Sealing device

A sealing device has a seal ring in a groove having a step, a first backup ring at the step in the groove, and a second backup ring, in the groove, between both rings offset from the step. The first backup ring includes a bottom-surface-side peripheral surface facing the step's bottom surface, an end surface facing the step's non-sealed-fluid-side side surface, a peripheral surface adjacent to the other member and facing the other member, and a slope facing the second backup ring. The length of the bottom-surface-side peripheral surface is equal to or smaller than the length of the bottom surface of the step. The second backup ring includes a peripheral surface facing the bottom surface of the groove, an end surface facing the non-sealed-fluid-side side surface of the groove, a slope facing the slope of the first backup ring, and a sealed-fluid-side end surface facing the seal ring.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase application of International Application No. PCT/JP2018/020134, filed on May 25, 2018 and published in Japanese as WO-2018/230306 on Dec. 20, 2018 and claims priority to Japanese Patent Application No. 2017-116202, filed on Jun. 13, 2017. The entire disclosures of the above applications are expressly incorporated by reference herein.

BACKGROUND

Technical Field

The disclosure relates to a sealing device associated with a sealing technology. The sealing device in accordance with the disclosure is suitably used especially as a high pressure seal for sealing a high-pressure sealed fluid.

Related Art

As a high pressure seal, a sealing device101illustrated inFIG. 3has conventionally been known. The sealing device101is disposed between two members,151and152, which face each other, to seal a sealed fluid on a high pressure side H, so that the sealed fluid does not leak to a low pressure side L. The sealing device101is composed of a seal ring111which is mounted in a circular mounting groove153provided in one member (e.g. a shaft)151of one of the two members151and152and which is brought in close contact with the other member (e.g. a housing)152, and a combination of a first backup ring121which is disposed on a non-sealed-fluid side (the low pressure side) L of the seal ring111and which is relatively hard, and a second backup ring131which is disposed between the seal ring111and the first backup ring121and which is relatively soft.

The mounting groove153is easily machined, so that the groove has a rectangular section. The first backup ring121is formed to have a triangular section and is provided with a perpendicular-to-axis planar end surface121afacing a non-sealed-fluid-side side surface153bof the mounting groove153, a cylindrically shaped peripheral surface121bfacing the other member152, and a slope121cwhich intersects with the end surface121aand the peripheral surface121b. The second backup ring131is provided with a perpendicular-to-axis planar end surface131afacing the seal ring111, a cylindrically shaped peripheral surface131bfacing a bottom surface153aof the mounting groove153, and a slope131cprovided, matching the slope121cof the first backup ring121. As with the first backup ring121, the second backup ring131is also formed to have a triangular section.

In the sealing device101having the foregoing configuration, the first backup ring121disposed on the non-sealed-fluid side (the low pressure side) L of the seal ring111makes it possible to prevent the seal ring111made of a rubber-like elastic material from protruding to a gap154between the two members151and152and consequently being damaged when the seal ring111is subjected to a high pressure P. Further, in the sealing device101, the second backup ring131disposed between the seal ring111and the first backup ring121makes it possible to prevent the seal ring111from protruding to a gap (not illustrated) between the first backup ring121and the other member152and consequently being damaged.

In the foregoing sealing device101, the following inconveniences are pointed out due to the simple triangular shapes of the sections of both the first backup ring121and the second backup ring131.

To install the sealing device101between the two members151and152, the sealing device101is first installed in the mounting groove153of the one member151and then the sealing device101is inserted together with the one member151into the inner periphery (a shaft hole152a) of the other member152(arrow x), as illustrated inFIG. 4A. At this time, the following event occurs, because an outer diameter dimension d1of the seal ring111before the insertion is larger than an inner diameter dimension d2of the shaft hole152a.

As illustrated inFIG. 4B, at the insertion, the outer periphery of the seal ring111interferes with an opening peripheral edge152bof the shaft hole152a. At this time, while the insertion of the seal ring111is temporarily stopped, the insertion of the one member151and the first backup ring121and the second backup ring131, which are pushed by the one member151, is continued (the arrow x), so that an interval t between the side surface153bof the mounting groove153and the seal ring111is gradually decreased.

In the second backup ring131, a corner131dbetween the peripheral surface131band the slope131chas an acute angle, and the corner131dhaving the acute angle tends to be compressed in an axial direction when pressed against the side surface153bof the mounting groove153. Hence, as the interval t between the side surface153bof the mounting groove153and the seal ring111is decreased, the second backup ring131is compressed and deformed, and the entire second backup ring131is moved toward the side surface153bof the mounting groove153, pressing the first backup ring121. The two backup rings121and131are in contact at the slopes121cand131c, so that, when the second backup ring131presses the first backup ring121, the first backup ring121is subjected to component forces in the directions of arrows y, and is deformed, increasing the outer diameter dimension thereof.

If the insertion of the first backup ring121is further continued in the deformed state with the increased diameter, then the outer periphery thereof interferes with the opening peripheral edge152bof the shaft hole152a, thus causing the first backup ring121to be damaged in some cases.

An object of the disclosure is to restrain damage to a first backup ring caused by an increase in the diameter of the first backup ring when inserting one member into the other member in a sealing device which is formed of a seal ring and the combination of a first backup ring and a second backup ring, the sealing device being attached to one of the two members.

SUMMARY

A sealing device includes: a seal ring which is installed in a mounting groove provided in one member of two members facing each other and which is brought in close contact with the other member; a first backup ring disposed at a step which is provided on a non-sealed-fluid side in the mounting groove and which decreases a groove depth; and a second backup ring which is disposed, in the mounting groove, between the seal ring and the first backup ring at a part other than the step and which is softer than the first backup ring, wherein the first backup ring has: a bottom-surface-side peripheral surface which faces a bottom surface of the step and an axial length of which is set to a length that is equal to or less than an axial length of the bottom surface of the step; an end surface facing a non-sealed-fluid-side side surface of the step; a peripheral surface which is adjacent to the other member and which faces the other member; and a slope which inclines such that the axial length of the bottom-surface-side peripheral surface is shorter than the axial length of the peripheral surface adjacent to the other member, and the second backup ring has: a peripheral surface facing a bottom surface of the mounting groove; a non-sealed-fluid-side end surface facing a non-sealed-fluid-side side surface of the mounting groove; a slope facing the slope of the first backup ring; and a sealed-fluid-side end surface facing a non-sealed-fluid-side side surface of the seal ring.

Effect

The sealing device can restrain damage to a first backup ring caused by an increase of the diameter of the first backup ring when inserting one member into the other member in a sealing device which is formed of a seal ring and the combination of a first backup ring and a second backup ring, the sealing device being attached to one of the two members.

DETAILED DESCRIPTION

FIG. 1illustrates the section of an essential part of a sealing device1according to an embodiment. The sealing device1according to the embodiment is used for a high pressure seal in hydraulic equipment, such as a direct injection injector.

The sealing device1is disposed in a circular gap between a shaft (one member)51and a housing (the other member)52, which are two members facing each other, to prevent a sealed fluid existing on a high pressure side (a sealed-fluid side) H on the right in the drawing from leaking to a low pressure side (a non-sealed-fluid side) L on the left in the drawing. The sealing device1has an O-ring11, which is a seal ring that is installed in a circular mounting groove53provided in the peripheral surface of the shaft51and is in close contact with the inner peripheral surface of the shaft hole of the housing52, a first backup ring21which is disposed on the non-sealed-fluid side L of the O-ring11and which is also installed in the mounting groove53, and a second backup ring31which is disposed between the O-ring11and the first backup ring21and which is also installed in the mounting groove53. The O-ring11may be replaced by a D-ring, an X-ring or other seal rings having different sectional shapes.

The O-ring11is formed of a rubber-like elastic material. The first backup ring21is formed of, for example, a nylon resin, which is harder than the second backup ring31. The second backup ring31is formed of, for example, a PTFE resin, which is softer than the first backup ring21.

The mounting groove53is easily machined, and is therefore formed into a rectangular groove having a rectangular section. The mounting groove53is provided with a step53dhaving a rectangular section that decreases the depth of the groove, the step53dbeing provided on a non-sealed-fluid-side side surface53c. The mounting groove53includes a cylindrically shaped bottom surface53a, a sealed-fluid-side side surface53bwhich is shaped like a plane perpendicular to axis, and a non-sealed-fluid-side side surface53cwhich is also shaped like a plane perpendicular to axis. The step53dhas a cylindrically shaped bottom surface53eand a non-sealed-fluid-side side surface53fwhich is shaped like a plane perpendicular to axis. The diameter dimension of the bottom surface53eof the step53dis set to be larger than that of the bottom surface53aof the mounting groove53. The non-sealed-fluid-side side surface53cof the mounting groove53may be inclined toward the sealed-fluid side H.

The first backup ring21is adapted to be installed at the step53din the mounting groove53, and includes a cylindrically shaped inner peripheral surface21a, which is the bottom-surface-side peripheral surface facing the bottom surface53eof the step53d, an end surface21bwhich faces a non-sealed-fluid-side side surface53fof the step53dand which is shaped like a plane perpendicular to axis, a cylindrically shaped outer peripheral surface21c, which is the peripheral surface adjacent to the other member and which faces the inner peripheral surface of the shaft hole of the housing52, and a slope21dhaving a tapered surface that inclines such that the axial length of the inner peripheral surface21ais shorter than the axial length of the outer peripheral surface21c. The sectional shape of the first backup ring21is basically trapezoidal or substantially trapezoidal. The tapering direction of the slope21dis such that the diameter dimension (the inner diameter dimension) thereof gradually decreases from the sealed-fluid side (the high pressure side) H toward the non-sealed-fluid side (the low pressure side) L.

The second backup ring31is installed to the main body of the mounting groove53rather than the step53d. The second backup ring31includes a cylindrically shaped inner peripheral surface31a, which is the peripheral surface facing the bottom surface53aof the mounting groove53, a non-sealed-fluid-side end surface31bwhich is shaped like a planar perpendicular to axis and which faces the non-sealed-fluid-side side surface53cof the mounting groove53, a slope31cfacing the slope21dof the first backup ring21, and a sealed-fluid-side end surface31dfacing a non-sealed-fluid-side side surface11aof the O-ring11. The sectional shape of the second backup ring31is basically trapezoidal or substantially trapezoidal. The slope31cis provided, matching the slope21dof the first backup ring21, and the tapering direction is such that the diameter dimension (the outer diameter dimension) thereof gradually decreases from the sealed-fluid side (the high pressure side) H toward the non-sealed-fluid side (the low pressure side) L. The slope31cis provided continuously along the outer periphery of the non-sealed-fluid-side end surface31b.

An outer diameter dimension d3of the first backup ring21is set to be smaller than an inner diameter dimension d2of the housing52, so that the first backup ring21does not interfere with the shaft hole opening peripheral edge (not illustrated) of the housing52when the sealing device1is inserted into a shaft hole52aof the housing52. An outer diameter dimension d4of the second backup ring31is also set to be smaller than the inner diameter dimension d2of the housing52, so that the second backup ring31does not interfere with the shaft hole opening peripheral edge (not illustrated) of the housing52when the sealing device1is inserted into the shaft hole52aof the housing52.

An axial length L1of the inner peripheral surface21a, which is the inner periphery of the first backup ring21, is set to be equal to an axial length L2of the bottom surface53eof the step53dor smaller than the axial length L2(L1≤L2).

The slope21dof the first backup ring21is formed to have a concave arc-shaped surface in a sectional view. The slope31cof the second backup ring31is formed to have a convex arc-shaped surface in a sectional view. The curvature radii of the two slopes21dand31care set to be the same. This enables the two slopes21dand31cto be in surface contact over the whole surfaces.

The sealed-fluid-side end surface31dof the second backup ring31is formed as a concave arc-shaped surface in a sectional view. The non-sealed-fluid-side side surface11aof the O-ring11is formed as a convex arc-shaped surface in a section view. The curvature radius of the sealed-fluid-side end surface31dof the second backup ring31is set to be larger than the curvature radius of the non-sealed-fluid-side side surface11aof the O-ring11. Therefore, in an initial state in which any pressure or external force has not yet been applied to the sealing device1, the O-ring11is in contact with only the radial central part of the second backup ring31and not in contact with the outer periphery and the inner periphery of the second backup ring31, thus forming an initial axial gap41.

In the sealing device1having the foregoing configuration, the first backup ring21is disposed on the non-sealed-fluid side L of the O-ring11, thus making it possible to prevent the O-ring11from protruding to a radial gap54between the shaft51and the housing52and being damaged when the O-ring11is subjected to a high pressure P. The sealing device1further has the second backup ring31disposed between the O-ring11and the first backup ring21, thus making it possible to prevent the O-ring11from protruding to a radial gap55between the first backup ring21and the housing52and being damaged. Hence, the deterioration of sealing performance caused by the O-ring11protruding to the gaps54or55and being damaged can be suppressed.

In the sealing device1, the non-sealed-fluid-side end surface31bfacing the non-sealed-fluid-side side surface53cof the mounting groove53is provided on the second backup ring31. By keeping the non-sealed-fluid-side end surface31bin contact with the non-sealed-fluid-side side surface53cof the mounting groove53from the beginning of the installation, the second backup ring31does not move in the mounting groove53toward the non-sealed-fluid side L and therefore does not press the first backup ring21even when the entire second backup ring31is pressed by the O-ring11. In addition, the outer periphery of the second backup ring31is not pressed by the O-ring11until the initial axial gap41formed between the outer periphery and the O-ring11disappears, so that the outer periphery of the second backup ring31does not press the first backup ring21. Thus, when inserting the sealing device1into the shaft hole52aof the housing52, the second backup ring31does not press the first backup ring21, so that the first backup ring21does not incur deformation that increases the outer diameter dimension d3thereof. Therefore, the situation in which the first backup ring21interferes with the opening peripheral edge of the shaft hole52aat the insertion does not take place, thus making it possible to restrain the damage to the first backup ring21attributable to the interference.

The slope21dof the first backup ring21is formed to have a concave arc-shaped surface in a sectional view, the slope31cof the second backup ring31is formed to have a convex arc-shaped surface in a sectional view, and the sealed-fluid-side end surface31dof the second backup ring31is formed to be a concave arc-shaped surface in a section view. These surfaces21d,31c, and31dare elastically deformed in shape such that the seal ring11is pressed against the second backup ring31when the high pressure P is applied to the O-ring11from the sealed-fluid side H, as illustrated inFIG. 2. At this time, the gap41disappears, thus enabling the O-ring11to press the second backup ring31(arrow A).

The second backup ring31that has been pressed elastically deforms such that the outer diameter dimension d4thereof increases, thus causing the second backup ring31to press the first backup ring21(arrow B).

The first backup ring21that has been pressed also elastically deforms such that the outer diameter dimension d3thereof increases and resultantly comes in contact with the shaft hole inner peripheral surface of the housing52or at least decreases the radial interval with respect to the shaft hole inner peripheral surface of the housing52(arrow C).

Thus, the first backup ring21, which elastically deforms outward in the radial direction as described above, exhibits the sealing action, so that the first backup ring21is expected to provide sealing effect.

The inner periphery of the second backup ring31that has been pressed by the O-ring11is pressed against the bottom surface53aof the mounting groove53in some cases (arrow D).

In such a case, the second backup ring31pressed against the bottom surface53aof the mounting groove53exhibits the sealing action, so that the sealing effect by the second backup ring31can be also expected.

As described above, not only the O-ring11but also the first backup ring21and the second backup ring31can exhibit the sealing action, thus enabling the sealing performance of the entire sealing device1to be improved. In comparison with a conventional right-triangle combination, the first backup ring (the hard backup ring)21can be enlarged in the axial direction without considering the rising-up during the installation, so that the rigidity of the first backup ring (the hard backup ring)21can be increased with a resultant higher pressure resistance.