JPH10231938A - Non-contact type mechanical seal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact type mechanical seal which can exert good sealing function specified by the design in accordance with the given conditions including the seal structure and which can be easily designed and fabricated. SOLUTION: The second seal ring 24 is formed from a seal ring body 241 made of carbon and a silicon carbide film 242 formed as covering part of the body 241. The surface of the film 242 is formed in the second sealing end face 24a to constitute a ring-shaped plane parallel with the first sealing end face 22a on low pressure conditions where no pressure strain is generated (see Fig. A). The thickness T of the silicon carbide film 242 is set so that the second sealing end face 24a is elastically deformed to a ring-shaped taper surface capable of forming a ring-shaped space 27 having a wedge-shaped section gradually narrowing in the non-seal fluid region A2 in the area to the first sealing end face 22a because of the interference of the elastic strain in the silicon carbide film 242 with the pressure strain in the ring body 241 on high pressure conditions where pressure strain is generated (see Fig. B).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a high-pressure seal in which a first seal ring and a second seal ring made of carbon softer than its constituent material are subjected to pressure-strain within an elastic limit by a fluid to be sealed in the second seal ring. By being relatively rotated under the conditions, it is configured to seal the sealed fluid region and the non-sealed fluid region, which are the inner and outer peripheral regions, between the first and second sealed end surfaces, which are the opposed end surfaces of the two sealed rings. And a non-contact type mechanical seal.

[0002]

2. Description of the Related Art Non-contact type mechanical seals of this kind are:
Generally, a dynamic pressure type seal configured to hold both sealing end faces in a non-contact state by dynamic pressure acting therebetween and a structure configured to hold both sealing end faces in a non-contact state by static pressure acting therebetween. Static pressure seals. Generally, a dynamic pressure type seal is used for a rotary device such as a turbine, a blower, and a centrifugal compressor which handles high pressure gas, and a static pressure type seal is used for a rotary device such as a pump which handles a high pressure liquid.

As shown in FIG. 8, for example, a conventional dynamic pressure type seal m ₁ includes a first sealing ring 12 fixed to a rotating shaft 11, a holding ring 15 and an O-ring 1
6, a second sealing ring 14 made of carbon and held slidably in the axial direction through the inner ring 6 and a spring 17 for urging the second sealing ring 14 toward the first sealing ring 12. The first and second sealed end faces 12a and 14a, which are the opposite end faces of the sealing rings 12 and 14, are kept in a non-contact state by generating dynamic pressure therebetween, and the outer peripheral side between the two sealed end faces 12a and 14a. It is configured to seal the unsealed fluid region a _2, which is the inner peripheral side region and the sealed fluid region a ₁ in the region. The first seal end faces 12a serving seal end face of the first seal ring 12, have dynamic pressure generation grooves 12b open to the sealed fluid region A ₁ is formed, the seal end faces 12a by the relative rotation of the seal ring 12, 14, A dynamic pressure is generated in the sealed fluid 14a. Both sealing end faces 12a,
As shown in FIG. 9 (A), the dynamic pressure generated during this time is balanced with the back pressure of the fluid to be sealed acting on the second sealing ring 14 and the urging force of the spring 17 so as to reduce the minute interval. It is kept in a separated non-contact state.

A conventional static pressure type seal m ₂ is a so-called tapered face seal, for example, as shown in FIG. 10, a first sealing ring 22 fixed to a rotating shaft 21,
A second sealing ring 24 made of carbon held in the sealing case 23 via an O-ring 25 so as to be slidable in the axial direction;
A spring 26 for urging the sealing ring 24 against the first sealing ring 22; and a spring 26 between the first and second sealing end faces 22a, 24a which are opposite end faces of the sealing rings 22, 24. It is configured to seal the unsealed fluid region a _2, which is the inner peripheral side region and the sealed fluid region a ₁ in the region. First sealing end face 22 which is a sealing end face of first sealing ring 22
a, like the first sealing end face 12a of the dynamic pressure type seal m _1, although there is a circular plane orthogonal to the axis, the second
Sealing end surface 24a is an inner circumferential direction (non-sealed fluid region A ₂ direction) gradually narrowed annular tapered surface capable of forming an annular space 27 of the wedge-shaped cross section (convex truncated cone between the first sealing end face 22a Surface). In the following description, the sealed fluid pressure P of the sealed fluid region A ₁ is assumed to be based on the unsealed fluid pressure of the non-sealed fluid region A _2. In each of the seals m ₁ and m ₂ , the non-sealed fluid region A ₂ is often the atmospheric region. In such a case, the sealed fluid pressure P means a gauge pressure based on the atmospheric pressure. .

[0005] Such a static pressure type seal taper face plate
M_TwoIs closed between the sealed end faces 22a and 24a.
Sealed fluid leakage direction (non-sealed fluid area A_TwoDirection)
Since an annular space 27 having a wedge-shaped cross section is formed,
A second seal movable axially by the sealing fluid pressure P
The ring 24 has a closing force F having a pressure distribution as shown in FIG._CWhen
Opening force F_OActs to create a gap between the sealing end faces 22a, 24a.
An interval S is formed. And this gap S is the closing force F_CWhen
Opening force F_OAnd stable in a balanced state
Clearance (hereinafter referred to as “equilibrium clearance S₀"). This
Here, the closing force F_CBy the back pressure acting on the second seal ring 24.
(More precisely, back pressure and sp
(By the biasing force of the ring 26),
Opening force F_OIs the pressure (static) of the sealed fluid that has entered the annular space 7.
Pressure). By the way, the closing force F_CIs
Because it is due to back pressure (and spring 26)
As shown by a chain line in FIG. 12, the sealed fluid pressure P does not fluctuate.
As long as the opening force F _OActs on the annular space 27
Since this is due to the static pressure, as shown by the broken line in FIG.
It changes in inverse proportion by the change of the interval S. In other words, the opening force
F_ODecreases as the gap S increases and decreases
According to the above. Therefore, the gap S is flat.
Equilibrium gap S₀When it becomes larger, the opening force F_OIs the closing force F_CThan
It becomes smaller and the space between the sealing end faces 22a and 24a is closed,
Gap S is equilibrium gap S₀When it becomes smaller, the opening force F_OBut
Closing force F_CAnd between the sealed end faces 22a, 24a
When opened, the gap S is in any case a closing force F_CAnd opening force F
_OAnd balanced gap S₀Returned to and retained
Will be.

[0006]

However, in the above-mentioned conventional non-contact type mechanical seals m ₁ and m ₂ , in each case, the second sealing rings 14 and 24 made of carbon are used.
As the second sealing end faces 14a, 24a are elastically deformed by the pressure strain generated in the above, there is a problem that a good sealing function cannot be expected under high pressure conditions.

That is, in the static pressure type seal m ₁ ,
Since the two sealing end faces 12a and 14a are held in a non-contact state with a fluid film interposed therebetween by the dynamic pressure generated therebetween, in order to exhibit a good sealing function, FIG.
As shown in (A), it is necessary to keep the two sealed end faces 12a, 14a in a parallel state. However, since the second sealing ring 14 is made of carbon that is softer than the first sealing ring 12, under the high pressure condition, pressure distortion (elastic distortion) occurs in the second sealing ring 14 due to the fluid to be sealed. As shown in FIG. 9B, the two sealed end faces 14a
There is a possibility that the space between the members a and 14a may be elastically deformed such that the space gradually increases in the inner circumferential direction (hereinafter, referred to as an “outer height state”).

By the way, the dynamic pressure generating groove 12b is
Opened on the outer peripheral side (sealed fluid area A ₁ ) of the sealing end faces 12a, 14a by the relative rotation of the sealing end faces 12a, 14a.
a, and is pumped toward the inner peripheral side (non-sealed fluid area A ₂ ).
When the sealing end face 12a is distorted and the parallelism of the two sealing end faces 12a, 14a is impaired, compared with the case where the two sealing end faces 12a, 14a are in a parallel state, the two sealing end faces 12a, 14a.
The dynamic pressure changes so as to be smaller on the outer peripheral side and larger on the inner peripheral side. As a result, the second sealed end face 1
A moment acts on 2a in a direction in which the distance from the first sealed end surface 14a is reduced on the outer peripheral side.

Therefore, as shown in FIG. 9C, the second sealed end faces 12a are supposed to be both sealed end faces 12a, 14a.
Is distorted into a state in which the distance gradually increases in the outer circumferential direction (hereinafter referred to as “inner height state”), the inner moment state is automatically restored to the parallel state by the action of the above moment. However, when the second sealed end face 14a is distorted to the outer height state, the above-mentioned moment acts to increase the distortion of the second sealed end face 14a. That is,
Due to this moment, the distance between the two sealed end faces 12a and 14a is further enlarged on the inner peripheral side, and the two sealed end faces 12a and 14a are brought into contact on the outer peripheral side. As a result, the sealing function is significantly reduced, and the sealing end faces 12a and 14a may be brought into contact with each other on the outer peripheral side, and the sealing function may be stopped.

On the other hand, also in the tapered face seal m ₂ , under high pressure conditions, pressure distortion (elastic strain) is generated in the second sealing ring 24 made of carbon, and the second sealing end face 24 a has its tapered amount (sealing end face). There is a possibility that elastic deformation may occur in a direction to decrease the axial distance (Δ between the inner and outer ends at 24a), and in an extreme case, the annular space 7 having a wedge-shaped cross section may be lost. This dynamic in pressure type seal m ₁ but the second seal end face 14a is the same as the phenomenon that elastically deformed to the outside high state, when it comes to such a state, the opening force F sufficient to be balanced in closing force F _{C O} can no longer be secured and the sealed end face 2
a, ensure a predetermined equilibrium gap S ₀ between 4a, it can not be maintained, the sealing function is lowered significantly.

The present invention has been made in view of the above points, and maintains the second sealed end face in an appropriate state even under a high pressure condition in which a pressure distortion occurs in the second sealing ring made of carbon material. It is an object of the present invention to provide a non-contact type mechanical seal capable of exhibiting a good sealing function.

[0012]

SUMMARY OF THE INVENTION According to the present invention, a first sealing ring and a second sealing ring made of a carbon material softer than a constituent material thereof are provided on a second sealing ring by a fluid to be sealed. Are relatively rotated under the high pressure condition where the sealing ring is formed, thereby sealing the sealed fluid region and the non-sealed fluid region which are the inner and outer peripheral regions between the first and second sealed end surfaces which are the opposed end surfaces of the two sealing rings. In the non-contact type mechanical seal configured as described above, it is proposed to configure as follows in order to achieve the above object.

That is, in the non-contact type mechanical seal (hereinafter referred to as "first seal") according to the present invention, the second sealing ring is formed of a carbon sealing ring main body and a part thereof. A silicon carbide film coated and formed, and the film surface is formed as a second sealed end face forming an annular plane parallel to the first sealed end face under the low pressure condition where the pressure distortion does not occur. Under the high pressure condition, the thickness of the second sealing end face is maintained under the low pressure condition so that the silicon carbide film generates an elastic strain that balances the pressure strain generated in the sealing ring body. Propose to set. With such a configuration, the second sealing end face can be maintained in an appropriate state parallel to the first sealing end face even under a high-pressure condition in which pressure distortion occurs in the second sealing ring, and a good sealing function can be achieved. Can be demonstrated.

In the non-contact type mechanical seal (hereinafter referred to as "second seal") according to the present invention, the second sealing ring is particularly formed of a carbon sealing ring main body and a part thereof. And a silicon carbide film formed by coating.
The film surface is configured as a second sealing end face that forms an annular plane parallel to the first sealing end face under the low pressure condition in which the pressure distortion does not occur, and the film thickness is adjusted under the high pressure condition. Annular taper which can form a wedge-shaped annular space in which the second sealed end face gradually narrows in the direction of the non-sealed fluid region between the first sealed end face and the second sealed end face due to the interference between the elastic strain generated in the sealing ring body and the pressure strain generated in the sealing ring main body. It is proposed that the surface be elastically deformed. With such a configuration, the second sealing end face can be maintained at an appropriate annular tapered surface under a high-pressure condition in which pressure distortion occurs in the second sealing ring, and a good taper face sealing function can be exhibited. Can be.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the first and second seals will be specifically described below with reference to FIGS.

That is, FIGS. 1 to 4 show an embodiment of the first seal. As shown in FIG. 1, a first seal M ₁ in this embodiment includes a first seal ring 12 fixed to a rotating shaft 11 such as a turbine shaft, and a seal case 1.
3 includes a second sealing ring 14 slidably held in the axial direction via a holding ring 15 and an O-ring 16, and a spring 17 for urging the second sealing ring 14 against the first sealing ring 12. And the first sealing ring 12,
And the second sealed end faces 12a and 14a are held in a non-contact state by generating a dynamic pressure therebetween, so that the sealed end faces 12a and 14a
a, a sealed fluid region (for example, a high-pressure gas region in a machine such as a turbine) A ₁ which is an outer peripheral side region between a and a.
And a non-sealed fluid region (for example, an atmospheric region outside the machine such as a turbine) L which is an inner peripheral region. This first seal M ₁ is used for the second seal M ₁ described below.
Except for the configuration of the seal ring 14, since it is intended to form a known dynamic pressure type seal m ₁ the same structure shown in FIG. 8, by subjecting the same reference member, its details are omitted. The first sealing ring 12 has a first sealing end face 12a, which is a sealing end face, formed as an annular plane perpendicular to the axis, and is made of a super-hard material such as WC or SiC. The first sealed end face 12a is not deformed by pressure strain even under a high-pressure condition that causes strain. Further, the first seal end faces 12a, dynamic pressure generating grooves of the appropriate shape opened to the sealed fluid region A ₁ 12
b is formed, and a dynamic pressure is generated between the sealed end faces 12a and 14a by the sealed fluid as the rotating shaft 11 rotates.

[0017] In Thus, in this first seal M _1,
According to the present invention, the second sealing ring 14 is configured as follows.

That is, as shown in FIGS. 1 and 2A, the second sealing ring 14 has a sealing ring main body 141 made of carbon softer than the constituent material of the first sealing ring 2, and a nose part thereof. The silicon carbide film 142 is formed to cover the portion 141a. The sealing ring main body 141 has a convex shape in cross section in which an end portion is formed into an annular nose portion 141a obtained by cutting out the inner and outer peripheral portions thereof. The silicon carbide film 142 has a uniform thickness formed by coating the tip surface of the nose portion 141a by a conventional method, and its film surface is formed on the second sealing end surface 14a forming an annular plane parallel to the first sealing end surface 12a. It is composed. In other words, the second sealed end surface 14a has a smooth surface perpendicular to the axis under low pressure conditions (for example, in an initial operation state) in which no pressure distortion due to the sealed fluid is generated or hardly generated in the sealing ring main body 141 made of carbon. As a matter of fact, it is mirror-finished.

The thickness T of the silicon carbide film 142 (the thickness after the surface is mirror-finished to a sealed end face) T is a high pressure at which pressure distortion within the elastic limit due to the sealed fluid is generated in the sealing ring body 141 made of carbon. under conditions (a state in which the first seal M ₁ is the normal operation), the second seal end surface 14a to maintain the shape of the low pressure conditions described above, the silicon carbide film 142 in the seal ring body 141 It is set so as to generate an elastic strain that balances the generated pressure strain.

That is, by the operation of the first seal M ₁ ,
If the sealed fluid region A ₁ is boosted to a pressure that results in a pressure strain (elastic strain) to seal the ring body 141 made of carbon, silicon carbide film 142 is also naturally produce elastic strain, silicon carbide film 142 Since there is a clear difference in the rigidity between the sealing ring 141 and the sealing ring body 141, the distortion forms of the two 141 and 142 are greatly different. Since the two members 141 and 142 form an integral structure, their distortions interfere with each other, and the second sealed end surface 14a is affected by only the distortion of the carbon sealing ring body 141 alone (for example, , Nose section 141
a in the case where the tip end face a is the second sealed end face 14a). On the other hand, the distortion form of silicon carbide film 142 differs depending on its thickness T.
2 and the second sealed end face 14 due to the distortion interference
The effect on a also depends on the film thickness T. Therefore, the distortions of the two 141 and 142 are balanced so as to cancel each other, and the second sealed end face 14a due to those distortions is balanced.
(Hereinafter, the dimension is referred to as "parallel") so as to eliminate the influence of (the second sealed end face 14a is not substantially deformed and is maintained in a state parallel to the first sealed end face 12a before the operation is started). State maintenance value T ₀ ). In other words, if the film thickness T is set to a specific dimension (parallel state maintaining value T ₀ ), the second sealing end face 14a is moved to the second sealing end face 14a regardless of whether or not the carbon sealing ring body 141 causes pressure strain. 1
It is conceivable that a proper state parallel to the sealing end face 12a can be maintained.

Therefore, in the first seal M ₁ ,
A film having a dimension (parallel state maintaining value T ₀ ) such that the silicon carbide film 142 generates elastic strain balanced with the pressure strain of the sealing ring body 141 under high pressure conditions under which the carbon sealing ring body 141 causes pressure strain. Finding the thickness T, such a thickness T ₀
By forming the second sealed end face 14a with the silicon carbide film 142, the second sealed end face 14a is devised so as to be maintained in an appropriate state parallel to the first sealed end face 12a.

The film thickness T that satisfies the above conditions is, specifically, for example, when the sealed fluid pressure P is 30 kgf / cm ^2.
And the entire length of the second sealing ring 12 (the length in the axial direction including the silicon carbide film 142).
L is 21mm and the amount of projection of the nose portion 141a when (axial length) L ₀ is 5 mm (the nose portion 141
a is 187 mm and 199 mm, respectively, as is clear from the following experimental results, 0.8 mm ≦
It may be set within the range of T ≦ 1.2 mm.

That is, the first seal M _{1 having} the above-described configuration.
To make the film thickness T 0 mm, 0.1 mm, 0.3 m
m, 0.8mm, 1.0mm, 1.2mm, 1.5m
m, 2.0mm, 2.5mm, for each case was 3.0 mm, the non-sealed fluid region A ₂ in a state open to the atmosphere seal operation (the sealed fluid region A while using nitrogen gas as the sealed fluid Pressure at ₁ : 30kgf / cm
² ) was performed. The case where T = 0 mm means that no silicon carbide film is formed on the nose portion 141a and the nose portion 141a
The tip surface is a case where the mirror-finished to the second seal end faces 14a, a case of a conventional dynamic pressure type seal m ₁ the same structure shown in FIG.

The second sealed end face 14 during operation
The state (a) (the state with respect to the first sealing end face 12a) and the sealing performance were confirmed. The results were as shown in Table 1. The sealing performance is determined by the sealing end faces 12a, 14
The leakage amount of nitrogen gas from a was measured, and those that were within the allowable range were indicated by ○ as good sealing performance, and those that exceeded the allowable range were indicated by x as poor sealing performance. .

[0025]

[Table 1]

That is, T without the silicon carbide film 142
In the case of = 0 mm, the second sealed end face 14a was deformed to the outer height state (see FIG. 9B), and the amount of leakage greatly exceeded the allowable range. Such deformation of the second sealed end face 14a is as follows.
This is due to pressure distortion of the carbon sealing ring body 141.

On the other hand, T = 0.8 mm, 1.0 m
In the case of having a silicon carbide film 142 of m and 1.2 mm,
The second sealing end face 14a is maintained in an appropriate state parallel to the first sealing end face 12a as shown in FIG. The amount was also within the allowable range, and good sealing performance was exhibited. This is because the sealing ring body 141 made of carbon and the silicon carbide film 142 are formed by the pressure P of the sealed fluid (nitrogen gas).
This is because pressure strain different from the above occurs, and the pressure strains of the two 141 and 142 are balanced and canceled on the second sealed end face 14a, thereby preventing the deformation of the second sealed end face 14a.

However, even when the second sealing end face 14a is formed of the silicon carbide film 142, T = 0.1 mm, 0.3 m
When m, the second sealing end face 14a was deformed to an outer height state as shown in FIG. 3A, and a good sealing function could not be exhibited, as in the case where the silicon carbide film 142 was not provided. . As described above, even when the second sealing end face 14a is formed of the silicon carbide film 142, the thickness T thereof is maintained at the parallel state maintaining value T _0.
(0.8 mm ≦ T ₀ ≦ 1.2 mm), the influence of the pressure strain of the silicon carbide film 142 on the second sealing end face 14 a is the same as when the silicon carbide film 142 is not provided. However, the significance of existence of silicon carbide film 142 is not recognized. On the other hand, T = 1.5 mm, 2.0 mm, 2.
In the case of 5 mm and 3.0 mm, T = 0 mm, 0.
Contrary to the case of 1 mm and 0.3 mm, the second sealed end face 14a was deformed to the inner height state as shown in FIG. 3 (B). As described above, when the thickness T of the silicon carbide film 141 is made unnecessarily thick to make the thickness T larger than the parallel state maintaining value T ₀ , the thickness T of the silicon carbide film 141 on the second sealed end face 14 a is reduced.
The pressure-strain balance between 41 and 142 is lost, and a different deformation force is generated as compared with the case where the silicon carbide film 142 is not provided on the second sealed end face 14a, and the second sealed end face 14a is deformed to the inner height state. In any case, the sealing ring body 1
Since the pressure distortion of 41 and silicon carbide film 142 and the deformation of second sealing end face 14a are within the elastic limit, second sealing end face 14a is in a state parallel to first sealing end face 12a when the sealing operation is stopped. Was elastically restored. However, the film thickness T is maintained in a parallel state maintaining value T ₀ (0.8 mm, 1.0 mm,
1.2 mm), the second sealed end surface 14a was maintained in an appropriate state parallel to the first sealed end surface 12a during the period from the start of the sealing operation to the stop of the operation.

By the way, the shape of the second sealing ring 14 is various. In general, in addition to the above-mentioned shape, as shown in FIG. 4, a shape in which a nose portion 141a is provided on the outer peripheral side (FIG. The shape is roughly classified into a shape provided on the inner peripheral side (FIG. B) and a shape provided with no nose portion 141a (FIG. C). Even if the shape of the sealing ring 14 is different, as shown in FIG. As the size increases, the deformation state of the sealing end face 14a due to the pressure strain shifts from the outer height state to the inner height state via the parallel state. That is, FIG. 5 shows the film thickness T on the horizontal axis,
On the vertical axis, the degree of deformation of the second sealing end face 14a, that is, the amount of taper under high pressure conditions in which the second sealing ring 14 causes pressure distortion (as shown in FIG. 3, the axial distance between the inner and outer peripheral ends of the second sealing end face 14a) Where the taper amount in the outer height state is positive and the taper amount in the inner height state is negative)
FIG. 4 is a curve diagram illustrating a relationship between a film thickness T and a taper amount Δ.

As can be understood from this curve diagram, under a high pressure condition in which pressure distortion occurs in second sealing ring 14, regardless of its shape, silicon carbide film 142 is not provided (T = 0m).
m), the second sealed end face 14a is deformed to the outer height state,
Even when the silicon carbide film 142 is provided, when it is thin, the second sealing end face 14a is deformed to an outer height state. As the film thickness T increases, the outer height remains unchanged, but the taper amount Δ decreases. When the film thickness T reaches a certain value T ₀ , the second sealed end face 14
a shifts from the outer height state to the parallel state. Further, when the film thickness T increases, the second sealing end surface 14a shifts from the parallel state to the inner height state. When the film thickness T is increased in this manner,
The second sealing end face 14a shifts from the outer height state to the inner height state,
During the transition, the second sealed end surface 14a is always in a parallel state. The dimension of the film thickness T at this time is the above-mentioned parallel state maintaining value T ₀ , and such a parallel state maintaining value T ₀ exists in the sealing ring 14 of any shape. Also,
When the film thickness T exceeds the parallel state maintenance value T ₀ , the taper amount Δ increases as the film thickness T increases, although the outer height remains unchanged.

That is, between the film thickness T and the shape of the second sealing end face 14a under high pressure conditions, when the film thickness T is in the range of T <T ₀ , the sealing end face 1
4a is deformed to an outer height state, and the taper amount Δ decreases as the film thickness T increases. When the film thickness T is T = T ₀ , the sealing end face 14a is not deformed by pressure strain, When the film thickness T is maintained in a parallel state and the film thickness T is in the range of T> T ₀ , the sealing end face 1
4a is deformed to the inner height state, and the taper amount Δ increases as the film thickness T increases.
_{Although 0} depends on the shape of the sealing ring 14, the sealing ring 1
This is always true regardless of the sealing conditions such as the shape of No. 4. Even when the shape of the sealing ring 14 is different, the basic dimensions of the sealing ring 14 (mainly,
4 have the same total length L and the amount of protrusion L ₀ of the nose portion 141a, the film thickness dimension in which the sealed end faces 14a are maintained in a parallel state, that is, the parallel state maintaining value T ₀ is equal.

This has been confirmed by experiments. That is, an experiment was performed under the same conditions as the above-described experiment using the first seal having the same structure as that used in the above-described experiment except that the shape of the second sealing ring 14 was different. In this experiment,
As the second sealing ring 14, 3 shown in FIGS.
Kind of things were used. The total length L of each second sealing ring 14 and the protrusion amount L ₀ of the nose portion 141a (excluding those of FIG. 4C) were the same as those used in the above experiment.
As a result, in each case, the second sealed end face 14a
<0.8mm, outer height condition, 0.8mm ≦ T ≦ 1.2m
At m, it was a parallel state, and at T> 1.2 mm, it was an inner height state. Further, the taper amount Δ of the second sealing end surface 14a decreases as the film thickness T increases in the outer height state, and conversely,
In the inner height state, it increased as the film thickness T increased. In addition, as a result of performing many experiments of the same kind including these experiments, depending on the sealing conditions such as the shape of the second sealing ring 14, the parallel state maintaining value T ₀ is generally 0.3.
mm to 3.0 mm, and L / 90 ≦ T ₀ ≦ L / 3 based on the total length L of the second sealing ring 14 (including the one having no nose portion 141a) or the nose. the amount of protrusion L ₀ parts 141a may be found in a range of _{L 0/20 ≦ T 0 ≦} 2L 0/3 as a reference is found. Note that the parallel state maintaining value T ₀ is
This means a film thickness dimension when the second sealed end face 14a is maintained in a state where the parallelism between the two sealed end faces 12a and 14a is within a certain allowable range capable of exerting an appropriate sealing function. Therefore, the parallel state maintaining value T ₀ has a certain width, and even in the case of T = T ₀ , in a strict sense, the second sealed end face 14 a is deformed to the outer height state or the inner height state. However, even in such a case, the taper amount Δ is very small such that the parallelism is within an allowable range.

Therefore, the first seal M having the above-described structure is used.
According to ₁ , by setting the film thickness T to the parallel state maintaining value T ₀ , the second sealed end face 14 a is brought into an appropriate state parallel to the first sealed end face 12 a regardless of the pressure fluctuation in the sealed fluid region A _1. It is possible to maintain a good non-contact state between the sealing end faces 12a and 14a even under a high pressure condition in which pressure distortion occurs in the sealing ring main body 141 made of carbon. Functions can be demonstrated.

FIGS. 6 and 7 show an embodiment of the second seal. This second seal is, for example, a tapered face seal m when the outer peripheral side of the sealing end face is used as a fluid region to be sealed. in the form of dynamic pressure type seal m ₁ of the second seal end faces 24a in the _two possible second seal end faces 14 is very similar and the form when it is deformed to inner height condition, and sealing the carbon-made seal ring in high pressure conditions Between the end face deformation and the thickness of the silicon carbide film constituting the sealed end face,
Focusing on the fact that the form under the high pressure condition of the sealing end surface can be controlled by adjusting the film thickness, when the sealed fluid region is pressurized to a certain pressure or more, the relationship is orthogonal to the axial direction. second sealing end faces that are annular plane is automatically deformed to a similar annular tapered surface as in the tapered face seal m _2, and which has been devised as can exhibit good taper face features.

That is, as shown in FIG. 6, the second seal M ₂ in this embodiment comprises a first seal ring 22 fixed to a rotating shaft (for example, an impeller shaft) 21 and a seal case directly opposed thereto. (For example, a pump casing) 23 and a second sealing ring 24 held by
Facing end surface serving as the seal end faces 22a of 2,24 at between 24a, the sealed fluid region of its outer circumferential region (e.g., a pump chamber) A ₁ and an inner non-sealed fluid region that is a peripheral region (e.g., the seal Atmosphere region communicating with outside of case 23) L
Are sealed by a taper face sealing function. This second seal M ₂ has the same structure as the known taper face seal m ₂ shown in FIG. 10 except for the configuration of the second sealing ring 24 described below, and therefore the same members as those are the same. The details are omitted by attaching the reference numerals. The first sealing ring 2
Reference numeral 2 designates a first sealing end face 22a, which is a sealing end face, formed as an annular plane orthogonal to the axis, and is made of a super-hard material such as WC, SiC or the like. Under the conditions, the first sealing end face 22a is not deformed by the pressure strain.

Thus, in this second seal M ₂ ,
According to the present invention, the second sealing ring 24 is
As shown in (A), the sealing ring main body 241 is made of carbon that is softer than the constituent material of the first sealing ring 22, and the silicon carbide film 242 is formed by coating a part of the tip of the sealing ring by a conventional method. is there. The silicon carbide film 242 has a uniform thickness T, and the surface of the film is formed as a second sealed end face 24a that forms an annular plane parallel to the first sealed end face 22a. In other words, the second sealed end face 24a has a smooth surface perpendicular to the axis under low pressure conditions (for example, in an initial operation state) in which no pressure distortion occurs due to the sealed fluid at all in the sealing ring main body 241 made of carbon. As a matter of fact, it is mirror-finished.

[0037] Then, according for the second sealing second sealing end face 24a of the M _2, since the relationship of the ~ between the thickness T of the silicon carbide film 242 is established, the silicon carbide film 242 thickness ( The film thickness T after the surface is mirror-finished to the sealed end face) is set to a value exceeding the parallel state maintaining value T ₀ ,
Under high pressure conditions where pressure distortion within the elastic limit due to the sealed fluid occurs in the sealing ring main body 241 made of carbon (the first seal M
₁ is in normal operation), the second sealed end face 24a is not located between the first sealed end face 22a and the second sealed end face 22a due to the interference between the elastic strain generated in the silicon carbide film 242 and the pressure strain generated in the sealing ring main body 241. the annular tapered surface capable of forming an annular space 27 of progressively narrowed wedge-shaped cross section in the sealed fluid region a ₁ direction are devised so as to be elastically deformed. Note that the second seal ring 24 of the second seal M ₂ also has the parallel state maintaining value T, as in the second seal ring 14 of the first seal M ₁ .
₀ is generally in the range of 0.3 mm to 3.0 mm, or the total length of the second sealing ring 24 (the length in the axial direction including the film thickness T).
It can be found in the range of L / 90 ≦ T ₀ ≦ L / 3 based on L.

If T> T ₀ , the second sealed end face 24a can be elastically deformed to the inner height state regardless of the film thickness T, and the deformation amount, that is, the second sealed end face 24a As described above, the taper amount Δ increases as the film thickness T increases. On the other hand, there is a certain limit to the taper amount Δ that is optimal for exhibiting the tapered face sealing function well, and is generally 3 μm to 50 μm. Therefore, when determining the film thickness T, it is necessary to consider that Δ = 3 μm to 50 μm. Depending on the sealing conditions such as the shape of the second sealing ring 24, generally, the film thickness T 2
It is preferable to set it to about 8 mm to 8 mm.

[0039] According to a second sealing M ₂ configured as described above, the second seal end faces 24a in response to the pressure conditions of the sealed fluid region A ₁ is automatically elastically deformed, good tapered face seal Function is exhibited.

That is, by the operation of the second seal M ₂ ,
When the pressure of the sealed fluid region A ₁ is increased to a certain pressure or more, the film thickness T is set to T> T ₀ , so that the sealing ring main body 241 and the silicon carbide film 242 are formed as shown in FIG. The second sealed end face 24a is elastically deformed to an inner height state, that is, is deformed into a convex annular tapered face due to the strain interference of the sealing end faces 22a and 24a, and the leakage direction of the sealed fluid (the non-sealed fluid area A). An annular space 27 having a wedge-shaped cross section gradually narrowing in _two directions) is formed. As a result, the same principle as the tapered face seal m ₂ mentioned at the outset, the seal end faces 22
a, so that the inter-24a is held in equilibrium gap S ₀ serving constant small gap.

That is, the second seal M ₂ changes to a structure corresponding to the tapered face seal m ₂ , and FIGS.
As shown in FIG. 2, the closing force F generated by the back pressure by the sealed fluid pressure P acting on the back surface of the second sealing ring 24 (more precisely, by the back pressure and the urging force of the spring 26).
And opening force F _O caused by the pressure of the sealed fluid which has entered (static pressure) is to be balanced in the _C and the annular space 7,
The gap S between the sealing end faces 22a and 24a is a constant equilibrium gap S
It will be kept at ₀ .

[0042] Then, since such a taper amount Δ of the second sealing end face 24a for forming a tapered face seal structure in which is ensured by the pressure distortion, as in a tapered face seal m ₂ mentioned in the introduction pressure strain As a result, the taper amount Δ does not decrease and the annular space 27 does not disappear, and a good taper face sealing function is exhibited.

On the other hand, immediately after the start of the sealing operation or the like, that is, no pressure distortion occurs in the second sealing ring 24 (including a case where the pressure distortion disappears due to a pressure drop due to the stop of the rotating shaft 21). Below, the second sealed end face 2
4a is not deformed or elastically returns to its original state to form an annular plane orthogonal to the axial direction, and the sealing end faces 22a, 24a
Are in a parallel state. Thus, the sealing end faces 22a, 24a
There in a state parallel, the seal end faces 22a, opening force F _O only open against the inter-24a back pressure serving closing force F _C is not generated.
Therefore, although the tapered face sealing function is not exhibited, the good sealing function is exhibited by the same function as the so-called end face type seal by the relative rotation sliding contact between the sealing end faces 22a and 24a via the fluid film. Become. That is, even under a low pressure condition in which the taper face seal function is not exhibited, the taper face seal structure is automatically changed to the end face contact type mechanical seal structure, a good seal function is exhibited, and the sealed end faces 22a, 24 are provided.
There is no case where a large amount of leakage occurs between the points a.

In the tapered face seal m ₂ , it is necessary to mirror-finish the second sealing end face 24 a into a tapered face, but the taper amount Δ is very small (the sealing ring 2).
In general, Δ =
Such a process is extremely difficult because the cost is about 3 μm to 50 μm), and the processing cost of the sealing end face 24 a (and the manufacturing cost of the sealing ring 24) rises unnecessarily, and appropriate processing accuracy can be ensured. It's not easy. However, the second sealing M _2, since it is not necessary to process the second sealing end face 24a to the tapered surface, such processing on the fabrication problems are not.

By the way, the first and second seals M ₁ , M ₂
Is not limited to the above-described embodiment, and can be appropriately improved and changed without departing from the basic principle of the present invention.

For example, in each of the first and second seals M ₁ and M ₂ having the above-described configuration, the inner peripheral area of the sealed end face is the sealed fluid area A ₁ and the outer peripheral area is the non-sealed fluid area A 1. It can be used when it becomes ₂ . However, in this case, the relationship between the outer height state and the inner height state on the second sealed end surfaces 14a, 24a is opposite to the case described above. For example, if T> T ₀ in the second sealing M _2, the high pressure conditions, a second sealing end face 24a is deformed to the outside high state,
Exhibits the taper face seal function. Further, the first sealing rings 12 and 22 are provided on the sealing cases 13 and 23 side,
It is also possible to provide the sealing rings 14, 24 on the rotating shaft 11, 21 side.

[0047]

As can be easily understood from the above description, according to the present invention, the second sealing end face of the non-contact type mechanical seal using the second sealing ring made of carbon is inevitably generated. Reduction of sealing function due to pressure distortion
A non-contact type that can reliably prevent the sealing end face from being formed of a silicon carbide film having a specific thickness and exerts a good sealing function even under a high pressure condition in which pressure distortion occurs in the second sealing ring. A mechanical seal can be provided.
Moreover, by adjusting the film thickness, the shape of the second sealing end surface under high-pressure conditions can be freely controlled. Therefore, a non-contact mechanical device capable of exhibiting a good sealing function according to the sealing conditions including the sealing structure. The seal can be easily designed and manufactured, and the seal function as designed can be exhibited.

[Brief description of the drawings]

FIG. 1 is a half cut longitudinal side view showing an example of a first seal.

FIG. 2 is an operation explanatory view showing an enlarged main part of FIG. 1;

FIG. 3 is a diagram corresponding to FIG. 2, showing a deformed state of a second sealing end surface when the film thickness is inappropriate.

FIG. 4 is a longitudinal sectional side view showing a modification of the second seal ring in the first seal.

FIG. 5 is a curve diagram showing a relationship between a film thickness T and a taper amount Δ of a second sealing end surface.

FIG. 6 is a half sectional vertical side view showing an example of a second seal.

FIG. 7 is an operation explanatory view showing a main part of FIG. 6 in an enlarged manner.

FIG. 8 is a half cut longitudinal side view showing a conventional dynamic pressure seal.

FIG. 9 is an operation explanatory view showing an enlarged main part of FIG. 8;

FIG. 10 is a half cut longitudinal side view showing a conventional tapered face seal.

FIG. 11 is an explanatory view showing a pressure distribution or an opening / closing force acting between the two sealed end faces when the second sealed end face is a worked or elastically deformed annular tapered face.

FIG. 12 is a curve diagram showing the relationship between the gap between the two sealed end faces and the opening / closing force when the second sealed end face is a worked or elastically deformed annular tapered face.

[Explanation of symbols]

 11, 21 ... rotating shaft, 12, 22 ... first sealing ring, 12
a, 22a: First sealed end face, 13, 23: Seal case
, 14, 24 ... second sealing ring, 14a, 24a ... second dense
Sealed end face, 141, 241: Seal ring body, 141a: No
Part (part of the sealing ring body), 142, 242 ... silicon carbide
Membrane, 27 ... Annular space, A₁... A sealed fluid area, A_Two… Non
Sealed fluid area, M₁… First seal (non-contact mechanical
Seal), M _Two… Second seal (non-contact type mechanical seal)
）), T: film thickness, Δ: taper amount.

Claims (2)

[Claims] 1. A relative rotation between a first sealing ring and a second sealing ring made of carbon softer than its constituent material under a high-pressure condition in which a pressure distortion within an elastic limit is caused in the second sealing ring by a sealed fluid. Accordingly, a non-contact type mechanical seal configured to seal a sealed fluid region and a non-sealed fluid region, which are inner and outer peripheral regions, between the first and second sealed end surfaces as opposed end surfaces of both sealing rings. Wherein the second sealing ring is constituted by a carbon sealing ring main body and a silicon carbide film coated on a part thereof, and the film surface is formed on the first sealing end face under a low pressure condition under which the pressure distortion does not occur. The silicon carbide film is formed on the second sealing end face forming an annular plane parallel to the silicon carbide film so as to maintain the film thickness under the high pressure condition so that the second sealing end face maintains the shape under the low pressure condition. Pressure generated in the sealing ring body A non-contact type mechanical seal characterized by being set so as to generate elastic strain balanced with force strain. 2. A relative rotation between a first sealing ring and a second sealing ring made of carbon softer than a constituent material thereof under a high-pressure condition in which a pressure distortion within an elastic limit is caused in the second sealing ring by a sealed fluid. Accordingly, a non-contact type mechanical seal configured to seal a sealed fluid region and a non-sealed fluid region, which are inner and outer peripheral regions, between the first and second sealed end surfaces as opposed end surfaces of both sealing rings. Wherein the second sealing ring is constituted by a carbon sealing ring main body and a silicon carbide film coated on a part thereof, and the film surface is formed on the first sealing end face under a low pressure condition under which the pressure distortion does not occur. And a second sealing end face which forms an annular plane parallel to the inner ring. The thickness of the second sealing end face is controlled by interference between elastic strain generated in the silicon carbide film and pressure strain generated in the sealing ring main body under the high pressure condition. Sealed end face is first sealed A non-contact type mechanical seal which is set so as to be elastically deformed into an annular tapered surface capable of forming an annular space having a wedge-shaped cross section gradually narrowing in a non-sealed fluid region direction with an end face.