JPS6231775A - Shaft seal device - Google Patents

Abstract

PURPOSE:To avoid the need of a special feeding device for pressure-increasing the sealed liquid by forming a spiral groove which engulfs the liquid on the low-pressure side to the high-pressure side by the revolution of a rotary ring, onto a slidable surface, so as to be closed on the high pressure side. CONSTITUTION:The sealing surface 21 of a static ring 2 consists of a spiral groove part 9 consisting of flat top parts 9a and spiral grooves 9b which are alternately arranged and a flat part 10 which is positioned onto the outer periphery of the spiral groove part 9 and on the same plane to the top part 9a. The center side of the spiral groove 9b is bored, and the outside part is closed. When a rotary shaft 3 revolves, liquid is engulfed from the opened edge on the center side of the spiral groove 9b by the pumping action, and a dynamic pressure is generated towards the outer periphery, and pressure is increased. At the terminal edge part of the spiral grooves 9b, the pressure a little larger than the pressure of the sealing fluid in a space H is generated, and a liquid film is formed between the sealing surfaces 11 and 21.

Description

[Detailed Description of the Invention] [Objective of the Invention] "Industrial Application Field" The present invention is a shaft sealing device for a rotating shaft, in particular, an end face seal such as a mechanical seal, and a sealing device for sealing a rotary shaft such as a toxic or flammable gas or liquid. This invention relates to a shaft sealing device for fluid that must never leak.

"Prior Art" An example of a conventional device of this type is shown in FIG. 5, which is a longitudinal sectional view. In the figure, a space H inside the casing is sealed with a high-pressure sealing fluid, and A is a space outside the casing where there is an atmosphere, and the sealing fluid in the space H flows out to the atmosphere side space A. The seal rTJ of the rotating ring /, which is integrally or fixed to the rotating shaft 3, and the sealing surface 2/ of the stationary ring slide in a state of fluid lubrication or boundary lubrication. ing.

The stationary ring is pushed in the axial direction by a spring 5 against the casing rod, but is locked to the casing rod by a rotation stopper (not shown) so that it does not rotate. Further, an O-ring t is provided where the stationary ring λ slides on the casing bow and slides in the axial direction, separating the space R from the space. The space A and the atmosphere side space A are covered with a floating ring seal 6 on the end face of the cover/λ that is sealed and fixed to the casing.
is pressed into contact with a spring/jJ disposed in the axial direction between the casing ring and the floating ring seal 6.

Pressure fluid of p+Δp (Δp is several kg/am2) with respect to the pressure p of the sealing fluid in the space H is supplied to the space through the supply hole, and the sealing surface of the rotating ring/ and the stationary ring co Due to the end seal effect between 1 and 2, the pressure difference of Δp prevents the liquid in the space from leaking into space 2, and the sliding surface between the floating ring seal 6 and the rotating shaft 3 prevents the liquid in the space from leaking into the atmosphere. It suppresses leakage to people in the side space.

``Problems to be Solved by the Invention'' When sealing a high-pressure fluid, this device requires a special supply device to increase the pressure of the liquid to be sealed. ■It is necessary to always control the differential pressure between the sealing fluid and the liquid that confines it. ■Since it is a contact type seal, if the sealing conditions are strict, it will inevitably lack reliability and have a short lifespan. (2) The space is under high pressure, and if liquid leaks from the seal 6, it becomes atmospheric pressure, resulting in a large loss. I have such problems.

An object of the present invention is to solve the above-mentioned problems in a shaft sealing device configured to seal a rotating shaft with an end face seal, and to provide a shaft sealing device that is highly reliable and does not require a special pressure boosting device. do.

[Structure of the invention]

``Means for Solving the Problems'' The present invention is characterized in that the sliding surfaces of a rotating ring that rotates together with a rotating shaft and a stationary ring that is attached to a casing are pressed and slide, and the sliding surfaces seal the ring. In this shaft sealing device, a spiral groove is provided on one of the sliding surfaces so that the liquid on the low pressure side is drawn in toward the high pressure side by the rotation of a rotary ring so as to end on the high pressure side.

"Operation" When the rotating shaft rotates, the rotating ring rotates, and due to the effect of the spiral groove, the liquid on the low pressure side moves to the high pressure side where the spiral groove stops, increasing the pressure and generating dynamic pressure. This pressurized liquid seals the sealing fluid on the high pressure side.

"Example" Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view. Similar to the conventional example shown in Figure 3, the space ■ inside the casing is filled with high-pressure sealing fluid.
A is the atmosphere side space on the outside side of the casing. Although the sealed liquid is supplied to the space, the pressure may be equal to or lower than the pressure of the sealed fluid in the space (2), and may be equal to atmospheric pressure. Further, the space may just be filled with a sealing liquid.

Sealing surface of rotating ring l integrally or fixed to rotating shaft 3/
/ and the sealing surface / of the stationary ring are sliding surfaces that slide through the liquid film. There is a spring in the axial direction between the stationary ringco and the casing side! is arranged, and the stationary ring -
is pushed in the axial direction toward the rotating ring l, or is locked to the casing side with a rotation stopper (not shown) so that it does not rotate. In addition, an 0 ring t is provided at the part where the stationary ring is slidably fitted to the casing side, separating it into a space ① and a space.

The space A and the atmosphere side space A are arranged in the axial direction between the casing q and the floating ring seal 6 on the end face of the cover l-, which is sealed and fixed to the casing side by a floating ring seal 6 that is slidably fitted on the rotating shaft 3. It is sealed and shut off by being pressed by the spring IS.

As shown in the first front view, the sealing surface of the stationary ring includes a spiral groove portion 9 in which a flat top portion 9a and a spiral groove 9b are arranged alternately, and a flat portion 10 located on the outside thereof and flush with the top portion 9a. Become. The spiral groove 9b extends through the center and stops at the outer circumference.

The hole is a hole for supplying liquid used for sealing to a space provided on the casing side, and the space is filled with low pressure liquid.

The rotating direction of the rotating shaft 3 is counterclockwise in FIG. 1, and due to the pumping action, the spiral groove tb draws in the liquid from the open end on the center side, and dynamic pressure is generated and increased toward the outer periphery, and the spiral groove tb Terminal part (outermost periphery) of groove 9b
In this case, a pressure slightly higher than that of the sealing fluid in space H is generated, and a liquid film is formed between the sealing surfaces // and C1.
Fluid lubrication is provided between both sealing surfaces //, -/.

The maximum pressure of this fluid lubrication liquid film is set so that the sealing fluid in the space H does not enter, or a small amount of liquid on the space side leaks to the space H side. This is particularly effective when the sealing fluid on the space H side is harmful, or even if it is not harmful in itself, it will cause serious problems if it leaks.

If the load on the sealing surface //, ko is W, and the pressure at the end of the spiral groove q1) is Pg, then if a fluid film is completely formed on the sealing surface //, ko/, then W=IL pg...・■
becomes. a is a coefficient determined by the shape of the spiral groove 9b, the number of grooves, the groove depth, etc. On the other hand, the pressing load W on the sealing surfaces // and ko/ is the sealing pressure p and the spring! Due to the spring load F, W=S-p-)-F...@. S is the rotating ring of the stationary ring co due to the pressure of the sealing fluid in the space H/
π(r2-rl) where -r2 = outer diameter of the sealing surface //, 2/; r1 = diameter of the sliding portion of the stationary ring and the casing q. From the equations and @, aPg = 8-1)+1'.

If we decide S so that S = a =: k, we get
IP==k(1)g-p), and the differential pressure Δp=(pg-p) at the flat portion 10 of the sealing surface will always be constant regardless of the sealing pressure if the spring load F is determined. Also, the thickness of the fluid film on the sealing surfaces //, -/ should be spiral grooved to be as thin as possible. 1) The groove shape and groove depth shall be determined. Therefore, the sealing surface //, λl is constantly raised to a higher pressure by Δp (several Kff/67rL2) with respect to the pressure p of the sealing fluid due to the pumping action of the spiral groove 9b, thereby sealing the sealing fluid and sealing surface //, 21 This is to reduce leakage by minimizing the gap between the two. Note that the value of Δp does not depend on the rotational speed, sealing pressure, or type of sealed liquid, but is determined only by the magnitude of the spring load of the spring.

The liquid to be sealed in the space should be oil, water, or other liquid if the sealing fluid is a gas, or another safe clean liquid if it is a liquid. In particular, in the latter case, it is desirable to seal the liquid containing foreign matter with a clean liquid of the same kind. In addition, if the sealed fluid in space H is a gas, the sealed liquid in the space H side where the sealed fluid leaks can be easily separated, which is very effective. It is very effective in cases where it does not matter.

The liquid contained in the space may be at atmospheric pressure and may be supplied by a low-head pump, or if the pump uses this sealing device, the fluid itself at low pressure may be introduced on the suction side of the pump. It's okay. Furthermore, since this liquid is under low pressure, leakage can be limited as much as possible with a simple seal such as the floating ring seal 6. The seal on the atmospheric pressure side may, of course, be a mechanical seal or other seal, and is selected depending on the situation. Although the spiral groove qb was on the stationary ring side, it may also be on the rotating ring side. In this embodiment, the depth of the spiral groove 9b is 3 to 50 μm, and the thickness of the liquid film on the sliding surface is about 1 to 3 μm.

FIG. 3 is a longitudinal sectional view of another embodiment of the invention. While the flow in the spiral groove portion D in the previous embodiment was an outward flow, in the embodiment shown in FIG. 3, it was an inward flow.

A sealing fluid exists in the space H, a liquid for sealing the sealing fluid exists in the space, and the atmosphere exists in the space A.

The attachment relationship of the stationary ring to the casing and the relationship of the rotating ring to the rotating shaft 3 are the same as in the previous embodiment. A space is formed on the rotating ring side, and a cover/- is sealed and fixed to the member housing 1 that is sealed and fixed to the casing y.
The floating ring seal 6 is pressed against the rotating shaft 3, and a rotating seal is formed between the floating link seal 6 and the rotating shaft 3.

FIG. 9 is a front view of the stationary ring λ. The spiral groove 9b provided in the stationary ring goes through the outer periphery and stops at the center.

When the rotating shaft J rotates clockwise in FIG. 9, the liquid in the space is drawn into the spiral groove 9b, and dynamic pressure is generated on the center side. This pressure creates a pressure slightly higher than the pressure of the sealing fluid in the space H on the sealing surface // and the center side of the col, and sealing is performed.

Embodiment ζ Is this a spiral? The depth of JLqb is, for example, 3 to go μm, depending on the viscosity of the sealed liquid, so as to generate sufficient dynamic pressure and form a fluid film as thin as possible. The thickness of the liquid film between the sliding surfaces is about /-Jμm.

The rotating ring/stationary ring in each embodiment is made of a hard material, especially ceramics (silicon carbide SiO or silicon nitride 81, N4 is 4 years old) on the side where the grooves are provided, and the mating sliding member is made of alumina. Ceramics, cemented carbide, stainless steel, high lead bronze, ordinary cast iron, carbon, or the same material as the side on which the spiral groove 9b is provided are suitable. The sliding surfaces of the rotating ring/stationary ring are mirror-finished, and the sliding motion is completely fluid** due to the dynamic pressure effect of the spiral groove, so experiments have shown that the coefficient of friction is as low as 0.003, making for low cooling. There is almost no need for In addition, the part provided with the spiral groove is shown on the right above, and the member provided with the spiral groove is thin-walled disc-shaped, and the stationary ring λ
Alternatively, it may be bonded to the rotating ring l, or if this mating member is also made of ceramics, it may be bonded in the form of a plate.

〔Effect of the invention〕

The present invention provides a shaft sealing device in which the sliding surfaces of a rotating ring that rotates together with a rotating shaft and a stationary ring that is attached to a casing are pressed and slide, and the sliding surfaces provide a seal. The shaft seal device is equipped with a spiral groove on the sliding surface of the rotary ring that draws the liquid from the low-pressure side toward the high-pressure side as it rotates, stopping at the high-pressure side. ■ A special supply device that increases the pressure of the sealed liquid. does not require.

■ No device is required to control the pressure difference between the sealed liquid and the sealed fluid.

■ The sealing surface is non-contact, so it is highly reliable and has a long life.

■ There is extremely little leakage of the sealed liquid to the outside, and there is little loss.

The following effects occurred.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 1 is a front view of the stationary ring of FIG. 1, and FIG. 3 is a longitudinal sectional view of another embodiment.
4 is a front view of the stationary ring shown in FIG. 3, and FIG. 3 is a longitudinal sectional view of the conventional example. /...Rotating ring Co...Stationary ring J...Rotating shaft
Da...Casing IIl...Materials...Spring 6.
・Floating ring seal 70. Supply hole to, 0
Ring 90. Spiral groove 9a...Top vb...
・Spiral groove 10・Self-flat part 1i--Sealing surface/Co...Cover 75...Spring Col...Sealing surface A,
H, L... Space. Patent applicant Ebara Research Institute, Ltd. Ebara Corporation

Claims (1)

[Claims] 1. In a shaft sealing device in which the sliding surfaces of a rotating ring that rotates with the rotating shaft and a stationary ring attached to the casing side are pressed and slide, and the sliding surfaces create a seal, when either sliding A shaft sealing device in which a spiral groove is provided on the dynamic surface of the rotating ring to draw liquid from the low pressure side toward the high pressure side so that it ends on the high pressure side.