JPS6333027B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dynamic pressure non-contact mechanical seal that is often used as a shaft sealing device for rotating equipment. This invention relates to improvements in dynamic pressure type contact mechanical seals that are mainly intended for shaft seals where the pressure increases.

The typical configuration of this type of dynamic pressure type non-contact mechanical seal (hereinafter abbreviated as mechanical seal) is as shown in Fig. 3, in which the rotating shaft 2 is inserted into the casing 1, and the right side of the figure is the low pressure side, When the left side of the drawing is the high pressure side, the rotating seal ring 3 is attached to the rotating shaft 2.
is equipped with a fixed seal ring 6 via a back-up spring 4 on a flange 5 fixed to the casing 1 side, and thus both seal rings 3, 6
are faced parallel to and in the same direction as the rotating shaft axis, and a fixed seal ring 6 and a back-up spring 4 are supported from the back by a spring 7. In addition, a spiral groove (hereinafter referred to as groove) 8 is machined in the rotary seal ring 3 on the sealing surface with the stationary seal ring 6 so as to have an advancing angle in the direction of rotation of the rotary shaft 2. Ru. The tip of this groove 8 is opened to the high pressure side. In this mechanical seal structure, when the rotating shaft 2 rotates, fluid enters the groove 8 having an advancing angle in the direction of rotation, and dynamic pressure is generated between the rotating seal ring 3 and the stationary seal ring 6. Due to the pressure balance between this pressure and the spring 7, both the seal rings 3 and 6 are kept in a non-contact state.

By the way, the structure and shape of conventional mechanical seals are designed with emphasis on maximizing the dynamic pressure effect, which is preferable when dealing with low-viscosity fluids such as gas, but when dealing with high-viscosity fluids such as oil. When sealing viscous fluid under high circumferential speed conditions, the dynamic pressure generated in groove 8 becomes excessive, and the gap between the sealing surfaces of both seal rings 3 and 6 during the above-mentioned balance becomes large, causing leakage from the high pressure side to the low pressure side. The amount increases. In addition, due to excessive distortion of the sealing surface due to high dynamic pressure, there is an inconvenience that both seal rings 3 and 6 come into surface contact. This led to the idea being devised.

That is, in FIG. 4, the length l in the radial direction (depth) of the groove 8 is shortened, in FIG. 5, the advancing angle α of the groove 8 is made shallow, and in FIG. On the contrary, in FIG. 7, the area of the groove 8 is made extremely large to reduce the dynamic pressure.

However, according to the configurations shown in FIGS. 4 to 7, the influence of machining errors of the groove 8 is large and complicated, and the difference between the theoretical value and the actual value of the generated dynamic pressure is large due to the decrease in machining accuracy, and the design calculation In addition to being difficult, it also has the disadvantage of lacking reliability. Further, according to the configuration shown in FIG. 6, since the groove width d is narrow, slurry and abrasion particles accumulate, making it impossible to generate dynamic pressure, and the pressure distribution is complicated, making calculation of dynamic pressure difficult. Further, in any of the configurations shown in FIGS. 4 to 7, the sealing surface area is large, the amount of heat generated within the sealing surface is large, and the problem of distortion cannot be solved.

Therefore, an object of the present invention is to provide a material that is easy to process;
Another object of the present invention is to provide a mechanical seal having a structure in which the theoretical calculation of generated dynamic pressure is simple and thermal distortion is minimal.

That is, the present invention brings a rotating seal ring and a stationary seal ring into contact with each other, and uses the dynamic pressure generated by the dynamic pressure generating groove to seal the two rings while keeping them in a non-contact state. Divided into a dynamic pressure generation area and a non-dynamic pressure generation area in the circumferential direction, a groove with a shallow groove depth is formed in the dynamic pressure generation area, and a deep groove depth is formed in the non-dynamic pressure generation area. It is characterized by forming a groove having a

According to the present invention, in the dynamic pressure generating region, significant dynamic pressure is generated due to the shallow groove, and in the non-dynamic pressure generating region, the generated dynamic pressure is eliminated due to the deep groove.

In this way, the area where dynamic pressure is generated is limited to a few narrow areas on the circumferential direction of the seal surface, and the boundaries between areas where no dynamic pressure is generated are clearly distinguished, so the pressure distribution during rotation can be accurately estimated. Therefore, accurate theoretical calculations can be made in advance.

Furthermore, since the length l, advance angle α, and width d of the groove in the dynamic pressure generation region are not modified, the groove is easy to process and the processing accuracy is high, and the estimation of the generated dynamic pressure will continue to be more accurate. Can be done.

Further, since the dynamic pressure generation area is limited (narrowed), even if the dynamic pressure generated in the area is large, the opening force of the entire sealing surface can be made small.

Therefore, it becomes easier to balance the pressure at equilibrium, and the gap between the sealing surfaces can be narrowed, resulting in a seal structure with less leakage.

Furthermore, by making the grooves deep in the non-dynamic pressure generation region, heat generation due to viscous shear of the fluid between the seal surfaces can be suppressed, and thermal distortion of the seal surfaces can be suppressed to a small level. At the same time, the amount of sealing liquid circulating in the area increases, improving the cooling effect of the sealing part.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In the rotary seal ring 9, the seal surface 10 that is in contact with the fixed seal ring 6 is divided into a dynamic pressure generating area A and a non-dynamic pressure generating area B alternately in the circumferential direction. As is clear from FIG. 1, the dynamic pressure generating area A is narrower than the non-dynamic pressure generating area B, and each dynamic pressure generating area A has the same area width.
Therefore, each non-dynamic pressure generating region B also has the same region width.

Then, in each dynamic pressure generation area A, an equal number of grooves 11 are etched with a relatively shallow groove depth and an advancing angle, which is almost the same as that conventionally processed under low viscosity liquid and low circumferential speed conditions. On the other hand, in each non-dynamic pressure generating region B, a groove 12 having one deep groove depth over the width of the region is machined with the same advancing angle. The other surfaces are flat as before, and the sealing surface of the fixed seal ring 6 is also flat.

In the mechanical seal having such a groove structure, high dynamic pressure is generated in the dynamic pressure generation area A due to the shallow groove depth of the groove 11, but in the non-dynamic pressure generation area B, the groove 12 has a shallow groove depth. Since the groove depth is deep, almost no dynamic pressure is observed. Therefore, the sealing surface gap between the rotating seal ring 9 and the stationary seal ring 6 is determined by the pressure balance between the dynamic pressure generated in the dynamic pressure generating area A and the spring 7.

Therefore, even if the dynamic pressure generated in the dynamic pressure generation area A is high due to high viscosity fluid such as oil and high circumferential speed, the area A is limited to a few locations in the circumferential direction of the seal surface. Therefore, the total dynamic pressure generated is lower than that of the conventional type in which dynamic pressure is generated around the entire circumference of the sealing surface 10, and therefore the sealing surface gap can be kept narrow.

Furthermore, if the non-dynamic pressure generating area B is provided and the groove 12 in this area is made deeper, the sealing surface area between the rotary seal ring 9 and the stationary seal ring 6 will be substantially reduced by the area B. The area of the heating surface can be reduced. Moreover, with rotation, groove 12
As a large amount of fluid flows into and out of the sealing surface, the heat generated at the sealing surface is removed, a cooling effect is effectively performed, and thermal distortion is suppressed.

The optimal values for the number of dynamic pressure generating parts A and the ratio of regions A and B change depending on the sealing conditions, and the higher the viscosity and peripheral speed, the smaller the ratio of region A needs to be. Since the region A in which pressure is generated and the region B in which pressure is not generated are clearly distinguished, the theoretical calculation of the generated dynamic pressure is easy and the difference from the actual value can be eliminated, which is practical.

In addition, as the dynamic pressure generation area A,
In the figure, a spiral groove is used, but as another embodiment of the present invention, a rotary seal ring 13 shown in FIG. 8 may be used, and this rotary seal ring 1
3, similarly to the rotary seal ring 9 shown in FIG. 1, dynamic pressure generating areas A and non-dynamic pressure generating areas B are provided alternately along the circumferential direction. A groove 14 having a shallow groove depth in a so-called Rayleigh step shape may also be formed.

In other words, groove 14 of the shallow depth shown in FIG.
is a substantially rectangular groove with a shallow depth when viewed from the front of the rotary seal ring 13;
One end of the groove is open with respect to the direction of rotation of No. 3.

It should be noted that the material of the sealing surface 10 explained in the embodiment needs to be a hard material in the grooved portion due to wear resistance, but a soft material such as carbon can be used in the flat portion.

Further, in the above embodiment description, the dynamic pressure generating portion A was formed on the outer diameter side of the seal ring 9, and the seal portion was formed on the inner diameter side, but depending on the sealing conditions, these relationships may be reversed.

Furthermore, in addition to high viscosity liquid and high circumferential speed conditions, the present invention
Of course, it can also be used under conditions of medium viscosity liquid and medium circumferential speed.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention, with FIG. 1 being a front view of a rotary seal ring, and FIG. 2 being a cutaway view taken along the line -- in FIG. Figure 3 is a cross-sectional view for explaining the dynamic pressure type non-contact mechanical seal structure, and Figures 4 to 7 show the main points of the sealing surface, respectively, showing conventional measures for generating dynamic pressure against high viscosity liquid and high circumferential speed conditions. FIG. 8 is a front view of a non-rotating seal ring showing another embodiment of the present invention. 1... Casing (fixed side), 2... Rotating shaft (rotating side), 6... Fixed seal ring, 7... Spring,
9... Rotating seal ring, 11, 14... Groove with shallow groove depth, 12... Groove with deep groove depth, A...
Dynamic pressure generation area, B... non-dynamic pressure generation area.

Claims (1)

[Claims] 1 A rotary seal ring fixedly mounted on the rotating side and a fixed seal ring movably held in the axial direction via a spring are brought into contact with each other on the stationary side, and a groove for generating dynamic pressure having an advancing angle is provided on the sealing surface. The sealing surface is divided alternately and circumferentially into a dynamic pressure generating area and a non-dynamic pressure generating area,
A dynamic pressure type non-contact mechanical seal formed by forming a groove having a shallow groove depth in a dynamic pressure generating area and forming a groove having a deep groove depth in a non-dynamic pressure generating area.