JP5736780B2 - Centrifugal compressor - Google Patents

Description

  The present invention relates to a centrifugal compressor, and more particularly to a centrifugal compressor having a non-contact seal.

  2. Description of the Related Art Conventionally, as a shaft seal structure of a centrifugal compressor that rotates at a high speed, a non-contact seal having a rotary ring provided on the impeller rotary shaft side and a fixed ring provided on the bearing housing side is known.

  For example, in Patent Document 1, as a centrifugal compressor having such a non-contact type seal, a non-contact type seal having a rotating ring and a fixed ring is provided between the rotor chamber and the bearing portion. A shaft seal device of a centrifugal compressor that supplies a seal gas to a seal is disclosed.

Japanese Patent Publication No. 7-69022

  By the way, in the non-contact type seal as described above, when the centrifugal compressor is operated, the rotating ring having the spiral groove on the surface rotates integrally with the impeller rotating shaft, so that a constant amount is provided between the rotating ring and the fixed ring. Dynamic pressure acts. Therefore, a desired sealing effect can be exhibited during operation of the centrifugal compressor. However, when the centrifugal compressor is stopped, a slight gap is generated between the rotating ring and the stationary ring due to the spiral groove on the surface of the rotating ring, so that the sealing effect may not be sufficiently exhibited.

  Therefore, when a centrifugal compressor having a non-contact type seal is used as a compressor of a heat pump, for example, the refrigerant in the loop of the heat pump is rotated from the gap between the rotating ring and the stationary ring when the centrifugal compressor is operated. It may flow into the housing that houses the gear mounting side of the shaft.

  More specifically, immediately after the heat pump stops, that is, immediately after the centrifugal compressor stops, the heat pump loop is at a higher temperature and pressure than the gear-side housing, so there is a pressure difference between both ends of the non-contact seal. Arise. If a pressure difference occurs, the refrigerant in the loop of the heat pump may flow from the back surface of the impeller through the gap between the rotating ring and the stationary ring into the gear-side housing.

  The present invention has been made in view of such a point, and the object thereof is a centrifugal compressor having a non-contact seal that seals the impeller rotary shaft in a housing that houses the gear mounting side of the impeller rotary shaft. It is to effectively suppress the refrigerant from flowing into the gear side housing relative to the non-contact type seal.

  In order to achieve the above object, a centrifugal compressor according to the present invention has a non-seal that seals the rotary shaft in a housing that houses a gear mounting side of the rotary shaft that has an impeller attached to one end and a gear attached to the other end. A centrifugal compressor having a contact-type seal that detects an outer pressure that is an impeller side pressure from the non-contact type seal and an inner pressure that is a pressure in the housing on the gear side from the non-contact type seal. The pressure in the housing closer to the gear side than the non-contact type seal is adjusted so that the difference between the pressure detecting means for detecting and the outside pressure detected by the pressure detecting means is equal to or less than a predetermined reference value. Pressure adjusting means, wherein the pressure adjusting means is located on the gear side of the non-contact seal when the outer pressure detected by the pressure detecting means is higher than the inner pressure. And supplying the insoluble gas to the lubricating oil in the housing within.

Further, the pressure adjusting means may be configured such that when the outer pressure detected by the pressure detecting means is lower than the inner pressure, the difference between the outer pressure and the inner pressure is less than a predetermined reference value. The pressure in the housing on the gear side relative to the contact seal may be lowered.

  According to the centrifugal compressor of the present invention, in the centrifugal compressor having the non-contact type seal that seals the impeller rotary shaft in the housing that houses the gear mounting side of the impeller rotary shaft, the refrigerant is more geared than the non-contact type seal. It is possible to effectively suppress the flow into the side housing.

It is a typical fragmentary sectional view showing the centrifugal compressor concerning one embodiment of the present invention. It is a flow which shows the pressure control by the controller of the centrifugal compressor which concerns on one Embodiment of this invention. It is a typical fragmentary sectional view showing a centrifugal compressor concerning other embodiments of the present invention. It is a typical fragmentary sectional view showing a centrifugal compressor concerning other embodiments of the present invention.

  Hereinafter, a centrifugal compressor according to an embodiment of the present invention will be described with reference to FIGS. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  A centrifugal compressor 1 according to an embodiment of the present invention is used as a centrifugal compressor of a high-temperature heat pump that raises a heat source of, for example, 100 ° C. to 150 ° C. to 150 ° C. to 180 ° C., as shown in FIG. The impeller housing portion 10, the gear box portion (housing) 20, the pressure detection portion (pressure detection means) 40, and the pressure adjustment portion (pressure adjustment means) 50 are provided.

  In the present embodiment, the centrifugal compressor 1 is described as being applied to a high-temperature heat pump, but can be widely applied to any type of heat pump that compresses refrigerant with a centrifugal compressor such as a refrigerator.

  As shown in FIG. 1, the impeller housing portion 10 houses an impeller 11 provided with a plurality of blades (not shown), a suction port portion 12 for taking in a refrigerant from an evaporator of a high-temperature heat pump (not shown), and the impeller 11. It has an impeller accommodating portion 13, an annular diffuser flow path 14 connected to the impeller accommodating portion 13, and a scroll flow path 15 connected to the outer peripheral edge of the diffuser flow path 14.

  As shown in FIG. 1, the impeller 11 is attached to an end portion of the impeller rotating shaft 21. And the impeller 11 discharges a refrigerant | coolant to radial outward by rotating integrally with the impeller rotating shaft 21 with the drive force of the motor 24 mentioned later.

  As shown in FIG. 1, the suction port portion 12 is provided on the upstream side of the impeller housing portion 10 so as to be coaxial with the impeller 11. Further, the suction port 12 is formed so that the opening area gradually decreases from the upstream side toward the downstream side.

  The impeller accommodating portion 13 is formed so that the opening area gradually increases from the upstream side toward the downstream side so as to accommodate the impeller 11. Further, the upstream side of the impeller accommodating portion 13 communicates with the suction port portion 12.

  The annular diffuser channel 14 is formed on the downstream side portion of the impeller housing portion 10 so as to surround the impeller housing portion 13. Further, a scroll passage 15 for discharging the refrigerant to a condenser (not shown) of a high-temperature heat pump is connected to the outer peripheral edge of the diffuser passage 14.

  That is, the impeller housing unit 10 compresses (increases) by discharging the refrigerant taken from the evaporator of the high-temperature heat pump through the suction port 12 to the scroll channel 15 by the rotation of the impeller 11. Temperature and pressure increase).

  As shown in FIG. 1, the gear box portion (housing) 20 accommodates the gear mounting side of the impeller rotary shaft 21, and includes a pair of bearings 22 and 23 provided inside the gear box portion 20, and a gear box. Motor 24 attached to the side of portion 20, driven gear 26 fitted to impeller rotary shaft 21, drive gear 27 fitted to motor drive shaft 25, and elastomer that seals motor drive shaft 25. A motor shaft seal 28 made of a material and a dry gas seal (non-contact seal) 30 are provided. Further, the gear box portion 20 between the dry gas seal 30 and the bearing 22 is provided with a piping hole 29 to which a first piping 53 described later is connected.

  As shown in FIG. 1, the impeller rotating shaft 21 is rotatably supported in the gear box portion 20 by a pair of bearings 22 and 23. A driven gear 26 that meshes with the drive gear 27 is fitted to the impeller rotary shaft 21 located between the pair of bearings 22 and 23. An annular protrusion 21 a to which a rotating ring 31 constituting a dry gas seal 30 described later is attached is formed on the peripheral surface of the impeller rotating shaft 21 between the bearing 22 and the impeller 11.

  As shown in FIG. 1, the motor drive shaft 25 of the motor 24 is inserted from the side of the gear box portion 20 and is rotatably supported by a bearing (not shown). The motor drive shaft 25 is fitted with a drive gear 27 having a larger diameter than the driven gear 26. A motor shaft seal 28 that seals the motor drive shaft 25 is provided on the side of the gear box portion 20 through which the motor drive shaft 25 is inserted. In addition, in the gear box portion 20, lubricating oil is sprayed in order to suppress wear of the driven gear 26 and the driving gear 27 that mesh with each other.

  As shown in FIG. 1, the dry gas seal 30 includes a rotary ring 31 provided on the impeller rotary shaft 21 side, and a fixed ring 32 provided on the gear box portion 20 side. The rotary ring 31 is fixed to the impeller rotary shaft 21 via an annular protrusion 21a. The fixed ring 32 is attached to an attachment portion 20a formed inside the gear box portion 20 so as to be movable in the axial direction via a coil spring (not shown). A plurality of spiral grooves (not shown) are provided on the side surface of the rotating ring 31 that faces the fixed ring 32. In other words, when the rotary ring 31 rotates integrally with the impeller rotary shaft 21, the dry gas seal 30 causes dynamic pressure to act between the rotary ring 31 and the fixed ring 32 due to the plurality of spiral grooves, thereby causing the impeller rotary shaft 21 to pivot. It is configured to seal. This dynamic pressure separates the stationary ring 32 from the rotating ring 31 against the biasing force of the coil spring. On the other hand, when the impeller rotating shaft 21 is stopped, the rotating ring 31 and the stationary ring 32 come into contact with each other by the biasing force of the coil spring. In this contacted state, a slight gap due to the spiral groove exists between the rotating ring 31 and the fixed ring 32.

  As shown in FIG. 1, the pressure detection unit (pressure detection unit) 40 includes a first pressure sensor 41 provided in the scroll flow path 15 of the impeller housing unit 10 and a first pipe 53 of the pressure adjustment unit 50 described later. And a second pressure sensor 42 provided. The first pressure sensor 41 detects a pressure in the scroll flow path 15 corresponding to a pressure outside the dry gas seal 30 (a pressure closer to the impeller 11 than the dry gas seal 30). The second pressure sensor 42 detects the pressure in the first pipe 53 corresponding to the pressure inside the dry gas seal 30 (pressure in the gear box portion 20 on the gear 26 side relative to the dry gas seal 30). . Moreover, the 1st pressure sensor 41 and the 2nd pressure sensor 42 are connected to the controller 57 of the pressure adjustment part 50 mentioned later via an electrical wiring.

  In the present embodiment, the pressure detection unit 40 is described as including the first pressure sensor 41 and the second pressure sensor 42 as separate bodies, but a differential pressure sensor, for example, can also be applied. Further, the first pressure sensor 41 may be provided, for example, in the diffuser flow path 14 as long as it is downstream of the impeller 11.

  As shown in FIG. 1, the pressure adjusting unit (pressure adjusting means) 50 includes a high pressure tank 51, a low pressure tank 52, a first pipe 53 having one end connected to the pipe hole 29 of the gear box part 20, and a first A three-way selector valve 54 provided at the other end of the pipe 53, a second pipe 55 that communicates the three-way selector valve 54 and the high-pressure tank 51, and a third pipe 56 that communicates the three-way selector valve 54 and the low-pressure tank 52. And a controller 57 for controlling the path switching of the three-way switching valve 54.

  The high-pressure tank 51 is a known gas cylinder or the like, and an inert gas (for example, nitrogen gas) that is insoluble with respect to the lubricating oil in the gear box portion 20 is stored therein at a high pressure. Note that the high-pressure gas may be configured to be supplied to the high-pressure tank 51 after being pressurized by a not-shown animal pressure device.

  The low-pressure tank 52 is a known vacuum tank or the like that is lower than the atmospheric pressure, and is connected to the piping hole 29 of the gear box portion 20 through the first piping 53, the three-way switching valve 54, and the third piping 56. .

  As shown in FIG. 1, the three-way switching valve 54 has a port A on the first pipe 53 side, a port B on the second pipe 55 side, and a port C on the third pipe 56 side. When the port A and the port B communicate with each other, the high-pressure gas in the high-pressure tank 51 is configured to flow from the second pipe 55 into the gear box portion 20 through the first pipe 53. That is, the pressure in the gear box portion 20 on the gear 26 side of the dry gas seal 30 is increased by the high pressure gas flowing from the high pressure tank 51. On the other hand, when the port A and the port C communicate with each other, the gas in the gear box portion 20 is configured to flow from the first pipe 53 to the low-pressure tank 52 through the third pipe 56. That is, the pressure inside the gear box portion 20 closer to the gear 26 than the dry gas seal 30 is lowered by drawing the internal gas into the low-pressure tank 52.

  The controller 57 includes a known CPU, ROM, RAM, input port, output port, and the like. Further, the output signals of the first pressure sensor 41 and the second pressure sensor 42 are input to the controller 57 after A / D conversion. Further, as shown in FIG. 1, the controller 57 includes a differential pressure calculation unit 58 and a switching control unit 59 as some functional elements.

The differential pressure calculation unit 58 is based on the output values of the first pressure sensor 41 and the second pressure sensor 42, the pressure P ₁ on the impeller 11 side relative to the dry gas seal 30, and the gear 26 side relative to the dry gas seal 30. A differential pressure ΔP with respect to the pressure P ₂ in the gear box portion 20 is calculated. Incidentally, in order to estimate accurately the pressure between the back surface and the dry gas seal 30 of the impeller 11 may be multiplied by a correction factor determined in advance by experiments or the like on the detection value P ₁ of the first pressure sensor 41. When a differential pressure sensor is used for the pressure detection unit 40, the differential pressure calculation unit 58 may be omitted by directly reading the detection value of the differential pressure sensor into the controller 57.

The switching control unit 59 controls the path switching of the three-way switching valve 54 according to the differential pressure ΔP calculated by the differential pressure calculation unit 58. Specifically, when the absolute value of the differential pressure ΔP is larger than a predetermined reference value P _th and the pressure P ₁ on the impeller 11 side is higher than the pressure P ₂ in the gear box portion 20 on the gear 26 side, A control signal that communicates between port A and port B is output until the absolute value of the differential pressure ΔP becomes equal to or less than a predetermined reference value _Pth . That is, the high-pressure gas in the high-pressure tank 51 flows into the gear box portion 20, and the pressure P ₂ in the gear box portion 20 on the gear 26 side is increased following the pressure P ₁ on the impeller 11 side. The refrigerant is prevented from flowing into the gear box portion 20.

Further, when the absolute value of the differential pressure ΔP is larger than a predetermined reference value P _th and the pressure P ₁ on the impeller 11 side is lower than the pressure P ₂ in the gear box portion 20 on the gear 26 side, the differential pressure ΔP Until the absolute value of becomes equal to or less than a predetermined reference value _Pth , a control signal for communicating the port A and the port C is output. That is, the gas in the gear box portion 20 is drawn into the low-pressure tank 52, and the pressure P ₂ in the gear box portion 20 on the gear 26 side is stepped down following the pressure P ₁ on the impeller 11 side to thereby lubricate. Leakage of oil to the impeller housing 10 side is suppressed.

On the other hand, when the absolute value of the differential pressure ΔP is smaller than the predetermined reference value P _th , that is, when the pressure P ₁ on the impeller 11 side and the pressure P ₂ in the gear box portion 20 on the gear 26 side are substantially equal, A control signal for cutting off the communication of A, B, and C is output.

The predetermined reference value P _th can be appropriately adjusted and set according to the type of refrigerant and the viscosity of the lubricating oil. Further, the predetermined reference value _Pth may be set to 0 (zero) in order to reliably prevent the refrigerant from flowing in or the lubricating oil from leaking out.

  Since the centrifugal compressor 1 according to an embodiment of the present invention is configured as described above, for example, the following control is performed according to the flow shown in FIG.

In step (hereinafter, simply referred to as “S”) 100, the detected values of the first pressure sensor 41 and the second pressure sensor 42 are read into the differential pressure calculation unit 58 of the controller 57. Then, a differential pressure ΔP between the pressure P ₁ on the impeller 11 side and the pressure P ₂ in the gear box portion 20 on the gear 26 side is calculated.

In S110, the switching control unit 59 checks whether or not the absolute value of the differential pressure ΔP calculated in S100 is greater than a predetermined reference value _Pth . If the absolute value of the differential pressure ΔP is larger than the predetermined reference value P _th, the process proceeds to S120. On the other hand, when the absolute value of the differential pressure ΔP is equal to or _smaller than the predetermined reference value P _{th, the} control of the ports A, B, and C is cut off in S160 and the control is not performed because the pressure increase or decrease in the gear box portion 20 is unnecessary. Will be returned.

In S120, the switching control unit 59, compared with the pressure P ₂ of the pressure P ₁ and the gear 26 side of the gearbox portion 20 of the impeller 11 side is performed. When the pressure P ₁ is higher than the pressure P ₂ , the process proceeds to S130 and the port A and the port B of the three-way switching valve 54 are communicated. That is, the high-pressure gas in the high-pressure tank 51 flows into the gear box portion 20, and the pressure P ₂ in the gear box portion 20 on the gear 26 side is increased.

On the other hand, when the pressure P ₁ is lower than the pressure P ₂ , the routine proceeds to S140, where the port A and the port C of the three-way switching valve 54 are communicated. That is, the gas in the gear box portion 20 is drawn into the low pressure tank 52, and the pressure P ₂ in the gear box portion 20 on the gear 26 side is reduced.

In S150, it is confirmed whether or not the absolute value of the differential pressure ΔP has reached a predetermined reference value _Pth or less. When the absolute value of the differential pressure ΔP has reached the predetermined reference value P _th or less, since the pressure increase or decrease in the gear box portion 20 is not necessary, the communication between the ports A, B, and C is shut off in S160. Control is returned.

On the other hand, when the absolute value of the differential pressure ΔP is still larger than the predetermined reference value P _th , the above-described pressure P ₂ in the gear box portion 20 on the gear 26 side is made to follow the pressure P ₁ on the impeller 11 side. The process returns to S120.

Thereafter, until the absolute value of the differential pressure ΔP becomes equal to or less than the predetermined reference value P _th , that is, when the predetermined reference value P _{th is set} to 0 (zero), the pressure P ₁ on the impeller 11 side and the gear 26 side gear This control S120 to S150 is repeated until there is no difference from the pressure P ₂ in the box portion 20.

  With the configuration as described above, the centrifugal compressor 1 according to one embodiment of the present invention has the following operations and effects.

During operation of the high-temperature heat pump, the refrigerant taken into the impeller accommodating portion 13 from the evaporator (not shown) via the suction port portion 12 is discharged from the diffuser passage 14 to the scroll passage 15 by the rotation of the impeller 11. Compressed (pressurized / heated). When the absolute value of the differential pressure ΔP becomes larger than the predetermined reference value P _th due to the increase in the pressure P ₁ on the impeller 11 side, the three-way until the absolute value of the differential pressure ΔP becomes equal to or lower than the predetermined reference value P _th. Port A and port B of the switching valve 54 communicate with each other. That is, by supplying the high-pressure gas from the high-pressure tank 51, the pressure P ₂ in the gear box portion 20 on the gear 26 side is increased so as to follow the pressure P ₁ on the impeller 11 side, whereby the differential pressure ΔP is predetermined. _Is maintained below the reference value _Pth .

  Therefore, since the inside of the gear box portion 20 is suppressed from becoming a low pressure during the operation of the high-temperature heat pump, the refrigerant flows from the back surface of the impeller 11 to the gear 26 side from a slight gap between the rotating ring 31 and the stationary ring 32. The flow into the gear box 20 can be effectively suppressed.

Further, while the high-temperature heat pump is stopped, the temperature of the refrigerant in the impeller housing portion 10 is suddenly lowered and the pressure is lowered. When the absolute value of the differential pressure ΔP becomes larger than the predetermined reference value P _th due to the decrease in the pressure P ₁ on the impeller 11 side, the three-way switching is performed until the absolute value of the differential pressure ΔP becomes equal to or lower than the predetermined reference value P _th. The port A and the port C of the valve 54 are communicated. That is, the pressure P ₂ in the gear box portion 20 on the gear 26 side is lowered by drawing the gas into the low pressure tank 52 so as to follow the pressure P ₁ on the impeller 11 side, so that the differential pressure ΔP is a predetermined reference value. _Pth or less is maintained.

  Therefore, since the pressure in the impeller housing portion 10 is suppressed to a low pressure while the high temperature heat pump is stopped, the lubricating oil in the gear box portion 20 on the gear 26 side is slightly changed between the rotating ring 31 and the stationary ring 32. Leaking into the impeller housing portion 10 from the gap can be effectively suppressed.

  Further, when the pressure in the gear box portion 20 on the gear 26 side is increased, an inert gas (for example, nitrogen gas) that is insoluble in the lubricating oil in the gear box portion 20 is supplied from the high-pressure tank 51.

  Accordingly, since dissolution of the supplied high-pressure gas into the lubricating oil is suppressed, the pressure inside the gear box portion 20 on the gear 26 side can be efficiently increased in a short time, and the amount of high-pressure gas required for the pressure increase Can also be optimized. Moreover, deterioration of the lubricating oil in the gear box portion 20 can be effectively prevented.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

  In the above-described embodiment, the second pressure sensor 42 has been described as being provided in the first pipe 53. However, if the pressure in the gear box portion 20 on the gear 26 side can be detected, for example, the back surface of the stationary ring 32 Or between the pair of bearings 22 and 23.

  Moreover, although the pipe hole 29 to which the first pipe 53 is connected has been described as being provided in the gear box portion 20 between the dry gas seal 30 and the bearing 22, for example, it is positioned between the pair of bearings 22 and 23. You may provide in the gear box part 20 to do.

  Further, the three-way switching valve 54 for branching the first pipe 53 is not necessarily required, and a flow rate adjusting valve is provided separately for the second pipe 55 and the third pipe 56, and the second pipe 55 and the third pipe 56 are respectively provided. The gear box portion 20 may be directly communicated with the gear box portion 20.

  Moreover, in the above-mentioned embodiment, although the pressure adjustment part 50 demonstrated as what has both the high pressure tank 51 and the low pressure tank 52, you may provide only either one tank.

In the configuration in which the pressure adjusting unit 50 includes only the high-pressure tank 51, the three-way switching valve 54 is replaced with an opening / closing valve 54a as shown in FIG. When the detection value (pressure P ₁ ) of the first pressure sensor 41 is higher than the detection value (pressure P ₂ ) of the second pressure sensor 42, the differential pressure ΔP between the pressure P ₁ and the pressure P ₂ is a predetermined value. The on-off valve 54a may be opened until the reference value _{Pth is} less than or equal to 0 (zero) to increase the pressure in the gear box portion 20 on the gear 26 side.

In the configuration in which the pressure adjusting unit 50 includes only the low-pressure tank 52, the three-way switching valve 54 is replaced with an opening / closing valve 54b as shown in FIG. When the detected value (pressure P ₁ ) of the first pressure sensor 41 is lower than the detected value (pressure P ₂ ) of the second pressure sensor 42, the differential pressure ΔP between the pressure P ₁ and the pressure P ₂ is a predetermined value. The on-off valve 54b may be opened until the reference value _{Pth is} less than or equal to 0 (zero), and the pressure in the gear box portion 20 on the gear 26 side may be reduced.

1 Centrifugal Compressor 11 Impeller 20 Gearbox (Housing)
21 Impeller rotating shaft (Rotating shaft)
30 Dry gas seal (non-contact seal)
31 Rotating ring 32 Fixed ring 40 Pressure detection part (pressure detection means)
41 1st pressure sensor 42 2nd pressure sensor 50 Pressure adjustment part (pressure adjustment means)
51 High-pressure tank 52 Low-pressure tank 53 First pipe 54 Three-way selector valve 55 Second pipe 56 Third pipe 57 Controller

Claims (2)

A centrifugal compressor having a non-contact seal that seals the rotating shaft in a housing that houses a gear mounting side of the rotating shaft that has an impeller attached to one end and a gear attached to the other end,
A first pressure sensor that detects an outer pressure that is a pressure on an impeller side than the non-contact seal ;
A second pressure sensor that detects an inner pressure that is a pressure in the housing on the gear side of the non-contact seal;
In the housing on the gear side with respect to the non-contact type seal so that the difference between the outer pressure detected by the first pressure sensor and the inner pressure detected by the second pressure sensor is not more than a predetermined reference value. Pressure adjusting means for adjusting the pressure of
The pressure adjusting means is
When the outer pressure detected by the first pressure sensor is higher than the inner pressure detected by the second pressure sensor , the difference between the outer pressure and the inner pressure is less than a predetermined reference value. An insoluble gas with respect to the lubricating oil in the housing is supplied into the housing on the gear side of the non-contact seal, and the external pressure detected by the first pressure sensor is detected by the second pressure sensor. Lowering the pressure in the housing on the gear side than the non-contact seal so that the difference between the outer pressure and the inner pressure is less than or equal to a predetermined reference value. Features centrifugal compressor. A piping hole is provided in the housing on the gear side from the non-contact seal,
The pressure adjusting means is
A high-pressure tank, a low-pressure tank, a first pipe having one end connected to the pipe hole, a three-way switching valve connected to the other end of the first pipe, the three-way switching valve, and the high-pressure tank communicate with each other. A second pipe, and a third pipe communicating the three-way switching valve and the low-pressure tank;
When the outer pressure detected by the first pressure sensor is higher than the inner pressure detected by the second pressure sensor, the path of the three-way switching valve is switched to connect the first pipe and the second pipe. And supplying insoluble gas from the high-pressure tank to the lubricating oil in the housing so that a difference between the outer pressure and the inner pressure is not more than a predetermined reference value, and the first pressure sensor When the outer pressure detected by the second pressure sensor is lower than the inner pressure detected by the second pressure sensor, the path of the three-way switching valve is switched to connect the first pipe and the third pipe, and the outer pressure The pressure in the housing on the gear side is lowered from the non-contact type seal so that the difference between the inner pressure and the inner pressure is not more than a predetermined reference value.
The centrifugal compressor according to claim 1.

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