Refrigeration cycle device

Abstract

A refrigeration cycle device (100) comprises: a main circuit (MC) having a compressor (1), a condenser (2), an expansion valve (3), an evaporator (4), a gas-liquid separator (5), and a suction pipe (SP); and an oil return path (RC) which is connected between the gas-liquid separator and the compressor and has an oil return pipe (RP), an open / close valve (6), an oil tank (7), and an oil equalizing pipe (OE) and a pressure equalizing pipe (PE). The gas-liquid separator has a first outflow port (53) for the outflow of a gas phase portion of a working medium and a second outflow port (54) for the outflow of a liquid phase portion of the working medium. The suction pipe connects the first outflow port and a suction port (13) of the compressor. The oil return pipe connects the second outflow port and the oil tank. The open / close valve opens and closes the oil return pipe. The volume of the oil tank is greater than the volume of the compressor. The oil equalizing pipe and the pressure equalizing pipe are connected in parallel between the oil tank and the compressor. The refrigeration cycle device further comprises a sensor (20) for detecting the degree of superheat of a refrigerant flowing through the suction pipe, and a control device (30) for controlling the opening degree of the open / close valve according to the degree of superheat detected by the sensor.

Description

Refrigeration cycle equipment

[0001] The present disclosure relates to a refrigeration cycle device.

[0002] Some refrigeration cycle devices are equipped with an oil return mechanism that stores an excess amount of refrigeration oil and returns the required amount to the compressor to prevent a shortage of lubricating oil (refrigeration oil) in the compressor.

[0003] The refrigeration cycle apparatus disclosed in Japanese Patent Laid-Open No. 2010-71568 (Patent Document 1) includes an oil return mechanism that includes an accumulator for separating and storing refrigeration oil discharged from the compressor together with the refrigerant, and an oil regulator for preventing excessive refrigeration oil from being returned from the accumulator to the compressor. The oil regulator is connected to the compressor via a suction pipe and a pressure equalizing pipe, and the pressure and oil level in the oil regulator are set to be equal to those in the compressor. When the oil level in the oil regulator falls below a specified level, a float valve provided in the oil regulator opens, and excess oil in the accumulator is supplied to the compressor via the oil regulator and the suction pipe.

[0004] JP 2010-71568 A

[0005] The oil return mechanism is a mechanism for ２ ) which uses a refrigerant whose operating pressure is higher than the withstand pressure of a general float valve.

[0006] A main object of the present disclosure is to provide a refrigeration cycle device that can avoid a shortage of refrigerating machine oil in a compressor and prevent oversupply of refrigerating machine oil to the compressor even when a refrigerant with a high operating pressure is used.

[0007] The refrigeration cycle apparatus of the present disclosure includes a main circuit having a compressor, a condenser, an expansion valve, an evaporator, a gas-liquid separator, and a suction pipe; and an oil return passage connected between the gas-liquid separator and the compressor, the oil return passage having an oil return pipe, an on-off valve, an oil tank, and an oil equalizing pipe and a pressure equalizing pipe. The compressor discharges a working medium containing a refrigerant and refrigeration oil. The gas-liquid separator is configured to separate the working medium flowing out from the evaporator into a gas phase portion and a liquid phase portion. The gas-liquid separator has a first outlet through which the gas phase portion of the working medium flows out and a second outlet through which the liquid phase portion of the working medium flows out. The suction pipe connects the first outlet to a suction port of the compressor. The oil return pipe connects the second outlet to an oil tank. The on-off valve opens and closes the oil return pipe. The volume of the oil tank is larger than the volume of the compressor. The oil equalizing pipe and the pressure equalizing pipe are connected in parallel between the oil tank and the compressor. The oil equalizing pipe is disposed below the pressure equalizing pipe. The refrigeration cycle device further includes a sensor for detecting the degree of superheat of the refrigerant flowing through the suction pipe, and a control device for controlling the opening degree of the on-off valve in accordance with the degree of superheat detected by the sensor.

[0008] According to the refrigeration cycle device of the present disclosure, even when a refrigerant with a high operating pressure is used, it is possible to avoid a shortage of refrigerating machine oil in the compressor and to prevent oversupply of refrigerating machine oil to the compressor.

[0009] It is a refrigerant circuit diagram of the refrigeration cycle device according to the embodiment. It is a diagram for explaining a first modified example of the refrigeration cycle device according to the embodiment. It is a diagram for explaining a second modified example of the refrigeration cycle device according to the embodiment.

[0010] Hereinafter, embodiments will be described with reference to the drawings. In the following, the same or corresponding parts will be denoted by the same reference numerals, and overlapping descriptions will not be repeated.

[0011] A configuration of a refrigeration cycle apparatus 100 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a refrigerant circuit diagram of the refrigeration cycle apparatus 100 according to the embodiment. The refrigeration cycle apparatus 100 according to the embodiment is, for example, a refrigerator.

[0012] The refrigerant circulating in the refrigeration cycle apparatus 100 is a refrigerant whose operating pressure is higher than the withstand pressure of a general float valve. From a different perspective, the refrigerant circulating in the refrigeration cycle apparatus 100 is a refrigerant whose operating pressure is higher than that of R410A. The operating pressure of the refrigerant is, for example, 5 MPa or higher, and may be 10 MPa or higher. The refrigerant is, for example, carbon dioxide (CO ２ )

[0013] 1, a refrigeration cycle apparatus 100 according to the present embodiment includes a main circuit MC and an oil return line RC. The oil return line RC branches off from the main circuit MC. The refrigeration cycle apparatus 100 according to the present embodiment also includes a sensor 20 and a control device 30.

[0014] The main circuit MC has a compressor 1, a condenser 2, an expansion valve 3, an evaporator 4, a gas-liquid separator 5, and a suction pipe SP. The main circuit MC is configured so that refrigerant flows through the compressor 1, condenser 2, expansion valve 3, evaporator 4, gas-liquid separator 5, and suction pipe SP in this order. The main circuit MC is configured by connecting the compressor 1, condenser 2, expansion valve 3, evaporator 4, and gas-liquid separator 5 via piping. The suction pipe SP is a piping that connects the gas-liquid separator 5 and the compressor 1 in the main circuit MC.

[0015] The oil return line RC branches off from the main circuit MC. The oil return line RC connects the gas-liquid separator 5 and the compressor 1. The oil return line RC has an oil return pipe RP, an on-off valve 6, an oil tank 7, an oil equalizing pipe OE, and a pressure equalizing pipe PE. The oil return line RC is configured so that refrigeration oil flows through the gas-liquid separator 5, the oil return pipe RP, the on-off valve 6, the oil tank 7, and the oil equalizing pipe OE in this order.

[0016] The compressor 1 compresses and discharges the drawn refrigerant. The compressor 1 includes a compressor main body (not shown) and a sealed container 11 that houses the compressor main body. The compressor main body includes an electric motor and a compression unit that is driven by the electric motor and compresses the refrigerant in the sealed container 11. The sealed container 11 has an inner bottom surface 11A extending horizontally and an inner side surface 11B extending in a direction intersecting the inner bottom surface 11A. The compressor main body is disposed on the inner bottom surface 11A of the sealed container 11. In this specification, the inner bottom surface 11A of the sealed container 11 is referred to as the inner bottom surface 11A of the compressor 1. The area of ​​the inner bottom surface 11A of the compressor 1 is smaller than the area of ​​the inner bottom surface 71A of the oil tank, which will be described later. In this specification, the suction volume of the compression unit is referred to as the volume of the compressor 1.

[0017] Refrigerating machine oil is stored in the compressor 1. The refrigerating machine oil acts as a lubricant for the compression section of the compressor 1. The compressor 1 discharges a working medium containing a refrigerant and refrigerating machine oil.

[0018] The compressor 1 has a discharge port 12 for discharging the working medium to the outside of the sealed container 11, a suction port 13 for drawing the refrigerant into the sealed container 11, an oil return port 14 for returning refrigeration oil to the inside of the sealed container 11, and a communication port 15 for allowing gas refrigerant to flow between the sealed container 11 and the oil tank 7. The discharge port 12 is connected to the condenser 2 via a discharge pipe. The suction port 13 is connected to the gas-liquid separator 5 via a suction pipe SP. The oil return port 14 is connected to the oil tank 7 via an oil equalizing pipe OE. The communication port 15 is connected to the oil tank 7 via a pressure equalizing pipe PE. The communication port 15 is arranged above the oil return port 14. The communication port 15 is arranged, for example, below the suction port 13. The refrigeration oil discharged from the discharge port 12 of the compressor 1 flows together with the refrigerant to the gas-liquid separator 5 in the main circuit MC, and then passes through the oil return line RC and is returned to the inside of the sealed container 11 from the oil return port 14 of the compressor 1.

[0019] An appropriate amount of refrigeration oil is set for the refrigeration oil stored in the compressor 1 in order to ensure normal operation of the compressor 1. A required minimum amount and an allowable maximum amount are set for the refrigeration oil stored in the compressor 1. In the refrigeration cycle device 100, the amount of refrigeration oil stored in the compressor 1 is maintained at or above the required minimum amount and below the allowable maximum amount. Preferably, the oil return port 14 is configured to be located below the oil level OL of the refrigeration oil when this minimum amount of refrigeration oil is stored in the sealed container 11. Preferably, the communication port 15 is configured to be located above the oil level OL of the refrigeration oil when this maximum amount of refrigeration oil is stored in the sealed container 11.

[0020] The compressor 1 may be a so-called two-stage compressor including a low-stage compression section that compresses a low-pressure refrigerant into an intermediate-pressure refrigerant and a high-stage compression section that compresses the intermediate-pressure refrigerant into a high-pressure refrigerant. In this case, the sum of the suction volumes of the compression sections is referred to as the volume of the compressor 1.

[0021] The condenser 2 is configured to condense the refrigerant discharged from the discharge port 12 of the compressor 1. The condenser 2 is, for example, a fin-and-tube heat exchanger having a plurality of fins and a heat transfer tube passing through the plurality of fins.

[0022] The expansion valve 3 is configured to reduce the pressure of the refrigerant flowing out from the condenser 2. The expansion valve 3 is, for example, a solenoid valve. The expansion valve 3 is capable of adjusting the flow rate of the refrigerant based on an instruction from, for example, the control device 30.

[0023] The evaporator 4 is configured to evaporate the refrigerant flowing out from the expansion valve 3. The evaporator 4 is, for example, a fin-and-tube heat exchanger having a plurality of fins and a heat transfer tube passing through the plurality of fins.

[0024] The gas-liquid separator 5 is configured to separate the working medium flowing out from the evaporator 4 into a gas phase portion and a liquid phase portion. The gas-liquid separator 5 may have any configuration as long as it can separate the working medium flowing out from the evaporator 4 into gas and liquid portions. The gas-liquid separator 5 shown in Figure 2 is an accumulator.

[0025] The gas phase portion of the working medium separated by the gas-liquid separator 5 is composed of gas refrigerant. The liquid phase portion of the working medium separated by the gas-liquid separator 5 contains refrigerating machine oil. The liquid phase portion of the working medium separated by the gas-liquid separator 5 is composed of, for example, liquid refrigerant and refrigerating machine oil.

[0026] The gas-liquid separator 5 has a container 51 capable of storing both the gas phase and liquid phase of the working medium, an inlet 52 through which the working fluid flowing out from the evaporator 4 flows into the container 51, a first outlet 53 through which the gas phase of the working medium flows out from the inside of the container 51 to the outside, and a second outlet 54 through which the liquid phase of the working medium flows out from the inside of the container 51 to the outside. The inlet 52 is arranged to face the inner circumferential surface of the container 51. The first outlet 53 is arranged above the second outlet 54.

[0027] The suction pipe SP connects the first outlet 53 of the gas-liquid separator 5 and the suction port 13 of the compressor 1. The suction pipe SP is configured to guide the gas phase portion of the working medium separated in the gas-liquid separator 5 to the compressor 1.

[0028] The oil return line RC is connected between the gas-liquid separator 5 and the compressor 1. The oil return line RC connects the second outlet 54 of the gas-liquid separator 5 and the oil return port 14 of the compressor 1. The oil return line RC has an oil return pipe RP, an on-off valve 6, an oil tank 7, an oil equalizing pipe OE, and a pressure equalizing pipe PE. The oil return line RC is configured so that refrigeration oil flows through the oil return pipe RP, the oil tank 7, and the oil equalizing pipe OE in this order. The gas-liquid separator 5, the on-off valve 6, the oil tank 7, and the compressor 1 are connected via piping to form the oil return line RC.

[0029] The oil return pipe RP is a pipe connecting the second outlet 54 of the gas-liquid separator 5 and the inlet 72 of the oil tank 7. The oil return pipe RP is configured to guide the liquid phase portion of the working medium separated in the gas-liquid separator 5 to the oil tank 7.

[0030] The on-off valve 6 opens and closes the oil return pipe RP. The on-off valve 6 is, for example, a solenoid valve. The on-off valve 6 is configured to be able to open and close the oil return pipe RP based on instructions from the control device 30.

[0031] The oil tank 7 is capable of storing refrigeration oil and liquid refrigerant. The volume of the oil tank 7 is larger than the volume of the compressor 1. The volume of the oil tank 7 is larger than the volume of the container 51 of the gas-liquid separator 5. The volume of the oil tank 7 is larger than the sum of the volume of the container 51 of the gas-liquid separator 5 and the volume of the portion of the oil return pipe RP that is located closer to the second outlet 52 of the gas-liquid separator 5 than the on-off valve 6.

[0032] In an initial state before the start of normal operation of the refrigeration cycle apparatus 100, the compressor 1 holds a necessary amount of refrigeration oil for lubrication, and the oil tank 7 holds an excess amount of refrigeration oil (excess oil). The amount of refrigeration oil stored in the oil tank 7 is greater than the amount of refrigeration oil stored in the compressor 1. Preferably, the oil tank 7 can store the entire amount of refrigeration oil contained in the main circuit MC and the oil return line RC. After the start of normal operation of the refrigeration cycle apparatus 100, when the on-off valve 6 is opened, the oil tank 7 stores the liquid refrigerant separated into gas and liquid in the gas-liquid separator 5 together with the refrigeration oil. During normal operation of the refrigeration cycle apparatus 100, the mass fraction of the refrigeration oil and liquid refrigerant stored in the oil tank 7 is higher than the mass fraction of the liquid refrigerant. The oil tank 7 has a volume large enough to prevent the refrigeration oil stored in the oil tank 7 from being diluted with the liquid refrigerant to an extent that it is no longer able to function as a lubricant. The volume of the oil tank 7 is, for example, two or more times, three or more times, or five or more times the volume of the compressor 1 .

[0033] The oil tank 7 has a container 71 capable of storing refrigeration oil and liquid refrigerant, an inlet 72 connected to the second outlet 54 of the gas-liquid separator 5 via an oil return pipe RP, a third outlet 73 connected to the oil return port 14 of the compressor 1 via an oil equalizing pipe OE, and a communication port 74 connected to the communication port 15 of the compressor 1 via a pressure equalizing pipe PE. The communication port 74 is disposed above the third outlet 73.

[0034] The container 71 has an inner bottom surface 71A extending horizontally and an inner side surface 71B extending in a direction intersecting the inner bottom surface 71A. The area of ​​the inner bottom surface 71A of the oil tank 7 is larger than the area of ​​the inner bottom surface 11A of the compressor 1. Preferably, the maximum dimension (width) of the inner bottom surface 71A of the oil tank 7 is larger than the maximum dimension (height) of the inner side surface 71B of the oil tank 7 in a direction perpendicular to the inner bottom surface 71A of the oil tank 7 (up-down direction).

[0035] The volume of the oil tank 7 is larger than the volume of a typical oil regulator. The area of ​​the inner bottom surface 71A of the oil tank 7 is larger than the area of ​​the inner bottom surface of a typical oil regulator.

[0036] The oil equalizing pipe OE and the pressure equalizing pipe PE are pipes that connect the oil tank 7 and the compressor 1 in parallel. The oil equalizing pipe OE is located lower than the pressure equalizing pipe PE. The oil equalizing pipe OE is configured to allow refrigeration oil containing liquid refrigerant to flow through it. The pressure equalizing pipe PE is configured to allow the gas phase portion (gas refrigerant) to flow through it. As a result, the oil equalizing pipe OE and the pressure equalizing pipe PE connect the oil tank 7 and the compressor 1 in parallel so that the liquid level LL of the refrigeration oil containing liquid refrigerant stored in the oil tank 7 is aligned with the oil level OL of the refrigeration oil stored in the compressor 1. In this specification, the phrase "the liquid level LL is aligned with the oil level OL" means that the liquid level LL and the oil level OL are located on the same plane.

[0037] An inner bottom surface 71A of the oil tank 7 is disposed on the same plane as, for example, an inner bottom surface 11A of the compressor 1. The height of the liquid level LL of the refrigerating machine oil and liquid refrigerant stored in the oil tank 7 is equal to the height of the oil level OL of the refrigerating machine oil stored in the compressor 1. The volume and shape of the oil tank 7 are configured so that the oil level OL and the liquid level LL do not exceed the height of the oil level OL when the maximum amount of refrigerating machine oil is stored in the sealed container 11.

[0038] The oil equalizing pipe OE is provided below the pressure equalizing pipe PE. The oil equalizing pipe OE and the pressure equalizing pipe PE are configured so as not to disturb the oil level in the compressor 1 and the liquid level in the oil tank 7 when refrigeration oil flows in and out between the oil tank 7 and the compressor 1 via the oil equalizing pipe OE and when gas-phase refrigerant flows in and out between the oil tank 7 and the compressor 1 via the pressure equalizing pipe PE. The oil equalizing pipe OE is configured to be located below the oil level in the compressor 1 and the liquid level in the oil tank 7 when the minimum amount of refrigeration oil is stored in the compressor 1. The pressure equalizing pipe PE is configured to be located above the oil level in the compressor 1 and the liquid level in the oil tank 7 when the maximum amount of refrigeration oil is stored in the compressor 1.

[0039] Sensor 20 is configured to detect the degree of superheat of the refrigerant flowing through suction pipe SP (hereinafter referred to as suction superheat). The suction superheat refers to the temperature difference between the temperature of the refrigerant suctioned by compressor 1 (hereinafter referred to as suction temperature) and the saturated gas temperature corresponding to the pressure of the refrigerant suctioned by compressor 1 (hereinafter referred to as suction pressure). Sensor 20 includes a temperature sensor that detects the suction temperature and a pressure sensor that detects the suction pressure. Sensor 20 outputs a measured signal to control device 30.

[0040] The control device 30 controls the opening degree of the on-off valve 6 in accordance with the suction superheat degree detected by the sensor 20. The control device 30 is configured to open the on-off valve 6 when the suction superheat degree detected by the sensor 20 decreases to a first determination value. The control device 30 is configured to maintain the on-off valve 6 in a closed state when the suction superheat degree detected by the sensor 20 is higher than the first determination value. The first determination value of the suction superheat degree for switching the on-off valve 6 from a closed state to an open state is, for example, 0 (zero). Note that the first determination value of the suction superheat degree may be any number greater than zero. The first determination value of the suction superheat degree may be set to any value that can suppress the occurrence of liquid backflow to the compressor 1 and prevent the occurrence of oversupply of oil to the compressor 1.

[0041] The control device 30 includes a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), etc. The CPU expands and executes a control program stored in the ROM.

[0042] Next, a description will be given of the operation of the refrigeration cycle apparatus 100. In the refrigeration cycle apparatus 100, the refrigerant mainly circulates through the main circuit MC, and the refrigerating machine oil circulates through an oil return circuit formed by a flow path in the main circuit MC connecting the discharge port 12 of the compressor 1 to the gas-liquid separator 5 and an oil return line RC.

[0043] The refrigerant that flows into the compressor 1 from the suction port 13 is compressed by the compressor 1 to become a high-temperature, high-pressure gas refrigerant, and is discharged together with refrigeration oil from the discharge port 12 of the compressor 1. The working medium that contains the gas refrigerant and refrigeration oil that is discharged from the discharge port 12 of the compressor 1 flows into the condenser 2. The gas refrigerant is condensed in the condenser 2 to become a liquid refrigerant, and flows out of the condenser 2 together with the refrigeration oil.

[0044] The working medium containing the liquid refrigerant and refrigerating machine oil flowing out of the condenser 2 flows into the expansion valve 3. The liquid refrigerant is decompressed by the expansion valve 3 to become a low-pressure gas-liquid two-phase refrigerant, which flows out from the expansion valve 3 together with the refrigerating machine oil. The working medium containing the gas-liquid two-phase refrigerant and refrigerating machine oil flowing out of the expansion valve 3 flows into the evaporator 4. The gas-liquid two-phase refrigerant is evaporated in the evaporator 4 to become a gas refrigerant, which flows out from the evaporator 4 together with the refrigerating machine oil.

[0045] The working medium containing gas refrigerant and refrigerating machine oil flowing out from the evaporator 4 flows into the gas-liquid separator 5, where it is separated into a gas phase portion containing gas refrigerant and a liquid phase portion containing liquid refrigerant and refrigerating machine oil.

[0046] The gas phase portion of the working medium separated in the gas-liquid separator 5 flows out from the first outlet 53 of the gas-liquid separator 5, passes through the suction pipe SP, and is sucked into the suction port 13 of the compressor 1. In this way, the refrigerant circulates through the main circuit MC of the refrigeration cycle apparatus 100.

[0047] The liquid phase portion of the working medium separated in the gas-liquid separator 5 is stored in the gas-liquid separator 5 when the on-off valve 6 is closed. When the on-off valve 6 is open, the liquid phase portion of the working medium separated in the gas-liquid separator 5 flows out from the second outlet 54 of the gas-liquid separator 5 and into the oil tank 7 via the oil return pipe RP.

[0048] In the refrigeration cycle apparatus 100, regardless of the open / close state of the on-off valve 6, the liquid level LL in the oil tank 7 is kept level with the oil level OL in the compressor 1. As a result, a sufficient amount of refrigeration oil is always stored in the compressor 1, and a shortage of refrigeration oil can be avoided.

[0049] The on-off valve 6 is in a closed state when the degree of intake superheat detected by the sensor 20 is higher than the first determination value. The on-off valve 6 is in an open state when the degree of intake superheat detected by the sensor 20 is equal to or lower than the first determination value.

[0050] When the suction superheat degree detected by the sensor 20 is higher than the first determination value, a sufficient amount of refrigerating machine oil is stored in the compressor 1, and liquid backflow, in which liquid refrigerant flows into the compressor 1, does not occur. Furthermore, in this state, the on-off valve 6 is closed. Therefore, the refrigerating machine oil separated from the gas refrigerant in the gas-liquid separator 5 is stored in the gas-liquid separator 5 and in a portion of the oil return pipe RP that is located closer to the second outlet 52 than the on-off valve 6. As a result, oversupply of oil to the compressor 1 can be suppressed.

[0051] On the other hand, the suction superheat decreases when the amount of refrigerant oil stored in the compressor 1 decreases, or when the amount of liquid refrigerant stored in the gas-liquid separator 5 increases, causing a decrease in the quality of the refrigerant flowing into the suction pipe SP from the first outlet 53. When it is detected that the suction superheat has decreased to or below the first judgment value, the on-off valve 6 is opened. As a result, while the on-off valve 6 is closed, the liquid refrigerant and refrigerant oil stored in the gas-liquid separator 5 and the oil return pipe RP located closer to the second outlet 52 than the on-off valve 6 flow into the oil tank 7 and mix with the refrigerant oil in the oil tank 7, causing the liquid level LL in the oil tank 7 to rise. Further, the refrigerant oil in the oil tank 7 is supplied to the compressor 1 until the oil level OL in the compressor 1 is equal to the liquid level LL in the oil tank 7. As a result, a shortage of refrigerant oil in the compressor 1 can be avoided. Furthermore, the volume of the oil tank 7 is larger than the sum of the volume of the container 51 of the gas-liquid separator 5 and the volume of the portion of the oil return pipe RP that is located closer to the second outlet 52 of the gas-liquid separator 5 than the on-off valve 6. Therefore, even if the entire amount of liquid refrigerant stored in the gas-liquid separator 5 and the portion of the oil return pipe RP that is located closer to the second outlet 52 than the on-off valve 6 flows into the oil tank 7 while the on-off valve 6 is closed, it is possible to avoid dilution of the refrigeration oil in the oil tank 7 and the compressor 1 by the liquid refrigerant.

[0052] The degree of suction superheat becomes higher than the first determination value due to the above-described effect caused by opening the on-off valve 6. After it is detected that the degree of suction superheat is higher than the first determination value, the on-off valve 6 is closed again.

[0053] <Modifications> As shown in Fig. 2, the gas-liquid separator 5 may be configured as an oil separator. Similar to the gas-liquid separator 5 shown in Fig. 1, the gas-liquid separator 5 shown in Fig. 2 has a container 51, an inlet 52, a first outlet 53, and a second outlet 54. The inlet 52 is disposed opposite the inner circumferential surface of the container 51. The first outlet 53 is disposed above the second outlet 54. The container 51 and the inlet 52 may be configured to cause the working fluid flowing out from the inlet 52 to flow spirally on the inner circumferential surface of the container 51, and to separate the refrigerating machine oil and the refrigerant by centrifugal forces applied to each of them.

[0054] 3, the gas-liquid separator 5 may be configured as a branch pipe. The gas-liquid separator 5 may be configured as, for example, a T-pipe. The gas-liquid separator 5 may also be configured as a Y-pipe.

[0055] The gas-liquid separator 5 shown in Fig. 3 has an inlet 52, a first outlet 53, and a second outlet 54, similar to the gas-liquid separator 5 shown in Fig. 1. The inlet 52 is arranged to face a portion of the inner circumferential surface of the T-shaped pipe or Y-shaped pipe that extends in the up-down direction between the first outlet 53 and the second outlet 54. The first outlet 53 is arranged above the second outlet 54. The first outlet 53 is arranged above the portion of the inner circumferential surface of the T-shaped pipe or Y-shaped pipe that faces the inlet 52. The second outlet 54 is arranged below the portion of the inner circumferential surface of the T-shaped pipe or Y-shaped pipe that faces the inlet 52.

[0056] <Effects> The oil return line RC of the refrigeration cycle apparatus 100 has an oil tank 7 with a volume larger than that of the compressor 1, instead of an oil regulator. Furthermore, in the refrigeration cycle apparatus 100, an oil equalization pipe OE and a pressure equalization pipe PE connect the oil tank 7 and the compressor 1 in parallel so that the liquid level LL of the refrigeration oil and liquid refrigerant stored in the oil tank 7 is equal to the oil level OL of the refrigeration oil stored in the compressor 1. Therefore, the refrigeration cycle apparatus 100 can avoid a shortage of refrigeration oil in the compressor 1 without using an oil regulator with a float valve. In other words, the refrigeration cycle apparatus 100 can avoid a shortage of refrigeration oil in the compressor 1 even when a refrigerant with a high operating pressure is used.

[0057] The refrigeration cycle apparatus 100 can employ a refrigerant having an operating pressure of 10 MPa or higher. The refrigeration cycle apparatus 100 can employ carbon dioxide as the refrigerant.

[0058] The refrigeration cycle apparatus 100 further includes a gas-liquid separator 5, an on-off valve 6 that opens and closes an oil return pipe RP that connects the second outlet 54 of the gas-liquid separator 5 and the inlet 72 of the oil tank 7, a sensor 20 that detects the superheat degree (suction superheat degree) of the refrigerant flowing through the suction pipe SP, and a control device 30 that controls the opening degree of the on-off valve 6 in accordance with the suction superheat degree detected by the sensor 20. As a result, the refrigeration cycle apparatus 100 can suppress over-oil supply and liquid backflow to the compressor 1 during normal operation, and can prevent breakdowns in the compressor 1.

[0059] As described above, the on-off valve 6 can be closed when the suction superheat degree is higher than the first determination value, thereby suppressing oversupply of oil to the compressor 1. Furthermore, the on-off valve 6 can be opened when the suction superheat degree falls to or below the first determination value, thereby suppressing liquid backflow to the compressor 1.

[0060] The first determination value of the suction superheat degree for switching the on-off valve 6 from the closed state to the open state may be zero. This can suppress the occurrence of liquid backflow to the compressor 1, compared to when the first determination value is less than zero.

[0061] Preferably, the oil tank 7 can store the entire amount of refrigeration oil contained in the main circuit MC and the oil return line RC. The volume of such oil tank 7 is sufficiently larger than the volume of the compressor 1, and the amount of refrigeration oil stored in the oil tank 7 is greater than the amount of refrigeration oil stored in the compressor 1. Therefore, even when the on-off valve 6 is closed, refrigeration oil can be supplied from the oil tank 7 to the compressor 1 via the oil equalization pipe OE, preventing a shortage of refrigeration oil in the compressor 1. Furthermore, during normal operation, it is possible to prevent the refrigeration oil stored in the oil tank 7 from being diluted with liquid refrigerant to such an extent that it is no longer able to function as a lubricant.

[0062] Preferably, the area of ​​the inner bottom surface 71A of the oil tank 7 is larger than the area of ​​the inner bottom surface 11A of the compressor 1. The maximum dimension of the inner bottom surface 71A of the oil tank 7 is larger than the maximum dimension of the inner side surface 71B of the oil tank 7 in a direction perpendicular to the inner bottom surface 71A of the oil tank 7. The volume of such an oil tank 7 is sufficiently larger than the volume of the compressor 1, and the amount of refrigeration oil stored in the oil tank 7 is greater than the amount of refrigeration oil stored in the compressor 1.

[0063] The gas-liquid separator 5 may be an accumulator, an oil separator, or a branch pipe. If the gas-liquid separator 5 is a branch pipe, the refrigeration cycle apparatus 100 can be made smaller than when the gas-liquid separator 5 is an accumulator or an oil separator.

[0064] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0065] 1 Compressor, 2 Condenser, 3 Expansion valve, 4 Evaporator, 5 Gas-liquid separator, 6 On-off valve, 7 Oil tank, 11 Sealed container, 11A Inner bottom surface, 11B Inner surface, 12 Discharge port, 13 Intake port, 14 Oil return port, 15 Communication port, 20 Sensor, 30 Control device, 51 Container, 52 Inlet, 53 First outlet, 54 Second outlet, 71 Container, 71A Inner bottom surface, 71B Inner surface, 72 Inlet, 73 Third outlet, 74 Communication port, 100 Refrigeration cycle device, LL Liquid level, MC Main circuit, OE Oil equalization pipe, OL Oil level, PE Pressure equalization pipe, RC Oil return path, RP Oil return pipe, SP Suction pipe.

Claims

1. A compressor comprising: a main circuit having a compressor, a condenser, an expansion valve, an evaporator, a gas-liquid separator, and a suction pipe; and an oil return passage connected between the gas-liquid separator and the compressor, the oil return passage having an oil return pipe, an on-off valve, an oil tank, an oil equalizing pipe, and a pressure equalizing pipe; the compressor discharges a working medium containing a refrigerant and a refrigeration oil; the gas-liquid separator is configured to separate the working medium discharged from the evaporator into a gas phase portion and a liquid phase portion, the gas-liquid separator having a first outlet through which the gas phase portion flows out and a second outlet through which the liquid phase portion flows out; the suction pipe connects between the first outlet and a suction port of the compressor; the oil return pipe connects between the second outlet and the oil tank; the on-off valve opens and closes the oil return pipe; the oil tank is capable of storing the liquid phase portion; and the volume of the oil tank is larger than the volume of the compressor; the oil equalizing pipe and the pressure equalizing pipe are connected in parallel to each other between the oil tank and the compressor, the oil equalizing pipe is arranged lower than the pressure equalizing pipe, and the refrigeration cycle apparatus further comprises a sensor for detecting a degree of superheat of the refrigerant flowing through the suction pipe, and a control device for controlling an opening degree of the on-off valve in accordance with the degree of superheat detected by the sensor.

2. The refrigeration cycle device according to claim 1, wherein the control device opens the on-off valve when the degree of superheat detected by the sensor falls below a judgment value.

3. The refrigeration cycle device according to claim 2, wherein the judgment value of the degree of superheat is zero.

4. A refrigeration cycle device according to any one of claims 1 to 3, wherein the oil tank is capable of storing the entire amount of refrigeration oil contained in the main circuit and the oil return line.

5. A refrigeration cycle device according to any one of claims 1 to 4, wherein the area of ​​the inner bottom surface of the oil tank is larger than the area of ​​the inner bottom surface of the compressor.

6. A refrigeration cycle device according to any one of claims 1 to 5, wherein the maximum dimension of the inner bottom surface of the oil tank is greater than the maximum dimension of the inner side surface of the oil tank in a direction perpendicular to the inner bottom surface of the oil tank.

7. A refrigeration cycle device according to any one of claims 1 to 6, wherein the gas-liquid separator is an accumulator.

8. A refrigeration cycle device according to any one of claims 1 to 6, wherein the gas-liquid separator is an oil separator.

9. A refrigeration cycle device according to any one of claims 1 to 6, wherein the gas-liquid separator is a branch pipe in which the first outlet is disposed higher than the second outlet.

10. A refrigeration cycle device according to any one of claims 1 to 9, wherein the refrigerant includes carbon dioxide.

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