion 16a1, and fits around the outer periphery of the coil spring 8 to hold the coil spring 8. An annular groove 16b1 is formed around the outer periphery of the flange portion 16b along the circumferential direction, and an annular rubber ring 16c is accommodated in the annular groove 16b1. When the holder 16 is inserted into the inner periphery of the upper end of the cylinder 1, the rubber ring 16c attached to the flange portion 16b facing the inner periphery of the cylinder 1 is in a compressed state and comes into close contact with the inner periphery of the cylinder 1, generating a frictional force between the rubber ring 16c and the cylinder 1, and the holder 16 is fixed in the cylinder 1. Note that the fixing member is not limited to the rubber ring 16c, as long as it can be in close contact with the inner periphery of the cylinder 1 to fix the holder 16. It is not limited to the rubber ring 16c, and may be made of something other than rubber.

[0044] In this way, one end of the coil spring 8 is fixed to the cylinder 1 via the holder 16, and the other end, which is the lower end in Fig. 1, faces the upper end surface in Fig. 2 of the spring receiving portion 14b of the plunger 14 in the axial direction. Then, as shown in Fig. 1, when the rod member 2 is placed in a neutral position with respect to the cylinder 1, there is a predetermined distance H between the lower end in Fig. 1, which is the other end of the coil spring 8, and the spring receiving portion 14b of the plunger 14 in a state in which the pressing portion 14b1 is in contact with the outer periphery of the annular plate group 7a of the leaf valve 7, and when the rod member 2 moves the predetermined distance H from the neutral position toward the stroke end on the contraction side with respect to the cylinder 1, the other end of the coil spring 8 comes into contact with the spring receiving portion 14b of the plunger 14. When the rod member 2 moves further toward the contraction-side stroke end after the coil spring 8 comes into contact with the spring receiving portion 14b, the coil spring 8 is compressed, and the elastic force generated by the compressed coil spring 8 is transmitted to the leaf valve 7 via the plunger 14, urging the leaf valve 7 in a direction to close the extension-side damping passage 5.

[0045] The inner diameter of the coil spring 8 is set to a diameter that allows it to be loosely fitted around the outer periphery of the tubular portion 14a of the plunger 14, so that the tubular portion 14a of the plunger 14 can move in and out of the inner periphery of the other end of the coil spring 8, and the other end of the coil spring 8 is guided by the tubular portion 14a and can abut against the spring receiving portion 14b without shifting in the radial direction. The tapered surface 14a1 provided on the elastic body side end of the tubular portion 14a allows the tubular portion 14a to move in and out of the coil spring 8 smoothly.

[0046] The shock absorber D is configured as described above, and its operation will be described below. First, the operation when the shock absorber D is extended will be described. When the rod member 2 moves downward in FIG. 1 relative to the cylinder 1 and the shock absorber D is extended, the liquid in the expansion-side chamber R1 contracted by the piston 4 bends the leaf valve 7 and passes through the expansion-side damping passage 5 to move to the expansion-side chamber R2. The expansion-side damping valve EV provides resistance to this liquid flow, so the pressure in the expansion-side chamber R1 rises and a difference occurs between the pressure in the expansion-side chamber R1 and the pressure in the compression-side chamber R2, and the shock absorber D generates an expansion-side damping force that hinders the extension operation. During the extension operation of the shock absorber D, the piston rod 3 withdraws from the cylinder 1, causing a shortage of liquid in the compression side chamber R2 by the volume of the piston rod 3 withdrawing from the cylinder 1. However, the shortage of liquid is supplied from the liquid chamber L to the compression side chamber R2 as the free piston 10c1 in the tank 10c is displaced in a direction that expands the air chamber G and the suction check valve SV opens.

[0047] Conversely, the operation when the shock absorber D is contracted will be described. When the rod member 2 moves upward in FIG. 1 relative to the cylinder 1 and the shock absorber D is contracted, the liquid in the compression side chamber R2 contracted by the piston 4 passes through the compression side damping passage 6 and moves to the expansion side chamber R1 which is expanded by pushing open the compression side damping valve CV. Since the compression side damping valve CV provides resistance to this liquid flow, the pressure in the compression side chamber R2 rises and a difference occurs between the pressure in the compression side chamber R2 and the pressure in the expansion side chamber R1. Also, when the shock absorber D is contracted, the piston rod 3 enters the cylinder 1, so the liquid in the compression side chamber R2 by the volume of the piston rod 3 entering the cylinder 1 becomes excessive, and the excess liquid moves from the compression side chamber R2 to the liquid chamber L in the tank 10c while being resisted by the compression side main damping valve MV which opens. Therefore, when the shock absorber D is contracting, the shock absorber D generates a damping force that hinders the contraction of the shock absorber D by the compression side main damping valve MV and the compression side damping valve CV.

[0048] Furthermore, when shock absorber D is in the contracting operation and rod member 2 moves a predetermined distance H from the neutral position toward the stroke end on the contraction side relative to cylinder 1, cylindrical portion 14a of plunger 14 is inserted into the inner circumference of the lower end of coil spring 8 fixed to cylinder 1 in FIG. 1, and the lower end of coil spring 8 abuts against spring support portion 14b.

[0049] Furthermore, when the contraction of the shock absorber D progresses and the movement distance of the rod member 2 from the neutral position becomes equal to or greater than the predetermined distance H, the coil spring 8 is compressed according to the movement distance of the rod member 2 from the neutral position to the contraction side, and the coil spring 8 applies a biasing force to the outer periphery of the annular plate group 7a of the leaf valve 7 via the plunger 14, biasing the leaf valve 7 in a direction to close the extension-side damping passage 5, and pressing the leaf valve 7 against the valve seat 4c of the piston 4. The biasing force with which the coil spring 8 biases the leaf valve 7 increases in proportion to the distance obtained by subtracting the predetermined distance H from the movement distance of the rod member 2 from the neutral position.

[0050] Then, when the shock absorber D begins to expand after the distance displaced from the neutral position of the rod member 2 toward the stroke end on the contraction side becomes equal to or greater than the predetermined distance H, the liquid tries to push open the leaf valve 7 in the extension-side damping valve EV and move from the extension-side chamber R1, which is compressed as the shock absorber D expands, to the contraction-side chamber R2, which is expanded. Since the leaf valve 7 is pressed against the valve seat 4c of the piston 4 by the biasing force of the coil spring 8, the biasing force of the coil spring 8 is added to the elastic force that tries to suppress the deflection due to the deflection rigidity of the leaf valve 7 itself, and the degree of opening of the leaf valve 7 becomes smaller. Therefore, the resistance to the flow of liquid passing through the extension-side damping valve EV when the biasing force of the coil spring 8 acts on the leaf valve 7 becomes larger than the resistance to the flow of liquid passing through the extension-side damping valve EV when the biasing force of the coil spring 8 does not act, so the damping force that prevents the extension of the shock absorber D becomes higher, making it difficult for the shock absorber D to expand.

[0051] In this way, when the shock absorber D begins to extend after the distance traveled from the neutral position of the rod member 2 toward the stroke end on the contraction side reaches or exceeds the predetermined distance H, the shock absorber D generates a high damping force to hinder the extension. Therefore, even if the suspension spring S is significantly compressed with the contraction of the shock absorber D to generate a large elastic force in the direction to extend the shock absorber D, or the cushion 12 is also compressed in addition to the suspension spring S to generate a large elastic force in the direction to extend the shock absorber D, the extension-side damping valve EV of the shock absorber D receives the biasing force of the coil spring 8, which is an elastic body, and provides a large resistance to the flow of liquid, so that the shock absorber D generates a high damping force to hinder the extension, slowing down the extension of the shock absorber D and mitigating the sudden extension caused by kickback. The predetermined distance H can be set arbitrarily, but is preferably set so that when the shock absorber D contracts from a state in which the rod member 2 is in a neutral position relative to the cylinder 1 to the vicinity of the stroke end on the contraction side, the suspension spring S is compressed and exerts a large force, or the cushion 12 begins to contract, the coil spring 8 comes into contact with the plunger 14 and biases the leaf valve 7. By setting the predetermined distance H in this manner, when the shock absorber D exhibits a sudden extension action due to kickback, the bias of the coil spring 8 increases the damping force exerted by the extension side damping valve EV, while in the normal range where the shock absorber D does not contract to the vicinity of the stroke end on the contraction side and kickback does not occur, the bias of the coil spring 8 is not applied and the damping force exerted by the extension side damping valve EV does not become excessive, so that the ride comfort in the normal range can be ensured.

[0052] As described above, the shock absorber D of this embodiment includes the cylinder 1, the rod member 2 having the piston 4 that is inserted into the cylinder 1 so as to be axially movable and that divides the inside of the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2, the extension-side damping passage 5 that is provided in the rod member 2 and communicates between the extension-side chamber R1 and the compression-side chamber R2, the extension-side damping valve EV that is provided in the rod member 2 and has a leaf valve (valve body) 7 that opens and closes the extension-side damping passage 5 and provides resistance to the flow of liquid passing from the extension-side chamber R1 to the compression-side chamber R2, and a coil spring (elastic body) 8 that biases the leaf valve (valve body) 7 in a direction to close the extension-side damping passage 5 when the rod member 2 moves a predetermined distance H or more from the neutral position toward the contraction-side stroke end relative to the cylinder 1.

[0053] In the shock absorber D thus configured, when the shock absorber D begins to extend after the distance traveled from the neutral position of the rod member 2 toward the stroke end on the contraction side reaches or exceeds a predetermined distance H, the extension-side damping valve EV of the shock absorber D receives the biasing force of the coil spring (elastic body) 8 and exerts a large resistance to the flow of the liquid, generating a high damping force and hindering the extension. Therefore, according to the shock absorber D of this embodiment, even in a situation in which the suspension spring S is greatly compressed with the contraction of the shock absorber D to generate a large elastic force in the direction to extend the shock absorber D, or in a situation in which the cushion 12 is compressed in addition to the suspension spring S to generate a large elastic force in the direction to extend the shock absorber D, a high damping force that hinders the extension operation is generated, slowing down the extension operation and mitigating the sudden extension operation caused by kickback.

[0054] Although the elastic body is a coil spring 8 as described above, it may be an elastic body other than a coil spring 8 as long as it can bias the leaf valve (valve body) 7 in a direction to close the extension side damping passage 5 when the rod member 2 moves from the neutral position toward the contraction side stroke end relative to the cylinder 1 by a predetermined distance H or more. For example, it may be a cylindrical rubber, a stacked disc spring, a wave washer, or the like.

[0055] Furthermore, in the shock absorber D of this embodiment, the extension-side damping passage 5 may be a port 4a provided in the piston 4, and a leaf valve 7 whose valve body is stacked on the piston 4 and whose inner circumference is fixed to the rod member 2. According to the shock absorber D configured in this manner, compared to the configuration of a shock absorber having a general configuration including the piston 4 and the extension-side damping valve EV in which the valve body that opens and closes the port 4a of the piston 4 is the leaf valve 7, the addition of the coil spring (elastic body) 8 can mitigate the sudden extension action due to kickback of the shock absorber D, so that kickback countermeasures can be implemented at low cost even in existing shock absorbers.

[0056] Furthermore, in the shock absorber D of this embodiment, the coil spring (elastic body) 8 biases the outer periphery of the leaf valve 7 toward the piston 4. Since the coil spring (elastic body) 8 biases the outer periphery of the leaf valve 7 toward the piston 4 in this way, the resistance that the extension side damping valve EV provides to the flow of liquid can be increased even if the biasing force of the coil spring (elastic body) 8 is small, compared to the case where the coil spring (elastic body) 8 biases the inside of the outer periphery of the leaf valve 7. Here, the biasing force of the coil spring (elastic body) 8 biases the rod member 2 in the direction to retract from the cylinder 1, so if the biasing force for biasing the leaf valve 7 is increased, the force for expanding the shock absorber D also increases. However, if the coil spring (elastic body) 8 biases the outer periphery of the leaf valve 7, the resistance that the extension side damping valve EV provides to the flow of liquid can be increased even if the biasing force of the coil spring (elastic body) 8 is reduced. As described above, according to the shock absorber D of this embodiment, a biasing force can be efficiently applied to bias the leaf valve 7 in the direction of closing the extension side damping passage 5, so that the force biasing the rod member 2 in the extension direction by the coil spring (elastic body) 8 can be kept small, and the sudden extension action caused by kickback can be effectively mitigated.

[0057] Furthermore, the shock absorber D of this embodiment includes an annular guide member 13 attached to the rod member 2 and disposed on the compression side chamber side of the leaf valve 7, and an annular plunger 14 attached to the outer periphery of the guide member 13 so as to be axially movable and facing the leaf valve 7, and the coil spring (elastic body) 8 is attached to the cylinder 1 and biases the leaf valve 7 via the plunger 14. In the shock absorber D configured in this manner, even if the lower end of the coil spring 8 in FIG. 1, which is the leaf valve side end, swings in the radial direction due to vibration input to the shock absorber D, the plunger 14 is guided by the guide member 13 and always abuts on the leaf valve 7 at the same position, and the biasing force of the coil spring (elastic body) 8 can be applied to the leaf valve 7. Therefore, in a state in which the coil spring (elastic body) 8 biases the leaf valve 7, the resistance that the extension side damping valve EV provides to the flow of liquid is stable, and the variation in the damping force at each extension operation can be suppressed, and the function of mitigating sudden extension due to kickback can be stably generated. It is also possible to omit the guide member 13 and the plunger 14 and have the coil spring (elastic body) 8 directly contact the leaf valve 7 so that the biasing force of the coil spring (elastic body) 8 acts on the leaf valve 7.

[0058] In the shock absorber D of this embodiment, the elastic body is a coil spring 8 having one end attached to the cylinder 1, the plunger 14 has a tubular portion 14a on the compression side chamber side that can be inserted into the inner periphery of the coil spring 8, and the tubular portion 14a has a tapered surface 14a1 that tapers toward the elastic body side end. According to the shock absorber D configured in this manner, the tapered surface 14a1 provided on the outer periphery of the tip of the tubular portion 14a allows the tubular portion 14a to smoothly enter and exit the coil spring 8, so there is no risk of the coil spring 8 riding on the tubular portion 14a due to eccentricity of the leaf valve side end thereof, causing an excessive biasing force to act on the leaf valve 7, thereby promoting kickback, and kickback can be stably mitigated.

[0059] In the example shown in FIG. 2, the plunger 14 is provided with a tubular portion 14a that can be inserted into the inner periphery of the coil spring 8 so that the coil spring 8 can stably abut against the spring receiving portion 14b of the plunger 14. However, as in the shock absorber D1 of the first modified example shown in FIG. 3, a tubular portion 13c that can be inserted into the inner periphery of the leaf valve side end of the coil spring 8 and that aligns the leaf valve side end of the coil spring 8 may be provided instead of the guide tube 13b of the guide member 13, and a plunger 23 that is annular and has an annular pressing portion 23a at its lower end that protrudes toward the leaf valve 7 may be brought into sliding contact with the outer periphery of the stopper portion 13a. Also, as in a shock absorber D2 of a second modified example shown in FIG. 4, the guide member 13 may be configured with two components, a circular valve stopper 24 and a guide 25 including a circular plate 25a laminated on the valve stopper 24 and a cylindrical portion 25b rising from the outer periphery of the circular plate 25a toward the coil spring 8, and the plunger 26 may be brought into sliding contact with the outer periphery of the valve stopper 24. In the example shown in FIG. 4, the outer diameter of the guide 25 is larger than the diameter of the outer periphery of the valve stopper 24 with which the inner periphery of the plunger 26 slides, so that the guide 25 prevents the plunger 26 from falling off the valve stopper 24. Furthermore, as in a shock absorber D3 of a third modified example shown in FIG. 5, the guide member may be a circular valve stopper 27, and the plunger 28 may be slidably attached to the outer periphery of the circular valve stopper 27.

[0060] In the shock absorbers D1, D2, and D3 configured in this manner, the plunger 14 always abuts against the leaf valve 7 at the same position, allowing the biasing force of the coil spring (elastic body) 8 to act on the leaf valve 7. Therefore, when the coil spring 8 biases the leaf valve 7, the resistance that the extension side damping valve EV provides to the flow of liquid is stable, making it possible to suppress variations in the damping force with each extension operation, and the function of mitigating sudden extension due to kickback can be stably generated.

[0061] Moreover, the shock absorber D of this embodiment is provided with a cushion 12 that is attached to the rod member 2 and is compressed between the rod member 2 and the cylinder 1 when the rod member 2 moves a predetermined distance H or more from the neutral position toward the contraction side stroke end relative to the cylinder 1. According to the shock absorber D configured in this manner, when the cushion 12 is compressed and exhibits a sudden extension action due to kickback, the damping force exerted by the extension side damping valve EV is increased by the bias of the coil spring 8, while in the normal use range where the shock absorber D does not contract to the vicinity of the contraction side stroke end and kickback does not occur, the bias of the coil spring 8 is not applied and the damping force exerted by the extension side damping valve EV does not become excessive, so that the ride comfort in the normal use range can be ensured.

[0062] Furthermore, the shock absorber D of this embodiment is provided with a holder 16 that holds one end of the coil spring (elastic body) 8, and the holder 16 has a rubber ring (fixing member) 16c that is in close contact with the inner circumference of the cylinder 1 and is fixed to the cylinder 1. According to the shock absorber D configured in this manner, the coil spring (elastic body) 8 can be fixed in a state of being suspended from the upper end of the cylinder 1 by the holder 16, and even if the shock absorber D is installed on a saddle-type vehicle by connecting the cylinder 1 to the vehicle body side of the saddle-type vehicle (not shown), the function of mitigating sudden extension due to kickback is not lost. In addition, the top of the holder 16 has a shape that is convex upward in FIG. 1, and when the central part side of the top abuts against the top of the cap 10a, the movement of the holder 16 upward in FIG. 1 with respect to the cylinder 1 is restricted. Therefore, even if the fixed position of the holder 16 relative to the cylinder 1 deviates from the designed position during assembly of the shock absorber D, when the shock absorber D contracts to its maximum contraction, the holder 16 is pushed by the rod member 2 and positioned at a position where it abuts on the top of the cap 10a, making it easy to assemble the coil spring (elastic body) 8 to the cylinder 1 and automatically positioning the coil spring (elastic body) 8 at the designed position as the shock absorber D contracts. The holder 16 may be attached to the inner periphery of the cylinder 1 or to the upper bracket 10.

[0063] 6, the guide member 13 and the plunger 14 may be eliminated, and an annular slider 30 may be provided at the leaf valve side end of the coil spring (elastic body) 8 in sliding contact with the inner periphery of the cylinder 1 and facing the leaf valve 7 in the axial direction. The slider 30 includes an annular fitting portion 30a that is fitted onto the outer periphery of the coil spring (elastic body) 8 and in sliding contact with the inner periphery of the cylinder 1, an annular spring receiving portion 30b that is provided at the lower end of the fitting portion 30a in FIG. 6 and comes into contact with the lower end of the coil spring (elastic body) 8, and a pressing portion 30c that protrudes downward from the lower end of the spring receiving portion 30b and faces the outer periphery of the leaf valve 7 in the axial direction.

[0064] In the shock absorber D4 configured in this manner, the annular slider 30 provided at the leaf valve side end of the coil spring (elastic body) 8 is aligned with the cylinder 1 and does not wobble in the radial direction, and the leaf valve 7 fixed to the rod member 2 is also aligned with the cylinder 1 by the piston 4 sliding against the inner circumference of the cylinder 1. Therefore, when the movement distance of the rod member 2 from the neutral position with respect to the cylinder 1 becomes equal to or greater than the predetermined distance H, the slider 30 and the leaf valve 7, which are aligned with respect to the cylinder 1, come into contact with each other, so that the contact position of the slider 30 with the leaf valve 7 does not change. Therefore, according to the shock absorber D4, the slider 30 always comes into contact with the leaf valve 7 at the same position and the biasing force of the coil spring (elastic body) 8 can be applied to the leaf valve 7. Therefore, in the state in which the coil spring (elastic body) 8 biases the leaf valve 7, the resistance that the extension side damping valve EV gives to the flow of liquid is stable, and the variation in the damping force at each extension operation can be suppressed, and the function of mitigating the sudden extension caused by the kickback can be stably generated.

[0065] In the above description, the valve body in the extension side damping valve EV is annular and is the leaf valve 7 whose inner circumference is fixed to the piston rod 3 of the rod member 2, but it may be a valve body other than a leaf valve, such as a poppet. Also, the extension side damping passage 5 may be formed by a passage that opens from the tip of the piston rod 3 of the rod member 2 and leads to the side facing the extension side chamber R1, and a structure may be adopted in which an elastic body, one end of which is attached to the cylinder 1, biases the valve body that can open and close the extension side damping passage 5 provided in the piston rod 3.

[0066] Although the preferred embodiment of the present invention has been described in detail above, modifications, variations and changes can be made without departing from the scope of the appended claims. [Explanation of symbols]

[0067] DESCRIPTION OF SYMBOLS 1···cylinder, 2···rod member, 4···piston, 4a···port, 5···rebound damping passage, 7···leaf valve (valve body), 8···coil spring (elastic body), 13···guide member, 14, 23, 26, 28···plunger, 14a···tubular portion, 14a1···tapered surface, 16···holder, 16c···rubber ring (fixing member), 24, 27···valve stopper (guide member), 25···guide (guide member), 30···slider, D, D1, D2, D3, D4···shock absorber, EV···rebound damping valve, R1···rebound chamber, R2···compression chamber

Claims

1. A cylinder; a rod member having a piston that is inserted into the cylinder so as to be axially movably and divides the inside of the cylinder into an expansion-side chamber and a compression-side chamber; an expansion-side damping passage provided in the rod member and communicating between the expansion-side chamber and the compression-side chamber; an extension-side damping valve that is provided on the rod member, has a valve body that opens and closes the extension-side damping passage, and provides resistance to a flow of liquid passing from the extension-side chamber toward the compression-side chamber; and an elastic body that urges the valve body in a direction to close the extension-side damping passage when the rod member moves a predetermined distance or more from a neutral position toward a stroke end on the contraction side relative to the cylinder. A shock absorber characterized by:

2. The extension-side damping passage is a port provided in the piston, The valve body is a leaf valve that is stacked on the piston and has an inner periphery fixed to the rod member.

2. The shock absorber according to claim 1 .

3. A cushion is attached to the rod member and compressed between the rod member and the cylinder when the rod member moves a predetermined distance or more from a neutral position toward a stroke end on the contraction side relative to the cylinder.

2. The shock absorber according to claim 1 .

4. The elastic body biases the outer periphery of the leaf valve toward the piston.

3. The shock absorber according to claim 2.

5. an annular guide member attached to the rod member and disposed on a compression side chamber side of the leaf valve; a plunger that is axially movably attached to an outer periphery of the guide member and faces the leaf valve; The elastic body is attached to the cylinder and biases the leaf valve via the plunger.

3. The shock absorber according to claim 2.

6. The elastic body has one end attached to the cylinder and the other end having an annular slider that is in sliding contact with the inner periphery of the cylinder and faces the leaf valve in the axial direction.

3. The shock absorber according to claim 2.

7. The elastic body is a coil spring having one end attached to the cylinder, The plunger has a cylindrical portion on a compression side chamber side that can be inserted into an inner periphery of the coil spring, The cylindrical portion has a tapered surface that is tapered toward the elastic body side end.

6. The shock absorber according to claim 5.

8. a holder for holding one end of the elastic body, The holder has a fixing member that is in close contact with the inner periphery of the cylinder and is fixed to the cylinder. A shock absorber according to any one of claims 1 to 7.

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