Mechanical seal

Abstract

Provided is a mechanical seal capable of suppressing generation of vibration in a sealing ring.　A mechanical seal 1 is for separating a liquid space S1 and a gas space S2 from each other, and is composed of a stationary-side element S and a rotary-side element R that rotates relative to the stationary-side element S. The stationary-side element S is provided with a stationary sealing ring 11 that is attached to a housing 3 side, and the rotary-side element R is provided with a rotary sealing ring 21 that is inserted into the housing 3 and is attached to a rotary shaft 2 side. The mechanical seal is provided with a gas introduction texture 16 that is provided on a sliding surface 11d of the stationary sealing ring 11, and that causes gas A in the gas space S2 to be introduced in between the sliding surfaces 11d, 21a, and ejects the gas A that has changed to fine bubbles into the liquid space S1.

Description

Mechanical seal

[0001] The present invention relates to a mechanical seal, for example, a mechanical seal for sealing a rotating shaft.

[0002] Mechanical seals are used by being installed between the housing of a fluid equipment and a rotating shaft that passes through the housing. Specifically, mechanical seals have the function of preventing leakage of the sealed fluid by bringing the sliding surface of a stationary seal ring attached to the housing into sliding contact with the sliding surface of a rotating seal ring that is attached to the rotating shaft and rotates.

[0003] For example, a mechanical seal as disclosed in Patent Document 1 is composed of a stationary element and a rotating element, and includes a stationary seal ring attached to the housing and a rotary seal ring attached to the rotating shaft inserted into the housing, with the sliding surface of the rotary seal ring provided with a fluid inlet groove communicating with the sealed fluid space and a dynamic pressure generating groove communicating with the leakage space. In the mechanical seal of Patent Document 1, the sliding surfaces of the stationary seal ring and the rotary seal ring, which rotate relative to each other, slide against each other, and a liquid film of the sealed fluid introduced into the fluid inlet groove provides liquid lubrication between the sliding surfaces. Furthermore, dynamic pressure is generated by gas in the leakage space introduced into the dynamic pressure generating groove, forming a small gap between the sliding surfaces, and the gas in the leakage space introduced into the dynamic pressure generating groove prevents the sealed fluid between the sliding surfaces from leaking into the leakage space.

[0004] Japanese Patent No. 6444492 (pages 8-9, Figures 1-2)

[0005] However, in the mechanical seal of Patent Document 1, when the rotating seal ring rotates at high speeds, the sealing between the sliding surfaces can become slightly unstable. When the cause of this was investigated, it was found that the gas in the leakage side space that was introduced into the dynamic pressure generating grooves was ejected from between the sliding surfaces into the space on the sealed fluid side as a mass of large bubbles, which could cause vibrations in the stationary seal ring and the rotating seal ring.

[0006] The present invention has been made in view of these problems, and has as its object to provide a mechanical seal that can suppress the occurrence of vibration in the seal ring.

[0007] In order to solve the above problems, the mechanical seal of the present invention is composed of a stationary element and a rotating element that rotates relative to the stationary element, wherein the stationary element has a stationary seal ring attached to a housing, and the rotating element has a rotating seal ring inserted into the housing and attached to a rotating shaft, and the mechanical seal separates a liquid space and a gas space, and the mechanical seal has a gas introduction texture provided on the sliding surface of at least one of the stationary seal ring and the rotating seal ring, which introduces gas from the gas space between the sliding surfaces and sprays the gas in fine bubble form into the liquid space. According to this, when the rotating seal ring is rotating at high speed, the distance between the sliding surfaces is secured such that fine gas bubbles are sprayed into the liquid space by the gas introduction texture, thereby suppressing the generation of vibration in the seal ring.

[0008] The gas introduction texture may be an inclined groove, which separates the sliding surfaces by dynamic pressure generated in the inclined groove, thereby allowing gas to be introduced from the gas space into the space between the sliding surfaces with high efficiency.

[0009] The inclined groove may be in communication with the gas space, which allows gas to be introduced from the gas space into the space between the sliding surfaces with even higher efficiency.

[0010] A space may be formed between the stationary element and the rotating element, through which the liquid in the liquid space can pass, and the radial dimension of the space is smaller than the width of the sliding surface. In this way, the introduction of fine bubbles into the liquid in the narrow space reduces the viscosity of the liquid in the space, thereby reducing the resistance of the liquid to the rotating element.

[0011] The liquid may be water or an aqueous solution, which has low viscosity and therefore facilitates the generation of fine bubbles in the liquid.

[0012] The gas may be air, which has low solubility and therefore the fine bubbles are less likely to disappear in the liquid, allowing the cleaning effect to be maintained for a long period of time.

[0013] The present invention relates to a mechanical seal having a rotary seal ring and a stationary seal ring, and is a mechanical seal having a rotary seal ring and a stationary seal ring.

[0014] The inventors discovered that by setting the relative peripheral speed of the sliding surfaces of the seal ring and the distance between the sliding surfaces within a predetermined range, fine bubbles can be generated between the sliding surfaces, thereby suppressing vibration of the seal ring and ensuring even more stable sealing performance.

[0015] The following describes embodiments of the mechanical seal according to the present invention. Note that the term "fine bubbles" used in this specification includes microbubbles with diameters of 1 to 100 μm and ultrafine bubbles with diameters of less than 1 μm.

[0016] A mechanical seal provided between a rotating shaft of a rotating device and a housing surrounding the rotating shaft according to an embodiment will be described with reference to Figures 1 to 3. In the following description, the left side of Figure 1 will be referred to as the left side of the mechanical seal, and the right side of the page will be referred to as the right side of the mechanical seal.

[0017] 1, the mechanical seal 1 is an outside-type mechanical seal that seals against a sealed fluid F that attempts to leak from the inner diameter side to the outer diameter side. The space on the inner diameter side of the stationary seal ring 11 and the rotary seal ring 21 will be described as a liquid space S1 on the sealed fluid F side, and the space on the outer diameter side of the stationary seal ring 11 and the rotary seal ring 21 will be described as a gas space S2 on the atmosphere A side. In this embodiment, the sealed fluid F will be described as water or an aqueous solution.

[0018] The mechanical seal 1 of this embodiment is composed of a rotating element R and a stationary element S, and the sliding surfaces 11d, 21a of the rotating seal ring 21 and the stationary seal ring 11, which slide against each other, separate the liquid space S1 and the gas space S2, thereby preventing the sealed fluid F from leaking from the liquid space S1 to the gas space S2. In this embodiment, even if air A mixes with the sealed fluid F in the liquid space S1 from the gas space S2, there is no adverse effect on the sealed fluid F or the rotating equipment.

[0019] The rotating element R is mainly composed of a sleeve 20 fixed to the rotating shaft 2, a rotary seal ring 21 held by the sleeve 20, and a cup gasket 22 that seals between the sleeve 20 and the rotary seal ring 21.

[0020] The sleeve 20 is an annular member with a generally J-shaped cross section that opens to the right, and is formed by pressing and bending a thin metal plate. The material and processing method of the sleeve 20 are not limited, and it may be a resin molded product, for example.

[0021] The sleeve 20 also has a cylindrical base 20a that is fitted onto the rotating shaft 2 and extends axially along the outer peripheral surface of the rotating shaft 2, an annular outward flange portion 20b that extends radially outward from the left end of the base 20a, and a cylindrical extension portion 20c that extends rightward from the outer diameter end of the outward flange portion 20b.

[0022] The rotary seal ring 21 has a generally rectangular cross section, and its right surface, i.e., the surface facing the stationary seal ring 11, is a flat sliding surface 21a. In this embodiment, this flat sliding surface 21a does not have any recesses such as grooves.

[0023] The cup gasket 22 is an annular member with an L-shaped cross section, and is made of an elastically deformable synthetic resin or rubber material. The cup gasket 22 is attached in a sandwiched state between the outer peripheral surface of the base portion 20 a of the sleeve 20 and the inner peripheral surface 21 b of the rotary seal ring 21, and between the outward flange portion 20 b of the sleeve 20 and the back surface 21 c of the rotary seal ring 21, thereby sealing the gap between the sleeve 20 and the rotary seal ring 21.

[0024] The stationary side element S is mainly composed of a stationary side case 10 fixed to the housing 3, a stationary seal ring 11 held in the stationary side case 10, a bellows 12 that seals between the stationary side case 10 and the stationary seal ring 11, a spring 13 that is held in the stationary side case 10 and urges the stationary seal ring 11 toward the rotary seal ring 21, a fixing member 14 that presses and fixes the bellows 12 to the stationary side case 10, and a retainer 15 for holding the spring 13.

[0025] The stationary seal ring 11 is key-fitted to the stationary case 10, allowing relative movement in the axial direction, but restricting movement in the rotational direction. The means for restricting movement of the stationary seal ring 11 in the rotational direction may be other means, such as an engagement pin.

[0026] The stationary case 10 is an annular member with a generally U-shaped cross section that opens to the left and is formed by pressing and bending a thin metal plate. The material and processing method of the stationary case 10 are not limited, and it may be a resin molded product, for example.

[0027] The stationary side case 10 also has a cylindrical base 10a that is fitted into the housing 3 and extends axially along the inner surface of the housing 3, an annular inward flange portion 10b that extends radially inward from the right end of the base 10a, and a cylindrical extension portion 10c that extends leftward from the inner diameter end of the inward flange portion 10b.

[0028] The bellows 12 is an annular member made of an elastically deformable synthetic resin material or rubber material, and has a pressing portion 12a arranged axially apart on the back surface 11e side of the stationary seal ring 11, an attachment portion 12b arranged on the outer diameter side of the stationary seal ring 11, and a connecting portion 12c connecting the pressing portion 12a and the attachment portion 12b.

[0029] The mounting portion 12 b of the bellows 12 is mounted by being sandwiched between the inner peripheral surface of the retainer 15 and the outer peripheral surface 11 c of the stationary seal ring 11 , thereby sealing the gap between the retainer 15 and the stationary seal ring 11 .

[0030] The retainer 15 is an annular member that opens to both the left and right and is formed by pressing and bending a thin metal plate. The material and processing method of the retainer 15 are not limited, and it may be a resin molded product, for example.

[0031] The fixing member 14 is a ring-shaped member made of metal with an approximately L-shaped cross section, and is fitted onto the pressing portion 12a of the bellows 12. By pressing the pressing portion 12a in the inward radial direction, the space between the fixing member 14 and the stationary case 10 is sealed.

[0032] The stationary seal ring 11 has a base 11a and an annular protrusion 11b that protrudes leftward from the inner diameter side of the base 11a. The left surface of the protrusion 11b, i.e., the surface facing the sliding surface 21a of the rotary seal ring 21, is a sliding surface 11d on which a gas-introducing texture is provided.

[0033] 2, a plurality of inclined grooves 16 (20 in this embodiment) are provided in the circumferential direction as a gas introduction texture on the outer diameter side, i.e., the gas space S2 side, of the sliding surface 11d of the stationary seal ring 11. The rotating seal ring 21, which is the mating sliding ring, rotates counterclockwise relative to the stationary seal ring 11, as shown by the solid arrow.

[0034] The portion of the sliding surface 11d other than the inclined groove 16 is a flat land 17 arranged on the same plane. The flat surface of the land 17 functions as a surface that substantially slides against the sliding surface 21a of the rotary seal ring 21.

[0035] In this embodiment, the radial dimensions of the sliding surface 11d of the stationary seal ring 11 on which the gas-introducing texture is formed are preferably an inner radius of 1.0 to 2.0 cm and an outer radius of 1.2 to 2.5 cm, and more preferably an inner radius of 1.5 to 1.6 cm and an outer radius of 1.8 to 1.9 cm. The sliding surface width of the sliding surface 11d, i.e., the dimension obtained by subtracting the inner radius from the outer radius of the sliding surface 11d, is preferably 0.2 to 0.5 cm, and more preferably 0.3 to 0.4 cm.

[0036] The inclined groove 16 communicates with the gas space S2 on the outer diameter side and extends from the outer edge of the sliding surface 11 d to the inner diameter side. More specifically, the inclined groove 16 communicates with the gas space S2 and extends in an arc shape from the outer diameter side to the inner diameter side, i.e., from the gas space S2 side to the liquid space S1 side, while being inclined toward the downstream side in the relative rotation direction, i.e., counterclockwise, with a component. The inclined groove 16 in this embodiment is a so-called spiral groove.

[0037] In this embodiment, the inclined groove 16 is formed to a constant depth in the circumferential direction. The inclined groove 16 is only required to have the function of directing the atmosphere A in the gas space S2 to the inner diameter side and generating a positive pressure at the closed end 16A, and is not limited to extending in an arc like a spiral groove, but may also extend in a straight line.

[0038] Next, the operation of the stationary seal ring 11 and the rotary seal ring 21 during relative rotation will be described.

[0039] First, when the rotary seal ring 21 is not rotating, a small amount of sealed fluid F enters between the sliding surface 11d of the stationary seal ring 11 and the sliding surface 21a of the rotary seal ring 21 from the liquid space S1 side. Also, atmospheric air A flows into the inclined groove 16 provided on the gas space S2 side.

[0040] Furthermore, since the spring 13 (see FIG. 1) biases the stationary seal ring 11 toward the rotary seal ring 21, the sliding surfaces 11d and 21a are in contact with each other, and almost no sealed fluid F that has entered between the sliding surfaces 11d and 21a leaks into the gas space S2.

[0041] When the rotating seal ring 21 starts to rotate relative to the stationary seal ring 11 at a low speed, i.e., when the rotating seal ring 21 is rotating at a low speed, the sealed fluid F that has entered between the sliding surfaces 11d and 21a moves in the rotational direction of the rotating seal ring 21 due to shear with the sliding surface 21a.

[0042] Meanwhile, air A in the inclined groove 16 moves toward the closed end 16A of the inclined groove 16 due to shear with the sliding surface 21a. Then, air A that has moved toward the closed end 16A of the inclined groove 16 flows out from the closed end 16A and its vicinity to between the sliding surfaces 11d and 21a. At the open end 16B of the inclined groove 16, air A is drawn into the inclined groove 16 from the gas space S2.

[0043] At this time, since the relative rotational speed between the rotating seal ring 21 and the stationary seal ring 11 is low, the atmosphere A does not become sufficiently dense within the inclined groove 16, so a high positive pressure is not generated, and almost no force acts to separate the sliding surfaces 11d, 21a.

[0044] The air A that flows out from the closed end 16A of the inclined groove 16 and its vicinity to the space between the sliding surfaces 11d and 21a is guided to move toward the inner diameter side, but is pushed back toward the outer diameter side by the pressure of the high-pressure sealed fluid F that flows from the liquid space S1 into the space between the sliding surfaces 11d and 21a.

[0045] When the relative rotational speed of the rotary seal ring 21 increases and exceeds a predetermined rotational speed, a large amount of air A moves toward the closed end 16A of the inclined groove 16, increasing the pressure at and near the closed end 16A of the inclined groove 16. In other words, a positive pressure is generated at and near the closed end 16A of the inclined groove 16.

[0046] At this time, the positive pressure generated at and near the closed end 16A of the inclined groove 16 separates the sliding surfaces 11d and 21a, forming a liquid film of the sealed fluid F on the inner diameter side between the sliding surfaces 11d and 21a, and forming a boundary with the atmosphere A introduced from the gas space S2 on the outer diameter side by the inclined groove 16.

[0047] Furthermore, since the sealed fluid F, which is a liquid, has a higher viscosity than the atmosphere A, the atmosphere A between the sliding surfaces 11d and 21a is less likely to enter the liquid space S1, making it easier to maintain the boundary between the liquid film of the sealed fluid F and the atmosphere A.

[0048] When the relative rotational speed of the rotating seal ring 21 increases further and the rotational speed reaches 4000 rpm or more, preferably 5000 rpm or more, the pressure of the sealed fluid F between the sliding surfaces 11d, 21a decreases due to the high-speed flow of the sealed fluid F, which is a liquid, between the sliding surfaces 11d, 21a caused by the sliding of the sliding surfaces 11d, 21a of the stationary seal ring 11 and the rotating seal ring 21, and the atmospheric air A introduced between the sliding surfaces 11d, 21a by the inclined grooves 16 is drawn into the liquid film of the sealed fluid F, and the sudden change in pressure breaks up the bubbles, thereby converting the atmospheric air A into fine bubbles.

[0049] In this way, when the rotating seal ring 21 is rotating at high speed, the inclined grooves 16 (see FIG. 2) formed in the sliding surface 11d of the stationary seal ring 11 introduce air A from the gas space S2 between the sliding surfaces 11d and 21a (see the solid arrow), and the air A is converted into fine bubbles in the liquid film between the sliding surfaces 11d and 21a, making it possible to eject fine bubbles B of the air A from between the sliding surfaces 11d and 21a into the liquid space S1 (see FIG. 3). Note that the fine bubbles B are air bubbles with a diameter of 100 μm or less.

[0050] Furthermore, when the rotating seal ring 21 is rotating at high speed, the distance between the sliding surfaces 11d and 21a is preferably larger than the diameter of the fine bubbles B injected into the liquid space S1, specifically, preferably 100 μm or less. That is, the seal load of the mechanical seal 1 is more preferably set so that the distance between the sliding surfaces 11d and 21a is 0.1 μm to 100 μm, preferably 0.2 μm to 30 μm, in balance with the dynamic pressure due to the inclined grooves 16 serving as the gas introduction texture when the rotating seal ring 21 is rotating at high speed. Note that the distance between the sliding surfaces 11d and 21a and the size of the fine bubbles B are shown in a distorted manner in Figure 3.

[0051] As explained above, in the mechanical seal 1 of this embodiment, the inclined grooves 16 are provided on the sliding surface 11d of the stationary seal ring 11 and serve as a gas introduction texture that introduces atmospheric air A from the gas space S2 between the sliding surfaces 11d and 21a and sprays the finely bubbled atmospheric air A into the liquid space S1. Therefore, when the rotating seal ring 21 is rotating at high speeds, the inclined grooves 16 stably ensure a distance between the sliding surfaces 11d and 21a that allows fine bubbles B of atmospheric air A to be sprayed into the liquid space S1. This makes it possible to suppress the occurrence of vibrations in the stationary seal ring 11 and the rotating seal ring 21 and ensure stable sealing between the sliding surfaces 11d and 21a.

[0052] Furthermore, by separating the sliding surfaces 11d and 21a by the dynamic pressure generated in the inclined groove 16, the air A can be introduced from the gas space S2 into the gap between the sliding surfaces 11d and 21a with high efficiency.

[0053] Furthermore, since the inclined groove 16 communicates with the gas space S2, the air A can be introduced from the gas space S2 into the gap between the sliding surfaces 11d and 21a with even higher efficiency.

[0054] Furthermore, an annular space S3 through which fine bubbles B ejected from between the sliding surfaces 11d, 21a pass is formed between the inner peripheral surface of the extension portion 10c of the stationary case 10 constituting the stationary element S and the outer peripheral surface of the base portion 20a of the sleeve 20 constituting the rotating element R. Space S3 is formed as a space whose radial dimension, through which the sealed fluid F of the liquid space S1 can pass, is smaller than the sliding surface width of the sliding surface 11d described above. As a result, fine bubbles B are introduced into the liquid (i.e., the sealed fluid F) in the narrow space S3, reducing the viscosity of the liquid in the space S3 and thereby reducing the resistance of the liquid to the rotating element R.

[0055] Furthermore, the fine bubbles B hardly combine with other fine bubbles B in the liquid and are unlikely to form large bubbles, so the resistance of the liquid to the rotating element R is likely to be maintained at a low level.

[0056] Furthermore, a separate fine bubble generator may be provided in the space S3 to allow the liquid in the space S3 to contain more fine bubbles B, thereby further reducing the resistance of the liquid to the rotating element R.

[0057] In addition, in this embodiment, the sealed fluid F is water or an aqueous solution, which is a liquid with low viscosity, and therefore fine bubbles B are easily generated in the liquid.

[0058] Furthermore, in this embodiment, the gas is air A, and since the solubility is low, the fine bubbles B are less likely to disappear in the liquid, and the cleaning effect and the viscosity reduction effect described above can be exerted by the fine bubbles B for a long period of time.

[0059] Furthermore, since fine bubbles B can be generated by the mechanical seal 1 that separates the liquid space S1 and the gas space S2 and ensures airtightness, there is no need to provide a separate fine bubble generator, and the rotating equipment can be made smaller.

[0060] In addition, for example, the base 20a of the sleeve 20 constituting the rotating side element R may be provided with irregularities so that the fine bubbles B passing through the space S3 can be efficiently diffused.

[0061] Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention also includes modifications and additions that do not deviate from the gist of the present invention.

[0062] For example, in the above embodiment, an outside-type mechanical seal has been described as an example, but the present invention is not limited to this, and an inside-type mechanical seal may also be used.

[0063] In addition, in the above embodiment, the gas introduction texture is described as being provided on the sliding surface of the stationary seal ring, but this is not limited to this. The gas introduction texture may be provided on the sliding surface of the rotary seal ring, or may be provided on the sliding surfaces of both the stationary seal ring and the rotary seal ring.

[0064] Furthermore, in the above embodiment, the gas introduction texture is described as being an inclined groove, but this is not limited to this, and the gas introduction texture may be a dynamic pressure generating groove other than an inclined groove, as long as it can introduce gas from the gas space between the sliding surfaces.

[0065] Furthermore, the inclined groove does not have to communicate with the gas space.

[0066] Furthermore, in the above embodiment, the liquid in the liquid space (i.e., the sealed fluid F) is described as being water or an aqueous solution, but this is not limited thereto, and the liquid may be a non-aqueous solution, for example, using an organic solvent, as long as it is capable of generating fine bubbles.

[0067] In the above embodiment, the gas in the gas space is the atmosphere A, but this is not limiting. Any gas may be selected as long as it has a low solubility in the liquid in the liquid space and does not adversely affect the sealed fluid or the rotating equipment when dissolved in the liquid.

[0068] REFERENCE SIGNS LIST 1 Mechanical seal 2 Rotating shaft 3 Housing 10 Stationary side case 11 Stationary seal ring 11d Sliding surface 12 Bellows 13 Spring 14 Fixed member 15 Retainer 16 Inclined groove (gas introduction texture) 16A Closed end 16B Open end 17 Land 20 Sleeve 21 Rotating seal ring 21a Sliding surface 22 Cup gasket A Atmosphere (gas) B Fine bubbles F Sealed fluid (liquid) R Rotating side element S Stationary side element S1 Liquid space S2 Gas space S3 Space

Claims

1. A mechanical seal comprising a stationary element and a rotating element that rotates relative to the stationary element, wherein the stationary element has a stationary seal ring attached to the housing side, and the rotating element has a rotating seal ring inserted into the housing and attached to the rotating shaft side, which separates a liquid space and a gas space, and which has a gas introduction texture provided on the sliding surface of at least one of the stationary seal ring and the rotating seal ring, which introduces gas from the gas space between the sliding surfaces and sprays the gas in fine bubbles into the liquid space.

2. The mechanical seal according to claim 1, wherein the gas-introducing texture is an inclined groove.

3. A mechanical seal according to claim 2, wherein said inclined groove communicates with said gas space.

4. A mechanical seal according to claim 1, wherein a space is formed between the stationary element and the rotating element, the radial dimension of which is smaller than the width of the sliding surface and through which the liquid in the liquid space can pass.

5. A mechanical seal according to any one of claims 1 to 4, wherein the liquid is water or an aqueous solution.

6. A mechanical seal according to any one of claims 1 to 4, wherein the gas is atmospheric air.

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