JP2017166597A - Sealing structure and sealing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure sealing performance between a cylinder part and a piston part even if eccentricity exceeding assumption is generated.SOLUTION: A sealing structure 1 comprises: a piston part 20 having an accurately recess 23 at an end face of a piston 21 in an axial line x direction; a cylinder part 10 in which an annular step part 12 is arranged having a flat face 12b parallel with the end face 21b of the piston 21 which reciprocates along the axial line x direction; and a sealing device 30 attached to the recess 23. The sealing device 30 has: a seal ring 31 which can reciprocate along the axial line x direction while being inserted into the recess 23, and has a cross-section recessed accommodation space; an annular elastic body seal 32 attached to an internal peripheral face of the seal ring; and an elastic member 33 which elongates and contracts in a state of straddling both an inside space of the recess 23 and the accommodation space of the seal ring 31. Even if eccentricity is generated between the piston part 20 and the cylinder part 10 in the radial direction, a state that a bottom is pressed against the flat face 12b of the step part 12 by an energization force of the elastic member 33 is maintained.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sealing structure and a sealing device, and more particularly to a sealing structure and a sealing device for sealing a portion where a piston reciprocates with respect to a cylinder.

  Conventionally, in a hydraulic cylinder for a construction machine, a piston seal is attached to an annular groove between the piston and the center of the piston, and a wear ring as a bearing is attached to the outer peripheral surface of the piston. ing. The wear ring is used to prevent galling between the piston and the cylinder, to reduce the eccentricity between the piston and the cylinder, and to improve the durability and sealing performance of the packing.

  A piston sealing system to which such a wear ring is attached has been proposed (for example, see Patent Document 1). As shown in FIG. 6, the piston sealing system 100 includes a piston seal (packing) 530 (first ring 510 and second ring 520), a wear ring 540, and a wear ring 550. The piston sealing system 100 is disposed in an annular gap between an inner peripheral surface 601a of a shaft hole provided in the cylinder 600 and an outer peripheral surface 500a of a piston 500 inserted through the shaft hole.

  The outer circumferential surface 500a of the piston 500 has a first annular groove 501, a second annular groove 502 and a third annular groove formed on both sides in the direction along the axis x with the first annular groove 501 interposed therebetween. 503 is provided. The first annular groove 501 includes a first ring 510 made of a hard material such as nylon, and a second elastic rubber body that presses the first ring 510 toward the inner peripheral surface 601 a of the cylinder 600. A piston seal (packing) 530 comprising a ring 520 is attached.

  A wear ring 540 and a wear ring 550 made of a hard material such as nylon are attached to the second annular groove 502 and the third annular groove 503. Wear ring 540 and wear ring 550 are provided as bearings for piston 500, prevent galling between piston 500 and cylinder 600, reduce eccentricity between piston 500 and cylinder 600, and provide piston seals. It is used to improve the durability of 530.

  As described above, when the piston sealing system 100 including the piston seal 530 and the pair of wear rings 540 and wear rings 550 provided on both sides of the piston seal 530 is used, the sealing function and the bearing can be maintained for a long time even under high pressure. It is possible to exhibit the function stably.

  Moreover, as shown in FIG. 7 in which the same reference numerals are assigned to the parts corresponding to those in FIG. 6, the piston sealing system 200 includes a piston seal (packing) 530 (first ring 510 and second ring 520). At the same time, the fitting dimension is set such that the gap between the inner peripheral surface 611a of the shaft hole of the cylinder 610 and the outer peripheral surface 551a of the piston 550 is as narrow as possible. By using the piston sealing system 200 having such a configuration, the eccentricity between the piston 550 and the cylinder 610 can be reduced in advance.

JP 2010-14173 A

  By the way, the piston 560 on both sides of the piston seal 530 (the first ring 510 and the second ring 520) is similar to the piston sealing system 300 shown in FIG. The gaps 561 and 562 with the cylinder 600 may be too narrow to attach the wear ring.

  In such a case, since the eccentricity between the piston 560 and the cylinder 600 cannot be reduced, the second ring 520 made of a rubber-like elastic body is set to an outer diameter tightening allowance that can follow the eccentricity, or the second The ring 520 must be set to have a cross-sectional crushing allowance that can follow the eccentricity. However, when the eccentric deflection width is larger than expected, a region that cannot be followed by the second ring 520 occurs, and the eccentricity may not be reduced.

  Also, like the piston sealing system 400 shown in FIG. 9, although the common piston seal 530 (the first ring 510 and the second ring 520) is mounted, the pistons 560 having different structures and sizes from each other. , And the piston 570 may be connected in the axial direction.

  In such a case, since the eccentricity of the two pistons 560 and 570 is stacked, the second ring 520 cannot follow the clearance between the cylinder 620 and the piston 560 or the clearance between the cylinder 630 and the piston 570. There was a case where the eccentricity could not be reduced.

  The present invention has been made in view of the above problems, and its purpose is to seal between the cylinder portion and the piston portion even when eccentricity more than expected occurs between the cylinder portion and the piston portion. It is an object of the present invention to provide a sealing structure and a sealing device that can ensure the performance.

  In order to achieve the above object, in the present invention, the piston rod (22) and the piston (21) are provided on the end surface (21b) along the radial direction perpendicular to the axis (x) direction of the piston (21). The piston part (20) having an annular recess (23) formed at a predetermined depth along the axis (x) direction and the piston (21) reciprocating along the axis (x) direction. A cylinder part (10) provided with an annular step part (12) having a flat surface (12b) parallel to the end face (21b), and a sealing device attached to the concave part (23) of the piston (21) ( 30), wherein the sealing device (30) reciprocates along the axis (x) while being inserted into the recess (23) of the piston (21). It is possible to have a concave cross section. A ring-shaped member (31) having a space, an annular seal member (32) mounted on the inner peripheral surface (31ci) of the ring-shaped member (31), and the recess (23) of the piston (21). The inner space and the recess (23) and the elastic member (33) disposed in the housing space so as to expand and contract in a state of straddling both the housing space of the ring-shaped member (31). Even when eccentricity occurs in the radial direction between the piston part (20) and the cylinder part (10), the bottom part (31) of the ring-shaped member (31) is applied by the urging force of the elastic member (33). The state where 31a) is pressed against the flat surface (12b) of the stepped portion (12) of the cylinder portion (10) is maintained.

  In the sealing device according to an aspect of the present invention, even if the piston portion (20) is moved relative to the cylinder portion (10) in the axis (x) direction, the ring-shaped member (31). The bottom part (31a) of the cylinder part (10) is pressed against the flat surface (12b) of the step part (12) of the cylinder part (10).

  In the sealing device according to one aspect of the present invention, the elastic member (33) is a wave coil spring.

  In the sealing device according to one aspect of the present invention, the ring-shaped member includes an annular seal member attached to an inner peripheral surface thereof.

  The sealing device which concerns on 1 aspect of this invention WHEREIN: The said sealing member (32) is mounted | worn with the cyclic | annular groove part (31 cm) formed in the internal peripheral surface (31ci) of the said ring-shaped member (31). Features.

  Moreover, in this invention, it consists of a piston rod (22) and a piston (21), and it is an annular recessed part (23) in the end surface (21b) along the radial direction orthogonal to the axis line (x) direction of the said piston (21). And a step portion (12) having a flat surface (12b) parallel to the end surface (21b) of the piston (21) slidably moved relative to the axis (x). A sealing device (30) attached to the recess (23) of the piston (21) of a sealing structure (1) including a provided cylinder portion (10), wherein the recess ( 23) can be reciprocated along the direction of the axis (x) while being inserted into the ring-shaped member (31) having an accommodation space having a concave cross section, and the inner peripheral surface of the ring-shaped member (31). Attached to (31ci) It extends and contracts in a state straddling both the annular seal member (32), the inner space of the recess (23) of the piston (21), and the accommodation space of the ring-shaped member (31). Even when the radial direction eccentricity occurs between the piston part (20) and the cylinder part (10), the concave part (23) and the elastic member (33) arranged in the accommodation space are included. The state in which the bottom portion (31a) of the ring-shaped member (31) is pressed against the flat surface (12b) of the stepped portion (12) of the cylinder portion (10) is maintained by the urging force of the elastic member (33). It is characterized by being.

  According to the sealing device according to the present invention, even when the eccentricity more than expected occurs between the cylinder part and the piston part, the sealing structure and the sealing that can ensure the sealing performance between the cylinder part and the piston part. An apparatus can be realized.

It is an expanded sectional view showing a schematic structure of a sealing structure and a sealing device concerning an embodiment of the invention. It is a partial expanded sectional view which shows the structure of the recessed part of the piston part compared with embodiment of this invention. It is an expanded sectional view which shows the structure of the piston part of the sealing structure which concerns on embodiment of this invention. It is a fragmentary sectional enlarged view which shows the mounting state of the spring in embodiment of this invention. It is a side view which shows the whole structure of the spring in embodiment of this invention. It is an approximate line sectional view showing the composition of the piston sealing system at the time of using the conventional wear ring. It is a rough sectional drawing which shows the structure of the piston sealing system at the time of narrowing the clearance gap between the conventional cylinder and piston as much as possible. It is an approximate line sectional view showing composition of a piston sealing system when there is no conventional wear ring installation space. It is an approximate line sectional view showing composition of a piston sealing system in case a conventional piston with a different outside diameter is connected.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an enlarged cross-sectional view showing a schematic configuration of a sealing structure and a sealing device according to an embodiment of the present invention. FIG. 2 is a partially enlarged cross-sectional view showing the configuration of the recess of the piston portion compared with the embodiment of the present invention. FIG. 3 is an enlarged cross-sectional view showing the configuration of the piston portion of the sealing structure according to the embodiment of the present invention. FIG. 4 is an enlarged partial cross-sectional view showing a mounting state of the spring in the embodiment of the present invention. FIG. 5 is a side view showing the overall configuration of the spring according to the embodiment of the present invention.

  Hereinafter, for convenience of explanation, in FIGS. 1 to 5, in the arrow ab direction along the axis x (hereinafter, also referred to as “stroke direction”), the sealing target side is the arrow a along the axis x direction. The direction. The atmosphere side is the direction of arrow b along the axis x direction. That is, the sealing target side is the direction inside the cylinder 10 and facing the hydraulic oil, and the atmosphere side is the direction outside the cylinder 10 and facing the atmosphere. In the direction of arrow cd orthogonal to the axis x (hereinafter also referred to as “radial direction”), the direction away from the axis x (arrow c direction) is the outer peripheral side, and the direction approaches the axis x (arrow d direction). Is the inner circumference side.

<Configuration of sealing structure>
As shown in FIGS. 1 to 5, a sealing structure 1 according to an embodiment of the present invention seals between a cylinder portion 10 and a piston portion 20 in a hydraulic cylinder for construction machinery by a sealing device 30. .

  The cylinder portion 10 includes a cylindrical cylindrical portion 11 having an inner peripheral surface 11a in the stroke direction (arrow ab direction) along the axis x, and a radial direction perpendicular to the axis x from the inner peripheral surface 11a of the cylindrical portion 11. And an annular step 12 that further protrudes toward the inner peripheral side (in the direction of arrow cd) (in the direction of arrow d).

  The step portion 12 is orthogonal to the axis line x connecting the inner peripheral surface 12a in the stroke direction (arrow ab direction) along the axis line x, the inner peripheral surface 11a of the cylindrical portion 11 and the inner peripheral surface 12a of the step portion 12. And an end face 12b along the radial direction (arrow cd direction). The end surface 12b is a flat surface along a radial direction (arrow cd direction) perpendicular to the axis x and parallel to an end surface 21b of the piston 21 described later. Henceforth, the end surface 12b of the step part 12 is called the flat surface 12b.

  The piston portion 20 includes a piston 21 having a predetermined outer diameter and a piston rod 22 having a smaller diameter than the piston 21. The piston rod 22 has an outer peripheral surface 22 a that is parallel to the inner peripheral surface 12 a of the step portion 12 of the cylinder portion 10 and that extends along the axis x.

  The piston 21 is radially parallel to the inner peripheral surface 11a of the cylindrical portion 11 and along the axis x, and the radial direction orthogonal to the axis x connecting the outer peripheral surface 22a of the piston rod 11 and the outer peripheral surface 21a of the piston 21. And an end face 21b along the arrow cd direction. The end surface 21 b of the piston 21 is a flat surface that is parallel to the flat surface 12 b of the stepped portion 12 of the cylinder 10.

  On the end surface 21 b of the piston 21, an annular recess 23 is formed having a predetermined depth in the stroke direction (arrow ab direction) along the axis x. In the recess 23, the annular inner space is a mounting space for mounting a sealing device 30 described later. The recess 23 has a predetermined width L1 in the radial direction (arrow cd direction).

  In the present embodiment, as shown in FIG. 2, the concave portion 29 is formed from the outer peripheral surface 21a of the piston 21 toward the inner peripheral side (arrow d direction) in the radial direction (arrow cd direction) perpendicular to the axis x. It is not assumed that it will be formed. As shown in FIG. 3, the recess 23 needs to be formed in the stroke direction (arrow ab direction) along the axis x with respect to the end surface 21 b of the piston 21.

<Configuration of sealing device>
As shown in FIG. 1, the sealing device 30 includes a space between the cylinder portion 10 and the piston portion 20 on the sealing target side (in the direction of arrow a) (hereinafter referred to as “sealed space”) Oi, It is separated from the atmosphere side (arrow b direction) space (hereinafter referred to as “atmosphere space”) Ai and prevents the hydraulic fluid in the sealed space Oi from leaking to the atmosphere side (arrow b direction). In addition, foreign matter such as dust is prevented from entering from the atmospheric space Ai to the sealing target side (in the direction of arrow a).

  As shown in FIG. 4, the sealing device 30 includes a seal ring 31 as a ring-shaped member, an elastic body seal 32 as a seal member, and a spring 33 as an elastic member.

  The seal ring 31 is made of a resin material, and in addition to a polytetrafluoroethylene (PTFE) soft resin, a curable resin such as polyether ether ketone (PEEK), poniphenylene sulfide resin (PPS), and nylon 6,6. Is also applicable.

  The seal ring 31 has a length in the stroke direction (arrow ab direction) along the axis x, that is, the height of the seal ring 31 is in the stroke direction (arrow ab direction) along the axis x of the recess 23 of the piston portion 21. It is formed shorter than the depth.

  However, the height of the seal ring 31 in the stroke direction (arrow ab direction) is such that the piston portion 20 moves relative to the cylinder portion 10, and the end surface 21 b of the piston 21 and the flat surface 12 b of the step portion 12 of the cylinder 10. It is set longer than the gap C1 when the distance between the two is farthest. Therefore, when the piston 21 moves relative to the cylinder portion 10, the seal ring 31 is formed so as not to fall out of the concave portion 23 of the piston 21.

  The seal ring 31 is a ring having an accommodation space having a concave shape in a cross section along the axis x. The seal ring 31 has an annular portion 31a as a bottom portion that extends in a direction orthogonal to the axis x, and a cylindrical shape that extends from the outer peripheral side (arrow c direction) end of the annular portion 31a to the sealing target side (arrow a direction). The outer peripheral side cylindrical portion 31b, a cylindrical inner peripheral side cylindrical portion 31c extending from the end on the inner peripheral side (arrow d direction) of the outer peripheral side annular portion 31a to the sealing target side (arrow a direction), It is formed in a concave annular shape.

  Further, the width L2 from the outer peripheral surface 31bg on the outer peripheral side (arrow c direction) of the outer peripheral side cylindrical portion 31b of the seal ring 31 to the inner peripheral surface 31ci on the inner peripheral side (arrow d direction) of the inner peripheral side cylindrical portion 31c is: It is formed to be slightly smaller than the width L1 of the recess 23 of the piston 21. Therefore, the seal 31 is slid in the stroke direction (arrow ab direction) in the recess 23 in a state where the outer peripheral side cylindrical portion 31b and the inner peripheral side cylindrical portion 31c of the seal ring 31 face each other with respect to the recess 23 of the piston 21. It can be inserted freely.

  An end surface (hereinafter also referred to as “outer bottom surface”) 31am on the atmosphere side (arrow b direction) of the annular portion 31a is a flat surface parallel to the radial direction (arrow cd direction) perpendicular to the axis x. Is formed. That is, the outer bottom surface 31 am of the annular portion 31 a is parallel to the flat surface 12 b of the step portion 12 of the cylinder 11. Note that the end surface (hereinafter also referred to as “inner bottom surface”) 31ai on the sealing target side (arrow a direction) of the annular portion 31a is also parallel to the radial direction (arrow cd direction) orthogonal to the axis x. It is formed as a flat surface.

  In the seal ring 31 having such a configuration, the inner annular housing space surrounded by the annular portion 31a, the outer peripheral side cylindrical portion 31b, and the inner peripheral side cylindrical portion 31c is used for arranging the spring 33. .

  On the inner peripheral surface 31ci on the inner peripheral side (in the direction of arrow d) of the inner peripheral side cylindrical portion 31c, a groove portion 31cm having an annular cross section is formed at a predetermined position in the stroke direction (in the direction of arrow ab) along the axis x. Yes. The width of the groove 31 cm in the stroke direction (arrow ab direction) is formed larger than the outer diameter of the elastic seal 32, and the depth in the radial direction (arrow cd direction) is smaller than the outer diameter of the elastic seal 32. Has been.

  The elastic body seal 32 is an O-ring made of an elastic body, for example. Examples of the elastic body of the elastic body seal 32 include various rubber materials. The rubber material may be an elastic body of rubber, for example, nitrile rubber (NBR), fluorine rubber (FKM), ethylene propylene rubber (EPDM), or the like. Further, the shape of the elastic seal 32 is not limited to the O-ring, and may be various other shapes such as a twister ring (X ring) and a USH type ring.

  As shown in FIGS. 4 and 5, the spring 33 is, for example, a series multi-winding wave coil spring in which a metal (for example, stainless steel) flat wire is deformed into a continuous wave shape and coiled. The spring 33 is disposed so as to extend and contract in a state of straddling both the inner space of the recess 23 of the piston 21 and the housing space having a concave cross section of the seal ring 31.

  Specifically, one end 33a on the sealing target side (arrow a direction) of the spring 33 is fixed to the inner bottom surface 23ai of the recess 23 of the piston 21, and the other end 33b on the atmosphere side (arrow b direction) of the spring 33 is a seal ring. 31 is fixed to the inner bottom surface 31ai of the annular portion 31a.

  The spring 33 constantly applies a biasing force toward the atmosphere side (arrow b direction) in the direction of the seal ring 31 toward the stepped portion 12 of the cylinder 11, that is, the stroke direction (arrow ab direction) along the axis x. .

  In this case, it is necessary to set within a range in which the spring 33 is bent by at least 1 mm with respect to the maximum stroke amount Stmax of the piston 21. That is, the spring set length of the spring 33 is set so as to satisfy the relationship of the stroke amount St of the piston 21 relative to the cylinder 11 <the spring deflection amount Ad of the spring 33 and to follow the stroke amount St of the piston 21.

  Here, the advantage of using a wave coil spring as the spring 33 is to obtain a stable bending characteristic while keeping the free length shorter than the coil spring. However, the spring 33 is not limited to this, and may be a wave coil spring of a parallel double winding type, a single winding type, or the like, and instead of using the wave coil spring, the seal ring 31 is accommodated. A plurality of coil springs may be arranged in the space in the circumferential direction at equal intervals.

<Operation by sealing device>
In the sealing structure 1 having such a configuration, as shown in FIG. 1, the elastic body mounted in the groove 31 cm on the inner peripheral surface of the seal ring 31 in a state where the sealing device 30 is mounted in the recess 23 of the piston 21. The seal 32 is brought into contact with the inner peripheral surface of the recess 23 of the piston 21 with a predetermined crushing margin.

  Therefore, even when the piston part 20 moves relative to the cylinder part 10 in the stroke direction (arrow ab direction) along the axis x, the elastic seal 32 attached to the inner peripheral surface of the seal ring 31 is provided. Closely slidable. Thereby, the sealing state between the said seal ring 31 and the piston part 21 is maintainable.

  Even when the piston portion 20 moves relative to the cylinder portion 10 in the stroke direction (arrow ab direction) along the axis x, the spring 33 moves the seal ring 31 toward the step portion 12 of the cylinder portion 10. The urging power is always given. Therefore, the close contact state in which the outer bottom surface 31am of the annular portion 31a of the seal ring 31 is pressed against the flat surface 12b of the step portion 12 is maintained.

  For this reason, even when a larger eccentricity than expected occurs between the cylinder portion 10 and the piston portion 20 during the operation of the hydraulic cylinder, the outer bottom surface 31am and the step portion 12 of the annular portion 31a of the seal ring 31 are formed. A sliding resistance is generated between the flat surface 12b and the flat surface 12b. As a result, the sealed state between the sealing 31 and the stepped portion 12 can be maintained while suppressing eccentricity between the cylinder portion 10 and the piston portion 20.

  Thus, the sealing device 30 prevents the hydraulic oil in the sealed space Oi closer to the sealing target side (arrow a direction) than the sealing device 30 from leaking to the atmosphere side (arrow b direction), and the sealing device 30. It is possible to prevent foreign matters such as dust from entering the sealing target side (arrow a direction) from the atmospheric space Ai on the atmosphere side (arrow b direction).

  As described above, in the sealing structure 1, even when the gap between the cylinder portion 10 and the piston portion 20 is narrow and the wear ring cannot be attached, it is easy to simply attach the sealing device 30 to the recess 23 of the piston 21. With the configuration, it is possible to maintain the sealed state between the sealing 31 and the stepped portion 12 while suppressing the eccentricity between the cylinder portion 10 and the piston portion 20.

  Thus, the sealing structure 1 and the sealing device 30 that can ensure the sealing performance between the cylinder part 10 and the piston part 20 even when eccentricity more than expected occurs between the cylinder part 10 and the piston part 20. Can be realized.

<Other embodiments>
In the above-described embodiment, the case where the piston portion 20 is reciprocated in the stroke direction with respect to the cylinder portion 10 has been described. However, the present invention is not limited thereto, and the cylinder portion 10 is not limited thereto. However, the present invention may be applied when the piston portion 20 only rotates without reciprocating.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the sealing structure 1 and the sealing device 30 according to the above-described embodiments, and is within the concept of the present invention and the scope of the claims. Includes all included aspects. In addition, the respective configurations may be selectively combined as appropriate so as to achieve at least part of the above-described problems and effects. For example, the shape, material, arrangement, size, and the like of each component in the above embodiment can be changed as appropriate according to the specific usage mode of the present invention.

  The case where the sealing structure and the sealing device of the present invention are applied to an application for sealing between the cylinder portion 10 and the piston portion 20 in a hydraulic cylinder for construction machinery has been described. However, what uses the sealing structure and the sealing device of the present invention can be applied to applications for sealing in applications such as rotation, swing, and reciprocation.

DESCRIPTION OF SYMBOLS 1 Sealing structure 10 Cylinder part 11 Cylindrical part 11a, 12a, 31ci Inner peripheral surface 12 Step part 12b Flat surface 20 Piston part 21 Piston 21a, 22a, 31bg Outer peripheral surface 21b End surface 22 Piston rod 23, 29 Recess 30 Sealing device 31 Seal ring (Ring-shaped member)
31a Annular part 31am Outer bottom 31ai Inner bottom 31b Outer cylindrical part 31c Inner cylindrical part 31cm Groove 32 Elastic seal (seal member)
33 Spring (elastic member)
33a One end 33b The other end Oi Sealed space Ai Atmospheric space x Axis

Claims (6)

A piston portion comprising a piston rod and a piston, and having an annular recess formed at a predetermined depth along the axial direction on an end surface along the radial direction orthogonal to the axial direction of the piston;
A cylinder portion provided with an annular step portion having a flat surface parallel to the end surface of the piston that reciprocates along the axial direction;
A sealing structure provided with a sealing device attached to the recess of the piston,
The sealing device includes:
A ring-shaped member that can reciprocate along the axial direction while being inserted into the concave portion of the piston, and has an accommodation space with a concave cross-section,
An elastic member disposed in the recess and the storage space so as to expand and contract in a state straddling both the inner space of the recess of the piston and the storage space of the ring-shaped member,
Even when eccentricity occurs in the radial direction between the piston part and the cylinder part, the bottom part of the ring-shaped member is pressed against the flat surface of the step part of the cylinder part by the urging force of the elastic member. Sealing structure characterized in that the state is maintained. Even when the piston part moves relative to the cylinder part in the axial direction, the state where the bottom part of the ring-shaped member is pressed against the flat surface of the step part of the cylinder part is maintained. The sealing structure according to claim 1, wherein: The sealing structure according to claim 1, wherein the elastic member is a wave coil spring. The sealing structure according to claim 1, wherein the ring-shaped member has an annular seal member mounted on an inner peripheral surface thereof. The sealing structure according to claim 4, wherein the seal member is mounted in an annular groove formed on an inner peripheral surface of the ring-shaped member. A piston portion comprising a piston rod and a piston and having an annular recess on an end surface along a direction orthogonal to the axial direction of the piston, and a flat surface parallel to the end surface of the piston that slidably moves in the axial direction A sealing device mounted on the concave portion of the piston having a sealing structure including a cylinder portion provided with a stepped portion having a surface;
A ring-shaped member that can reciprocate along the axial direction while being inserted into the concave portion of the piston, and has an accommodation space with a concave cross-section,
An elastic member disposed in the recess and the storage space so as to expand and contract in a state straddling both the inner space of the recess of the piston and the storage space of the ring-shaped member,
Even when eccentricity occurs in the radial direction between the piston part and the cylinder part, the bottom part of the ring-shaped member is pressed against the flat surface of the step part of the cylinder part by the urging force of the elastic member. A sealing device characterized in that the state is maintained.

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