JP7801967B2 - Refrigeration system - Google Patents

Description

This disclosure relates to a refrigeration system.

In refrigeration systems equipped with multiple compressors, each compressor is connected by an oil equalization pipe. The oil equalization pipes connected to multiple compressors supply refrigeration oil from compressors with a large amount of oil to compressors with a small amount, thereby equalizing the amount of refrigeration oil in each compressor.

For example, Patent Document 1 describes a refrigeration system in which two multi-stage compressors, each with a high-pressure compression element and a low-pressure compression element, are connected in parallel, and which has an oil return pipe as an oil equalization pipe to prevent uneven oil levels. The oil return pipe in Patent Document 1 returns refrigeration oil discharged from one compressor to the suction side of the other compressor. As a result, if an uneven amount of refrigeration oil accumulates in the compressors, the greater amount of refrigeration oil discharged from one compressor will return to the compressor with less refrigeration oil. As a result, unevenness in the amount of refrigeration oil accumulated in the compressors is prevented.

JP 2011-214757 A

However, in some cases, not only compressors but also compressor units each having an oil tank and a compressor are connected in parallel. In such a structure, oil does not circulate sequentially through each compressor and each oil tank. As a result, differences in the operating status of the compressors in each compressor unit can result in differences in the amount of oil stored in the oil tank. As a result, some oil tanks may not have enough oil to supply to the compressors, making it difficult to operate multiple compressor units stably and continuously.

The present disclosure has been made to solve the above-mentioned problems, and aims to provide a refrigeration system that can stably supply oil to all compressors in multiple compressor units.

In order to solve the above problem, the refrigeration system according to the present disclosure comprises a plurality of compressor units and an oil equalization pipe connecting the plurality of compressor units to one another, and each compressor unit comprises a low-pressure compressor that compresses a refrigerant, a high-pressure compressor that compresses the refrigerant compressed by the low-pressure compressor, an oil separator that separates lubricating oil from the refrigerant compressed by the high-pressure compressor, an oil tank that stores the lubricating oil separated by the oil separator, a main oil line connected to the oil tank and that discharges the oil stored in the oil tank, and a front oil equalization pipe. The compressor unit further includes a low-pressure oil line that connects the main oil line to the low-pressure compressor and sends the oil circulating through the main oil line to the low-pressure compressor, and a high-pressure oil line that connects the main oil line to the high-pressure compressor and sends the oil circulating through the main oil line to the high-pressure compressor, and the oil equalizer pipe connects the main oil lines of different compressor units to each other, and each compressor unit further includes a low-pressure valve arranged in the low-pressure oil line and a high-pressure valve arranged in the high-pressure oil line.

The refrigeration system disclosed herein allows for a stable supply of oil to all compressors in multiple compressor units.

1 is a diagram showing a schematic configuration of a refrigeration system according to a first embodiment of the present disclosure. FIG. 2 is a diagram showing a schematic configuration of a refrigeration system according to a second embodiment of the present disclosure.

Below, an embodiment of a refrigeration system according to the present disclosure will be described with reference to the accompanying drawings. However, the present disclosure is not limited to this embodiment.

First Embodiment
(Configuration of refrigeration system)
As shown in Fig. 1, the refrigeration system 1 includes a plurality of compressor units 2 (two in this embodiment) that compress a refrigerant. The refrigeration system 1 circulates the refrigerant compressed by the compressor units 2 between a cooling supply target such as an indoor unit. In this embodiment, the refrigerant is, for example, carbon dioxide (CO2). However, the refrigerant may be a refrigerant other than carbon dioxide.

In addition to multiple compressor units 2, the refrigeration system 1 mainly comprises a condenser 8 that condenses the refrigerant compressed by the compressor units 2, an evaporator 9 that evaporates the recovered refrigerant, an oil equalization pipe 10, and a control unit 200. Furthermore, in the refrigeration system 1, the multiple compressor units 2 are connected in parallel. Therefore, the multiple compressor units 2 can be operated simultaneously under not only the same operating conditions, but also different operating conditions.

In this embodiment, the refrigeration system 1 includes multiple compressor units 2, including a first compressor unit 2A and a second compressor unit 2B. The first compressor unit 2A and the second compressor unit 2B have the same configuration. Therefore, hereinafter, the first compressor unit 2A and the second compressor unit 2B will be simply referred to as compressor units 2.

The compressor unit 2 of this embodiment mainly comprises a low-pressure compressor 3, an intercooler 4, a high-pressure compressor 5, an oil separator 6, an oil tank 7, a main oil line 70, a low-pressure oil line 30, a high-pressure oil line 50, a low-pressure valve 39, and a high-pressure valve 59.

In the compressor unit 2, the refrigerant flows from the low-pressure compressor 3 toward the oil separator 6. Hereinafter, in the direction of refrigerant flow in the compressor unit 2, the side where the low-pressure compressor 3 is located relative to the intercooler 4 is referred to as the upstream side, and the side where the high-pressure compressor 5 is located relative to the intercooler 4 is referred to as the downstream side.

The low-pressure compressor 3 compresses the gas refrigerant supplied from the evaporator 9 in multiple stages (two stages in this embodiment). In this embodiment, the low-pressure compressor 3 is a two-stage compressor equipped with a low-pressure rotary compression mechanism 31 and a low-pressure scroll compression mechanism 32 in series. The low-pressure rotary compression mechanism 31 compresses the gas refrigerant supplied from outside the low-pressure compressor 3. The low-pressure scroll compression mechanism 32 further compresses the refrigerant compressed by the low-pressure rotary compression mechanism 31. The refrigerant compressed by the low-pressure scroll compression mechanism 32 is sent to the intercooler 4. The low-pressure compressor 3 also includes a low-pressure oil level sensor (oil sensor) 33. The low-pressure oil level sensor 33 is a sensor capable of measuring the amount of oil (refrigeration oil) stored inside the low-pressure compressor 3. The low-pressure oil level sensor 33 detects the oil level inside the casing (not shown) of the low-pressure compressor 3. The low-pressure oil level sensor 33 sends a signal to the control unit 200 when the oil level reaches or leaves the detectable range.

The intercooler 4 is disposed between the low-pressure compressor 3 and the high-pressure compressor 5. The intercooler 4 is disposed downstream of the low-pressure compressor 3 in the direction of refrigerant flow. The intercooler 4 cools the refrigerant compressed by the low-pressure compressor 3. In this embodiment, the intercooler 4 is, for example, an air-cooled type.

The high-pressure compressor 5 is located downstream of the intercooler 4 in the refrigerant flow direction. The high-pressure compressor 5 further compresses the gas refrigerant compressed by the low-pressure compressor 3 and then cooled by the intercooler 4 in multiple stages (two stages in this embodiment). In this embodiment, the high-pressure compressor 5 is a two-stage compressor equipped with a high-pressure rotary compression mechanism 51 and a high-pressure scroll compression mechanism 52 in series. The high-pressure rotary compression mechanism 51 compresses refrigerant supplied from outside the high-pressure compressor 5. The high-pressure scroll compression mechanism 52 further compresses the refrigerant compressed by the high-pressure rotary compression mechanism 51. The refrigerant compressed by the high-pressure rotary compression mechanism 51 is sent to the oil separator 6. The high-pressure compressor 5 also includes a high-pressure oil level sensor (oil sensor) 53. The high-pressure oil level sensor 53 is a sensor capable of measuring the amount of oil (refrigeration oil) stored inside the high-pressure compressor 5. The high-pressure oil level sensor 53 detects the height of the oil level inside the casing (not shown) of the high-pressure compressor 5. The high-pressure oil level sensor 53 issues a signal to the control unit 200 when the oil level position reaches or leaves the detectable range.

The oil separator 6 is located downstream of the high-pressure compressor 5 in the refrigerant flow direction. The oil separator 6 separates the oil (refrigeration oil) contained in the refrigerant compressed by the high-pressure compressor 5. The refrigerant that passes through the oil separator 6 is sent to the condenser 8, which is located downstream of the compressor unit 2 in the flow direction.

The oil tank 7 is located downstream of the oil separator 6 in the direction of refrigerant flow. The oil separated by the oil separator 6 is discharged into the oil tank 7. The oil tank 7 stores the oil sent from the oil separator 6.

The main oil line 70 is a pipe connected to the oil tank 7. The main oil line 70 is connected to the bottom of the oil tank 7 and discharges the oil stored in the oil tank 7 to the outside of the oil tank 7. The main oil line 70 is directly connected to the bottom of the oil tank 7.

The low-pressure oil line 30 is a pipe that connects the main oil line 70 and the low-pressure compressor 3. The low-pressure oil line 30 sends oil circulating through the main oil line 70 to the low-pressure compressor 3. The low-pressure oil line 30 is directly connected to the main oil line 70.

The high-pressure oil line 50 is a pipe that connects the main oil line 70 and the high-pressure compressor 5. The low-pressure oil line 30 sends oil circulating through the main oil line 70 to the high-pressure compressor 5. The high-pressure oil line 50 is directly connected to the main oil line 70. The low-pressure oil line 30, high-pressure oil line 50, and main oil line 70 are connected at connection position C.

The low-pressure valve 39 is disposed in the low-pressure oil line 30. The low-pressure valve 39 is capable of switching the opening degree of the low-pressure oil line 30 based on a signal from the control unit 200. In this embodiment, the low-pressure valve 39 is an on-off valve that can be switched between a fully open state, which allows oil flowing through the low-pressure oil line 30 toward the low-pressure compressor 3, and a fully closed state, which prevents oil from flowing through the low-pressure oil line 30. The low-pressure valve 39 is disposed downstream in the flow direction (closer to the low-pressure compressor 3) from the connection position C.

The high-pressure valve 59 is disposed in the high-pressure oil line 50. The high-pressure valve 59 is capable of switching the opening degree of the high-pressure oil line 50 based on a signal from the control unit 200. In this embodiment, the high-pressure valve 59 is an on/off valve that can be switched between a fully open state, which allows oil flowing through the high-pressure oil line 50 toward the high-pressure compressor 5, and a fully closed state, which prevents oil from flowing through the high-pressure oil line 50. The high-pressure valve 59 is disposed downstream in the flow direction (closer to the high-pressure compressor 5) from connection position C.

The condenser 8 is a condenser that condenses the refrigerant compressed by the compressor unit 2. The condenser 8 is located downstream of the oil separator 6 in the refrigerant flow direction. In this embodiment, only one condenser 8 is located for each of the compressor units 2. The condenser 8 is, for example, an air-cooled heat exchanger that exchanges heat between the refrigerant and external air. The high-temperature, high-pressure gas refrigerant generated by the high-pressure compressor 5 is condensed as it passes through the condenser 8, becoming a high-temperature, high-pressure liquid refrigerant. The refrigerant condensed in the condenser 8 is sent to the evaporator 9 via a receiver (not shown), an expansion valve (not shown), etc.

The evaporator 9 generates low-temperature, low-pressure gas refrigerant to be supplied to the compressor unit 2. The evaporator 9 is located upstream of the low-pressure compressor 3 in the refrigerant flow direction. In this embodiment, the evaporators 9 are located separately for each of the compressor units 2. That is, two evaporators 9 are provided in this embodiment, the same number as the compressor units 2. The evaporator 9 is, for example, an air-cooled heat exchanger that exchanges heat between the refrigerant and external air. The low-temperature, low-pressure liquid refrigerant that has passed through an expansion valve or the like evaporates by exchanging heat with external air as it passes through the evaporator 9, becoming a low-temperature, low-pressure gas refrigerant. The low-temperature, low-pressure gas refrigerant is supplied to the low-pressure compressor 3 of the compressor unit 2.

The oil equalization pipe 10 connects multiple compressor units 2 to each other. Specifically, the oil equalization pipe 10 connects the main oil lines 70 of different compressor units 2 between the connection position C and the oil tank 7. Therefore, the oil equalization pipe 10 of this embodiment connects the main oil line 70 of the first compressor unit 2A to the main oil line 70 of the second compressor unit 2B. The first end (one end) of the oil equalization pipe 10 is connected between the connection position C of the first compressor unit 2A and the oil tank 7. The second end (the end opposite to the first end) of the oil equalization pipe 10 is connected between the connection position C of the second compressor unit 2B and the oil tank 7. As a result, the oil equalization pipe 10 is connected to the first compressor unit 2A and the second compressor unit 2B downstream of the oil tank 7 in the flow direction and upstream of the low-pressure oil line 30 and the high-pressure oil line 50 in the flow direction. The oil equalization pipe 10 of this embodiment is a linear pipe that maintains the same diameter.

The control unit 200 adjusts the opening degrees of the low-pressure valve 39 and the high-pressure valve 59 based on information from the low-pressure oil level sensor 33 and the high-pressure oil level sensor 53. In this embodiment, the control unit 200 collectively controls the first compressor unit 2A and the second compressor unit 2B. Specifically, the control unit 200 acquires information on the oil level position in each compressor from the low-pressure oil level sensor 33 and the high-pressure oil level sensor 53 of the first compressor unit 2A and the low-pressure oil level sensor 33 and the high-pressure oil level sensor 53 of the second compressor unit 2B. Based on the acquired oil level position information, the control unit 200 switches the low-pressure valve 39 and the high-pressure valve 59 corresponding to the compressor in which the sensor that sent the information is located to either a fully open state or a fully closed state. Here, "corresponding" means that the low-pressure oil level sensor 33 or the high-pressure oil level sensor 53 that sent the information is located.

More specifically, the control unit 200 acquires information about the oil level position inside the low-pressure compressor 3 and the high-pressure compressor 5 based on signals sent from the low-pressure oil level sensor 33 and the high-pressure oil level sensor 53 when the oil level position reaches or leaves the detectable range. If the acquired oil level position information indicates that the oil level position has reached the detectable range, the control unit 200 sends an instruction to the corresponding low-pressure valve 39 or high-pressure valve 59 to fully close. If the acquired oil level position information indicates that the oil level position has left the detectable range, the control unit 200 sends an instruction to the corresponding low-pressure valve 39 or high-pressure valve 59 to fully open.

(Action and effect)
In the refrigeration system 1 configured as described above, a plurality of compressor units 2 are connected in parallel. In each compressor unit 2, gas refrigerant generated in the evaporator 9 is supplied to the low-pressure compressor 3. The gas refrigerant supplied to the low-pressure compressor 3 flows sequentially through the low-pressure rotary compression mechanism 31 and the low-pressure scroll compression mechanism 32, and is compressed in two stages. The gas refrigerant compressed by the low-pressure compressor 3 is sent to the intercooler 4 and cooled. The gas refrigerant cooled by the intercooler 4 is then supplied to the high-pressure compressor 5. The gas refrigerant supplied to the high-pressure compressor 5 flows sequentially through the high-pressure rotary compression mechanism 51 and the high-pressure scroll compression mechanism 52, and is compressed in two stages. The gas refrigerant compressed by the high-pressure compressor 5 is sent to the oil separator 6, where oil contained in the gas refrigerant is separated. The gas refrigerant from which the oil has been separated is sent to the condenser 8 and supplied to a refrigerant supply target. The refrigerant that has undergone heat exchange in the refrigerant supply target is returned to the compressor unit 2 and sent to the evaporator 9 via a receiver (not shown), an expansion valve (not shown), etc. The refrigerant sent to the evaporator 9 evaporates to become a low-temperature, low-pressure gas refrigerant. The low-temperature, low-pressure gas refrigerant is supplied again to the low-pressure compressor 3 of the compressor unit 2. In this way, the refrigerant is circulated to the compressor unit 2 in the refrigeration system 1.

The oil separated by the oil separator 6 is sent to the oil tank 7 and stored there. The oil sent to the oil tank 7 is returned to the low-pressure compressor 3 through the main oil line 70 and the low-pressure oil line 30 only when the low-pressure valve 39 is fully open. A portion of the oil passing through the main oil line 70 is returned to the high-pressure compressor 5 through the main oil line 70 and the high-pressure oil line 50 only when the high-pressure valve 59 is fully open. The oil passing through the main oil line 70 is sent to another main oil line 70 through the oil equalizer 10. In other words, a portion of the oil passing through the main oil line 70 of the first compressor unit 2A is sent to the main oil line 70 of the second compressor unit 2B through the oil equalizer 10. A portion of the oil passing through the main oil line 70 of the second compressor unit 2B is sent to the main oil line 70 of the first compressor unit 2A through the oil equalizer 10.

In this manner, in the refrigeration system 1 of this embodiment, the main oil line 70 of the first compressor unit 2A and the main oil line 70 of the second compressor unit 2B are connected by an oil equalization pipe 10. Therefore, oil accumulated in the oil tank 7 of the first compressor unit 2A can flow not only into the main oil line 70 of the first compressor unit 2A but also into the main oil line 70 of the second compressor unit 2B. Similarly, oil accumulated in the oil tank 7 of the second compressor unit 2B can flow not only into the main oil line 70 of the second compressor unit 2B but also into the main oil line 70 of the first compressor unit 2A. In addition, in each compressor unit 2, a low-pressure valve 39 is disposed in the low-pressure oil line 30, and a high-pressure valve 59 is disposed in the high-pressure oil line 50. Therefore, the amount (flow state) of oil flowing from the main oil line 70 and low-pressure oil line 30 to the low-pressure compressor 3 can be adjusted by the low-pressure valve 39. Similarly, the amount of oil flowing from the main oil line 70 and high-pressure oil line 50 to the high-pressure compressor 5 (flow state) can be adjusted by the high-pressure valve 59. As a result, oil stored in different oil tanks 7 can be supplied to any compressor by switching the opening of the low-pressure valve 39 and high-pressure valve 59. Therefore, regardless of the operating status of multiple compressors, it is possible to stop the supply of oil to a compressor with a large amount of oil and start the supply of oil to a compressor with little oil. This allows a stable supply of oil to all compressors in multiple compressor units 2.

The control unit 200 also switches the opening degree of the low-pressure valve 39 and the high-pressure valve 59 based on information on the oil level position from the low-pressure oil level sensor 33 and the high-pressure oil level sensor 53 of each compressor unit 2. Therefore, if there is a low-pressure compressor 3 or a high-pressure compressor 5 in each compressor unit 2 that is short of oil, the low-pressure valve 39 and the high-pressure valve 59 can be automatically opened to supply oil to the low-pressure compressor 3 or the high-pressure compressor 5 that is short of oil. Similarly, if there is a low-pressure compressor 3 or a high-pressure compressor 5 in each compressor unit 2 that is excessively oil-accumulating, the low-pressure valve 39 and the high-pressure valve 59 can be automatically closed to supply oil to the low-pressure compressor 3 or the high-pressure compressor 5 that is excessively oil-accumulating. In this way, the amount of oil in each compressor can be automatically adjusted by the control unit 200. Therefore, in multiple compressor units 2, oil can be supplied to all compressors so that the amount of oil accumulated therein is approximately uniform.

Second Embodiment
Next, a second embodiment of the refrigeration system 1B according to the present disclosure will be described. In the second embodiment described below, components common to the first embodiment will be denoted by the same reference numerals in the drawings and will not be described again. The second embodiment differs from the first embodiment in that it includes an adjustable on-off valve 101.

The refrigeration system 1B of the second embodiment further includes an adjusting on-off valve 101 arranged midway through the oil equalization pipe 10. The adjusting on-off valve 101 is capable of switching the opening degree of the oil equalization pipe 10 based on a signal from the control unit 200B. The adjusting on-off valve 101 of this embodiment is an on-off valve that can be switched between a fully open state, which allows oil to flow through the oil equalization pipe 10, and a fully closed state, which prevents oil from flowing through the oil equalization pipe 10.

In the second embodiment, the control unit 200B adjusts the opening degree of not only the low-pressure valve 39 and the high-pressure valve 59 but also the regulating on-off valve 101 based on information from the low-pressure oil level sensor 33 and the high-pressure oil level sensor 53. The control unit 200B acquires information on the oil level position in each compressor from the low-pressure oil level sensor 33 and the high-pressure oil level sensor 53 of the first compressor unit 2A and the low-pressure oil level sensor 33 and the high-pressure oil level sensor 53 of the second compressor unit 2B. Based on the acquired oil level information, the control unit 200B acquires information on the total oil volume for the low-pressure compressor 3 and the high-pressure compressor 5 of the first compressor unit 2A, and information on the total oil volume for the low-pressure compressor 3 and the high-pressure compressor 5 of the second compressor unit 2B. Based on the information on the total oil volume for each compressor unit 2, the control unit 200B sends an instruction to the regulating on-off valve 101 to fully open if the oil volume in one of the compressor units 2 is low or excessive. Furthermore, if the amount of oil in all compressor units 2 is appropriate, the control unit 200B sends an instruction to the regulating on-off valve 101 to fully close it.

(Action and effect)
In the refrigeration system 1B configured as described above, the regulating on-off valve 101 switches the oil flow state in the oil equalization pipe 10. Therefore, it is possible to stop the supply of oil between the first compressor unit 2A and the second compressor unit 2B. Therefore, when it is desired to operate only one compressor unit 2, it is possible to prevent oil from being supplied to the compressor unit 2 that is not operating. As a result, among the multiple compressor units 2, stable operation is possible even with only some of the compressor units 2.

(Other embodiments)
The above describes in detail the embodiments of the present disclosure with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present disclosure.

In addition, the configuration of the refrigeration systems 1 and 1B other than the compressor unit 2 is not limited in any way and can be changed as appropriate.

Furthermore, the low-pressure compressor 3 and the high-pressure compressor 5 are not limited to being two-stage compressors. The low-pressure compressor 3 and the high-pressure compressor 5 may be multi-stage compressors with three or more stages, or may be single-stage compressors with only one stage. The low-pressure compressor 3 and the high-pressure compressor 5 are not limited to being structured with a rotary compression mechanism and a scroll compression mechanism. For example, the low-pressure compressor 3 and the high-pressure compressor 5 may have multiple stages of only a rotary compression mechanism, or may have multiple stages of only a scroll compression mechanism.

The compressor unit 2 and the refrigeration system 1, 1B may further include a receiver (not shown) that recovers liquid refrigerant from the refrigerant condensed in the condenser 8, an expansion valve (not shown) that adiabatically expands the liquid refrigerant recovered in the receiver to reduce its pressure and evaporate part of the liquid, thereby bringing the refrigerant into a two-phase gas-liquid state, and an economizer (not shown) that separates the refrigerant that has been brought into a two-phase gas-liquid state in the expansion valve into a gas phase and a liquid phase.

Furthermore, the low pressure valve 39 and the high pressure valve 59 are not limited to being on/off valves or solenoid valves. The low pressure valve 39 and the high pressure valve 59 may be valves whose opening degree can be adjusted as desired, or may be valves whose opening degree is adjusted manually rather than by the control units 200 and 200B. If the low pressure valve 39 and the high pressure valve 59 are not on/off valves but valves whose opening degree can be adjusted as desired, the control units 200 and 200B may send instructions to adjust the valve opening degree appropriately.

Furthermore, the evaporator 9 is not limited to being arranged separately for multiple compressor units 2. For example, only one evaporator 9 may be arranged for multiple compressor units 2.

Furthermore, the capacitor 8 is not limited to being arranged in a single manner for multiple compressor units 2. For example, the capacitors 8 may be arranged separately for multiple compressor units 2.

<Additional Notes>
The refrigeration systems 1 and 1B described in each embodiment can be understood, for example, as follows.

(1) The refrigeration system 1, 1B according to the first aspect comprises a plurality of compressor units 2 connected in parallel and an oil equalization pipe 10 connecting the plurality of compressor units 2 to one another, and each compressor unit 2 comprises a low-pressure compressor 3 that compresses a refrigerant, a high-pressure compressor 5 that compresses the refrigerant compressed by the low-pressure compressor 3, an oil separator 6 that separates oil from the refrigerant compressed by the high-pressure compressor 5, an oil tank 7 that stores the oil separated by the oil separator 6, a main oil line 70 connected to the oil tank 7 and discharging the oil stored in the oil tank 7, and a main oil line 70 connected to the main oil tank 7 that discharges the oil stored in the main oil tank 7. The compressor unit 2 further includes a low-pressure oil line 30 that connects the main oil line 70 to the low-pressure compressor 3 and sends the oil flowing through the main oil line 70 to the low-pressure compressor 3, and a high-pressure oil line 50 that connects the main oil line 70 to the high-pressure compressor 5 and sends the oil flowing through the main oil line 70 to the high-pressure compressor 5. The oil equalization pipe 10 connects the main oil lines 70 of different compressor units 2 to each other, and each compressor unit 2 further includes a low-pressure valve 39 arranged in the low-pressure oil line 30 and a high-pressure valve 59 arranged in the high-pressure oil line 50.

This connects the main oil line 70 of one compressor unit 2 to the main oil line 70 of another compressor unit 2 via the oil equalization pipe 10. Therefore, oil stored in the oil tank 7 of one compressor unit 2 can flow not only into the main oil line 70 of that compressor unit 2, but also into the main oil lines 70 of the other compressor units 2. Additionally, each compressor unit 2 has a low-pressure valve 39 disposed in the low-pressure oil line 30 and a high-pressure valve 59 disposed in the high-pressure oil line 50. Therefore, the amount of oil flowing from the low-pressure oil line 30 to the low-pressure compressor 3 (flow state) can be adjusted by the low-pressure valve 39. Similarly, the amount of oil flowing from the high-pressure oil line 50 to the high-pressure compressor 5 (flow state) can be adjusted by the high-pressure valve 59. This allows oil stored in different oil tanks 7 to be supplied to any compressor by switching the opening of the low-pressure valve 39 and the high-pressure valve 59. Therefore, regardless of the operating status of multiple compressors, it is possible to stop the supply of oil to compressors with a large amount of oil and start the supply of oil to compressors with a small amount of oil. This allows for a stable supply of oil to all compressors in multiple compressor units 2.

(2) The refrigeration system 1, 1B according to the second aspect is the refrigeration system 1, 1B of (1), wherein the low-pressure compressor 3 and the high-pressure compressor 5 have oil sensors capable of measuring the amount of oil stored therein, and further include control units 200, 200B that adjust the opening degrees of the low-pressure valve 39 and the high-pressure valve 59 based on information from the oil sensors.

As a result, if there is a low-pressure compressor 3 or high-pressure compressor 5 in each compressor unit 2 that is short of oil, the low-pressure valve 39 and high-pressure valve 59 for supplying oil to the low-pressure compressor 3 or high-pressure compressor 5 that is short of oil can be automatically opened. Similarly, if there is a low-pressure compressor 3 or high-pressure compressor 5 in each compressor unit 2 that has an excess of oil accumulated, the low-pressure valve 39 and high-pressure valve 59 for supplying oil to the low-pressure compressor 3 or high-pressure compressor 5 that has an excess of oil accumulated can be automatically closed. In this way, the amount of oil in each compressor can be automatically adjusted by the control units 200, 200B. Therefore, in multiple compressor units 2, oil can be supplied to all compressors so that the amount of accumulated oil is as uniform as possible.

(3) The refrigeration system 1 according to the third aspect is the refrigeration system 1 or 1B according to (1) or (2), further comprising an adjustment on-off valve 101 arranged midway along the oil equalization pipe 10.

This allows the supply of oil between multiple compressor units 2 to be stopped. Therefore, if you want to operate only one compressor unit 2, it is possible to prevent oil from being supplied to the compressor unit 2 that is not operating. This allows stable operation of multiple compressor units 2 even with only some of the compressor units 2.

DESCRIPTION OF SYMBOLS 1, 1B... Refrigeration system 2... Compressor unit 3... Low-pressure compressor 31... Low-pressure rotary compression mechanism 32... Low-pressure scroll compression mechanism 33... Low-pressure oil level sensor 4... Intercooler 5... High-pressure compressor 51... High-pressure rotary compression mechanism 52... High-pressure scroll compression mechanism 53... High-pressure oil level sensor 6... Oil separator 7... Oil tank 70... Main oil line 30... Low-pressure oil line 50... High-pressure oil line 39... Low-pressure valve 59... High-pressure valve C... Connection position 2A... First compressor unit 2B... Second compressor unit 10... Oil equalization pipe 8... Condenser 9... Evaporator 200, 200B... Control unit 101... Adjustable opening/closing valve

Claims (3)

a plurality of compressor units connected in parallel;
an oil equalization pipe connecting the plurality of compressor units to each other,
Each compressor unit is
a low-pressure compressor that compresses a refrigerant;
a high-pressure compressor that compresses the refrigerant compressed by the low-pressure compressor;
an oil separator that separates oil from the refrigerant compressed by the high-pressure compressor;
an oil tank that stores the oil separated by the oil separator;
a main oil line connected to the oil tank and discharging the oil stored in the oil tank;
a low-pressure oil line connecting the main oil line and the low-pressure compressor and sending the oil flowing through the main oil line to the low-pressure compressor;
a high-pressure oil line connecting the main oil line and the high-pressure compressor and sending the oil flowing through the main oil line to the high-pressure compressor,
the oil equalization pipe connects the main oil lines in different compressor units to each other;
Each compressor unit further includes a low pressure valve disposed in the low pressure oil line and a high pressure valve disposed in the high pressure oil line. The low-pressure compressor and the high-pressure compressor each have an oil sensor capable of measuring the amount of oil stored therein,
The refrigeration system according to claim 1 , further comprising a control unit that adjusts the opening degrees of the low-pressure valve and the high-pressure valve based on information from the oil sensor. The refrigeration system of claim 1 or claim 2, further comprising an adjustable on-off valve disposed midway along the oil equalization pipe.