JPH11351407A - Shaft seal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To strictly control the leakage of a fluid to be sealed to the air side and prevent the contamination of the fluid to be sealed of the fluid intervened between both the mechanical seals or the like in a shaft seal device provided with mechanical seals in the two steps in the axial direction. SOLUTION: A first mechanical seal 40 at the side of a fluid to be sealed (B) has a contact type seal structure, while a second mechanical seal 50 at the air side (A) has a non-contact type seal structure. A high pressure seal gas having just a pressure differential of 2 kg/cm<2> or less than the pressure of the fluid to be sealed (B) is supplied to an intermediate chamber 20a partitioned between the side of the fluid to be sealed (B) and the air side (A) by both the mechanical seals 40, 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaft sealing technique for sealing the circumference of a rotating shaft, and more particularly to a shaft sealing device in which mechanical seals are arranged in two stages in the axial direction.

[0002]

2. Description of the Related Art In a shaft sealing technique, when it is necessary to strictly control leakage of a fluid to be sealed to the atmosphere side, conventionally, as schematically shown in FIG.
M ₁ , Sealing structure which is adapted to isolate a sealed fluid B and the atmosphere A side by interposing the intermediate liquid O oil such as the space between them and arranged in two stages M ₂ in the axial direction is employed.

In addition, mechanical seals M ₁ , M ₂ is,
A non-contact type seal having a gap between the seal surfaces of the rotating ring and the stationary ring is used as the mechanical seal M ₁ , There is also known a shaft sealing structure in which a harmless seal gas SG such as N ₂ gas having a higher pressure than the fluid B to be sealed is interposed between M ₂ to isolate the fluid B side to be sealed from the atmosphere A side. Have been.

[0004]

The following problems are pointed out in the shaft sealing device according to the prior art. First, in the case where the intermediate liquid O such as oil is interposed between the mechanical seals M ₁ and M ₂ arranged in two stages in the axial direction, a pump for circulating and supplying the intermediate liquid O, a fixed amount of the intermediate liquid O , And various accumulators such as an accumulator for adjusting the pulsation of the pressure of the intermediate liquid O by the pump are required, and maintenance management is complicated. There is also a possibility that the sealed fluid B is contaminated by intermediate liquid O from leaking from the mechanical seal M ₁ to flight.

The mechanical seal M ₁ , The M ₂ as a non-contact seal structure, those interposing a harmless seal gas SG, such as high-pressure N ₂ gas than sealed fluid B therebetween, machine space from between the sealing surfaces of the non-contact mechanical seal M ₁ Since the sealing gas SG leaks, for example, in the case of a shaft sealing device for a pump, cavitation occurs due to bubbles of the sealing gas mixed in the fluid B to be sealed, and the pump efficiency may be significantly reduced. For this reason, it is necessary to perform maintenance management such as periodically removing the leaked gas accumulated in the pump.

Also, in the unlikely event that the mechanical seal M ₁ , When the pressure of the seal gas SG is supplied between M ₂ becomes lower than the pressure of the sealed fluid B, damaged sealing surface of the mechanical seal M ₁ which has been held in a non-contact state by the pressure balance becomes in contact , The fluid B to be sealed is the mechanical seal M ₁ , It flows between M _2, further mechanical seal
There is a risk of leakage to the atmosphere A side from between the sealing surface of the non-contact M _2.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a main technical problem thereof is that a shaft sealing device provided with two stages of mechanical seals in the axial direction has a seal to the atmosphere side. A shaft seal structure that satisfies the requirement to strictly regulate the leakage of the target fluid and effectively prevents contamination of the fluid to be sealed due to leakage of the fluid interposed between the two mechanical seals and damage to the sealing surface of the mechanical seal Is to do.

[0008]

Means for Solving the Problems The technical problems described above are:
This can be effectively solved by the present invention. That is, in the shaft sealing device according to the present invention, a mechanical seal is disposed in two stages in the axial direction between the housing and the rotating shaft inserted through the inner periphery of the housing, and the mechanical seal is disposed on the side of the fluid to be sealed among the mechanical seals. The first mechanical seal has a contact-type seal structure in which the sealing surfaces of the rotating ring and the stationary ring are closely slid with each other. Of the two mechanical seals, the second mechanical seal on the atmosphere side is the sealing of the rotating ring and the stationary ring. A non-contact type seal structure having a gap between the surfaces, a sealing gas having a higher pressure than the sealing target fluid is supplied to an intermediate chamber defined between the sealing target fluid side and the atmosphere side by the two mechanical seals. Supply. In this case, more preferably, the pressure difference between the seal gas supplied to the intermediate chamber and the fluid to be sealed is 2 kg / cm ² or less.

According to the shaft sealing device of the present invention, since the first mechanical seal on the fluid side to be sealed has a contact-type sealing structure, it is supplied to the intermediate chamber between the second mechanical seal on the atmosphere side. Leakage of the seal gas into the fluid to be sealed is effectively suppressed. Even if the supply pressure of the seal gas to the intermediate chamber becomes lower than the pressure of the fluid to be sealed, the first mechanical seal has a contact-type seal structure, so that the fluid to be sealed passes through the intermediate chamber to the atmosphere. There is no leakage to the side, and there is no damage to the sealing surface due to pressure drop in the intermediate chamber as in the non-contact type sealing structure.

Although the first mechanical seal has a contact-type seal structure as described above, the gas pressure in the intermediate chamber is higher than the fluid to be sealed. Part of the lubricating liquid film is difficult to intervene,
For this reason, it is slid in a substantially dry state. However, by reducing the pressure difference between the gas pressure of the intermediate chamber and the fluid to be sealed, for example, by reducing this pressure difference to 2 kg / cm ² or less, it is possible to significantly reduce the sliding load on the sealed sliding surface.
Further, by using a sliding material impregnated with fluorine oil on one of the sealing surfaces, it is possible to improve sliding characteristics in a dry state.

Since the second mechanical seal on the atmosphere side has a non-contact type seal structure, the sealing gas supplied to the intermediate chamber is supplied to the atmosphere through the gap between the sealing surfaces of the rotating ring and the stationary ring in the second mechanical seal. Released inside. Harmless gases such as air or N ₂ gas is used as the sealing gas for this.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of a shaft sealing device according to the present invention will be described with reference to FIG.

In this figure, reference numeral 10 denotes an equipment main body housing, and reference numeral 20 denotes this equipment main body housing 10.
A shaft seal housing consisting of two annular housing members 21 and 22 axially connected by bolts 25 and nuts 26 in an air-tight manner to each other via O-rings 23 and 24 at the ends of the shaft seal, reference numeral Reference numeral 30 denotes a rotating shaft inserted through the inner periphery of the shaft sealing portion housing 20 and the device main body housing 10. In the inner peripheral portions of the annular housing members 21 and 22 in the shaft seal housing 20, annular concave portions 21a and 22a axially facing each other are formed. First and second rotating rings 60 are shared between the annular concave portions 21a and 22a and the rotating shaft 30 in order to seal between the fluid B to be sealed inside the machine and the atmosphere A outside the machine. Mechanical seals 40 and 50 are arranged in two stages in the axial direction.

The first mechanical seal 40 on the fluid B side to be sealed is housed in the annular recess 21a of the annular housing member 21 of the shaft seal housing 20 via the packing 42 in an airtight and axially movable state. And the stationary ring 41 is attached to the annular housing member 2.
1 (shaft seal housing 2); a dowel pin 43 for preventing rotation; and a stationary ring 41 disposed at equal intervals in the circumferential direction within the annular recess 21a and pushing the stationary ring 41 from the annular recess 21a toward the second mechanical seal 50. And a plurality of coil springs (not shown) for urging. Reference numeral 44 denotes a snap ring that regulates the amount of movement of the stationary ring 41 toward the second mechanical seal 50 by the coil spring.

On the other hand, the mechanical seal 50 on the atmosphere A side
Is engaged in an axially movable engagement groove 22b formed in the annular recess 22a of the annular housing member 22 of the shaft seal housing 20 so as to be movable in the axial direction. The stationary ring 51 is prevented from rotating, and is arranged in the annular concave portion 22a at equal intervals in the circumferential direction so that the stationary ring 51 is pushed out from the annular concave portion 22a to the first mechanical seal 40 side via a retainer 52. A plurality of coil springs 53 to be urged and a packing 54 sandwiched between the stationary ring 51 and the retainer 52 to maintain airtightness between the stationary ring 51 and the annular housing member 22 are provided. Note that reference numeral 5
Reference numeral 5 denotes a snap ring that regulates the amount of movement of the stationary ring 51 toward the first mechanical seal 40 by the coil spring 53.

A sleeve 31 extending to a position corresponding to the inner periphery of the shaft seal housing 20 is provided on the outer peripheral surface of the rotary shaft 30 and is fixed by a set screw (not shown). The rotating ring 60 is provided with the first mechanical seal 40.
Of the stationary ring 41 of the second mechanical seal 50
1 and an inner peripheral portion of the sleeve 31.
The collar 3 is externally fitted in contact with the outer peripheral step portion 31 a of the sleeve 3, and attached to the outer end of the sleeve 31 with a bolt 32.
3 fixed. The sleeve 31 and the rotating shaft 3
The airtightness is maintained by the O-ring 34 between 0 and the O-ring 35 between the rotary ring 60 and the sleeve 31.

As the material of the rotating ring 60, for example, a SiC sliding material is used, and for the stationary ring 41 of the first mechanical seal 40, which is in sliding contact with the rotating ring 60, for example, a carbon sliding material impregnated with fluorine oil is used. Can be

The stationary ring 41 of the first mechanical seal 40 has a smooth end face of a nose portion 41 a formed continuously in the circumferential direction at an end facing the second mechanical seal 50 side. One end face 61 facing the inside of the aircraft
Is closely related to In other words, the first mechanical seal 40 has a contact-type shaft sealing structure in which the stationary ring 41 and the rotating ring 60 slide tightly with an appropriate surface pressure to achieve a shaft sealing function.

The stationary ring 51 of the second mechanical seal 50 has an end face 51 a facing the first mechanical seal 40 side and a second end face 62 facing the outside of the rotary ring 60.
In other words, the second mechanical seal 50 has a non-contact type shaft sealing structure.

The annular housing member 22 of the shaft seal housing 20 has a circumferentially continuous intermediate portion defined by annular concave portions 21a and 22a and a seal portion formed by the first and second mechanical seals 40 and 50. A gas supply hole 22b is formed toward the chamber 20a. That is, the intermediate chamber 20a to supply harmless seal gas SG, such as air or N ₂ gas of a high pressure (differential pressure 2 kg / cm ² or less) than the pressure of the sealed fluid B through the gas supply hole 22b It has become.

On the other hand, a required number of radial or helical dynamic pressure grooves 6 are provided on an end face 62 of the rotating ring 60 facing the stationary ring 51.
2a are formed, and the dynamic pressure generated in the dynamic pressure groove 62a with the rotation of the rotary ring 60 causes the second mechanical seal 50 to move the stationary ring 51 and the rotary ring 60 to each other through a minute gap. It is maintained in a non-contact state. Therefore, the seal gas SG such as air or N ₂ continuously supplied to the intermediate chamber 20 a through the gas supply holes 22 b is supplied to the outside air A through the gap of the non-contact seal surface S ₂ in the second mechanical seal 50. flows out to the middle, by the orifice effect in a non-contact seal surface S ₂ of the gap at this time, the intermediate chamber 2
0a is maintained in a high pressure state by a pressure difference of ² kg / cm ² or less than the fluid B to be sealed.

In the above configuration, when the rotating shaft 30 rotates, the rotating force is transmitted to the rotating ring 60 via the sleeve 31, that is, the rotating ring 60 rotates integrally with the rotating shaft 30. Sealed fluid B of flight, although reaches to the inner peripheral space of the stationary ring 41 in the first mechanical seal 40, the still ring 41 forms a seal sliding surface S ₁ and the rotary ring 60, also Stationary ring 41 and annular housing member 21
And the gas pressure in the intermediate chamber 20a is higher than that of the fluid B to be sealed.
Leakage of the fluid B to be sealed into the intermediate chamber 20a is effectively prevented. In addition, an O-ring 35 is interposed between the rotating ring 60 and the sleeve 31 and an O-ring 34 is interposed between the rotating shaft 30 and the sleeve 31, so that the O-ring 35 is interposed between the rotating ring 60 and the sleeve 31. Also, the fluid B to be sealed does not leak to the atmosphere A from between the rotary shaft 30 and the sleeve 31.

Since the pressure of the seal gas SG in the intermediate chamber 20a is higher than the pressure of the fluid B to be sealed, the sealing sliding surface S1 of the _first mechanical seal 40 is in a dry state, that is, the pressure of the fluid B to be sealed. The slide is performed in a state in which liquid lubrication due to intervention is difficult to perform. However, as described above, the difference between the gas pressure in the intermediate chamber 20a and the pressure of the fluid B to be sealed is small, and the first mechanical seal 40 has a pressure-balanced seal structure, and is only operated by the biasing force of the coil spring. since the surface pressure of the sealing sliding surface S ₁ is given, small sliding load, further, the stationary ring 41 made of carbon sliding material impregnated with rotary ring 60 and the fluorine oil consisting of SiC sliding material since good sliding properties by the combination can be obtained, it is possible to effectively suppress wear and damage of the sealing sliding surface S _1.

Although the gas pressure of the intermediate chamber 20a is higher than that of the fluid B to be sealed, the pressure difference is as small as ² kg / cm ² or less, and the first mechanical seal 40 has a contact type seal structure. Therefore, the seal gas SG supplied to the intermediate chamber 20a hardly leaks into the fluid B to be sealed in the machine. For this reason, the occurrence of cavitation due to the incorporation of air bubbles into the fluid B to be sealed is prevented, and it is not necessary to perform maintenance such as periodically removing leakage gas (seal gas SG) accumulated in the apparatus.

Further, even if the pressure of the seal gas SG supplied to the intermediate chamber 20a is lower than the pressure of the fluid B to be sealed,
First for the mechanical seal 40 is a contact-type seal structure to achieve the shaft sealing function in a sealed sliding surface S _1, a non-in the second mechanical seal 50 from which sealed fluid B is further flows into the intermediate chamber 20a nor that via the gap between the contact seal surface S ₂ leaks outside to the atmosphere a in. Moreover, there is no need to circulate the seal gas SG with the outside, and therefore, there is no need for auxiliary equipment such as a pump and an accumulator as in the case where oil or the like is pressurized and circulated from the outside to the intermediate chamber 20a.

The first and second mechanical seals 4
Since 0 and 50 have a structure in which one rotating ring 60 is shared, the mounting length in the axial direction is short.
0 does not increase the size of the shaft sealing device.

[0027]

As described above, according to the shaft sealing device of the present invention, the following effects are realized. First, since the first mechanical seal on the fluid to be sealed has a contact-type seal structure, it is possible to effectively suppress leakage of the seal gas supplied to the intermediate chamber into the fluid to be sealed, and This prevents cavitation of the attached pump or the like and contamination of the fluid to be sealed, which is a sealing target. Further, since only the seal gas needs to be supplied to the intermediate chamber, external equipment such as a pressurized circulation device is not required, and maintenance of the equipment is easy.

Even if the pressure of the seal gas becomes lower than the pressure of the fluid to be sealed, the first mechanical seal on the fluid side to be sealed has a contact-type sealing structure, so that the fluid to be sealed passes through the intermediate chamber to the atmosphere side. No leakage or damage to the sealing surface. In addition, since the pressure difference between the fluid to be sealed and the seal gas is as small as ² kg / cm ² or less, the sliding load on the sealing sliding surface of the first mechanical seal is small, and it is good despite the fact that liquid lubrication is not performed. It is possible to maintain slidability.

[Brief description of the drawings]

FIG. 1 is a half sectional view showing a preferred embodiment of a shaft sealing device according to the present invention by cutting along a plane passing through an axis.

FIG. 2 is an explanatory view schematically showing a shaft sealing device according to a conventional technique.

[Explanation of symbols]

Reference Signs List 20 shaft seal housing 20a intermediate chamber 30 rotating shaft 40 first mechanical seal 50 second mechanical seal 60 rotating ring A atmosphere B fluid to be sealed S ₁ sealed sliding surface S ₂ non-contact sealing surface SG sealing gas

Claims (3)

[Claims] 1. A mechanical seal is disposed in two stages in an axial direction between a housing and a rotating shaft inserted through an inner periphery of the housing, and a first mechanical seal of the two mechanical seals on a fluid side to be sealed is provided. Is a contact-type seal structure in which the sealing surfaces of the rotating ring and the stationary ring are slid in close contact with each other. Of the two mechanical seals, the second mechanical seal on the atmosphere side has a gap between the sealing surfaces of the rotating ring and the stationary ring. A non-contact type sealing structure, wherein a seal gas having a higher pressure than the sealing target fluid is supplied to an intermediate chamber defined between the sealing target fluid and the atmosphere side by the two mechanical seals. Shaft sealing device. 2. The shaft sealing device according to claim 1, wherein the pressure difference between the sealing gas supplied to the intermediate chamber and the fluid to be sealed is 2 kg / cm ² or less. 3. The shaft sealing device according to claim 1, wherein the first mechanical seal uses a sliding material in which one sealing surface is impregnated with fluorine oil.