Buffer

Abstract

The buffer includes: a cylinder; a rod that is movably inserted into the cylinder; a piston that is inserted into the cylinder, divides the inside of the cylinder into an extension-side chamber and a compression-side chamber, and has a passage for communicating the extension-side chamber and the compression-side chamber; and a valve for opening and closing the passage; the piston has a first piston segment that is axially divided and disengages or seats the valve body of the valve, and a second piston segment that is axially opposed to the first piston segment, and the second piston segment is formed of a material having a higher strength than the first piston segment.

Description

Technical Field

[0001] The present invention relates to a buffer. Background Art

[0002] For example, as disclosed in JP2015-224780A, a buffer includes: 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 that partition the inside of the cylinder by the piston and are filled with hydraulic oil; an outer cylinder that covers the outer periphery of the cylinder and forms a reservoir for storing hydraulic oil between the cylinders; a damping passage that only allows hydraulic oil to flow from the extension side chamber to the reservoir and applies resistance to the flow of the hydraulic oil flowing through; a rectifying passage provided on the piston that only allows hydraulic oil to flow from the compression side chamber to the extension side chamber; and a suction passage that only allows hydraulic oil to flow from the reservoir to the compression side chamber.

[0003] The buffer configured in this way has check valves on the rectifying passage and the suction passage, and by these check valves, it is set to a single-phase type in which hydraulic oil sequentially flows through the reservoir, the compression side chamber, the extension side chamber, and then reaches the reservoir during the telescopic movement. Moreover, the buffer applies resistance to the flow of the hydraulic oil discharged from the inside of the cylinder to the reservoir during the telescopic movement and generates a damping force that hinders the telescopic movement.

[0004] The check valve provided on the piston includes: an annular valve body that seats or unseats on a valve seat surrounding the outlet end of the rectifying passage of the piston; and a spring that biases the annular valve body toward the piston, and when the entire annular valve body receives pressure from the compression side chamber and moves away from the piston, the rectifying passage is opened.

[0005] Since the annular valve body in the check valve repeatedly moves away from and contacts the piston due to the telescopic movement of the buffer, it is formed of quenched high-carbon steel or the like with excellent elastic limit and fatigue resistance limit. On the other hand, from the viewpoints of formability and wear resistance, the piston that repeatedly collides with the annular valve body is formed of cast iron with a carbon content of 2.14% to 6.67%.

[0006] When the piston is formed of cast iron in this way, even if it repeatedly collides with the annular valve body, the wear of the piston is less, and the buffer can be maintained and function for a long time. Summary of the Invention

[0007] For example, taking a railway vehicle or a structure as a vibration damping object, the buffer is provided between the body of the railway vehicle and the bogie, or between the bodies of adjacent railway vehicles, between the elastically supported structure and the ground, or between the columns and beams of the structure, etc., and is used for the purpose of attenuating the vibration of the vibration damping object.

[0008] As described above, when the object to be vibration-damped by the buffer is a heavy object such as a railway vehicle or a structure, in order to suppress the vibration of the object to be vibration-damped, it is necessary for the buffer to generate a large damping force. In order to meet such a requirement and increase the damping force of the buffer, it is only necessary to increase the difference between the pressure in the extension-side chamber and the pressure in the compression-side chamber. However, in this case, a large pressure is applied to the piston due to the high pressure in the cylinder.

[0009] As described above, the piston is formed of cast iron. Although the wear resistance of cast iron is excellent, its strength is low, and it may not be able to withstand the action of high pressure. In addition, the high pressure in the cylinder is generated when the buffer expands and contracts at high speed. We hope that more hydraulic oil can pass through the passage provided in the piston. However, as described above, since the piston is formed of cast iron, when the cross-sectional area of the passage is increased, the strength decreases, and it is also difficult to ensure a large cross-sectional area of the passage. Therefore, in the conventional buffer, there is a problem that it is difficult to generate a high damping force due to the high pressure in the cylinder.

[0010] Therefore, an object of the present invention is to provide a buffer that can withstand the high pressure in the cylinder and generate a high damping force.

[0011] To solve the above problems, the buffer of the present invention includes: a cylinder; a rod that is movably inserted into the cylinder; a piston that is inserted into the cylinder and divides the inside of the cylinder into an extension-side chamber and a compression-side chamber, and has a passage for communicating the extension-side chamber and the compression-side chamber; and a valve for opening and closing the passage; the piston has a first piston divided body that is axially divided and separates or seats the valve body of the valve, and a second piston divided body that is axially divided and opposed to the first piston divided body, and the second piston divided body is formed of a material having a higher strength than the first piston divided body. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a longitudinal sectional view of the buffer in one embodiment.

[0013] Figure 2 is an enlarged sectional view of the piston portion of the buffer in one embodiment.

[0014] Figure 3 is a plan view of the second piston divided body of the buffer in one embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] Hereinafter, the present invention will be described based on the embodiments shown in the drawings. As Figure 1As shown, a shock absorber D in one embodiment includes: a cylinder 1; a rod 2 which is movably inserted into the cylinder 1; a piston 3 which is inserted into the cylinder 1 and has a passage 3a for connecting the expansion side chamber R1 and the compression side chamber R2 while dividing the cylinder 1 into an expansion side chamber R1 and a compression side chamber R2; and a valve V for opening and closing the passage 3a. In addition, in the case of the shock absorber D, for example, it is installed between a car body and a bogie in a railway vehicle (not shown) and used to suppress the vibration of the car body and the bogie.

[0016] Next, each part of the buffer D is described in detail. Figure 1 As shown, in cylinder 1 Figure 1 The left end of the cylinder 1 is embedded with an annular rod guide 10. Figure 1 The right end is closed by the valve housing 11. In addition, the cylinder 1 is accommodated together with the valve housing 11. Figure 1 The right end of the cylinder 1 is sealed by a bottom cover 13 in the outer tube 12. A reservoir R is formed between the cylinder 1 and the outer tube 12. The reservoir R is annular and stores fluid such as hydraulic oil together with gas.

[0017] Outer cylinder 12 Figure 1 The opening at the middle left end is closed by the rod guide 10 mounted on the outer tube 12. Moreover, the cylinder 1 and the valve housing 11 are sandwiched by the rod guide 10 and the bottom cover 13 fixed to the outer tube 12 and are accommodated in the outer tube 12 and fixed relative to the outer tube 12.

[0018] The rod 2 is inserted into the cylinder 1 so as to be slidable through the rod guide 10 and is guided to move in the axial direction by the rod guide 10. The rod 2 includes a small diameter portion 2a provided at a position as Figure 1 The front end of the middle right end has a small outer diameter and a piston 3 is installed on the outer periphery; the threaded portion 2b is arranged on the outer periphery of the front end of the small diameter portion 2a; the first step portion 2c (refer to Figure 2 ), which is formed between the small diameter portion 2a and the small diameter portion 2a. Figure 1 The boundary between the positions on the left side; and the second step portion 2d (reference Figure 2 ) and the third step portion 2e (refer to Figure 2 ), which is arranged closer to the first step portion 2c Figure 1 Thus, in the shock absorber D of the present embodiment, the rod 2 has a shape in which the outer diameter is divided into three small diameters at the front end side.

[0019] The piston 3 is annular, mounted on the small diameter portion 2a of the rod 2, and is inserted into the cylinder 1 movably, dividing the cylinder 1 into an extension side chamber R1 and a compression side chamber R2 filled with a fluid such as hydraulic oil. In addition, the fluid may be a liquid such as water or an aqueous solution in addition to the hydraulic oil. In addition, a gas may be used as the fluid instead of the liquid.

[0020] In the present embodiment, the piston 3 is configured to include a first piston segment 31 and a second piston segment 32 that are axially divided. Both the first piston segment 31 and the second piston segment 32 are annular, and after overlapping axially, they become integrated to form the piston 3.

[0021] The first piston segment 31 is formed of a cast iron such as gray cast iron, ductile cast iron, malleable cast iron, alloy cast iron, or white cast iron. Cast iron is a ternary alloy of iron containing carbon in the range of 2.14 to 6.67% and silicon in the range of about 1 to 3%, and has excellent wear resistance. The first piston segment 31 includes: an annular recess 31a, which is circular and formed on the outer periphery on the side of the split surface A1 on the right end side in the axial direction and is opposite to the end on the side of the split surface A2 at the left end of the second piston segment 32; an annular groove 31b, which is formed circumferentially on the end on the side of the reverse split surface B1 at the left end; an annular valve seat 31c, which projects axially from the end on the side of the reverse split surface B1 and surrounds the groove 31b; and a plurality of first ports 31d, which open on the split surface A1 and communicate with the groove 31b. Figure 2 on the outer periphery on the side of the split surface A1 on the right end side in the axial direction and is opposite to the end on the side of the split surface A2 at the left end of the second piston segment 32; Figure 2 an annular groove 31b, which is formed circumferentially on the end on the side of the reverse split surface B1 at the left end; Figure 2 on the end on the side of the reverse split surface B1 at the left end; an annular valve seat 31c, which projects axially from the end on the side of the reverse split surface B1 and surrounds the groove 31b; and a plurality of first ports 31d, which open on the split surface A1 and communicate with the groove 31b.

[0022] The second piston segment 32 is formed of a carbon steel containing carbon in the range of 0.02 to 2.14%. Carbon steel has high strength, and the second piston segment 32 has a higher strength than the first piston segment 31. Moreover, as Figure 2 and Figure 3 shown, the second piston segment 32 includes: an annular groove 32a, which is circular and formed circumferentially on the outer periphery; an open groove 32b, which is formed circumferentially through the annular groove on the end on the side of the split surface A2 at the left end; and a plurality of second ports 32c, which open on the reverse split surface B2 and communicate with the open groove 32b; and has a threaded groove (not shown) on the inner periphery and is screwed with the threaded portion 2b of the rod 2. Figure 2 on the end on the side of the split surface A2 at the left end; and a plurality of second ports 32c, which open on the reverse split surface B2 and communicate with the open groove 32b; and has a threaded groove (not shown) on the inner periphery and is screwed with the threaded portion 2b of the rod 2.

[0023] The outer diameters of the first piston segment 31 and the second piston segment 32 are the same, and they have an inner diameter that can be mounted on the outer periphery of the small-diameter portion 2a of the rod 2. Moreover, when the centers of the first piston segment 31 and the second piston segment 32 are aligned and the first piston segment 31 is axially overlapped on the second piston segment 32, the respective first ports 31d of the first piston segment 31 and the open groove 32b of the second piston segment 32 are arranged to face each other.

[0024] The first piston segment 31 and the second piston segment 32 configured in this way are used after the dividing surfaces A1 and A2 face each other and overlap axially. Moreover, after the small-diameter portion 2a of the rod 2 is inserted into the inner circumference of the first piston segment 31, the second piston segment 32 is screwed onto the thread portion 2b formed on the outer circumference of the small-diameter portion 2a of the rod 2. Then, the first piston segment 31 is clamped by the first step portion 2c of the rod 2 and the second piston segment 32 and fixed to the rod 2. Further, a piston nut 15 is screwed on the front end side of the thread portion 2b closer to the second piston segment 32. In this way, when the piston nut 15 is screwed onto the thread portion 2b of the rod 2, a double nut is formed by the second piston segment 32 and the piston nut 15, preventing the loosening of the second piston segment 32 and preventing the piston 3 from falling off the rod 2. Additionally, the piston 3 can also be fixed to the rod 2 only by the piston nut 15 without providing a thread groove on the inner circumference of the second piston segment 32. The first piston segment 31 and the second piston segment 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 cooperate with each other to function as the piston 3.

[0025] In addition, when the first piston segment 31 and the second piston segment 32 overlap, the first port 31d faces the opening groove 32b, the first port 31d and the second port 32c communicate with each other, and a passage 3a for communicating the extension-side chamber R1 and the compression-side chamber R2 is formed. Additionally, the number of the first port 31d and the second port 32c can be set arbitrarily.

[0026] Further, when the first piston segment 31 and the second piston segment 32 overlap, the annular recess 31a provided on the outer circumference of the first piston segment 31 faces the dividing surface A2 of the second piston segment 32, and an annular groove for surrounding the outer circumference of the piston 3 is formed.

[0027] In the annular groove formed by the annular recess 31a, a sealing member 4 in the shape of a ring for sealing between the cylinder 1 and the piston 3 is accommodated. The sealing member 4 is configured to include a sealing ring 4a that slidably contacts the inner circumferential surface of the cylinder 1 and an O-ring 4b disposed on the inner circumferential side of the sealing ring 4a.

[0028] The sealing ring 4a is made of synthetic resin and slidably contacts the inner circumferential surface of the cylinder 1, having self-lubricity to prevent hydraulic oil from flowing between it and the cylinder 1 while not hindering the smooth movement of the piston 3. In addition, the O-ring 4b is in close contact with the inner circumferential surface of the sealing ring 4a and the bottom surface of the annular recess 31a of the piston 3 and seals between the sealing ring 4a and the piston 3 to prevent hydraulic oil from flowing through the annular recess 31a. In this way, in the buffer D of the present embodiment, the sealing member 4 is composed of the sealing ring 4a and the O-ring 4b, but it can also be composed of a single member.

[0029] In order to install the sealing member 4 on the outer periphery of the piston 3, before overlapping and integrating the first piston segment 31 and the second piston segment 32, the sealing member 4 can be accommodated in the annular recess 31a from the side of the dividing surface A1 of the first piston segment 31. Since the side of the dividing surface A1 of the first piston segment 31 of the annular recess 31a is open, when installing the sealing member 4 on the annular recess 31a, without expanding the diameter of the sealing member 4, the sealing member 4 can be installed in the annular recess 31a without applying any load to the sealing member 4.

[0030] In this way, after assembling the sealing member 4 on the first piston segment 31, if the first piston segment 31 and the second piston segment 32 are overlapped, the piston 3 can be formed.

[0031] In addition, an annular piston ring 5 for slidingly contacting the inner periphery of the cylinder 1 and guiding the axial movement of the piston 3 is installed in the annular groove 32a provided on the outer periphery of the second piston segment 32.

[0032] As described above, the piston 3 configured in this way is installed on the outer periphery of the small-diameter portion 2a of the rod 2. Specifically, a spiral spring 16, an annular valve body 17 formed of an annular plate and serving as a valve body, and the piston 3 are sequentially assembled at the front end of the rod 2. As described above, in a state where the dividing surfaces A1 and A2 between the first piston segment 31 and the second piston segment 32 are in close contact with each other, the piston 3 is fixed on the outer periphery of the small-diameter portion 2a of the rod 2.

[0033] In addition, the annular valve body 17 is formed of spring steel such as high-carbon steel, alloy steel, and stainless steel. The spring steel has excellent characteristics of elastic limit and fatigue limit. The annular valve body 17 is annular, has an outer diameter larger than the annular valve seat 31c of the first piston segment 31, and is slidably fitted between the first step portion 2c and the second step portion 2d of the rod 2 along the axial direction. Moreover, the annular valve body 17 can move away from or close to the piston 3 in the axial direction, closes the passage 3a in a state of abutting against the piston 3 and seating on the annular valve seat 31c, and opens the passage 3a when moving away from the piston 3. When the annular valve body 17 abuts against the second step portion 2d, its further movement to the Figure 1 left is restricted, and the maximum lift amount when moving away from the piston 3 is set according to the setting position of the second step portion 2d. The spiral spring 16 is installed between the third step portion 2e and the annular valve body 17, and applies a force to the annular valve body 17 to make it abut against the piston 3.

[0034] Therefore, in the buffer D of the present embodiment, the annular valve body 17 and the helical spring 16, which are the valve bodies that leave or seat on the annular valve seat 31c of the first piston segment 31, constitute a valve V for opening and closing the passage 3a. In the buffer D of the present embodiment, the valve V opens the passage 3a by moving the annular valve body 17 away from the annular valve seat 31c, thereby only allowing the hydraulic oil to flow from the compression side chamber R2 to the extension side chamber R1. When the hydraulic oil flows from the extension side chamber R1 to the compression side chamber R2, the annular valve body 17 seats on the annular valve seat 31c to form a check valve for closing the passage 3a.

[0035] Next, a discharge passage 10a for communicating the extension side chamber R1 and the reservoir R is provided on the rod guide 10. A damping valve 10b is provided on the discharge passage 10a. The damping valve only allows the hydraulic oil to flow from the extension side chamber R1 to the reservoir R, applies resistance to the flow of the hydraulic oil passing through, and prevents its reverse flow; the discharge passage 10a is set as a one-way passage that only allows the hydraulic oil to flow from the extension side chamber R1 to the reservoir R.

[0036] In addition, a suction passage 11a for communicating the reservoir R and the compression side chamber R2 is provided on the valve housing 11. A suction check valve 11b is provided on the suction passage 11a. The suction check valve only allows the hydraulic oil to flow from the reservoir R to the compression side chamber R2 and prevents its reverse flow; the suction passage 11a is set as a one-way passage that only allows the hydraulic oil to flow from the reservoir R to the compression side chamber R2.

[0037] The buffer D is configured in the above manner, and the operation of the buffer D will be described below. First, the operation when the rod 2 moves leftward relative to the cylinder 1 and the buffer D performs an extension operation will be described. When the buffer D performs an extension operation, the piston 3 moves leftward relative to the cylinder 1. Figure 1 As a result, the extension side chamber R1 is compressed, and the compression side chamber R2 is enlarged. Figure 1 In this case, since the passage 3a provided in the piston 3 is closed by the annular valve body 17 seating on the annular valve seat 31c, the hydraulic oil in the extension side chamber R1 flows through the damping valve 10b of the discharge passage 10a and is discharged to the reservoir R. Since resistance is applied to the movement of such hydraulic oil by the damping valve 10b, the pressure in the extension side chamber R1 rises and becomes higher than the pressure in the reservoir R. In addition, although the volume of the compression side chamber R2 expands due to the movement of the piston 3 and the hydraulic oil is insufficient, the insufficient part of the hydraulic oil is supplied from the reservoir R to the compression side chamber R2 through the suction check valve 11b being opened and via the suction passage 11a. Therefore, the pressure in the compression side chamber R2 is approximately equal to the pressure in the reservoir R.

[0038] ​

[0039] When the buffer D extends in this manner, the pressure in the extension-side chamber R1 acting on the side surface of the extension-side chamber R1 of the piston 3 is higher than the pressure in the compression-side chamber R2 acting on the side surface of the compression-side chamber R2 of the piston 3, and the buffer D generates an extension-side damping force that hinders the extension action. In addition, the hydraulic oil in the volume portion where the rod 2 withdraws from the cylinder 1 is supplied from the reservoir R to the compression-side chamber R2 to compensate for the volume where the rod 2 withdraws from the cylinder 1.

[0040] Next, the operation when the rod 2 moves to the Figure 1 right middle with respect to the cylinder 1 and the buffer D contracts will be described. When the buffer D contracts, the piston 3 moves to the Figure 1 right middle with respect to the cylinder 1. Therefore, while the compression-side chamber R2 is compressed, the extension-side chamber R1 is expanded.

[0041] In this case, while opening the passage 3a provided in the piston 3 by separating the annular valve body 17 from the annular valve seat 31c, the suction check valve 11b is closed and the suction passage 11a is cut off. Therefore, the hydraulic oil in the compression-side chamber R2 flows through the passage 3a and moves to the extension-side chamber R1. In addition, when the buffer D contracts, since the rod 2 intrudes into the cylinder 1, there is an excess of hydraulic oil in the volume portion where the rod 2 intrudes into the cylinder 1 in the cylinder 1. The excess hydraulic oil in the cylinder 1 is discharged to the reservoir R through the damping valve 10b of the discharge passage 10a. Since resistance is applied to the movement of such hydraulic oil by the damping valve 10b, the pressure in the extension-side chamber R1 rises and becomes higher than the pressure in the reservoir R. In addition, since the compression-side chamber R2 is in a state of being connected to the extension-side chamber R1 through the passage 3a, the pressure in the compression-side chamber R2 is approximately equal to the pressure in the extension-side chamber R1.

[0042] When the buffer D contracts in this manner, the pressure in the extension-side chamber R1 acting on the side surface of the extension-side chamber R1 of the piston 3 is approximately equal to the pressure in the compression-side chamber R2 acting on the side surface of the compression-side chamber R2 of the piston 3. However, since the pressure-receiving area that bears the pressure in the compression-side chamber R2 is larger than the pressure-receiving area that bears the pressure in the extension-side chamber R1 of the piston 3, the buffer D generates a compression-side damping force that hinders the contraction action. In addition, the hydraulic oil in the volume portion where the rod 2 intrudes into the cylinder 1 is discharged from the cylinder 1 to the reservoir R to compensate for the volume where the rod 2 intrudes into the cylinder 1. In this way, the buffer D generates a damping force when performing the telescopic action and attenuates the vibration of the object to be vibration-damped.

[0043] In addition, when the buffer D extends, the annular valve body 17 in the valve V abuts against the annular valve seat 31c on the first piston dividing body 31 provided in the piston 3 and cuts off the passage 3a. When the buffer D contracts, the annular valve body 17 in the valve V moves away from the piston 3 and opens the passage 3a. Thus, when the buffer D repeatedly expands and contracts, the annular valve body 17 repeatedly collides with the first piston dividing body 31. What is required of the first piston dividing body 31 that abuts against the annular valve body 17 is wear resistance, and a material with excellent wear resistance sometimes has poor strength. As in conventional buffers, when the entire piston is formed of a material with excellent wear resistance and is used after increasing the pressure in the cylinder 1 when the buffer expands and contracts in order to generate a high damping force, the strength of the piston may be insufficient.

[0044] However, in the buffer D of the present embodiment, the piston 3 includes a first piston dividing body 31 and a second piston dividing body 32 that are axially divided. The first piston dividing body 31 and the second piston dividing body 32 that collide with the annular valve body 17 are formed of different materials, and the strength of the second piston dividing body 32 is higher than that of the first piston dividing body 31. Therefore, when the buffer D expands and contracts, even if the pressure in the cylinder 1 is higher than before and a large axial force acts on the piston 3, since the second piston dividing body 32 with high strength supports the first piston dividing body 31 with poor strength in the axial direction, deformation of the first piston dividing body 31 can be prevented. In addition, since the deformation of the first piston dividing body 31 with poor strength can be supported by the second piston dividing body 32 with better strength, even if the flow path area of the passage 3a is increased for use in the high-speed expansion and contraction of the buffer D, deformation of the first piston dividing body 31 can be prevented.

[0045] Thus, the buffer D of the present embodiment includes: a cylinder 1; a rod 2 that is movably inserted into the cylinder 1; a piston 3 that is inserted into the cylinder 1 and divides the inside of the cylinder 1 into an extension side chamber R1 and a compression side chamber R2, and has a passage 3a for communicating the extension side chamber R1 and the compression side chamber R2; and a valve V for opening and closing the passage 3a. The piston 3 has a first piston dividing body 31 that is axially divided and causes the annular valve body (valve body) 17 of the valve V to leave or seat, and a second piston dividing body 32 that is axially opposed to the first piston dividing body 31. The second piston dividing body 32 is formed of a material with higher strength than the first piston dividing body 31.

[0046] As described above, in the buffer D configured in this way, even if the pressure in the cylinder 1 is increased, the deformation of the first piston dividing body 31 with poor strength can be supported by the second piston dividing body 32 with better strength, and the flow path area of the passage 3a can be increased. Therefore, according to the buffer D of the present embodiment, it can withstand the high pressure in the cylinder 1 and generate a high damping force.

[0047] In addition, in the buffer D of the present embodiment, the second piston segment 32 is screwed onto the threaded portion 2b of the rod 2, and the first piston segment 31 is clamped by the second piston segment 32 and the first step portion 2c of the rod 2. Therefore, the force acting on the piston 3 due to the pressure in the cylinder 1 is transmitted through the second piston segment 32 with high strength, and thus it is possible to prevent an excessive shearing force from acting on the inner peripheral portion of the first piston segment 31. Therefore, according to the buffer D configured in this way, it is possible to further protect the first piston segment 31 with relatively poor strength.

[0048] In addition, the structure of the valve V is not limited to the foregoing structure, and it may also be a flap valve or a lift valve. In addition, the piston 3 only needs to include a first piston segment 31 that is axially divided and causes the valve V to leave or seat, and a second piston segment 32 that is axially opposed to the first piston segment 31. Therefore, it may also be composed of three or more piston segments including the first piston segment 31 and the second piston segment 32.

[0049] In addition, in the buffer D of the present embodiment, since the annular valve body (valve body) 17 in the valve V is formed of a material having a higher strength than that of the first piston segment 31, it is also possible to prevent the annular valve body (valve body) 17 from deforming under the high pressure in the cylinder 1.

[0050] Alternatively, the first piston segment 31 may be formed of cast iron, and the annular valve body (valve body) 17 in the valve V may be formed of spring steel. Since cast iron has excellent wear resistance, it can also withstand the wear caused by the repeated collisions of the annular valve body (valve body) 17. Therefore, it is the best material for the first piston segment 31. Since spring steel has excellent elastic limit and fatigue limit, it is the best material for the annular valve body (valve body) 17, which is used to withstand a relatively high pressure from the back side opposite to the piston as the piston's opposite side in the extension side chamber R1 and repeatedly collide with the piston 3. As described above, according to the buffer D in which the first piston segment 31 is formed of cast iron and the annular valve body (valve body) 17 of the valve V is formed of spring steel, it is possible to reduce the deterioration caused by the wear of the first piston segment 31, and it is possible to reduce the deterioration such as deformation and fatigue of the annular valve body (valve body) 17.

[0051] Further, in the buffer D of the present embodiment, the first piston segment 31 is provided with a first port 31d communicating from the reverse partition surface B1 side to the partition surface A1 side, and the second piston segment 32 is provided with a second port 32c communicating from the reverse partition surface B2 side to the partition surface A2 side. On the partition surface A2 side of the second piston segment 32, there is provided an annular opening groove 32b for communicating with both the first port 31d and the second port 32c formed along the circumferential direction. According to the buffer D configured in this way, when the first piston segment 31 and the second piston segment 32 are overlapped, even if they are not aligned in the circumferential direction, the first port 31d and the second port 32c can communicate through the opening groove 32b. Therefore, when the passage 3a is provided in the piston 3, the assembly of the buffer D becomes easy. The opening groove may be provided on the partition surface A1 of the first piston segment 31 instead of the second piston segment 32.

[0052] In addition, the buffer D of the present embodiment includes: a reservoir R for storing hydraulic oil (fluid); a discharge passage 10a communicating the extension side chamber R1 and the reservoir R; a damping valve 10b provided on the discharge passage 10a and applying resistance to the flow of the hydraulic oil (fluid) while only allowing the hydraulic oil (fluid) to flow from the extension side chamber R1 to the reservoir R; a suction passage 11a communicating the reservoir R and the compression side chamber R2; and a suction check valve 11b provided on the suction passage 11a and only allowing the hydraulic oil (fluid) to flow from the reservoir R to the compression side chamber R2; the valve V is a check valve that only allows the hydraulic oil (fluid) to flow from the compression side chamber R2 to the extension side chamber R1 in the passage 3a. The buffer D configured in this way is set as a single-phase buffer in which when a telescopic action is presented, the hydraulic oil (fluid) sequentially passes through the reservoir R, the compression side chamber R2, the extension side chamber R1, and then flows back unidirectionally to the reservoir R. In the single-phase buffer D set, all of the hydraulic oil (fluid) moving from the reduced compression side chamber R2 during contraction moves to the extension side chamber R1 via the passage 3a. Therefore, the amount of hydraulic oil (fluid amount) flowing through the passage 3a in the single-phase buffer D is larger than the amount of hydraulic oil (fluid amount) flowing through the passage provided on the piston of the buffer. This buffer is set as a two-way buffer in which the hydraulic oil (fluid) reciprocates between the extension side chamber and the compression side chamber without passing through the reservoir during telescoping. In this way, in the single-phase buffer D, there is a high requirement for enlarging the flow path area of the passage 3a provided in the piston 3.

[0053] Therefore, the structure including the first piston segment 31 that seats or unseats the valve V on the piston 3 and the second piston segment 32 with high strength is most suitable for the single-phase buffer D that has to allow more hydraulic oil (fluid) to flow due to the high pressure in the cylinder 1, thereby improving the practicality of the single-phase buffer D.

[0054] In addition, the piston 3 includes a first piston divided body 31 divided axially and a second piston divided body 32 axially opposite to the first piston divided body 31, and the sealing member 4 is accommodated in an annular recess 31a provided on the outer periphery of the first piston divided body 31 on the side of the dividing surface A1.

[0055] In the buffer D configured in this way, before the first piston divided body 31 and the second piston divided body 32 are overlapped, the sealing member 4 can be accommodated in the annular recess 31a without expanding its diameter. When the first piston divided body 31 and the second piston divided body 32 are overlapped, the dividing surface A2 of the second piston divided body 32 faces the annular recess 31a, and an annular groove is formed on the outer periphery of the piston 3. Thus, even if the sealing member 4 accommodated in the annular recess 31a moves axially relative to the piston 3, it is clamped axially by the first piston divided body 31 and the second piston divided body 32 so as not to move and does not come out of the annular recess 31a.

[0056] Moreover, in the buffer D of the present embodiment, when the sealing member 4 is installed on the piston 3, after the sealing member 4 is accommodated in the annular recess 31a of the first piston divided body 31 in advance without applying any load, the sealing member 4 can be installed on the piston 3 only by overlapping the first piston divided body 31 and the second piston divided body 32. In addition, in the buffer D of the present embodiment, when the sealing member 4 is removed from the piston 3, after the first piston divided body 31 and the second piston divided body 32 are separated, the sealing member 4 is simply removed from the annular recess 31a of the first piston divided body 31.

[0057] Therefore, according to the buffer D of the present embodiment, it is possible to easily install the sealing member 4 on the outer periphery of the piston 3 without applying an unreasonable acting force to expand the diameter of the sealing member 4. Therefore, as the pressure in the cylinder 1 for generating a large damping force in the buffer D increases, the strength of the sealing member 4 is improved. As a result, even if it is difficult to expand the diameter of the sealing member 4, it is not necessary to expand the diameter of the sealing member 4 when the sealing member 4 is installed on the piston 3. Therefore, the sealing member 4 can be easily installed or removed on the piston 3. Therefore, according to the buffer D of the present embodiment, even if the sealing member 4 is made highly strong, the sealing member 4 can be easily installed or removed on the piston 3.

[0058] In addition, in the buffer D of the present embodiment, a ring-shaped recess 31a for accommodating the sealing member 4 is provided on the outer periphery of the first piston segment 31 on the side of the dividing surface A1. However, the ring-shaped recess 31a of the first piston segment 31 may be omitted and a ring-shaped recess for accommodating the sealing member 4 may be provided on the outer periphery of the second piston segment 32 on the side of the dividing surface A2. In this way, even if the operation of enlarging the diameter of the sealing member 4 is not performed before overlapping the first piston segment 31 and the second piston segment 32, it can be assembled on the second piston segment 32. Therefore, even if the sealing member 4 is made stronger, the sealing member 4 can be easily attached to or detached from the piston 3.

[0059] Furthermore, ring-shaped recesses that are axially opposed to each other may be provided on both the outer periphery of the first piston segment 31 on the side of the dividing surface A1 and the outer periphery of the second piston segment 32 on the side of the dividing surface A2. When the first piston segment 31 and the second piston segment 32 are overlapped, a single ring-shaped groove for accommodating the sealing member 4 is formed on the outer periphery of the piston 3 through these ring-shaped recesses. In this way, even if the operation of enlarging the diameter of the sealing member 4 is not performed when overlapping the first piston segment 31 and the second piston segment 32, it can be assembled on the outer periphery of the piston 3. Therefore, even if the sealing member 4 is made stronger, the sealing member 4 can be easily attached to or detached from the piston 3.

[0060] In addition, when the first piston segment 31 and the second piston segment 32 are axially overlapped and combined, as long as they can function as the piston 3, their shapes can be arbitrarily changed, and they may have concavities and convexities on the dividing surfaces A1 and A2.

[0061] In addition, the buffer D is a single-phase buffer, but it may also be a two-way buffer in which hydraulic oil reciprocates between the extension side chamber R1 and the compression side chamber R2 during the telescopic movement. When it is a two-way buffer, since the valve V is arranged on both sides of the first piston segment, a structure in which both axial sides of the first piston segment are clamped by the second piston segment formed of a material having a higher strength than the first piston segment is sufficient. In addition, for the discharge passage 10a, the damping valve 10b, and the suction passage 11a, the installation positions may also be set at positions other than the illustrated positions. In addition, the vibration damping objects of the buffer D are not limited to railway vehicles and structures, and may also be straddle-type vehicles, automobiles, other machines, etc.

[0062] The preferred embodiments of the present invention have been described in detail above, but modifications, deformations, and changes can be made as long as they do not depart from the scope of the claims.

[0063] This application claims priority based on Japanese Patent Application No. 2020-115277, filed with the Japan Patent Office on July 3, 2020, the entire content of which is incorporated herein by reference.

Claims

1. A buffer, which comprises: a cylinder; a rod that is movably inserted into the cylinder; a piston that is inserted into the cylinder and divides the interior of the cylinder into an extension-side chamber and a compression-side chamber, and has a passage for communicating the extension-side chamber and the compression-side chamber; and a valve for opening and closing the passage; the piston has a first piston segment that is axially divided and causes the valve body of the valve to be seated or unseated, and a second piston segment that is axially divided and axially opposed to the first piston segment; the second piston segment is formed of a material having a higher strength than that of the first piston segment.

2. The buffer according to claim 1, wherein the valve body is formed of a material having a higher strength than that of the first piston segment.

3. The buffer according to claim 2, wherein the first piston segment is formed of cast iron, and the valve body is formed of spring steel.

4. The buffer according to claim 1, wherein the first piston segment has a first port that communicates from the reverse division surface side to the division surface side, the second piston segment has a second port that communicates from the reverse division surface side to the division surface side, and has an annular opening groove that communicates with both the first port and the second port formed on the division surface side of one of the first piston segment and the second piston segment in the circumferential direction.

5. The buffer according to any one of claims 1 to 4, characterized in that it comprises: a reservoir for storing a fluid; a discharge passage for communicating the extension-side chamber and the reservoir; a damping valve provided on the discharge passage that allows only the fluid to flow from the extension-side chamber to the reservoir while applying resistance to the flow of the fluid; a suction passage for communicating the reservoir and the compression-side chamber; and a suction check valve provided on the suction passage that allows only the fluid to flow from the reservoir to the compression-side chamber; the valve is a check valve that allows only the fluid to flow from the compression-side chamber to the extension-side chamber in the passage.

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