JPS5926128Y2 - mechanical seal - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a mechanical seal suitable for high-pressure fluid.

As shown in FIG. 1, a rotating sealing ring 2 that is non-rotatably fitted to the rotating shaft 1 and a stationary sealing ring 4 that is fixed to the inner wall of a frame 3 surrounding the rotating shaft 1 are connected to each other. Mechanical seals in which an intermediate sealing ring 5 is interposed between opposing sealing surfaces 6 and 7 and fluid is sealed by each sealing surface 6 and 7 have been widely used.

However, when sealing high-pressure fluid with this type of mechanical seal, the pressure of each sealing ring on the seal surfaces 6 and 7 is set high, so the material of the intermediate sealing ring is self-lubricating, such as carbon graphite. Therefore, it is necessary to improve the frictional condition of the sealing surface by using a material having the following properties.

However, in general, carbon graphite materials have a smaller elastic modulus than metal materials and are therefore extremely easily deformed by hydraulic pressure, which causes many problems, especially in mechanical seals for high-pressure fluids.

For example, in a mechanical seal using an intermediate sealing ring 5 having a T-shaped axial cross section as shown in FIG. has a distribution state whose direction and size are approximately represented by arrows in FIG. 2a.

Considering the deformation of the intermediate sealing ring 5 due to the hydraulic pressure at this time, due to the hydraulic pressure applied in the same direction as the rotating shaft 1, the inner diameter side of the sealing surface of the intermediate sealing ring is changed as shown in Fig. 2. Due to the hydraulic pressure applied in the radial direction of the rotating shaft 1, the outer diameter side of the sealing surface of the intermediate sealing ring 5 tends to deform into a convex shape, as shown in FIG. 2C.

Therefore, when axial hydraulic pressure and radial hydraulic pressure are applied to the intermediate sealing ring 5 at the same time, the intermediate sealing ring 5
Depending on the ratio between the width P of the sealing surface and the amount of protrusion n of the sealing surface, the influence of the hydraulic pressure in the axial direction becomes larger than the influence of the hydraulic pressure in the radial direction, and the inner diameter side of the sealing surface of the intermediate sealing ring 5 becomes convex. Or, conversely, the influence of the hydraulic pressure in the radial direction becomes greater than the influence of the hydraulic pressure in the axial direction, which determines whether the outer diameter side of the sealing surface of the intermediate sealing ring 5 becomes convex.

Therefore, if the hydraulic pressure is set constant and the ratio P/n of the width P of the sealing surface and the protrusion amount n of the sealing surface is appropriately selected, the influence of the hydraulic pressure in the axial direction and the influence of the hydraulic pressure in the radial direction can be reduced. are balanced, and as a result, it is possible to eliminate the inclination of both end seal surfaces due to deformation of the intermediate seal ring 5.

However, the ratio p between the width P of the sealing surface and the protrusion amount n of the sealing surface
There is a natural limit to reducing /n due to the material strength of the intermediate sealing ring 5, so if the hydraulic pressure exceeds a certain range, deformation of the intermediate sealing ring 5 can be eliminated by balancing the hydraulic pressure applied to each surface. This makes it impossible to maintain the parallelism of the sealing surfaces, which impairs the sealing performance.

For this reason, recently, as shown in FIG.
6, the sealing surface 8 at both ends is suppressed from deformation due to the influence of hydraulic pressure.
Mechanical seals have been devised that prevent the parallelism of the . It is difficult to manufacture, and it is difficult to determine the shape to balance the distortion caused by the hydraulic pressure mentioned above.

The present invention was developed in light of these circumstances, and addresses the unique problems that arise when a carbon graphite intermediate sealing ring with a T-shaped cross section is used without liquid pressure acting on its inner wall surface. , a mechanical system capable of solving the problem that when high fluid pressure acts on the outer wall surface of the intermediate sealing ring, distortion occurs in the intermediate sealing ring itself, resulting in a reduction in sealing performance, with a simple configuration. It is intended to provide a seal.

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

As shown in FIG. 4, a rotating shaft 1 provided within a frame 10
A rotary sealing ring 13 is fitted onto the rotary shaft 12 so as to be non-rotatable with respect to the rotary shaft 12 but slidable in the direction of the rotary shaft.

Further, a stationary sealing ring 14 is attached to the inner wall of the frame 10 around the rotating shaft 12 so as to surround the rotating shaft 12, and the stationary sealing ring 14 is attached to the frame 10 by a rotation prevention pin 15.
It is made to not rotate relative to 0.

Further, an intermediate sealing ring 18 made of carbon graphite is provided between the end surfaces 16 and 17 of the stationary sealing ring 14 and the rotating sealing ring 13, which face each other, so that both end sealing surfaces of the intermediate sealing ring 18 are in contact with the respective end surfaces 16 and 17. and is interposed so that no hydraulic pressure acts on its inner wall surface.

On the other hand, a spring retainer 19 is fitted to the rear of the other end of the rotary sealing ring 13 on the rotary shaft 12 so that it cannot rotate with respect to the rotary shaft, and the force of the spring 20 held by the spring retainer 19 is applied to the rotary sealing ring. 13 is pressed against the intermediate seal ring 18 to seal the fluid present around the outer circumference of the rotary seal ring 13.

Further, the intermediate sealing ring 18 has a T-shaped cross section in the rotational axis direction with the sealing surface projecting parallel to both sides thereof, and the groove A provided in the circumferential direction on the inner wall surface has a U-shaped cross section. The size is set to be necessary and sufficient to balance the deformation of the intermediate sealing ring 18 caused by hydraulic pressure and to maintain the parallelism of both sealing surfaces 6 and 7.

Specifically, an intermediate sealing ring 18 having dimensions as shown in FIG.
It is known that it is sufficient to determine the size of the groove A such that the following relationship holds true.

Note that P is the sealing surface 16. of the intermediate sealing ring 18. 17, and n is the width of this sealing surface 16. 17, ρ is the radius of curvature of the arcuate groove bottom of groove A, and t is the groove depth of groove A.

With such a configuration, the intermediate sealing ring 18 having the groove A has a convex outer diameter side of both end sealing surfaces compared to an intermediate sealing ring having the groove A and having the same dimensions and material. Even if the width P of the sealing surface and the ratio p/n of the protrusion amount n of the sealing surface are the same, it will deform under much higher hydraulic pressure than the intermediate sealing ring without the groove A. The effect of the hydraulic pressure that tries to deform the outer diameter side of the sealing surfaces at both ends into a convex shape and the influence of the hydraulic pressure that tries to deform the inner diameter side of the sealing surfaces at both ends into a convex shape are balanced, and the sealing surfaces at both ends are Can be maintained in an ideal parallel state.

Therefore, as shown in FIG. 3, the intermediate sealing ring 26 is reinforced by providing a metallic reinforcing ring 27 on the convex portion of the inner wall of the intermediate sealing ring 26 in the circumferential direction. 8
There is no need to take measures such as minimizing the parallelism of the lines, which is effective in saving manufacturing man-hours and materials.

FIGS. 6 and 7 show a method for determining whether the mechanical seal according to the present invention exhibits the desired effect through experiments.

That is, in this experiment, m=7 mm, n=2.
A conventional mechanical seal has an intermediate sealing ring with dimensions of 5 mm, P = 3, 5 mm, and q = 12 mm, and a mechanical seal having the same external shape as this intermediate seal ring and a t = 2 mm on its inner wall surface.
For the mechanical seal according to the present invention having an intermediate sealing ring 18 provided with a groove A of ρ-1.4 mm, the amount of leakage and frictional resistance at the seal surface were compared and measured.

According to the results shown in Fig. 6, in the conventional mechanical seal, the frictional force acting on the sealing surface does not increase as indicated by the polygonal line F despite the increase in hydraulic pressure, and the frictional force acting on the seal surface does not increase as indicated by the polygonal line C
As shown, when the liquid pressure exceeds 4 mg/cm2, the amount of leakage at the seal surface increases.

On the other hand, in the mechanical seal according to the present invention, as shown by the broken line, the frictional force increases linearly as the hydraulic pressure increases.

From this, it can be seen that the seal surfaces 6 and 7 of the intermediate seal ring 18 maintain parallelism, and the plane sliding state of the seal surfaces is maintained.

Further, as shown by the polygonal line d, in the mechanical seal according to the present invention, even if a hydraulic pressure of 80 kg/Cm2 is generated, the amount of leakage does not increase at all.

Furthermore, according to the results shown in FIG. 7, in the conventional mechanical seal, the friction coefficient of the sealing surface decreases significantly as the hydraulic pressure increases, as indicated by the polygonal line e.

This shows that the sealing surface is extremely distorted by the hydraulic pressure.

In contrast, in the mechanical seal according to the present invention, the coefficient of friction is constant regardless of the hydraulic pressure, as indicated by the polygonal line f.

Therefore, it can be seen that the sealing surface of the mechanical seal according to the present invention maintains parallelism despite an increase in hydraulic pressure.

As detailed above, according to the present invention, the deformation of the intermediate sealing ring caused by hydraulic pressure can be balanced and the parallelism of both sealing surfaces can be maintained. The sealing performance of the carbon graphite intermediate sealing ring with a T-shaped cross section has been dramatically improved, and since the grooves are provided only on the inner wall surface, which is the non-wetted surface, the structure has been improved. It is simple and easy to implement, and provides excellent practical effects.

[Brief explanation of drawings]

FIG. 1 is a front view showing a conventional example, FIG. 2 is an explanatory view showing a deformed state of the intermediate sealing ring in the conventional example, FIG. 3 is a sectional view showing the shape of the intermediate sealing ring in another conventional example, and FIG. The figure is a front view showing an embodiment of the present invention, FIG. 5 is a dimensional explanatory diagram of an intermediate sealing ring, and FIGS. 6 and 7 are explanatory diagrams showing experimental results. 13... Rotating sealing ring, 14... Stationary sealing ring, 18... Intermediate sealing ring, A... Groove.

Claims (1)

[Claims for Utility Model Registration] An intermediate sealing ring made of carbon graphite having a T-shaped cross section and having sealing surfaces on both sides is provided between a rotating sealing ring and a stationary sealing ring so that hydraulic pressure does not act on its inner wall surface. In this mechanical seal, a groove having a U-shaped cross section is provided only on the inner wall surface, which is the non-liquid contact surface, of the intermediate sealing ring, and the radius of curvature ρ of the arcuate groove bottom of this groove and the groove depth t are The relationship between the width P of the sealing surface and its protrusion amount n is such that: dan=ρ and deafness=1.
Mechanical seal with jn characteristics.