SHOCK ABSORBER

A shock absorber according to the present invention includes: a cylinder, a rod movably inserted into the cylinder, and a partition member having a disk shape and inserted into the cylinder to partition an inside of the cylinder into two working chambers, in which the partition member includes a plurality of ports that communicates the working chambers with each other, and a choke passage having a portion communicating the working chambers with each other and passing through an inner peripheral side or an outer peripheral side of each port along a circumferential direction.

TECHNICAL FIELD

The present invention relates to a shock absorber.

BACKGROUND ART

Some shock absorbers include, for example, a cylinder, a piston rod movably inserted into the cylinder, a piston slidably inserted into the cylinder and coupled to the piston rod, an extension side chamber and a compression side chamber that are defined in the cylinder by the piston and filled with hydraulic fluid, an extension side port and a compression side port that are provided in the piston and communicate the extension side chamber and the compression side chamber, an extension side leaf valve having an annular shape that is stacked on a compression side chamber side end of the piston, has an inner periphery fixed to the piston rod and an outer periphery allowed to bend, and opens and closes the extension side port, a compression side leaf valve having an annular shape that is stacked on an extension side chamber side end of the piston, has an inner periphery fixed to the piston rod and an outer periphery allowed to bend, and opens and closes the compression side port, and a choke passage that is provided in the piston and communicates the extension side chamber and the compression side chamber.

When the shock absorber configured as described above performs an extension and contraction operation at a low speed, the extension side leaf valve or the compression side leaf valve does not open, so that the hydraulic fluid flows back and forth between the extension side chamber and the compression side chamber through the choke passage. Therefore, as disclosed, for example, in JP 2007-132389 A, the conventional shock absorber exerts a damping force depending on a pressure loss when the hydraulic fluid passes only through the choke passage when performing an extension and contraction operation at a low speed. The characteristic of the damping force generated by the shock absorber with respect to the extension and contraction speed when the hydraulic fluid passes only through the choke passage (damping force characteristic) is a characteristic in which the damping force increases substantially in proportion to the extension and contraction speed, which is called a choke characteristic. Therefore, when the choke passage is provided in the piston as described above, the damping force is relatively easily set as compared with an orifice in which the damping force of the shock absorber has a characteristic proportional to the square of the extension speed.

CITATION LIST

Patent Literature

Patent Literature 1: JP 2007-132389 A

SUMMARY OF INVENTION

Technical Problem

Here, as the passage length of the choke passage increases, the resistance applied to the flow of the hydraulic fluid increases, and the damping force of the shock absorber can be increased. As described above, in the conventional shock absorber, when the choke passage is provided in the piston instead of the orifice, it is sufficient if the length of the choke passage is set according to the required damping force characteristic.

However, in the conventional shock absorber, when the choke passage is provided in the piston, it is provided to penetrate from an extension side chamber end to a compression side chamber end of the piston in an axial direction, and the length of the choke passage cannot be set to be equal to or longer than the length of the piston in the axial direction. In addition, since a stroke length of the shock absorber is sacrificed when the axial length of the piston is increased, there is a limit to increase the axial length of the piston.

As described above, the use of the orifice makes it difficult to set the damping force characteristic and thus it is desired to use the choke passage, but in the conventional shock absorber, since a long choke passage cannot be provided, there is a problem that the damping force when extending and contracting at a low speed cannot be set high.

Thus, an object of the present invention is to provide a shock absorber that can increase the damping force when extending and contracting at a low speed and enables easy setting of the damping force characteristic.

In order to solve the above problems, a shock absorber according to the present invention includes a cylinder, a rod movably inserted into the cylinder, and a partition member having a disk shape and inserted into the cylinder to define two working chambers in the cylinder, in which the partition member includes a port communicating the two working chambers, and a choke passage having a portion communicating the two working chambers and passing through an inner peripheral side or an outer peripheral side of the port of the partition member along a circumferential direction. In the shock absorber configured as described above, since the choke passage includes a portion provided along the circumferential direction in a dead space on the inner peripheral side or the outer peripheral side of the port of the partition member having a disk shape, the passage length of the choke passage can be increased without increasing the axial length of the partition member. Since the passage length of the choke passage can be increased, the degree of freedom in designing the passage length of the choke passage is improved, and a choke passage having a sufficient length can be formed in the partition member.

DESCRIPTION OF EMBODIMENTS

First Embodiment

Hereinafter, the present invention will be described on the basis of embodiments illustrated in the drawings. As illustrated inFIG.1, a shock absorber D according to the first embodiment includes a cylinder1, a rod2movably inserted into the cylinder1, and a piston3, which is a partition member, that is inserted into the cylinder1and defines an extension side chamber R1and a compression side chamber R2as two working chambers in the cylinder1. Further, in the case of the shock absorber D, for example, it is used by being interposed between a vehicle body and an axle of a vehicle, which is not illustrated, to suppress vibrations of the vehicle body and the wheels.

Each part of the shock absorber D will be described in detail below. As illustrated inFIG.1, a rod guide10having an annular shape is mounted on an upper end of the cylinder1, and a lower end of the cylinder1is closed by a cap11. Further, in the cylinder1, the rod2on which the piston3is mounted at a distal end is movably inserted.

The rod2is slidably inserted into the rod guide and inserted into the cylinder1, and movement in the axial direction is guided by the rod guide10. In addition, the inside of the cylinder1is partitioned by the piston3into the extension side chamber R1and the compression side chamber R2that are filled with fluid such as hydraulic fluid. Note that a liquid other than the hydraulic fluid such as water and an aqueous solution may also be used as the fluid. In addition, the fluid may be a gas instead of a liquid.

Note that a gas chamber G is defined inside the cylinder1below the compression side chamber R2by a free piston6slidably inserted into the cylinder1. Further, when the rod2is displaced in the axial direction with respect to the cylinder1, the gas chamber G is expanded or contracted by the free piston6being displaced in the axial direction with respect to the cylinder1according to the volume of the rod2entering and leaving the cylinder1, and the volume of the rod2entering and leaving the cylinder1is compensated by a change in the volume of the gas chamber G. In this manner, the shock absorber D is a so-called single cylinder type shock absorber, but may be configured as a double cylinder type shock absorber including a reservoir outside the cylinder1.

Returning to this, the rod2includes a screw portion2bprovided on the outer periphery of a distal end portion2a, which is a lower end inFIG.1, and a C-ring2cattached to the outer periphery above the distal end portion2a. An extension side leaf valve7and a compression side leaf valve8formed in an annular shape are attached to the outer periphery of the distal end portion2aof the rod2together with the piston3having an annular shape. The leaf valves7and8and the piston3are sandwiched between a piston nut9screwed to the screw portion2band the C-ring2cand fixed to the outer periphery of the distal end portion2aof the rod2.

As illustrated inFIGS.2to4, the piston3has a disk shape, and includes an insertion hole3athrough which the distal end portion2aof the rod2is inserted at the center, and extension side ports3band compression side ports3cthat are provided on the same circumference and have an arc shape as viewed in the axial direction. In addition, three extension side ports3band three compression side ports3care alternately arranged on the same circumference in the piston3, and serve as ports in the piston3, which is a partition member.

In addition, the piston3includes a valve seat3dhaving a petal shape surrounding each extension side port3bat an end portion facing the compression side chamber R2side as illustrated inFIG.4, and a valve seat3ehaving a petal shape surrounding each compression side port3cat an end portion facing the extension side chamber R1side as illustrated inFIG.2. As described above, the extension side ports3bprovided in the piston3of the shock absorber D of the first embodiment are independent opening ports that do not communicate with each other, and the compression side ports3care also independent opening ports that do not communicate with each other.

Further, as illustrated inFIGS.2to4, the piston3includes a choke passage T1having a spiral shape disposed on the outer peripheral side of the extension side ports3band the compression side ports3cof the piston3and surrounding the extension side ports3band the compression side ports3c. That is, the choke passage T1is formed in a spiral shape and is formed to include a spiral portion passing through the outer peripheral side of the extension side ports3band the compression side ports3c, which are the ports of the piston3, along the circumferential direction. More in detail, the choke passage T1has a spiral shape and opens from the outer peripheral side of the valve seat3eat the extension side chamber R1side end of the piston3to the outer peripheral side of the valve seat3dat the compression side chamber R2side end of the piston3and communicates the extension side chamber R1and the compression side chamber R2.

Note that, although not illustrated, the choke passage T1may include a spiral portion disposed on the outer peripheral side of the extension side ports3band the compression side ports3cof the piston3, a portion that opens in the axial direction from the outer peripheral side of the valve seat3eat the extension side chamber R1side end of the piston3and is connected to the spiral portion, and a portion that opens in the axial direction from the outer peripheral side of the valve seat3dat the compression side chamber R2side end of the piston3and is connected to the spiral portion. In addition, the choke passage T1having a spiral shape may be disposed on the inner peripheral side of the extension side ports3band the compression side port3cof the piston3as in pistons3of the first modification illustrated inFIG.5and the second modification illustrated inFIG.6. When the choke passage T1is disposed on the inner peripheral side of the extension side ports3band the compression side port3cof the piston3, as illustrated inFIG.5, it is sufficient if a spiral portion T1aof the choke passage T1is provided such that portions T1band T1cthat communicate respectively with the extension side chamber R1side end and the compression side chamber R2side end of the piston3are provided between the extension side ports3band the compression side ports3cof the piston3. In addition, when the choke passage T1is disposed on the inner peripheral side of the extension side ports3band the compression side ports3cof the piston3, as illustrated inFIG.6, one end and an other end of the choke passage T1may be opened to the insertion hole3a, and the rod2may be provided with a passage2din which one opening communicates with the extension side chamber R1and a passage2ein which the other opening communicates with the compression side chamber R2.

Note that the piston3configured as described above can be manufactured using a 3D printer. When the 3D printer is used, the choke passage T1having a complicated structure can be easily formed in the piston3together with the extension side ports3band the compression side ports3c.

The extension side leaf valve7is a stack leaf valve in which a plurality of annular plates is stacked, and is stacked on a lower surface of the piston3facing the compression side chamber R2inFIG.1. The inner periphery of the extension side leaf valve7is sandwiched and fixed between the piston nut9and the C-ring2c, bending of the outer peripheral side, which is a free end, is allowed, and the extension side leaf valve7is seated and unseated with respect to the valve seat3dto open and close outlet ends of the extension side ports3b. As described above, when the extension side leaf valve7is placed on the piston3, sandwiched between the piston nut9and the C-ring2cof the rod2, and fixed to the rod2, the extension side leaf valve7abuts on the valve seat3dand is stacked on the piston3. Further, in a state where the outer periphery is seated on the valve seat3d, the extension side leaf valve7closes the extension side ports3band disconnects communication between the extension side chamber R1and the compression side chamber R2via the extension side ports3b. In addition, when the extension side leaf valve7is bent by receiving a pressure of the extension side chamber R1through the extension side ports3band unseated from the valve seat3d, the extension side ports3bare opened, the extension side chamber R1and the compression side chamber R2communicate with each other, and resistance is applied to the flow of the hydraulic fluid from the extension side chamber R1to the compression side chamber R2.

In addition, the compression side leaf valve8is a stack leaf valve in which a plurality of annular plates is stacked, and is stacked on an upper surface of the piston3facing the extension side chamber R1inFIG.1. The inner periphery of the compression side leaf valve8is sandwiched and fixed between the piston nut9and the C-ring2c, bending of the outer peripheral side, which is a free end, is allowed, and the compression side leaf valve8is seated and unseated with respect to the valve seat3eto open and outlet ends of the compression side ports3c. As described above, when the compression side leaf valve8is placed on the piston3, sandwiched between the piston nut9and the C-ring2cof the rod2, and fixed to the rod2, the compression side leaf valve8abuts on the valve seat3eand is stacked on the piston3. Further, in a state where the outer periphery is seated on the valve seat3e, the compression side leaf valve8closes the compression side ports3cand disconnects communication between the compression side chamber R2and the extension side chamber R1via the compression side ports3c. In addition, when the compression side leaf valve8is bent by receiving a pressure of the compression side chamber R2through the compression side ports3cand unseated from the valve seat3e, the compression side ports3care opened, the compression side chamber R2and the extension side chamber R1communicate with each other, and resistance is applied to the flow of the hydraulic fluid from the compression side chamber R2to the extension side chamber R1.

The shock absorber D is configured as described above, and the operation of the shock absorber D will be described hereinafter. First, an operation when the rod2moves upward inFIG.1with respect to the cylinder1and the shock absorber D performs an extension operation will be described. When the shock absorber D performs the extension operation, the piston3moves upward inFIG.1with respect to the cylinder1, and thus, the extension side chamber R1is compressed and the compression side chamber R2is enlarged.

Then, the pressure in the extension side chamber R1increases. This pressure acts on the extension side leaf valve7through the extension side ports3bthat are not closed by the leaf valve8stacked on the upper end of the piston3inFIG.1. When the extension speed of the shock absorber D is low and the pressure in the extension side chamber R1does not reach the valve opening pressure of the leaf valve7, the hydraulic fluid moves from the extension side chamber R1to the compression side chamber R2only through the choke passage T1. Therefore, when the extension speed is low, the choke passage T1applies resistance to the hydraulic fluid passing therethrough and the shock absorber D generates a damping force. In addition, when the extension speed of the shock absorber D exceeds the low speed and reaches the high speed range, the leaf valve7bends and is unseated from the valve seat3dto open the extension side ports3b, so that the hydraulic fluid in the extension side chamber R1passes through the extension side ports3band the choke passage T1and moves to the compression side chamber R2. When the flow rate increases, the choke passage T1applies a larger resistance to the flow of the hydraulic fluid than the leaf valve7does. Therefore, when the extension speed of the shock absorber D becomes high, the hydraulic fluid is less likely to pass through the choke passage T1, so that the hydraulic fluid preferentially passes through the extension side ports3b. Therefore, when the extension speed exceeds the low speed and reaches the high speed range, the shock absorber D generates a damping force substantially by the resistance applied to the flow of the hydraulic fluid by the leaf valve7. Note that at the time of extension of the shock absorber D, since the rod2is retracted from the inside of the cylinder1, the free piston6moves upward inFIG.1with respect to the cylinder1, the volume of the gas chamber G is enlarged by the volume of the rod2retracted from the inside of the cylinder1, and the volume of the rod2retracted from the inside of the cylinder1is compensated.

Next, an operation when the rod2moves downward inFIG.1with respect to the cylinder1and the shock absorber D performs a contraction operation will be described. When the shock absorber D performs the contraction operation, the piston3moves downward inFIG.1with respect to the cylinder1, and thus, the compression side chamber R2is compressed, and the extension side chamber R1is enlarged.

Then, the pressure in the compression side chamber R2increases. This pressure acts on the compression side leaf valve8through the compression side ports3cthat are not closed by the leaf valve7stacked on the lower end of the piston3inFIG.1. When the contraction speed of the shock absorber D is low and the pressure in the compression side chamber R2does not reach the valve opening pressure of the leaf valve8, the hydraulic fluid moves from the compression side chamber R2to the extension side chamber R1only through the choke passage T1. Therefore, when the contraction speed is low, the choke passage T1applies resistance to the hydraulic fluid passing therethrough and the shock absorber D generates a damping force. In addition, when the contraction speed of the shock absorber D exceeds the low speed and reaches the high speed range, the leaf valve8bends and is unseated from the valve seat3eto open the compression side ports3c, so that the hydraulic fluid in the compression side chamber R2passes through the compression side ports3cand the choke passage T1and moves to the extension side chamber R1. When the flow rate increases, the choke passage T1applies a larger resistance to the flow of the hydraulic fluid than the leaf valve8does. Therefore, when the contraction speed of the shock absorber D becomes high, the hydraulic fluid is less likely to pass through the choke passage T1, so that the hydraulic fluid preferentially passes through the compression side ports3c. Therefore, when the contraction speed exceeds the low speed and reaches the high speed range, the shock absorber D generates a damping force substantially by the resistance applied to the flow of the hydraulic fluid by the leaf valve8. Note that at the time of contraction of the shock absorber D, since the rod2enters the inside of the cylinder1, the free piston6moves downward inFIG.1with respect to the cylinder1, the volume of the gas chamber G is reduced by the volume of the rod2entering the inside of the cylinder1, and the volume of the rod2entering the inside of the cylinder1is compensated.

As described above, when the extension and contraction speed of the shock absorber D is low, the shock absorber D generates a damping force with the choke passage T1, and when the extension and contraction speed of the shock absorber D is high, the shock absorber D generates a damping force with the leaf valves7and8. Therefore, the damping force characteristic of the shock absorber D of the first embodiment is a characteristic that becomes the choke characteristic substantially proportional to the extension and contraction speed when the extension and contraction speed of the shock absorber D is low and changes to the valve characteristic of the leaf valves7and8when the extension and contraction speed of the shock absorber D is high.

As described above, the shock absorber D of the first embodiment includes the cylinder1, the rod2movably inserted into the cylinder1, and the piston (partition member)3that has a disk shape and is inserted into the cylinder1to partition the inside of the cylinder1into the extension side chamber R1and the compression side chamber R2as the two working chambers, and the piston (partition member)3includes the extension side ports (ports)3band the compression side ports (ports)3cthat communicate the extension side chamber R1and the compression side chamber R2, and the choke passage T1that includes a portion communicating the extension side chamber R1and the compression side chamber R2and passing through the outer peripheral side of the extension side ports (ports)3band the compression side ports (ports)3cof the piston (partition member)3along the circumferential direction.

In the shock absorber D configured as described above, since the choke passage T1includes a portion provided along the circumferential direction in a dead space of the outer periphery of the extension side ports (ports)3band the compression side ports (ports)3cof the piston (partition member)3having a disk shape, the passage length of the choke passage T1can be increased without increasing the axial length of the piston (partition member)3. Since the passage length of the choke passage T1can be increased, the degree of freedom in designing the passage length of the choke passage T1is improved, and the choke passage T1having a sufficient length can be formed in the piston (partition member)3. As described above, with the shock absorber D of the first embodiment, the passage length of the choke passage T1can be increased, and it is not necessary to use an orifice the damping force characteristic of which is difficult to set as a countermeasure for the insufficient damping force, and therefore, the damping force at the time of extension and contraction at a low speed can be increased, and the damping force characteristic can be easily set.

Note that, in the choke passage T1, as described above, since the choke passage T1may include a portion provided along the circumferential direction in a dead space of the inner periphery of the extension side ports (ports)3band the compression side ports (ports)3cof the piston (partition member)3having a disk shape. Also with the shock absorber D configured as described above, the passage length of the choke passage T1can be increased, and it is not necessary to use an orifice the damping force characteristic of which is difficult to set as a countermeasure for the insufficient damping force, and therefore, the damping force at the time of extension and contraction at a low speed can be increased, and the damping force characteristic can be easily set.

In addition, with the shock absorber D of the first embodiment, since the portion provided in the inner periphery or the outer periphery of the extension side ports (ports)3band the compression side ports (ports)3cof the piston (partition member)3in the choke passage T1has a spiral shape, the length of the choke passage T1can be set by setting the number of times of circulating the inside of the piston (partition member)3in the circumferential direction by effectively using the dead space of the piston (partition member)3, and the degree of freedom in designing the passage length of the choke passage T1can be greatly improved.

Note that, in the shock absorber D of the first embodiment, the partition member is the piston3, but a partition wall or the like used in a manner of being fixed to the cylinder1may be used as the partition member. For example, in a double cylinder type shock absorber including a reservoir outside the cylinder, a valve case fixed to an end portion of the cylinder may be used as a partition member, the reservoir and a compression side chamber partitioned by the valve case may be used as working chambers, and a choke passage may be formed in the valve case.

In addition, as illustrated inFIG.7, a piston20may be configured as described below as a third modification of the partition member. As illustrated inFIGS.7to10, the piston20includes a piston main body21having a disc shape and including an insertion hole21athat allows insertion of the rod2at the center, an extension portion22having a cylindrical shape suspended from an outer periphery of a lower end of the piston main body21inFIG.9, a ring mounting portion23having a plurality of annular grooves provided on an outer periphery of the extension portion partway on the outer periphery of the piston main body21, and a piston ring24mounted on the outer periphery of the ring mounting portion23. In the piston20configured as described above, the outer diameter of the portion of the piston main body21where the piston ring24is not mounted is smaller than the outer diameter of the piston ring24, and an annular gap C is formed between this portion and the cylinder1. That is, a small-diameter portion25is formed in the piston20at the portion of the piston main body21where the piston ring24is not mounted.

In addition, the piston main body21of the piston20includes three compression side ports21cthat communicate the extension side chamber R1and the compression side chamber R2and have an arc shape as viewed in the axial direction, and three extension side ports21b, which are second ports, that communicate the extension side chamber R1and the compression side chamber R2and have a circular shape as viewed in the axial direction. The extension side ports21bare provided at equal intervals on the same circumference of the piston main body21of the piston20, and the compression side ports21care provided at equal intervals on the same circumference on the outer peripheral side of the extension side ports21bof the piston main body21of the piston20. Further, an extension side annular valve seat21dsurrounding the outer peripheral side of each extension side port21bis provided at the compression side chamber R2side end of the piston main body21, and an inner annular valve seat21eprovided between the extension side ports21band the compression side ports21cand surrounding the outer peripheral side of each extension side port21band a compression side annular valve seat21fsurrounding the outer peripheral side of each compression side port21care provided at the extension side chamber R1side end of the piston main body21.

The extension side ports21band the compression side ports21care provided at positions displaced from each other in the circumferential direction with respect to the piston main body21, that is, at positions not aligned in a radial direction with respect to the piston main body21. Furthermore, as illustrated inFIG.9, the compression side port21cprovided on the outer peripheral side of the extension side port21bwith respect to the piston main body21includes a bent portion21c1bent toward the inner peripheral side of the piston main body21at the center.

Further, the piston20is provided with a choke passage T2. The choke passage T2is configured to include a portion T2athat opens from the small-diameter portion25that is the outer periphery of the piston main body21, extends obliquely downward inFIG.9and in the direction of the center of the piston20, and reaches the center of the piston main body21in the axial direction, a portion T2bthat opens from a position that is a lower end of the piston main body21inFIG.9, is an outer periphery of the openings of the extension side ports21b, and faces the extension side ports21bin the radial direction, extends in the axial direction, and reaches the center of the piston main body21in the axial direction, and a portion T2cthat is disposed on the outer peripheral side of the compression side ports21cthat are ports and the extension side ports21bthat are second ports in the piston20, passes along the circumferential direction, and communicates the portion T2aand the portion T2bas illustrated inFIG.8. Note that the circumferential length of the portion T2cis set to be longer than the axial length of the piston main body21of the piston20, but can be set to any length according to the setting of the damping force. In addition, the portion T2cmay extend along the circumferential direction while meandering in the radial direction of the piston main body21.

The portion T2cof the choke passage T2passing through the outer peripheral side of the compression side ports21cand the extension side ports21bof the piston20along the circumferential direction passes through the outside of the bent portions21c1of the compression side ports21c, and is disposed at a position overlapping the open ends of the compression side ports21cwhen the piston20is viewed from the axial direction as illustrated inFIG.8. That is, the portion T2cof the choke passage T2is disposed in the outer periphery of the bent portions21c1of the compression side ports21cand on the side opposite to the bent side of the bent portions21c1, and is disposed between the openings of the compression side ports21con the extension side chamber R1side and the openings on the compression side chamber R2side in the axial direction of the piston20. From the viewpoint of the compression side ports21c, the compression side ports21cinclude the bent portions21c1that avoid the portion T2cof the choke passage T2at the center.

As described above, since the compression side ports21cinclude the bent portions21c1partway, a space for providing the portion T2cpassing through the outer peripheral side of the compression side ports21calong the circumferential direction of the choke passage T2is formed on the outer peripheral side of the bent portions21c1of the piston20, and the choke passage T2can be formed in the piston20without difficulty. Note that since each extension side port21b, which is a second port, is provided on the inner peripheral side of each compression side port21c, it is not necessary to provide a bent portion in order to secure a space for providing the portion T2cof the choke passage T2. Note that when a space for providing the portion T2cof the choke passage T2cannot be secured in the piston3without the bent portions because the compression side ports21cand the extension side ports21bare provided on the same circumference, the compression side ports21cand the extension side ports21bmay be provided with the bent portions.

In addition, the choke passage T2may be formed as in a piston20of a fourth modification illustrated inFIG.11and a fifth modification illustrated inFIG.12. Specifically, the choke passage T2includes only the portion T2c, and as illustrated inFIG.11, the compression side ports21cand the extension side ports21bcommunicate with each other in the piston3, and the extension side chamber R1and the compression side chamber R2communicate with each other via the compression side ports21cand the extension side ports21b. Furthermore, as illustrated inFIG.12, the portion T2cof the choke passage T2may be disposed on the inner peripheral side of the extension side ports21band the compression side ports21cof the piston20. In this case, a space for providing the portion T2cmay be secured by providing bent portions21b1bent toward the outer peripheral side of the piston20using the extension side ports21bas ports so that the extension side ports21bon the inner peripheral side do not compress the space for providing the portion T2cof the choke passage T2, and the bent portions may not be provided for the compression side ports21c. Note that when the choke passage T2is disposed on the inner peripheral side of the extension side ports21band the compression side ports21cof the piston20, similarly to the example illustrated inFIG.6, one end and an other end of the choke passage T2may be opened to the insertion hole21a, and the rod2may be provided with a passage2din which one opening communicates with the extension side chamber R1and a passage2ein which the other opening communicates with the compression side chamber R2.

Even when the choke passage T2is formed in the piston20as described above, since the choke passage T2includes the portion provided along the circumferential direction in the dead space on the outer peripheral side of the compression side ports (ports)21cof the piston (partition member)20having a disk shape, the passage length of the choke passage T2can be increased along the circumferential direction in which the length can be easily obtained as compared with the axial length of the piston (partition member)20without increasing the axial length of the piston (partition member)20. Since the passage length of the choke passage T2can be increased, the degree of freedom in designing the passage length of the choke passage T2is improved, and the choke passage T2having a sufficient length can be formed in the piston (partition member)20. Therefore, with the shock absorber D of the first embodiment in which the choke passage T2is formed in the piston20as described above, the passage length of the choke passage T2can be increased, and it is not necessary to use an orifice the damping force characteristic of which is difficult to set as a countermeasure for the insufficient damping force, and therefore, the damping force at the time of extension and contraction at a low speed can be increased, and the damping force characteristic can be easily set.

Note that, in the choke passage T2, as described above, the choke passage T2may include a portion provided along the circumferential direction in a dead space on the inner peripheral side of the compression side ports (ports)21cof the piston (partition member)20having a disk shape. Also with the shock absorber D configured as described above, the passage length of the choke passage T2can be increased, and it is not necessary to use an orifice the damping force characteristic of which is difficult to set as a countermeasure for the insufficient damping force, and therefore, the damping force at the time of extension and contraction at a low speed can be increased, and the damping force characteristic can be easily set.

In addition, in the piston (partition member)20of the third modification described above, the compression side ports (ports)21cinclude the bent portions21c1that bend to the inner periphery of the piston (partition member)20, and the portion T2cof the choke passage T2that is disposed on the outer peripheral side of the compression side ports (ports)21cof the piston (partition member)20and passes along the circumferential direction is disposed on the outer peripheral side of the bent portions21c1of the compression side ports (ports)21cand on the side opposite to the bent side of the bent portions21c1. With the shock absorber D configured as described above, a space for providing the portion T2cpassing through the outer peripheral side of the compression side ports (ports)21calong the circumferential direction of the choke passage T2is formed on the outer peripheral side of the bent portions21c1of the piston (partition member)20, and the choke passage T2can be formed in the piston (partition member)20without difficulty. Note that, as illustrated inFIG.12, when the portion T2cof the choke passage T2is disposed on the inner peripheral side of the extension side ports (ports)21bof the piston20, the extension side ports (ports)21bmay be provided with the bent portions21b1bent toward the outer peripheral side of the piston (partition member)20, and the portion T2cof the choke passage T2disposed on the inner peripheral side of the extension side ports (ports)21band passing along the circumferential direction may be disposed on the inner peripheral side of the bent portions21b1of the extension side ports (ports)21bof the piston (partition member)20and on the side opposite to the bent side of the bent portions21b1. With the shock absorber D configured as described above, a space for providing the portion T2cpassing through the inner periphery of the extension side ports (ports)21bof the piston20along the circumferential direction of the choke passage T2is formed on the inner peripheral side of the bent portions21b1of the piston20, and the choke passage T2can be formed in the piston20without difficulty.

Furthermore, the piston (partition member)20of the third modification described above includes the small-diameter portion25that forms the annular gap C facing the extension side chamber (one working chamber) R1with respect to the cylinder1on the outer periphery of the extension side chamber side end that is one end, and the choke passage T2opens from the small-diameter portion25and reaches the compression side chamber side end that is the other end of the piston (partition member)20. In the piston (partition member)20configured as described above, the outlet end of the choke passage T2on the extension side chamber R1side is formed in the small-diameter portion25that is an outer peripheral side portion of the piston (partition member)20, and it is not necessary to provide the outlet end of the choke passage T2on the extension side chamber R1side at an end portion of the piston (partition member)20facing the extension side chamber (one working chamber) R1. Accordingly, the outlet ends of the compression side ports (ports)21ccan be disposed on the outer peripheral side of the end portion of the piston (partition member)20facing the extension side chamber (one working chamber) R1without being interfered with by the choke passage T2. Therefore, with the shock absorber D configured as described above, since the diameter of the compression side annular valve seat21fsurrounding the compression side ports (ports)21cformed in the piston (partition member)20can be secured to be large, the pressure receiving area of the compression side leaf valve8receiving the pressure of the compression side chamber R2increases, and the valve opening responsiveness of the leaf valve8is improved. Therefore, with the shock absorber D configured as described above, since the valve opening responsiveness of the leaf valve8can be improved, variations in damping force characteristic for each product can be reduced.

Note that the small-diameter portion may be provided on the outer periphery on the piston20on the compression side chamber side, and in this case, it is sufficient if the extension side port21bare disposed on the outer peripheral side of the compression side ports21cand the extension side chamber side end of the choke passage T2is opened to the small-diameter portion. In this way, when the outlet ends of the extension side ports21bare formed on the outer peripheral side of the piston20, the choke passage T2does not become interference, and the diameter of the extension side annular valve seat21dsurrounding the extension side ports21bcan be increased to improve the valve opening responsiveness of the leaf valve7, and variations in damping force characteristic of the shock absorber D for each product can be reduced.

Furthermore, the piston (partition member)20of the fourth modification described above includes the plurality of compression side ports (ports)21cthat allows the flow of the fluid from the compression side chamber R2to the extension side chamber R1, and the plurality of extension side ports (second ports)21bthat is provided at positions on the inner peripheral side of the compression side ports (ports)21cof the piston (partition member)20and not facing the compression side ports (ports)21cin the radial direction and allows the flow of the fluid from the extension side chamber R1to the compression side chamber R2, and one end of the choke passage T2is connected to one of the compression side ports (ports)21c, and the other end of the choke passage T2is connected to one of the extension side ports (second ports)21b. In the piston (partition member)20configured as described above, since the outlet ends at both ends of the choke passage T2are not formed at the extension side chamber side end and the compression side chamber side end of the piston (partition member)20, the diameter of the compression side annular valve seat21fsurrounding the compression side ports (ports)21cand the diameter of the extension side annular valve seat21dsurrounding the extension side ports21bcan be increased. Therefore, with the shock absorber D configured as described above, the valve opening responsiveness of the leaf valves7and8can be improved, and variations in damping force characteristic of the shock absorber D for each product can be reduced. Note that, in the first embodiment, the compression side ports21care ports, and the extension side ports21bare second ports, but the compression side ports21cmay be second ports, and the extension side ports21bmay be ports.

Second Embodiment

As illustrated inFIG.13, a shock absorber D1according to the second embodiment includes a cylinder1, a rod2movably inserted into the cylinder1, and a piston30, which is a partition member, that is inserted into the cylinder1and defines an extension side chamber R1and a compression side chamber R2as two working chambers in the cylinder1. Further, similarly to the shock absorber D, the shock absorber D1is used by being interposed between a vehicle body and an axle of a vehicle, which is not illustrated, to suppress vibrations of the vehicle body and the wheels. Note that, among the members constituting the shock absorber D1of the second embodiment, the same members as the members constituting the shock absorber D of the first embodiment are denoted by the same reference numerals as the members of the shock absorber D of the first embodiment.

Each part of the shock absorber D1will be described in detail below. As illustrated inFIG.13, a rod guide10having an annular shape is mounted on an upper end of the cylinder1, and a lower end of the cylinder1is closed by a cap11. Further, in the cylinder1, the rod2on which the piston30is mounted at a distal end is movably inserted.

The rod2is slidably inserted into the rod guide and inserted into the cylinder1, and movement in the axial direction is guided by the rod guide10. In addition, the inside of the cylinder1is partitioned by the piston30into the extension side chamber R1and the compression side chamber R2that are filled with fluid such as hydraulic fluid. Note that a liquid other than the hydraulic fluid such as water and an aqueous solution may also be used as the fluid. In addition, the fluid may be a gas instead of a liquid.

Note that a gas chamber G is defined inside the cylinder1below the compression side chamber R2by a free piston6slidably inserted into the cylinder1. Further, when the rod2is displaced in the axial direction with respect to the cylinder1, the gas chamber G is expanded or contracted by the free piston6being displaced in the axial direction with respect to the cylinder1according to the volume of the rod2entering and leaving the cylinder1, and the volume of the rod2entering and leaving the cylinder1is compensated by a change in the volume of the gas chamber G. In this manner, the shock absorber D1is a so-called single cylinder type shock absorber, but may be configured as a double cylinder type shock absorber including a reservoir outside the cylinder1.

Returning to this, the rod2includes a screw portion2bprovided on the outer periphery of a distal end portion2a, which is a lower end inFIG.13, and a C-ring2cattached to the outer periphery above the distal end portion2a. An extension side leaf valve7and a compression side leaf valve8formed in an annular shape are attached to the outer periphery of the distal end portion2aof the rod2together with the piston30having an annular shape. The leaf valves7and8and the piston30are sandwiched between a piston nut9screwed to the screw portion2band the C-ring2cand fixed to the outer periphery of the distal end portion2aof the rod2.

As illustrated inFIGS.14to16, the piston30includes a first member31having an annular shape and a second member32having an annular shape fitted to the outer periphery of the first member31. The first member31has a disk shape, and includes an insertion hole31athrough which the distal end portion2aof the rod2is inserted at the center, and extension side ports31band compression side ports31cthat are provided on the same circumference and have an arc shape as viewed in the axial direction. In addition, three extension side ports31band three compression side ports31care alternately arranged on the same circumference in the first member31, and serve as ports in the piston30, which is a partition member.

In addition, the first member31includes a valve seat31dhaving a petal shape surrounding each extension side port31bat an end portion facing the compression side chamber R2side as illustrated inFIG.16and a valve seat31ehaving a petal shape surrounding each compression side port31cat an end portion facing the extension side chamber R1side as illustrated inFIG.14. As described above, the extension side ports31bprovided in the piston30of the shock absorber D1of the second embodiment are independent opening ports that do not communicate with each other, and the compression side ports31care also independent opening ports that do not communicate with each other.

Further, as illustrated inFIGS.14to16, the first member31includes a groove31fhaving a spiral shape along the circumferential direction on the outer periphery that is a facing peripheral portion facing the second member32. The groove31fopens from the extension side chamber R1side end of the first member31, which is an upper end inFIG.15, goes around the outer periphery of the first member31in a spiral shape, and opens to the compression side chamber R2side end of the first member31, which is a lower end inFIG.15. The groove31fis formed so as not to come into contact with the extension side ports31band the compression side ports31cin a state where the entirety is opened to the outside in the thick portion of the outer periphery of the extension side ports31band the compression side ports31cof the first member31.

On the other hand, as illustrated inFIG.15, the second member32includes a piston ring32ahaving an annular shape on the outer periphery. Further, when the second member32is fitted to the outer periphery of the first member31, the inner peripheral surface faces the groove31fwhile leaving the outlet end of the groove31fon the extension side chamber R1side and the outlet end on the compression side chamber R2side. Therefore, when the second member32is fitted to the outer periphery of the first member31, the groove31fforms a choke passage T3having a spiral shape in which only both ends are opened.

That is, when the piston30, which is a partition member, is assembled by fitting the first member31to the inner periphery of the second member32, the choke passage T3is formed by the groove31f. The choke passage T3has a spiral shape and opens from the outer peripheral side of the valve seat31eat the extension side chamber R1side end of the piston30to the outer peripheral side of the valve seat31dat the compression side chamber R2side end of the piston30and communicates the extension side chamber R1and the compression side chamber R2.

Note that, like a piston30of the first modification illustrated inFIG.17, the groove31fmay not be provided in the outer periphery of the first member31, but a groove32bmay be formed in the inner periphery of the second member32that is a facing peripheral portion facing the first member31. Also in this case, when the second member32is fitted to the first member31, a choke passage T3ais formed by the groove32b.

In addition, although not illustrated, the choke passage T3may have a shape having a spiral portion partway. That is, the choke passage T3may be formed by a spiral portion, a portion that opens in the axial direction from the outer peripheral side of the valve seat31eat the extension side chamber R1side end of the piston30and is connected to the spiral portion, and a portion that opens in the axial direction from the outer peripheral side of the valve seat31dat the compression side chamber R2side end of the piston30and is connected to the spiral portion. As described above, the extending direction and the cross-sectional shape of choke passage T3can be arbitrarily set by the extending direction and the cross-sectional shape of the groove31f. Accordingly, the groove31fmay have a shape meandering in the axial direction of the first member31and extending along the circumferential direction as in a piston30of the second modification illustrated inFIG.18.

In addition, as in a piston30of the third modification illustrated inFIG.19, as a structure in which a second member34is fitted to the inner periphery of a first member33, a groove33cmay be formed in the inner periphery of the first member33using the inner periphery of the first member33having extension side ports33aand compression side ports33bas a facing peripheral portion. In this case, the second member34is attached to the distal end portion2aof the rod2, and the first member33is brought into sliding contact with the cylinder1. The groove33chas one end connected to one of the extension side ports33aand the other end connected to one of the compression side ports33b, and communicates the extension side chamber R1and the compression side chamber R2via the extension side port33aand the compression side port33b. Even when the groove33cis formed in the inner periphery of the first member33as described above, when the second member34is fitted to the first member33, a choke passage T3bis formed by the groove33c. Note that when the choke passage T3bis disposed on the inner peripheral side of the extension side ports33aand the compression side ports33bof the piston30as described above, instead of forming the groove33cin the inner periphery of the first member33, a groove for forming the choke passage may be provided using the outer periphery of the second member34as a facing peripheral portion.

Note that the piston30configured as described above includes the two parts: the first member31,33and the second member32,34, and the groove31f,32b,33cis formed in the facing peripheral portion that is a peripheral surface facing the counterpart of the first member31,33or the second member32,34, so that the groove31f,32b,33chaving a shape along the circumferential direction can be processed from the outside. In addition, when the groove is provided using the outer periphery of the first member31,33or the second member32,34as a facing peripheral portion, the first member31,33or the second member32,34can be manufactured by sintering using a mold although depending on the shape of the groove. Therefore, in the shock absorber D1of the second embodiment, the choke passage T3, T3a, T3bcan be easily provided inside the piston30. In addition, a 3D printer may be used in manufacturing the piston30. By using a 3D printer, the first member31,33or the second member32,34having the groove31f,32b,33cthat need to be processed through a plurality of processes can be manufactured by single processing.

The extension side leaf valve7is a stack leaf valve in which a plurality of annular plates is stacked, and is stacked on a lower surface of the piston30facing the compression side chamber R2inFIG.13. The inner periphery of the extension side leaf valve7is sandwiched and fixed between the piston nut9and the C-ring2c, bending of the outer peripheral side, which is a free end, is allowed, and the extension side leaf valve7is seated and unseated with respect to the valve seat31dto open and close outlet ends of the extension side ports31b. As described above, when the extension side leaf valve7is placed on the piston30, sandwiched between the piston nut9and the C-ring2cof the rod2, and fixed to the rod2, the extension side leaf valve7abuts on the valve seat31dand is stacked on the piston30. Further, in a state where the outer periphery is seated on the valve seat31d, the extension side leaf valve7closes the extension side ports31band disconnects communication between the extension side chamber R1and the compression side chamber R2via the extension side ports31b. In addition, when the extension side leaf valve7is bent by receiving a pressure of the extension side chamber R1through the extension side ports31band unseated from the valve seat31d, the extension side ports31bare opened, the extension side chamber R1and the compression side chamber R2communicate with each other, and resistance is applied to the flow of the hydraulic fluid from the extension side chamber R1to the compression side chamber R2.

In addition, the compression side leaf valve8is a stack leaf valve in which a plurality of annular plates is stacked, and is stacked on an upper surface of the piston30facing the extension side chamber R1inFIG.13. The inner periphery of the compression side leaf valve8is sandwiched and fixed between the piston nut9and the C-ring2c, bending of the outer peripheral side, which is a free end, is allowed, and the compression side leaf valve8is seated and unseated with respect to the valve seat31eto open and close outlet ends of the compression side ports31c. As described above, when the compression side leaf valve8is placed on the piston30, sandwiched between the piston nut9and the C-ring2cof the rod2, and fixed to the rod2, the compression side leaf valve8abuts on the valve seat31eand is stacked on the piston30. Further, in a state where the outer periphery is seated on the valve seat3e, the compression side leaf valve8closes the compression side ports31cand disconnects communication between the compression side chamber R2and the extension side chamber R1via the compression side ports31c. In addition, when the compression side leaf valve8is bent by receiving a pressure of the compression side chamber R2through the compression side ports31cand unseated from the valve seat31e, the compression side ports31care opened, the compression side chamber R2and the extension side chamber R1communicate with each other, and resistance is applied to the flow of the hydraulic fluid from the compression side chamber R2to the extension side chamber R1.

The shock absorber D1is configured as described above, and the operation of the shock absorber D1will be described hereinafter. First, an operation when the rod2moves upward inFIG.13with respect to the cylinder1and the shock absorber D1performs an extension operation will be described. When the shock absorber D1performs the extension operation, the piston30moves upward inFIG.13with respect to the cylinder1, and thus, the extension side chamber R1is compressed and the compression side chamber R2is enlarged.

Then, the pressure in the extension side chamber R1increases. This pressure acts on the extension side leaf valve7through the extension side ports31bthat are not closed by the leaf valve8stacked on the upper end of the piston30inFIG.13. When the extension speed of the shock absorber D1is low and the pressure in the extension side chamber R1does not reach the valve opening pressure of the leaf valve7, the hydraulic fluid moves from the extension side chamber R1to the compression side chamber R2only through the choke passage T3. Therefore, when the extension speed is low, the choke passage T3applies resistance to the hydraulic fluid passing therethrough and the shock absorber D1generates a damping force. In addition, when the extension speed of the shock absorber D1exceeds the low speed and reaches the high speed range, the leaf valve7bends and is unseated from the valve seat31dto open the extension side ports31b, so that the hydraulic fluid in the extension side chamber R1passes through the extension side ports31band the choke passage T3and moves to the compression side chamber R2. When the flow rate increases, the choke passage T3applies a larger resistance to the flow of the hydraulic fluid than the leaf valve7does. Therefore, when the extension speed of the shock absorber D1becomes high, the hydraulic fluid is less likely to pass through the choke passage T3, so that the hydraulic fluid preferentially passes through the extension side ports31b. Therefore, when the extension speed exceeds the low speed and reaches the high speed range, the shock absorber D1generates a damping force substantially by the resistance applied to the flow of the hydraulic fluid by the leaf valve7. Note that at the time of extension of the shock absorber D1, since the rod2is retracted from the inside of the cylinder1, the free piston6moves upward inFIG.13with respect to the cylinder1, the volume of the gas chamber G is enlarged by the volume of the rod2retracted from the inside of the cylinder1, and the volume of the rod2retracted from the inside of the cylinder1is compensated.

Next, an operation when the rod2moves downward inFIG.13with respect to the cylinder1and the shock absorber D1performs a contraction operation will be described. When the shock absorber D1performs the contraction operation, the piston30moves downward inFIG.13with respect to the cylinder1, and thus, the compression side chamber R2is compressed, and the extension side chamber R1is enlarged.

Then, the pressure in the compression side chamber R2increases. This pressure acts on the compression side leaf valve8through the compression side ports31cthat are not closed by the leaf valve7stacked on the lower end of the piston30inFIG.13. When the contraction speed of the shock absorber D1is low and the pressure in the compression side chamber R2does not reach the valve opening pressure of the leaf valve8, the hydraulic fluid moves from the compression side chamber R2to the extension side chamber R1only through the choke passage T3. Therefore, when the contraction speed is low, the choke passage T3applies resistance to the hydraulic fluid passing therethrough and the shock absorber D1generates a damping force. In addition, when the contraction speed of the shock absorber D1exceeds the low speed and reaches the high speed range, the leaf valve8bends and is unseated from the valve seat31eto open the compression side ports31c, so that the hydraulic fluid in the compression side chamber R2passes through the compression side ports31cand the choke passage T3and moves to the extension side chamber R1. When the flow rate increases, the choke passage T3applies a larger resistance to the flow of the hydraulic fluid than the leaf valve8does. Therefore, when the contraction speed of the shock absorber D1becomes high, the hydraulic fluid is less likely to pass through the choke passage T3, so that the hydraulic fluid preferentially passes through the compression side ports31c. Therefore, when the contraction speed exceeds the low speed and reaches the high speed range, the shock absorber D1generates a damping force substantially by the resistance applied to the flow of the hydraulic fluid by the leaf valve8. Note that at the time of contraction of the shock absorber D1, since the rod2enters the inside of the cylinder1, the free piston6moves downward inFIG.13with respect to the cylinder1, the volume of the gas chamber G is reduced by the volume of the rod2entering the inside of the cylinder1, and the volume of the rod2entering the inside of the cylinder1is compensated.

As described above, when the extension and contraction speed of the shock absorber D1is low, the shock absorber D1generates a damping force with the choke passage T3, and when the extension and contraction speed of the shock absorber D1is high, the shock absorber D1generates a damping force with the leaf valves7and8. Therefore, the damping force characteristic of the shock absorber D1of the second embodiment is a characteristic that becomes the choke characteristic substantially proportional to the extension and contraction speed when the extension and contraction speed of the shock absorber D1is low and changes to the valve characteristic of the leaf valves7and8when the extension and contraction speed of the shock absorber D1is high.

As described above, the shock absorber D1of the second embodiment includes the cylinder1, the rod2movably inserted into the cylinder1, and the piston (partition member)30that has a disk shape and is inserted into the cylinder1to partition the inside of the cylinder1into the extension side chamber R1and the compression side chamber R2as the two working chambers, and the piston (partition member)30includes the first member31that has an annular shape and has the extension side ports (ports)31band the compression side ports (ports)31cthat communicate the extension side chamber R1and the compression side chamber R2, and the second member32that has an annular shape and is fitted to the inner periphery or the outer periphery of the first member31, the first member31has the groove31fformed along the circumferential direction in the outer periphery that is a facing peripheral portion facing the second member32and communicating the extension side chamber R1and the compression side chamber R2, and the choke passage T3is formed by the groove31fby fitting the first member31and the second member32.

In the shock absorber D1configured as described above, since the choke passage T3is provided along the circumferential direction in a dead space on the outer peripheral side of the extension side ports (ports)31band the compression side ports (ports)31cof the piston (partition member)30having a disk shape, the passage length of the choke passage T3can be increased without increasing the axial length of the piston (partition member)30. Since the passage length of the choke passage T3can be increased, the degree of freedom in designing the passage length of the choke passage T3is improved, and the choke passage T3having a sufficient length can be formed in the piston (partition member)30. As described above, with the shock absorber D1of the second embodiment, the passage length of the choke passage T3can be increased, and it is not necessary to use an orifice the damping force characteristic of which is difficult to set as a countermeasure for the insufficient damping force, and therefore, the damping force at the time of extension and contraction at a low speed can be increased, and the damping force characteristic can be easily set.

In addition, since the choke passage T3is formed by the groove31fprovided in the outer periphery of the first member31, the piston (partition member)30having the choke passage T3having a complicated shape can be manufactured by simple processing.

Note that, as described above, it is sufficient if the groove forming the choke passage T3is provided in the facing peripheral portion of any one of the first member31and the second member32, and therefore, the groove may be provided in the inner periphery of the second member32, and in the case of a structure in which the second member34is fitted to the inner periphery of the first member33, the groove may be provided in the inner periphery of the first member or the outer periphery of the second member34.

In addition, with the shock absorber D1of the second embodiment, since the choke passage T3is formed by the groove31f,33c,34bhaving a spiral shape provided in the outer periphery of the first member31, the inner periphery of the first member33, the inner periphery of the second member32, or the outer periphery of the second member34, the length of the choke passage T3can be set by setting the number of times of circulating the inside of the piston (partition member)30in the circumferential direction by effectively using the dead space of the piston (partition member)30, and the degree of freedom in designing the passage length of the choke passage T3can be greatly improved.

Furthermore, as in the piston30of the second modification, the choke passage T3may be formed by the groove31fformed to meander in the axial direction of the piston (partition member)30and extend in the circumferential direction with respect to the outer periphery that is the facing peripheral portion of the first member31. Also in the shock absorber D1configured as described above, the length of the choke passage T3can be set by setting the number of times of meandering the inside of the piston (partition member)30in the axial direction by effectively using the dead space of the piston (partition member)30, and the degree of freedom in designing the passage length of the choke passage T3can be greatly improved. Note that also when the choke passage T3is formed by such a meandering groove, it is sufficient if the groove is provided in the inner periphery of the first member33, the inner periphery of the second member32, or the outer periphery of the second member34in addition to the outer periphery of the first member31.

Note that, in the shock absorber D1of the second embodiment, the partition member is the piston30, but a partition wall or the like used in a manner of being fixed to the cylinder1may be used as the partition member. For example, in a double cylinder type shock absorber including a reservoir outside the cylinder, a valve case fixed to an end portion of the cylinder may be used as a partition member, the reservoir and a compression side chamber partitioned by the valve case may be used as working chambers, and a choke passage may be formed in the valve case.

In addition, as illustrated inFIG.20, a piston40may be configured as described below as a fourth modification of the partition member. As illustrated inFIGS.20to23, the piston40is configured to include a first member41and a second member44fitted to the outer periphery of the first member41.

The first member41includes a main body portion42having a disk shape and including an insertion hole42athat allows insertion of the rod2at the center, and an extension portion43having a cylindrical shape suspended from the outer periphery of the lower end of the main body portion42inFIG.22. In addition, the main body portion42includes three compression side ports42c, which are ports, that communicate the extension side chamber R1and the compression side chamber R2and have an arc shape as viewed in the axial direction, and three extension side ports42b, which are third ports, that communicate the extension side chamber R1and the compression side chamber R2and have a circular shape as viewed in the axial direction. The extension side ports42bare provided at equal intervals on the same circumference of the main body portion42, and the compression side ports42care provided at equal intervals on the same circumference on the outer peripheral side of the extension side ports21bof the main body portion42. Further, an extension side annular valve seat42dsurrounding the outer peripheral side of the extension side ports42bis provided at the compression side chamber R2side end of the main body portion42, and an inner annular valve seat42eprovided between the extension side ports42band the compression side ports42cand surrounding the extension side ports42band a compression side annular valve seat42fsurrounding the outer periphery of the compression side ports42care provided at the extension side chamber R1side end of the main body portion42.

The extension side ports42band the compression side ports42care provided at positions displaced from each other in the circumferential direction with respect to the main body portion42, that is, at positions not aligned in a radial direction with respect to the main body portion42. Furthermore, as illustrated inFIG.22, the compression side port42cprovided on the outer peripheral side of the main body portion42includes a bent portion42c1bent toward the inner peripheral side of the first member41at the center. In addition, the extension portion43includes a flange portion43ahaving a cylindrical shape, suspended from the outer periphery of the lower end of the main body portion42, and protruding toward the outer peripheral side at the lower end. The outer diameter of the extension portion43is set to be the same diameter as that of the main body portion42except for the flange portion43a, and the outer periphery of the extension portion43and the outer periphery of the main body portion42are flush with each other. The second member44having an annular shape is fitted from the upper end of the main body portion42of the first member41configured as described above inFIG.22to the upper side of the flange portion43aof the extension portion43.

Further, in addition, a groove42gis provided on the outer periphery that is a facing peripheral portion of the main body portion42of the first member41facing the second member44. The groove42gis provided along the circumferential direction on the outer periphery of the main body portion42of the first member41. One end of the groove42gis connected to the extension side port42bthrough a hole42hextending in the radial direction through the wall of the main body portion42, and the other end of the groove42gis connected to the compression side port42cthrough a hole42iextending in the radial direction through the wall of the first member41. Therefore, the groove42gcommunicates the extension side chamber R1and the compression side chamber R2via the extension side port42band the compression side port42c. In addition, the groove42gpasses through the outside of the bent portions42clof the compression side ports42c, and as illustrated inFIG.21, the groove is disposed at a position passing through the vicinity of the open ends of the compression side ports42cwhen the piston40is viewed from the axial direction.

On the other hand, as illustrated inFIG.22, the second member44includes a piston ring44ahaving an annular shape on the outer periphery. Further, when the second member44is fitted to the outer periphery of the first member41, the inner peripheral surface faces the groove42g. Therefore, when the second member44is fitted to the outer periphery of the first member41, the groove42gis closed by the second member44, and a choke passage T4that communicates the extension side chamber R1and the compression side chamber R2through the extension side port42band the compression side port42cis formed.

The choke passage T4thus formed is disposed in the outer periphery of the bent portions42c1of the compression side ports42cand on the side opposite to the bent side of the bent portions42c1, and is disposed between the openings of the compression side ports42con the extension side chamber R1side and the openings on the compression side chamber R2side in the axial direction of the piston40. From the viewpoint of the compression side ports42c, the compression side ports42cinclude the bent portions42clthat avoid the groove42gforming the choke passage T4at the center.

The compression side ports42cinclude the bent portions42c1partway as described above, and a space for providing the groove42gis formed in the outer periphery of the bent portions42c1, and the choke passage T4can be formed in the piston40without difficulty. Note that since each extension side port42bis provided on the inner peripheral side of each compression side port42cof the piston40, it is not necessary to provide a bent portion in order to secure a space for providing the groove42g. Note that when a space for providing the groove42gforming the choke passage T4cannot be secured in the piston30without the bent portions because the compression side ports42cand the extension side ports42bare provided on the same circumference, the compression side ports42cand the extension side ports42bmay be provided with the bent portions.

Note that, although not illustrated, when the second member44is fitted to the inner periphery of the first member41, the groove forming the choke passage T4may be formed not in the outer periphery but in the inner periphery of the first member41. In this case, it is sufficient if a space for forming the groove is secured in the inner periphery of the first member41by providing the bent portions that bend toward the outer peripheral side of the first member41using the extension side ports42bon the inner peripheral side as ports and the compression side ports42con the outer peripheral side are third ports.

Even when the choke passage T4is formed in the piston40as described above, since the choke passage T4is formed by the groove42gprovided in the inner periphery or the outer periphery of the first member41, the choke passage T4is provided along the circumferential direction in a dead space on the outer peripheral side or the inner peripheral side of the extension side ports (ports)42band the compression side ports (ports)42cof the piston (partition member)40. Therefore, the passage length of the choke passage T4can be increased without increasing the axial length of the piston (partition member)40.

Since the passage length of the choke passage T4can be increased, the degree of freedom in designing the passage length of the choke passage T4is improved, and the choke passage T4having a sufficient length can be formed in the piston (partition member)40. Therefore, with the shock absorber D1of the second embodiment in which the choke passage T4is formed in the piston40as described above, the passage length of the choke passage T4can be increased, and it is not necessary to use an orifice the damping force characteristic of which is difficult to set as a countermeasure for the insufficient damping force, and therefore, the damping force at the time of extension and contraction at a low speed can be increased, and the damping force characteristic can be easily set.

In addition, in the piston (partition member)40of the fourth modification described above, the compression side ports (ports)42cinclude the bent portions42c1that bend to the inner peripheral side of the first member41, and the groove42gforming the choke passage T4is disposed in the outer periphery of the bent portions42c1of the compression side ports (ports)42cof the first member41and on the side opposite to the bent side of the bent portions42c1. With the shock absorber D1configured as described above, a space for providing the choke passage T4on the outer periphery is formed by the bent portions42c1of the first member41, and the choke passage T4can be formed in the piston (partition member)40without difficulty.

Furthermore, the first member41of the piston (partition member)40of the fourth modification described above includes the plurality of compression side ports (ports)42cthat allows the flow of the fluid from the compression side chamber R2to the extension side chamber R1, and the plurality of extension side ports (third ports)42bthat is provided at positions on the inner peripheral side of the compression side ports (ports)42cof the piston (partition member)40and not facing the compression side ports (ports)42cin the radial direction and allows the flow of the fluid from the extension side chamber R1to the compression side chamber R2, the groove42gis formed in the first member41, and one end of the choke passage T4is connected to one of the compression side ports (ports)42c, and the other end of the choke passage T4is connected to one of the extension side ports (third ports)42b. In the piston (partition member)40configured as described above, since the outlet ends at both ends of the choke passage T4are not formed at the extension side chamber side end and the compression side chamber side end of the piston (partition member)40, the diameter of the compression side annular valve seat42fsurrounding the compression side ports (ports)42cand the diameter of the extension side annular valve seat42dsurrounding the extension side ports42bcan be increased. Therefore, with the shock absorber D1configured as described above, the valve opening responsiveness of the leaf valves7and8can be improved, and variations in damping force characteristic of the shock absorber D1for each product can be reduced. Note that, in the second embodiment, the compression side ports42care ports, and the extension side ports42bare third ports, but the compression side ports42cmay be third ports, and the extension side ports42bmay be ports.

Although the preferred embodiments of the present invention have been described above in detail, modifications, variations, and changes can be made without departing from the scope of the claims.

The present application claims priority based on Japanese Patent Application No. 2021-020665 and Japanese Patent Application No. 2021-020667 filed with the Japan Patent Office on Feb. 12, 2021, and the entire contents of the applications are incorporated into the present specification by reference.