WO2018003748A1

WO2018003748A1 - Refrigerator

Info

Publication number: WO2018003748A1
Application number: PCT/JP2017/023420
Authority: WO
Inventors: 直也三吉; 上田　憲治; 長谷川　泰士
Original assignee: 三菱重工サーマルシステムズ株式会社
Priority date: 2016-06-30
Filing date: 2017-06-26
Publication date: 2018-01-04
Also published as: JP2018004142A; US20190078811A1; CN108779946A; CN108779946B

Abstract

The purpose of the present invention is to provide a refrigerator in which the capacity of an oil tank can be made smaller than in the prior art while a foaming phenomenon is addressed. The refrigerator is provided with: a refrigeration cycle which includes a condenser, an evaporator, and an electric compressor having a compression mechanism to be driven by a motor and in which a refrigerant circulates; an oil tank (23) in which a lubricating oil is stored; a heater (27) which is set in the oil tank (23) and which heats the lubricating oil; a lubricating oil supply line (22) which is connected to the oil tank (23) and which supplies the lubricating oil from the oil tank (23) into a housing having the motor housed therein; a lubricating oil discharge line (25) which returns the lubricating oil from the housing back to the oil tank (23); a pressure equalizing pipe (29) which has one end connected to the oil tank (23) and the other end connected to the refrigeration cycle; and a buffer tank (28) which is set to the pressure equalizing pipe (29), which receives the refrigerant and the lubricating oil flowing out from the oil tank (23), and in which the lubricating oil is stored.

Description

refrigerator

The present invention relates to a refrigerator.

The turbo compressor installed in the turbo refrigerator is composed of a compression mechanism, a speed increasing mechanism, and the like. In order for the turbo compressor to operate stably, it is necessary to continue to properly supply the lubricating oil to the bearings that support the impeller of the compression mechanism, the gears of the speed increasing mechanism, and the like. The lubricating oil system includes an oil tank and an oil pump, and the lubricating oil stored in the oil tank is supplied to the bearings and gears of the turbo compressor by the oil pump. The lubricating oil supplied to the bearings and gears is returned to the oil tank and repeatedly circulates through the lubricating oil system.

In the compression mechanism, since the refrigerant system and the lubricating oil system are not completely independent, the refrigerant is dissolved in the lubricating oil. Since the viscosity of the lubricating oil decreases when the refrigerant dissolves, the inside of the oil tank is maintained at a low pressure in order to reduce the amount of refrigerant dissolved in the oil tank. Therefore, for example, a pressure equalizing pipe that communicates with a low-pressure portion (for example, an evaporator or a compressor suction port) of the refrigerant system is connected to the oil tank.

In the following Patent Document 1, since the pressure in the oil tank is reduced when the turbo chiller is started, and the refrigerant dissolved in the lubricating oil is gasified and formed, the refrigerant passing through the turbo compressor is started at the start. A technique for setting a suction volume control unit for controlling a volume to a target opening degree is disclosed. Patent Document 2 below discloses a technique for equalizing the oil tank internal pressure and the economizer internal pressure by connecting the other end of the pressure equalizing pipe whose one end is connected to the oil tank to an economizer instead of an evaporator. ing.

JP 2009-186030 A JP 2009-293901 A

In the oil tank communicating with the refrigerant system, the internal pressure decreases at the start-up or transition of the turbo refrigerator where the pressure of the refrigerant system decreases. Here, the time of transition is when changing the operating state, for example, when lowering the output of the turbo chiller. When the pressure in the lubricating oil system decreases, such as when the pressure inside the oil tank decreases, the refrigerant that has melted into the lubricating oil cannot be melted beyond the saturation state, and a refrigerant gas is generated and the lubricating oil foams. Get up.

In the oil tank where the forming phenomenon has occurred, the oil level rises compared to the normal time when the forming phenomenon does not occur. In addition, when the forming phenomenon occurs, the amount of lubricating oil that can be supplied to bearings, gears, and the like in the lubricating oil system decreases. In the case of a low-pressure refrigerant (for example, R1233zd), since the specific volume of the refrigerant gas is larger than that of a high-pressure refrigerant (for example, R134a), the gas volume generated in the forming phenomenon is large. Therefore, in the low-pressure refrigerant, the difference from the normal time is further increased with respect to the increase in the oil level and the decrease in the amount of oil supply.

The pressure equalizing pipe connected to the oil tank is connected to the upper part of the oil tank. However, when the oil level rises during forming, the formed lubricating oil flows into the pressure equalizing pipe, and the lubricating oil is connected to the destination of the pressure equalizing pipe. There is a risk of flowing to an evaporator or the like. Therefore, conventionally, in order to cope with the oil level rise during forming, the height of the oil tank has been increased.

In addition, by arranging the oil pump on the bottom of the oil tank while increasing the depth of the oil tank so that the oil pump does not suck the refrigerant gas at the time of forming, the position of the oil surface and the oil pump at the time of forming is changed. They are also being released.

In either case, it is necessary to increase the size of the oil tank in the height direction, and the capacity of the oil tank must be set large in order to cope with the forming phenomenon.

This invention is made | formed in view of such a situation, Comprising: It aims at providing the refrigerator which can make the capacity | capacitance of an oil tank small compared with the past, corresponding to a forming phenomenon. .

In order to solve the above problems, the refrigerator of the present invention employs the following means.
That is, the refrigerator according to the present invention includes an electric compressor having a compression mechanism driven by a motor, a condenser, an evaporator, a refrigeration cycle in which refrigerant circulates, an oil tank in which lubricating oil is stored, A heater installed in the oil tank for heating the lubricating oil; and connected to the oil tank for supplying the lubricating oil from the oil tank to a housing for housing the motor; An oil circulation pipe for returning the lubricating oil to the tank, and one end connected to the oil tank separately from the oil circulation pipe, the other end is installed in the pressure equalization pipe connected to the refrigeration cycle, and the pressure equalization pipe, A buffer tank for receiving the refrigerant and the lubricating oil flowing out from the oil tank and storing the lubricating oil.

According to this configuration, the motor that drives the compression mechanism is housed in the housing, and the lubricating oil is supplied from the oil tank to the housing, so that the lubricating oil lubricates the bearings that support the rotating shaft of the motor. Can be made. In addition, one end of the pressure equalizing pipe is connected to the oil tank, and the other end of the pressure equalizing pipe is connected to the refrigeration cycle, so that the pressure at the connection portion with the refrigeration cycle is substantially equal to the pressure in the oil tank. The part to which the pressure equalizing pipe is connected in the refrigeration cycle is a part where the pressure is low in the refrigeration cycle such as an evaporator and a compressor suction port.
Furthermore, the refrigerant and lubricating oil that have flowed out of the oil tank are supplied to the buffer tank via the pressure equalizing pipe, and are temporarily stored in the buffer tank. Thereby, even if forming occurs inside the oil tank and the refrigerant and the lubricating oil flow out of the oil tank, the lubricating oil is stored in the buffer tank and does not flow to the refrigeration cycle, but only the refrigerant goes to the refrigeration cycle.

In the above invention, one end is connected to the buffer tank, and the other end is connected to the oil tank separately from the pressure equalizing pipe, and a return pipe for returning the lubricating oil stored in the buffer tank to the oil tank is further provided. You may prepare.

According to this configuration, one end of the return pipe is connected to the buffer tank, and the other end of the return pipe is connected to the oil tank, so that the lubricating oil stored in the buffer tank is returned to the oil tank. Thus, the lubricating oil that has flowed out of the oil tank and accumulated in the buffer tank is returned to the oil tank without flowing into the refrigerant cycle.

In the above invention, the position where the return pipe is connected to the oil tank may be close to the position where the oil circulation pipe is connected in the oil tank.

According to this configuration, since the lubricating oil returned from the buffer tank is returned to the vicinity of the position where the oil circulation pipe is connected in the oil tank, the lubricating oil returned from the buffer tank is formed in the oil tank 23. Even if it occurs, it is mixed with lubricating oil that is not affected by forming.

In the above invention, the oil tank may be divided by a partition plate into a separation region where the lubricating oil returned from the housing flows and a discharge region where the lubricating oil is supplied to the housing.

According to this configuration, the lubricating oil in which the refrigerant is dissolved is supplied to the separation region, and the lubricating oil in which the refrigerant is dissolved in the separation region is separated into the lubricating oil and the refrigerant. Then, the separated lubricating oil is supplied from the separation region to the discharge region and is supplied into the housing. Since the separation region and the discharge region are partitioned by a partition plate, the lubricating oil flowing into the oil tank is efficiently separated in the separation region by utilizing the difference between the lubricating oil and the refrigerant and the closed space. . Further, even if the forming phenomenon occurs in the separation region, it is possible to prevent the foamed lubricating oil from flowing into the discharge region.

In the above invention, a flow forming plate for directing the flow of the lubricating oil stored in the oil tank from the upper part to the lower part or from the lower part to the upper part may be installed in the separation region.

According to this configuration, a flow from the upper part to the lower part in the stored lubricating oil, or a flow from the lower part to the upper part is formed.

In the above invention, the partition plate may be installed separately from the bottom surface of the oil tank.

According to this configuration, the lubricating oil in which the refrigerant has melted flows downstream without staying at the bottom in the divided region.

According to the present invention, it is possible to reduce the capacity of the oil tank as compared with the conventional one while accommodating the forming phenomenon.

It is a lineblock diagram showing a turbo refrigerator concerning one embodiment of the present invention. It is a longitudinal cross-sectional view which shows the turbo compressor of the turbo refrigerator based on one Embodiment of this invention. It is a perspective view which shows the oil tank of the turbo refrigerator which concerns on one Embodiment of this invention. It is a perspective view which shows the modification of the oil tank of the turbo refrigerator based on one Embodiment of this invention.

Below, turbo refrigerator 1 concerning one embodiment of the present invention is explained with reference to drawings.
As shown in FIG. 1, the turbo refrigerator 1 includes a turbo compressor 2 that compresses the refrigerant, a condenser 3 that cools and condenses the refrigerant, and further cools and supercools the refrigerant condensed in the condenser 3. A sub-cooler 4 that gives the refrigerant, a first pressure-reducing valve 5 that depressurizes the high-pressure refrigerant to an intermediate pressure, an intermediate cooler 6 that gives supercooling to the refrigerant, a second pressure-reducing valve 7 that depressurizes the refrigerant to low pressure, and a low-pressure refrigerant An evaporator 8 for evaporating is provided.

The turbo compressor 2, the condenser 3, the subcooler 4, the first pressure reducing valve 5, the intermediate cooler 6, the second pressure reducing valve 7 and the evaporator 8 constitute a refrigeration cycle, and the refrigerant is the turbo compressor 2, the condenser. 3, the subcooler 4, the first pressure reducing valve 5, the intermediate cooler 6, the second pressure reducing valve 7, and the evaporator 8 are circulated in this order. Further, the refrigerant is supplied from the intercooler 6 to the turbo compressor 2 by bypass without passing through the evaporator 8.

The turbo compressor 2 includes a housing 30 configured by integrally connecting a motor housing 31, a speed increaser housing 32, and a compressor housing 33.
As shown in FIG. 2, the motor housing 31 incorporates a motor 9 that is driven at a variable speed by an inverter device. One end 10 a of the motor shaft 10 of the motor 9 protrudes from the motor housing 31 to the speed increaser housing 32. The motor 9 includes a stator 20 and a rotor 21. A rotor 21 is fixed to the motor shaft 10, and the rotor 21 rotates inside the stator 20. The motor shaft 10 is supported by the rolling bearing 14 on the speed increaser housing 32 side. The rolling bearing 14 is composed of, for example, a plurality of angular ball bearings. The rolling bearing 14 is installed in the motor housing 31 via a bearing box (not shown).

The compressor housing 33 accommodates a compression mechanism 15 having a first stage compression stage and a second stage compression stage. The refrigerant sucked into the first stage compression stage from the outside and compressed by the first stage compression stage is sent to the second stage compression stage. Then, the refrigerant sucked into the second stage compression stage and compressed by the second stage compression stage is discharged to the outside.

A rotary shaft 11 is rotatably installed in the compressor housing 33. A first stage impeller 12 for the first stage compression stage and a second stage compression stage are disposed on one end 11a side of the rotary shaft 11. The second stage impeller 13 is provided. The rotating shaft 11 is supported by the rolling bearing 14 on the speed increaser housing 32 side. The rolling bearing 14 is composed of, for example, a plurality of angular ball bearings. The rolling bearing 14 is installed in the compressor housing 33 via a bearing box (not shown).

A small-diameter gear 17 is provided on the other end 11b side of the rotary shaft 11 supported by the rolling bearing 14. The gear 17 is meshed with a large-diameter gear 18 provided at one end 10 a of the motor shaft 10, and a speed increasing mechanism 19 is configured by these

gears

17 and 18. The speed increasing mechanism 19 is accommodated in the speed increasing device housing 32.

Lubricating oil is supplied to the rolling bearing 14 and the

gears

17 and 18 for each component.

The lubricating oil system includes a lubricating oil supply line 22 and a lubricating oil discharge line 25.
The lubricating oil supply line 22 is a pipe connecting the oil tank 23 and the turbo compressor 2. The lubricating oil is supplied from the oil tank 23 to the motor housing 31 and the speed increaser housing 32 of the turbo compressor 2 by an oil pump 36 provided in the lubricating oil supply line 22. The lubricating oil that has passed through the motor 9 and the speed increasing mechanism 19 is returned to the oil tank 23 via the lubricating oil discharge line 25. An oil cooler 24 is installed in the lubricating oil supply line 22 and the lubricating oil discharge line 25 according to the present embodiment.

In the motor housing 31 and the speed increaser housing 32, a lubricating oil inlet connected to the lubricating oil supply line 22 is formed, and the lubricating oil is supplied from the lubricating oil supply line 22 to the turbo compressor 2. The turbo compressor 2 is supplied with the refrigerant extracted from the condenser 3 constituting the refrigeration cycle. A liquid refrigerant inlet connected to the refrigerant supply line 34 is formed in the motor housing 31 and the speed increaser housing 32, and the liquid refrigerant is supplied from the refrigerant supply line 34.

The lubricating oil that has passed through the motor housing 31 and the speed increaser housing 32 of the turbo compressor 2 is discharged to the oil tank 23. The motor housing 31 and the speed increaser housing 32 are formed with a lubricating oil outlet connected to the lubricating oil discharge line 25, and the motor housing 31 and the speed increaser housing 32 are connected to the oil tank 23 via the lubricating oil discharge line 25. Refrigerant and lubricating oil are discharged.

The lubricating oil discharged to the oil tank 23 has a refrigerant dissolved therein and diluted with the refrigerant. The oil tank 23 is provided with a heater 27 (see FIG. 3) that evaporates the refrigerant in order to increase the concentration of the diluted lubricating oil. As the refrigerant evaporates, the lubricating oil returns to the state before dilution and can be repeatedly used as lubricating oil for lubricating the

gears

17 and 18 and the rolling bearing 14.

As shown in FIG. 3, the oil tank 23 is a container that can contain lubricating oil, and the lubricating oil is stored in a lower portion inside the oil tank 23.
The oil tank 23 can be roughly divided into a separation region 41 and a discharge region 42.

The oil tank 23 is formed with a lubricant / refrigerant inlet connected to the lubricant discharge line 25. The heater 27 is installed, for example, below the separation region 41 of the oil tank 23, heats the refrigerant and lubricating oil in the oil tank 23, and evaporates the refrigerant. As a result, the refrigerant gas generated by evaporation moves upward of the oil tank 23, and the lubricating oil having a reduced content of the refrigerant evaporated from the refrigerant flows downstream of the oil tank 23.

A lubricant outlet connected to the lubricant supply line 22 is formed below the oil tank 23. In the present embodiment, an oil pump 36 is installed at the lubricating oil outlet. Lubricating oil is supplied from the oil tank 23 to the turbo compressor 2 via the lubricating oil supply line 22.

A refrigerant gas outlet connected to the pressure equalizing pipe 29 is formed above the oil tank 23, and the refrigerant gas is supplied from the oil tank 23 to the evaporator 8 through the pressure equalizing pipe 29. Thereby, the refrigerant | coolant supplied to the turbo compressor 2 from the condenser 3 or the subcooler 4 is returned to a refrigerating cycle.
Further, one end of a pressure equalizing pipe 29 is connected to the oil tank 23, and the other end of the pressure equalizing pipe 29 is connected to the evaporator 8 of the refrigeration cycle. The pressure and the pressure in the oil tank 23 are almost equal. The connection destination of the pressure equalizing pipe 29 is not limited to the evaporator 8 and may be, for example, the suction port of the turbo compressor 2.

The lubricating oil stored in the oil tank 23 is preferably adjusted so as to be maintained within a predetermined temperature range. The temperature of the lubricating oil is determined based on, for example, the temperature at which appropriate lubrication is exerted in the

gears

17 and 18 of the turbo compressor 2 and the rolling bearing 14 that are lubricated by the lubricating oil.

The temperature of the lubricating oil stored in the oil tank 23 is adjusted by heating with the heater 27, for example. Heating by the heater 27 is controlled based on the temperature detected by the temperature detection unit 35 installed in the lower part of the oil tank 23. The heater 27 may be controlled to be turned on / off based on the detected temperature to adjust the heating to the refrigerant or the lubricating oil, or the set temperature of the heater 27 may be adjusted based on the detected temperature. Good.

The oil tank 23 is partitioned by a partition plate 43 and divided into a separation region 41 and a discharge region 42. The partition plate 43 is a plate-like member, and the side end portion contacts the inner side surface of the oil tank 23. As a result, the oil tank 23 is divided into two regions with the partition plate 43 as a boundary. On the lubricating oil discharge line 25 side of the partition plate 43 is a separation region 41 into which the lubricating oil returned from the housing 30 flows. Further, the lubricating oil supply line 22 side of the partition plate 43 is a discharge region 42 where the lubricating oil is supplied to the housing 30.

The separation region 41 is supplied with the lubricating oil in which the refrigerant is dissolved from the lubricating oil discharge line 25. The lubricating oil in which the refrigerant has dissolved has a higher specific gravity than the refrigerant alone or the lubricating oil alone, and has a high concentration at the bottom surface of the separation region 41. And the refrigerant | coolant is heated and gasified by the heater 27 arrange | positioned near the bottom face of the separation area | region 41 with a high refrigerant | coolant density | concentration, and it isolate | separates into lubricating oil and a refrigerant | coolant. In the oil tank 23, the space in which the lubricating oil is stored is limited by the partition plate 43, so that the lubricating oil can be efficiently heated by the heater 27.

In the separation region 41, a plurality of flow forming plates 44 other than the partition plate 43 described above may be provided. By installing the flow forming plate 44 in the separation region 41, the flow of the lubricating oil from the upper part to the lower part or the flow from the lower part to the upper part can be formed in the stored lubricating oil. Thereby, the lubricating oil can be efficiently brought into contact with the heater 27, or the separated and gasified refrigerant can be raised upward.

The heated and gasified refrigerant rises above the lubricating oil stored in the oil tank 23. Even when the forming phenomenon occurs, the foamed lubricating oil rises along the partition plate 43 and the flow forming plate 44, and then the foam floats on the liquid lubricating oil. Therefore, in the present embodiment, unlike the case where there is no partition plate 43 or flow forming plate 44, bubbles due to the refrigerant gas hardly flow to the downstream side inside the liquid lubricating oil. As a result, it is possible to prevent bubbles from being sucked into the oil tank 23.

The lubricating oil stored in the oil tank 23 is caused to flow in one direction by the oil pump 36, that is, from the lubricating oil / refrigerant inlet side to the lubricating oil outlet side. As a result, the lubricating oil whose refrigerant concentration is reduced due to the separation of the refrigerant flows toward the lubricating oil outlet side. Further, when the forming phenomenon occurs, bubbles floating on the lubricating oil also flow toward the downstream side along the flow of the lubricating oil.

When the oil level rises due to foaming due to the foaming phenomenon, the foam passes through the pressure equalizing pipe 29 and the foamed lubricating oil falls into the buffer tank 28.

In addition, the lower end part of the partition plate 43 or the flow forming plate 44 may be in contact with the bottom surface of the oil tank 23 or may be separated from the bottom surface. When in contact with the bottom surface, a flow from the lower part to the upper part is formed in the lubricating oil. When separated from the bottom surface, the lubricating oil in which the refrigerant has melted flows downstream without staying at the bottom in the separation region 41. At this time, the lubricating oil in which the refrigerant is dissolved flows along the heater 27, whereby the refrigerant can be efficiently gasified.

In the example shown in FIG. 3, the case where one partition plate 43 and two flow forming plates 44 are installed is illustrated, but the present invention is not limited to this example. For example, as shown in FIG. 4, one partition plate 43 and one flow forming plate 44 may be installed.

In the discharge area 42, an oil pump 36 is installed. The oil pump 36 is an immersion pump, for example, and is installed on the bottom surface of the oil tank 23. The oil pump 36 sucks the lubricating oil at the bottom of the oil tank 23 and supplies the lubricating oil to the outside, that is, the housing 30. In the present embodiment, when the foaming phenomenon occurs, the bubbles rise in the separation region 41, so that the oil pump 36 installed in the discharge region 42 is difficult to suck the refrigerant gas.

In addition, the heater 27 may be installed only in the upstream separation region 41, or may be installed in the downstream discharge region 42 as shown in FIG. In addition, by installing the heater 27 in the discharge region 42, the amount of refrigerant separated from the lubricating oil can be increased. However, if there is a possibility that a forming phenomenon may occur due to heating by the heater 27 in the discharge area 42, it is better not to install the heater 27 in the discharge area 42.

The buffer tank 28 is installed in the pressure equalizing pipe 29. The buffer tank 28 can store foamy lubricating oil flowing out from the oil tank 23 and has a capacity that prevents the lubricating oil from flowing out to the pressure equalizing pipe 29 on the downstream side. An inlet portion connected to a pressure equalizing pipe 29 connected to the oil tank 23 is formed in the upper portion of the buffer tank 28. Further, an outlet portion is formed at a portion different from the inlet portion at the upper portion of the buffer tank 28, and the outlet portion is connected to a pressure equalizing pipe 29 connected to the evaporator 8.

The refrigerant and lubricating oil that have flowed out of the oil tank 23 are supplied to the buffer tank 28 via the pressure equalizing pipe 29. Then, the lubricating oil flowing out from the oil tank 23 is temporarily stored in the buffer tank 28. In addition, the gasified refrigerant dissolved in the lubricating oil flows from the buffer tank 28 to the evaporator 8.

As a result, even if foaming occurs inside the oil tank 23 and the foam-like refrigerant and lubricating oil flow out of the oil tank 23, the lubricating oil is stored in the buffer tank 28 and does not flow to the refrigeration cycle, but only the refrigerant. Heads for the refrigeration cycle.

A return pipe 26 is connected below the oil tank 23. One end of the return pipe 26 is connected to the bottom surface of the buffer tank 28, for example, and the other end is connected to the oil tank 23. The return pipe 26 is provided separately from the pressure equalizing pipe 29 and returns the lubricating oil stored in the buffer tank 28 to the oil tank 23. As a result, the lubricating oil that has flowed out of the oil tank 23 and accumulated in the buffer tank 28 is returned to the oil tank 23 without flowing into the refrigerant cycle.

The position where the return pipe 26 is connected to the oil tank 23 is the side close to the position where the lubricating oil supply line 22 is connected in the oil tank 23. Thereby, the lubricating oil returned from the buffer tank 28 is returned to the vicinity of the position where the lubricating oil supply line 22 is connected in the oil tank 23, for example, to the discharge region 42. Even when forming occurs in the oil tank 23, it is mixed with lubricating oil not affected by the forming.

Next, a lubricating oil supply method and a cooling method in the turbo refrigerator 1 according to the present embodiment will be described.

Lubricating oil is stored in the oil tank 23 and is supplied from the oil tank 23 to the turbo compressor 2 by the oil pump 36. The lubricating oil supplied to the turbo compressor 2 is supplied to the

gears

17 and 18 and the rolling bearing 14 inside the motor housing 31 and the speed increaser housing 32 of the turbo compressor 2.

Lubricating oil supplied to the

gears

17 and 18 and the rolling bearing 14 rises in temperature due to friction loss while lubricating the

gears

17 and 18 and the rolling bearing 14.

The lubricating oil that has passed through the motor housing 31 and the speed increaser housing 32 of the turbo compressor 2 passes through the oil cooler 24 and is cooled. As a result, the lubricating oil that has passed through the

gears

17 and 18 and the rolling bearing 14 in the motor housing 31 and the speed increaser housing 32 of the turbo compressor 2 is cooled by the oil cooler 24.

Thereafter, the lubricating oil cooled by the oil cooler 24 and the refrigerant dissolved in the lubricating oil are discharged to the oil tank 23.

The lubricating oil and refrigerant discharged to the oil tank 23 flow downward in the separation region 41 and are heated by the heater 27 installed in the lower part of the oil tank 23, and the refrigerant evaporates. As a result, the kinematic viscosity of the lubricating oil diluted with the refrigerant is restored.

Lubricating oil in which the refrigerant has evaporated and the refrigerant content has decreased flows to the downstream side of the oil tank 23. Further, the refrigerant gas evaporated by the heater 27 is directed upward of the oil tank 23, and is supplied from the oil tank 23 through the pressure equalizing pipe 29 to the evaporator 8 through the pressure equalizing pipe 29 and the buffer tank 28. The

When the pressure in the oil tank 23 decreases due to a decrease in pressure in the refrigeration cycle and a foaming phenomenon occurs in which the lubricating oil bubbles due to the gasified refrigerant, the bubbles due to the refrigerant and the lubricating oil are separated from the partition plate 43. Alternatively, it rises along the flow forming plate 44. Further, the bubbles floating on the liquid lubricating oil flow toward the downstream side along the flow of the lubricating oil.

When the oil level due to the foam rises due to the foaming phenomenon, the foam passes through the pressure equalizing pipe 29, and the foam due to the refrigerant and the lubricating oil falls into the buffer tank 28. As a result, lubricating oil is stored in the lower part of the buffer tank 28, and the gasified refrigerant flows to the evaporator 8 through the pressure equalizing pipe 29.

As described above, according to the present embodiment, the refrigerant and the lubricating oil flowing out from the oil tank 23 are supplied to the buffer tank 28 via the pressure equalizing pipe 29, and the lubricating oil is temporarily stored in the buffer tank 28. Thereby, even if foaming occurs in the oil tank 23 and the refrigerant and the lubricating oil flow out of the oil tank 23, the lubricating oil is stored in the buffer tank 28 and does not flow to the refrigeration cycle, but only the refrigerant enters the refrigeration cycle. Head.

Further, the lubricating oil in which the refrigerant is dissolved is supplied to the separation region 41 of the oil tank 23, and the lubricating oil in which the refrigerant is dissolved in the separation region 41 is separated into the lubricating oil and the refrigerant. The separated lubricating oil is supplied from the separation region 41 to the discharge region 42 and supplied into the housing 30. Since the separation region 41 and the discharge region 42 are partitioned by the partition plate 43, the lubricating oil that has flowed into the oil tank 23 in the separation region 41 is different in the specific gravity of the lubricating oil and the refrigerant and the lubricating oil in a narrow space. It is efficiently separated by utilizing the temperature rise of Further, by installing the partition plate 43, it is possible to prevent the foamed lubricating oil from flowing toward the discharge region 42 even if the forming phenomenon occurs in the separation region 41.

From the above, the amount of lubricating oil flowing out to the refrigeration cycle such as the evaporator 8 can be reduced. Further, the amount of refrigerant sucked by the oil pump 36 can be reduced, and the amount of lubricating oil circulating in the lubricating oil system can be prevented from being reduced.

1: Turbo refrigerator 2: Turbo compressor 3: Condenser 4: Subcooler 5: First pressure reducing valve 6: Intermediate cooler 7: Second pressure reducing valve 8: Evaporator 9: Motor 10: Motor shaft 10a: One end 11: Rotating shaft 11a: one end 11b: other end 12: first stage impeller 13: second stage impeller 14: rolling bearing 15: compression mechanism 17: gear 18: gear 19: speed increasing mechanism 20: stator 21: rotor 22: Lubricating oil supply line 23: Oil tank 24: Oil cooler 25: Lubricating oil discharge line 26: Return pipe 27: Heater 28: Buffer tank 29: Pressure equalizing pipe 30: Housing 31: Motor housing 32: Booster housing 33: Compressor Housing 34: Refrigerant supply line 35: Temperature detector 36: Oil pump 41: Separation area 42: Discharge area 43: Partition Plate 44: Flow forming plate

Claims

An electric compressor having a compression mechanism driven by a motor, a condenser, an evaporator, and a refrigeration cycle in which refrigerant circulates;
An oil tank in which lubricating oil is stored;
A heater installed inside the oil tank for heating the lubricating oil;
An oil circulation pipe connected to the oil tank, supplying the lubricating oil from the oil tank to a housing containing the motor, and returning the lubricating oil from the housing to the oil tank;
Separate from the oil circulation pipe, one end is connected to the oil tank and the other end is connected to the refrigeration cycle.
A buffer tank that is installed in the pressure equalizing pipe, receives the refrigerant flowing out of the oil tank and the lubricating oil, and stores the lubricating oil;
A refrigerator equipped with.
2. The apparatus further comprises a return pipe having one end connected to the buffer tank and the other end connected to the oil tank separately from the pressure equalizing pipe to return the lubricating oil stored in the buffer tank to the oil tank. The refrigerator as described in.
The refrigerator according to claim 2, wherein the position where the return pipe is connected to the oil tank is in the vicinity of the position where the oil circulation pipe is connected to the oil tank.
4. The oil tank according to claim 1, wherein the oil tank is divided by a partition plate, and is divided into a separation region where the lubricating oil returned from the housing flows and a discharge region where the lubricating oil is supplied to the housing. The refrigerator according to any one of the above.
5. The refrigerator according to claim 4, wherein a flow forming plate that directs the flow of the lubricating oil stored in the oil tank from the upper part to the lower part or from the lower part to the upper part is installed in the separation region.
The refrigerator according to claim 4, wherein the partition plate is installed separately from the bottom surface of the oil tank.