JPH08303605A - Non-contact type mechanical seal - Google Patents

Abstract

PURPOSE: To prevent strain interference between a static sealing ring and a holding ring, and also excellently maintain a secondary seal function by an O-ring between the static sealing ring and the holding ring. CONSTITUTION: An interval between the back surface 4d of a static sealing ring 4 and the front surface 5d of a holding ring 5 is held in a non-contact condition secondarily sealed by an O-ring 10 held in an annular groove 11. The diameter of a groove opening side part 13a on the inside diameter side wall surface 13 of the annular groove 11 is formed smaller than a groove end side part 13b, and the O-ring 10 is formed to be supported in such a condition that it is not be brought in contact with the groove end side part 13a on the inside diameter side wall surface 13. An annular O-ring holding part 5c which ranges to the groove opening side part 13a so as to be loosely fittingly plunged into the annular recessed part 4c of the static sealing ring 4, is projected on the front surface 5d of the holding ring 5.

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.
A rotary seal ring 3 fixed to a rotary shaft 2 penetrating through the ring, a holding ring 5 having an L-shaped cross section held by the seal case 1 via an O-ring 7 so as to be movable in the axial direction, the seal case 1 and the holding ring 5. And a stationary seal ring 4 which is urged by the spring 6 to the rotary seal ring 3 via the retaining ring 5 and a rectangular cross section formed on the front surface 5d of the retaining ring 5. An O-ring 10 which is engaged and held in an annular groove 11 having a shape or a dovetail shape and which secondarily seals between the back surface 4d of the stationary sealing ring 4 and the front surface 5d of the holding ring 5 is provided. , 4 between the sealed end surfaces 3a and 4a, which are the opposite end surfaces, are kept in a non-contact state with a fluid film interposed by generating a dynamic pressure by the dynamic pressure generating groove 3b provided in the rotary side sealed end surface 3a. Sealing end faces 3a, 4 in the fluid film forming portion
It is well known that the high pressure fluid region H, which is the outer peripheral region of a, and the low pressure fluid region L, which is the inner peripheral region thereof, are sealed (hereinafter referred to as "conventional seal").

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, when 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 the 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 strain state completely different from the strain of itself. Therefore, the smoothness of the stationary side sealing end surface 4a, the concentricity with respect to the rotating side sealing end surface 3a,
If the parallelism is impaired and the dynamic pressure generated between the sealing end faces 3a and 4a becomes non-uniform, or in an extreme case, an unexpected situation such as defective dynamic pressure generation or local contact between the sealing end faces 3a and 4a may occur. This causes a problem that a good sealing function cannot be exhibited for a long period of time. In particular, the problem is high pressure,
It occurs remarkably under high speed conditions, making it more difficult to use under such sealing conditions.

Therefore, in the conventional seal, as shown in FIGS. 7 and 8, the groove depth of the annular groove 11 is set to be smaller than the cross-sectional diameter of the O-ring 10 by a predetermined amount, and a part of the O-ring 10 is annular groove. By making the stationary seal ring 4 protrude from 11, the stationary seal ring 4 is held in a non-contact state where it is sealed between the rear surface 4d of the stationary seal ring 4 and the front surface 5d of the retaining ring 5 via the O-ring 10. It is designed so as not to be adversely affected by the distortion of No. 5. That is, since the stationary seal ring 4 and the holding ring 5 are only in indirect contact with each other via the O-ring 10, both rings 4, 5 are subject to pressure fluctuations, temperature changes, etc.
Even when different strains occur, the strains are absorbed by the elastic deformation of the O-ring 10 and do not interfere with each other, and the stationary seal ring 4 is not adversely affected by the strain of the retaining ring 5. The O-ring 10 is generally made of rubber or the like having incompressibility and high friction, and even when the rings 4 and 5 are relatively displaced in the axial direction without being displaced in the radial direction. As shown in FIG. 8, the inner diameter of the annular groove 11 with the outer diameter side wall surface 14 of the annular groove 11 has an appropriate allowance so that the secondary seal can be satisfactorily secondary-sealed by the following deformation. It is supported by the side wall surface 13.

[0006]

However, in the conventional seal, as shown in FIG. 8, the annular groove 11 has a rectangular cross section (FIG. (A)) or a dovetail groove shape (FIG. (B)). Therefore, the strain of both rings 4 and 5 may not be absorbed by the elastic deformation of the O-ring 10, and the mutual interference of these strains cannot be completely eliminated.

That is, the contact point C ₁ of the O-ring 10 on the back surface 4d of the stationary seal ring 4 (hereinafter referred to as the "first contact point") and the contact point of the O-ring 10 on the retaining ring 5, that is, the bottom wall surface 15 of the annular groove 11. The contact point of the O-ring 10 (hereinafter referred to as “second contact point”) C ₂ in FIG. Relative displacement will occur. On the other hand, the O-ring 10 is made of a material having a high friction coefficient such as rubber and the rear surface 4 of the stationary seal ring 4 is made.
Since it is pinched between d and the bottom wall surface 15 of the annular groove 11, slippage is unlikely to occur at both contact points C ₁ and C ₂ , and deformation occurs due to relative displacement of the contact points C ₁ and C _2. Will be done. Therefore, when the first contact point C ₁ is displaced relative to the second contact point C ₂ in the inner diameter direction, the O-ring portion that is in contact with the first contact point C ₁ along with the displacement of the first contact point C ₁ moves in the inner diameter direction. Tries to elastically deform, but the annular groove 1
O-ring part in 1 (hereinafter referred to as "groove part") 10a
Since the deformation of the O-ring 10 in the inner diameter direction is prevented by the inner diameter side wall surface 13 of the annular groove 11, the deformation of the O-ring 10 also contributes to the fact that it is made of an incompressible material such as rubber. Therefore, the O-ring portion (hereinafter referred to as “outer groove portion”) 10b slightly protruding from the annular groove 11 is only allowed within a range in which it can be elastically deformed (see the chain line in FIG. 8).

However, since the outer groove portion 10b is extremely small, the range in which the O-ring 10 can deform following the displacement of the first contact point 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 is O
There is a case where the follow-up deformation limit of 0 is exceeded, and in such a case, the strains of both rings 4 and 5 are not absorbed by the deformation of the groove outer portion 10b, and there is a risk of mutual interference. It should be noted that it is possible to increase the amount of protrusion of the O-ring 10 from the annular groove 11 to increase the follow-up deformation limit.
May jump out of the annular groove 11 and fall off, and cannot be used at all due to the secondary sealing function between the rings 4 and 5.

The present invention solves the above-mentioned problems in the conventional seal to surely prevent mutual strain interference between the stationary seal ring and the retaining ring, and to prevent the O between the stationary seal ring and the retaining ring. An object of the present invention is to provide a non-contact type mechanical seal that can maintain a good secondary sealing function of a ring and can exhibit a good sealing function of both sealing rings for a long period of time regardless of sealing conditions. Is.

[0010]

SUMMARY OF THE INVENTION The present invention comprises a rotary seal ring fixed to a rotary shaft and a stationary seal ring held in a seal case in a state of being biased to the rotary seal ring via a retaining ring. A dynamic pressure generating groove is formed on one of the sealing end surfaces, which are the opposite end surfaces of, and between the back surface of the stationary sealing ring and the front surface of the retaining ring,
In order to achieve the above object, in a non-contact type mechanical seal configured to hold in a non-contact state secondary-sealed by an O-ring held in an annular groove formed in the front surface of the holding ring, in particular, The groove side portion of the inner diameter side wall surface of the annular groove has a diameter smaller than that of the groove inner side portion, and the O ring is supported in the inner diameter side wall surface in a non-contact state with the groove side portion and the front surface of the retaining ring. In addition, it is proposed that an annular O-ring holding portion, which is connected to the groove opening side portion and is inserted into the inner peripheral side space of the stationary sealing ring in a loose fitting manner, is provided in advance.

[0011]

The O-ring is formed on the inner diameter side wall surface of the annular groove,
Since it is supported in a non-contact state with the groove mouth side portion, not only the outer groove portion but also the portion corresponding to the groove mouth side portion of the inner groove portion (hereinafter referred to as “apparent outer groove portion”) Deformation is possible. That is, the inner diameter side wall surface of the annular groove is substantially constituted only by the groove inner side portion in terms of the support form by the inner diameter side wall surface of the O-ring, and the deformation is substantially not restricted by the inner diameter side wall surface. The portion is constituted by an outer groove portion protruding from the annular groove and an apparent outer groove portion continuous with the outer groove portion. Therefore, due to the distortion of the stationary seal ring and the retaining ring, the first contact point may become the second contact point.
The deformable part follows the displacement of the first contact point even when the relative displacement in the inner diameter direction is large relative to the contact point, that is, when the relative displacement that cannot be absorbed only by the deformation of the outside of the groove occurs. The elastic deformation of the stationary seal ring and the retaining ring is not absorbed by the deformation of the deformable portion and does not interfere with each other, and the stationary seal ring is not adversely affected by the distortion of the retaining ring. Never receive.

On the other hand, if the deformable portion is large, it is possible to easily follow the relative displacement of the contact portion, but on the other hand, the deformable portion is deformed more than necessary in the inner diameter direction, which is affected by the vibration of the device. There is a risk that the O-ring will pop out from the annular groove in the inner diameter direction and fall off. However, since the deformation or displacement of the deformable portion in the inner diameter direction is restricted within a certain range by the O-ring holding portion extending from the front surface of the holding ring to the inner peripheral side space portion of the stationary sealing ring, the above description is given. There is no such fear. Moreover, since the O-ring holding portion is connected to the groove opening side portion, the deformation or displacement of the deformable portion in the inner diameter direction is restricted within the range corresponding to the groove opening of the annular groove, so that part of the deformable portion is It is easy to return the (mainly the outer portion of the apparent groove) to the inside of the annular groove, and the O-ring works well even when the stationary seal ring and the retaining ring move relative to each other due to the influence of strain or vibration. Following deformation is possible, and the secondary sealing function of the O-ring is satisfactorily exhibited and maintained.

[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 high pressure fluid region. A dynamic pressure generating groove 3b having an appropriate shape such as a spiral shape opening to the outer peripheral portion facing 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 high-pressure fluid region (for example, a high-pressure gas region in a machine such as a turbine) H that is an outer peripheral region of the sealed end faces 3a and 4a and a low-pressure fluid that is an inner peripheral region thereof. A region (for example, an atmospheric region outside the machine such as a turbine) L is sealed.

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 fitted and held in the inner peripheral portion of the retainer portion 1b of the seal case 1 via a rubber 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.

As shown in FIGS. 1 to 3, an O-ring 10 is interposed between the stationary seal ring 4 and the retaining ring 5 between the opposed end surfaces 4d and 5d of the rings 4 and 5 in the axial direction. By doing so, the secondary seal is held in a non-contact state.

That is, the front surface of the holding ring 5, that is, the pressing portion 5
A concentric annular groove 11 is formed in the front surface 5d of b, and the static sealing ring 4 is biased by the spring 6 by fitting and holding the rubber O-ring 10 in the annular groove 11 while slightly protruding. In combination with the operation, in a sealed state having an appropriate clearance 12 between the holding ring 5 and the holding ring 5, the rotary sealing ring 3 is urged and held so as to be pressed. In addition, O
The ring 10 is held in a non-contact state with the outer diameter side wall surface 14 of the annular groove 11.

Thus, the annular groove 11 is, as shown in FIG.
The groove mouth side portion 13a of the inner diameter side wall surface 13 has a smaller diameter than the groove inner side portion 13b so that the O ring 10 is supported on the inner diameter side wall surface 13 in a non-contact state with the groove mouth side portion 13a. That is, in this embodiment, as shown in FIG. 3, the inner diameter side wall surface 13 of the annular groove 11 is an inclined surface that gradually reduces its diameter in the groove mouth direction, and the groove inner portion 10a is separated from the groove mouth side portion 13a. In this state, the groove back side portion 13b is configured to be supported. As shown in FIGS. 2 and 3, the front surface 5d of the pressing portion 5b is a circle that is continuous with the groove opening side portion 13a and is loosely fitted into the inner peripheral space of the stationary sealing ring 4, that is, the annular recess 4c. An annular O-ring holding portion 5c is provided so as to project. The gap S between the annular recess 4c and the O-ring holder 5c is
Both parts 4c and 5c are set as small as possible within a range in which they do not interfere with each other due to the strain of both rings 4 and 5. Specifically, when both parts 4c and 5c are in the concentric state, S = 0.3
It is preferable to set it to ˜0.5 mm.

By the way, in front of the stationary seal ring 4 and the retaining ring 5,
The front surface and the back surface have dynamic pressure due to the fluid in the high-pressure fluid region H and
Due to static pressure, pressing force F in the axial direction as shown in Fig. 4₁, F
´₁, F₂, F '₂, F₃, F_FourWill work
It That is, the front surface of the stationary seal ring 4 has a sealing end surface 3
Pressing force F due to dynamic pressure generated between a and 4a₁And annular convex
The pressing force F ′ due to the fluid pressure received by the portion 4b₁Acts,
The back surface of the annular protrusion 4b is pressed by the fluid pressure.
Pressure F '₂And pressure of fluid that has entered clearance 12
Pressing force due to₂Works. Here, the stationary seal ring 4
Pressing force F ′ acting on the annular convex portion 4b₁, F '₂Is the direction
On the contrary, they are the same size, and they are offset.
Therefore, the static sealing ring 4 has a pressing force F₁, F₂Only
It can be considered to work. On the other hand, the front side of the retaining ring 5
Pressing force F due to the pressure of the fluid that has entered Alance 12₃But
Fluid acting on the back surface of the pressing portion 5b
Pressing force due to pressure F_FourWorks. Therefore, the pressing force F₁
Is depending on the usage conditions of the mechanical seal.
It is inevitably determined and the pressing force F_Fourabout
The diameter of the secondary seal part by the O-ring 7, that is, the held part
The outer diameter of 5a (hereinafter referred to as "balance diameter") D
The pressing force F₂, F ₃Is O
The diameter of the secondary seal portion formed by the ring 10 (hereinafter referred to as "seal
To some extent freely by d)
it can. That is, the seal diameter d and the back surface 4 of the stationary seal ring 4
d and the pressure receiving area on the front surface 5d of the retaining ring 5 are inversely proportional to
However, if the seal diameter d is increased, the pressing force F₂, F₃Is small
And the pressing force F becomes smaller as the seal diameter d becomes smaller.₂, F₃Is
growing. Therefore, in this embodiment, the seal diameter d is
Larger than lance diameter D, F₁> F₂And F₃<F_Four
By setting so that
Make sure that the secondary sealing function is always excellent
is there. That is, F₁> F₂And F₃<F_FourSo that
The stationary seal ring 4 and the retaining ring 5 in the approaching direction.
The O-ring 10 is pressed, regardless of vibration and the like.
Is held in a state of being pinched between both rings 4 and 5,
The secondary sealing function of the plug 10 does not deteriorate. However
However, if the seal diameter d is not larger than a certain value, specifically d
If -D <0.5 mm, the above effect can be expected so much.
Absent. On the contrary, if the seal diameter d becomes larger than necessary,
Physically, if d-D> 4.0 mm, the static sealing ring 4
Pressing force F that acts₁And pressing force F₂Out of balance with
The pressing force difference (F₁-F₂)
The torsional strain of the stationary seal ring 4 increases,
There is a risk of local contact between the surfaces 3a and 4a. But
Therefore, the seal diameter d is 0.
Depending on sealing conditions, etc., within the range of 5 mm ≤ d-D ≤ 4.0 mm.
It is preferable to set it appropriately. By the way
The diameter d is actually the static seal ring in the O-ring 10.
4 or contact point C with retaining ring 5₁, C₂Is the diameter at
However, such contact point C₁, C₂Is the property of O-ring components
Varies depending on (rubber hardness, rubber deterioration, etc.) and sealing conditions
Because it is easy to identify and difficult to identify,
With reference to the inner and outer diameters of the annular groove 11 (see, for example, FIG.
4, the seal diameter d is based on the inner diameter of the annular groove 11.
It is preferable to design. In addition, the actual sea
The fluctuation range of the radius d is determined by the displacement of the O-ring 10 in the inner diameter direction,
Deformation is restricted by the O-ring holding part 5c.
Therefore, even under the worst conditions, the inner and outer diameters of the annular groove 11
It does not become larger than the range, and normally the annular groove 11
Narrower than the range of inner and outer diameters.

In the non-contact type mechanical seal constructed as described above, the O-ring 10 is supported on the inner diameter side wall surface 13 of the annular groove 11 in a non-contact state with the groove opening side portion 13a. Therefore, not only the outer groove portion 10b, but also the portion of the inner groove portion 10a corresponding to the groove mouth side portion 13a, that is, the apparent outer groove portion 10'b can be deformed in the inner diameter direction. That is, the back surface 4 of the stationary seal ring 4
The first contact point C ₁ which is the contact point of the O ring 10 in d is the second contact point C which is the contact point of the O ring 10 in the retaining ring 5, that is, the contact point of the O ring 10 in the bottom wall surface 15 of the annular groove 11. _{On the} other hand, in the case of a large relative displacement in the inner diameter direction, the outer groove portion 10b and the apparent outer groove portion 10'b connected thereto are deformed following the displacement of the first contact point C _1. Become, O ring 1
The following deformation limit of 0 is significantly larger than that in the case of the annular groove configuration shown in FIGS. 8A and 8B (see the chain line in FIG. 3). In other words, the inner diameter side wall surface 13 of the O-ring 10
In view of the support form by the above, the inner diameter side wall surface 13 of the annular groove 11 is substantially constituted only by the groove inner portion 13b, and the deformable portion whose deformation is not substantially restricted by the inner diameter side wall surface 13 is the annular groove. The groove outer portion 10b protruding from 11 and the apparent groove outer portion 10'b which is a part of the groove inner portion 10a connected to the groove outer portion 10b. Therefore, the deformable portions 10b and 10'b are larger than in the conventional seal, and the 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. Even if it is not possible, as shown by the chain line in FIG. 3, the deformable portions 10b and 10'b can easily elastically deform following the displacement of the first contact point C ₁ , resulting in both rings. The strains 4 and 5 are not absorbed by the deformation of the deformable portions 10 ′ a and 10 b and do not interfere with each other, and the static sealing ring 4 is not adversely affected by the strain of the retaining ring 5.

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 risk that the O-ring 10 may pop out from the annular groove 11 in the inner diameter direction and fall off. However, the deformation and displacement of the deformable portions 10b and 10'b in the inner diameter direction are kept within a certain range by the O-ring holding portion 5c which is continuous with the groove side portion 13a and protrudes into the annular recess 4c of the stationary seal ring 4. Since it is regulated, there is no fear as described above. That is, the adverse effect caused by enlarging the deformable portions 10b and 10'b is reliably eliminated by the O-ring holding portion 5c. Moreover, since the O-ring holding portion 5c is connected to the groove opening side portion 13a, the deformable portion 10b,
Since the deformation or displacement of 10'b in the inner diameter direction is restricted within the range corresponding to the groove opening of the annular groove 11, a part of the deformable portions 10b, 10'b (mainly the apparent outer groove portion) is formed. The return to the inside of the annular groove 11 becomes easy. Therefore, even when the stationary seal ring 4 and the retaining ring 5 move relative to each other due to the influence of strain or vibration, the O-ring 10 can be appropriately deformed following this, and the secondary sealing function of the O-ring 10 is good. Is demonstrated and maintained. The secondary sealing function is set so that the seal diameter d is appropriately set within the above range with the balance diameter D as a reference so that the stationary seal ring 4 and the retaining ring 5 are pressed in the approaching direction. By
It will be even better.

By the way, since the holding ring 5 is held by the seal case 1 via the O-ring 7 which is an elastic member, there is a possibility that the holding ring 5 may be eccentric due to vibration of the device.
If the holding ring 5 is eccentric relative to the stationary seal ring 4 by a certain amount or more, the clamping state in the circumferential direction of the O-ring 10 becomes extremely uneven, and the secondary sealing function of the O-ring 10 may deteriorate. There is. However, the O-ring holding portion 5c projecting from the holding ring 5 is inserted into the annular recess 4c of the stationary sealing ring 4 with a slight clearance S, and the O-ring holding portion 5c is relatively opposed to the stationary sealing ring 4 and the holding ring 5. Since the amount of eccentricity is regulated within a certain range, the pinching state of the O-ring 10 in the circumferential direction does not become significantly uneven.

From these facts, in the non-contact mechanical seal according to the present invention, the smoothness of the stationary side sealing end surface 4a and the concentricity with respect to the rotating side sealing end surface 3a are affected by the distortion of the retaining ring 5. ， Without loss of parallelism, even under high pressure and high speed sealing conditions,
The sealing function of the sealed end faces 3a and 4a can be exhibited well.

The non-contact mechanical seal according to the present invention is not limited to the above-mentioned embodiment, and can be appropriately improved and changed without departing from the basic principle of the present invention. That is, the inner diameter side wall surface 1 of the annular groove 11
The O-ring 10 may have any shape as long as it supports the O-ring 10 in a state in which the O-ring 10 does not contact the groove opening side portion 13a, and the shape is arbitrary, and may be, for example, the shape shown in FIG. That is, in the structure shown in FIG. 5A, the O-ring 10 is supported by the groove inner side portion 13b in a non-contact state with the groove mouth side portion 13a by using the inner diameter side wall surface 13 as an arc surface that gradually reduces in diameter in the groove mouth direction. Is done. In addition, the same figure (B)
Alternatively, in the structure shown in (C), the inner diameter side wall surface 13 has a stepped shape, and the O-ring 10 is supported by the large-diameter groove inner side portion 13b in a state of being separated from the small-diameter groove mouth side portion 13a.

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, the means for generating the dynamic pressure between the sealed end faces 3a, 4a is also optional. That is, the dynamic pressure generating groove 3a
The shape and the sealing end surfaces 3a and 4a forming the same can be selected arbitrarily.

[0031]

As can be easily understood from the above description, in the non-contact mechanical seal of the present invention, the shape of the inner diameter side wall surface of the annular groove is devised so that the stationary seal ring and the retaining ring are Since the O-ring that secondarily seals the space between the two is made easier to deform in the inner diameter direction, mutual interference of strain between the stationary seal ring and the retaining ring is reliably prevented, and the stationary seal ring is retained by the retaining ring. It is not affected by the distortion. Moreover, since the deformation and displacement of the O-ring in the inner diameter direction are restricted within a certain range by the O-ring holding portion, the O-ring is reliably prevented from jumping out and falling out of the annular groove.
The secondary sealing function of the O-ring is exhibited well. Therefore, according to the present invention, there is provided a non-contact mechanical seal capable of always exhibiting a good sealing function by both sealing rings regardless of sealing conditions without complicating and increasing the size of the structure. can do.

[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 (inner peripheral side space portion), 4d ... Back surface of stationary sealing ring, 5 ... Holding ring, 5b ... Pressing section, 5c ... O-ring holding portion, 5d ... Front surface of pressing portion (front surface of holding ring), 6 ... Spring, 10 ... O ring, 11 ... Annular groove, 13 ... Inner diameter side wall surface, 13a ... Groove mouth side portion, 13b ... Groove depth Side part.

Claims (1)

[Claims] 1. One of sealing end faces, which is an end face opposed to a rotary seal ring fixed to a rotary shaft and a stationary seal ring held by a seal case in a state of being pressed and pressed to the rotary seal ring through a holding ring. A dynamic pressure generating groove is formed in the ring, and an O-ring held between the back surface of the stationary seal ring and the front surface of the retaining ring in an annular groove formed in the front surface of the retaining ring is a secondary sealed non-contact state. In the non-contact mechanical seal configured to hold the groove, the groove side portion of the inner diameter side wall surface of the annular groove has a smaller diameter than the groove back side portion, and the O-ring does not contact the groove side portion on the inner diameter side wall surface. In addition to being configured to be supported in a state, a ring-shaped O-ring holding portion is provided on the front surface of the holding ring, the ring-shaped O-ring holding portion being connected to the groove opening side portion and protruding into the inner peripheral side space of the stationary sealing ring in a loose fit manner. Non-contact type mechanism characterized by being Nical seal.