Secondary seal

Abstract

Provided is a secondary seal capable of ensuring sealing performance even in a high-speed rotation environment. In a ring-shaped secondary seal (1) that seals between a rotary seal ring (4) and a holding member (3) that holds the rotary seal ring (4) and is sandwiched in the radial direction by the rotary seal ring (4) and the holding member (3), the area on the inner diameter side of an axial line passing through the center of the radial direction is smaller than the area on the outer diameter side of the axial line in an arbitrary cross-section in the circumferential direction.

Description

Technical Field

[0001] The present invention relates to secondary seals, for example to secondary seals for use in rotating seal rings. Background Art

[0002] In the field of shaft seals for rotating machinery such as automobiles and general industrial machinery, mechanical seals are used to prevent leakage of sealed fluids. Such mechanical seals have: a rotating shaft that is inserted through a housing; a stationary seal ring that is mounted on the housing; and a rotating seal ring that is mounted on the rotating shaft. The rotating seal ring rotates together with the rotating shaft, and the sliding surfaces of the stationary seal ring and the rotating seal ring rotate and slide relative to each other, which can prevent the sealed fluid arranged on one radial side of the sliding surface from leaking to the other radial side. In addition, usually, an elastic annular secondary seal is arranged between the rotating shaft and the rotating seal ring to seal the rotating shaft and the rotating seal ring.

[0003] For example, the mechanical seal shown in Patent Document 1 has a sleeve fixed to a shaft. The sleeve has a flange portion extending from the axial outer diameter side and a rotating ring holding portion extending from the outer diameter end of the flange portion in the axial direction. A rotating ring is arranged on the inner diameter side of the rotating ring holding portion. In addition, a retaining frame inserted through the rotating ring is fixed to the flange portion, and an O-ring is arranged between the rotating ring and the retaining frame.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2015 / 108107 (page 6, Figure 2 ) Summary of the invention

[0007] Problems to be solved by the invention

[0008] In the mechanical seal of Patent Document 1, an O-ring can be used to prevent the sealed fluid from leaking from between the rotating ring and the retainer to the atmosphere. However, in an environment where the shaft rotates at high speed, the O-ring is deformed in a manner that moves toward the outer diameter due to centrifugal force, so there is a concern that the inner periphery of the O-ring is separated from the retainer, causing leakage of the sealed fluid.

[0009] The present invention has been made in view of such problems, and an object of the present invention is to provide a secondary seal that can ensure sealing performance even in a high-speed rotation environment.

[0010] Means for solving problems

[0011] In order to solve the above-mentioned problems, the secondary seal of the present invention is annular, and is clamped in the radial direction by a rotating seal ring and a retaining component that retains the rotating seal ring, so as to seal between the rotating seal ring and the retaining component, wherein, with respect to the secondary seal, in any circumferential cross-section, the area on the inner diameter side of an axial line passing through the radial center is smaller than the area on the outer diameter side.

[0012] As a result, the secondary seal is less likely to deform in the radial direction when centrifugal force acts, and the inner diameter side of the secondary seal is less likely to float from the sealed surface. Therefore, the sealing performance can be ensured even in a high-speed rotation environment.

[0013] Alternatively, the secondary sealing member may be made of the same raw material.

[0014] This can prevent the occurrence of cracks and splitting.

[0015] The secondary seal may include an outer diameter bulging portion and an inner diameter bulging portion, each of the bulging portions is convexly curved in the radial direction, and a curvature radius of the inner diameter bulging portion is smaller than a curvature radius of the outer diameter bulging portion.

[0016] This makes it difficult for the secondary seal to deform radially, and reduces the contact area between the inner diameter side of the secondary seal and the sealed surface, so that the inner diameter side of the secondary seal is not easily lifted from the sealed surface, and the secondary seal is easy to insert during assembly.

[0017] A base portion may be provided between the inner diameter side bulging portion and the outer diameter side bulging portion, the base portion having an axial dimension greater than an axial dimension of the outer diameter side bulging portion in contact with the rotary seal ring or the holding member.

[0018] This can prevent the secondary seal from rolling in the axial direction when the secondary seal is inserted.

[0019] The base portion may have an axial dimension that is greater than a radial dimension of a portion between the rotary seal ring and the holding member that sandwiches the secondary seal.

[0020] Thus, the axial dimension of the secondary seal is larger than the radial dimension of the sandwiched space, so that the secondary seal can be prevented from rolling.

[0021] Alternatively, the secondary seal may be symmetrical in the axial direction.

[0022] As a result, when centrifugal force acts, the secondary seal deforms in a well-balanced manner, thereby improving the sealing performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1This is a longitudinal sectional view showing a mechanical seal using a secondary seal according to an embodiment of the present invention.

[0024] Figure 2 (a) is a perspective view of the assembled state of the rotary seal ring and the housing viewed from one side. Figure 2 (b) is a perspective view showing the assembled state of the rotary seal ring and the housing as viewed from the other side.

[0025] Figure 3 It is a cross-sectional view showing the structure of the secondary seal.

[0026] Figure 4 (a) to (c) are explanatory diagrams showing the process of assembling the rotary seal ring and the housing. DETAILED DESCRIPTION

[0027] Hereinafter, the mode for implementing the secondary seal of the present invention will be described based on examples.

[0028] Example

[0029] Reference Figures 1 to 4 The secondary seal of the embodiment is described below. Figure 1 The description will be made with the right side of the paper as one axial side and the left side of the paper as the other axial side.

[0030] The secondary seal 1 of the present embodiment is a secondary seal applied to a mechanical seal 10 used in the field of shaft sealing of rotating machines such as automobiles and general industrial machines.

[0031] like Figure 1 As shown, the mechanical seal 10 is an inner-type seal that seals the sealed fluid F that is intended to leak from the outer diameter side of the sliding surface to the inner diameter side, and mainly comprises: a rotating seal ring 4, which is arranged on the rotating shaft 2 via a housing 3 as a retaining component so as to be able to rotate together with the rotating shaft 2; and a stationary seal ring 6, which is fixed to the housing 5 of the installed equipment via a housing 7.

[0032] The rotating seal ring 4 and the stationary seal ring 6 are typically formed of a combination of SiC (hard material) and SiC (hard material) or a combination of SiC (hard material) and carbon (soft material), but are not limited thereto. Any sliding material that can be used as a sliding material for a mechanical seal can be used. In addition, as SiC, there are materials consisting of two or more phases with different components and compositions, represented by sintered bodies using boron, aluminum, carbon, etc. as sintering aids, such as SiC dispersed with graphite particles, reaction sintered SiC composed of SiC and Si, SiC-TiC, SiC-TiN, etc. As carbon, resin molded carbon, sintered carbon, etc. represented by carbon mixed with carbonaceous and graphite can be used. In addition, in addition to the above-mentioned sliding materials, metal materials, resin materials, surface modified materials (coating materials), composite materials, etc. can also be used.

[0033] like Figure 1 and Figure 2 As shown, the housing 3 is composed of a first plate portion 3a, a second plate portion 3b, a third plate portion 3c and a fourth plate portion 3d. The first plate portion 3a is fixed to the outer peripheral surface of the rotating shaft 2 and extends in an annular shape toward the outer diameter side. The second plate portion 3b extends in an annular shape from the outer diameter end portion of the first plate portion 3a toward the other axial side. The third plate portion 3c extends in an annular shape from the other side end portion of the second plate portion 3b toward the outer diameter side. The fourth plate portion 3d extends from the outer diameter end portion of the third plate portion 3c toward one axial side. The fourth plate portion 3d is a sheet-like shape that is approximately one-eighth of a circular arc when viewed in the axial direction, and is formed in a plurality of pieces separated in the circumferential direction. In the present embodiment, four pieces are formed.

[0034] A plurality of protrusions 4c extending in the outer diameter direction are formed along the circumferential direction on the outer periphery of the rotary seal ring 4. In this embodiment, four protrusions 4c are formed, and the fourth plate portion 3d of the housing 3 is inserted through adjacent protrusions 4c. Thus, the rotary seal ring 4 is connected to the housing 3 in a state where relative movement in the axial direction is allowed and movement in the circumferential direction is restricted.

[0035] In addition, an annular recess 4b is formed on the inner periphery of the rotary seal ring 4, which is open on the other axial side and the inner diameter side and has a stepped shape in cross-section. The secondary seal 1 is crimped and arranged between the annular recess 4b and the second plate portion 3b of the housing 3. Thus, it is possible to prevent the sealed fluid F from flowing out from between the annular recess 4b and the rotating shaft 2 to the atmosphere A side. In addition, the specific structure of the secondary seal 1 will be described in detail later.

[0036] like Figure 1 As shown, a bellows 8 is disposed between the stationary seal ring 6 and the housing 7. This prevents the sealed fluid F from flowing out from between the stationary seal ring 6 and the housing 7 to the atmosphere A side.

[0037] Furthermore, a spring 9 is disposed between the housing 7 and the bellows 8. As a result, the sliding surface 6a of the stationary seal ring 6 is pressed against the sliding surface 4a of the rotating seal ring 4, and the two seal rings slide in close contact with each other.

[0038] like Figure 3 As shown, the secondary seal 1 is annular and has a base 11, an outer diameter bulging portion 12 and an inner diameter bulging portion 13. The base 11, the outer diameter bulging portion 12 and the inner diameter bulging portion 13 are made of an elastomer of the same raw material. In addition, the raw material of the elastomer constituting the secondary seal 1 can be rubber or synthetic resin.

[0039] The base 11 is a generally rectangular shape that is long in the axial direction when viewed in cross section. The axial dimension of the base 11 is greater than the axial dimension of the contact portion between the secondary seal 1 and the rotary seal ring 4 or the axial dimension of the contact portion between the secondary seal 1 and the housing 3. The axial dimension is greater than the radial dimension between the rotary seal ring 4 and the housing 3 at the portion where the secondary seal 1 is clamped.

[0040] The outer diameter-side bulging portion 12 as the outer diameter portion of the secondary seal 1 has a curved shape that is convex from the axial center portion of the base portion 11 toward the outer diameter direction in a cross-sectional view.

[0041] The inner diameter-side bulging portion 13 as the inner diameter portion of the secondary seal 1 has a curved shape that is convex from the axial center portion of the base portion 11 toward the inner diameter direction in a cross-sectional view.

[0042] Extended portions 11 a and 11 b are provided on both axial sides of the base portion 11 so as to extend in the axial direction beyond the outer diameter side bulging portion 12 and the inner diameter side bulging portion 13 .

[0043] The curvature radius of the inner diameter side bulging portion 13 is smaller than the curvature radius of the outer diameter side bulging portion 12. That is, the inner diameter side bulging portion 13 is more tapered than the outer diameter side bulging portion 12.

[0044] Reference Figure 3 , with respect to the secondary seal 1, in any circumferential cross section, an imaginary axial line passing through the radial center (refer to Figure 3 The area on the inner diameter side (a single-dot chain line extending axially in the figure) is smaller than the area on the outer diameter side.

[0045] Furthermore, the secondary seal 1 has a line-symmetric shape in cross section with reference to an imaginary line γ that passes through the axial center and extends in the radial direction.

[0046] As described above, the curvature radius of the inner diameter side bulging portion 13 is smaller than the curvature radius of the outer diameter side bulging portion 12, so the cross-sectional area of ​​the outer diameter side bulging portion 12 is larger than the cross-sectional area of ​​the inner diameter side bulging portion 13. In addition, since the outer diameter side bulging portion 12 and the inner diameter side bulging portion 13 are made of the same material, the rigidity of the outer diameter side bulging portion 12 is higher than the rigidity of the inner diameter side bulging portion 13.

[0047] The radial rigidity k of the outer diameter side bulging portion 12 and the inner diameter side bulging portion 13 is N It can be obtained by the following formula (1).

[0048] k N =EA / L (1)

[0049] k N : Radial rigidity

[0050] E: Young's modulus

[0051] A: Cross-sectional area

[0052] L: Length

[0053] Therefore, the rigidity of the outer diameter bulging portion 12 of the same length is higher than that of the inner diameter bulging portion 13 , and therefore the radial deformation of the outer diameter bulging portion 12 is smaller than that of the inner diameter bulging portion 13 when a certain radial force acts.

[0054] Furthermore, the base 11 has a radial dimension longer than the outer diameter side bulging portion 12 and the inner diameter side bulging portion 13. The cross-sectional area of ​​the base 11 is larger than the cross-sectional area of ​​the outer diameter side bulging portion 12. That is, the rigidity of the base 11 is higher than the rigidity of the outer diameter side bulging portion 12. In addition, the cross-sectional area of ​​the base 11 is preferably about 2 to 30 times the cross-sectional area of ​​the outer diameter side bulging portion 12.

[0055] Next, use Figure 4 The assembly of the housing 3 and the rotary seal ring 4 will be described.

[0056] like Figure 4 As shown in (a), first, the secondary seal 1 is inserted into the annular recess 4b of the rotary seal ring 4 from the other axial side. At this time, almost no radial force acts on the secondary seal 1.

[0057] Then, if Figure 4 As shown in (b), the rotary seal ring 4 assembled with the secondary seal 1 is inserted from one axial side into the recess 3e formed by the second plate portion 3b, the third plate portion 3c, and the fourth plate portion 3d of the housing 3.

[0058] Thus, the secondary seal 1 is compressed in the radial direction between the rotary seal ring 4 and the second plate portion 3b of the housing 3. At this time, since the rigidity of the outer diameter side bulging portion 12 is higher than that of the inner diameter side bulging portion 13, the inner diameter side bulging portion 13 is greatly deformed compared to the outer diameter side bulging portion 12, and the outer diameter side bulging portion 12 is hardly deformed.

[0059] Furthermore, since the inner diameter bulged portion 13 is tapered compared to the outer diameter bulged portion 12, the contact area between the inner diameter bulged portion 13 and the second plate portion 3b can be reduced, thereby facilitating the insertion of the rotary seal ring 4 assembled with the secondary seal 1.

[0060] Furthermore, when the rotating seal ring 4 is inserted, the secondary seal 1 tries to roll in the axial direction due to the friction between the outer diameter side bulging portion 12 and the rotating seal ring 4 and the friction between the inner diameter side bulging portion 13 and the second plate portion 3b. However, the axial rolling of the secondary seal 1 is restricted because the extended portion 11a on one axial side of the secondary seal 1 contacts the inner circumferential surface of the rotating seal ring 4 constituting the annular recessed portion 4b and the extended portion 11b on the other axial side contacts the second plate portion 3b.

[0061] like Figure 4 As shown in (c), the assembly of the housing 3 and the rotating seal ring 4 is completed by inserting the rotating seal ring 4 into the recess 3e until the other axial end of the rotating seal ring 4 abuts against the third plate portion 3c. Here, in the part that the outer diameter side bulge 12 of the secondary seal 1 contacts (in other words, the part that the outer diameter side bulge 12 of the part that clamps the secondary seal 1 contacts), as long as there is a radial wall on the opposite side of the insertion direction of the secondary seal 1, even if the outer diameter side bulge 12 slides during insertion and the secondary seal 1 shifts, it can be pressed in by abutting against the radial wall. That is, in Figure 4 In the embodiment, it is sufficient that there is a radial wall of the annular recessed portion 4b.

[0062] As described above, the rigidity of the outer diameter side bulging portion 12 of the secondary seal 1 of this embodiment is higher than the rigidity of the inner diameter side bulging portion 13. When the secondary seal 1 is clamped in the radial direction between the rotating seal ring 4 and the housing 3, Figure 4 As shown in (c), the inner diameter side bulging portion 13 is greatly deformed compared to the outer diameter side bulging portion 12, and the outer diameter side bulging portion 12 is almost not deformed. Figure 1 As shown, even if centrifugal force acts on the secondary seal 1, the inner diameter side bulging portion 13 can be prevented from floating from the second plate portion 3b of the housing 3 as the sealed surface. Therefore, sealing performance can be ensured even in an environment where the rotating shaft 2 rotates at a high speed.

[0063] Furthermore, the secondary seal 1 is made of the same material, and the cross-sectional area of ​​the outer diameter bulged portion 12 is larger than that of the inner diameter bulged portion 13 . Therefore, the radial rigidity of the outer diameter bulged portion 12 can be made larger than that of the inner diameter bulged portion 13 .

[0064] Furthermore, since the outer diameter side bulging portion 12 and the inner diameter side bulging portion 13 are curved in a convex shape in the radial direction, and the curvature radius of the inner diameter side bulging portion 13 is smaller than that of the outer diameter side bulging portion 12, the outer diameter side bulging portion 12 is not easily deformed in the radial direction. Furthermore, the contact area between the inner diameter side bulging portion 13 and the second plate portion 3b can be reduced, so that the insertion operation of the rotary seal ring 4 assembled with the secondary seal 1 is easy.

[0065] Furthermore, a base portion 11 having a higher rigidity than the outer diameter side bulging portion 12 is provided between the outer diameter side bulging portion 12 and the inner diameter side bulging portion 13. Thus, the base portion 11 is hardly deformed when clamped in the radial direction between the rotary seal ring 4 and the housing 3, so that the radial thickness of the secondary seal 1 can be ensured, and the sealing performance can be improved.

[0066] Furthermore, since the base portion 11 has the extension portions 11 a and 11 b extending in the axial direction, the extension portions 11 a and 11 b can prevent the secondary seal 1 from rolling in the axial direction when the secondary seal 1 is inserted.

[0067] Furthermore, since the secondary seal 1 has a symmetrical shape in the axial direction with respect to the imaginary line γ, when centrifugal force acts, the secondary seal 1 deforms in a well-balanced manner, thereby providing good sealing performance.

[0068] As mentioned above, although the embodiment of the present invention is described with reference to the drawings, the specific structure is not limited to these embodiments, and even if there are changes and additions within the scope that does not depart from the gist of the present invention, they are also included in the present invention.

[0069] For example, in the above-mentioned embodiment, the secondary seal 1 is sandwiched between the rotating seal ring 4 and the housing 3 on the inner diameter side of the rotating seal ring 4, but it may be sandwiched between the rotating seal ring and the holding member on the outer diameter side of the rotating seal ring.

[0070] Furthermore, in the aforementioned embodiment, the outer diameter side bulge 12 and the inner diameter side bulge 13 are curved in shape, but are not limited to this. The outer diameter portion may also be rectangular, and the outer diameter portion may be formed integrally with the base. In addition to the above, or independently of the above, the inner diameter portion may also be rectangular. As long as the area on the inner diameter side of an axial line passing through the radial center in any circumferential cross-section is smaller than the area on the outer diameter side, it may be a free shape.

[0071] Furthermore, in the above-mentioned embodiment, the rigidity of the base portion 11 is higher than the rigidity of the outer diameter side bulging portion 12 , but the base portion may have the same rigidity as the outer diameter portion.

[0072] Furthermore, in the above-mentioned embodiment, the secondary seal 1 is exemplified in that the axial dimension is larger than the radial dimension, but the radial dimension may be larger than the axial dimension.

[0073] Furthermore, in the above-described embodiment, the spring 9 for maintaining the surface pressure between the sliding surfaces is provided on the stationary seal ring 6 side, but the spring 9 may be provided on the rotating seal ring 4 side.

[0074] Furthermore, in the aforementioned embodiment, the secondary sealing member 1 is exemplified as being symmetrical in shape with respect to a radial line, but may also be an asymmetrical shape.

[0075] Furthermore, in the above-mentioned embodiment, an inner type is exemplified for sealing the sealed fluid that leaks from the outer diameter side to the inner diameter side of the sliding surface, but an outer type may be used for sealing the sealed fluid that leaks from the inner diameter side to the outer diameter side of the sliding surface.

[0076] Description of symbols

[0077] 1: secondary seal; 2: rotating shaft; 3: housing (holding component); 4: rotating seal ring; 4a: sliding surface; 5: housing; 6: stationary seal ring; 6a: sliding surface; 9: spring; 10: mechanical seal; 11: base; 11a, 11b: extension part; 12: outer diameter side bulge; 13: inner diameter side bulge; A: atmosphere; F: sealed fluid.

Claims

1. A secondary seal, which is annular and is clamped in the radial direction by a rotating seal ring and a retaining member for retaining the rotating seal ring, so as to seal between the rotating seal ring and the retaining member, wherein: Regarding the secondary seal, in any cross section in the circumferential direction, an area on the inner diameter side of an axial line passing through the radial center is smaller than an area on the outer diameter side.

2. The secondary seal according to claim 1, wherein: The secondary seal is made of the same raw material.

3. The secondary seal according to claim 2, wherein: The secondary seal has an outer diameter bulging portion and an inner diameter bulging portion, each of the bulging portions is convexly curved in the radial direction, and a curvature radius of the inner diameter bulging portion is smaller than a curvature radius of the outer diameter bulging portion.

4. The secondary seal according to claim 3, wherein: A base portion is provided between the inner diameter side bulging portion and the outer diameter side bulging portion, and the base portion has an axial dimension that is larger than an axial dimension of the outer diameter side bulging portion in contact with the rotary seal ring or the holding member.

5. The secondary seal according to claim 4, wherein: The base portion has an axial dimension that is greater than a radial dimension between the rotary seal ring and the retaining member at a portion where the secondary seal is sandwiched.

6. The secondary seal according to any one of claims 1 to 5, wherein: The secondary seal is symmetrical in the axial direction.

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