JP2018071606A - mechanical seal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mechanical seal which can suppress the damage of a slide face caused by sedimentation by reducing the accumulation of substances contained in fluid even if used in the fluid containing a component which is liable to cause a chemical reaction by heat such as silicate, and can prevent the generation of noise such as streaking.SOLUTION: A mechanical seal comprises a rotating ring 11 fixed to a rotating shaft side, and a fixed ring 21 arranged at a housing 3 side so as to oppose the rotating ring 21. The mechanical seal seals a sealed fluid while relatively rotating a sealing end face clearance S being an opposing end face between the rotating ring 11 and the fixed ring 21, and also comprises a water repellent part in which water repellent treatment is applied to a high-pressure fluid side rather than the sealing end face clearance S at least at either of the rotating ring 11 and the fixed ring 12.SELECTED DRAWING: Figure 1

Description

  The present invention comprises a rotating ring fixed on the rotating shaft side and a fixing ring disposed on the housing side so as to face the rotating ring, and is a sealed end face between the rotating ring and the fixed ring The present invention relates to a mechanical seal configured to seal a sealed fluid while relatively rotating between end faces.

  Conventionally, as a kind of mechanical seal, as shown in FIG. 8, it can rotate integrally with the rotary shaft 70 via a sleeve 71 and a cup gasket 72 on the rotary shaft 70 side for driving a pump impeller (not shown). A mating ring 73 as a rotating ring provided in a state, and a seal ring 75 as a stationary ring provided via a bellows 77 in the cartridge 76 in a non-rotating state and axially movable in a pump housing 79. And sealing the fluid to be sealed while relatively rotating sliding surfaces which are opposed end surfaces of the mating ring 73 and the seal ring 75 (see, for example, Patent Document 1).

  Usually, ceramics which are hydrophobic materials such as silicon carbide and alumina having excellent wear resistance are used as the matting ring 73, and carbon which is a hydrophobic material having excellent self-lubricating properties is used as the seal ring 75. ing. However, when the hydrophobic materials slide with each other, the sliding surfaces may be too close to each other, and water may not enter the sliding surfaces, resulting in a phenomenon of “squealing”. Therefore, in order to prevent “squeal”, a coating of hydrophilic material is applied to the sliding surface and outer peripheral area of the ceramics, which is a hydrophobic material, and the sliding surface is combined with a hydrophilic material and a hydrophobic material. Some improve the slidability (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 2000-74226 (third page, FIG. 2) Japanese Patent Laying-Open No. 2004-183810 (6th page, FIG. 1)

  In the mechanical seal of Patent Document 1, carbon is used as the material of the seal ring 75. In addition to self-lubricating properties, carbon has moderate irregularities on its surface, so it can hold a liquid film due to the sealed fluid between the sliding surface of the mating ring 73 and has excellent lubrication characteristics. Demonstrate. However, while carbon exhibits excellent slidability, components of the sealing liquid such as silicate cause a chemical change due to sliding heat generation and accumulate on the unevenness of the carbon surface, and the deposit peels off and slides. May cause damage to the sliding surface and reduce the sealing function. Further, since the mating ring 73 is formed by sintering ceramics such as silicon carbide, the surface of the mating ring 73 has minute irregularities, and substances contained in the liquid are deposited on the irregularities. The moving surface may be damaged and the sealing function may be deteriorated.

  In the mechanical seal of Patent Document 2 as well, hydrophobic carbon is used as the rotation-side sliding member, so that the constituent components of the sealing liquid such as silicate cause chemical changes due to sliding heat generation and accumulate on the unevenness of the carbon surface. In addition, the sliding surface may be damaged by the deposit. In addition, when a hydrophilic coating is coated on the sliding surface of the fixed-side sliding member and the outer diameter side of the sliding surface, the hydrophilic coating makes it easy to get wet with the fluid to be sealed. The deposit tends to be easily deposited, and the deposit may damage the sliding surface and reduce the sealing function.

  The present invention has been made paying attention to such problems, and even if a mechanical seal is used in a sealing liquid containing a component that easily undergoes a chemical change due to heat, such as silicate, the substance contained in the liquid A mechanical seal that can reduce the accumulation of noise and prevent the sealed end surface, which is the opposite end surface of the rotating ring and stationary ring, from being damaged by deposits, and can also prevent the generation of abnormal noise such as squealing The purpose is to provide.

In order to solve the above problems, the mechanical seal of the present invention is
A rotating ring fixed on the rotating shaft side, and a fixed ring disposed on the housing side so as to face the rotating ring,
A mechanical seal configured to seal a sealed fluid while relatively rotating between sealed end faces which are opposed end faces of the rotating ring and the fixed ring,
At least one of the rotating ring and the stationary ring is provided with a water-repellent part that is water-repellent on the high-pressure fluid side than between the sealed end faces.
According to this feature, the water-repellent portion that is water-repellent on the high-pressure fluid side than between the sealed end surfaces can prevent a substance contained in the sealed fluid from flowing into between the sealed end surfaces. Damage can be prevented.

The mechanical seal of the present invention is
A gap is provided on the high-pressure fluid side from between the sealed end faces, and the axial gap u of the gap is set in a range of at least 0 <u <kT / P.
Where u is the axial gap of the gap, P is the pressure of the sealed fluid, and T is the surface tension between the water repellent portion and the sealed fluid.
According to this feature, it is possible to limit the axial gap of the gap portion and limit the entry of the sealed fluid between the sealed end surfaces, thereby preventing the sealed end surface from being damaged by the substance contained in the sealed fluid. Can do.

The mechanical seal of the present invention is
An inner radius and an outer radius of the gap are set by r2 ² −r1 ² = 2P / ρn ² ω ² .
Where r1 is the inner radius of the gap, r2 is the outer radius, P is the sealed fluid pressure, ρ is the sealed fluid density, ω is the angular velocity of the rotating ring, and n is a coefficient in the range of 0 <n <1. It is.
According to this feature, it is possible to limit the diameter of the gap portion and restrict the entry of the sealed fluid between the sealed end surfaces, and thus prevent the sealed end surface from being damaged by the substance contained in the sealed fluid. it can.

The mechanical seal of the present invention is
The axial gap of the gap portion is characterized by gradually narrowing toward the sealed end face.
According to this feature, a gap portion having a minute axial gap can be easily formed between the rotating ring and the fixed ring.

The mechanical seal of the present invention is
The water repellent part is characterized in that a contact angle with a fluid to be sealed is larger than 90 °.
According to this feature, the contact angle with the sealed fluid is larger than 90 °, and the entry of the sealed fluid between the sealed end faces can be restricted, so that the substance contained in the sealed fluid is less likely to adhere, It is possible to prevent a decrease in water repellency due to damage, peeling, etc., and to improve durability.

The mechanical seal of the present invention is
The sealed end face includes a dynamic pressure generating mechanism that generates dynamic pressure by relative rotation between the rotating ring and the fixed ring.
According to this feature, even if the water-repellent part that is water-repellent on the high-pressure fluid side than between the sealed end faces prevents the fluid to be sealed from flowing into the sealed end faces, the sealed end faces Since a fluid film can be formed by generating a positive pressure with the stationary ring, it is possible to prevent abnormal noise such as squealing.

1 is a longitudinal sectional view showing a mechanical seal according to Embodiment 1. FIG. It is a longitudinal cross-sectional view which shows the sealing end surface which is an opposing end surface of the mating ring of Example 1, and the water-repellent part formed in the high pressure fluid side rather than this sealing end surface. (A) is an AA arrow line view of FIG. 2, Comprising: The figure which shows the sealing end surface and water-repellent part of a mating ring, (b) is a figure which shows the DD cross section of (a). (A) is a BB arrow line view of FIG. 2, Comprising: The figure which shows the sealing end surface and water-repellent part of a seal ring, (b) is a figure which shows the EE cross section of (a). It is a figure which shows the modification of the mechanical seal which concerns on Example 1, (a) makes the outer-diameter side of the sealing end surface of a seal ring a flat cyclic | annular inclined surface, (b) is the sealing end surface of a seal ring. The outer diameter side is an annular inclined surface made of a convex curved surface. 2A and 2B are diagrams illustrating a configuration of a mechanical seal according to the first embodiment, in which FIG. 2A is an enlarged view of a portion C in FIG. 2, and FIG. (C) is a figure which shows the state by which the seal surface is not water-repellent-treated in (a). It is a figure which shows the mating ring of the mechanical seal which concerns on Example 2, and is a figure which shows the dynamic positive pressure generation mechanism provided in the sealing end surface of the mating ring. It is a longitudinal cross-sectional view which shows the mechanical seal of the prior art 1.

  EMBODIMENT OF THE INVENTION The form for implementing the mechanical seal which concerns on this invention is demonstrated based on an Example.

  A mechanical seal according to the first embodiment will be described with reference to FIGS. 1 to 6. In the first embodiment, an inside type mechanical seal that seals a fluid that leaks from the outer circumference of the sealing end surface S toward the inner circumference direction will be described as an example, but the present invention may be either an inside type or an outside type. It can also be applied to mechanical seals of the type. In the first embodiment, the mating ring 11 is described as a rotating ring and the seal ring 21 is described as a stationary ring. However, the mating ring 11 may be a stationary ring and the sealing ring 21 may be a rotating ring. In FIG. 1, the outer peripheral side of the sealing end surface S will be described as a high-pressure fluid side, and the inner peripheral side will be described as a low-pressure fluid side (for example, the atmosphere side).

  FIG. 1 is a longitudinal sectional view showing an example of a mechanical seal, and is provided in a state of being integrally rotatable on a rotating shaft 2 side for driving a high pressure fluid side rotating body (for example, a pump impeller, not shown). The rotation side cartridge 10 and the fixed side cartridge 20 fixed to the housing 3 in a non-rotating state. The mating ring 11 disposed on the rotation side cartridge 10 and the seal ring 21 disposed on the stationary side cartridge 20 rotate relative to each other at the sealing end surface S, so that the sealed fluid is removed from the outer periphery of the rotation shaft 2. It is intended to prevent outflow to the atmosphere side. Further, as shown in FIG. 2, a water repellent portion Hr is provided on the high pressure fluid side of the sealed end surface S of the mating ring 11, and a water repellent portion Hs is provided on the high pressure fluid side of the sealed end surface S of the seal ring 21. An annular gap portion Ncs is formed between the water repellent portion Hr of the mating ring 11 and the water repellent portion Hs of the seal ring 21. Hereinafter, configurations of the rotation side cartridge 10 and the fixed side cartridge 20 will be described.

  The rotation side cartridge 10 mainly includes a rotation side sleeve 12 fixed to the rotation shaft 2, a cup gasket 13 that rotates together with the rotation side sleeve 12, and a mating ring 11.

  As shown in FIG. 1, the rotation-side sleeve 12 is an annular member having a substantially U-shaped cross section, and is an inner cylinder portion 12a that is press-fitted and fixed to the rotation shaft 2, and extends radially outward from one end of the inner cylinder portion 12a. It is comprised from the wall part 12b provided, and the outer cylinder part 12c extended in the axial direction by the side of the inner cylinder part 12a from the outer diameter side edge part of this wall part 12b. The opening of the rotating sleeve 12 is fixed to the rotating shaft so as to face the fixed cartridge 20 side.

  As shown in FIGS. 2 and 3, the mating ring 11 is made of an annular member having a substantially rectangular cross section, and the mating ring 11 has various mechanical properties such as silicon carbide and alumina having high mechanical strength and excellent wear resistance. Or made of cemented carbide. On the front side of the mating ring 11 facing the seal ring 21, there is provided a seal surface Rs that is finished smoothly and functions as a sealed end surface S. In order to cope with the case where the rotation centers of the mating ring 11 and the seal ring 21 do not exactly coincide with each other, the seal surface Rs is set to be larger than the radial width of the sealing end surface S of the seal ring 21 described later. The sealing end face margin is formed by increasing the outer diameter and decreasing the inner diameter. In the present embodiment, the radial width of the sealing surface Rs of the mating ring 11 is formed larger than the radial width of the sealing end surface S of the seal ring 21, but the present invention is limited to this. Of course, the present invention can be applied to the reverse case. Further, as shown in FIG. 3, two notch recesses 19 are formed in the outer peripheral portion of the mating ring 11, and the above-described rotation-side sleeve 12 is engaged with the notch recess 19, and the mating ring 11 And the rotary sleeve 12 rotate together.

  As shown in FIGS. 2 and 3, the water repellent water repellent treatment is applied to the high pressure fluid side of the sealing surface Rs of the mating ring 11, that is, the outer diameter side end surface 11 a and the outer peripheral surface 11 b of the mating ring 11. Part Hr is provided. The outer diameter side end surface 11a of the mating ring 11 is formed lower by the thickness t of the water repellent part Hr than the seal surface Rs toward the back side. As will be described later, a water-repellent portion Hr is formed on the outer diameter side end surface 11a to a thickness t or more by coating or the like, and the water-repellent portion Hr and the seal surface Rs having no water-repellent portion Hr are finished flush with each other. It is done. Thereby, the thickness of the water repellent part Hr is ensured, durability can be improved, and a margin for sealing end surface between the mating ring 11 and the seal ring 21 can be secured. Furthermore, a water repellent portion Hr is also disposed on the outer peripheral surface 11 b of the mating ring 11. The water repellent part Hr is made of a resin or powder such as Teflon-based (“Teflon” is a registered trademark), silicon-based, and the like, by coating the outer diameter side end surface 11 a and the outer peripheral surface 11 b of the mating ring 11. It is formed. 2 and 3, the water repellent portion Hr is provided on both the outer diameter side end face 11a and the outer peripheral face 11b of the mating ring 11, but is provided only on the outer diameter side end face 11a. Also good.

  Furthermore, as shown in FIG. 1, the cup gasket 13 is an annular member having an L-shaped cross section, and is made of an elastic body such as rubber. The cup gasket 13 is provided with an appropriate fastening allowance between the mating ring 11 and the inner cylindrical portion 12a of the rotation side sleeve 12, and a sealing property and a fixing force are ensured.

  The mating ring 11 is accommodated in the annular space 10a of the rotary sleeve 12 so that the sealing surface Rs faces the opening of the rotary sleeve 12, and the back side and the inner peripheral side of the mating ring 11 are cupped. The rotation side cartridge 10 is configured by being fixed to the rotation side sleeve 12 via the gasket 13.

  Next, the fixed side cartridge 20 will be described. The fixed side cartridge 20 is mainly composed of a fixed side sleeve 22 fixed to the housing 3, a seal ring 21 accommodated in the fixed side sleeve 22, a bellows 23, a case 24, a driving band 25 and a spring 26. . Hereinafter, the fixed side sleeve 22, the seal ring 21, and the bellows 23 will be described.

  As shown in FIG. 1, the stationary sleeve 22 is an annular member having a substantially U-shaped cross section, and is provided with an outer cylindrical portion 22c that is press-fitted and fixed to the housing 3, and extends radially inward from one end of the outer cylindrical portion 22c. Wall portion 22b, and inner tube portion 22a extending in the axial direction on the outer tube portion 22c side from the inner diameter side end portion of the wall portion 22b. The opening of the stationary sleeve 22 is fixed to the housing 3 so as to face the opening on the rotating cartridge 10 side.

  As shown in FIGS. 2 and 4, the seal ring 21 is made of an annular member having a substantially rectangular cross section, and is made of a material excellent in self-lubricating property and sliding property such as carbon. The seal ring 21 is formed with a sealed end surface S that faces the sealed end surface S of the mating ring 11. The sealing end surface S of the seal ring 21 is formed in an annular portion protruding in the axial direction, and is finished smoothly. Further, a water-repellent water repellent portion Hs is provided on the high-pressure fluid side of the sealing end surface S of the seal ring 21, that is, on the outer diameter side end surface 21a and the outer peripheral surface 21b of the seal ring 21. The outer diameter side end surface 21a of the seal ring 21 is formed lower than the sealed end surface S toward the back side. In the water repellent portion Hs, the water repellent portion Hs is formed on the outer diameter side end surface 21a by coating or the like, and the water repellent portion Hs and the sealed end surface S having no water repellent portion Hs are finished flush with each other. The water repellent portion Hs is made of a resin or powder such as Teflon-based (“Teflon” is a registered trademark) or silicon-based, and is formed on the outer diameter side end surface 21 a and the outer peripheral surface 21 b of the seal ring 21 by coating or the like. The water repellent portion Hs is provided on both the outer diameter side end surface 21 a and the outer peripheral surface 21 b of the seal ring 21, but may be provided only on the outer diameter side end surface 21 a of the seal ring 21. In this embodiment, the mating ring 11 and the seal ring 21 are provided with a water repellent portion having a thickness t or more. However, at least one of the mating ring 11 and the seal ring 21 is provided with a water repellent portion having a thickness t or more. It is good also as a water-repellent part formed by coating and the other provided.

  The bellows 23 is formed by molding a flexible elastic body, for example, a non-metallic material such as rubber, or a thin metal. A driving band 25 is attached to the outer peripheral side of one end of the bellows 23, and the bellows 23 is provided with an appropriate tightening allowance between the driving band 25 and the inner cylindrical portion 22a of the fixed side sleeve 22, and has a sealing property. And securing force is secured. On the other hand, the other end of the bellows 23 is provided with a case 24 on the outer peripheral side, and the seal ring 21 is hermetically held by the case 24 and the bellows 23.

  As shown in FIG. 1, the sealing end surface S of the seal ring 21 is disposed in the annular space 20a of the stationary sleeve 22 so as to face the opening, and the seal ring 21 includes a bellows 23, a case 24, a driving band 25, The fixed-side cartridge 20 is configured by being housed and fixed in the fixed-side sleeve 22 via a spring 26. Thereby, since the seal ring 21 is supported by the flexible bellows 23 and the spring 26, the seal ring 21 is supported to be movable in the axial direction and the radial direction.

  As shown in FIG. 1, the rotating side cartridge 10 and the fixed side cartridge 20 configured as described above are attached so that the respective opening portions face each other, and the mating ring 11 and the seal ring 21 are attached to the sealed end surface S. Thus, the leakage of the sealed fluid can be limited by rotating relative to each other. Even if a relative displacement occurs between the seal ring 21 and the mating ring 11, the seal ring 21 is supported in the radial direction via the flexible bellows 23. It can follow and rotate relatively. The surface pressure of the sealing end surface S is determined by the resultant force of the axial pressing force by the bellows 23 and the spring 26.

  The action of the water repellent portion Hr of the mating ring 11 configured as described above and the Hs of the seal ring 21 will be described.

  The water-repellent portions Hr and Hs that have been subjected to the water-repellent treatment have water repellency and are difficult to wet with liquid. When the water repellency of the surfaces of the mating ring 11 and the seal ring 21 is high, the surfaces of the mating ring 11 and the seal ring 21 are less likely to get wet with the fluid to be sealed. As a result, the surfaces of the mating ring 11 and the seal ring 21 Becomes difficult to adhere to the substance contained in the sealed fluid.

  In particular, since carbon generally used as the seal ring 21 has moderate irregularities on the surface in addition to self-lubricating properties, a lubricating film made of a sealed fluid is formed between the sealing end surface S of the mating ring 11. It can be retained and exhibits excellent lubricating properties. However, carbon exhibits excellent lubrication characteristics, but when used in a fluid with a high silicate concentration, the substances contained in the liquid accumulate on the unevenness of the carbon surface, and peel off when the deposit increases to some extent. May flow to the sealing end surface S and damage the sealing end surface S to lower the sealing function.

  Therefore, the water-repellent part Hs having high water repellency is formed on the surface of the seal ring 21 to prevent the seal ring 21 from getting wet with the fluid to be sealed, thereby preventing adhesion of substances contained in the liquid to the irregularities on the surface of the seal ring. can do. Further, the water repellent portion Hs also reduces the adhesion between the surface of the seal ring 21 and the substance contained in the liquid, so that even if the substance contained in the liquid is deposited and deposited on the carbon surface, the deposit is not formed. Since it peels before it grows large, deposits with large grains are prevented from flowing into the sealed end face S, and damage to the sealed end face S can be prevented. Similarly, the mating ring 11 formed by sintering ceramics such as silicon carbide also has minute irregularities on its surface. Therefore, not only the seal ring 21 but also the water-repellent portion Hr is provided on the outer diameter side of the sealing end surface S of the mating ring 11 to reduce the deposit, and the deposit flows into the sealed end surface S. This can prevent the damage of the sealed end surface S.

  The water repellent parts Hr and Hs are provided at least on the outer diameter side end face 11a of the sealing end face S of the mating ring 11 and the outer diameter side end face 21a of the sealed end face S of the seal ring 21, but the water repellent parts Hr, Hs is also provided on the outer peripheral surface 11b of the mating ring 11 and the outer peripheral surface 21b of the seal ring 21 to further reduce deposits and prevent the deposits from flowing into the sealed end surface S. Damage to S can be prevented.

  In this embodiment, the water repellent portions Hr and Hs are formed by coating, but the method of forming the water repellent portions Hr and Hs is not limited to this, and a plate-like fluororesin or silicon resin having water repellency is used. You may comprise. For example, as shown in FIG. 3, the outer diameter side end surface 11 a of the sealing end surface S of the mating ring 11 is formed lower than the sealing end surface S by a depth t on the back side. Then, a water-repellent resin plate having a thickness t or more is attached to the outer diameter side end surface 11a formed low by the depth t by adhesion or the like, and the water-repellent resin plate and the sealed end surface S are finished flush. In this way, the water-repellent part made of a plate-like member can secure the thickness of the water-repellent part, so that the water-repellent part can be prevented from being lowered due to peeling like a coating, and is more durable than the water-repellent parts Hr and Hs by coating. Will improve.

  The water-repellent portions Hr and Hs are made of a material having water repellency. However, the present invention is not limited to this, and a minute periodic concavo-convex pattern having a diameter of about several nanometers is formed on the surface of a material having low water repellency. Thus, the water repellent portions Hr and Hs may be formed. As a method of forming a minute periodic uneven pattern, a method of physically forming a minute periodic uneven pattern directly on the surface of the mating ring 11 and the seal ring 21 with a laser or the like, or a method of forming a minute period by chemically stacking molecules. A method of forming a concavo-convex pattern can be used. Furthermore, even higher water repellency can be obtained by forming a fine periodic uneven pattern on the surface of a fluororesin plate or the like having excellent water repellency.

  Further, as shown in FIGS. 2 and 5, a gap Ncs having a minute axial gap u is formed between the water repellent part Hr of the mating ring 11 and the water repellent part Hs of the seal ring 21. The For example, the axial gap u in the axial direction of the gap Ncs is formed to be about 1 μm to 1 mm, although it varies depending on the pressure of the sealed fluid. As will be described later, a gap Ncs having a minute axial gap u is formed between the water-repellent part Hr of the mating ring 11 and the water-repellent part Hs of the seal ring 21 so that the gap Ncs is non-contact. Acts as a seal.

  In order to form a minute gap, a minute gap may be formed by parallel axial gaps u as shown in FIG. 2, but as shown in FIG. 5, the water repellent portion Hr of the mating ring 11 and By narrowing the axial gap u between the seal ring 21 and the water repellent part Hs gradually toward the sealed end face S, a minute gap can be easily formed. FIG. 5A shows an example in which the outer diameter side of the sealing end surface S of the seal ring 31 is formed as a conical surface 31a having a certain inclination. With this configuration, the gap portion Ncs between the water-repellent portion Hr of the mating ring 11 and the water-repellent portion Hs of the seal ring 21 is gradually narrowed toward the sealed end surface S, so that a minute gap can be easily formed. Can be formed. FIG. 5B shows an arcuate conical surface 41a having a curved surface that protrudes outward on the outer diameter side of the sealing end surface S of the seal ring 41. FIG. With this configuration, it is possible to easily form a minute gap over a long distance in the radial direction as compared with FIG. 5 (a) and 5 (b), the outer diameter side of the sealing end surface S of the seal ring is inclined in the radial direction. However, the outer diameter side of the sealing end surface S of the mating ring is inclined in the radial direction. Alternatively, the outer diameter side of the sealing end surface S of the seal ring and mating ring may be inclined in the radial direction.

  Here, the reason why the gap Ncs formed between the water repellent part Hr of the mating ring 11 and the water repellent part Hs of the seal ring 21 is formed in a minute gap to function as a non-contact seal will be described. To do.

  As shown in FIG. 6, in a state where the sealed fluid is sealed in the gap Ncs, the fluid film of the sealed fluid includes the pressure P of the sealed fluid and the sealed fluid generated by the rotation of the mating ring 11. The acting centrifugal force Fc and the surface tension T between the sealed end surface S and the sealed fluid mainly act. Therefore, the radial force Fr (direction perpendicular to the axis) acting as a fluid film of the sealed fluid can be expressed by (Equation 1).

  Fr = Pπdu−Fc + 2Tπdcos θ (Formula 1)

  Here, d is a liquid level position (diameter) of the sealed fluid in the gap Ncs, and θ is a contact angle between the sealed fluid and the surfaces of the mating ring 11 and the seal ring 21. The contact angle θ is an angle formed by the solid surface and the tangent line at the liquid surface end of the fluid. In (Expression 1), the first term on the right side indicates the product of the pressure P of the sealed fluid and the area of the liquid surface, that is, the fluid pressure acting on the liquid surface, and the axial gap u in the axial direction of the gap Ncs is small. The fluid pressure acting on the liquid level can be reduced as much as possible. The second term is a centrifugal force acting on the sealed fluid. By reducing the axial gap u, the circumferential speed of the sealed fluid in the gap Ncs is increased, and the pressure gradient due to the centrifugal force in the axial gap u is increased. Further, by increasing the radial width of the gap Ncs, the pressure loss when the sealed fluid flows from the high pressure fluid side to the low pressure fluid side can be increased. The third term represents the product of the surface tension T acting on the liquid surface end of the sealed fluid and the liquid surface end circumference, that is, the surface tension acting on the liquid surface end. If Fr is negative, a force toward the radially outer side (high-pressure fluid side) increases in the sealed fluid, and the sealed fluid can be sealed by the gap Ncs. If Fr is positive, the gap The sealed fluid cannot be sealed by Ncs.

  Here, the contact angle θ varies depending on the state of the seal surfaces Rs and Ss. When the seal surfaces Rs and Ss are difficult to wet, the contact area between the sealed fluid and the sealed end surface is small, and the contact angle θ is large. On the contrary, in the state which is easy to get wet, the contact area between the sealed fluid and the sealed end surface is large, and the contact angle θ is small. For example, when the gap Ncs is formed between the water repellent part Hr and the water repellent part Hs as shown in FIG. 6B, the surface of the water repellent parts Hr and Hs is sealed with the fluid to be sealed. The contact angle θ1 is larger than 90 °, and the radial component of the surface tension T acts toward the high-pressure fluid side, so that it acts in a direction to suppress leakage of the sealed fluid. Conversely, when the gap Ncs is formed between the wall surfaces not having the water repellent portion as shown in FIG. 6C, the contact angle θ2 between the wall surface and the fluid to be sealed becomes smaller than 90 ° and the surface Since the radial component of the tension T acts toward the low-pressure fluid side, it acts in a direction that promotes leakage of the sealed fluid. In (Formula 1), the centrifugal force Fc acts in a direction to limit leakage. Therefore, the condition for sealing the sealed fluid only by the surface tension T of the gap Ncs with Fc being zero on the safe side is (Formula 2). It becomes.

  Fr = Pπdu + 2Tπdcos θ <0 (Formula 2)

  In (Expression 2), P, d, u, and T are always positive values. Therefore, in order to satisfy (Expression 2), the contact angle needs to be θ> 90 °. That is, in order to seal the fluid to be sealed by the gap Ncs, the contact angle needs to be 90 ° <θ <180 ° (−1 ≦ cos θ <0), and the axial gap u at this time is at least (formula It is necessary to set in the range of 3).

u <kT / P (0 <k ≦ 2) (Formula 3)
However, u is the gap (μm) in the axial direction of the gap Ncs, P is the pressure (MPa) of the sealed fluid, and T is the surface tension (N / m) between the gap Ncs and the sealed fluid. Since (Equation 3) ignores the sealing effect due to the centrifugal force, the axial gap u of the gap Ncs determined by (Equation 3) shows a minimum value.

  In (Equation 3), the value of k is determined according to the contact angle θ, but the axial gap u of the gap Ncs between the mating ring 11 and the seal ring 21 is set during stoppage. Therefore, the axial gap u during operation may be larger than during stoppage. Therefore, in consideration of the fluctuation of the axial gap u during operation, the value of k is not determined according to the contact angle θ, but is simply determined in the range of 0 <k <2, and the axial direction of the gap Ncs is determined. The sealed fluid may be sealed by adjusting the size of the gap u.

  If the axial gap u of the gap Ncs is determined to be at least the minimum gap satisfying (Equation 3), the sealed fluid can be sealed by the gap Ncs. However, since the minimum gap u determined by (Equation 3) is a minute gap, the axial gap u between the mating ring 11 and the seal ring 21 is actually set to the gap u determined by Expression 3. It is difficult to do. Therefore, by gradually narrowing the axial gap u between the water repellent part Hr of the mating ring 11 and the water repellent part Hs of the seal ring 21 shown in FIG. Since it can be formed, the gap Ncs between the water repellent part Hr of the mating ring 11 and the water repellent part Hs of the seal ring 21 can function as a non-contact seal.

  (Formula 3) was a condition for sealing the sealed fluid only by the surface tension T of the gap Ncs. However, instead of adjusting the size of the axial gap u of the gap Ncs, by adjusting the outer diameter and the inner diameter of the gap Ncs, only the centrifugal force due to the swirling flow of the gap Ncs can be used for sealing. The fluid can also be sealed.

  The fluid in the gap Ncs is swirling due to the rotation of the mating ring 11. Since the mating ring 11 rotates at the peripheral speed Vs and the seal ring 21 is stationary, the rotational speed Vf of the sealed fluid in the gap Ncs is the rotational speed Vs = rω (r is a radius, ω is a speed between the rotational angular speed of the mating ring 11) and the speed of the seal ring 21 = 0. Therefore, the swirling speed of the sealed fluid in the gap Ncs can be expressed as Vf = nrω (coefficient of 0 <n <1). Further, in the flow swirling at the swivel speed Vf in the gap Ncs, the centrifugal force based on the swirl speed Vf and the pressure gradient in the radial direction are balanced, and therefore the following equation is established.

dp / dr = ρVf ² / r = n ² ρrω ² (Formula 4)
ρ is the density of the fluid to be sealed. When (Equation 4) is integrated from the inner radius r1 (outer radius of the sealed end surface S) of the gap Ncs to the outer radius r2, Equation 5 is obtained.

Pr2-Pr1 = ρn ² ω ² (r2 ² −r1 ² ) / 2 (Formula 5)
Here, the inner radius r1 (sealed) of the gap Ncs is such that Pr2 = P (pressure of the sealed fluid) at the outer radius r2 of the gap Ncs and Pr1 = 0, that is, atmospheric pressure, at the inner radius r1 of the gap. If the outer radius of the end face S) and the outer radius r2 are determined, the gap portion Ncs can function as a non-contact seal. Usually, since the inner radius r1 of the gap Ncs (the outer radius of the sealed end surface S) is determined from the design conditions, the outer radius r2 of the gap Ncs can be determined by (Equation 6).

r2 ² −r1 ² = 2P / ρn ² ω ² (0 <n <1) (Formula 6)
Where r1 is the inner radius dimension (m) of the gap Ncs, r2 is the outer radius dimension (m) of the gap Ncs, P is the sealed fluid pressure (Pa), and ρ is the sealed fluid density (kg / m ³ ). Ω is the angular velocity of the mating ring. Since (Equation 6) ignores the sealing effect of the water repellent portion of the gap Ncs, the outer radius r2 determined by (Equation 6) shows the maximum value.

  From the above, if the radial width Lc = r2-r1 of the gap Ncs between the water repellent part Hr of the mating ring 11 and the water repellent part Hs of the seal ring 21 is set to satisfy at least Expression 6, The portion Ncs can function as a non-contact seal. At this time, the value of n in (Equation 6) is determined by the size of the axial gap u of the gap Ncs. In order to make the gap portion Ncs function as a non-contact seal portion, the radial width Lc of the gap portion Ncs is arbitrarily determined by adjusting the size of the axial gap u of the gap portion Ncs according to (Equation 3). Alternatively, the radial width Lc of the gap portion Ncs may be adjusted by the equation (6) to arbitrarily adjust the size of the axial gap u of the gap portion Ncs, or the axial gap of the gap portion Ncs. Both the size of u and the radial width Lc may be adjusted.

  The effects of the present invention are as follows.

  The mating ring 11 and the seal ring 21 are provided with water-repellent portions Hr and Hs that are water-repellent on the high-pressure fluid side of the sealed end surface S, so that the high-pressure side of the mating ring 11 and the seal ring 21 is sealed. The substance contained in the sealed fluid is less likely to get wet with the fluid, and the deposition and deposition of the substance contained in the sealed fluid can be prevented, and the deposit on the sealed end surface S from the high-pressure fluid side can be prevented. It is possible to prevent the sealed end surface S from being damaged due to inflow.

  The gap portion Ncs is provided on the high-pressure fluid side of the sealed end surface S, and the axial gap u of the gap portion Ncs is set to at least the range of (Equation 3) 0 <u <kT / P. It can function as a non-contact seal. Thereby, since the approach of the sealed fluid between the sealed end surfaces can be restricted, it is possible to prevent the sealed end surface S from being damaged by the substance contained in the sealed fluid.

The inner radius r1 and the outer radius r2 of the gap Ncs are set by (Expression 6) r2 ² −r1 ² = 2P / ρn ² ω ^2, so that the gap Ncs can function as a non-contact seal. Thereby, since the approach of the sealed fluid between the sealed end surfaces can be restricted, it is possible to prevent the sealed end surface S from being damaged by the substance contained in the sealed fluid.

  Since the water repellent portions Hs and Hr have a contact angle with the sealed fluid larger than 90 °, the entry of the sealed fluid into the sealed end surface S can be restricted, and the substances contained in the sealed fluid adhere to it. It becomes difficult to prevent a decrease in water repellency due to scratches or peeling.

  Since the axial gap u of the gap Nsc is formed so as to become gradually narrower toward the sealed end face, a minute axial gap can be formed between the rotating ring and the fixed ring.

  Next, with reference to FIG. 7, the mechanical seal which concerns on Example 2 of this invention is demonstrated. The second embodiment is different from the first embodiment in that the sealing end surface S includes a dynamic pressure generating mechanism that generates a dynamic pressure in the relative rotation between the mating ring 11 and the seal ring 21. Note that the same components as those shown in the above-described embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In the second embodiment, a case where the spiral groove 58 is provided on the sealed end surface S will be described as an example as a dynamic pressure generating mechanism that generates a positive pressure (dynamic pressure) by relative movement of the mating ring 11 and the seal ring 21. .

  As shown in FIG. 7, a water repellent portion Hs (light ink portion in FIG. 7) is provided on the outer peripheral side of the seal ring 51. A plurality of spiral grooves 58 (six in this embodiment) are formed on the sealing end surface S where the seal ring 51 and the mating ring 11 rotate relative to each other. The spiral groove 58 has a bottom 58e that is slightly recessed from the sealed end surface S, and is a spiral groove that is inclined to the rear side in the rotation direction of the mating ring 11, and is an inner peripheral end that is open to the low-pressure fluid side. 58a, a pair of helical walls 58b and 58d closed by the sealed end surface S, and an outer peripheral side end wall 58c closed by the sealed end surface S.

  As shown in FIG. 7, when the mating ring 11 rotates in the clockwise direction, the low-pressure fluid (air) sucked from the inner peripheral end 58a opened to the low-pressure fluid side becomes a pair of helical walls 58b, 58d and The pressure is increased in the spiral groove 58 closed by the outer peripheral side end wall 58c, and the pressurized fluid is supplied from the spiral groove 58 to the sealed end surface S, and the mating ring 11 and the seal ring 51 maintain fluid lubrication. can do.

  When the gap Ncs functions as a non-contact seal, the flow of the sealed fluid from the high-pressure fluid side to the sealed end surface S is hindered, so that the lubrication state at the sealed end surface S is a boundary lubrication state. However, even if the flow of the sealed fluid from the high-pressure fluid side to the sealed end surface S is hindered, the low-pressure fluid (air) is supplied from the low-pressure fluid side to the sealed end surface S by the plurality of spiral grooves 58 provided on the sealed end surface S. Therefore, fluid lubrication can be maintained, and abnormal noise such as squeal can be prevented. In addition, since the inflow of the sealed fluid from the high-pressure fluid side to the sealed end surface S is hindered, it is possible to prevent the substances contained in the sealed fluid from being deposited and deposited on the sealed end surface S, and thus due to the deposits. It is possible to prevent the sealing end surface S from being damaged and improve the sealing performance.

  In the above embodiment, the dynamic pressure generating mechanism is configured by the spiral groove 58. However, the dynamic pressure generating mechanism may be configured by a Rayleigh step mechanism or a combination of a Rayleigh step mechanism and a reverse Rayleigh step, and the groove depth gradually decreases in the rotation direction. It is good also as a deformation | transformation Rayleigh step mechanism which consists of a dynamic-pressure generation | occurrence | production groove | channel which has the taper-shaped bottom wall which becomes.

DESCRIPTION OF SYMBOLS 1 Mechanical seal 2 Rotating shaft 3 Housing 10 Rotation side cartridge 11 Mating ring (rotating ring)
11a Outer diameter side end face 12 Rotating side sleeve 13 Cup gasket 18 Rotating ring 20 Fixed side cartridge 21 Seal ring (fixed ring)
21a Outer diameter side end face 22 Fixed side sleeve 23 Bellows 24 Case 25 Driving band 26 Spring 31 Seal ring (fixed ring)
41 Seal ring (fixed ring)
51 Seal ring (fixed ring)
58 Positive pressure generation mechanism S Sealed end face Hr, Hs Water repellent part Ncs Gap part u Axial gap r1 Inner radius r2 of gap part Ncs Outer radius of gap part Ncs

Claims (6)

A rotating ring fixed on the rotating shaft side, and a fixed ring disposed on the housing side so as to face the rotating ring,
A mechanical seal configured to seal a sealed fluid while relatively rotating between sealed end faces which are opposed end faces of the rotating ring and the fixed ring,
A mechanical seal characterized in that at least one of the rotating ring and the stationary ring is provided with a water-repellent part that is water-repellent on the high-pressure fluid side than between the sealed end faces. 2. The mechanical device according to claim 1, wherein a gap is provided on the high-pressure fluid side from between the sealed end faces, and the axial gap u of the gap is set in a range of at least 0 <u <kT / P. seal.
Where u is the axial gap of the gap, P is the pressure of the sealed fluid, T is the surface tension between the water repellent portion and the sealed fluid, and k is a coefficient in the range of 0 <k ≦ 2. The mechanical seal according to claim 2, wherein an inner radius and an outer radius of the gap portion are set by r2 ² −r1 ² = 2P / ρn ² ω ² .
Where r1 is the inner radius of the gap, r2 is the outer radius of the gap, P is the sealed fluid pressure, ρ is the sealed fluid density, ω is the angular velocity of the rotating ring, and n is 0 <n <. A coefficient in the range of 1.   The mechanical seal according to claim 2 or 3, wherein the gap in the axial direction of the gap portion is gradually narrowed toward the sealed end face.   The mechanical seal according to any one of claims 1 to 4, wherein a contact angle between the water repellent part and the fluid to be sealed is larger than 90 °.   The mechanical seal according to claim 1, wherein the sealing end surface includes a dynamic pressure generating mechanism that generates dynamic pressure by relative rotation between the rotating ring and the fixed ring.

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