JP2008267449A - Backup ring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backup ring capable of increasing the amount of radial extension so as to cope with a case where a gap between two members is large. <P>SOLUTION: An inner peripheral surface 111 and an outer peripheral surface 121 of the backup ring 100 are arranged parallel to and concentrically with the axis. Both faces of either of an inner diameter side end portion 110 and an outer diameter side end portion 120 are arranged perpendicularly to the axis. A projecting portion 130 is provided between the inner diameter side end portion 110 and the outer diameter side end portion 120. The projecting portion 130 elastically deforms when it receives pressure, and applies stress directed toward the inner diameter side to the inner diameter side end portion 110 and also applies stress directed toward the outer diameter side to the outer diameter side end portion 120. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a backup ring that prevents a part of a sealing device from protruding into a gap between two members.

  In a hydraulic cylinder used in various apparatuses such as a construction machine cylinder, a general machine cylinder, and a shock absorber, a sealing device is provided to seal an annular gap between the piston and the cylinder. As this sealing device, various packings made of a rubber-like elastic body such as a U-shaped packing having a U-shaped cross section are applied. In particular, when used in an environment where the pressure of the sealing fluid (generally, hydraulic pressure) is high, a part of the sealing device is prevented from protruding into the protruding gap between the piston and the cylinder. For this purpose, a backup ring is used.

  A conventional general backup ring will be described with reference to FIGS. 8 to 10 are schematic cross-sectional views of a sealing structure portion to which a backup ring according to a conventional example is applied. 8 shows a state in which no hydraulic pressure is applied, FIG. 9 shows a state in which the hydraulic pressure is applied, and FIG. 10 shows a state in which the hydraulic pressure is applied and the protruding gap is large.

  As shown in each figure, in order to seal the annular gap between the piston 600 and the cylinder 700, a packing 300 as a sealing device is provided. In this conventional example, an annular groove 610 is provided on the piston 600 side, and the packing 300 is disposed in the annular groove 610. Further, the packing 300 according to this conventional example is a U-shaped packing made of a rubber-like elastic body, having lips 310 and 320 on the inner peripheral side and the outer peripheral side, respectively, and having a substantially U-shaped cross section. The inner peripheral lip 310 is in close contact with the groove bottom surface 611 of the annular groove 610, and the outer peripheral lip 320 is in close contact with the inner peripheral surface 710 of the shaft hole provided in the cylinder 700. The annular gap between them is sealed.

  When receiving the hydraulic pressure, the packing 300 is pushed from the high pressure side (H) to the low pressure side (L). Therefore, a part of the packing 300 may protrude into the protruding gap S0 between the piston 600 and the cylinder 700 and may be damaged, for example, partly torn. Therefore, in order to prevent this, a resin-made backup ring 810 is disposed in the annular groove 610 on the lower pressure side (L) than the packing 300.

  FIG. 8 shows a state where the packing 300 is not subjected to hydraulic pressure. At this time, there is a gap between the outer peripheral surface 811 of the backup ring 810 and the inner peripheral surface 710 of the shaft hole of the cylinder 700. When receiving the hydraulic pressure P, the packing 300 is pushed from the high pressure side (H) to the low pressure side (L). Therefore, the backup ring 810 is sandwiched between the low pressure side (L) end surface 330 of the packing 300 and the low pressure side surface 612 of the annular groove 610. As a result, the backup ring 810 is compressed and deformed in the axial direction, and thus is expanded and deformed in the radial direction. By the expansion and deformation of the backup ring 810 in the radial direction, the outer peripheral surface 811 of the backup ring 810 closely contacts the inner peripheral surface 710 of the shaft hole of the cylinder 700, and a part of the packing 300 (in this case, the end on the outer peripheral side) Protruding into the protruding gap S0 can be prevented (see FIG. 9).

Here, the gap between the outer peripheral surface 811 of the backup ring 810 and the inner peripheral surface 710 of the shaft hole of the cylinder 700 is the initial state (the state in which no hydraulic pressure is applied) from the viewpoint of enhancing the function of preventing the packing 300 from protruding. ) Is as small as possible. However, there are limits to reducing this gap in consideration of the mountability and the dimensional tolerance of each part.

  Further, when a soft material is applied as the material of the backup ring 810 in order to increase the amount of expansion deformation in the radial direction of the backup ring 810, the pressure resistance of the backup ring 810 is inferior. Therefore, it is desirable to use a hard material as a material for the backup ring 810. However, when a hard material is used as the material of the backup ring 810, the amount of expansion and deformation becomes small. Therefore, when the protruding gap S1 (> S0) is large, the outer peripheral surface 811 of the backup ring 810 and the axis of the cylinder 700 A gap may be formed between the inner peripheral surface 710 of the hole and a part of the packing 300 may protrude into the gap (see the portion indicated by arrow X in FIG. 10).

  In particular, in recent years, a reduction in the thickness of the cylinder tube has been studied in order to reduce the weight of the cylinder. When the cylinder tube is thinned, the expansion of the cylinder tube due to the internal pressure in the cylinder increases, and the amount of change in the gap between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder increases. Therefore, in the case of a packing made of a rubber-like elastic body, even if the change in the gap can be followed, there is a possibility that the change in the gap cannot be handled in the case of a hard resin backup ring.

  Here, as a countermeasure when the gap between the cylinder and the piston becomes large, a technique is known in which the cross-sectional shape of the backup ring is a parallelogram (see Patent Document 1).

  In the case of this technique, only one of the end part on the inner diameter side and the end part on the outer diameter side of the backup ring (only the end part on the inner diameter side disclosed in Patent Document 1) is on the side surface of the annular groove. The other portion is in contact with the side surface of the annular groove. For this reason, the backup ring is deformed so as to be directed in the radial direction by elastic deformation due to a gap between the annular groove and the side surface of the annular groove, rather than the expansion and contraction in the radial direction accompanying the compressive deformation in the axial direction. Therefore, it can be applied to the case where the gap between the cylinder and the piston is large as compared with the case of the extensional deformation in the radial direction accompanying the compression deformation.

  However, in this technique, when the backup ring is pushed into the packing, the backup ring is in contact with the side surface of the annular groove when viewed in a cross section of the backup ring (cross section passing through the axis). Deforms to rotate around the part. Therefore, in the process of deforming the backup ring, both the outer peripheral surface and the inner peripheral surface of the backup ring change in inclination with respect to the mating member surface. Therefore, it is difficult to completely eliminate the gap between the outer peripheral surface of the backup ring and the inner peripheral surface of the shaft hole of the cylinder and between the inner peripheral surface of the backup ring and the outer peripheral surface of the piston. Further, when the cross-sectional shape of the backup ring is a parallelogram, there is not much stability at the time of mounting, and as a result, the assemblability is not good.

  In addition, as a countermeasure when the gap between the cylinder and the piston becomes large, a technique is also known in which the groove bottom of the annular groove in which the backup ring is attached has a tapered surface (patent) References 2 and 3).

In the case of this technique, when the gap between the cylinder and the piston is large, the backup ring slides in the axial direction and the gap becomes smaller as the gap between the cylinder and the piston becomes larger. Can also be adapted. However, in the case of this technique, since at least a part of the groove bottom of the annular groove has to be a tapered surface, it takes time and cost for the groove processing compared to the case where the tapered surface is not formed. .
Japanese Patent Application Laid-Open No. 8-135595 Japanese Patent Laid-Open No. 11-72162 JP 11-315925 A

  An object of the present invention is to provide a backup ring that can increase the amount of expansion and deformation in the radial direction so that it can be applied even when the gap between two members becomes large.

  The present invention employs the following means in order to solve the above problems.

That is, the backup ring of the present invention is
A backup ring provided adjacent to a sealing device for sealing an annular gap between two members,
When the sealing device disposed in the annular groove provided in one of the two members receives the pressure of the sealing fluid, a part of the sealing device becomes an end of the low-pressure side surface of the annular groove. In order to prevent the edge portion from protruding into the gap between the two members, in the backup ring disposed in the annular groove and on the lower pressure side than the sealing device,
The end on the inner diameter side and the end on the outer diameter side are both a surface facing the opposite member of the two members and a surface facing the low-pressure side surface of the annular groove. It is configured to be parallel to the surface of the opposing part,
Between the end portion on the inner diameter side and the end portion on the outer diameter side, it is elastically deformed by receiving pressure, and stress in the direction toward the inner diameter side is applied to the end portion on the inner diameter side. And the protrusion part which gives the stress to the direction which goes to an outer diameter side with respect to the edge part on the said outer diameter side is provided.

  In the backup ring of the present invention, the inner diameter side end and the outer diameter side end are either a surface facing the opposite member of the two members or a surface facing the low-pressure side surface of the annular groove. Is also configured to be parallel to the surface of the opposing portion on the opposing counterpart side. Therefore, when the backup ring is pushed into the sealing device and is sandwiched between the sealing device and the low-pressure side surface of the annular groove, both the inner diameter side end portion and the outer diameter side end portion move in the axial direction. Compressive deformation in the axial direction.

  Further, since the backup ring of the present invention is provided with a protruding portion, when the protruding portion receives pressure, a stress in a direction toward the inner diameter side is applied to the end portion on the inner diameter side, and A stress in a direction toward the outer diameter side is applied to the end portion on the outer diameter side. Therefore, the backup ring is deformed so as to expand in the radial direction not only by the radial deformation due to the compressive deformation in the axial direction but also by the elastic deformation of the protruding portion.

  Here, the backup ring is preferably composed of a single member made of resin.

The backup ring is composed of two members, a resin-made first ring and a rubber-like elastic second ring,
It is also preferable that the second ring is disposed on the groove bottom side of the annular groove and the protruding portion is provided on the second ring.

In this way, by providing the second ring made of a rubber-like elastic body and providing the second ring with a protruding portion, the backup ring can be further expanded and deformed in the radial direction.

  In addition, said each structure can be employ | adopted combining as much as possible.

  As described above, according to the present invention, the amount of expansion and deformation in the radial direction can be increased so that it can be applied even when the gap between the two members is increased.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. .

Example 1
With reference to FIGS. 1-3, the backup ring which concerns on Example 1 of this invention is demonstrated. FIG. 1 is a part of a schematic cross-sectional view of a backup ring according to Embodiment 1 of the present invention. 2 and 3 are schematic sectional views showing a state in which the backup ring according to the first embodiment of the present invention is mounted. 2 shows a state where no hydraulic pressure is applied, and FIG. 3 shows a state where the hydraulic pressure is applied.

<Backup ring>
With reference to FIG. 1 in particular, the configuration of the backup ring according to the first embodiment of the present invention will be described. The backup ring 100 according to the present embodiment is composed of a single member made of resin. The backup ring 100 according to the present embodiment is configured by a plate-like member, and is a member having a circular planar shape and a concentric circular hole at the center of the circle.

  An end portion on the inner diameter side (hereinafter referred to as an inner diameter side end portion 110) and an outer diameter side end portion (hereinafter referred to as an outer diameter side end portion 120) in the backup ring 100 are configured to be on the same flat plate. ing. Therefore, both surfaces (both surfaces in the axial direction) of the inner diameter side end portion 110 and the outer diameter side end portion 120 are configured to be in the same plane. Further, the inner peripheral surface 111 and the outer peripheral surface 121 of the backup ring 100 are configured to be parallel and concentric with the axis. Both surfaces of the inner diameter side end portion 110 and the outer diameter side end portion 120 are configured to be perpendicular to the axis.

  Further, the backup ring 100 is provided with a protruding portion 130 between the inner diameter side end portion 110 and the outer diameter side end portion 120. The protruding portion 130 is configured by a portion protruding in a curved shape in the axial direction from the flat plate portions of the inner diameter side end portion 110 and the outer diameter side end portion 120. Further, the protruding portion 130 is continuously provided over the entire circumference.

<Function of backup ring>
In particular, the function of the backup ring according to the first embodiment of the present invention will be described with reference to FIGS.

  Generally, an annular sealing device is used to seal an annular gap between two members. In the present embodiment, the case where the annular gap between the piston 400 and the cylinder 500 constituting the hydraulic cylinder is sealed by the packing 300 as a sealing device will be described as an example.

In the present embodiment, an annular groove 510 is provided on the inner peripheral side of the shaft hole of the cylinder 500, and the packing 300 is disposed in the annular groove 510. The packing 300 according to this embodiment is a U-shaped packing made of a rubber-like elastic body, having lips 310 and 320 on the inner peripheral side and the outer peripheral side, respectively, and having a substantially U-shaped cross section. The inner peripheral lip 310 is in close contact with the outer peripheral surface 410 of the piston 400, and the outer peripheral lip 320 is in close contact with the groove bottom surface 511 of the annular groove 510 provided on the inner peripheral side of the shaft hole of the cylinder 500. The annular gap between 400 and cylinder 500 is sealed.

  When receiving the hydraulic pressure, the packing 300 is pushed from the high pressure side (H) to the low pressure side (L). For this reason, a part of the packing 300 may protrude into the protruding gap S between the piston 400 and the cylinder 500 and may be damaged, for example, partly torn. More specifically, the end portion on the inner peripheral side of the packing 300 on the low pressure side (L) may protrude from the end edge portion of the low pressure side surface 512 of the annular groove 510 into the clearance S.

  Therefore, in order to prevent this, the backup ring 100 according to the present embodiment is disposed in the annular groove 510 on the lower pressure side (L) than the packing 300.

  FIG. 2 shows a state where the packing 300 is not subjected to hydraulic pressure. At this time, the outer peripheral surface 121 of the backup ring 100 and the groove bottom surface 511 of the annular groove 510 provided on the inner peripheral side of the shaft hole of the cylinder 500 are shown. There is a gap between the inner peripheral surface 111 of the backup ring 100 and the outer peripheral surface 410 of the piston 400.

  When receiving the hydraulic pressure P, the packing 300 is pushed from the high pressure side (H) to the low pressure side (L). Therefore, the backup ring 100 is sandwiched between the low pressure side (L) end surface 330 of the packing 300 and the low pressure side surface 512 of the annular groove 510.

  Then, in the case of the backup ring 100 according to the present embodiment, first, the protruding portion 130 is pushed in by the low pressure side (L) end surface 330 of the packing 300. Thereby, the curved protruding portion 130 is elastically deformed so that the radius of curvature gradually increases and finally becomes a flat plate shape (the radius of curvature is infinite). In the process of this deformation, a stress in the direction toward the inner diameter side is applied to the inner diameter side end portion 110, and a stress in the direction toward the outer diameter side is applied to the outer diameter side end portion 120. . Therefore, when the backup ring 100 is viewed as a whole, the backup ring 100 is deformed so as to expand and deform in the radial direction.

  And after the protrusion part 130 becomes flat plate shape and the shape of the backup ring 100 whole becomes flat plate shape, like the case of a general backup ring, the backup ring 100 is compressed and deformed in the axial direction, and in the radial direction. Deforms and stretches.

  As described above, due to the expansion and deformation of the backup ring 100 in the radial direction, the inner peripheral surface 111 of the backup ring 100 comes into close contact with the outer peripheral surface 410 of the piston 400, and a part of the packing 300 (in this case, the end on the inner peripheral side) ) Can be prevented from protruding into the protruding gap S (see FIG. 3).

<Excellent points of this embodiment>
The backup ring 100 according to the present embodiment is configured such that an inner peripheral surface 111 thereof (corresponding to the front end surface of the inner diameter side end portion 110) and an outer peripheral surface of the piston 400 facing this are parallel (and concentric). Has been. Further, the outer peripheral surface 121 (corresponding to the front end surface of the outer diameter side end portion 120) and the groove bottom surface 511 of the annular groove 510 provided on the inner peripheral side of the shaft hole of the cylinder 500 facing this are parallel (and concentric). It is configured to become.

Furthermore, the low pressure side (L) surface of the inner diameter side end portion 110 and the low pressure side (L) surface of the outer diameter side end portion 120 are both parallel to the low pressure side surface 512 of the annular groove 510 facing them. It is comprised so that. That is, all of these surfaces are configured as surfaces perpendicular to the axis.

  From the above, when the backup ring 100 is pushed into the packing 300 and sandwiched between the packing 300 and the low pressure side surface 512 of the annular groove 510, the inner diameter side end 110 and the outer diameter side end 120 are Also moves in the axial direction or compressively deforms in the axial direction. For this reason, when the cross-sectional shape is a parallelogram (see Patent Document 1 described above), when viewed in the cross-section of the backup ring (cross-section passing through the axis), the backup ring is Therefore, it does not deform so as to rotate with the contacted part as the base point. Therefore, the backup ring 100 according to the present embodiment has good stability at the time of mounting and good assemblability.

  Further, since the backup ring 100 according to the present embodiment is provided with the protruding portion 130, when the protruding portion 130 receives pressure, the inner diameter side end portion 110 is stressed in the direction toward the inner diameter side. The outer end 120 is given a stress in the direction toward the outer diameter.

  Therefore, the backup ring 100 is deformed so as to extend in the radial direction not only by the radial deformation due to the compressive deformation in the axial direction but also by the elastic deformation of the protruding portion 130.

  Thereby, the amount of expansion deformation in the radial direction can be further increased as compared with the case of only the expansion deformation in the radial direction accompanying the compression deformation in the axial direction as in a general backup ring. Accordingly, the present invention can be applied to a case where the amount of change in the gap between the two members is large.

(Example 2)
4 to 7 show a second embodiment of the present invention. In the first embodiment, the case where the backup ring is composed of a single resin member has been described. However, in this embodiment, the backup ring includes a resin-made first ring and a rubber-like elastic second ring. The case where it consists of these two members is demonstrated. In the first embodiment, the case where the annular groove is provided on the cylinder side has been described as an example. However, in this embodiment, the case where the annular groove is provided on the piston side will be described as an example. In addition, the same code | symbol is attached | subjected about the component same as the case of the said Example 1, and the description is abbreviate | omitted suitably.

  FIG. 4 is a part of a schematic cross-sectional view of a backup ring and a sealing device (packing) according to Embodiment 2 of the present invention. 5-7 is typical sectional drawing of the sealing structure part to which the backup ring based on Example 2 of this invention was applied. Here, FIG. 5 shows a state in which no hydraulic pressure is applied, FIG. 6 shows a state in which the hydraulic pressure is applied, and FIG. 7 shows a state in which the hydraulic pressure is applied and a protruding gap is large.

  The backup ring 200 according to the present embodiment includes a first ring 210 made of resin and a second ring 220 made of a rubber-like elastic body, and the first ring 210 and the second ring 220 are arranged concentrically. . In the present embodiment, the first ring 210 is disposed on the outer diameter side, and the second ring 220 is disposed on the inner diameter side.

  The first resin ring 210 has a configuration similar to that of a general resin backup ring, and is a ring-shaped member having a rectangular cross-sectional shape (cross-sectional shape passing through the axis). The outer peripheral surface 211 and the inner peripheral surface 212 are configured to be parallel and concentric with the axis. Also, both axial surfaces are configured to be perpendicular to the axial center. That is, the first ring 210 is a simple cylindrical member.

  The second ring 220 made of a rubber-like elastic body has the same configuration as the backup ring in the first embodiment except that the material is made of a rubber-like elastic body. That is, the inner diameter side end portion (hereinafter referred to as the inner diameter side end portion 221) and the outer diameter side end portion (hereinafter referred to as the outer diameter side end portion 222) of the second ring 220 are on the same flat plate. It is configured. Therefore, both surfaces (both surfaces in the axial direction) of the inner diameter side end portion 221 and the outer diameter side end portion 222 are configured to be on the same plane. Further, the inner peripheral surface 221a and the outer peripheral surface 222a of the second ring 220 are configured to be parallel to and concentric with the axial center. Both surfaces of the inner diameter side end portion 221 and the outer diameter side end portion 222 are configured to be perpendicular to the axis.

  Further, the second ring 220 is provided with a protruding portion 223 between the inner diameter side end 221 and the outer diameter side end 222. The protruding portion 223 is configured by a portion protruding in a curved shape in the axial direction from the flat plate portions of the inner diameter side end 221 and the outer diameter side end 222. The protruding portion 223 is continuously provided over the entire circumference.

  Further, the width (axial distance) of the first ring 210 and the width (axial distance) of the second ring 220 are set to be the same. Therefore, in a state in which these rings are combined (a state in which the second ring 220 is fitted on the inner diameter side of the first ring 210) and no external force is applied, these two axial surfaces are the same surface. It becomes.

  Here, also in the present embodiment, the case where the annular gap between the piston 600 and the cylinder 700 constituting the hydraulic cylinder is sealed by the packing 300 as a sealing device will be described as an example. The packing 300 has the same configuration as that described in the first embodiment.

  However, in the present embodiment, the case where the annular groove 610 is provided on the piston 600 side and the packing 300 is disposed in the annular groove 610 will be described as an example.

  Also in the case of the present embodiment, as in the case of the first embodiment, the backup ring 200 according to the present embodiment is disposed in the annular groove 610 and on the lower pressure side (L) than the packing 300.

  FIG. 5 shows a state where the packing 300 is not subjected to hydraulic pressure. At this time, the gap between the outer peripheral surface of the backup ring 200 (the outer peripheral surface 211 of the first ring 210) and the inner peripheral surface 710 of the shaft hole of the cylinder 700 is shown. There is a gap. In this embodiment, there is no gap between the inner peripheral surface of the backup ring 200 (the inner peripheral surface 221a of the second ring 220) and the groove bottom surface 611 of the annular groove 610 provided on the outer peripheral side of the piston 600. It is configured as follows.

  When receiving the hydraulic pressure P, the packing 300 is pushed from the high pressure side (H) to the low pressure side (L). Therefore, the backup ring 200 is sandwiched between the low pressure side (L) end surface 330 of the packing 300 and the low pressure side surface 612 of the annular groove 610.

  Then, in the case of the backup ring 200 according to the present embodiment, first, the protruding portion 223 of the second ring 220 is pushed in by the low pressure side (L) end surface 330 of the packing 300. Thereby, the curved protruding portion 223 is elastically deformed so that the radius of curvature gradually increases and finally becomes a flat plate shape (the radius of curvature is infinite). In the process of this deformation, a stress in the direction toward the inner diameter side is applied to the inner diameter side end portion 221, and a stress in the direction toward the outer diameter side is applied to the outer diameter side end portion 222. . Therefore, when the second ring 220 is viewed as a whole, the second ring 220 is deformed so as to expand and deform in the radial direction.

  Then, the second ring 220 is extended and deformed in the radial direction, whereby the inner peripheral surface 212 of the first ring 210 is pushed in the outer radial direction. Thereby, the first ring 210 is deformed so as to expand its diameter. Accordingly, the backup ring 200 as a whole is deformed so as to expand and deform in the radial direction.

  And after the protrusion part 223 becomes flat plate shape and the shape of the backup ring 200 whole becomes flat plate shape, the backup ring 200 (the 1st ring 210 and the 2nd ring 220) is the same as the case of a general backup ring. Is compressed and deformed in the axial direction and stretched and deformed in the radial direction. Needless to say, the elastic deformation amount of the second ring 220 made of rubber-like elastic material is larger than that of the first ring 210 made of resin.

  Thus, also in the present embodiment, the outer peripheral surface of the backup ring 200 (the outer peripheral surface 211 of the first ring 210) is in close contact with the inner peripheral surface 710 of the shaft hole of the cylinder 700 due to the radial deformation of the backup ring 200. In addition, it is possible to prevent a part of the packing 300 (in this case, the end on the outer peripheral side) from protruding into the protruding gap S. In addition, since it is the resin-made first ring 210 that prevents a part of the packing 300 from protruding into the protruding gap S, the backup ring itself (the first ring 210 itself) protrudes into the protruding gap S. There is no such thing.

  Needless to say, by configuring the backup ring 200 as described above, the present embodiment can achieve the same effects as those of the first embodiment. In this embodiment, the backup ring 200 is configured to include the second ring 220 made of a rubber-like elastic body, and the protruding portion 223 is provided to the second ring 220. Therefore, it is easy to make the deformation amount that deforms so that the protruding portion 223 expands in the radial direction when receiving pressure is larger than that in the first embodiment.

  In this embodiment, when the protrusion gap is small (in the case of the protrusion gap S0), the outer peripheral surface 211 of the first ring 210 is the inner periphery of the shaft hole of the cylinder 700 before the projecting portion 223 becomes flat. It is set so as to be in close contact with the surface 710 (see FIG. 6).

  Even when the protrusion gap is large (in the case of the protrusion gap S1 (> S0)), the protruding portion 223 is deformed until it has a flat plate shape, and further, due to the radial extension deformation accompanying the axial compression deformation. Since the backup ring 200 is further extended and deformed, the outer peripheral surface 211 of the first ring 210 is in close contact with the inner peripheral surface 710 of the shaft hole of the cylinder 700 (see FIG. 7).

  In addition, as a factor which becomes large, the case where a cylinder expand | swells as an internal pressure becomes large, or the case where eccentricity becomes large as a cylinder becomes thin.

(Other)
As described above, in the backup ring of the present invention, the annular groove is provided in the member on the shaft side (piston in the first and second embodiments) and the member having the shaft hole (cylinder in the first and second embodiments). It can be applied to any of the cases.

  In the case where the backup ring is composed of the first ring and the second ring as in the second embodiment, when the annular groove is provided in the member (cylinder) having the shaft hole, the resin-made first ring has the inner diameter It is necessary to employ | adopt the structure which arrange | positions to the side and arrange | positions the 2nd ring made from a rubber-like elastic body to the outer diameter side. This is because it is necessary to arrange the resin-made first ring on the side of the sealing device (packing) that prevents protrusion.

  In the first and second embodiments, the backup ring is arranged so that the protruding portion faces the packing side. However, the protruding portion faces the low-pressure side surface of the annular groove. A backup ring may be placed. However, as shown in Examples 1 and 2, the projecting portion is directed toward the packing side, and in the process until the projecting portion becomes flat, there is a gap between the portion excluding the projecting portion and the packing. Therefore, it is possible to more reliably prevent a part of the packing from being caught between the backup rings.

  As specific materials for the sealing device (packing) and the second ring, nitrile rubber, fluorine rubber, hydrogenated nitrile rubber, urethane rubber, and the like can be cited as preferred examples. In Example 2, it is desirable that the packing and the second ring be made of the same material as much as possible. These materials may be appropriately selected according to usage conditions and the like. Moreover, as a specific material of the backup ring in Example 1 and the 1st ring in Example 2, hard materials, such as a tetrafluoroethylene resin and a polyamide resin, can be mentioned as a suitable example. These materials may be appropriately selected according to the use conditions.

FIG. 1 is a part of a schematic cross-sectional view of a backup ring according to Embodiment 1 of the present invention. FIG. 2 is a schematic cross-sectional view showing a state where the backup ring according to the first embodiment of the present invention is mounted (a state where no hydraulic pressure is applied). FIG. 3 is a schematic cross-sectional view illustrating a state in which the backup ring according to the first embodiment of the present invention is mounted (a state in which hydraulic pressure is applied). FIG. 4 is a part of a schematic cross-sectional view of a backup ring and a sealing device (packing) according to Embodiment 2 of the present invention. FIG. 5 is a schematic cross-sectional view (showing a state where no hydraulic pressure is applied) of the sealing structure portion to which the backup ring according to the second embodiment of the present invention is applied. FIG. 6 is a schematic cross-sectional view (showing a state where hydraulic pressure is applied) of the sealing structure portion to which the backup ring according to the second embodiment of the present invention is applied. FIG. 7 is a schematic cross-sectional view (showing a state where hydraulic pressure is applied and a protruding gap is large) of the sealing structure portion to which the backup ring according to the second embodiment of the present invention is applied. FIG. 8 is a schematic cross-sectional view (showing a state where no hydraulic pressure is applied) of a sealing structure portion to which a backup ring according to a conventional example is applied. FIG. 9 is a schematic cross-sectional view (showing a state where hydraulic pressure is applied) of a sealing structure portion to which a backup ring according to a conventional example is applied. FIG. 10 is a schematic cross-sectional view of a sealing structure portion to which a backup ring according to a conventional example is applied (showing a state where hydraulic pressure is applied and a protruding gap is large).

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Backup ring 110 Inner diameter side edge 111 Inner peripheral surface 120 Outer diameter side end 121 Outer peripheral surface 130 Protruding part 200 Backup ring 210 First ring 211 Outer surface 212 Inner peripheral surface 220 Second ring 221 Inner diameter side end 221a Inner circumference Surface 222 Outer diameter side end 222a Outer peripheral surface 223 Protruding portion 300 Packing 310, 320 Lip 330 End face 400 Piston 410 Outer surface 500 Cylinder 510 Annular groove 511 Groove bottom surface 512 Low pressure side surface 600 Piston 610 Annular groove 611 Groove bottom surface 612 Low pressure side surface 700 Cylinder 710 Inner peripheral surface

Claims (3)

A backup ring provided adjacent to a sealing device for sealing an annular gap between two members,
When the sealing device disposed in the annular groove provided in one of the two members receives the pressure of the sealing fluid, a part of the sealing device becomes an end of the low-pressure side surface of the annular groove. In order to prevent the edge portion from protruding into the gap between the two members, in the backup ring disposed in the annular groove and on the lower pressure side than the sealing device,
The end on the inner diameter side and the end on the outer diameter side are both a surface facing the opposite member of the two members and a surface facing the low-pressure side surface of the annular groove. It is configured to be parallel to the surface of the opposing part,
Between the end portion on the inner diameter side and the end portion on the outer diameter side, it is elastically deformed by receiving pressure, and stress in the direction toward the inner diameter side is applied to the end portion on the inner diameter side. And the protrusion part which gives the stress to the direction which goes to an outer diameter side with respect to the edge part on the outer diameter side is provided.   The backup ring according to claim 1, wherein the backup ring is made of a single member made of resin. It is composed of two members, a first ring made of resin and a second ring made of rubber-like elastic body,
The backup ring according to claim 1, wherein the second ring is disposed on a groove bottom side of the annular groove, and the protruding portion is provided on the second ring.

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