JP7481929B2 - Shock absorber - Google Patents

Description

The present invention relates to a shock absorber.

The shock absorber, for example, comprises a cylinder, a piston rod movably inserted into the cylinder, a piston slidably inserted into the cylinder and connected to the piston rod, an extension side chamber and a compression side chamber partitioned by the piston within the cylinder and filled with hydraulic oil, an outer cylinder that covers the outer periphery of the cylinder and forms a reservoir between the cylinder and the outer cylinder for storing hydraulic oil, a damping passage equipped with a damping valve that allows hydraulic oil to flow only from the extension side chamber to the reservoir and provides resistance to the flow of hydraulic oil passing through, a straightening passage provided in the piston that allows hydraulic oil to flow only from the compression side chamber to the extension side chamber, and a suction passage that allows hydraulic oil to flow only from the reservoir to the compression side chamber.

The shock absorber configured in this way is equipped with valves that function as check valves in the rectification passage and the suction passage, and is set up as a uniflow type in which hydraulic oil circulates through the reservoir, compression side chamber, and extension side chamber in order during expansion and contraction, before reaching the reservoir. The shock absorber then applies resistance in the damping passage to the flow of hydraulic oil discharged from inside the cylinder to the reservoir during expansion and contraction, generating a damping force that impedes expansion and contraction.

The valve provided on the piston is annular and is biased by a spring from the back side toward the piston, and is seated on an annular outer valve seat surrounding the outlet end of the piston's flow straightening passage and an annular inner valve seat provided on the inner side of the outlet end. When the valve is completely separated from the piston by pressure from the compression side chamber, it opens the flow straightening passage.

JP 2015-224780 A

Shock absorbers are used to dampen the vibrations of railway vehicles or structures, for example, by being installed between the body and bogie of a railway vehicle, between the bodies of adjacent railway vehicles, between an elastically supported structure and the ground, or between the columns and beams of a structure.

As mentioned above, when the object to be damped by the shock absorber is a heavy object such as a railway vehicle or structure, the shock absorber is required to generate a large damping force to suppress the vibration of the object. In order to increase the damping force of the shock absorber to meet such a requirement, the difference between the pressure in the expansion side chamber and the pressure in the compression side chamber can be increased.

However, when the pressure in the expansion-side chamber is higher than that in the compression-side chamber, the valve receives the pressure in the expansion-side chamber at its back and is pressed toward the piston, seating on the inner and outer valve seats and bending the middle part toward the piston. Therefore, if the difference between the pressure in the expansion-side chamber and the pressure in the compression-side chamber is increased, the valve may bend significantly and undergo plastic deformation, making it impossible to close the passage. Therefore, conventional shock absorbers have the problem that it is difficult to generate a high damping force by increasing the pressure inside the cylinder.

Therefore, the present invention aims to provide a shock absorber that can withstand high pressure inside the cylinder and generate high damping force.

In order to solve the above problems, the shock absorber of the present invention comprises a telescopic body having a cylinder and a rod inserted into the cylinder so as to be freely movable in the axial direction, a partition member having a passageway that separates two fluid chambers within the telescopic body and connects the fluid chambers, and a ring-shaped valve that can be moved axially toward and away from the partition member and opens and closes the passageway, the partition member has an annular inner valve seat that protrudes axially from the end facing the valve and on which the inner circumferential surface of the valve sits, an annular outer valve seat that protrudes axially from the end facing the valve and on which the outer circumferential surface of the valve sits, and an intermediate valve seat that protrudes axially from the end facing the valve, and the passageway and intermediate valve seat are formed between the inner valve seat and the outer circumferential valve seat.

A shock absorber configured in this way can prevent plastic deformation of the valve even if a larger axial force acts on the valve by increasing the pressure inside the cylinder compared to conventional shock absorbers.

In addition, the protruding height of the intermediate valve seat may be lower than the protruding heights of the inner valve seat and the outer valve seat. According to the shock absorber configured in this manner, the intermediate valve seat does not hinder the valve from seating on the inner valve seat and the outer valve seat, so that it is possible to ensure smooth blocking of the passage by the valve while preventing plastic deformation of the valve. Furthermore, the intermediate valve seat may be provided around the entire circumference of the partition member except for the opening of the passage.

The shock absorber may also be configured so that a plurality of passages are provided on the same circumference in the partition member, and an intermediate valve seat is provided between the passages. With a shock absorber configured in this manner, the intermediate valve seat is provided around the entire circumference of the partition member except for the openings of the passages, so that the intermediate valve seat supports the middle portion of the valve evenly in the circumferential direction, suppressing valve fatigue.

Furthermore, the intermediate valve seat is formed in a circumferential ring shape between the inner valve seat and the outer valve seat of the partition member, and multiple passages may be provided between the inner valve seat and the intermediate valve seat and between the intermediate valve seat and the outer valve seat. With a shock absorber configured in this way, the entire circumference of the middle part of the valve can be supported without interruption, which further suppresses fatigue due to valve bending, and since the passages are provided between the inner valve seat and the intermediate valve seat and between the outer valve seat and the intermediate valve seat, the flow area can be secured, so there is no problem in using the shock absorber in applications where it expands and contracts at high speed.

The shock absorber may be a piston in which a partition member is movably inserted into a cylinder and divides the inside of the cylinder into an expansion side chamber and a compression side chamber, a passage communicating the expansion side chamber and the compression side chamber, a reservoir for storing a fluid, a discharge passage communicating the expansion side chamber and the reservoir, a damping valve provided in the discharge passage to allow only the flow of fluid from the expansion side chamber to the reservoir and to provide resistance to the flow of the fluid, a suction passage communicating the reservoir and the compression side chamber, and a suction check valve provided in the suction passage to allow only the flow of fluid from the reservoir to the compression side chamber, and the valve may be a check valve that allows only the flow of fluid from the compression side chamber to the expansion side chamber through the passage. According to the shock absorber configured in this way, the practicality of the shock absorber set to a uniflow type can be improved.

As a result, the shock absorber of the present invention can withstand high pressure inside the cylinder and generate high damping force.

FIG. 2 is a vertical cross-sectional view of the shock absorber according to the embodiment. FIG. 2 is an enlarged cross-sectional view of a piston portion of the shock absorber according to the embodiment. FIG. 2 is a partially enlarged cross-sectional view of a piston of the shock absorber according to the embodiment. FIG. 2 is a plan view of a piston of the shock absorber according to one embodiment. FIG. 11 is a plan view of a piston of a shock absorber according to a first modified example of an embodiment.

The present invention will be described below based on the embodiment shown in the drawings. As shown in FIG. 1, the shock absorber D in one embodiment includes an expandable body E having a cylinder 1 and a rod 2 inserted into the cylinder 1 so as to be freely movable in the axial direction, a piston 3 as a partition member that divides the expandable body E into two fluid chambers, an expansion side chamber R1 and a compression side chamber R2, and has a passage 3a that connects the expansion side chamber R1 and the compression side chamber R2, and a ring-shaped valve V that can move axially toward and away from the piston 3 and opens and closes the passage 3a. This shock absorber D is used, for example, by being interposed between the car body and the bogie of a railway vehicle (not shown) to suppress vibration of the car body and the bogie.

The following is a detailed explanation of each part of the shock absorber D. In this embodiment of the shock absorber D, the expandable body E includes a cylinder 1, an outer tube 12 attached to the outer periphery of the cylinder 1, and a rod 2 movably inserted into the cylinder 1, as shown in FIG. 1.

A ring-shaped rod guide 10 is fitted to the left end of the cylinder 1 in FIG. 1, and the right end of the cylinder 1 in FIG. 1 is closed by a valve case 11. The cylinder 1 and the valve case 11 are housed in an outer cylinder 12, the right end of which is closed by a bottom cap 13 in FIG. 1. A ring-shaped reservoir R is formed between the cylinder 1 and the outer cylinder 12, in which a fluid such as hydraulic oil is stored together with gas.

The opening at the left end of the outer cylinder 12 in FIG. 1 is closed by a rod guide 10 attached to the outer cylinder 12. The cylinder 1 and the valve case 11 are sandwiched between the rod guide 10 fixed to the outer cylinder 12 and a bottom cap 13, and are housed within the outer cylinder 12 and fixed to the outer cylinder 12.

The rod 2 is inserted into the cylinder 1 by being slidably inserted into the rod guide 10, and its axial movement is guided by the rod guide 10. The telescopic body E thus comprises the cylinder 1 and the rod 2, with the rod 2 being able to move axially relative to the cylinder 1, and it telescopes and expands due to the axial movement of the rod 2 relative to the cylinder 1.

As shown in Fig. 2, the rod 2 includes a small diameter portion 2a provided at the tip, which is the right end in Fig. 2, having a small outer diameter, and having a piston 3 as a partition member attached to its outer periphery, a threaded portion 2b provided on the outer periphery of the tip of the small diameter portion 2a, a first step portion 2c formed at the boundary between the small diameter portion 2a and the left side of the small diameter portion 2a in Fig. 2, and a second step portion 2d and a third step portion 2e provided on the left side of the first step portion 2c in Fig. 2. In this way, in the shock absorber D of this embodiment, the rod 2 has a shape in which the outer diameter becomes smaller in three steps at the tip side.

The piston 3 is annular and is attached to the small diameter portion 2a of the rod 2 and is inserted movably into the cylinder 1, dividing the inside of the cylinder 1 into an extension side chamber R1 and a compression side chamber R2, which are filled with a fluid such as hydraulic oil. Note that the fluid may be a liquid other than hydraulic oil, such as water or an aqueous solution. The fluid may also be a gas instead of a liquid.

In this embodiment, as shown in FIG. 2, the piston 3 is configured to include a first piston division body 31 and a second piston division body 32 that are divided in the axial direction. The first piston division body 31 and the second piston division body 32 are both annular, and when stacked in the axial direction, they are integrated to form the piston 3.

The first piston segment 31 is made of cast iron, such as gray cast iron, spheroidal graphite cast iron, malleable cast iron, alloy cast iron, white cast iron, etc. Cast iron is a ternary alloy of iron containing 2.14 to 6.67% carbon and approximately 1 to 3% silicon, and is characterized by its excellent wear resistance. The first piston divided body 31 is annular, and includes an annular recess 31a formed along the circumferential direction on the outer periphery of the dividing surface A1 side, which is the right end side in FIG. 1, facing the dividing surface A2 side end of the second piston divided body 32, which is the left end in FIG. 1, a plurality of first ports 31b opening in the axial direction from the dividing surface A1 to the opposite dividing surface B1, an annular inner valve seat 31c protruding in the axial direction from the opposite dividing surface B1 side end on which the inner circumferential side of the valve V sits, an annular outer valve seat 31d protruding in the axial direction from the opposite dividing surface B1 side end on which the outer circumferential side of the valve V sits, and an intermediate valve seat 31e formed between the inner valve seat 31c and the outer valve seat 31d and protruding in the axial direction from the opposite dividing surface B1 side end.

As shown in FIG. 3, the end face W of the intermediate valve seat 31e is lower than an imaginary plane Z, which is a plane including the end face X of the inner valve seat 31c and the end face Y of the outer valve seat 31d. In other words, in the axial direction of the first piston divided body 31, the protruding height of the intermediate valve seat 31e from the end on the opposite side of the dividing surface B1 is lower than an imaginary plane Z, which includes both the end face X of the inner valve seat 31c and the end face Y of the outer valve seat 31d.

In addition, as shown in FIG. 4, the first port 31b of the first piston division 31 is formed in the intermediate valve seat 31e. In other words, the intermediate valve seat 31e is provided between the first ports 31b, 31b. Therefore, the intermediate valve seat 31e is formed between the inner peripheral valve seat 31c and the outer peripheral valve seat 31d with multiple arc-shaped portions obtained by dividing the annular ring by the first port 31b. As will be described later, the first port 31b forms the passage 3a. Therefore, the intermediate valve seat 31e is provided between the passages 3a.

The second piston divided body 32 is made of carbon steel containing carbon in the range of 0.02 to 2.14%. Carbon steel has high strength, and the second piston divided body 32 has a higher strength than the first piston divided body 31. The second piston divided body 32 is annular, and has a first seal groove 32a formed along the circumferential direction on the outer periphery, an annular groove 32b formed along the circumferential direction on the side end of the dividing surface A2, which is the left end in FIG. 1, and a plurality of second ports 32c that open in the axial direction from the opposite dividing surface B2 and communicate with the annular groove 32b, and is screwed to the screw portion 2b of the rod 2 through a screw groove (not shown) on the inner periphery.

The first piston split body 31 and the second piston split body 32 have the same outer diameter and an inner diameter that allows them to be attached to the outer periphery of the small diameter portion 2a of the rod 2. When the first piston split body 31 and the second piston split body 32 are centered and the first piston split body 31 is placed axially on the second piston split body 32, the first ports 31b of the first piston split body 31 and the annular groove 32b of the second piston split body 32 are arranged to face each other.

The first piston divided body 31 and the second piston divided body 32 thus constructed are used by stacking them in the axial direction with the divided surfaces A1 and A2 facing each other. Then, after inserting the small diameter portion 2a of the rod 2 into the inner circumference of the first piston divided body 31, the second piston divided body 32 is screwed into the screw portion 2b formed on the outer circumference of the small diameter portion 2a of the rod 2. Then, the first piston divided body 31 is sandwiched between the first step portion 2c of the rod 2 and the second piston divided body 32 and fixed to the rod 2. Furthermore, a piston nut 15 is screwed into the tip side of the screw portion 2b from the second piston divided body 32. When the piston nut 15 is screwed into the screw portion 2b of the rod 2 in this way, the second piston divided body 32 and the piston nut 15 form a double nut, which prevents the second piston divided body 32 from loosening and prevents the piston 3 from falling off the rod 2. The piston 3 may be fixed to the rod 2 only by the piston nut 15 without providing a threaded groove on the inner circumference of the second piston division 32. The first piston division 31 and the second piston division 32 fixed to the rod 2 in this way are integrally held on the outer circumference of the small diameter portion 2a of the rod 2 and function together as the piston 3.

When the first piston division 31 and the second piston division 32 are stacked, the first port 31b and the annular groove 32b face each other, and the first port 31b and the second port 32c communicate with each other to form a passage 3a that communicates between the expansion side chamber R1 and the compression side chamber R2.

Furthermore, when the first piston section 31 and the second piston section 32 are stacked, the annular recess 31a provided on the outer periphery of the first piston section 31 faces the dividing surface A2 of the second piston section 32 to form an annular second seal groove surrounding the outer periphery of the piston 3.

The second seal groove formed by the annular recess 31a accommodates a seal member 4 that is annular and seals between the cylinder 1 and the piston 3. The seal member 4 is composed of a seal ring 4a that slides against the inner circumferential surface of the cylinder 1, and an O-ring 4b that is disposed on the inner circumferential side of the seal ring 4a.

The seal ring 4a is made of synthetic resin and is in sliding contact with the inner circumferential surface of the cylinder 1, preventing hydraulic oil from passing between the seal ring 4a and the cylinder 1, and is self-lubricating so as not to impede the smooth movement of the piston 3. The O-ring 4b is in close contact with the inner circumferential surface of the seal ring 4a and the bottom surface of the annular recess 31a of the piston 3, closing the gap between the seal ring 4a and the piston 3 and preventing hydraulic oil from passing through the annular recess 31a. Thus, in the shock absorber D of this embodiment, the seal member 4 is composed of the seal ring 4a and the O-ring 4b, but may be composed of a single part.

To attach the seal member 4 to the outer periphery of the piston 3, the seal member 4 is placed in the annular recess 31a from the split surface A1 side of the first piston split body 31 before the first piston split body 31 and the second piston split body 32 are stacked and integrated. Since the annular recess 31a is open on the split surface A1 side of the first piston split body 31, there is no need to expand the diameter of the seal member 4 to attach it to the annular recess 31a, and the seal member 4 can be attached to the annular recess 31a without applying any load to the seal member 4.

In this way, after the seal member 4 is attached to the first piston segment 31, the first piston segment 31 is stacked on the second piston segment 32 to form the piston 3.

In addition, an annular piston ring 5 is fitted in the first seal groove 32a provided on the outer periphery of the second piston segment 32, sliding against the inner periphery of the cylinder 1 to guide the axial movement of the piston 3.

The piston 3 thus constructed is mounted on the outer periphery of the small diameter portion 2a of the rod 2, as described above. Specifically, the coil spring 16, the annular valve V, and the piston 3 are assembled in this order to the tip of the rod 2. As described above, the piston 3 is fixed to the outer periphery of the small diameter portion 2a of the rod 2 with the first piston divided body 31 and the second piston divided body 32 in close contact with each other's divided surfaces A1 and A2. The valve V is stacked on the extension side chamber end, which is the upper end of the piston 3 as a partition member in FIG. 1. As described above, the inner peripheral valve seat 31c, the outer peripheral valve seat 31d, and the intermediate valve seat 31e are provided on the end of the piston 3 facing the valve V. Therefore, the inner peripheral valve seat 31c, the outer peripheral valve seat 31d, and the intermediate valve seat 31e are all provided protruding toward the valve V side from the end of the piston 3 as a partition member facing the valve V. In addition, in the shock absorber D of this embodiment, the inverse split surface B1 of the first piston split body 31 of the piston 3 is the end facing the valve V.

The valve V is made of spring steel such as high carbon steel, alloy steel, stainless steel, etc. Spring steel has excellent elasticity and fatigue resistance. The valve V is annular and faces the inner valve seat 31c and the outer valve seat 31d of the first piston divided body 31 in the axial direction, and is fitted to the outer periphery between the first step 2c and the second step 2d of the rod 2 so as to be freely movable in the axial direction. In other words, the valve V has an outer diameter larger than the outer diameter of the outer valve seat 31d and an inner diameter smaller than the outer diameter of the inner valve seat 31c, and when it is in contact with the piston 3, it is seated on the inner valve seat 31c and the outer valve seat 31d. In this way, when the valve V is in contact with the piston 3, the inner peripheral surface side of the valve V is seated on the inner valve seat 31c, and the outer peripheral surface side of the valve V is seated on the outer valve seat 31d.

More specifically, the valve V in the shock absorber D of this embodiment is an annular plate with an inner diameter of about 20 mm, an outer diameter of about 40 mm, and a thickness of about 1.2 mm to 2.0 mm, and has high bending rigidity. Therefore, a very large force is required to bend the middle part of the valve V while supporting the inside and outside.

The valve V can move toward and away from the piston 3 in the axial direction, and closes the passage 3a when seated on the inner valve seat 31c and outer valve seat 31d of the first piston division 31 of the piston 3, and opens the passage 3a when the valve V moves away from the piston 3. When the valve V abuts against the second step 2d, it is restricted from moving further to the left in FIG. 1, and the maximum lift amount at which the valve V moves away from the piston 3 is set by the installation position of the second step 2d. A coil spring 16 is interposed between the third step 2e and the valve V, and biases the valve V so that it abuts against the piston 3.

Therefore, in the shock absorber D of this embodiment, the valve V is biased by the coil spring 16 from the rear side, i.e., the side opposite the piston. When the pressure in the expansion side chamber R1 is higher than the pressure in the contraction side chamber R2, the valve V seats on the inner valve seat 31c and the outer valve seat 31d of the piston 3 to block the passage 3a. On the other hand, when the pressure in the contraction side chamber R2 becomes higher than the pressure in the expansion side chamber R1 and the force of the pressure in the contraction side chamber R2 acting on the piston 3 side, which is the front side, through the passage 3a exceeds the biasing force of the coil spring 16, the valve V separates from the piston 3 to open the passage 3a. In this way, in the shock absorber D of this embodiment, the valve V constitutes a check valve that allows only the flow of hydraulic oil from the contraction side chamber R2 to the expansion side chamber R1 through the passage 3a, and seats the valve V on the inner valve seat 31c and the outer valve seat 31d to block the passage 3a against the flow of hydraulic oil from the expansion side chamber R1 to the contraction side chamber R2.

Even if the pressure in the expansion side chamber R1 acting on the rear side of the valve V becomes higher than the pressure in the compression side chamber R2 acting on the front side, if the pressure difference between the two is small, the middle part does not bend much. However, if the pressure inside the cylinder 1 is increased to obtain a large damping force, the pressure in the expansion side chamber R1 acting on the valve V increases, and the middle part also bends.

When the valve V receives high pressure from the expansion-side chamber R1 in this way and bends its middle portion, the middle portion abuts against the middle valve seat 31e, supporting the front side of the valve V and preventing the valve V from bending any further. Increasing the force bending the middle portion of the valve V increases the amount of bending, and eventually the valve V yields and undergoes plastic deformation. The middle valve seat 31e abuts against the middle portion of the valve V before the amount of bending of the valve V reaches the amount of bending at which it becomes plastically deformed, preventing the valve V from bending plastically.

By providing the intermediate valve seat 31e between the inner valve seat 31c and the outer valve seat 31d in this way, the intermediate valve seat 31e can support the middle part of the valve V, preventing the valve V from being significantly deformed and plastically deformed.

In addition, in the shock absorber D of this embodiment, the intermediate valve seat 31e protrudes from the end face of the piston 3 as a partition member lower than the protruding heights of both the inner valve seat 31c and the outer valve seat 31d. Specifically, the end face W of the intermediate valve seat 31e is located lower than the imaginary plane Z including the end face X of the inner valve seat 31c and the end face Y of the outer valve seat 31d. Therefore, in the shock absorber D of this embodiment, when the valve V is placed on the piston 3 and seated on the inner valve seat 31c and the outer valve seat 31d in an unloaded state without applying any force to the valve V, the intermediate part between the inner and outer sides of the valve V does not abut against the intermediate valve seat 31e.

The end face W of the intermediate valve seat 31e is arranged at a position that can limit the amount of deflection of the intermediate part of the valve V relative to the imaginary plane Z so that the deflection of the intermediate part of the valve V falls within the range of elastic deformation. The amount of deflection that causes the unsupported intermediate part of the valve V to bend toward the piston 3 side and to plastically deform beyond the range of elastic deformation when the valve V is supported by the inner peripheral valve seat 31c and the outer peripheral valve seat 31d varies depending on the inner and outer diameters and plate thickness and material of the valve V. However, if the distance between the end face W of the intermediate valve seat 31e and the imaginary plane Z is shorter than the amount of deflection Lmax of the part of the valve V that faces the intermediate valve seat 31e in the axial direction when the valve V plastically deforms just beyond the range of elastic deformation, the plastic deformation of the valve V can be prevented. Therefore, if the axial distance between the end face W of the intermediate valve seat 31e and the imaginary plane Z is L1, the position of the intermediate valve seat 31e can be determined so that the distance L1 satisfies 0≦L1<Lmax. The amount of deflection caused by the plastic deformation of the valve V varies depending on the inner and outer diameters, plate thickness, and material of the valve V, so the amount of deflection Lmax can be calculated according to the specifications of the valve V and the position of the end face W of the intermediate valve seat 31e can be determined. In addition, the end face W of the intermediate valve seat 31e may be in contact with the imaginary plane Z as long as it does not exceed the imaginary plane Z toward the anti-piston side. In this case, the valve V will also abut against the intermediate valve seat 31e when seated on the inner valve seat 31c and the outer valve seat 31d, so in this case, the middle part of the valve V can also be supported to restrict deflection.

The rod guide 10 is provided with a discharge passage 10a that connects the extension side chamber R1 to the reservoir R. The discharge passage 10a is provided with a damping valve 10b that provides resistance to the flow of hydraulic oil passing through while allowing only the flow of hydraulic oil from the extension side chamber R1 to the reservoir R and prevents the flow in the opposite direction, and the discharge passage 10a is set as a one-way passage that allows only the flow of hydraulic oil from the extension side chamber R1 to the reservoir R.

The valve case 11 is also provided with a suction passage 11a that connects the reservoir R and the pressure side chamber R2. The suction passage 11a is provided with a suction check valve 11b that allows hydraulic oil to flow only from the reservoir R to the pressure side chamber R2 and prevents it from flowing in the opposite direction, so that the suction passage 11a is set as a one-way passage that allows hydraulic oil to flow only from the reservoir R to the pressure side chamber R2.

The shock absorber D is configured as described above, and its operation will be described below. First, the operation will be described when the rod 2 moves to the left in FIG. 1 relative to the cylinder 1 and the shock absorber D extends. When the shock absorber D extends, the piston 3 moves to the left in FIG. 1 relative to the cylinder 1, so that the expansion side chamber R1 is compressed and the compression side chamber R2 is expanded.

In this case, the valve V is seated on the inner valve seat 31c and the outer valve seat 31d, blocking the passage 3a provided in the piston 3, and the hydraulic oil in the expansion side chamber R1 is discharged to the reservoir R through the damping valve 10b in the discharge passage 10a. The damping valve 10b provides resistance to this movement of hydraulic oil, so the pressure in the expansion side chamber R1 rises and becomes higher than the pressure in the reservoir R. In addition, the volume of the compression side chamber R2 expands due to the movement of the piston 3, causing a shortage of hydraulic oil, but the suction check valve 11b opens and supplies this shortage of hydraulic oil from the reservoir R to the compression side chamber R2 through the suction passage 11a. Therefore, the pressure in the compression side chamber R2 becomes almost equal to the pressure in the reservoir R.

In this way, when shock absorber D is extended, the pressure in extension chamber R1 acting on the side of piston 3 becomes higher than the pressure in compression chamber R2 acting on the side of compression chamber R2, and shock absorber D generates an extension damping force that impedes the extension operation. In addition, hydraulic oil equivalent to the volume of the rod 2 exiting from cylinder 1 is supplied from reservoir R to compression chamber R2, compensating for the volume of rod 2 exiting from cylinder 1.

Next, we will explain the operation when the rod 2 moves to the right in FIG. 1 relative to the cylinder 1 and the shock absorber D contracts. When the shock absorber D contracts, the piston 3 moves to the right in FIG. 1 relative to the cylinder 1, compressing the compression side chamber R2 and expanding the expansion side chamber R1.

In this case, the entire valve V moves away from the piston 3 and separates from the inner valve seat 31c and the outer valve seat 31d, opening the passage 3a provided in the piston 3, and the suction check valve 11b closes to block the suction passage 11a, so that the hydraulic oil in the compression side chamber R2 moves through the passage 3a to the extension side chamber R1. Also, when the shock absorber D is contracting, the rod 2 enters the cylinder 1, so that the hydraulic oil in the cylinder 1 becomes excessive by the volume of the rod 2 entering the cylinder 1. This excess hydraulic oil in the cylinder 1 passes through the damping valve 10b in the discharge passage 10a and is discharged to the reservoir R. Since the damping valve 10b provides resistance to such movement of the hydraulic oil, the pressure in the extension side chamber R1 rises and becomes higher than the pressure in the reservoir R. Also, since the compression side chamber R2 is in a state of communication with the extension side chamber R1 through the passage 3a, the pressure in the compression side chamber R2 and the pressure in the extension side chamber R1 become approximately equal.

In this way, when shock absorber D contracts, the pressure in the extension side chamber R1 acting on the side of the extension side chamber R1 of the piston 3 and the pressure in the compression side chamber R2 acting on the side of the compression side chamber R2 of the piston 3 are approximately equal, but since the pressure-receiving area receiving the pressure in the compression side chamber R2 is larger than the pressure-receiving area receiving the pressure in the extension side chamber R1 of the piston 3, shock absorber D generates a compression side damping force that impedes the contraction operation. In addition, the hydraulic oil equivalent to the volume of the rod 2 entering the cylinder 1 is discharged from the cylinder 1 to the reservoir R, compensating for the volume of the rod 2 entering the cylinder 1. In this way, shock absorber D generates a damping force when it expands or contracts, and damps the vibration of the vibration-damping target.

In this embodiment, the shock absorber D comprises an expandable body E having a cylinder 1 and a rod 2 inserted into the cylinder 1 so as to be freely movable in the axial direction; a piston (partition member) 3 which separates the expansion side chamber (fluid chamber) R1 and the compression side chamber (fluid chamber) R2 within the expandable body E and has a passage 3a which connects the expansion side chamber (fluid chamber) R1 and the compression side chamber (fluid chamber) R2 on the same circumference; and a valve V which is annular and can be moved axially toward and away from the piston (partition member) 3 and opens and closes the passage 3a. The piston (partition member) 3 has an intermediate valve seat 31e between an inner valve seat 31c on which the valve V is seated and removed, and an outer valve seat 31d. During the expansion operation of the shock absorber D, when the large pressure in the expansion-side chamber R1 acts on the back side of the valve V and the middle part of the valve V bends while the inner and outer peripheries of the valve V are supported by the inner valve seat 31c and the outer valve seat 31d, the middle valve seat 31e abuts against the front side of the middle part before the valve V undergoes plastic deformation, restricting further bending of the valve V. Therefore, when the pressure in the expansion-side chamber R1 decreases, the valve V returns to its original flat annular plate shape by its restoring force without plastic deformation, so that during the expansion operation of the shock absorber D, it can seat on the inner valve seat 31c and the outer valve seat 31d and block the passage 3a. Then, the shock absorber D can exert the damping force as designed, without the valve V leaving the passage 3a open.

As a result, even if a large axial force acts on the valve V by increasing the pressure inside the cylinder 1 more than before when the shock absorber D expands or contracts, plastic deformation of the valve V can be prevented. Therefore, the shock absorber D of this embodiment can withstand high pressure inside the cylinder 1 and generate a high damping force.

In addition, the shock absorber D of this embodiment is configured so that the protruding height of the intermediate valve seat 31e is lower than the protruding height of the inner valve seat 31c and the outer valve seat 31d. According to the shock absorber D configured in this manner, since the protruding height of the intermediate valve seat 31e is lower than the protruding height of the inner valve seat 31c and the outer valve seat 31d, even if the flexural rigidity of the valve V is increased, the intermediate valve seat 31e does not prevent the valve V from seating on the inner valve seat 31c and the outer valve seat 31d. Therefore, according to the shock absorber D configured in this manner, since the intermediate valve seat 31e does not hinder the valve V from seating on the inner valve seat 31c and the outer valve seat 31d, it is possible to ensure smooth blocking of the passage 3a by the valve V while preventing plastic deformation of the valve V, and since the flexural rigidity of the valve V can be increased, a higher damping force can be generated. In addition, in order to prevent the intermediate valve seat 31e from interfering with the seating of the valve V on the inner valve seat 31c and the outer valve seat 31d, the protruding height of the intermediate valve seat 31e may be the same as the protruding heights of the inner valve seat 31c and the outer valve seat 31d. In other words, the end face W of the intermediate valve seat 31e may be disposed in a position in contact with an imaginary plane Z including the end face X of the inner valve seat 31c and the end face Y of the outer valve seat 31d.

Furthermore, since the intermediate valve seat 31e is only required to prevent plastic deformation of the valve V, it may be configured to partially support the intermediate portion between the opposing portions of the inner valve seat 31c and the outer valve seat 31d of the valve V by separating them in the circumferential direction.

In addition, since the intermediate valve seat 31e in the shock absorber D of this embodiment has a passage 3a formed therein, the intermediate valve seat 31e is provided around the entire circumference of the piston 3 except for the opening of the passage 3a. When the intermediate valve seat 31e is provided between the passages 3a in this manner, the intermediate valve seat 31e supports the middle portion of the valve V evenly in the circumferential direction, so that the deflection of the middle portion of the valve V is evenly suppressed in the circumferential direction, and fatigue of the valve V can be suppressed.

When shock absorber D expands, valve V closes passage 3a in piston 3, and when shock absorber D contracts, valve V moves away from piston 3 to open passage 3a. As shock absorber D repeatedly expands and contracts, valve V repeatedly collides with first piston divided body 31. The first piston divided body 31 that valve V abuts against is required to be wear-resistant, and materials with excellent wear resistance may be disadvantageous in terms of strength. If the entire piston is made of a material with excellent wear resistance, the strength of the piston may be insufficient when the cylinder 1 is pressurized when the shock absorber expands and contracts to generate a high damping force.

However, in the shock absorber D of this embodiment, the piston 3 includes a first piston divided body 31 and a second piston divided body 32 that are divided in the axial direction, and the first piston divided body 31 and the second piston divided body 32 that the valve V collides with are made of different materials, and the second piston divided body 32 has a higher strength than the first piston divided body 31. Therefore, even if the pressure inside the cylinder 1 is increased to a higher pressure than in the past and a large axial force acts on the piston 3 during the expansion and contraction of the shock absorber D, the second piston divided body 32, which has a higher strength, supports the first piston divided body 31, which has a lower strength, in the axial direction, so that deformation of the first piston divided body 31 can be prevented. In addition, since the deformation of the first piston divided body 31, which has a lower strength, can be supported by the second piston divided body 32, which has a higher strength, deformation of the first piston divided body 31 can be prevented even if the flow passage area of the passage 3a is increased in order to use the shock absorber D in an application in which the shock absorber D expands and contracts at high speed. Therefore, according to the shock absorber D of this embodiment, it is possible to further increase the pressure inside the cylinder 1 and generate a higher damping force.

In addition, in the shock absorber D of this embodiment, the second piston segment 32 is screwed onto the threaded portion 2b of the rod 2, and the first piston segment 31 is sandwiched between the second piston segment 32 and the first step portion 2c of the rod 2. This means that the force acting on the piston 3 due to the pressure in the cylinder 1 is transmitted via the second piston segment 32, which has high strength, and it is possible to prevent excessive shear force from acting on the inner circumference of the first piston segment 31. Therefore, with the shock absorber D configured in this way, the first piston segment 31, which is inferior in strength, can be further protected.

In addition, in the shock absorber D of this embodiment, the valve V is made of a material with higher strength than the first piston division 31, so deformation of the valve V due to high pressure inside the cylinder 1 can be prevented.

It is advisable to form the first piston split body 31 from cast iron and the valve V from spring steel. Cast iron has excellent wear resistance and can withstand wear caused by repeated collisions of the valve V, making it the optimal material for the first piston split body 31, while spring steel has excellent elasticity and fatigue resistance limits, making it the optimal material for the valve V, which receives high pressure from the back side, which is the side opposite the piston, from the extension side chamber R1 and repeatedly collides with the piston 3. As described above, according to the shock absorber D in which the first piston split body 31 is formed from cast iron and the valve V is formed from spring steel, it is possible to reduce deterioration due to wear of the first piston split body 31 and to reduce deterioration such as deformation and fatigue of the valve V.

Furthermore, in the shock absorber D of this embodiment, the first piston divided body 31 has a first port 31b that leads from the opposite division surface B1 side to the division surface A1 side, the second piston divided body 32 has a second port 32c that leads from the opposite division surface B2 side to the division surface A2 side, and has an annular groove 32b that communicates with both the first port 31b and the second port 32c formed along the circumferential direction on the division surface A2 side of the second piston divided body 32. According to the shock absorber D configured in this way, the first port 31b and the second port 32c are communicated through the annular groove 32b even if the first piston divided body 31 and the second piston divided body 32 are not aligned in the circumferential direction when stacking them, so that the shock absorber D can be easily assembled when the passage 3a is provided in the piston 3. The annular groove may be provided on the division surface A1 of the first piston divided body 31 instead of the second piston divided body 32.

The shock absorber D of this embodiment includes a reservoir R for storing hydraulic oil (fluid), a discharge passage 10a communicating the extension-side chamber R1 with the reservoir R, a damping valve 10b provided in the discharge passage 10a for allowing only the flow of the hydraulic oil (fluid) from the extension-side chamber R1 to the reservoir R and for providing resistance to the flow of the hydraulic oil (fluid), a suction passage 11a communicating the reservoir R with the compression-side chamber R2, and a suction check valve 11b provided in the suction passage 11a for allowing only the flow of the hydraulic oil (fluid) from the reservoir R to the compression-side chamber R2. The valve V is a check valve for allowing only the flow of the hydraulic oil (fluid) from the compression-side chamber R2 to the extension-side chamber R1 through the passage 3a. The shock absorber D configured in this manner is set as a uniflow type shock absorber in which, when the shock absorber D performs an expansion/contraction operation, the hydraulic oil (fluid) is returned in one direction to the reservoir R via the reservoir R, the compression side chamber R2, and the expansion side chamber R1 in this order. In the shock absorber D configured as a uniflow type, the entire amount of hydraulic oil (fluid) moving from the compression side chamber R2, which contracts during contraction, moves to the expansion side chamber R1 via the passage 3a. Therefore, the amount of hydraulic oil (fluid amount) passing through the passage 3a in the shock absorber D configured as a uniflow type is greater than the amount of hydraulic oil (fluid amount) passing through the passage provided in the piston of the shock absorber configured as a biflow type in which the hydraulic oil (fluid) moves between the expansion side chamber and the compression side chamber without passing through the reservoir during expansion/contraction. Thus, in the shock absorber D configured as a uniflow type, there is a high demand for a larger flow passage area of the passage 3a provided in the piston 3.

Therefore, a structure that includes a first piston segment 31 on which the valve V seats and unseats the piston 3, and a second piston segment 32 with high strength is optimal for a uniflow type shock absorber D that is forced to allow more hydraulic oil (fluid) to pass through due to the high pressure inside the cylinder 1, improving the practicality of the uniflow type shock absorber D.

The piston 3 also includes a first piston split body 31 that is divided in the axial direction and a second piston split body 32 that faces the first piston split body 31 in the axial direction, and the seal member 4 is housed in an annular recess 31a that is provided on the outer periphery of the first piston split body 31 on the split surface A1 side.

In the shock absorber D configured in this manner, the seal member 4 can be accommodated in the annular recess 31a without expanding the diameter before the first piston segment 31 and the second piston segment 32 are stacked, and when the first piston segment 31 and the second piston segment 32 are stacked, the split surface A2 of the second piston segment 32 faces the annular recess 31a, forming a second seal groove on the outer periphery of the piston 3. Then, even if the seal member 4 accommodated in the annular recess 31a tries to move in the axial direction relative to the piston 3, it is sandwiched between the first piston segment 31 and the second piston segment 32 in the axial direction and cannot move, so it does not come out of the annular recess 31a.

In the shock absorber D of this embodiment, when the seal member 4 is attached to the piston 3, the seal member 4 is first accommodated in the annular recess 31a of the first piston division 31 without applying any load, and then the seal member 4 can be attached to the piston 3 simply by stacking the first piston division 31 and the second piston division 32. In addition, in the shock absorber D of this embodiment, when the seal member 4 is removed from the piston 3, the seal member 4 can be easily removed from within the annular recess 31a of the first piston division 31 after separating the first piston division 31 and the second piston division 32.

Therefore, according to the shock absorber D of this embodiment, there is no need to apply excessive force to expand the diameter of the seal member 4, and the seal member 4 can be easily attached to the outer periphery of the piston 3. Therefore, even if the strength of the seal member 4 is increased as the pressure inside the cylinder 1 increases to generate a large damping force in the shock absorber D, and it becomes difficult to expand the diameter of the seal member 4, there is no need to expand the diameter of the seal member 4 when attaching it to the piston 3, so the seal member 4 can be easily attached and detached to the piston 3. Therefore, according to the shock absorber D of this embodiment, even if the strength of the seal member 4 is increased, the seal member 4 can be easily attached and detached to the piston 3.

In the shock absorber D of this embodiment, the annular recess 31a that accommodates the seal member 4 is provided on the outer periphery of the split surface A1 side of the first piston split body 31, but the annular recess 31a of the first piston split body 31 may be eliminated and an annular recess that accommodates the seal member 4 may be provided on the outer periphery of the split surface A2 side of the second piston split body 32. Even in this case, the seal member 4 can be assembled to the second piston split body 32 without having to expand the diameter before stacking the first piston split body 31 and the second piston split body 32, so that the seal member 4 can be easily attached and detached to the piston 3 even if the strength of the seal member 4 is increased.

Furthermore, annular recesses facing each other in the axial direction may be provided on both the outer periphery of the split surface A1 side of the first piston divided body 31 and the outer periphery of the split surface A2 side of the second piston divided body 32, so that when the first piston divided body 31 and the second piston divided body 32 are stacked, a single second seal groove that accommodates the seal member 4 may be formed on the outer periphery of the piston 3 by these annular recesses. Even in this way, the seal member 4 can be assembled to the outer periphery of the piston 3 without having to be enlarged when stacking the first piston divided body 31 and the second piston divided body 32, so that the seal member 4 can be easily attached and detached to the piston 3 even if the strength of the seal member 4 is increased.

The first piston split body 31 and the second piston split body 32 can have any shape as long as they can function as a piston 3 when stacked and assembled in the axial direction, and the split surfaces A1 and A2 may have irregularities.

As described above, in this embodiment, the piston 3 is composed of the first piston segment 31 and the second piston segment 32, which allows for even higher pressure inside the cylinder 1. However, the piston 3 may not be composed of multiple segments, but may be composed of a single, inseparable part. Furthermore, the piston 3 may be composed of three or more piston segments, including the first piston segment 31 and the second piston segment 32.

Furthermore, as mentioned above, in order to suppress fatigue of the valve V, it is preferable that the entire circumference of the middle part of the valve V can be supported by the middle valve seat 31e as widely as possible. For this reason, as in the piston 41 of the shock absorber of the first modified example of one embodiment shown in FIG. 5, an annular middle valve seat 41c may be provided between the inner valve seat 41a and the outer valve seat 41b, and passages 41d, 41e may be provided between the inner valve seat 41a and the middle valve seat 41c and between the outer valve seat 41b and the middle valve seat 41c, thereby ensuring the flow area and providing wide support over the entire circumference of the middle part of the valve V.

The shock absorber configured in this way can seamlessly support the entire circumference of the middle part of the valve V, further suppressing fatigue caused by bending of the valve V, and since the passages 41d, 41e are provided between the inner valve seat 41a and the middle valve seat 41c, and between the outer valve seat 41b and the middle valve seat 41c, the flow area can be secured, so that the shock absorber D can be used in applications where it expands and contracts at high speed without any problems.

In the shock absorber D of the embodiment described above, the piston 3 is used as the partition member, but the valve case 11 may be used as the partition member instead of the piston 3, and the valve case 11 may be provided with an inner peripheral valve seat, an outer peripheral valve seat, and an intermediate valve seat, or the piston 3 and the valve case 11 may both be used as partition members, and the inner peripheral valve seat, the outer peripheral valve seat, and an intermediate valve seat may be provided on them. In this case, the compression side chamber R2 and the reservoir R become the fluid chambers.

Although the shock absorber D is a uniflow type shock absorber, it may be a biflow type shock absorber in which hydraulic oil flows between the expansion side chamber R1 and the compression side chamber R2 during expansion and contraction. The exhaust passage 10a, damping valve 10b, and suction passage 11a may be installed in locations other than those shown in the figure. The object of vibration damping by the shock absorber D is not limited to railway vehicles and structures, but may be a saddle-ride vehicle, automobile, other machinery, etc.

Although the preferred embodiment of the present invention has been described in detail above, modifications, variations, and changes are possible without departing from the scope of the claims.

1: Cylinder, 2: Rod, 3, 41: Piston (partition member), 3a, 41d, 41e: Passage, 31c, 41a: Inner valve seat, 31d, 41b: Outer valve seat, 31e, 41c: Intermediate valve seat, B1: Inverse split surface (end facing the valve), D: Shock absorber, E: Expandable body, R: Reservoir (fluid chamber), R1: Expansion side chamber (fluid chamber), R2: Compression side chamber (fluid chamber), V: Valve, W: End surface of intermediate valve seat, X: End surface of inner valve seat, Y: End surface of outer valve seat, Z: Virtual plane

Claims (5)

an expandable body having a cylinder and a rod inserted into the cylinder so as to be freely movable in an axial direction;
a partition member that separates two fluid chambers within the expandable body and has a passage that connects the fluid chambers to each other;
a valve that is annular and can be moved toward and away from the partition member in the axial direction to open and close the passage,
the partition member has an annular inner peripheral valve seat that protrudes in the axial direction from an end portion facing the valve and seats on an inner peripheral surface side of the valve, an annular outer peripheral valve seat that protrudes in the axial direction from an end portion facing the valve and seats on an outer peripheral surface side of the valve, and an intermediate valve seat that protrudes in the axial direction from an end portion facing the valve,
the passage and the intermediate valve seat are formed between the inner valve seat and the outer valve seat ;
the intermediate valve seat is formed annularly in a circumferential direction between the inner valve seat and the outer valve seat of the partition member,
A plurality of the passages are provided between the inner peripheral valve seat and the intermediate valve seat and between the intermediate valve seat and the outer peripheral valve seat.
A shock absorber characterized by: an expandable body having a cylinder and a rod inserted into the cylinder so as to be freely movable in an axial direction;
a partition member that separates two fluid chambers within the expandable body and has a passage that connects the fluid chambers to each other;
a valve that is annular and can be moved toward and away from the partition member in the axial direction to open and close the passage,
the partition member has an annular inner peripheral valve seat that protrudes in the axial direction from an end portion facing the valve and seats on an inner peripheral surface side of the valve, an annular outer peripheral valve seat that protrudes in the axial direction from an end portion facing the valve and seats on an outer peripheral surface side of the valve, and an intermediate valve seat that protrudes in the axial direction from an end portion facing the valve,
the passage and the intermediate valve seat are formed between the inner circumferential valve seat and the outer circumferential valve seat;
A shock absorber , wherein a protruding height of the intermediate valve seat is lower than protruding heights of the inner peripheral valve seat and the outer peripheral valve seat. an expandable body having a cylinder and a rod inserted into the cylinder so as to be freely movable in an axial direction;
a partition member that separates two fluid chambers within the expandable body and has a passage that connects the fluid chambers to each other;
a valve that is annular and can be moved toward and away from the partition member in the axial direction to open and close the passage,
the partition member has an annular inner peripheral valve seat that protrudes in the axial direction from an end portion facing the valve and seats on an inner peripheral surface side of the valve, an annular outer peripheral valve seat that protrudes in the axial direction from an end portion facing the valve and seats on an outer peripheral surface side of the valve, and an intermediate valve seat that protrudes in the axial direction from an end portion facing the valve,
the passage and the intermediate valve seat are formed between the inner valve seat and the outer valve seat;
The intermediate valve seat is provided around an entire periphery of the partition member except for an opening of the passage . The passages are provided in a plurality on the same circumference in the partition member,
The shock absorber according to claim 2 , wherein the intermediate valve seat is provided between the passages. The partition member is a piston that is movably inserted into the cylinder and divides the inside of the cylinder into an expansion-side chamber and a compression-side chamber, which are fluid chambers,
The passage communicates the expansion-side chamber and the compression-side chamber,
A reservoir for storing a fluid;
a discharge passage communicating the expansion-side chamber with the reservoir;
a damping valve provided in the discharge passage to allow only a flow of the fluid from the expansion-side chamber toward the reservoir and to provide resistance to the flow of the fluid;
a suction passage communicating between the reservoir and the pressure-side chamber;
a suction check valve provided in the suction passage to allow only a flow of the fluid from the reservoir to the compression side chamber,
The shock absorber according to any one of claims 1 to 4, wherein the valve is a check valve that allows the fluid to flow through the passage only in a direction from the compression-side chamber to the expansion-side chamber.

Images