JPH08334174A - Noncontact mechanical seal - Google Patents

Abstract

PURPOSE: To exhibit and maintain sealing function by an seal ring and secondary sealing function by a holding annulus side O-ring for a long period in a good condition regardless of a seal condition. CONSTITUTION: In a noncontact mechanical seal formed in such constitution that a rotary seal ring and a stationary seal annulus 4 are relatively rotated in a noncontact condition, a space between the front surface 5d of the push- pressing part of a holding annulus 5 and the back surface 4d of the stationary seal annulus 4 are held in a secondary sealed noncontact condition by a holding annulus side O-ring held to an annular groove 11 formed on the front surface 5d of the push-pressing part 5b. An annular O-ring holding part 5c which is protruded on the front surface 5d of the push-pressing part 5b, which is inserted in the annular recessed part 4c of the static enclosed annulus 4 having few diameter direction clearance in a loosely fitted condition while being formed in continuity to the inner diameter side wall surface of the annular groove 11. The inner diameter d of the annular groove 11 is set to D+0.5mm<=d<=D +0.4mm in relation to the diameter D of the held part of the holding annulus 5 which is held to a seal case 1 through a case side O-ring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact type mechanical device suitable for use in a rotating machine such as a turbine, a blower, a centrifugal compressor, which mainly handles gases (nitrogen, argon, hydrogen, natural gas, air, etc.). It is about seals.

[0002]

2. Description of the Related Art As a conventional non-contact type mechanical seal of this type, as shown in FIGS. 7 and 8, a rotary seal ring 3 fixed to a rotary shaft 2 and a rotary shaft 2 are loosely fitted. A cylindrical held portion 5a that is inserted and held in the seal case 1 while being secondarily sealed via a case-side O-ring 7 so as to be movable in the axial direction, and an annular pressing portion 5 formed at the front end portion thereof.
a retaining ring 5 having an L-shaped cross section and a seal case 1
A spring 6 interposed between the rotary seal ring 3 and the holding ring 5, and a spring 6 interposed between the rotary ring 2 and the pressing portion 5b of the holding ring 5.
A stationary seal ring 4 which is loosely fitted to the rotary seal ring 3 via a retaining ring 5 by a spring 6 and a ring having a rectangular cross section or a dovetail groove formed on the front surface of the pressing portion 5b. A retaining ring side O-ring 10 which is retained in the groove 11 and retains a secondary seal between the front surface 5d of the pressing portion 5b and the rear surface 4d of the stationary seal ring 4 in a non-contact state. At the sealing end faces 3a, 4a, which are the end faces of the rotary seal ring 3 and the stationary seal ring 4 facing each other, the relative rotation action and the action of the dynamic pressure generating groove 3b formed in the one seal end face 3a cause the seal end faces 3a, 4a. While keeping the non-contact state,
A structure configured to seal a sealed fluid region H which is an outer peripheral side region of the sealed end faces 3a and 4a and a non-sealed fluid region L which is an inner peripheral side region (hereinafter referred to as "conventional seal").
Is well known.

By the way, the rotary seal ring 3, the stationary seal ring 4 and the holding ring 5 are made of different materials having different thermal expansion coefficients and Young's moduli because of their different functions. For example, the rotary seal ring 3 is made of a super-hard material such as WC or SiC, the stationary seal ring 4 is made of softer carbon than the constituent material of the rotary seal ring 3, and the holding ring 5 is made of a metal material such as SUS304 or Ti. It is composed of. On the other hand, the rotary seal ring 3, the stationary seal ring 4, and the holding ring 5 are subject to heat distortion and pressure distortion due to heat generated during operation and system pressure of the device (hereinafter, “distortion” means these distortions). However, these strain amounts and strain states are not the same, and differ from each other due to the difference in constituent materials. In particular, the amount of strain of the retaining ring 5 is extremely larger than those of the rotary seal ring 3 and the stationary seal ring 4 due to the constituent materials.

Therefore, in the traditional non-contact type mechanical seal in which the stationary seal ring 4 and the retaining ring 5 are integrated by fitting or the like, their distortions interfere with each other at the contact portions of both rings 4, 5. As a result, the stationary seal ring 4 is strongly affected by the strain of the retaining ring 5, and exhibits a completely different strain state from the strain of itself. Therefore, the smoothness of the stationary side sealing end surface 4a and the concentricity and parallelism with respect to the rotating side sealing end surface 3a are impaired,
The dynamic pressure generated between the sealing end faces 3a, 4a becomes non-uniform, or in extreme cases, the dynamic pressure generation failure or the sealing end faces 3a, 4a occurs.
An unexpected situation such as local contact of a occurs, which causes a problem that a good sealing function cannot be exhibited for a long period of time. In particular, such a problem remarkably occurs under high pressure and high speed conditions, which makes it more difficult to use under such sealing conditions.

Therefore, in the conventional seal, as shown in FIGS. 7 and 8, by making a part of the retaining ring side O-ring 10 protrude from the annular groove 11, the rear face 4d of the stationary seal ring 4 and the front face of the retaining ring 5 are made. A small clearance 12 is formed between the stationary seal ring 4 and the stationary ring 5d so as not to be adversely affected by the distortion of the retaining ring 5.
That is, since the stationary seal ring 4 and the retaining ring 5 are only in indirect contact with each other via the retaining ring side O-ring 10,
Even when different strains occur in both rings 4 and 5 due to pressure fluctuations, temperature changes, etc., those strains are retained in the O-ring 10 on the retaining ring side.
The static sealing rings 4 are not absorbed by the elastic deformation and do not interfere with each other, and the stationary sealing ring 4 is not adversely affected by the distortion of the holding ring 5. The holding ring side O-ring 10 is generally made of rubber or the like having incompressibility and high friction.

[0006]

However, in the conventional seal, since the stationary seal ring 4 and the retaining ring 5 are not integrated like the traditional non-contact type mechanical seal, both rings 4, 5 are not integrated. There is a risk of being installed in a relatively eccentric state. By the way, the holding ring side O-ring 10 interposed between the stationary seal ring 4 and the holding ring 5 is made of a high friction material as described above, and the two rings 4, 5 and the holding ring side O-ring 10 are connected to each other. Since slippage is unlikely to occur at the contact point, once the both rings 4 and 5 are incorporated in a relatively eccentric positional relationship, fluctuations in the positional relationship are allowed by elastic deformation of the retaining ring side O-ring 10. Nothing more than On the other hand, the holding ring side O-ring 10 is in contact with the stationary seal ring 4 and the holding ring 5 in a non-slip state, and the holding ring side O-ring 10 is made of an incompressible material as described above. Therefore, the elastic deformation limit amount of the holding ring side O-ring 10 is extremely small. Therefore, when the relative eccentricity of both rings 4 and 5 at the time of installation is large, this cannot be absorbed by the elastic deformation of the holding ring side O-ring 10, that is, both rings 4 and 5 have a proper positional relationship. The stationary seal ring 4
The seal end surface 4a of the rotary seal ring 3 is operated with a large inclination with respect to the seal end surface 3a of the rotary seal ring 3,
There arises a problem that the good sealing function of No. 4 cannot be exhibited. In an extreme case, the two sealing end surfaces 4a and 5a locally contact with each other to cause abnormal heat generation, and the retaining ring side O-ring 10 prevents distortion interference between the stationary sealing ring 4 and the retaining ring 5. In addition to disappearing, the stationary seal ring 4, which is softer than the rotary seal ring 3, may be damaged.

Further, as described above, since the holding ring 5 has a larger strain than the stationary sealing ring 4, the stationary sealing ring 5 and the holding ring side O-ring 1 may depend on the sealing conditions such as the fluid temperature.
The contact point with 0 may be largely displaced in the inner diameter direction. In such a case, the conventional seal does not have any means for preventing the retaining ring side O-ring 10 from displacing in the inner diameter direction.
The ring 10 pops out from the annular groove 11 in the inner diameter direction,
In an extreme case, the ring groove 11 may fall off.
Also, depending on the sealing conditions such as the property of the fluid and the temperature, the holding ring side O-ring 10 deteriorates due to contact with the fluid, and its elasticity decreases, so that the holding ring side O-ring 10 is placed between the two rings 4 and 5. There is a risk that it may not be able to deform following the displacement. Further, due to the vibration of the equipment, pressure fluctuation, etc., the pressing force of the holding ring 5 of the holding ring side O-ring 10 against the stationary seal ring 4, that is, both rings 4,
There is a possibility that the clamping pressure of the O-ring 10 on the retaining ring side due to 5 may decrease. Therefore, from the above, there is a problem that the secondary sealing function of the retaining ring side O-ring 10 cannot be satisfactorily exhibited and maintained for a long period of time.

The present invention has been made in view of the above points, and makes it possible to satisfactorily exhibit and maintain the sealing function of the sealing ring and the secondary sealing function of the holding ring side O-ring for a long period of time regardless of the sealing conditions. It is an object of the present invention to provide a non-contact type mechanical seal.

[0009]

According to the present invention, there is provided a rotary seal ring fixed to a rotary shaft, and a cylinder which is movably held in an axial direction in a state of being secondarily sealed in a seal case through a case side O-ring. Holding ring having a ring-shaped to-be-held portion and an annular pressing portion formed at the front end thereof, a stationary sealing ring which is biased to the rotary sealing ring via the holding ring, and a front surface of the pressing portion. And a retaining ring side O-ring which is retained in the formed annular groove and retains a secondary seal between the front face of the pressing portion and the rear face of the stationary seal ring in a non-contact state, thereby providing a rotary seal. By sealingly rotating the sealing end faces, which are the opposing end faces of the ring and the stationary seal ring, in a non-contact state, the sealed fluid region, which is the outer peripheral region of the sealed end face, and the non-sealing fluid region, which is the inner peripheral region, are sealed. In a non-contact mechanical seal configured to In order to achieve the above object, in particular, on the front surface of the pressing portion, an annular recess formed in the inner peripheral portion of the stationary sealing ring, which is continuous with the inner diameter side wall surface of the annular groove, is provided with a slight radial clearance. A ring-shaped O-ring holding portion that protrudes in a fitting shape is provided to project, and the inner diameter d of the annular groove is D + 0.5 mm ≦ d ≦ D + 4.0 with respect to the outer diameter D of the held portion.
It is proposed that the structure be set to be mm.

[0010]

The O-ring holding portion is loosely fitted into the annular recess formed in the inner peripheral portion of the stationary sealing ring with a slight radial gap, and the O-ring holding portion extends radially between the stationary sealing ring and the holding ring. Since the positional relationship does not fluctuate greatly, even if the temporary seal and the stationary ring are incorporated in a relatively eccentric positional relationship, the relative eccentricity of both rings is extremely small. Therefore, the relative eccentricity of the two rings can be sufficiently absorbed by the elastic deformation of the holding ring side O-ring, and the stationary seal ring is operated in a state in which the sealing end face of the stationary seal ring is largely inclined with respect to the sealing end face of the rotary seal ring. Therefore, the sealing function of the sealing ring is not deteriorated, and both sealing end faces do not locally contact with each other.

Further, the displacement and deformation of the holding ring side O-ring in the inner diameter direction due to relative displacement between the stationary seal ring and the holding ring, vibration, etc. are restricted within a certain range by the O-ring holding portion. Therefore, since the O-ring holding portion is continuous with the inner diameter side wall surface of the annular groove, the O-ring on the holding ring side does not protrude or fall out from the annular groove in the inner diameter direction.

By the way, the fluid pressure of the sealed fluid region acts on the retaining ring in a uniform distribution, and as a result, a pressing force for separating it from the stationary sealing ring acts on the front surface of the retaining ring, A pressing force acts on the back surface of the retaining ring to press it against the stationary sealing ring. The pressing force acting on the front surface is the outer diameter of the retaining ring and the diameter of the secondary sealing portion of the retaining ring side O-ring (that is, the annular region where the retaining ring side O-ring and the stationary sealing ring or the retaining ring contact). (Hereinafter referred to as “first seal diameter”), the pressing force acting on the back surface is determined by the outer diameter of the retaining ring and the case-side O-ring secondary seal location (that is, case-side O-ring). It is determined by the pressure receiving area specified by the diameter (hereinafter referred to as the "second seal diameter") of the annular region in contact with the held portion of the retaining ring, so the magnitude relationship between the two pressing forces is the first seal diameter. It is inversely proportional to the size relationship of the second seal diameter. On the other hand, the second seal diameter is always constant and coincides with the outer diameter D of the held portion, but the first seal diameter is the O-ring of the retaining ring side due to the relative displacement between the stationary sealing ring and the retaining ring. It changes due to deformation and displacement. However, since such deformation and displacement are restricted within the annular groove by the O-ring holding portion as described above, the first seal diameter does not become smaller than the inner diameter d of the annular groove. In other words,
When the first seal diameter matches the inner diameter d of the annular groove, the fluid pressure receiving area on the front surface of the retaining ring is maximized, and the pressing force acting on the front surface is maximized. Therefore,
As described above, when the inner diameter d of the annular groove is designed to be larger than the outer diameter D of the held portion by a predetermined amount, the pressing force acting on the front surface of the holding ring is always maintained regardless of the fluctuation of the first seal diameter. It becomes smaller than the pressing force acting on the back surface, and the retaining ring is pressed against the stationary sealing ring. As a result, the O-ring on the retaining ring side is always maintained in a state of being pinched between the stationary seal ring and the retaining ring, and in combination with the action of the O-ring retaining section described above, the retaining ring side O-ring is retained. The secondary sealing function of the O-ring will be satisfactorily exhibited and maintained. The inner diameter d of the annular groove is D + 0.5 mm ≦ d ≦ D + 4.0
The reason for setting in the range of mm is as follows. That is, when d <D + 0.5 mm, the difference between the pressing force acting on the front surface of the retaining ring and the pressing force acting on the rear surface is not so remarkable, and depending on the sealing conditions, the retaining ring may not move to the stationary sealing ring. In some cases, the pressing force, that is, the holding ring side O-ring holding pressure becomes insufficient, and a good secondary seal cannot be exerted. On the other hand, on the back surface of the stationary seal ring, a pressing force (force that presses the stationary seal ring against the rotary seal ring) acts due to the fluid pressure acting in an even distribution, and the magnitude of this pressing force is Since it is determined by one seal diameter, that is, the inner diameter d of the annular groove, when d> D + 4.0 mm, the pressing force acting on the back surface of the stationary seal ring causes the static seal ring to move due to the dynamic pressure generated between both seal rings. It becomes smaller than necessary compared to the pressing force to separate it from the rotary seal ring, the balance of both pressing forces is lost, and the torsional strain of the stationary seal ring becomes large due to the moment due to the difference in the pressing force. There is a risk of local contact between the two sealing end faces. Further, the difference between the pressing force acting on the front surface of the retaining ring and the pressing force acting on the rear surface thereof, that is, the pressing force of the retaining ring against the stationary sealing ring becomes excessive depending on the sealing conditions, and the retaining ring side O-ring becomes unnecessarily large. There is a possibility that the followability due to the relative displacement between the stationary seal ring and the retaining ring is deteriorated as well as the secondary sealing function due to being pinched. Therefore, in order to properly hold the clamping pressure of the O-ring on the retaining ring side and balance the pressing force acting on the stationary seal ring, the inner diameter d of the annular groove is D + 0.5 m.
It is necessary to set it appropriately within the range of m ≦ d ≦ D + 4.0 mm according to the sealing condition and the like.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be specifically described below based on the embodiments shown in FIGS.

As shown in FIG. 1, the non-contact type mechanical seal of this embodiment has a ring-shaped rotary seal ring 3 fixed to a seal case 1 and a rotary shaft 2 such as a turbine shaft penetrating the seal case 1. An annular stationary seal ring 4 that directly faces the rotary seal ring 3 in the axial direction, and a holding ring 5 held by the seal case 1 on the back side of the stationary seal ring 4.
A plurality of coil-shaped springs 6 (only one is shown) interposed between the seal case 1 and the holding ring 5.

As shown in FIG. 1, the seal case 1 has a cylindrical guide portion 1a and an annular retainer portion 1b. The rotating shaft 2 concentrically penetrates the guide portion 1a and the retainer portion 1b.

The rotary seal ring 3 is made of a super-hard material such as WC or SiC. As shown in FIGS. 1 and 2, the end face 3a axially opposed to the stationary seal ring 4 has a sealed fluid. A dynamic pressure generating groove 3b having an appropriate shape such as a spiral shape that opens to the outer peripheral portion facing the area H is formed. By the action of the dynamic pressure generating groove 3b, a dynamic pressure is generated with the relative rotation of the both sealing rings 3 and 4, and a fluid film is interposed between the sealing end faces 3a and 4a which are the opposite end faces of the both sealing rings 3 and 4. Hold the formed non-contact state. Thus, in the portion where the fluid film is formed, a sealed fluid region (for example, a high-pressure gas region in a machine such as a turbine) H which is an outer peripheral region of the sealed end faces 3a and 4a and a non-inner peripheral region thereof. A seal is provided between a sealed fluid region (for example, an atmospheric region outside the machine such as a turbine) L.

The stationary seal ring 4 is made of carbon, which is relatively softer than the constituent material of the rotary seal ring 3, and as shown in FIGS. 1 and 2, the guide portion 1a of the seal case 1 is extremely minute. It is internally fitted and held so as to be movable in the axial direction with a gap. That is, an annular convex portion 4b and an annular concave portion 4c having a diameter larger than the outer diameter and the inner diameter of the sealing end surface 4a are formed on the outer peripheral portion and the inner peripheral portion on the back side of the stationary sealing ring 4, and the annular convex portion 4b is formed. , For example JIS-B0401
Guide part 1a with a dimensional tolerance of about clearance fit
The radial displacement of the stationary seal ring 4 between the outer peripheral surface of the annular convex portion 4b and the inner peripheral surface of the guide portion 1a is prevented as much as possible by fitting it into Is formed so that a very small gap is formed to allow the passage of the. This gap is set appropriately according to the diameter of the stationary seal ring 4, the sealing conditions, etc., but in general,
It is preferable that the difference between the outer diameter of the annular convex portion 4b and the inner diameter of the guide portion 1a is set to about 10 to 100 μm.

The holding ring 5 is made of a metal material such as SUS304 and Ti. As shown in FIGS. 1 and 2, the holding ring 5 has a cylindrical holding portion 5a and an annular pressing portion 5b formed at the front end thereof. And has an L-shaped cross section. As shown in FIG. 2, the holding ring 5 is configured such that the held portion 5a is inserted and held in the inner peripheral portion of the retainer portion 1b of the seal case 1 via the rubber case-side O-ring 7 so that the seal case 1 is held. In addition, it is held so as to be movable in the axial direction in a state where a secondary seal is made between the two.

The stationary seal ring 4 is, as shown in FIG.
A proper number of detent pins (only one is shown) 8 to be planted in the pressing portion 5b of the retaining ring 5 are inserted into and engaged with the retaining ring 5 so that the retaining ring 5 cannot rotate relative to the retaining ring 5. Further, as shown in FIG. 2, the retaining ring 5 has a proper number of detent pins 9 (only one is shown) 9 to be planted in the retaining ring 5, which are inserted into the retainer portion 1b of the sealing case 1 in a protruding manner so that the retaining case 5 is sealed. It is impossible to rotate relative to 1. These detent pins 8 and 9 may be common. For example, one detent pin 8 is abolished, the other detent pin 9 is supported by the retaining ring 5 in a penetrating manner, and both ends thereof are urged and engaged with the retainer portion 1b and the stationary sealing ring 4. You may

As shown in FIGS. 1 and 2, each spring 6 is interposed between the retainer portion 1b of the seal case 1 and the pressing portion 5b of the retaining ring 5 to rotate the retaining ring 5 in the axial direction. It is pressed and urged in the direction toward the sealing ring 3.

Thus, between the stationary seal ring 4 and the retaining ring 5, as shown in FIGS. 1 to 3, the retaining ring side O-ring is located between the opposing end faces 4d and 5d of the two rings 4 and 5 in the axial direction. By interposing 10, the secondary seal is maintained in a non-contact state. That is, a concentric annular groove 11 is formed on the front surface of the retaining ring 5, that is, the front surface 5d of the pressing portion 5b, and the retaining ring side O-ring 10 made of rubber is fitted and retained in the annular groove 11 in a slightly protruding state. By the stationary seal ring 4
Together with the biasing action of the spring 6,
In a sealed state with an appropriate clearance 12 between them, the rotary seal ring 3 is urged and held to be pressed. The holding ring side O-ring 10 is held in a non-contact state with the outer diameter side wall surface 14 of the annular groove 11.

Further, on the front surface 5d of the pressing portion 5b, as shown in FIGS. 2 and 3, a slight radial gap S is formed in the annular recess 4c of the stationary seal ring 4, which is continuous with the inner diameter side wall surface 13 of the annular groove 11.
O-ring holding part 5c that has a protrusion and is inserted in a loose fit
And the holding ring side O-ring 10 has an annular groove 11
The inner diameter d, that is, the outer diameter of the O-ring holding portion 5c, is prevented from being deformed or displaced in the inner diameter direction. In addition,
In this radial gap, the gap S is such that both parts 4c, 5c are both rings 4, 5
It is preferable to set it as small as possible within the range where interference does not occur depending on the distortion of No. 3, and generally, it is set so that S = 0.3 to 0.5 mm when both parts 4c and 5c are concentric. Preferably.

Further, the inner diameter d of the annular groove 11 is the same as in a known non-contact type mechanical seal including a conventional seal, and the pressure relationship acting on the front surface and the back surface of the stationary sealing ring 4 does not cause the two sealing end surfaces 3a and 4a to be non-contact. Although it is set on condition that the relationship of holding in contact is established, in the non-contact mechanical seal according to the present invention, D + 0.5 mm is further added to the outer diameter D of the held portion 5a of the holding ring 5. ≤d≤D +
It is set to be 4.0 mm.

That is, the pressing forces F ₁ and F ₂ due to the dynamic pressure and the static pressure having the pressure distribution as shown in FIG. 4A act on the front surface and the back surface of the stationary seal ring 4, but the pressing force F ₁ Is
Acting on the sealing end surface 4a of the stationary sealing ring 4,
This is due to the dynamic pressure generated between the sealed end faces 3a and 4a, and the pressing force F ₂ is the annular region facing the sealed fluid region H on the back surface of the stationary seal ring 4, that is, the portion corresponding to the outer peripheral surface of the sealed end face 4a. This is due to the fluid pressure in the sealed fluid region H that acts in a uniform distribution in the annular region from the holding ring side O-ring 10 to the secondary sealing position. The outer diameter of the stationary seal ring 4 because it has become larger than the outer diameter of the sealing end faces 4a, even pressure to the front and rear of the outer peripheral side of the annular projection 4b _{F'1, F'2} is acts Since these pressing forces F ′ ₁ and F ′ ₂ are opposite in direction and have the same size, they cancel each other, so that the pressing force F ′ is applied to the stationary seal ring 4.
Only ₁ , F ₂ shall act. And the pressing force F
₂ is determined by the pressure receiving area specified by the outer diameter of the sealed end surface 4a and the first seal diameter d ₀ which is the diameter of the secondary sealing point by the holding ring side O-ring 10. Further, the secondary sealing location of the retaining ring side O-ring 10 varies due to the deformation and displacement of the retaining ring side O-ring 10, but its variation in the inner diameter direction is restricted by the action of the O-ring retaining portion 5c as described above. Therefore, the first seal diameter d ₀ does not become smaller than the inner diameter d of the annular groove 11,
It will vary within the range of d ₀ ≧ d. Therefore, the pressing force F ₂ becomes maximum when the first seal diameter d ₀ is set to the lower limit value of the fluctuation range, that is, when d ₀ = d, and the pressing force F _{2 at} the maximum is the dynamic pressure. Pressing force due to
If it is smaller than ₁ , the two sealed end faces 3a and 4a are always held in a non-contact state. That is, it is an indispensable condition in the non-contact type mechanical seal that the both sealing end faces 3a and 4a are held in the non-contact state, so that the annular groove 1 corresponding to the lower limit value of the first seal diameter d ₀ is formed.
The inner diameter d of 1 is, as a general design matter in the non-contact mechanical seal, naturally designed so that F ₁ > F _2, and even in the non-contact mechanical seal according to the present invention, Designed to be. On the other hand, within the range satisfying such a condition (F ₁ > F ₂ ), the inner diameter d of the annular groove 11 is set to the second seal diameter which is the diameter of the secondary seal portion by the case side O-ring 7, that is, the held portion 5a. It is sufficiently possible to make the diameter larger than the outer diameter D in a certain range. Therefore, in the non-contact mechanical seal according to the present invention, the inner diameter d of the annular groove 11 is set to be larger than the outer diameter D of the held portion 5a within the range of 0.5 to 4.0 mm as described above. It is set.

Further, in this embodiment, the annular groove 11 is
The inner diameter side wall surface 13 is formed so that the groove back side portion 13b has a larger diameter than the groove mouth side portion 13a.
In the above, the holding ring side O-ring 10 is configured to be supported by the groove mouth side portion 13a in a non-contact state. That is, as shown in FIG. 3, the inner diameter side wall surface 13 of the annular groove 11 is used as an inclined surface that gradually reduces in diameter in the groove mouth direction, and the inner groove portion 10a of the retaining ring side O-ring 10 is separated from the groove mouth side portion 13a. The groove back side portion 13b is supported. The O-ring holding portion 5c is formed on the groove opening side portion 13a.
Inner diameter d of the annular groove 11 described above with the diameter of the end of the groove mouth side portion 13a.
Has been identified.

In the non-contact type mechanical seal constructed as described above, the O-ring holding portion 5c has a slight radial gap S in the annular recess 4c formed in the inner peripheral portion of the stationary seal ring 4. Since it is inserted loosely and the positional relationship between the stationary seal ring 4 and the retaining ring 5 in the radial direction does not fluctuate significantly, the provisional command, the positions where both rings 4 and 5 are relatively eccentric Even if they are incorporated by the relationship, the relative eccentricity of both rings 4 and 5 is extremely small. Therefore, both rings 4,5
Relative eccentricity can be sufficiently absorbed by elastic deformation of the O-ring 10 on the retaining ring side, and the operation is performed with the sealing end surface 4a of the stationary sealing ring 4 largely inclined with respect to the sealing end surface 3a of the rotary sealing ring 3. Therefore, the sealing function of the sealing rings 3 and 4 does not deteriorate, and neither of the sealing end faces 3a and 4a locally contacts.

Further, the displacement and deformation of the holding ring side O-ring 10 in the inner diameter direction due to the relative displacement between the stationary seal ring 4 and the holding ring 5, vibration, etc. are restricted within a certain range by the O-ring holding portion 5c. . Therefore, since the O-ring holding portion 5c is continuous with the inner diameter side wall surface 13 of the annular groove 11, the O-ring 10 on the holding ring side does not protrude or fall out of the annular groove 11 in the inner diameter direction.

The front and back surfaces of the retaining ring 5 are covered with
Pressing force F due to fluid pressure P in sealing fluid region H₃, F_FourMade by
However, as shown in FIG. 4 (B), the pressing force F₃Holds
An annular region facing the sealed fluid region H on the front surface of the ring 5,
That is, from the outer peripheral portion of the pressing portion 5b to the holding ring side O-ring 10
Due to the uniform distribution in the annular area leading to the secondary sealing point due to
Due to the acting fluid pressure P, the pressing force F_FourIs
An annular region facing the sealed fluid region H on the back surface of the retaining ring 5.
Area, that is, the outer circumference of the pressing portion 5b to the case side O-ring
No uniform distribution in the annular area up to the secondary sealing point according to 7.
This is due to the fluid pressure P acting as a function. And press
Force F₃Is the first seal diameter d₀And the outer diameter D of the pressing portion 5b₁When
Given by the pressure receiving area specified by₃= Pπ
((D₁) ²-(D₀)²) / 4. Also, the pressing force
F_FourIs the second seal diameter D, which is the outer diameter of the pressed portion 5a, and
Outer diameter D of pressure part 5b₁Depending on the pressure receiving area specified by
Yes, F_Four= Pπ ((D₁)²-(D)²) / 4
It On the other hand, the first seal diameter d₀Of the O-ring 10 on the retaining ring side
Although it fluctuates due to deformation and displacement, as mentioned above, the annular groove 1
It does not become smaller than the inner diameter d of 1. Like this
₀Since ≧ d and d> D as described above, the first series
Diameter d₀Even when fluctuates, always F₃<F_FourTona
The difference between these pressing forces (F_Four-F₃), The retaining ring 5
It will be pressed against the stationary seal ring 4. Accordingly
And acts on the front and back surfaces of the stationary seal ring 4 as described above.
Pressing force F₁, F₂Is of course F₁> F₂Seki
Taking into account that the stationary seal ring 4 and the retaining ring 5,
Are always held together. As a result, the retaining ring side
The O-ring 10 is always clamped between the rings 4 and 5.
Is retained in the O-ring 10 on the retaining ring side,
Even if vibration of the equipment occurs, make sure that the space between both rings 4 and 5 is good.
Secondary seal. And D + 0.5 mm ≦ d ≦ D +
By setting it to 4.0 mm, the static seal ring 4 is pushed.
Discipline (F_Four-F₃) Is the sealing condition (O ring on the retaining ring side)
Irrespective of changes in the properties of the ring 10, pressure fluctuations, etc.)
Large enough to be able to clamp the side O-ring 10 properly.
O-ring 1 on the retaining ring side
Secondary function between both rings 4 and 5 by 0 and relative between both rings 4 and 5
The function of following the displacement is exhibited well.
Further, the pressing force F acting on the front surface and the back surface of the stationary seal ring 4 is
₁, F₂But F₁> F₂Balance while satisfying the conditions of
The pressure difference (F₁-F₂) To the moment
The torsional strain of the stationary seal ring 4 becomes larger and the both seal ends
There is no risk of local contact between the surfaces 3a and 4a.

From the above, the retaining ring side O-ring 10
The secondary sealing function by the sealant and the sealing function by the sealing rings 3, 4 are excellently exhibited, and the sealed fluid region H and the non-sealed fluid region can be maintained for a long period of time regardless of the assembling form of both rings 4, 5 and the sealing conditions. Good sealing with L can be performed.

By the way, in the conventional seal, as shown in FIG. 8, the annular groove 11 has a rectangular cross section in which the inner diameter wall surface 13 is a plane parallel to the axis (FIG. (A)) or the inner diameter wall surface 13.
With a dovetail groove in which the diameter gradually increases toward the inner side of the groove ((B) in the same figure)
Therefore, the strains of the stationary sealing ring 4 and the retaining ring 5 may not be absorbed by the elastic deformation of the retaining ring side O-ring 10, and mutual interference of these strains cannot be completely eliminated.

That is, the contact point of the holding ring side O-ring 10 (hereinafter referred to as "first contact point") C ₁ on the back surface 4d of the stationary seal ring 4 and the contact point of the holding ring side O-ring 10 on the holding ring 5, that is, the ring shape. When the retaining ring side O-ring 10 is in contact with the bottom wall surface 15 of the groove 11 (hereinafter, referred to as “second contact point”) C ₂ , when both rings 4 and 5 are distorted, the strain amounts are as described above. As described above, there is a large difference, which results in relative displacement in the radial direction. On the other hand, the holding ring side O-ring 10 is made of a material having a high friction coefficient such as rubber, and the rear surface 4d of the stationary seal ring 4 and the annular groove 11 are made.
Since it is pinched between the bottom wall surface 15 and the bottom wall surface 15, it is difficult for the contact points C ₁ and C ₂ to slip, and the contact point C
It will be deformed with the relative displacement of ₁ and C ₂ . Therefore, as shown by the chain line in FIG. 8, when the first contact point C ₁ is displaced relative to the second contact point C ₂ in the inner diameter direction, the first contact point C ₁ comes into contact with the displacement along with the displacement of the first contact point C _1. The retaining ring side O-ring portion is elastically deformed in the inner diameter direction, but the retaining ring side O-ring portion (hereinafter referred to as “inner groove portion”) 10a in the annular groove 11 is deformed in the inner diameter direction. Since the retaining ring side O-ring 10 is prevented from being deformed by the inner diameter side wall surface 13, the deformation of the retaining ring side O-ring 10 is slightly reduced from the annular groove 11 in combination with the deformation of the retaining ring side O-ring 10. The holding ring side O-ring portion (hereinafter, referred to as “outer groove portion”) 10b protruding inward is only allowed within a range in which it can be elastically deformed. However, since the outer groove portion 10b is extremely small, the range in which the retaining ring side O-ring 10 can be deformed following the displacement of the first contact portion C ₁ (hereinafter referred to as "following deformation limit") is extremely small. Few. Therefore, the relative displacement amount of the contact points C ₁ and C ₂ due to the strain of both rings 4 and 5 may exceed the follow-up deformation limit of the retaining ring side O-ring 10. In such a case, the strain of both rings 4 and 5 may be increased. May not be absorbed by the deformation of the outer groove portion 10b and may interfere with each other. It should be noted that it is conceivable to increase the amount of protrusion of the retaining ring side O-ring 10 from the annular groove 11 to increase the follow-up deformation limit, but this is done by vibration or pressure fluctuation. There is a risk that the side O-ring 10 will jump out of the annular groove 11 and fall off, and it cannot be used at all due to the secondary sealing function between both rings 4 and 5.

However, such a problem is caused by devising the shape of the annular groove 11, particularly the shape of the inner diameter side wall surface 13 as in the above-described embodiment, so that the O-ring holding portion 5c is attached to the holding ring 5.
In combination with the formation of the above, it can be reliably solved.

That is, the retaining ring side retaining ring side O-ring 10
However, since the inner diameter side wall surface 13 of the annular groove 11 is supported in a non-contact state with the groove mouth side portion 13a, the portion corresponding to the groove mouth side portion 13a in the groove inner portion 10a as well as the groove outer portion 10b. (Hereafter, “apparent outside groove”)
Also, 10'b can be deformed in the inner diameter direction. That is, the first contact point C which is the contact point of the retaining ring side retaining ring side O-ring 10 on the back surface 4d of the stationary seal ring 4.
₁ is a holding ring side holding ring side O-ring 10 in the holding ring 5.
Of the outer circumferential surface of the annular groove 11, that is, the outer peripheral portion of the groove when a large relative displacement is made in the inner diameter direction with respect to the second contact point C ₂ which is the contact point of the retaining ring side O-ring 10 on the bottom wall surface 15 of the annular groove 11. 10b and the apparent outer groove portion 10'b connected thereto are deformed following the displacement of the first contact point C ₁ , and the following deformation limit of the retaining ring side retaining ring side O ring 10 is shown in FIG. It is significantly larger than in the case of the annular groove configuration shown in A) and (B). In other words, the inner diameter side wall surface 13 of the annular groove 11 is substantially constituted only by the groove inner portion 13b because of the support form of the inner diameter side wall surface 13 of the retaining ring side holding ring side O-ring 10, and thus the inner diameter side The deformable portions whose deformation is not substantially restricted by the wall surface 13 are the outer groove portion 10b protruding from the annular groove 11 and the apparent outer groove portion 10'b which is a part of the inner groove portion 10a connected to the outer groove portion 10b. Will be configured. Therefore, the deformable portions 10b and 10'b are larger than in the conventional seal, and the retaining ring side retaining ring side O-ring 10 is easily deformed in the inner diameter direction. Therefore, the first contact point C ₁ is largely displaced in the inner diameter direction relative to the second contact point C ₂ due to the distortion of both rings 4 and 5, and the relative displacement is absorbed depending on the deformation of the groove outer portion 10b. If you can't
As shown by the chain line, the deformable portions 10b and 10'b can easily elastically deform following the displacement of the first contact portion C ₁ , and as a result, the strain of both rings 4 and 5 can be deformed. The stationary seal ring 4 is not adversely affected by the distortion of the retaining ring 5 because they are not absorbed by the deformation of 10'a and 10b and do not interfere with each other.

On the other hand, the deformable portions 10b, 1
If 0'b is large, the relative displacement of the contact points C ₁ and C ₂ can be easily followed, but the deformable portions 10b and 10'b are deformed more than necessary in the inner diameter direction, which may cause an influence of vibration of the device. Together, there is a possibility that the retaining ring side retaining ring side O-ring 10 may jump out from the annular groove 11 in the inner diameter direction and fall off. However, the deformation or displacement of the deformable portions 10b and 10'b in the inner diameter direction is continued to the groove opening side portion 13a, and the stationary seal ring 4 is
Retaining ring side O-ring retaining portion 5 that protrudes into the annular recess 4c of
Since it is regulated within a certain range by c, there is no fear as described above. That is, the deformable portion 10b,
The adverse effect of increasing the size of 10'b is reliably eliminated by the holding ring side O-ring holding portion 5c. Moreover, the retaining ring side O-ring retaining portion 5c is formed in the groove opening side portion 13a.
Since the deformable portions 10b and 10'b are restricted in deformation and displacement in the inner diameter direction within the range corresponding to the groove opening of the annular groove 11, the deformable portions 10b and 10'b are connected to each other.
A part of 0'b (mainly the outer portion of the apparent groove) can be easily returned to the inside of the annular groove 11. Therefore, even when the stationary seal ring 4 and the retaining ring 5 relatively move due to the influence of strain, vibration, etc., the retaining ring side retaining ring side O-ring 10 can be appropriately deformed following this, and the retaining ring side retaining ring can be retained. The secondary sealing function of the ring-side O-ring 10 is excellently exhibited and maintained. In addition,
In the secondary sealing function, the stationary seal ring 4 and the retaining ring 5 are pressed in the approaching direction by appropriately setting the inner diameter d of the annular groove 11 within the above range (D + 0.5 mm ≦ d ≦ D + 4.0 mm). It goes without saying that by setting the above condition, it will be more effectively exhibited.

The non-contact mechanical seal according to the present invention is not limited to the above embodiment, and can be appropriately improved and changed without departing from the basic principle of the present invention. For example, as for the shape of the inner diameter side wall surface 13 of the annular groove 11 for more surely avoiding the strain interference between the stationary seal ring 4 and the retaining ring 5, the retaining ring side retaining ring side O ring 10 is not formed in the groove mouth side portion 13a. It is arbitrary as illustrated in FIG. 5 as long as it is supported in a contact state. That is, in the structure shown in FIG. 5 (A), the inner diameter side wall surface 13 is an arc surface that gradually reduces in diameter in the groove opening direction, and the retaining ring side retaining ring side O-ring 10 is not in contact with the groove opening side portion 13a. Side part 1
3b is supported. Further, in the case shown in FIG. 1B or 1C, the inner diameter side wall surface 13 has a stepped shape, and the holding ring side holding ring side O ring 10 is separated from the small diameter groove mouth side portion 13a, and the large diameter groove is formed. The rear side portion 13b is supported.

Further, as shown in FIG. 6, the seal case 1
By forming a cylindrical guide portion 1c extending from the retainer portion 1b to the inner peripheral portion of the stationary seal ring 4 through the retaining ring 5 and fitting the stationary seal ring 4 onto the guide portion 1c, The stationary seal ring 4 may be retained in the seal case 1 so as to be movable in the axial direction and not displaceable in the radial direction. Even in this case, the stationary seal ring 4 is fitted to the guide portion 1c with a dimensional tolerance (JIS-B0401) of a clearance fit, and the inner peripheral surface of the stationary seal ring 4 and the outer peripheral surface of the guide portion 1c are separated from each other. An extremely minute gap is formed between the stationary seal ring 4 and the radial displacement of the stationary seal ring 4, which allows movement of the stationary seal ring 4 in the axial direction and passage of fluid. This gap is appropriately set according to the diameter of the stationary seal ring 4, the sealing conditions, etc., as in the above embodiment.
Generally, it is preferable to set the difference between the inner diameter of the stationary seal ring 4 and the outer diameter of the guide portion 1c to about 10 to 100 μm. Of course, any means may be used to generate a dynamic pressure between the sealed end surfaces 3a and 4a. That is, the dynamic pressure generating groove 3
The shape of a and the sealing end faces 3a and 4a forming the same are arbitrary.

[0037]

As can be easily understood from the above description, the non-contact mechanical seal of the present invention has a configuration such as a form when the stationary seal ring and the retaining ring are assembled and a property change of the retaining ring side O-ring. Regardless of the sealing conditions, the sealing function of the sealing ring and the secondary sealing function of the O-ring on the retaining ring side can be excellently exerted and maintained, and the sealed fluid region and the non-sealed fluid region can be sealed for a long period of time. It can be done well.

[Brief description of drawings]

FIG. 1 is a half-section vertical side view showing an embodiment of a non-contact type mechanical seal according to the present invention.

FIG. 2 is a vertical cross-sectional side view showing an enlarged main part of FIG.

FIG. 3 is a vertical cross-sectional side view showing an enlarged main part of FIG.

FIG. 4 is a pressure distribution diagram acting on a stationary seal ring and a retaining ring.

FIG. 5 is a vertical sectional side view corresponding to FIG. 3 showing a modified example of the annular groove.

FIG. 6 is a vertical sectional side view corresponding to FIG. 1 showing another embodiment.

FIG. 7 is a vertical sectional side view corresponding to FIG. 1 showing a conventional seal.

8 is a vertical cross-sectional side view showing an enlarged main part of FIG.

[Explanation of symbols]

1 ... Seal case, 2 ... Rotating shaft, 3 ... Rotating sealing ring, 3
a, 4a ... Sealing end face, 3b ... Dynamic pressure generating groove, 4 ... Stationary sealing ring, 4c ... Annular recess, 4d ... Rear surface of stationary sealing ring, 5 ... Holding ring, 5b ... Pressing section, 5c ... O-ring holding section, 5d ... Front of pressing portion, 6 ... Spring, 10 ... Holding ring side O-ring, 11 ... Annular groove, 13 ... Inner diameter side wall surface, d ... Inner diameter of annular groove, D ... Outer diameter of held portion, H ... Sealed Fluid region, L ... Non-sealed fluid region.

Claims (1)

[Claims] 1. A rotary seal ring fixed to a rotary shaft, and a tubular portion to be held axially movable in a state of being secondarily sealed in a seal case via a case-side O-ring and its front end. A retaining ring having an annular pressing portion formed on the pressing portion, a stationary sealing ring that is biased to the rotary sealing ring via the retaining ring, and an annular groove formed on the front surface of the pressing portion. And a holding ring side O-ring that holds the front surface of the pressing portion and the back surface of the stationary sealing ring in a secondary sealed non-contact state, and opposes the rotary sealing ring and the stationary sealing ring. A non-contact structure configured to seal a sealed fluid region, which is an outer peripheral side region of the sealed end face, and a non-sealing fluid region, which is an inner peripheral side region, by relatively rotating the sealed end face that is the end face in a non-contact state. In the mechanical seal, An annular O-ring holding portion is formed so as to be loosely fitted into the annular concave portion formed in the inner peripheral portion of the stationary sealing ring and connected to the inner diameter side wall surface of the annular groove with a slight radial gap. The inner diameter d of the annular groove is D + 0.5 mm ≦ d ≦ D + 4.0 mm with respect to the outer diameter D of the held portion.
A non-contact type mechanical seal characterized by being configured as follows.