JP4833882B2 - Screw fluid machine - Google Patents

Description

  The present invention relates to a screw fluid machine.

  In a screw fluid machine such as a screw compressor that compresses a target gas with a male and female screw rotor housed in the rotor chamber, and a screw expander that rotates a screw rotor that expands and gasifies the target gas in the rotor chamber, A shaft seal structure is provided between the screw rotor of the rotor shaft and the bearing in order to seal the target gas in the system or prevent external air from being mixed into the target gas.

  As described in Patent Document 1, in the conventional screw compressor, a lip seal is used as a suction side shaft seal device, and a mechanical seal is used as a discharge side shaft seal device.

The lip seal is an inexpensive and space-saving shaft seal device, but generally the maximum pressure that can be sealed is about 0.3 kgf / cm ² . For this reason, the lip seal can be used only for the shaft seal on the suction side of the low pressure because the shaft seal may be insufficient on the discharge side where the pressure is high or the durability may be significantly reduced. On the other hand, the mechanical seal is capable of high-pressure shaft sealing, but has a problem that it is very expensive and requires a large space for installation.
JP 2000-45948 A

  In view of the above problems, an object of the present invention is to provide a screw fluid machine having a shaft seal structure that is inexpensive and space-saving on the high-pressure side of a rotor shaft.

In order to solve the above-described problems, according to the present invention, in the screw fluid machine that compresses the target gas or converts the expansion force of the target gas into a rotational force by a screw rotor that engages the male and female accommodated in the rotor chamber, A non-contact seal between the rotor and a bearing on the high-pressure side of the rotor shaft of the screw rotor, a sleeve fitted on the outer periphery of the rotor shaft between the non-contact seal and the bearing, and an outer periphery of the sleeve A lip seal that is in sliding contact, a communication path that communicates a space between the non-contact seal and the lip seal to a low-pressure space that is equal to or lower than a working pressure of the lip seal, and the gap between the screw rotor and the non-contact seal. It is assumed that a shaft seal fluid flow path for supplying a shaft seal fluid to the rotor shaft is provided.

According to this configuration, the target gas and lubricating fluid (lubricating oil, sealing water, etc.) are substantially sealed in the rotor chamber by the non-contact seal, and the target gas and lubricating fluid slightly leaking from the non-contact seal are completely sealed with the lip seal. Seal it to prevent it from entering the bearing. Furthermore, by providing the communication path, the target gas and the lubricating fluid that slightly leak into the space between the non-contact seal and the lip seal are discharged from the screw rotor side to the low-pressure space. This prevents the pressure from rising due to the leaked target gas, so that excessive pressure is not applied to the lip seal, the sealing performance of the lip seal is impaired, and the lip seal can be worn out in a short time. Absent. Further, since this shaft seal structure is constituted by a non-contact seal and a lip seal, it is inexpensive and requires a small installation space. Further, since the lip seal seals the rotor shaft by not sliding directly against the rotor shaft but by sliding contact with the sleeve, the wear is less and the life is longer. Further, the shaft sealing fluid increases the shaft sealing effect of the non-contact seal, and the efficiency of the screw fluid machine can be improved.

  Moreover, the screw fluid machine of this invention WHEREIN: The said low pressure space may be the suction flow path of the said object gas, or the low pressure part of the said rotor chamber.

  According to this configuration, the target gas and the lubricating fluid leaked from the non-contact seal can be returned to the rotor chamber, so that they can be recovered and reused without being discharged out of the system. As a result, loss of the target gas and lubricating fluid can be prevented, and there is no waste.

  In the screw fluid machine of the present invention, an open flow path that communicates the space between the lip seal and the bearing to the outside may be provided.

  According to this configuration, even when the lubricating fluid leaks to the bearing side due to wear of the lip seal or the like, the leaked lubricating fluid is discharged to the outside, so that the lubricating fluid flows into the bearing and causes a problem. Can be prevented.

  In the screw fluid machine of the present invention, a spiral groove may be formed in a contact portion of the lip seal with respect to the rotor shaft.

  According to this configuration, the shaft sealing ability of the lip seal is increased.

  As described above, the shaft seal structure on the discharge side of the rotor shaft of the screw fluid machine of the present invention substantially seals the high discharge pressure of the screw rotor with a non-contact seal. Further, the target gas or lubricating fluid that slightly leaks from the non-contact seal in the communication path is discharged to the low pressure portion to prevent the pressure on the bearing side of the non-contact seal from rising, so that the target gas or lubricating fluid is It is possible to completely seal with a lip seal so as not to flow into. For this reason, the screw fluid machine of the present invention has an inexpensive and space-saving shaft seal structure. In addition, by bringing the lip seal into sliding contact with the sleeve fitted to the rotor shaft, the wear of the lip seal can be reduced and the life can be extended.

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1 shows a screw compressor 1 according to a reference example of the present invention. The screw compressor 1 uses a pair of male and female screw rotors 4 housed in a rotor chamber 3 of a housing 2 to compress a target gas (for example, air or refrigerant) containing a lubricating fluid (lubricating oil or water). It is a screw fluid machine.

  The housing 2 includes a suction flow path 5 for supplying a target gas to be compressed to the rotor chamber 3, a discharge flow path 6 for discharging the target gas compressed by the screw rotor 4 in the rotor chamber 3, and the screw rotor 4. Bearing shaft sealing spaces 8 and 9 are provided for installing a structure for supporting and sealing the rotor shaft 7 on the suction side (low pressure side) and the discharge side (high pressure side), respectively.

  The rotor shaft 7 is rotatable by a roller bearing 10 installed in the bearing shaft sealed space 8 on the suction side and two ball bearings 11 installed in the bearing shaft sealed space 9 on the discharge side (high pressure side). It is supported, extends through the bearing shaft sealing space 9 on the suction side, and is connected to a motor (not shown).

  A lip seal 12 is installed on the motor side of the roller bearing 10 to prevent foreign substances (such as grease on the roller bearing 10) from entering the motor side. On the screw rotor 4 side of the roller bearing 10, grease on the roller bearing 10 is installed. A lip seal 13 is provided for sealing so as not to flow out to the screw rotor 4 side, and a lip seal 14 for sealing the target gas or lubricating fluid from entering the roller bearing 10 side from the suction flow path 5. .

  A labyrinth seal 15, a lip seal 16, and a lip seal 17 are provided in the bearing shaft seal space 9 on the discharge side between the screw rotor 4 and the ball bearing 10 in order from the screw rotor 4 side. The labyrinth seal 15 includes a rotor that is fitted to the rotor shaft 7 and rotates together with the rotor shaft 7, and a known stator that is fitted and fixed to the inner wall of the bearing shaft sealing chamber 9 so as not to contact the rotor. Non-contact seal. A sleeve 18 is fitted on the outer periphery of the rotor shaft 7 between the labyrinth seal 15 and the ball bearing 11 with an interference fit, and the lip seals 16 and 17 are disposed on the outer periphery of the sleeve 18 rotating integrally with the rotor shaft 7. It comes in sliding contact. The lip seal 16 is installed in a direction that seals intrusion of the target gas from the labyrinth seal 15 side, and the lip seal 17 is installed in a direction that prevents the outflow of grease or the like from the ball bearing 11. The sleeve 18 is preferably sprayed with a material such as WC (tungsten carbide) or chromia (chromium oxide) on its outer peripheral surface to improve wear resistance. The lip seals 16 and 17 are made of PTFE (tetrafluoroethylene). Resins) are preferred.

  Further, in the housing 2, an open channel 19 for communicating the bearing shaft sealing space 8 between the lip seal 13 and the lip seal 14 to the outside, and a bearing shaft sealing space 9 between the labyrinth seal 15 and the lip seal 16 are provided. Is connected to the suction flow path 5.

Next, the operation of the screw compressor 1 will be described.
The screw rotor 4 of the screw compressor 1 sucks and compresses the target gas from the suction flow path 5 and discharges it from the discharge flow path 6. Therefore, naturally, the suction flow path 5 has a lower pressure than the service pressure of the lip seal 16 (for example, about 0.3 kgf / cm ² ). At this time, the lubricating fluid contained in the target gas lubricates and seals between the male and female screw rotors 4 and between the screw rotor 4 and the inner wall of the rotor chamber 3.

  From the gap between the rotor shaft 7 on the discharge side and the housing 2, the lubricating fluid and the target gas tend to flow out due to the pressure of the compressed target gas. The labyrinth seal 15 seals the bearing shaft sealing space 9 around the rotor shaft 7 leaving only a minute gap having a complicated shape between the stator and the rotor. The lubricating fluid and the target gas hardly pass through the labyrinth seal 15 from the screw rotor 4 side to the bearing 10 side due to the flow path resistance of the gap of the labyrinth seal 15. The lubricating fluid and the target gas that have been able to pass through the gap of the labyrinth seal 15 slightly lose their pressure due to the flow path resistance of the labyrinth seal 15.

  As a result, even if the lubricating fluid or the target gas passes through the labyrinth seal 15, its pressure becomes smaller than the service pressure of the lip seal 16 and is completely blocked by the lip seal 16, so that it enters the ball bearing 11 side. Can not do it.

  If there is no communication path 20 and the bearing shaft sealing space 9 between the labyrinth seal 15 and the lip seal 16 is a sealed space, the lubricating fluid and the target gas leaking through the labyrinth seal 15 are accumulated little by little. Then, the amount of substance in the shaft seal space 9 between the labyrinth seal 15 and the lip seal 16 is increased, and the internal pressure is increased. When the pressure in the bearing shaft seal space 9 between the labyrinth seal 15 and the lip seal 16 exceeds the service pressure of the lip seal 16, the lip seal 16 is deformed or damaged, and the lubricating fluid and the target gas are moved to the ball bearing 11 side. Infiltrate.

However, since the screw compressor 1 of the present reference example is provided with the communication passage 20 that connects the bearing shaft seal space 9 between the labyrinth seal 15 and the lip seal 16 to the suction flow path 5, the labyrinth seal 15 The lubricating fluid and the target gas that have passed through the gap are discharged to the suction flow path 5 through the communication path 20. As a result, in the bearing shaft sealing space 9 between the labyrinth seal 15 and the lip seal 16, the pressure does not increase and the sealed state of the lip seal 16 is maintained.

  Further, the fact that the pressure in the bearing shaft seal space 9 does not increase contributes to extending the life of the lip seal without damaging the lip seal 16 or wearing it in a short time. Further, when the lip seal 16 and the lip seal 17 are brought into sliding contact with the sleeve 18 fitted to the rotor shaft 7, the wear of the lip seals 16 and 17 is further reduced, and the life can be further increased.

  Further, since the lubricating fluid and the target gas discharged from the bearing shaft seal space 9 to the suction flow path are again sucked into the rotor chamber 3 and compressed by the screw rotor 4, they are discharged out of the system and become a loss. There is no.

The labyrinth seal 15 and the lip seal 16 used in the screw compressor 1 of this reference example have a smaller installation space and are less expensive than mechanical seals used in conventional screw compressors. For this reason, the screw compressor 1 of the present reference example can be provided at a lower cost than the conventional screw compressor. Moreover, since the labyrinth seal 15 is non-contact, it does not wear like a mechanical seal and its maintenance cost is low.

Then, the screw compressor 1 of 1st Embodiment of this invention is shown in FIG. In the present embodiment, the same components as those in the reference example are denoted by the same reference numerals and description thereof is omitted. In the screw compressor 1 of the present embodiment, the communication passage 20 is connected to an intermediate pressure portion near the suction side of the rotor chamber 3. The pressure in the intermediate pressure part is sufficiently lower than the service pressure of the lip seal 16. The screw compressor 1 of the first embodiment is a so-called water-lubricated type that employs water as a lubricating fluid.

  The housing 2 is provided with a shaft seal fluid passage 21 for supplying the same water as the lubricating fluid as a shaft seal fluid between the screw rotor 4 of the rotor shaft 7 and the labyrinth seal 15. The shaft 7 is provided with an annular groove 22 that allows the water supplied from the shaft-sealed fluid flow path 21 to spread over the entire circumference of the rotor shaft 7.

  As a result, the gap between the housing 2 and the rotor shaft 7 is filled with the water of the shaft seal fluid, and the target gas is not leaked from between the housing 2 and the rotor shaft 7. As a result, the amount of the target gas leaking from the labyrinth seal 15 becomes very small.

  Further, the housing 2 is provided with an open flow path 23 that opens the bearing shaft seal space 9 between the lip seal 16 and the lip seal 17 to the outside by communicating with the outside.

  Accordingly, even if the water of the shaft seal fluid exceeds the lip seal 16 and enters the bearing shaft seal space 9 on the ball bearing 11 side due to wear due to the life of the lip seal 16, the water is Since it is discharged to the outside from the open channel 23, it does not enter the inside of the ball bearing 11 and cause a problem.

Furthermore, the detail of the screw compressor 1 of 2nd Embodiment of this invention is shown in FIG. Components in arrangement and figures unillustrated portions denoted by the same reference numerals as in the first embodiment will be omitted because it is same as the first embodiment.

In this embodiment, it replaces with the labyrinth seal 15 of 1st Embodiment, and the spiral seal is comprised by providing the external thread-like spiral part 24 which protrudes to the circumference | surroundings on the rotor shaft 7. FIG. Also by this spiral seal, the water of the shaft seal fluid supplied from the shaft seal fluid channel 21 can be substantially suppressed from leaking to the bearing shaft seal space 9 on the lip seal 16 side.

  In the present embodiment, the spiral groove 25 is formed in the contact portion of the lip seal 16 with respect to the rotor shaft 7. The spiral groove 25 can enhance the sealing ability of the lip seal 16.

Next, FIG. 4 shows a screw compressor 1 of a reference example of the present invention, which is different from FIG. In this reference example , the same components as those in the reference example of FIG. 1 or the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the housing 2 of this reference example , similarly to the open flow path 23, an open flow path 26 that opens the atmosphere by communicating the bearing shaft seal space 9 between the labyrinth seal 15 and the lip seal 16 to the outside is provided. ing.

  By providing the open flow path 26, the lubricating fluid and the target gas that have passed through the labyrinth seal 15 are discharged to the outside from the open flow path 26, so that the bearing shaft sealing space between the labyrinth seal 15 and the lip seal 16 is released. The pressure of 9 is not raised.

  Further, when the target gas to be compressed is steam, it is confirmed whether or not the sealing performance of the labyrinth seal 15 and the lip seal 16 is properly maintained by providing ceramic humidity sensors in the open flow paths 23 and 26. Can do. Furthermore, an automatic monitoring device may be provided that displays a warning message when the measured value of the humidity sensor is monitored and exceeds a predetermined value.

  In order to improve the sealing performance, a plurality of lip seals 13, 14, 16, and 17 may be provided in the axial direction.

In addition, although said 1st or 2nd embodiment concerns a screw compressor, this invention is applicable also to a screw expander (expander).

The schematic sectional drawing of the screw compressor of the reference example of this invention. 1 is a schematic sectional view of a screw compressor according to a first embodiment of the present invention. The schematic fragmentary sectional view of the screw compressor of 2nd Embodiment of this invention. The schematic sectional drawing of the screw compressor of another reference example of this invention.

Explanation of symbols

1 Screw compressor (screw fluid machine)
2 Housing 3 Rotor chamber 4 Screw rotor 5 Suction flow path 6 Discharge flow path 7 Rotor shaft 9 Bearing shaft sealing space 11 Ball bearing 15 Labyrinth seal (non-contact seal)
16 Lip seal 18 Sleeve 20 Communication path 21 Shaft seal fluid flow path 23 Open flow path 25 Spiral groove 26 Open flow path

Claims (3)

In a screw fluid machine that compresses a target gas by a screw rotor that engages with a male and female accommodated in a rotor chamber or converts an expansion force of the target gas into a rotational force,
A non-contact seal between the screw rotor and the bearing on the high-pressure side of the rotor shaft of the screw rotor;
A sleeve fitted on the outer periphery of the rotor shaft between the non-contact seal and the bearing;
A lip seal slidably in contact with the outer periphery of the sleeve;
A communication path that communicates a space between the non-contact seal and the lip seal to a low-pressure space that is equal to or lower than a service pressure of the lip seal ;
A screw fluid machine comprising a shaft seal fluid flow path for supplying shaft seal fluid to the rotor shaft between the screw rotor and the non-contact seal .   The screw fluid machine according to claim 1, wherein the low-pressure space is a suction passage for the target gas or a low-pressure portion of the rotor chamber. The screw fluid machine according to claim 1 or 2 , wherein a spiral groove is formed in a contact portion of the lip seal with respect to the sleeve.

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