JPH0660690B2 - Dynamic pressure non-contact mechanical seal - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a dynamic pressure non-contact mechanical seal applied to a shaft sealing portion of a rotary device for high pressure fluid such as a gas turbine, a blower and an air compressor. Is.

[Prior Art] Conventionally, as a seal device applied to a shaft sealing portion of a rotary device for high-pressure fluid such as a gas turbine, a blower, and an air compressor, the Japan Society of Mechanical Engineers (C edition) 5
Volume 3 No. 491, Paper No. 86-0778A No. 1487
The "Rayleigh step end face seal with reverse step" published on pages 1493 is known.

As shown in FIG. 1, the sealing device described in the above document has a rotary seal ring 2A that rotates integrally with a rotary member 1 (a rotary sleeve 1B that rotates simultaneously with the rotary shaft 1A in the illustrated example) of a device to be sealed. The rotary side sealing element 2 and the spring retainer 3A fixed to the casing 3 side of the device to be sealed.
In addition, a stationary side seal element provided with a stationary seal ring 4A which is non-rotatably held via detent pins 3B arranged at equal intervals in the circumferential direction and which is constantly urged to move toward the rotary seal ring 2A by a spring 3c. 4 and the rotary seal ring 2A
As shown in FIG. 4, a plurality of narrow and deep fluid introduction grooves 5 extending in the circumferential direction and extending in the radial direction are formed on the sealing surface 2a of the above, and communicated with each of these fluid introduction grooves 5. In addition, in order to increase the dynamic pressure generated in one step in the radial direction, the dynamic pressure generating groove 6 having a shallow bottom extending to one side in the circumferential direction, for example, the side opposite to the rotational direction indicated by the arrow a, is made as wide as possible in the radial direction. It is a dynamic pressure non-contact type mechanical seal formed in.

In the dynamic pressure non-contact type mechanical seal configured as described above, the rotary seal ring 2A rotates as the rotary member 1 of the shaft-sealed device rotates. This rotation causes the fluid on the high-pressure side Y to move into the fluid introduction groove 5
Flows into the dynamic pressure generating groove 6 from the
A dynamic pressure is generated between the seal surface 2a of A and the seal surface 4a of the stationary seal ring 4A, and the seal surface 4a is sealed by the seal surface 2a.
The urging force in the direction of separating from the sealing surface 2a acts on the both sealing surfaces 2a by the pressure at the balance point between this urging force and the spring force of the spring 3C that urges the sealing surface 4a to move in the direction of abutting the sealing surface 2a. , 4a to form a narrow seal gap of, for example, about 5 to 20 μm to seal the low pressure side X and the high pressure side Y in a non-contact state.

[Problems to be Solved by the Invention] In the conventional dynamic pressure non-contact type mechanical seal having the above configuration,
Since only a one-step dynamic pressure generating groove 6 that is wide in the radial direction is formed on the sealing surface 2a of the rotary seal ring 2A so as to communicate with the fluid introduction groove 5, both sealing surfaces 2a and 4a face each other in parallel. In a normal state, as shown in FIG. 5 (a), the generated dynamic pressure can be made sufficiently large and the rigidity of the gap can be made high, but on the other hand, the rotary seal ring 2A is not evenly and radially high in the radial direction. Due to being added, this rotary seal ring 2A
When the seal surfaces 2a and 4a are relatively inclined due to distortion of the seal surface, the parallelism between the seal surfaces 2a and 4a is broken, and the generated dynamic pressure escapes from the side with a large facing seal gap. As shown in b), it exhibits a sharp pressure drop. As a result, the force for opening the seal surfaces 2a, 4a is significantly weakened against the force for closing the seal surfaces 2a, 4a from the back side of the stationary seal ring 4A including the spring force of the spring 3C, and The action of returning the seal surfaces 2a and 4a to the parallel facing posture does not work either. As a result, the seal surfaces 2a and 4a come into contact with each other and the seal is broken or the seal surface 2
There is a problem that troubles such as damage of a and 4a are likely to occur. The solid line in FIG. 5 indicates the average pressure distribution generated in the dynamic pressure generating groove 6.

The present invention has been made in view of the above circumstances, and suppresses a decrease in dynamic pressure when the sealing surface is inclined,
It is an object of the present invention to provide a dynamic pressure non-contact type mechanical seal that can ensure a seal gap and avoid contact trouble between seal faces by exerting a restoring force of the seal faces to a parallel facing posture.

[Means for Solving the Problems] In order to achieve the above object, a dynamic pressure non-contact mechanical seal according to the present invention has an outer end radially outward on the seal face of a rotary seal ring at equal intervals in the circumferential direction. A plurality of fluid introduction grooves that are open and extend in the radial direction are formed so that the inner end is present in the sealing surface, and a dynamic pressure generating groove that communicates with each of the fluid introduction grooves and extends in at least one of the circumferential directions is formed. The dynamic pressure generating grooves are individually divided into a plurality of pieces in the radial direction.

[Operation] According to the present invention having the above-described configuration, by the rotation of the rotary seal ring,
Fluid enters the dynamic pressure generation groove that communicates with the fluid introduction groove from the radially outer side (high pressure side) to generate dynamic pressure, and this dynamic pressure forms a predetermined seal gap to achieve a predetermined seal in a non-contact state. Let me do it.

At this time, for example, when the seal surface is tilted due to distortion of the rotary seal ring and the seal gap becomes non-uniform in the radial direction, the dynamic pressure generated in the dynamic pressure generation groove on the wide side of the seal gap is remarkable. Although it decreases, the decrease in the dynamic pressure generated in the dynamic pressure generation groove on the narrow side of the seal gap is suppressed due to the narrow width of the groove, and as a whole, it is possible to secure sufficient dynamic pressure so that the sealing surfaces do not contact each other. A sufficient moment acts to return the seal surface to the parallel facing posture due to the difference in the dynamic pressure in the radial direction, and a predetermined sealing performance can be secured.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a vertical sectional side view showing the overall structure of a dynamic pressure non-contact type mechanical seal, and FIG. 2 is a front view of a rotary seal ring of the present invention. In the present invention, it is formed on the seal surface of the rotary seal ring. FIG. 1 shows an embodiment of the present invention, except that the dynamic pressure generating groove is divided into a plurality of parts in the radial direction, which is the same as the conventional example except for this point, and other members and configurations are the same. And the conventional example, and in FIG.
The parts corresponding to those in FIG. 4 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 2, on the sealing surface 2a of the rotary seal ring 2A,
A plurality of (for example, 12) fluid introduction grooves 5 are formed at equal intervals in the circumferential direction so that the outer ends open radially outward (high-pressure side Y) of the seal surface 2a and the inner ends extend inside the seal surface 2a. ) Is formed.

The fluid introduction groove 5 extends radially from the outer end of the seal surface 2a, and its depth is set to 5 μm to 1 mm.

Further, the fluid introduction groove 5 is communicated with each of the fluid introduction grooves 5, extends to one side (counterclockwise direction) in the circumferential direction, and has a depth of 2 to 20 μm.
The dynamic pressure generating groove 6 set to 1 is formed. A plurality of these dynamic pressure generating grooves 6 are formed independently at the seal surface 2a of the rotary seal ring 2A at equal intervals in the radial direction (three in the illustrated example, but four or more). It may be) narrow width grooves 6A, 6B, 6C, and the sum of the widths of these grooves is 30 to 70% of the surface width W (diametrical dimension) of the sealing surface 2a. (About 59% in the illustrated example).

In the case of the above-mentioned configuration, by rotating the rotary seal ring 2A in the direction of the arrow a, the fluid on the high-pressure side Y from the fluid introduction groove 5 divides the dynamic pressure generating groove 6 into the respective narrow narrow grooves 6
A, 6B, and 6C flow in to generate a dynamic pressure between the seal surface 2a of the rotary seal ring 2A and the seal surface 4a of the static pressure seal ring 4A, and the dynamic pressure causes the seal surface 2a to move from the seal surface 4a. The seal surface 2a is urged in the separating direction, and by the pressure at the balance point between this urging force and the spring force of the spring 3C,
A narrow seal gap of, for example, about 5 to 20 μm is formed between 4a to seal the low pressure side X and the high pressure side Y in a non-contact state.

Here, when the sealing faces 2a and 4a facing each other are relatively inclined as shown in FIG. 3 due to, for example, distortion of the rotary seal ring 2A due to the reason as described above, the side where the seal gap is wide. , That is, the divided narrow groove 6B on the radially inner side,
Although the dynamic pressure generated in 6C is reduced, the dynamic pressure generated in the divided narrow groove 6A on the outer side in the radial direction is suppressed, and sufficient dynamic pressure is ensured so that both seal surfaces 2a, 4a are not brought into contact with each other. Can be generated and both sealing surfaces 2
Since the moment M that tries to restore the a and 4a to face-to-face parallel to each other is generated, a predetermined seal gap is secured, and it is possible to surely prevent the seal breakage and the seal faces 2a and 4a from being damaged.

[Effects of the Invention] As described above, according to the present invention, by dividing the dynamic pressure generating groove into a plurality of independent pieces in the radial direction, even if the sealing surface is inclined, it is possible to reduce By suppressing the decrease in dynamic pressure that occurs in the narrow groove, it is possible to reliably avoid contact trouble between the sealing surfaces and generate a moment to restore the sealing surfaces to a parallel facing posture. It can be returned to a predetermined seal gap. Therefore, just by making a simple configuration improvement,
It is possible to prevent breakage of the seal and damage to the seal surface, and ensure highly reliable and safe sealing performance for a long period of time.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of the entire structure showing the present invention and a conventional example in common, FIG. 2 is an enlarged front view of a rotary seal ring of the present invention, and FIG. 3 is a case where a sealing surface of the present invention is inclined. FIG. 4 is a pressure distribution characteristic diagram, FIG. 4 is an enlarged front view of a conventional rotary seal ring, and FIG.
Figures (a) and (b) are pressure distribution characteristics of the conventional example.
Is a pressure distribution characteristic diagram in a normal operating state, and (b) is a pressure distribution characteristic diagram when the sealing surface is inclined. Further, in FIGS. 3 and 5, the chain double-dashed line is a continuous pressure distribution corresponding to the sealing surface, and the solid line is an average pressure distribution when the sealing surface is divided into a groove area and other areas. 1 ... Rotating member, 2 ... Rotating side sealing element, 2A ... Rotating sealing ring, 2a ... Sealing surface, 3C ... Spring, 4 ...
... Fixed-side sealing element, 4A ... stationary sealing ring, 5 ... fluid introduction groove, 6 ... dynamic pressure generating groove, 6A, 6B, 6C ...
… Divided narrow groove.

Claims (1)

[Claims] 1. A rotary side sealing element provided with a rotary seal ring that rotates integrally with a rotary member of a shaft-sealed device, and a non-rotatable member on the casing side of the shaft-sealed device, and a spring side of the rotary seal ring. In a mechanical seal having a stationary side seal element provided with a stationary seal ring that is constantly urged to move, an outer end of the rotary seal ring is opened radially outward at equal intervals in the circumferential direction on the seal surface of the rotary seal ring. A plurality of fluid introduction grooves extending in the radial direction are formed so that the ends are in the sealing surface, and a dynamic pressure generating groove communicating with each of the fluid introduction grooves and extending in at least one of the circumferential directions is formed. A dynamic pressure non-contact mechanical seal characterized in that each of the generated grooves is divided into a plurality of grooves independently in the radial direction.