JP2005249131A - Floating ring type mechanical seal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a floating ring type mechanical seal capable of properly securing the parallelism of a seal face even under a condition of high pressure and large pressure fluctuation, and free from abnormal abrasion and abnormal leakage of the seal face. <P>SOLUTION: A floating ring 8 is pressed and held between a rotational ring 6 at a rotating shaft 2 side and a stationary ring 4 at a seal case 3 side. The rotational ring 6 is relatively unrotatably held by a sleeve mounted on a rotating shaft 2 in a state of being displaceable in the axial direction and the radial direction within an elastic deformation range of a first O-ring 17 and a second O-ring 18 functioned as a secondary seal. The first O-ring 18 slid to the radial displacement of the rotary ring 2 with respect to the rotary ring 2 is composed of polytetrafluoro ethylene. A contact face 4a with the floating ring 8 of the stationary ring 4 is coated with a polytetrafluoro ethylene film 41 having a ten point average height of 2μm or less and a film thickness of 10-20 μm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is a mechanical seal that is suitably used under high pressure conditions as a shaft sealing means such as a canned water circulation pump of a thermal power plant, and is capable of moving in an axial direction between a rotary ring provided on a rotary shaft and a seal case, and The present invention relates to a floating ring type mechanical seal in which a floating ring is clamped and held in a state in which relative rotation with respect to the stationary ring is prevented between a stationary ring provided in a state of being biased in the direction of the rotating ring.

  As shown in FIGS. 3 and 4, the conventional floating ring type mechanical seal is held by the rotary ring 6 fixed to the rotary shaft and the seal casing so as to be movable in the axial direction and is urged by a spring in the direction of the rotary ring. Relative rotational sliding contact of the seal surfaces 6a and 83a, which are contact surfaces between the rotating ring 6 and the floating ring 8, is held between the stationary ring 4 by holding and holding the floating ring 8 whose both end portions are substantially symmetrical. By the action, the sealed fluid region A which is the outer peripheral side region of the relative rotational sliding contact portion and the non-sealed fluid region (atmospheric region) B which is the inner peripheral side region are shield-sealed (hereinafter referred to as “the sealed fluid region A”). "Conventional seal" is well known (see, for example, Patent Document 1). The stationary ring 4 and the idle ring 8 are connected so as not to rotate relative to each other, and the pressing surfaces 4a and 82a that are contact surfaces of the rings 4 and 8 do not rotate relative to each other.

  By the way, a general configuration is adopted in which a rotating ring and a stationary ring are brought into direct contact without interposing the idle ring 8 and a sealed fluid is sealed by a relative rotational sliding contact between the rotating ring and the stationary ring. In the case of a mechanical seal, when it is used under high pressure conditions, the parallelism of the seal surface, which is the contact surface between the rotating ring and the stationary ring, is impaired, and a good sealing function cannot be exhibited. That is, since the stationary ring is held in the seal casing so as to be movable in the axial direction so as to follow the rotating ring, the fluid pressure in the sealed fluid region is maintained at the proximal end portion of the stationary ring held by the seal case. However, the influence (pressure strain) is large at the distal end side portion of the stationary ring, that is, the seal surface side portion which is free because it follows the rotating ring. Therefore, the pressure strain distribution in the axial direction in the stationary ring becomes non-uniform, that is, the pressure strain is greatly different between the proximal end portion and the distal end side portion in the stationary ring, and the stationary ring is greatly distorted with respect to the axis. As a result, the sealing surface of the stationary ring is inclined, and the parallelism with the sealing surface of the rotating ring is significantly impaired.

On the other hand, in the conventional seal, an idle ring 8 for exerting a sealing function by a relative rotational sliding contact with the rotary ring 6 is held between the rotary ring 6 and the stationary ring 4 with a pressure. Since both end portions are substantially symmetrical, the influence of the fluid pressure in the sealed fluid region A (hereinafter simply referred to as “fluid pressure”) is received in a balanced manner in the axial direction. That is, the pressure strain generated in the idle ring 8 is substantially the same at both end portions, and is not greatly distorted with respect to the axis. Therefore, the seal surface 83a of the idle ring 8 is not inclined with respect to the seal surface 6a of the rotary ring 6 even under high pressure conditions, and the parallelism of the seal surfaces 6a and 83a is ensured, and a good sealing function is achieved. It can be demonstrated.
Japanese Patent Laid-Open No. 50-149860 (FIG. 4)

  However, according to the conventional seal, when this is used as a shaft sealing means of a rotating device (for example, a canned water circulation pump of a thermal power plant) where the fluid pressure is extremely high and a large pressure fluctuation occurs, that is, it rotates with a stationary ring. When used under a high pressure condition in which the pinching force of the idle ring 8 by the ring is extremely high, the parallelism of the seal surfaces 6a and 83a is impaired as described below, and an abnormality from between the seal surfaces 6a and 83a occurs. Leakage and abnormal wear occur, and a good sealing function cannot be achieved.

  That is, the idle ring 8 contracts and deforms in the radial direction as the fluid pressure increases, and the contraction deformation (elastic deformation) is eliminated and recovered as the fluid pressure decreases. Difference in material and holding structure from the rotating ring 6 and the like (for example, the idle ring 8 is generally made of a soft material such as carbon that is more easily deformed than the rotating ring 6 and the like, and the radial direction due to fluid pressure. Unlike the rotating ring 6 and the like that are fitted and held on the rotating shaft, there is no holding means to prevent or suppress the deformation, so the contraction deformation of the floating ring 8 is smaller than that of the rotating ring 6 or the stationary ring 4. Remarkably larger.

Further, as shown in FIG. 3A, axial contact surface loads W ₁ and W ₂ and radial frictional forces F ₁ and F ₂ act on the pressing surface 82a and the seal surface 83a of the idle ring 8. It will be. Here, the contact surface load (hereinafter referred to as “first contact surface load”) W ₁ acting on the pressing surface 82 a is the spring urging force (spring force) that presses the stationary ring 4 in the direction of the rotating ring and the stationary ring 4. is due to the fluid pressure acting on the back (back pressure), the surface-load acting on the sealing surface 83a (hereinafter "second contact surface load" referred to) W ₂ is rotary ring by the first contact surface load W ₁ 6 due to the pressing reaction force on the sealing member 6 and the opening force between the sealing surfaces by the fluid film formed between the sealing surfaces 6a and 83a (the fluid film pressure that tries to expand the sealing surfaces 6a and 83a) (balance ratio and criticality) Balance). Therefore, the both-contact surface loads W ₁ and W ₂ increase or decrease substantially in proportion to the fluid pressure and have a relationship of W ₁ > W ₂ as shown in FIG. It should be noted that the fluid pressure acting on both end faces of the idle ring 8 is substantially the same in the opposite direction because the both end portions of the idle ring 8 are substantially symmetrical, and cancel each other out. Become. Further, the frictional force acting on the pressing surface 82a (hereinafter "first frictional force" hereinafter) frictional force (hereinafter "second friction force" hereinafter) F ₂ acting on F ₁ and the sealing surface 83a is the change in fluid pressure It is a frictional resistance force that acts to prevent slippage that occurs at the contact portion between the stationary ring 4 and the rotating ring 6 due to the radial deformation of the idle ring 8, and the maximum between the pressing surfaces 4a and 82a and between the sealing surfaces 6a and 83a. With the value of the static frictional force as the upper limit value, it increases and decreases substantially in proportion to the fluid pressure, as with the contact loads W ₁ and W ₂ . Therefore, if the static friction coefficient of the idle ring 8 with respect to the rotating ring 6 and the stationary ring 4 is μ, the maximum static friction force between the pressing surfaces 4a and 82a (hereinafter referred to as “first maximum static friction force”) is μ · W _1. The maximum static friction force between the seal surfaces 6a and 83a (hereinafter referred to as “second maximum static friction force”) is given by μ · W ₂ .

Thus, in a pressure increasing situation where the fluid pressure increases due to a change in the operating condition of the rotating device, the start of operation, etc., as shown in FIG. 3A, the pressing surface 82a and the sealing surface 83a of the idle ring 8 are in contact with The loads W ₁ and W ₂ and the frictional forces F ₁ and F _{2 in the} outer diameter direction act, and these contact surface loads W ₁ and W ₂ and the frictional forces F ₁ and F ₂ increase the fluid pressure. It increases with it. When the frictional forces F ₁ and F ₂ reach the maximum static frictional forces μ · W ₁ and μ · W ₂ , radial slip occurs between the idle ring 8 and the stationary ring 4 or the rotating ring 6. It will be.

However, since W ₁ > W ₂ and μ · W ₁ > μ · W ₂ as described above, first, in the process of increasing the fluid pressure, first, the second friction force F ₂ is the second maximum static friction force. When μ · W ₂ is reached, slip occurs between the seal surfaces 6a and 83a. On the other hand, the first frictional force F ₁ is in the range of F ₁ <μ · W ₁ , and no slip occurs between the pressing surfaces 4a and 82a. Therefore, as shown in FIG. 3B, the seal surface 83a of the idle ring 8 slides in the inner diameter direction with respect to the seal surface 6a of the rotary ring 6, and the seal surfaces 6a and 83a are moved to the inner diameter side (atmosphere region B side). The idle ring 8 is tilted in such a state that it is opened (hereinafter referred to as “periphery of outer diameter”).

When going further boosted from this state, the first frictional force F ₁ reaches the first maximum static friction force mu · _{W 1,} slippage pressing surface 4a, between 82a. As a result, as shown in FIG. 3C, the inclination of the idle ring 8 is eliminated, and the seal surfaces 6a and 83a are returned to the parallel state (hereinafter referred to as the “whole surface contact state”).

By the way, when the second frictional force F ₂ reaches the second maximum static frictional force μ · W ₂ , slippage occurs between the seal surfaces 6 a and 83 a, so that the second frictional force F ₂ temporarily decreases until F ₂ ≈0. become. Thereafter, the second friction force F ₂ increases from F ₂ ≈0 as the fluid pressure increases, reaches the second maximum static friction force μ · W ₂ again, and causes slipping, and F ₂ It decreases to ≈0. That is, as shown by the solid line in FIG. 5B, the second frictional force F ₂ sticks and slips between F ₂ ≈0 and F ₂ = μ · W ₂ like a saw blade as the fluid pressure increases. Will increase. The first frictional force F ₁ is likewise reaches the first maximum static friction force mu · _{W 1,} by the pressing surface 4a, a slip between 82a occurs, the first frictional force F ₁ is temporarily It will decrease until F ₁ ≈0. Thereafter, the first friction force F ₁ increases from F ₁ ≈0 as the fluid pressure increases, reaches the first maximum static friction force μ · W ₁ again, and causes slipping, and F ₁ It decreases to ≈0. That is, as indicated by the solid line in FIG. 5A, the first friction force F ₁ is F ₁ ≈0 and F ₁ = μ · W ₁ as the fluid pressure increases, as with the second friction force F _2. It increases while stick-slip in the shape of a saw blade. Here, the stick-slip cycle (pitch) is small for the second friction force F _{2 and} large for the first friction force F ₁ .

  Therefore, in the pressure increasing process until the fluid pressure reaches a predetermined maximum pressure, the slip between the seal surfaces 6a and 83a and the slip between the pressing surfaces 4a and 82a are alternately repeated, and the seal surface 6a. , 83a, depending on the fluid pressure, the outer diameter contact state (for example, the state shown in FIG. 3B), the entire surface contact state (for example, the state shown in FIG. 3C), It will not be stable.

  Furthermore, the relative movement state of the seal surfaces 6a and 83a is not stable in this way even in a pressure-decreasing situation where the fluid pressure drops from the maximum pressure due to a change in the operating condition, operation stop, or the like.

That is, when the fluid pressure decreases from the maximum pressure, the contraction deformation (elastic deformation) in the radial direction of the floating ring 8 generated at the time of pressure increase gradually recovers with the decrease of the fluid pressure, and the floating ring 8 moves in the radial direction. It will be expanded and deformed. Therefore, the frictional forces F ₁ and F ₂ are gradually reduced as the pressure is lowered, and eventually act in the opposite direction. That is, assuming that the acting direction (outer diameter direction) of the frictional forces F ₁ and F ₂ at the time of pressure increase is positive, the negative frictional force −F ₁ , −F ₂ ( Hereinafter, the negative first friction force “−F ₁ ” is referred to as “first friction force f ₁ ”, and the negative second friction force “−F ₂ ” is referred to as “second friction force f ₂ ”). After that, as shown in FIG. 4D, the frictional forces f ₁ and f ₂ become −μ · W ₁ ≦ f ₁ <0, −μ · W ₂ ≦ f _{2 as the} fluid pressure decreases. It increases in the range of <0 (increases in the negative direction).

Further, when the fluid pressure is reduced from this state, first, the second frictional force f ₂ reaches the second maximum static frictional force −μW ₂ , and as shown in FIG. A state in which 83a slides in the outer diameter direction with respect to the seal surface 6a of the rotating ring 6 and the seal surfaces 6a and 83a open to the outer diameter side (sealed fluid region A side) (hereinafter referred to as “inner diameter contact state”). It becomes.

When the pressure reduction further proceeds, the first friction force f ₁ reaches the first maximum static friction force −μ · W ₁ , and slip occurs between the pressing surfaces 4 a and 82 a, as shown in FIG. The inclination of the idle ring 8 is almost eliminated, and the seal surfaces 6a and 83a return to the substantially parallel full contact state.

By the way, even when the pressure is lowered, when the frictional forces f ₁ and f ₂ reach the maximum static frictional forces −μ · W ₁ and −μ · W ₂ , they slide between the pressing surfaces 4a and 82a or between the sealing surfaces 6a and 83a. Is temporarily reduced until f ₁ ≈0 and f ₂ ≈0, and then increases as the fluid pressure decreases, and again the maximum static frictional force −μ · W ₁ , −μ · _W will _{be 2} to reach, such frictional forces increase and decrease are repeated. That is, the frictional forces f ₁ and f ₂ are expressed as f ₁ ≈0, f ₂ ≈0 and f ₁ ≈−μ · W ₁ , as the fluid pressure increases, as indicated by chain lines in FIGS. It increases while stick-slip in a saw blade shape between f ₂ = −μ · W ₂ . The stick-slip cycle (pitch) is also small for the second friction force f _{2 and} large for the first friction force f ₁ , as in the case of pressure increase.

  Therefore, even in the pressure decreasing process until the fluid pressure reaches a predetermined minimum pressure, the slip between the seal surfaces 6a and 83a and the slip between the pressing surfaces 4a and 82a are alternately repeated, and the seal surface The relative motion state of 6a, 83a is a state of contact with the inner diameter (for example, the state shown in FIG. 4E) or a state of contact with the entire surface (for example, the state shown in FIG. 4F), depending on the fluid pressure. It will not be stable.

  As described above, in the conventional seal, the first maximum static frictional force between the pressing surfaces 4a and 82a and the second maximum static frictional force between the sealing surfaces 6a and 83a are greatly different from each other. The contact resistance balance between the ring 6 and the stationary ring 4 is lost, and the tilting operation of the idle ring 8 and the correcting operation thereof are repeated according to the pressure increase state and the pressure decrease state. As a result, the seal surfaces 6a and 83a The parallelism cannot be ensured, and the contact form of the free ring seal surface 83a with the rotary ring seal surface 6a varies. Due to the variation in the contact form, abnormal wear of the seal surface (particularly, the soft ring seal surface 83a that is softer than the rotating ring seal surface 6a) occurs. Further, when the seal surface is abnormally worn, the seal surfaces 6a and 83a cannot be properly in contact with each other, and abnormal leakage occurs between the seal surfaces 6a and 83a. Further, even when the seal surface does not wear abnormally, the seal surface 6a, 83a is in a contact state with respect to the inner diameter where the seal surface 6a, 83a opens toward the sealed fluid region A side, regardless of the state where the seal surface 6a, 83a is contacted with the outer diameter. Then, a large amount of leakage occurs between the seal surfaces 6a and 83a. That is, in such a state of contact with the inner diameter, the seal surfaces 6a and 83a are not in contact with each other as in the so-called taper face type non-contact seal, and the taper amount of the free ring seal surface 83a to the rotating ring seal surface 6a is the third power of the taper amount. A large amount of leakage in proportion to will occur.

  Moreover, in the conventional seal, when the fluid pressure is extremely high, the rotary ring 6 is also deformed by the fluid pressure, and this also impairs the parallelism of the seal surfaces 6a and 83a. Combined with the fact that the contact resistance balance between the ring 8 and the stationary ring 4 and the rotating ring 6 is lost, the parallelism of the seal surfaces 6a and 83a is impaired, so that a satisfactory sealing function cannot be expected.

  The present invention solves such problems, and ensures the parallelism of the seal surface, which is the contact surface between the rotating ring and the idle ring, even under conditions where the fluid pressure is extremely high and fluctuates greatly. It is possible to provide a floating ring type mechanical seal that can exhibit a good sealing function without causing abnormal wear or abnormal leakage of the seal surface.

  In the present invention, the rotating ring is rotated relative to the stationary ring between the rotating ring provided on the rotating shaft and the stationary ring provided in the seal case so as to be axially movable and biased in the rotating ring direction. In order to achieve the above object, in the floating ring type mechanical seal that is held under pressure while being blocked, in particular, the rotating ring is connected via a plurality of O-rings including those that function as secondary seals. In the elastic deformation range of the O-ring, the rotating shaft is held on the rotating shaft so as to be displaceable in the axial direction and the radial direction, and the radial direction of the rotating ring is at least between the O-ring and the rotating ring. It is proposed that the O-ring that causes slippage with respect to the displacement is made of a low-friction elastic material (an elastic material having a low friction coefficient with respect to the rotating ring).

  In such a floating ring type mechanical seal, it is preferable that the O-ring causing the slip is made of polytetrafluoroethylene (PTFE).

  Further, it is preferable that at least one of the contact surfaces of the free ring and the stationary ring is coated with a low friction material film made of PTFE or the like, and the surface roughness of the low friction material film is sufficiently increased by lapping or the like. It is preferable that the point average height (Rz) is 2 μm or less (generally 0.5 to 2 μm, and about 1 μm is optimal). When Rz> 2 μm, smooth sliding between the free ring and the stationary ring cannot be expected regardless of the material of the film. Moreover, it is preferable that the film thickness of a low friction material film (polytetrafluoroethylene film etc.) is 10-20 micrometers. If the film thickness exceeds 20 μm, the contact surface hardness with the mating ring decreases, so the mating ring bites into the low-friction material film, and the sliding with the idle ring is not performed smoothly. If the thickness is less than 10 μm, the low-friction material film may be partially worn or peeled off due to contact wear with the other ring.

  Further, the idle ring type mechanical seal of the present invention is inserted and fixed to the stationary side sealing element including the seal case and a group of members attached to the rotary case and the rotary shaft so as to facilitate the assembling and detaching operations to and from the rotating device. The sleeve and the rotating side sealing element composed of a group of members attached to the sleeve can be integrally connected by a detachable set plate in a state where the idle ring is held between the stationary ring and the rotating ring. It is preferable to use a cartridge type mechanical tool.

  According to the floating ring type mechanical seal of the present invention, the contact surface between the rotating ring and the floating ring is caused by the fluid pressure even under a severe pressure condition in which the pressure of the fluid to be sealed is extremely high and greatly fluctuates. The parallelism of the seal surface is not impaired, and abnormal wear and abnormal leakage of the seal surface can be effectively prevented to exhibit a good sealing function. Therefore, the idle ring type mechanical seal of the present invention can be suitably used as a shaft seal means such as a canned water circulation pump of a thermal power plant, and its practical value is extremely large.

  1 and 2 show an example of an idle ring type mechanical seal according to the present invention. FIG. 1 is a longitudinal side view showing a state in which the mechanical seal is incorporated in a rotating device, and FIG. It is an enlarged view.

  That is, the floating ring type mechanical seal according to the present invention shown in FIG. 1 is a rotary device (for example, a canned water circulation pump of a thermal power plant) in which the pressure of the fluid to be sealed is extremely high and a large pressure fluctuation occurs depending on the operation state. It is used as a shaft seal means, and passes through a seal case 3 attached to a shaft seal casing (for example, a pump casing of the above-mentioned canned water circulation pump) 1 of the rotating device and the shaft seal casing 1. A sleeve 5 fitted and fixed to a rotating shaft 2 (for example, the impeller shaft of the above-described canned water circulation pump), a rotating ring 6 provided on the rotating shaft 2 facing the stationary ring 4, and a seal case 3. A spring 7 interposed between the stationary ring 4, a floating ring 8 held between both the rings 4 and 6, and a set plate 9 connecting the seal case 3 and the sleeve 5. Thus, due to the relative rotational sliding contact between the rotating ring 6 and the idle ring 8, the sealed fluid region (region communicating with the in-machine region of the rotating device) A that is the outer peripheral side region of the relative rotational sliding contact portion is not sealed. It is of a cartridge type configured to shield and seal a fluid region (atmospheric region which is an outside region of the rotating device) B. In the following description, front and rear means the left and right in FIGS. Further, the axis refers to the axis of the rotating shaft 2.

  As shown in FIG. 1, the seal case 3 has a cylindrical shape attached to the rear end portion of the shaft seal casing 1 in a state of concentrically surrounding the rotary shaft portion 2a protruding rearward from the shaft seal casing 1. A cylindrical main body 31 that contacts and engages the shaft seal casing 1, an annular wall portion 32 that is integrally formed on the inner peripheral portion of the rear end thereof, and a front surface portion of the wall portion 32. And a spring retainer 33 attached to. The spring retainer 33 includes an annular spring holding portion 33a attached to the wall portion 32 and a cylindrical stationary ring holding portion 33b protruding forward from the inner peripheral side end portion thereof. The seal case 3 is formed with supply / discharge passages 35 and 36 for the quenching liquid (water) 34 and a drain 37.

  As shown in FIG. 1, the stationary ring 4 is held in the seal case 3 via an O-ring 10 and a drive pin 11 so as to be movable in the axial direction and not relatively rotatable. That is, the stationary ring 4 has a base end portion (rear end portion) fitted to the stationary ring holding portion 33b of the spring retainer 33 via the O-ring 10 so that the seal case 3 is O-spaced therebetween. In a state of being sealed (secondary seal) by the ring 10, it is held so as to be movable in the axial direction. In addition, the stationary ring 4 has a plurality of drive pins (only one shown) 11 projecting from the base end portion of the stationary ring 4, and each pin 11 is formed in the spring holding portion 33 a of the spring retainer 33. By engaging with, relative rotation with respect to the seal case 3 is prevented in a state in which movement in the axial direction within a predetermined range is allowed. The stationary ring 4 is made of a hard metal material (for example, stainless steel) in consideration of adhesiveness with a low-friction material film 41 to be described later.

  As shown in FIG. 1, the sleeve 5 includes a cylindrical main body portion 51 inserted through the rotary shaft portion 2 a, and an annular first holding portion 52 formed at the front end portion (front end portion) of the main body portion 51. The cylindrical second holding portion 53 protrudes rearward from the outer peripheral portion of the first holding portion 52, and is located in the seal case 3 except for the base end portion (rear end portion) of the main body portion 51. In the state, it is inserted and fixed to the rotating shaft 2. That is, the stopper ring 13 inserted through the rotary shaft 2 is fitted and fixed to the base end portion of the main body 51 protruding rearward from the seal case 3 by an appropriate number of first set screws 14, and the stopper ring 13. Is fixed to the rotary shaft 2 by an appropriate number of second set screws 15, so that the sleeve 5 is detachably fixed to the rotary shaft 2. An appropriate number of O-ring grooves are formed in the inner peripheral portion of the first holding portion 52, and the space between the rotary shaft 2 and the sleeve 5 is secured by the O-ring 16 engaged and held in the O-ring groove. It is sealed (secondary seal). Note that a labyrinth seal ring 54 for constituting a labyrinth seal with the seal case 3 is attached to the distal end portion (front end portion) of the sleeve 5.

  As shown in FIG. 1, the rotary ring 6 can be displaced in the axial direction and the radial direction (direction orthogonal to the axial direction) within the elastic deformation range of the O-rings 17 and 18 via a plurality of O-rings 17 and 18. It is held on the rotating shaft 2 in a state where it can be deformed). That is, as shown in FIGS. 1 and 2, the rotating ring 6 is located between the first holding portion 52 and the annular space formed between the opposing peripheral surfaces of the main body portion 51 and the second holding portion 53 in the sleeve 5. In a state where axial displacement is allowed in the elastic deformation range of the first O-ring 17 interposed between the second O-ring 17 and the second O-ring 18 interposed between the second holding portion 53 and in the radial direction. It is fitted and held in a state where displacement is allowed. A sufficient annular gap between the inner peripheral surface of the rotating ring 6 and the outer peripheral surface of the main body 51 opposite thereto is sufficient to allow radial displacement and deformation of the rotating ring 6 as shown in FIG. 55 is formed.

  That is, as shown in FIG. 2, the first O-ring 17 is engaged and held in an O-ring groove formed on the rear end surface of the first holding portion 52, and the back surface (front end surface) of the rotary ring 6 is placed on the first O-ring 17. It is received with a slight gap between it and the rear end surface of the holding portion 52. The first O-ring 17 functions as a cushioning material that absorbs and relaxes the axial pressing force acting on the rotating ring 6, and slips so as not to hinder the radial displacement of the rotating ring 6. It will occur. Accordingly, the first O-ring 17 is an elastic material having an elastic force sufficient to exhibit a cushion function against the axial displacement of the rotating ring 6, and has a low friction coefficient with respect to the rotating ring 6. It is necessary to use a low-friction material that can easily slip with respect to radial displacement, and in this example, it is made of polytetrafluoroethylene (PTFE). Further, as shown in FIG. 2, the second O-ring 18 is sandwiched between the opposed peripheral surfaces of the rotating ring 6 and the second holding portion 53 in a state where the second O-ring 18 can be elastically deformed to allow the radial displacement of the rotating ring 6. The pressure is held, and functions as a secondary seal that seals between the sleeve 5 (second holding portion 53) and the rotating ring 6 regardless of the radial displacement of the rotating ring 6. The second O-ring 18 may be made of an elastic material sufficient to function as a secondary seal, and in this example, other O-rings 10, 16, and 25 that function as secondary seals are also used as fluorine. It is made of rubber (FKM). The rotary ring 6 is made of a hard material such as ceramics. In this example, the rotary ring 6 is made of silicon carbide, and a reinforcing ring 19 made of a metal material (titanium or the like) is fitted to the outer periphery thereof. It is fixed. The reinforcing ring 19 is fitted and fixed to the outer peripheral portion of the rotating ring 6 except for the base end portion (front end portion) with which the second O-ring 18 comes into contact by shrink fitting or the like. By engaging the drive pin 21 screwed into the second holding portion 53 into the engagement hole 20, the rotation of the rotary ring 6 relative to the rotary shaft 2, that is, the sleeve 5 is prevented. The engagement hole 20 is of a size that allows the drive pin 21 to be engaged with a sufficient margin in the axial direction and the radial direction. , 18 is devised so as not to prevent displacement of the rotary ring 6 in the radial direction and the axial direction due to elastic deformation.

  As shown in FIG. 1, the spring 7 is held by an appropriate number of engaging recesses 22 formed at equal intervals in the circumferential direction in the spring holding portion 33 a of the spring retainer 33, and the rear surface (rear end surface) of the stationary ring 4. ) In the direction of the rotating ring (forward).

  As shown in FIGS. 1 and 2, the idle ring 8 includes an annular main body portion 81, a pressing portion 82 and a seal portion 83 that form a substantially identical annular shape and are integrally formed at the front and rear end portions on the inner peripheral side thereof. Thus, the pressing surface 82 a that is the end surface of the pressing portion 82 contacts the pressing surface 4 a that is the front end surface (front end surface) of the stationary ring 4, and the sealing surface 83 a that is the end surface of the sealing portion 83 is the front end of the rotating ring 6. In a state of contact with the seal surface 6a which is the surface (rear end surface) (see FIG. 2), the urging force (and back pressure described later) by the spring 7 is held between the stationary ring 4 and the rotating ring 6 by pressure. Yes. The idle ring 8 is configured such that an appropriate number of drive pins 23 projecting from the front end portion of the stationary ring 4 at equal intervals in the circumferential direction are engaged with engagement holes 24 formed in the main body 81, thereby In addition, in a state in which a relative displacement within a predetermined range is allowed in the axial direction and the radial direction, the relative rotation is maintained. An O-ring 25 that seals between the rings 4 and 8 (secondary seal) is interposed between the opposed end faces in the axial direction of the stationary ring 4 and the main body 81 of the idle ring 8 in a pinched manner. An appropriate number of communication holes 26 penetrating in the axial direction at equal intervals in the circumferential direction are formed in the main body 81 of the idle ring 8. Note that the idle ring 8 is made of a material softer than the constituent material of the rotary ring 6, and is made of carbon in this example.

Thus, the low friction material film 41 is formed on at least one of the pressing surfaces 4a and 82a which are contact surfaces between the stationary ring 4 and the idle ring 8. In this example, as shown in FIG. 2, a low-friction material film (polytetrafluoroethylene film) 41 made of polytetrafluoroethylene (PTFE) is formed at the contact portion of the stationary ring 4 with the floating ring 8. The surface of the film 41 is a pressing surface 4a. The low-friction material film 41 constituting the pressing surface 4a is coated on the stationary ring 4 and then surface-treated so that the surface roughness thereof is a 10-point average height (Rz) of 2 μm or less. By setting the surface roughness of the low friction material film 41, that is, the surface roughness of the pressing surface 4a to Rz2 μm or less, the static friction coefficient μ ′ between the pressing surfaces 4a and 82a is changed to the static friction coefficient between the sealing surfaces 6a and 83a. The ratio μ ′ / μ with respect to μ can be made as small as possible so as to be equivalent to or close to the inverse ratio W ₂ / W _{1 of} the contact surface load described above. When Rz> 2 μm, smooth sliding between the pressing surfaces 4a and 82a cannot be expected, and the static friction coefficient μ ′ cannot be reduced to a level that satisfies the above-described conditions. Incidentally, the surface treatment of the low-friction material film 41 is generally performed by lapping, and the surface roughness is usually Rz = 0.5 to 2 μm. In this example, the surface roughness of the low friction material film 41 is set to Rz = 1 μm by lapping. The film thickness of the low friction material film 41 is set to 10 to 20 μm. The stationary ring 4 is made of a metal material such as stainless steel in order to ensure adhesion with the polytetrafluoroethylene film 41. However, when the film thickness is less than 10 μm, the stationary ring 4 is peeled off from the metal base material (stationary ring 4). This is because if the film thickness exceeds 20 μm, the film hardness is low and the contact portion of the idle ring 8 may bite into the film 41. When the film thickness is 20 μm or less (10 μm or more), the hardness of the metal base material is reflected as the film hardness, and the insufficient hardness of the film itself is compensated. The low-friction material film 41 is formed at least in a range including an annular region on the stationary ring pressing surface 4a in which the free ring pressing surface 82a is relatively displaced in the radial direction due to pressure fluctuations in the sealed fluid region A. In this example, as shown in FIG. 2, the low-friction material film 41 is formed over a wide range including the region on the stationary ring pressing surface 4a with which the O-ring 25 contacts. is there.

  As shown in FIG. 1, the set plate 9 is attached to the wall portion 32 of the seal case 3 with a bolt 28 with one end engaged with the recess 27 formed in the main body 51 of the sleeve 5. Thus, the seal case 3 and the sleeve 5 are coupled so as not to be relatively movable in the axial direction and to be relatively non-rotatable. The stationary side includes the seal case 3 and a group of members (the stationary ring 4 and the spring 7) attached thereto. A floating ring 8 is provided between the stationary ring 4 and the rotating ring 6 with the sealing element and the sleeve 5 inserted and fixed to the rotating shaft 2 and a rotating side sealing element composed of a group of members (such as the rotating ring 6) attached thereto. They are integrally connected in a state where the pressure is held. The positional relationship in the axial direction between the seal case 3 and the sleeve 5 in a state where they are connected by the set plate 9, that is, the positional relationship in the axial direction between the stationary ring 4 and the rotating ring 6 in a state where the idle ring 8 is clamped, It is set to be the same as that in the operation state of the floating ring type mechanical seal. Therefore, the sealing plate including the floating ring 8 can be assembled by the set plate 9 in the same form as that of the floating ring-shaped mechanical seal. The set plate 9 is to be removed after the floating ring-shaped mechanical seal is incorporated in the shaft seal casing 1 and the rotary shaft 2, and the number thereof is set appropriately.

  By the way, the attachment of the free ring type mechanical seal to the shaft seal casing 1 and the rotary shaft 2 is usually performed in a fixed procedure for each of the constituent members constituting the stationary side seal element and the rotary side seal element including the idle ring 8 individually. It is done by incorporating in. The positional relationship between these structural members is an important factor that determines the function of the mechanical seal, and the incorporation of the structural members must be performed so that the positional relationship is appropriate. Therefore, it is extremely difficult to incorporate these many structural members into the rotating device while maintaining an appropriate positional relationship, and it is not rare that a predetermined sealing function is not exhibited due to poor integration. Similarly, maintenance work that requires removal and re-assembly from the rotating equipment is cumbersome and difficult.

  However, if the cartridge-type floating ring type mechanical seal as described above is used, the set plate 9 can be attached to and detached from the rotating device in the same state as the usage form of the mechanical seal. However, it is possible to appropriately and easily perform the assembling work into the rotating device, and the maintenance work can be easily performed. Such a point is a very significant merit in practical use in a floating ring type mechanical seal having a complicated structure in which a floating ring 8 is further added to the structure of a general mechanical seal.

  In the floating ring type mechanical seal configured as described above, the rotary shaft 2 (sleeve 5) in a state where the rotary ring 6 is allowed to be displaced in the axial direction and the radial direction via the first and second O-rings 17 and 18. Therefore, even when the fluid pressure (fluid pressure in the sealed fluid region A) is extremely high and a large pressure fluctuation occurs, the seal surfaces 6a, which are contact surfaces between the rotating ring 6 and the idle ring 8, are provided. The parallelism of 83a can be ensured and a good sealing function can be exhibited.

  That is, when the fluid pressure is extremely high, the rotating ring 6 may be deformed (distorted) in the radial direction and / or the axial direction due to the fluid pressure, and the seal surface 6a may be in an inappropriate shape. Is absorbed by the elasticity of the first O-ring 17 and / or the second O-ring 18, and the parallelism with the seal surface 83a of the idle ring 8 is lost due to the deformation of the seal surface 6a of the rotary ring 6. There is nothing. By the way, the contact pressure between the rotating ring 6 and the first O-ring 17 due to a large axial force acting on the rotating ring 6 (due to the fluid pressure acting directly on the rotating ring 6 and the back pressure and spring pressure of the stationary ring 4). And the frictional force between the two 6 and 17 is increased, and the second O-ring 18 does not smoothly absorb the radial deformation of the rotating ring 6 and the parallelism of the seal surfaces 6a and 83a may be impaired. However, such a fear does not occur at all by configuring the first O-ring 17 with a low friction material (in this example, PTFE). That is, since the first O-ring 17 is made of a low-friction material such as PTFE, the rotary ring 6 slips between the first O-ring 17 when a radial force is applied thereto. It is easily displaced and deformed in the radial direction, and the displacement and deformation are absorbed and relaxed by the elastic deformation of the second O-ring 18. Therefore, even when an axial force and / or a radial force that deforms the rotating ring 6 is applied, the parallelism of the seal surfaces 6a and 83a is not impaired.

Further, the rotating ring 6 is not fixed to the rotating shaft 2 as in the case of the conventional seal, and is held on the rotating shaft 2 in a state where axial displacement is allowed within the elastic deformation range of the first O-ring 17. Therefore, even when the fluid pressure is extremely high and the back pressure acting on the stationary ring 4 is high, the contact loads W ₁ and W ₂ described at the beginning are small because they are absorbed by the elastic deformation of the first O-ring 17. Thus, the number of rotation rings 6 is greatly reduced as compared with the case where the rotation ring 6 is fixed to the rotation shaft 2 as in the case of a conventional seal. As a result, the maximum static frictional force between the pressing surfaces 4a and 82a and between the sealing surfaces 6a and 83a is reduced, and the idle ring 8 tilts as described at the beginning even under conditions where the fluid pressure is high and greatly fluctuates. The seal surfaces 6a and 83a are not brought into contact with the outer diameter (for example, the state shown in FIG. 3B) or the inner diameter contact (for example, the state shown in FIG. 4E). Parallelism is maintained and a good sealing function is exhibited.

That is, since the maximum static frictional force at the contact portion between the idle ring 8 and the stationary ring 4 and the rotating ring 6 is given by the product of the contact load W ₁ , W ₂ and the static friction coefficient, the contact load W ₁ , W _{When 2} is small, the static friction coefficient (μ ′) between the pressing surfaces 4a and 82 is between the sealing surfaces 6a and 83a by configuring the pressing surface 4a of the stationary ring 4 with the low friction material film 41 described above. The first maximum static friction force μ ′ · W ₁ between the pressing surfaces 4a and 82a and the second maximum static friction force μ · between the seal surfaces 6a and 83a in combination with the static friction coefficient (μ) of W ₂ does not produce a large difference between them, and is equivalent or approximate. Therefore, in the case where the sealed fluid region A is under the boost status, by increasing the fluid pressure, the second frictional force F ₂ acting on the floating ring seal surface 83a reaches the second maximum static friction force mu · _{W 2} Te, when the slippage between the sealing surfaces 6a, 83a may have the same time or a short time difference, the floating ring first frictional force acting on the pressing surface 82a F ₁ also first maximum static friction force μ'· _{W 1} Thus, slip occurs between the pressing surfaces 4a and 82a. As a result, the idle ring 8 is not tilted at all, or even if it is tilted, it is immediately restored, and the seal surfaces 6a and 83a are not brought into contact with the inner diameter as shown in FIG. That is, the relative positions of the idle ring 1 and the stationary ring 4 and the rotating ring 6 only change from, for example, the entire contact state shown in FIG. 3A to the entire contact state shown in FIG. The parallelism of the surfaces 6a and 83a is maintained. Further, even when the sealed fluid region A is under the step-down situation, as well, by the lowering of the fluid pressure, the second frictional force f ₂ is and second maximum static friction force -μ acting on the floating ring seal surface 83a It reached W _2, when the slippage sealing surface 6a, between 83a is, at the same time or with a slight time difference, the first frictional force acting on the floating ring pressing surface 82a f ₁ be the first maximum static friction force - μ ′ · W ₁ is reached, and slip occurs between the pressing surfaces 4a and 82a. Therefore, as in the above-described pressure increase situation, the idle ring 8 is not tilted at all, or even if it is tilted, it is immediately restored, so that the seal surfaces 6a and 83a are brought into contact with the outer diameter as shown in FIG. Thus, the parallelism of the seal surfaces 6a and 83a is maintained. That is, the relative positions of the idle ring 1, the stationary ring 4, and the rotation 1 are merely displaced from, for example, the entire contact state shown in FIG. 4D to the entire contact state shown in FIG. In other words, the stick-slip cycle (pitch) for the first frictional force F ₁ , f ₁ generated by pressure fluctuation and the stick-slip cycle (pitch) for the second frictional force F ₂ , f ₂ are equivalent or approximate. This maintains the contact resistance balance between the idle ring 8 and the stationary ring 4 and the rotating ring 6, whereby the parallelism of the seal surfaces 6a and 83a is maintained regardless of pressure fluctuations, resulting in abnormal seal surfaces. Wear and abnormal leakage are prevented. Therefore, according to the idle ring type mechanical seal in which the rotary ring 6 is held in an axially displaceable state via the first O-ring 17 as described above, even under conditions where the fluid pressure is extremely high and the pressure fluctuation is large. A good sealing function will be exhibited.

Furthermore, since the pressing surface 4a of the stationary ring 4 is composed of the low friction material film 41 and the surface thereof is wrapped so that Rz ≦ 2 μm, the static friction coefficient μ ′ between the pressing surfaces 4a and 82a is The ratio μ ′ / μ to the static friction coefficient μ between the seal surfaces 6a and 83a can be made as small as possible so as to be equivalent to or approximate to the inverse ratio W ₂ / W _{1 of the} contact surface load. As a result, the parallelism of the seal surfaces 6a and 83a is maintained more effectively by maintaining the contact resistance balance between the idle ring 8 and the stationary ring 4 and the rotary ring 6, and abnormal wear of the seal surfaces 6a and 83a is reduced. Abnormal leakage can be prevented more reliably.

  In addition, due to the low processing accuracy and assembly accuracy of the rotary shaft 2 or the sleeve 5 to which the rotary ring 6 is attached and the deformation of the sleeve 5 due to heat from the rotary device side, the rotary ring posture becomes inappropriate, The parallelism of the seal surfaces 6a and 83a may be impaired. However, if the rotating ring 6 is held by the O-rings 17 and 18 so as to be displaceable in the axial direction and the radial direction as described above, the posture of the rotating ring 6 is corrected by the pressing force by the idle ring 8, and The parallelism of the seal surfaces 6a and 83a is not impaired by the accuracy failure.

  The configuration of the present invention is not limited to the above-described embodiment, and can be appropriately changed and improved without departing from the basic principle of the present invention. For example, the number and arrangement of the O-rings 17 and 18 that hold the rotary ring 6 can also be changed as appropriate according to the configuration of the mechanical seal and the sealing conditions. Further, the constituent material of the O-ring (first O-ring 17) or the low friction material film 41 that causes slipping between the rotary rings 6 is not limited to PTFE, and the constituent materials of the respective rings 4, 6, and 8 In consideration of this relationship, it can be selected appropriately. For example, polyether ether ketone (PEEK) can be used as a constituent material of the low friction material film 41.

It is the vertical side view which showed an example of the idle ring type mechanical seal which concerns on this invention. FIG. 2 is an enlarged detailed view showing a main part of FIG. 1. It is explanatory drawing which shows the relative displacement of the idle ring at the time of pressure | voltage rise, a rotation ring, and a stationary ring. It is explanatory drawing which shows the relative displacement of the idle ring at the time of pressure reduction, a rotation ring, and a stationary ring. It is a graph which shows the relationship between the contact surface load and friction force which act on the contact surface with the rotation ring of a free ring, and a stationary ring, and fluid pressure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Shaft seal casing, 2 ... Rotating shaft, 3 ... Seal case, 4 ... Stationary ring, 4a, 82a ... Pressing surface (contact surface of stationary ring and free ring), 5 ... Sleeve, 6 ... Rotating ring, 6a 83a ... sealing surface (contact surface between the rotating ring and the free ring), 7 ... spring, 8 ... free ring, 9 ... set plate, 10 ... O ring, 17 ... first O ring (in the radial displacement of the rotating ring) 18 ... second O-ring (O-ring that functions as a secondary seal), 41 ... low friction material film, A ... sealed fluid region, B ... non-sealed fluid region (atmospheric region) ).

Claims (7)

Relative rotation of the floating ring with respect to the stationary ring is prevented between the rotating ring provided on the rotating shaft and the stationary ring that is axially movable on the seal case and biased in the rotating ring direction. In the floating ring type mechanical seal that is held under pressure in the state,
The rotating ring is held on the rotating shaft through a plurality of O-rings including those functioning as secondary seals in a state in which they can be displaced in the axial direction and the radial direction within the elastic deformation range of these O-rings, and these An idle ring type mechanical seal characterized in that an O-ring that causes slippage at least with respect to a radial displacement of the rotating ring is made of a low-friction elastic material. The free-ring-type mechanical seal according to claim 1, wherein the O-ring that causes the slip is made of polytetrafluoroethylene. The idle ring type mechanical seal according to claim 1, wherein a low friction material film is formed on at least one of contact surfaces of the idle ring and the stationary ring. The idle ring type mechanical seal according to claim 3, wherein the low friction material film is a polytetrafluoroethylene film. The idle ring type mechanical seal according to claim 3 or 4, wherein the surface roughness of the low-friction material film is 10-point average height of 2 µm or less. The idle ring type mechanical seal according to claim 3, 4 or 5, wherein the film thickness of the low friction material film is 10 to 20 µm. A stationary side sealing element consisting of a seal case and a group of members attached thereto, a sleeve inserted through and fixed to the rotary shaft, and a rotational side sealing element consisting of a group of members attached thereto are allowed to float between the stationary ring and the rotary ring. A cartridge-type mechanical tool constructed so that it can be integrally connected by a detachable set plate in a state where the ring is held under pressure. Claims 1, 2, 3, and 3 The floating ring-shaped mechanical seal according to claim 4, claim 5, or claim 6.