Refrigeration cycle device

Abstract

A refrigeration cycle device (1001) comprises a compressor (10), an oil separator (11), a first heat exchanger (13), an expansion valve (14), and a second heat exchanger (15). The compressor (10), the oil separator (11), the first heat exchanger (13), the expansion valve (14), and the second heat exchanger (15) constitute a refrigerant circuit (C1) through which a refrigerant circulates. The refrigeration cycle device (1001) further comprises: an oil return path (RP) that returns refrigerator oil from the oil separator (11) to an intake part of the compressor (10); a flow rate regulation mechanism (16) disposed in the oil return path (RP); and an oil quantity detection device (17) that detects the quantity of refrigerator oil stored in the oil separator (11). The flow rate regulation mechanism (16) controls the flow rate of fluid passing through the oil return path (RP) in response to the output of the oil quantity detection device (17).

Description

Refrigeration cycle equipment

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

[0002] Many refrigeration and cooling equipment with large refrigerant circuits, such as commercial air conditioners, are equipped with an oil return line to reduce the amount of oil in the refrigerant circuit. Japanese Patent Publication No. 3874980 (Patent Document 1) discloses an air conditioning system with an oil return line. One end of this oil return line is connected to an oil separator, and the other end is connected to a refrigerant pipe extending from the evaporator to the compressor.

[0003] Patent No. 3874980

[0004] In the configuration disclosed in Japanese Patent No. 3874980, when the oil level in the oil separator is low, refrigerant may flow into the oil return line. When refrigerant flows into the oil return line, refrigerant that does not contribute to the compressor's capacity circulates between the compressor and the oil return line. This increases the compressor's workload and reduces the coefficient of performance (COP) of the refrigeration cycle system.

[0005] The present disclosure has been made to explain an embodiment that solves the above-mentioned problems, and its purpose is to provide a refrigeration cycle device that can appropriately return refrigerating machine oil to the compressor while avoiding a decrease in COP.

[0006] The present disclosure relates to a refrigeration cycle device. The refrigeration cycle device includes a compressor, an oil separator, a first heat exchanger, an expansion valve, and a second heat exchanger. The compressor, the oil separator, the first heat exchanger, the expansion valve, and the second heat exchanger form a refrigerant circuit through which a refrigerant circulates. The refrigeration cycle device further includes an oil return path that returns refrigeration oil from the oil separator to a suction section of the compressor, a flow rate adjustment mechanism disposed in the oil return path, and an oil level detection device that detects the amount of refrigeration oil stored in the oil separator. The flow rate adjustment mechanism controls the flow rate of a fluid passing through the oil return path in accordance with the output of the oil level detection device.

[0007] According to the refrigeration cycle device disclosed herein, when there is a risk of refrigerant being mixed into the oil return path, the flow rate of fluid passing through the oil return path is reduced, thereby allowing refrigeration oil to be appropriately returned to the compressor while avoiding a decrease in COP.

[0008] FIG. 10 is a diagram showing the configuration of a refrigeration cycle device of embodiment 1. FIG. 11 is a flowchart for explaining control of a flow rate adjustment mechanism in embodiment 1. FIG. 12 is a diagram showing the configuration of a refrigeration cycle device of embodiment 2. FIG. 13 is a diagram showing the configuration of a refrigeration cycle device of embodiment 3. FIG. 14 is a diagram showing temperature changes when refrigerant oil flows through oil detection path 17B. FIG. 15 is a diagram showing temperature changes when refrigerant flows through oil detection path 17B. FIG. 16 is a diagram showing the configuration of a refrigeration cycle device of embodiment 4. FIG. 17 is a diagram showing the configuration of a refrigeration cycle device of embodiment 5. FIG. 18 is a diagram showing the configuration of a refrigeration cycle device of embodiment 6. FIG. 19 is a diagram showing the configuration of a refrigeration cycle device of embodiment 7. FIG. 19 is a flowchart for explaining control of a flow rate adjustment mechanism in embodiment 8.

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. While several embodiments will be described below, it was originally intended that the configurations described in each embodiment be combined as appropriate. Note that identical or corresponding parts in the drawings will be designated by the same reference numerals, and their description will not be repeated.

[0010] Embodiment 1. Figure 1 is a diagram showing the configuration of a refrigeration cycle apparatus according to Embodiment 1. The refrigeration cycle apparatus 1001 includes a compressor 10, an oil separator 11, a heat exchanger 13, an expansion valve 14, a heat exchanger 15, and a control device 600. The compressor 10, the oil separator 11, the heat exchanger 13, the expansion valve 14, and the heat exchanger 15 form a refrigerant circuit C1 through which a refrigerant circulates. During cooling operation, the heat exchanger 13 functions as a condenser, and the heat exchanger 15 functions as an evaporator.

[0011] The refrigeration cycle apparatus 1001 further includes an oil return path RP that returns refrigerating machine oil from the oil discharge portion of the oil separator 11 to the suction portion of the compressor 10, a flow rate adjustment mechanism 16 arranged in the oil return path RP, an oil level detection device 17 that detects the amount of oil stored in the oil separator 11, and a control device 600 that controls the flow rate adjustment mechanism 16 in accordance with the output of the oil level detection device 17. The refrigerating machine oil passes through the oil return path RP and is returned to the suction portion of the compressor 10. The flow rate adjustment mechanism 16 controls the flow rate of the fluid (refrigerating machine oil and refrigerant) passing through the oil return path RP in accordance with a command from the control device 600.

[0012] Although not shown, a receiver may be provided between the heat exchanger 13 and the expansion valve 14. Furthermore, although not shown, the heat exchanger 13 and the heat exchanger 15 are each provided with a fan.

[0013] The control device 600 is configured to include a CPU (Central Processing Unit) 601, memory 602 (ROM (Read Only Memory) and RAM (Random Access Memory)), an input / output buffer (not shown), etc. The CPU 601 deploys a program stored in the ROM into the RAM, etc., and executes it. The program stored in the ROM is a program in which the processing procedures of the control device 600 are written. The control device 600 controls each device in the refrigeration cycle device in accordance with these programs. This control is not limited to processing by software, but can also be processed by dedicated hardware (electronic circuitry).

[0014] The control device 600 may be distributed between the indoor unit and the outdoor unit and connected by communication.

[0015] 2 is a flowchart illustrating the control of the flow rate adjustment mechanism in the first embodiment. In step S1, the control device 600 determines whether the amount of refrigeration oil in the oil separator 11 has decreased based on the output of the oil level detection device 17. If there is not a sufficient amount of refrigeration oil in the oil separator 11, refrigerant may flow into the oil return path RP. The refrigerant that flows through the oil return path RP, bypasses the heat exchanger 13, the expansion valve 14, and the heat exchanger 15 of the refrigerant circuit C1, and returns to the compressor 10 is hereinafter referred to as the bypassed refrigerant.

[0016] If the oil amount has decreased (YES in S1), the control device 600 controls the flow rate adjustment mechanism 16 to reduce the flow rate of the fluid flowing through the oil return route RP in step S2.

[0017] On the other hand, if the oil amount has not decreased (NO in S1), the control device 600 controls the flow rate adjustment mechanism 16 to increase the flow rate of the fluid flowing through the oil return route RP in step S3.

[0018] In this way, by controlling the flow rate adjustment mechanism 16 to retain a certain amount of refrigeration oil in the oil separator 11, it is possible to reduce the amount of bypass refrigerant flowing through the oil return route RP when the oil level is low. This prevents refrigerant that does not contribute to the cooling capacity from circulating through the compressor 10 and the oil return route RP, prevents an increase in the workload of the compressor 10, and prevents a decrease in COP.

[0019] Embodiment 2 In embodiment 2, a first specific example of the oil level detection device 17 described in embodiment 1 will be described. FIG. 3 is a diagram showing the configuration of a refrigeration cycle device of embodiment 2. In a refrigeration cycle device 1002 shown in FIG. 3, the oil level detection device 17 includes an oil level sensor 17A that detects the height of the oil level in the oil separator 11. The configuration of other parts of the refrigeration cycle device 1002 is similar to that of the refrigeration cycle device 1001 shown in FIG. 1, so the description will not be repeated. Note that the control device 600 is omitted from the subsequent figures.

[0020] The oil level sensor 17A may be, for example, a float type sensor, a capacitance sensor, or a self-heating sensor.

[0021] The float sensor has a mechanism in which a float floating on the oil surface inside the oil separator 11 moves up and down, and detects the oil level based on the position of the float.

[0022] The capacitance sensor has a flat capacitor. The dielectric constant between the electrodes changes when the sensor is immersed in oil, and the capacitance of the capacitor also changes. By detecting this change in capacitance, it is possible to determine whether the amount of refrigeration oil is greater than a threshold value.

[0023] The self-heating sensor has a resistive element that generates heat when energized. When the resistive element is immersed in oil, the temperature changes and the resistance value also changes. By detecting the change in resistance value, it is possible to determine whether the amount of refrigeration oil is greater than the threshold value.

[0024] As described above, by using an oil level sensor as an oil level detection device and controlling the flow rate adjustment mechanism, the amount of bypass refrigerant flowing through the oil return route RP when the oil level is low can be reduced. This prevents refrigerant that does not contribute to the cooling capacity from circulating between the compressor 10 and the oil return route RP, prevents an increase in the workload of the compressor 10, and prevents a decrease in COP.

[0025] Embodiment 3 In embodiment 3, a second specific example of the oil level detection device 17 described in embodiment 1 will be described. Fig. 4 is a diagram showing the configuration of a refrigeration cycle device of embodiment 3. In a refrigeration cycle device 1003 shown in Fig. 4, the oil level detection device 17 includes an oil detection path 17B, a solenoid valve 17C, a cooling device 17D, and a temperature sensor 17E. The configuration of other parts of the refrigeration cycle device 1003 is similar to that of the refrigeration cycle device 1001 shown in Fig. 1, and therefore description thereof will not be repeated.

[0026] The cooling device 17D includes an internal heat exchanger 171. The internal heat exchanger 171 is configured to exchange heat between the low-temperature, low-pressure gas refrigerant after passing through the heat exchanger 15 and the fluid (refrigerating machine oil and / or gas refrigerant) passing through the oil detection path 17B.

[0027] The intake port P3 of the oil detection path 17B is installed at a predetermined height of the oil separator 11. The position of the intake port P3 is higher than the position of the oil discharge port P4 of the oil separator 11 and lower than the positions of the gas inlet P1 and the gas discharge port P2.

[0028] The oil detection passage 17B is connected to the oil return passage at a junction P5 located upstream of the flow rate adjustment mechanism 16. ...

[0029] Fig. 5 is a diagram showing a temperature change when refrigerating machine oil flows through the oil detection passage 17B. Fig. 6 is a diagram showing a temperature change when refrigerant flows through the oil detection passage 17B.

[0030] As shown in Figure 5, when the oil level is higher than the height of the suction port P3, refrigeration oil flows through the oil detection path 17B. When this oil is cooled by the internal heat exchanger 171, the temperature drops from temperature T1 to temperature T2, which is below the saturated gas temperature. On the other hand, as shown in Figure 6, when the oil level is lower than the height of the suction port P3, refrigerant flows through the oil detection path 17B. Even when this oil is cooled by the internal heat exchanger 171, the temperature drops only to the saturated gas temperature T3. If the internal heat exchanger 171 is designed appropriately, the temperature difference shown in Figures 5 and 6 can be generated.

[0031] Therefore, when detecting the oil level, solenoid valve 17C is opened and the temperature is measured by temperature sensor 17E. When the temperature measured by temperature sensor 17E is lower than the saturated gas temperature converted from the pressure detected by a high-pressure sensor (not shown), it can be detected that the oil level is lower than the height of intake port P3.

[0032] As described above, if the oil level detection device detects the oil level based on the temperature change when the fluid flowing through the oil detection path 17B is cooled and controls the flow rate adjustment mechanism, the amount of bypass refrigerant flowing through the oil return path RP when the oil level drops can be reduced. This prevents refrigerant that does not contribute to the cooling capacity from circulating between the compressor 10 and the oil return path RP, prevents an increase in the workload of the compressor 10, and prevents a decrease in the COP.

[0033] Embodiment 4 In embodiment 4, a third specific example of the oil level detection device 17 described in embodiment 1 will be described. Fig. 7 is a diagram showing the configuration of a refrigeration cycle apparatus according to embodiment 4. The refrigeration cycle apparatus 1004 shown in Fig. 7 further includes a bypass flow path BP, a heat exchanger 19, and an expansion valve 20 in addition to the configuration of the refrigeration cycle apparatus 1001 shown in Fig. 1.

[0034] The heat exchanger 19 has a first flow path and a second flow path, and is configured to exchange heat between the refrigerant flowing through these paths. The refrigerant that has passed through the heat exchanger 13 flows through the first flow path of the heat exchanger 19. The bypass flow path BP branches off from a branch point between the outlet of the first flow path of the heat exchanger 19 and the expansion valve 14, and merges with the refrigerant circuit C1 near the suction port of the compressor 10.

[0035] The oil level detection device 17 includes an oil detection passage 17B, a solenoid valve 17C, a cooling device 17D, and a temperature sensor 17E. The other parts of the configuration of the refrigeration cycle device 1004 are similar to those of the refrigeration cycle device 1001 shown in FIG. 1, and therefore description thereof will not be repeated.

[0036] In the fourth embodiment, the cooling device 17D includes an internal heat exchanger 172. The internal heat exchanger 172 is configured to exchange heat between the refrigerant in the bypass flow path BP after passing through the heat exchanger 19 and the fluid (refrigerating machine oil and / or gas refrigerant) passing through the oil detection path 17B.

[0037] The intake port P3 of the oil detection path 17B is installed at a predetermined height of the oil separator 11. The position of the intake port P3 is higher than the position of the oil discharge port P4 of the oil separator 11 and lower than the positions of the gas inlet P1 and the gas discharge port P2.

[0038] The oil detection path 17B is connected to the oil return path at a junction P5 located upstream of the flow rate adjustment mechanism 16. ...

[0039] In the fourth embodiment as well, if the internal heat exchanger 172 is designed to generate the temperature difference shown in FIGS. 5 and 6, the oil level position can be detected.

[0040] In the fourth embodiment, as in the third embodiment, an increase in the workload of the compressor 10 can be prevented, and a decrease in the COP can be prevented. Furthermore, since the expansion valve 20 can control the flow rate of the refrigerant flowing through the bypass flow path BP, the heat exchange amount of the heat exchanger 172 can be adjusted to any value, and the heat exchanger 172 can be easily designed because it can respond to a wide range of changes in the state of the refrigeration cycle.

[0041] Embodiment 5 In embodiment 5, a first specific example of the flow rate adjustment mechanism described in embodiment 1 will be described. Fig. 8 is a diagram showing the configuration of a refrigeration cycle apparatus of embodiment 5. A refrigeration cycle apparatus 1005 shown in Fig. 8 includes an electronic expansion valve (Linear Expansion Valve: LEV) 16A as the flow rate adjustment mechanism 16. The configuration of other parts of the refrigeration cycle apparatus 1005 is similar to that of the refrigeration cycle apparatus 1001 of Fig. 1, and description thereof will not be repeated.

[0042] By using the electronic expansion valve 16A, the control device 600 can increase or decrease the flow rate of the fluid (refrigerant and refrigerating machine oil) passing through the oil return route RP based on the output of the oil level detection device 17.

[0043] In the fifth embodiment, any of the configurations shown in the second to fourth embodiments can be used as the oil level detection device 17. Furthermore, the control device 600 can control the flow rate using the control shown in the first embodiment.

[0044] Sixth Embodiment In the sixth embodiment, a second specific example of the flow rate adjustment mechanism described in the first embodiment will be described. FIG. 9 is a diagram showing the configuration of a refrigeration cycle apparatus according to the sixth embodiment. In the refrigeration cycle apparatus 1006 shown in FIG. 9, the flow rate adjustment mechanism 16 includes a solenoid valve 16B and a capillary tube 16C arranged in series in the oil return path RP. The configuration of the other parts of the refrigeration cycle apparatus 1006 is similar to that of the refrigeration cycle apparatus 1001 shown in FIG. 1, and therefore description thereof will not be repeated.

[0045] As described above, the capillary tube 16C and the solenoid valve 16B are installed in the oil return route RP, and the solenoid valve 16B is controlled to open when the flow rate is increased and closed when the flow rate is decreased. This allows the control device 600 to adjust the flow rates of the refrigerant and refrigerating machine oil passing through the oil return route RP.

[0046] In the sixth embodiment, any of the configurations shown in the second to fourth embodiments can be used as the oil level detection device 17. Furthermore, the control device 600 can control the flow rate using the control shown in the first embodiment.

[0047] When an LEV is disposed in the oil return line RP as in the fifth embodiment, it is preferable to use a component other than the expansion valve 14. Because the oil return line RP carries high-temperature refrigeration oil and refrigerant discharged from the compressor 10, the LEV must have high heat resistance. Therefore, an LEV disposed in the oil return line RP as shown in FIG. 8 may require special specifications and be an expensive component. On the other hand, because capillary tubes and solenoid valves have a simple structure and high heat resistance, common components can be used in the oil return line, making it possible to construct a flow rate adjustment mechanism at low cost.

[0048] Seventh Embodiment In the seventh embodiment, a third specific example of the flow rate adjustment mechanism described in the first embodiment will be described. Fig. 10 is a diagram showing the configuration of a refrigeration cycle apparatus according to the seventh embodiment. In the refrigeration cycle apparatus 1007 shown in Fig. 10, an oil return path RP branches into flow paths RP1 and RP2 at a branch point BP1 and then merges at a junction MP1. The flow rate adjustment mechanism 16 includes a solenoid valve 16B and a capillary tube 16C arranged in series in flow path RP1, and a capillary tube 16D arranged in flow path RP2.

[0049] In the seventh embodiment, any of the configurations shown in the second to fourth embodiments can be used as the oil level detection device 17. Furthermore, the control device 600 can control the flow rate using the control shown in the first embodiment.

[0050] 10, the oil return path RP is branched into RP1 and RP2 in parallel, with capillary tubes 16C and 16D installed in each path, and a solenoid valve 16B installed in one path, RP1. The control device 600 can adjust the flow rate by opening the solenoid valve 16B when increasing the flow rate and closing the solenoid valve 16B when decreasing the flow rate.

[0051] In the configuration shown in FIG. 9, when the flow rate is reduced, the flow rate becomes zero. However, in the configuration shown in FIG. 10, even when the flow rate is reduced, a certain amount of refrigeration oil can be returned to the compressor 10.

[0052] Embodiment 8 In Embodiment 1, during operation of the refrigeration cycle device, the amount of refrigerant flowing through the oil return path RP is constantly monitored, and the flow rate is controlled by the flow rate adjustment mechanism 16. However, the flow rate adjustment mechanism 16 also has moving parts, and it is advantageous in terms of the lifespan of the device to move the moving parts as few times as possible.

[0053] Therefore, in the eighth embodiment, the control shown in FIG. 2 is executed only in a situation where the refrigerant is likely to flow into the oil return route RP.

[0054] 11 is a flowchart for explaining the control of the flow rate adjustment mechanism in embodiment 8. In step S11, the control device 600 determines whether an execution condition for determining whether or not to execute flow rate adjustment control is met.

[0055] For example, the control device 600 determines that the execution condition of step S11 is met when the operating frequency of the compressor 10 is lower than the judgment frequency. The judgment frequency can be set to, for example, half the upper limit of the operating frequency of the compressor.

[0056] When the operating frequency of the compressor 10 is low, the amount of refrigeration oil discharged from the compressor 10 decreases. As the amount of refrigeration oil in the oil separator 11 decreases, the refrigerant is more likely to return to the oil return path RP. On the other hand, when there is a lot of refrigeration oil in the oil separator 11, the refrigeration oil mainly flows through the oil return path RP, so a decrease in COP due to the presence of the oil return path is unlikely to occur. Therefore, as described above, the operating frequency of the compressor is used to determine whether or not to perform flow rate adjustment control.

[0057] However, the execution condition is not limited to this. For example, the control device 600 may determine that the execution condition of step S11 is met when the pressure difference between the suction port and the discharge port of the compressor 10 is smaller than a determination threshold value. In this case, the determination threshold value may be set to half the maximum value of the pressure difference.

[0058] When the diameter of the fluid passage restriction portion of the flow rate adjustment mechanism is the same, the larger the differential pressure, the greater the amount of fluid passing through the oil return path RP, making it easier for the refrigerant to return. Therefore, as described above, it may be possible to determine whether to perform flow rate adjustment control based on the magnitude of the differential pressure.

[0059] If the execution condition is not met (NO in S11), the control device 600 fixes the flow rate of the flow rate adjustment mechanism 16 to a standard value in step S15. This reduces the number of times the movable part of the flow rate adjustment mechanism 16 moves, which is advantageous in terms of product life.

[0060] If the execution condition is met (YES in S11), in step S12, the control device 600 determines whether the amount of refrigerating machine oil in the oil separator 11 has decreased based on the output of the oil amount detection device 17. If there is not a sufficient amount of refrigerating machine oil in the oil separator 11, there is a possibility that refrigerant will flow into the oil return path RP.

[0061] If the oil amount has decreased (YES in S12), the control device 600 controls the flow rate adjustment mechanism 16 to reduce the flow rate of the fluid flowing through the oil return route RP in step S13.

[0062] On the other hand, if the oil amount has not decreased (NO in S12), the control device 600 controls the flow rate adjustment mechanism 16 to increase the flow rate of the fluid flowing through the oil return route RP in step S14.

[0063] In this way, by controlling the flow rate adjustment mechanism 16 to retain a certain amount of refrigeration oil in the oil separator 11, it is possible to reduce the amount of bypass refrigerant flowing through the oil return route RP when the oil level is low. This prevents refrigerant that does not contribute to the cooling capacity from circulating through the compressor 10 and the oil return route RP, prevents an increase in the workload of the compressor 10, and prevents a decrease in COP.

[0064] In the eighth embodiment, any of the configurations shown in the second to fourth embodiments can be used as the oil level detection device 17. Furthermore, any of the configurations shown in the fifth to seventh embodiments can be used as the flow rate adjustment mechanism 16.

[0065] In the eighth embodiment, the same effects as those of the first to seventh embodiments can be obtained, and the life of the flow rate adjusting mechanism 16 can be extended more than that of the first to seventh embodiments.

[0066] (Summary) Hereinafter, the embodiment will be summarized with reference to the drawings again.

[0067] (1) The refrigeration cycle apparatus 1001 shown in FIG. 1 of the present disclosure includes a compressor 10, an oil separator 11, a heat exchanger 13, an expansion valve 14, and a heat exchanger 15. The compressor 10, the oil separator 11, the heat exchanger 13, the expansion valve 14, and the heat exchanger 15 configure a refrigerant circuit C1 through which a refrigerant circulates. The refrigeration cycle apparatus 1001 further includes an oil return path RP that returns refrigeration oil from the oil separator 11 to the suction section of the compressor 10, a flow rate adjustment mechanism 16 disposed in the oil return path RP, and an oil level detection device 17 that detects the amount of refrigeration oil stored in the oil separator 11. The flow rate adjustment mechanism 16 controls the flow rate of a fluid passing through the oil return path RP in accordance with the output of the oil level detection device 17.

[0068] (2) In paragraph 1, as shown in FIG. 3, the oil level detection device 17 includes an oil level sensor 17A that detects the position of the oil level in the oil separator.

[0069] (3) In paragraph 1, as shown in FIG. 4, the oil amount detection device 17 includes an oil detection path 17B that is connected to the oil separator 11 at an intake port P3 that is higher than the position of the oil discharge port P4 at which one end of the oil return path RP is connected to the oil separator 11, and that is connected to the oil return path RP at a junction P5 provided in the oil return path RP, a cooling device 17D that cools the fluid passing through the oil detection path 17B, and a temperature sensor 17E that detects the temperature of the part of the oil detection path 17B that has passed through the cooling device 17D.

[0070] (4) In paragraph 3, as shown in FIG. 4, the cooling device 17D includes a heat exchanger 171 configured to exchange heat between the refrigerant flowing from the heat exchanger 15 to the compressor 10 in the refrigerant circuit C1 and the fluid passing through the oil detection path 17B.

[0071] (5) In the third paragraph, as shown in Fig. 7, the refrigeration cycle apparatus 1004 further includes a bypass flow path BP that branches off a portion of the refrigerant flowing from the heat exchanger 13 in the refrigerant circuit C1 toward the expansion valve 14 and returns the refrigerant to the compressor 10. The cooling device 17D includes a heat exchanger 172 configured to exchange heat between the refrigerant passing through the bypass flow path BP and a fluid passing through the oil detection path 17B.

[0072] (6) In any one of paragraphs 1 to 5, as shown in FIG. 8, the flow rate adjusting mechanism 16 includes an electronic expansion valve 16A.

[0073] (7) In any one of paragraphs 1 to 5, as shown in FIG. 9, the flow rate adjustment mechanism 16 includes a solenoid valve 16B and a capillary tube 16C arranged in series in the oil return path RP.

[0074] (8) In any one of paragraphs 1 to 5, as shown in Fig. 10, the oil return route RP branches into a flow path RP1 and a flow path RP2 at a branch point BP1 and then merges at a junction MP. The flow rate adjustment mechanism 16 includes a solenoid valve 16B and a capillary tube 16C arranged in series in the flow path RP1, and a capillary tube 16D arranged in the flow path RP2.

[0075] (9) In any one of paragraphs 1 to 8, the refrigeration cycle apparatus 1001 further includes a control device 600 that controls the compressor 10 and the flow rate adjustment mechanism 16. As shown in Fig. 11 , the control device 600 is configured to execute a first control (S15) that keeps the flow rate of the flow rate adjustment mechanism 16 fixed while the compressor 10 is operating, and a second control (S12 to S14) that controls the flow rate of the flow rate adjustment mechanism 16 in accordance with the output of the oil level detection device 17 while the compressor 10 is operating.

[0076] (10) In paragraph 9, as shown in FIG. 11, the control device 600 is configured to execute the first control (S15) when the operating frequency of the compressor 10 is higher than a threshold value, and to execute the second control (S12 to S14) when the operating frequency is lower than the threshold value.

[0077] (11) In paragraph 9, as shown in FIG. 11, the control device 600 is configured to execute the first control (S15) when the pressure difference between the suction section and the discharge section of the compressor 10 is smaller than a threshold value, and to execute the second control (S12 to S14) when the pressure difference is larger than the threshold value.

[0078] 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 by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0079] 10 Compressor, 11 Oil separator, 13, 15, 19, 171, 172 Heat exchanger, 14, 20 Expansion valve, 16 Flow rate adjustment mechanism, 16A Electronic expansion valve, 16B, 17C Solenoid valve, 16C, 16D Capillary tube, 17 Oil level detection device, 17A Oil level sensor, 17B Oil detection path, 17D Cooling device, 17E Temperature sensor, 600 Control device, 601 CPU, 602 Memory, 1001 to 1007 Refrigeration cycle device, BP Bypass flow path, BP1 Branch point, C1 Refrigerant circuit, MP, MP1, P5 Junction point, P1 Gas inlet, P2 Gas outlet, P3 Intake port, P4 Oil outlet, RP Return oil path, RP1, RP2 Flow path.

Claims

1. A refrigeration cycle device comprising a compressor, an oil separator, a first heat exchanger, an expansion valve, and a second heat exchanger, wherein the compressor, the oil separator, the first heat exchanger, the expansion valve, and the second heat exchanger constitute a refrigerant circuit through which a refrigerant circulates, a return oil path for returning refrigeration machine oil from the oil separator to the suction part of the compressor, a flow rate adjustment mechanism disposed in the return oil path, and an oil quantity detection device for detecting the quantity of refrigeration machine oil stored in the oil separator, wherein the flow rate adjustment mechanism controls the flow rate of the fluid passing through the return oil path according to the output of the oil quantity detection device, the oil quantity detection device comprises an oil detection path connected to the return oil path at a connection point connected to the oil separator at a position higher than the position where one end of the return oil path is connected to the oil separator, a cooling device for cooling the fluid passing through the oil detection path, and a temperature sensor for detecting the temperature of a portion of the oil detection path after passing through the cooling device.

2. The refrigeration cycle device according to claim 1, wherein the oil quantity detection device comprises an oil level sensor for detecting the position of the oil level in the oil separator.

3. The cooling device comprises a third heat exchanger configured to perform heat exchange between the refrigerant flowing from the second heat exchanger to the compressor in the refrigerant circuit and the fluid passing through the oil detection path, according to claim 1.

4. The refrigeration cycle device further comprises a bypass flow path for branching a part of the refrigerant flowing from the first heat exchanger to the expansion valve in the refrigerant circuit and returning it to the compressor, The cooling device comprises a third heat exchanger configured to perform heat exchange between the refrigerant passing through the bypass flow path and the fluid passing through the oil detection path, according to claim 1.

5. The refrigeration cycle device according to any one of claims 1 to 4, wherein the flow rate adjustment mechanism comprises an electronic expansion valve.

6. The refrigeration cycle device according to any one of claims 1 to 4, wherein the flow rate adjustment mechanism comprises a solenoid valve and a capillary tube disposed in series in the return oil path.

7. The return oil path branches into a first flow path and a second flow path at a branch point and then merges at a merging point, The flow rate adjustment mechanism comprises a solenoid valve and a first capillary tube disposed in series in the first flow path, and a second capillary tube disposed in the second flow path, according to any one of claims 1 to 4.

8. The refrigeration cycle device further includes a control device that controls the compressor and the flow rate adjustment mechanism. The control device is configured to execute a first control for fixing the flow rate of the flow rate adjustment mechanism during operation of the compressor, and a second control for controlling the flow rate of the flow rate adjustment mechanism according to the output of the oil amount detection device during operation of the compressor. The refrigeration cycle device according to any one of claims 1 to 4.

9. The control device is configured to execute the first control when the operating frequency of the compressor is higher than a threshold value, and execute the second control when the operating frequency is lower than the threshold value. The refrigeration cycle device according to claim 8.

10. The control device is configured to execute the first control when the pressure difference between the suction part and the discharge part of the compressor is smaller than a threshold value, and execute the second control when the pressure difference is larger than the threshold value. The refrigeration cycle device according to claim 8.