Shock absorber

Abstract

A shock absorber (D) comprises: a cylinder (1); a piston rod (2) movably inserted inside the cylinder (1) in the axial direction; a piston (3) that is connected to the piston rod (2), is movably inserted into the cylinder (1) in the axial direction, and partitions the inside of the cylinder (1) into an extension-side chamber (R1) and a pressure-side chamber (R2); a sub-cylinder (4) accommodated in the pressure-side chamber (R2) in the cylinder (1); and a partition wall (5) that partitions the inside of the sub-cylinder (4) into a hydraulic lock chamber (L) and a compensation chamber (R) on the anti-piston side (R) of the hydraulic lock chamber (L), wherein the compensation chamber (R) has an air chamber (G) and a liquid chamber (A) communicating with the pressure-side chamber (R2), and when the piston rod (2) moves in a contraction direction for contracting the pressure-side chamber (R2) relative to the cylinder (1) and the leading end of the piston rod (2) or a connecting member is inserted into the hydraulic lock chamber (L), the hydraulic lock chamber (L) suppresses movement of the piston rod (2) in the contraction direction by means of internal pressure.

Description

buffer

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

[0002] As disclosed in JP2020-008150A, for example, the shock absorber comprises 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 cylinder into an extension-side chamber and a compression-side chamber filled with hydraulic oil, a piston rod movably inserted into the cylinder and connected to the piston, and a free piston movably inserted into the cylinder in the axial direction and forming an air chamber within the cylinder opposite the compression-side chamber, and is interposed between the body and rear wheel of a saddle-type vehicle to generate a damping force that suppresses vibration of the vehicle body when the shock absorber is extended or retracted.

[0003] JP2020-008150A

[0004] In conventional shock absorbers, when the piston moves relative to the cylinder in a direction that compresses the compression-side chamber, a compression-side leaf valve that opens and closes the compression-side port provided in the piston opens, allowing hydraulic oil to move from the compression-side chamber to the extension-side chamber.This creates a difference in pressure between the compression-side chamber and the extension-side chamber, generating a compression-side damping force that suppresses the compression action.

[0005] Such conventional shock absorbers can generate a compression damping force and suppress vibrations of the vehicle body, but when the vehicle is forced to travel on rough roads in areas where road maintenance is not advanced, when the shock absorber contracts to near the end of its stroke, it may be necessary for the shock absorber to generate a greater compression damping force than before.

[0006] To meet such demands, it would be possible to increase the pressure in the compression side chamber when the shock absorber is contracting, but in conventional shock absorber structures, the air chamber faces the compression side chamber via a free piston, and the pressure in the compression side chamber cannot be increased above the pressure in the air chamber, so there is a limit to how much the compression side damping force can be increased.

[0007] Therefore, an object of the present invention is to provide a shock absorber that can generate a large damping force near the stroke end.

[0008] In order to solve the above problems, the shock absorber of the present invention comprises a cylinder, a piston rod that is inserted into the cylinder so as to be axially movable, a piston that is connected to the piston rod and inserted into the cylinder so as to be axially movable, and that divides the inside of the cylinder into an extension-side chamber and a compression-side chamber, a sub-cylinder that is housed in the compression-side chamber of the cylinder, and a partition that divides the inside of the sub-cylinder into a hydraulic lock chamber and a compensation chamber on the opposite side of the hydraulic lock chamber from the piston, the compensation chamber having an air chamber and a liquid chamber that is connected to the compression-side chamber, and when the piston rod moves in a contraction direction relative to the cylinder to compress the contraction-side chamber and the tip of the piston rod or a connecting member connected to the piston rod is inserted into the hydraulic lock chamber, the internal pressure suppresses movement of the piston rod in the contraction direction.

[0009] In a shock absorber configured in this manner, when the shock absorber contracts, the piston moves in the contraction direction, and the piston rod enters the hydraulic lock chamber, and the pressure in the hydraulic lock chamber creates a resistance force that suppresses the movement of the piston rod, which is added to the damping force during the contraction operation.

[0010] Fig. 1 is a cross-sectional view of a shock absorber according to an embodiment of the present invention, and Fig. 2 is a cross-sectional view of a shock absorber according to a first modified example of the embodiment of the present invention.

[0011] The present invention will be described based on an embodiment shown in the drawings. As shown in Fig. 1 , a shock absorber D in one embodiment includes a cylinder 1, a piston rod 2 inserted into the cylinder 1 so as to be axially movable, a piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be axially movable and dividing the interior of the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2, a sub-cylinder 4 housed in the compression-side chamber R2 of the cylinder 1, and a partition wall 5 dividing the interior of the sub-cylinder 4 into a hydraulic lock chamber L and a compensation chamber R on the opposite side of the hydraulic lock chamber L from the piston. Although not shown, the shock absorber D is, for example, interposed between the body and rear wheel of a saddle-type vehicle such as a motorcycle, and generates a damping force during extension / contraction to suppress vibration of the vehicle body. The shock absorber D may also be used in vehicles other than saddle-type vehicles, and may also be used in equipment, buildings, and the like other than vehicles.

[0012] Each component of the shock absorber D will now be described. The cylinder 1 is cylindrical, and its upper opening is closed by a cap 10 attached to its upper end in FIG. 1 . The cap 10 closes the upper opening of the cylinder 1 and includes a bracket 10a that enables connection to the body of a saddle-ride type vehicle. An annular rod guide 11, through which a piston rod 2 is inserted, is fitted to the inner periphery of the lower end of the cylinder 1 in FIG. 1 , and an annular bump stopper 12 is attached to the open end of the lower end of the cylinder 1 in FIG. 1 . The rod guide 11 is restricted from moving downward in FIG. 1 (outward from within the cylinder 1) by a snap ring 13 attached to the inner periphery of the cylinder 1. The pressure of the liquid in the cylinder 1 presses the rod guide 11 downward in FIG. 1 , positioning it in contact with the snap ring 13. In addition, a cylindrical bushing 14 that slides against the outer periphery of the piston rod 2 and a seal ring 15 that slides against the outer periphery of the piston rod 2 to seal the outer periphery of the piston rod 2 are attached to the inner periphery of the rod guide 11, and a seal ring 16 that fits tightly against the inner periphery of the cylinder 1 to seal between the cylinder 1 and the rod guide 11 is attached to the outer periphery of the rod guide 11.

[0013] An annular upper spring bearing 7 is screwed onto the outer periphery of the cylinder 1 at the top in Fig. 1. When the upper spring bearing 7 is rotated relative to the cylinder 1, it can be displaced in the vertical direction in Fig. 1, which is the axial direction relative to the cylinder 1.

[0014] The piston rod 2 is inserted into the cylinder 1 via the bump stopper 12 and the inner periphery of the rod guide 11 so as to be axially movable, and the piston 3, which is inserted into the cylinder 1 so as to be axially movable, is connected to the tip of the piston rod 2. The piston rod 2 has a small-diameter portion 2a, which is provided at the upper end in Fig. 1 (i.e., the tip), and the piston 3 is attached to its outer periphery, a threaded portion 2b provided on the outer periphery of the upper end of the small-diameter portion 2a, and a step portion 2c formed below the small-diameter portion 2a. A bracket 17 is attached to the lower end of the piston rod 2 in Fig. 1 so as to be connectable to a swing arm that supports the rear wheel of a saddle-ride type vehicle (not shown), and a bump cushion rubber 18, which is placed above the bracket 17, is fitted to the outer periphery of the lower end of the piston rod 2. The bump cushion rubber 18 faces the bump stopper 12 axially, which is attached to the lower end of the cylinder 1 in FIG. 1. When the shock absorber D strokes toward the contraction side near the stroke end, it comes into contact with the bump stopper 12 and is compressed, exerting a resilient force that suppresses further stroke of the shock absorber D in the contraction direction, thereby mitigating the impact when the shock absorber D is fully contracted.

[0015] The bracket 17 is provided with a lower spring bearing 17a on its outer periphery, and a suspension spring 8 made of a coil spring is interposed between the lower spring bearing 17a and an upper spring bearing 7 attached to the outer periphery of the cylinder 1. The suspension spring 8 biases the cylinder 1 and the piston rod 2 in the axial direction, i.e., in the direction that extends the shock absorber D, and exerts a resilient force that interposes the shock absorber D between the body and rear wheel of the saddle-ride type vehicle, thereby elastically supporting the vehicle body. Note that the installation position of the upper spring bearing 7 relative to the cylinder 1 can be changed in the axial direction, so that the initial load applied to the suspension spring 8 can be changed to adjust the vehicle height of the saddle-ride type vehicle.

[0016] An annular compression-side leaf valve 20, an annular piston 3, and an annular extension-side leaf valve 21 are assembled in this order to the small diameter portion 2a of the piston rod 2. The compression-side leaf valve 20, the piston 3, and the extension-side leaf valve 21 are sandwiched between a piston nut 22 that is screwed onto a threaded portion 2b at the tip of the small diameter portion 2a and a step portion 2c of the piston rod 2, and are fixed to the small diameter portion 2a of the piston rod 2.

[0017] The piston 3 is provided with a piston ring 3a on its outer periphery that slides against the inner periphery of the cylinder 1, and divides the inside of the cylinder 1 into an expansion-side chamber R1 and a compression-side chamber R2 that are filled with liquid. The piston 3 also has an expansion-side port 3b and a compression-side port 3c that communicate between the expansion-side chamber R1 and the compression-side chamber R2. The liquid filled in the expansion-side chamber R1 and the compression-side chamber R2 is, for example, hydraulic oil, but a liquid other than hydraulic oil can also be used.

[0018] The compression-side leaf valve 20 is a laminated leaf valve formed by laminating a plurality of annular plates, and is laminated at the lower end of the piston 3 in FIG. 1 with its inner periphery fixed to the piston rod 2 and its outer periphery allowed to bend. When laminated on the piston 3, the compression-side leaf valve 20 closes the compression-side port 3c, and when it is bent by receiving the pressure of the compression-side chamber R2 acting via the compression-side port 3c, it opens the compression-side port 3c.

[0019] On the other hand, the expansion-side leaf valve 21 is a laminated leaf valve formed by laminating a plurality of annular plates, and is laminated at the upper end of the piston 3 in FIG. 1 with its inner periphery fixed to the piston rod 2 and its outer periphery allowed to bend. When laminated on the piston 3, the expansion-side leaf valve 21 closes the expansion-side port 3b, and when it is bent by receiving the pressure of the expansion-side chamber R1 acting via the expansion-side port 3b, it opens the expansion-side port 3b.

[0020] Furthermore, a blocking body 6 is threadedly attached to the threaded portion 2b of the small-diameter portion 2a of the piston rod 2, on the sub-cylinder side, which is above the piston nut 22 in FIG. 1 . In this manner, the blocking body 6 is attached to the tip of the piston rod 2 as a connecting member. In this embodiment, the blocking body 6 is shaped like a hexagonal nut so that it can be gripped with a wrench (not shown), and has a threaded portion 6a on its inner periphery that threads onto the threaded portion 2b, and an annular flat surface 6b at its end on the sub-cylinder side, which is the upper end in FIG. 1 . Furthermore, a stopper 23 is attached to the outer periphery of the threaded portion 2b of the piston rod 2, on the side opposite the sub-cylinder of the blocking body 6, and abuts against the lower end of the blocking body 6 in FIG. 1 . The stopper 23 is a snap ring that fits into a groove (not shown) provided on the outer periphery of the small-diameter portion 2a of the piston rod 2. The stopper 23 abuts against the lower end of the blocking body 6 and restricts downward movement of the blocking body 6 in FIG. 1 , which is the side opposite the sub-cylinder, relative to the piston rod 2.

[0021] In addition, the tip of the small diameter portion 2a of the piston rod 2 is cylindrical, and the blocking body 6 is clamped between a flange portion 2d formed by crimping the tip and a stopper 23, so that the blocking body 6 is fixed immovably to the piston rod 2.

[0022] The sub-cylinder 4 is cylindrical and fitted onto the outer periphery of an annular ridge 10b provided at the lower end of the cap 10 in FIG. 1 and is fixed to the cap 10 by welding, and is housed in the compression-side chamber R2 within the cylinder 1. In this manner, the upper end of the sub-cylinder 4 is closed by the cap 10, and the outer diameter of the sub-cylinder 4 is smaller than the inner diameter of the cylinder 1, forming an annular gap S between the sub-cylinder 4 and the cylinder 1.

[0023] Furthermore, a disk-shaped partition wall 5 is attached to the inner periphery of the sub-cylinder 4, and the interior of the sub-cylinder 4 is partitioned by the partition wall 5 into a hydraulic lock chamber L and a compensation chamber R on the opposite piston side of the hydraulic lock chamber L. In this embodiment, the sub-cylinder 4 is formed of two cylinders 4a, 4b stacked in the axial direction, and the inner diameters of the opposing open ends of the cylinders 4a, 4b are made large enough to allow the partition wall 5 to fit into them. The cylinders 4a, 4b are stacked in the axial direction with the open ends of the cylinders 4a, 4b fitted into the partition wall 5, and the ends of the cylinders 4a, 4b are then welded from the outer periphery to the outer periphery of the partition wall 5, thereby manufacturing the sub-cylinder 4 integrally with the partition wall 5. By integrating the partition wall 5 with the sub-cylinder 4 in this way, the hydraulic lock chamber L and the compensation chamber R can be liquid-tightly separated without the need for a sealing member. The method for providing the partition wall 5 on the sub-cylinder 4 is just one example, and the partition wall 5 may be fixed to the sub-cylinder 4 by, for example, clamping the partition wall 5, which is fitted onto the inner periphery of the sub-cylinder 4, between a pair of snap rings attached to the inner periphery of the sub-cylinder 4. In this case, a seal ring that is in close contact with the inner periphery of the sub-cylinder 4 may be provided on the outer periphery of the partition wall 5 to seal the space between the hydraulic lock chamber L and the compensation chamber R.

[0024] Furthermore, a free piston 30 is inserted into the compensation chamber R at the inner periphery of the sub-cylinder 4, sliding against the inner periphery of the sub-cylinder 4 and movable in the axial direction, dividing the compensation chamber R into an air chamber G and a liquid chamber A. The free piston 30 is provided with a seal ring 30a on its outer periphery, sliding against the inside of the sub-cylinder 4, thereby sealing the gap between the air chamber G and the liquid chamber A. The air chamber G is filled with compressed gas, and the liquid chamber A is filled with the same liquid as the liquid filled in the expansion-side chamber R1 and the compression-side chamber R2. In the shock absorber D of this embodiment, the free piston 30 is used to divide the compensation chamber R into the air chamber G and the liquid chamber A, but an elastic partition such as a bladder, a diaphragm, or a bellows may also be used, which can change the volume distribution between the air chamber G and the liquid chamber A.

[0025] Furthermore, the sub-cylinder 4 is provided with an orifice 4c that penetrates the wall of the sub-cylinder 4 and communicates between the compression-side chamber R2 and the liquid chamber A. The orifice 4c provides resistance to the flow of liquid traveling between the compression-side chamber R2 and the liquid chamber A of the compensation chamber R. In this embodiment, the cross-sectional area of ​​the annular gap S between the sub-cylinder 4 and the cylinder 1 is made larger than the opening area of ​​the orifice 4c, so that the resistance that the annular gap S provides to the flow of liquid passing through the annular gap S is not greater than the resistance that the orifice 4c provides to the flow of liquid passing through the orifice 4c. In this embodiment, the orifice 4c provides resistance to the flow of liquid traveling between the compression-side chamber R2 and the liquid chamber A of the compensation chamber R. However, the flow path area of ​​the annular gap S may be reduced to provide resistance to the flow of liquid passing through the annular gap S and traveling between the compression-side chamber R2 and the liquid chamber A of the compensation chamber R, and the annular gap S may be used as a restricting flow path. In this case, instead of the orifice 4c, a hole that provides almost no resistance to the flow of liquid passing through may be provided in the sub-cylinder 4, and the liquid chamber A may be connected to the compression side chamber R2 via the annular gap S.

[0026] A lock piece 31 is inserted into the hydraulic lock chamber L within the sub-cylinder 4 so as to be axially movable, and a spring 32 is interposed between the lock piece 31 and the partition wall 5. The lock piece 31 has an annular head 31a with a hole 31b in the center, and a cylindrical portion 31c that rises upward in Figure 1 from the outer periphery of the head 31a and faces the inner periphery of the sub-cylinder 4, and faces a blocking body 6 attached to the tip of the piston rod 2 in the axial direction.

[0027] A snap ring 33 that prevents the lock piece 31 from coming out of the hydraulic lock chamber L is attached to the inner periphery of the sub-cylinder 4 near its lower end in FIG. 1 , and the lock piece 31 is biased by a spring 32 to a position where it abuts against the snap ring 33 when separated from the blocking body 6 of the piston rod 2. The spring 32 is a conical coil spring, and has a shorter overall length at maximum compression than a cylindrical coil spring. This ensures a sufficient stroke length for the lock piece 31 within the hydraulic lock chamber L, and also shortens the axial length of the hydraulic lock chamber L. This does not prevent the spring 32 from being a cylindrical coil spring. Furthermore, the spring 32 may be an elastic body other than a coil spring, such as a wave washer, a disc spring, rubber, or the like, as long as it can bias the lock piece 31.

[0028] The outer diameter of the cylindrical portion 31c of the lock piece 31 is slightly smaller than the inner diameter of the portion of the sub-cylinder 4 that forms the hydraulic lock chamber L, so that the liquid can pass through the gap between the outer periphery of the lock piece 31 and the inner periphery of the sub-cylinder 4 while encountering resistance.

[0029] The inner diameter of the hole 31b in the head 31a is smaller than the outer diameter of the annular flat surface 6b of the blocking body 6 and is set to a diameter that allows insertion of the flange portion 2d at the tip of the piston rod 2. Therefore, when the blocking body 6 and the lock piece 31 are not in contact with each other, the hydraulic lock chamber L and the compression side chamber R2 are communicated with each other via the hole 31b of the lock piece 31 and the gap between the outer periphery of the lock piece 31 and the inner periphery of the sub-cylinder 4, but when the piston rod 2 moves upward in Figure 1 relative to the cylinder 1 and the head 31a is in contact with the flat surface 6b of the blocking body 6, the hole 31b of the lock piece 31 is blocked by the flat surface 6b of the blocking body 6 and the piston rod 2, and the interior of the hydraulic lock chamber L and the compression side chamber R2 are communicated with each other only via the narrow gap between the outer periphery of the lock piece 31 and the inner periphery of the sub-cylinder 4.

[0030] 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 piston rod 2 moves downward in FIG. 1 relative to the cylinder 1 and the shock absorber D is extended, the liquid in the extension-side chamber R1, which is contracted by the piston 3, passes through the extension-side port 3b and moves to the compression-side chamber R2, which is expanded by pushing open the extension-side leaf valve 21. The extension-side leaf valve 21 provides resistance to this liquid flow, causing the pressure in the extension-side chamber R1 to rise, creating a difference in pressure between the extension-side chamber R1 and the compression-side chamber R2. As a result, the shock absorber D generates an extension-side damping force that impedes the extension operation. During the extension operation of the shock absorber D, the piston rod 2 retracts from the cylinder 1, causing a shortage of liquid in the compression-side chamber R2 by the volume of the piston rod 2 retracting from the cylinder 1. However, the free piston 30 is displaced in the sub-cylinder 4 in a direction that expands the air chamber G, and the shortage liquid is supplied from the liquid chamber A to the compression-side chamber R2.

[0031] 1 relative to the cylinder 1, causing the shock absorber D to contract. The liquid in the compression-side chamber R2, which is contracted by the piston 3, passes through the compression-side port 3c and pushes open the compression-side leaf valve 20, moving to the expansion-side chamber R1. The compression-side leaf valve 20 provides resistance to this liquid flow, causing the pressure in the compression-side chamber R2 to rise, creating a difference between the pressure in the compression-side chamber R2 and the pressure in the expansion-side chamber R1. This causes the shock absorber D to generate a compression-side damping force that impedes the contraction. When the shock absorber D contracts, the piston rod 2 enters the cylinder 1, causing excess liquid in the compression-side chamber R2 by the volume of the piston rod 2 entering the cylinder 1. However, the excess liquid flows into the liquid chamber A of the compensation chamber R through the orifice 4c, causing the free piston 30 to be displaced in the sub-cylinder 4 in a direction that contracts the air chamber G. Furthermore, the compensation chamber R is connected to the compression side chamber R2 and the liquid chamber A via the orifice 4c, and the pressure in the compression side chamber R2 can rise above the pressure in the liquid chamber A, so the shock absorber D can generate a larger compression side damping force than a conventional single-tube shock absorber.

[0032] As the shock absorber D contracts and the piston rod 2 moves upward in Figure 1 relative to the cylinder 1, the blocking body 6 attached to the tip of the piston rod 2 eventually comes into contact with the head 31a of the lock piece 31 in the hydraulic lock chamber L. When the flat surface 6b of the blocking body 6 comes into contact with the lock piece 31 in this way, the hole 31b of the lock piece 31 is blocked by the blocking body 6 and the piston rod 2, and communication between the hydraulic lock chamber L and the compression side chamber R2 through the hole 31b is cut off. When the piston rod 2 further moves upward in Figure 1 relative to the cylinder 1 from this state and the shock absorber D contracts, the lock piece 31 is pressed by the blocking body 6 and moves in a direction that compresses the hydraulic lock chamber L, and the blocking body 6 serving as a connecting member is inserted into the hydraulic lock chamber L. When the blocking body 6 is in contact with the head 31a of the lock piece 31, the hydraulic lock chamber L and the compression side chamber R2 are in communication only through the gap between the lock piece 31 and the sub-cylinder 4, so that when the piston rod 2 moves in the contracting direction relative to the cylinder 1, the piston rod 2 enters the hydraulic lock chamber L, and when the lock piece 31 is pushed by the blocking body 6 and contracts the hydraulic lock chamber L, the liquid in the hydraulic lock chamber L moves to the compression side chamber R2 while encountering resistance through the gap. Therefore, the pressure in the hydraulic lock chamber L rises to or exceeds the pressure in the compression side chamber R2, and the piston rod 2, together with the lock piece 31, is pressed downward in FIG. 1 by the action of the pressure in the hydraulic lock chamber L.

[0033] In this way, when the shock absorber D is displaced toward the contraction side near the stroke end, the blocking body 6 abuts against the lock piece 31, increasing the pressure in the hydraulic lock chamber L and thereby exerting the hydraulic lock function. Therefore, the shock absorber D can generate a greater compression side damping force by adding the resistance force caused by the increase in pressure in the hydraulic lock chamber L to the damping force generated by the compression side leaf valve 20.

[0034] When the shock absorber D contracts to near the stroke end and then starts to extend, the piston rod 2 withdraws from the hydraulic lock chamber L, and the lock piece 31 is biased by the spring 32 to return to its initial position in contact with the snap ring 33 before compressing the hydraulic lock chamber L.

[0035] As described above, the shock absorber D of this embodiment comprises the cylinder 1, the piston rod 2 inserted into the cylinder 1 so as to be axially movable, the piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be axially movable and dividing the interior of the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2, the sub-cylinder 4 housed in the compression-side chamber R2 of the cylinder 1, and the partition wall 5 dividing the interior of the sub-cylinder 4 into a hydraulic lock chamber L and a compensation chamber R on the opposite side of the hydraulic lock chamber L from the piston, the compensation chamber R having an air chamber G and a liquid chamber A connected to the compression-side chamber R2, and when the piston rod 2 moves in a contraction direction relative to the cylinder 1 so as to compress the contraction-side chamber R2 and the closing body 6 serving as a connecting member connected to the piston rod 2 is inserted into the hydraulic lock chamber L, the internal pressure suppresses movement of the piston rod 2 in the contraction direction.

[0036] In the shock absorber D of this embodiment configured as described above, when the shock absorber D exhibits a contraction operation, the piston 3 moves in the contraction direction, and the piston rod 2 enters the hydraulic lock chamber L, and a resistance force that suppresses the movement of the piston rod 2 due to the pressure in the hydraulic lock chamber L can be added to the damping force during the contraction operation. Therefore, according to the shock absorber D of this embodiment, when the shock absorber D contracts to near the stroke end, it is possible to generate a greater damping force than conventional shock absorbers. Furthermore, if the shock absorber D configured as described above is used by being interposed between the body and wheel of a saddle-ride type vehicle, it is possible to suppress so-called bottoming out, in which the shock absorber contracts to the stroke end when the saddle-ride type vehicle is traveling on rough roads.

[0037] Furthermore, since the shock absorber D of this embodiment can generate a large damping force when it contracts near the stroke end, it can absorb the impact at the time of maximum contraction without generating a large elastic force in the bump cushion rubber 18, and it also becomes possible to reduce the size and weight of the bump cushion rubber 18. Furthermore, since the shock absorber D of this embodiment can generate a large damping force when it contracts near the stroke end, it is not necessary to change the spring constant to compensate for the lack of damping force as the compression of the suspension spring 8 progresses, and therefore the structure of the suspension spring 8 can be simplified and productivity is improved.

[0038] Furthermore, the shock absorber D of this embodiment is equipped with a lock piece 31 having a hole 31b and inserted into the hydraulic lock chamber L within the sub-cylinder 4 so as to be axially movably, a spring 32 interposed between the lock piece 31 and the partition wall 5 to bias the lock piece 31 toward the piston, and a blocking body 6 provided at the tip of the piston rod 2 to block the hole 31b when it comes into contact with the lock piece 31, and the blocking body 6 is used as a connecting member.

[0039] With the shock absorber D configured in this manner, when the piston rod 2 approaches the sub-cylinder 4, the blocking body 6 provided on the piston rod 2 side blocks the hole 31b of the lock piece 31 that compresses the hydraulic lock chamber L, and the hydraulic lock chamber L can be compressed by the piston rod 2, the blocking body 6, and the lock piece 31. Therefore, even if there is a misalignment between the axes of the piston rod 2 and the sub-cylinder 4, the hydraulic lock chamber L can be compressed to increase the pressure within the hydraulic lock chamber L, and the desired large compression-side damping force can be obtained near the stroke end.

[0040] If there is no problem with axial misalignment between the piston rod 2 and the sub-cylinder 4, the lock piece 31, spring 32, and snap ring 33 housed in the sub-cylinder 4 may be eliminated, and an annular lock piece may be provided on the outer periphery of the piston rod 2 as a connecting member. When the piston rod 2 enters the sub-cylinder 4 together with the lock piece, the hydraulic lock chamber L is compressed by the lock piece provided on the piston rod 2, increasing the internal pressure and suppressing movement of the piston rod 2 in the contracting direction.

[0041] In the shock absorber D of this embodiment, a blocking body 6 is provided as a connecting member connected to the piston rod 2, and the hydraulic lock chamber L restricts movement of the piston rod 2 in the contraction direction when the blocking body 6 is inserted into the hydraulic lock chamber L. However, a connecting member may not be provided and the hydraulic lock chamber L may restrict movement of the piston rod 2 in the contraction direction when the tip of the piston rod 2 is inserted into the hydraulic lock chamber L. In this case, for example, when the tip surface of the piston rod 2 abuts against the lock piece 31, the tip surface may close the hole 31b. Furthermore, if no connecting member is provided and the lock piece 31, spring 32, and snap ring 33 are eliminated, the inner diameter of the tube 4a of the sub-cylinder 4 that forms the hydraulic lock chamber L may be made slightly larger than the outer diameter of the tip of the piston rod 2. When the tip of the piston rod 2 is inserted into the hydraulic lock chamber L, the pressure in the hydraulic lock chamber L increases, restricting movement of the piston rod 2 in the contraction direction. In this way, the shock absorber D may generate a hydraulic locking function by attaching some kind of connecting member to the tip of the piston rod 2 and inserting the connecting member into the hydraulic lock chamber L, or may generate a hydraulic locking function by inserting the tip of the piston rod 2 itself into the hydraulic lock chamber L.

[0042] Furthermore, in the shock absorber D of this embodiment, when the hydraulic lock chamber L is compressed, the liquid flowing from the hydraulic lock chamber L to the pressure-side chamber R2 passes through the gap between the lock piece 31 and the sub-cylinder 4, and this gap applies resistance to the flow of the liquid, thereby increasing the pressure in the hydraulic lock chamber L. However, instead of having the lock piece 31 slide against the inner periphery of the sub-cylinder 4 and forming a passage functioning as an orifice or choke in the lock piece 31, the blocking body 6, or between the lock piece and the blocking body 6, or the piston rod 2, the pressure in the hydraulic lock chamber L can be increased by having the liquid pass through this passage. Furthermore, the sub-cylinder 4 may be provided with an orifice or choke that connects the hydraulic lock chamber L and the pressure-side chamber R2. Furthermore, although the blocking body 6 is hexagonal, the shape and structure of the blocking body 6 can be appropriately modified as long as it closes the hole 31b of the lock piece 31 when it abuts against the lock piece 31 and can compress the hydraulic lock chamber L together with the lock piece 31 when the piston rod 2 enters the hydraulic lock chamber L. Incidentally, even when a groove is provided on one or both of the contact surfaces of the blocking body 6 or the lock piece 31 and the groove functions as an orifice or choke for increasing the pressure in the hydraulic lock chamber L, the hole 31b is not completely blocked when the blocking body 6 is in contact with the lock piece 31. However, even in such a case, the blocking body 6 is still included in the concept of blocking the hole 31b as long as the function of the hydraulic lock chamber L can be realized.

[0043] The lock piece 31 may be made of metal, but if it is made of resin, the impact sound when it comes into contact with the blocking body 6 can be reduced and damage to the inner surface of the sub-cylinder 4 can be suppressed when it moves within the sub-cylinder 4.

[0044] Furthermore, in the shock absorber D of this embodiment, the sub-cylinder 4 is provided with an orifice 4c on the side that connects the compression-side chamber R2 to the fluid chamber A, so that the pressure in the compression-side chamber R2 can be made higher than the pressure in the compensation chamber R when the shock absorber D is contracting, thereby making it possible to increase the compression-side damping force when the shock absorber D is contracting. Therefore, if the shock absorber D configured in this manner is used by being interposed between the body and wheel of a saddle-ride type vehicle, bottoming out can be further suppressed when the saddle-ride type vehicle is traveling on rough roads.

[0045]

[0023] Furthermore, in the shock absorber D of this embodiment, the blocking body 6 is attached to the outer periphery of the tip of the piston rod 2, the piston 3 is annular and attached to the outer periphery of the piston rod 2 on the side opposite to the sub-cylinder from the blocking body 6, and has an expansion-side port 3b and a compression-side port 3c that communicate between the expansion-side chamber R1 and the compression-side chamber R2, a compression-side leaf valve 20 that is annular and has an inner periphery fixed to the outer periphery of the piston rod 2 and overlapped with the expansion-side chamber end of the piston 3 to open and close the compression-side port 3c, an expansion-side leaf valve 21 that is annular and has an inner periphery fixed to the outer periphery of the piston rod 2 and overlapped with the compression-side chamber end of the piston 3 to open and close the expansion-side port 3b, and a stopper 23 that is attached to the outer periphery of the piston rod 2 and abuts against the side opposite to the sub-cylinder of the blocking body 6. In the shock absorber D configured in this manner, when the shock absorber D contracts to the vicinity of the stroke end, the blocking body 6 provided on the piston rod 2 abuts against the lock piece 31 and compresses the hydraulic lock chamber L together with the lock piece 31, thereby increasing the pressure in the hydraulic lock chamber L. The pressure in the hydraulic lock chamber L presses the obstruction body 6 against the piston rod 2 toward the piston 3, but the movement of the obstruction body 6 toward the piston 3 is restricted by the stopper 23 attached to the piston rod 2, so that the axial load that the obstruction body 6 receives due to the pressure in the hydraulic lock chamber L does not act on the compression-side leaf valve 20, the piston 3, or the extension-side leaf valve 21. Therefore, according to the shock absorber D of this embodiment configured as described above, even if the obstruction body 6 is provided on the piston rod 2, the axial load that the obstruction body 6 receives due to the pressure in the hydraulic lock chamber L does not act on the compression-side leaf valve 20, the piston 3, or the extension-side leaf valve 21. Therefore, it is possible to prevent deterioration of the compression-side leaf valve 20, the piston 3, and the extension-side leaf valve 21, and it is possible to generate the extension-side and compression-side damping forces as designed.

[0046] The vertical arrangement of the air chamber G and the liquid chamber A in the compensation chamber R may be reversed from that shown in FIG. 1 . In addition, in the shock absorber D of this embodiment, the sub-cylinder 4 is provided with an orifice 4c that connects the liquid chamber A and the compression-side chamber R2 to assist the pressure increase in the compression-side chamber R2 during contraction. However, a hole that does not function as an orifice may be provided that connects the liquid chamber A and the compression-side chamber R2 and provides a restrictive flow path that provides resistance to the flow of liquid in the gap between the cylinder 1 and the sub-cylinder 4 to assist the pressure increase in the compression-side chamber R2 during contraction. However, when the orifice 4c, whose area is easy to manage, is used to assist the pressure increase in the compression-side chamber R2 during contraction, it is possible to enjoy the advantage of easier adjustment of the pressure in the compression-side chamber R2 and the pressure in the liquid chamber A. Furthermore, although the diameter of the sub-cylinder 4 on the hydraulic lock chamber L side and the diameter on the compensation chamber R side are shown to be equal, they may be different. Furthermore, in the shock absorber D of this embodiment, the sub-cylinder 4 is held by the cap 10, so that the components to be assembled to the sub-cylinder 4 can be assembled to the cap 10 together with the sub-cylinder 4 to form a sub-cylinder assembly, facilitating the assembly of the shock absorber D. However, the structure for housing and fixing the sub-cylinder 4 within the cylinder 1 is not limited to that shown in Figure 1 and can be modified in design as appropriate.

[0047] For example, like the shock absorber D1 in the first modified example of one embodiment shown in Figure 2, the sub-cylinder 4 may be formed by a first cylinder 41 that is a cylindrical bottomed cylinder and has a bottom 41a as a partition wall to form the hydraulic lock chamber L, and a second cylinder 42 that is fitted onto the outer periphery of the bottom end of the first cylinder 41 and is crimped from the outer periphery to hold the first cylinder 41 and form the compensation chamber R.

[0048] The first cylinder 41 has a disk-shaped bottom 41a and a cylindrical portion 41b whose outer diameter is smaller than that of the bottom 41a and which hangs down from the bottom 41a toward the piston. The first cylinder 41 is accommodated in the compression-side chamber R2 within the cylinder 1 and defines a hydraulic lock chamber L therein. A lock piece 31 is inserted into the first cylinder 41 so as to be movable in the axial direction, and a conical coil spring 32 is interposed between the lock piece 31 and the bottom 41a. The lower end of the cylindrical portion 41b in FIG. 2 is bent toward the inner periphery, forming a bent portion 41c at the lower end of the cylindrical portion 41b. The bent portion 41c prevents the lock piece 31 from coming out of the hydraulic lock chamber L. When the lock piece 31 is separated from the blocking body 6 of the piston rod 2, the lock piece 31 is biased by the spring 32 to be positioned in contact with the bent portion 41c.

[0049] The second tube 42 is cylindrical and fitted onto the outer periphery of an annular ridge 10b provided at the lower end of the cap 10 in FIG. 2 and fixed to the cap 10 by welding. It is housed in the compression-side chamber R2 within the cylinder 1, forming a compensation chamber R therein. The inner diameter of the lower end of the second tube 42 in FIG. 2 is larger than that of the upper end, and the second tube 42 has a step 42a on the inner periphery and an orifice 42b that radially penetrates the wall on the side opposite the piston from the step 42a. The inner diameter of the lower end of the second tube 42 is set to a diameter that allows the bottom 41a of the first tube 41 to be inserted therein. The axial length of the larger-diameter portion 42c of the second tube 42 is longer than the axial length of the bottom 41a of the first tube 41.

[0050] To connect the first tube 41 and the second tube 42 configured in this manner, the bottom end of the first tube 41 is inserted into the inside of the lower end of the second tube 42, and the bottom 41 a of the first tube 41 is brought into contact with the stepped portion 42 a of the second tube 42. In this state, the portion 42 c with a larger inner diameter at the lower end of the second tube 42 is used as a crimping portion and crimped from the outer periphery to plastically deform the bottom 41 a so as to grip it, thereby connecting the second tube 42 and the first tube 41. In this way, when the sub-cylinder 4 is formed by the first cylinder 41, which is a cylindrical bottomed cylinder that forms the hydraulic lock chamber L, and the second cylinder 42, which is fitted onto the outer periphery of the bottom end of the first cylinder 41 and is crimped from the outer periphery to hold the first cylinder 41 in place and form the compensation chamber R, no distortion occurs in the first cylinder 41 and the second cylinder 42 due to welding, and post-processing of the inner surfaces of the first cylinder 41 and the second cylinder 42 is not required, so the sub-cylinder 4 can be manufactured cheaply and easily. In addition, because the hydraulic lock chamber L is formed by the first cylinder 41, there is no need to worry about liquid leaking from inside the hydraulic lock chamber L into the compression-side chamber R2 through any gap other than between the cylindrical portion 41 b and the lock piece 31 when the hydraulic lock function is performed, and the hydraulic lock function can be performed stably.

[0051] Furthermore, even if the liquid in the compensation chamber R leaks into the pressure side chamber R2 from between the lower end portion 42d, which is the crimped portion of the first tube 41 and the second tube 42, the joint between the first tube 41 and the second tube 42 is only faced by the liquid chamber A, and the liquid chamber A and the pressure side chamber R2 are always in communication, so no problem occurs, and since the hydraulic lock chamber L is formed within the bottomed cylindrical first tube 41, there is no effect on the hydraulic lock chamber L.

[0052] In addition, the second tube 42 may hold the first tube 41 by fitting the second tube 42 to the outer periphery of the first tube 41, as long as the holding state can be maintained by fitting the second tube 42 to the outer periphery of the first tube 41.

[0053] It is also possible to form the sub-cylinder 4 by connecting the first and second cylinders together, with the first cylinder forming the hydraulic lock chamber L being cylindrical and the second cylinder connected to the cap 10 to form the compensation chamber R being a cylinder with a bottom, and fitting the first cylinder onto the outer periphery of the bottom end of the second cylinder and crimping the first cylinder from the outer periphery toward the bottom of the second cylinder.

[0054] Although the preferred embodiment of the present invention has been described in detail, modifications, variations and changes can be made thereto without departing from the scope of the appended claims.

[0055] DESCRIPTION OF SYMBOLS 1: Cylinder, 2: Piston rod, 3: Piston, 3b: Extension side port, 3c: Compression side port, 4: Sub-cylinder, 4c: Orifice, 5: Partition wall, 6: Blocking body (connecting member), 20: Compression side leaf valve, 21: Extension side leaf valve, 23: Stopper, 31: Lock piece, 31b: Hole, 32: Spring, 41: First cylinder, 41a: Bottom, 42: Second cylinder, A: Fluid chamber, D: Shock absorber, G: Air chamber, L: Hydraulic lock chamber, R: Compensation chamber, R1: Extension side chamber, R2: Compression side chamber, S: Annular gap

Claims

1. A shock absorber comprising: a cylinder; a piston rod inserted into the cylinder so as to be axially movably; a piston connected to the piston rod and inserted into the cylinder so as to be axially movably, dividing the interior of the cylinder into an extension-side chamber and a compression-side chamber; a sub-cylinder contained in the compression-side chamber of the cylinder; and a partition wall dividing the interior of the sub-cylinder into a hydraulic lock chamber and a compensation chamber on an opposite piston side of the hydraulic lock chamber, wherein the compensation chamber has an air chamber and a liquid chamber connected to the compression-side chamber, and when the piston rod moves relative to the cylinder in a contraction direction compressing the compression-side chamber and the tip of the piston rod or a connecting member connected to the piston rod is inserted into the hydraulic lock chamber, internal pressure suppresses movement of the piston rod in the contraction direction.

2. A shock absorber as claimed in claim 1, comprising: a lock piece having a hole and inserted within said sub-cylinder so as to be axially movably into said hydraulic lock chamber; a spring interposed between said lock piece and said partition wall for biasing said lock piece towards the piston; and a blocking body provided at the tip of said piston rod for blocking said hole when it comes into contact with said lock piece, said connecting member being said blocking body.

3. A shock absorber according to claim 1, wherein the sub-cylinder has an orifice on the side thereof that connects the pressure side chamber to the liquid chamber.

4. A shock absorber as claimed in claim 1, wherein a restricting flow passage is formed in the annular gap between said cylinder and said sub-cylinder to provide resistance to the flow of liquid passing between said compression side chamber and said compensation chamber.

5. A shock absorber as claimed in claim 1, wherein the sub-cylinder comprises a first cylinder having a bottom and a bottom that serves as the partition to form a hydraulic lock chamber, and a second cylinder that is fitted onto the outer periphery of the bottom end of the first cylinder and holds the first cylinder to form a compensation chamber.

6. A shock absorber as claimed in claim 2, wherein the obstruction body is attached to the outer periphery of the tip of the piston rod, the piston is annular and attached to the outer periphery of the piston rod on the side opposite the sub-cylinder from the obstruction body, and has an extension-side port and a compression-side port communicating the extension-side chamber and the compression-side chamber, a compression-side leaf valve which is annular and has an inner periphery fixed to the outer periphery of the piston rod and is placed on the extension-side chamber side end of the piston for opening and closing the compression-side port, an extension-side leaf valve which is annular and has an inner periphery fixed to the outer periphery of the piston rod and is placed on the compression-side chamber side end of the piston for opening and closing the extension-side port, and a stopper which is attached to the outer periphery of the piston rod and abuts on the side opposite the sub-cylinder from the obstruction body.

7. A shock absorber according to claim 2, wherein the spring is a conical coil spring.

Images