COOLING CIRCUIT DEVICE

Abstract

Refrigeration circuit device (1001), comprising: a compressor (10), an oil separator (11), a first heat exchanger (13), an expansion valve (14) and a second heat exchanger (15), wherein the compressor (10), the oil separator (11), the first heat exchanger (13), the expansion valve (14) and the second heat exchanger (15) form a refrigerant circuit (C1) through which refrigerant circulates; an oil return path (RP) configured to return refrigeration oil from the oil separator (11) to an inlet of the compressor (10); a flow rate adjustment mechanism (16) arranged in the oil return path (RP);and an oil quantity measuring device (17) configured to measure a quantity of refrigeration oil stored in the oil separator (11), wherein the flow rate adjustment mechanism (16) is configured to operate in response to an output from the oil quantity measuring device (17) to control a flow rate of a fluid passing through the oil return path (RP), wherein the oil quantity measuring device (17) comprises: an oil measurement path (17B) connected to the oil separator (11) at a point which is level higher than a point at which an end of the oil return path (RP) is connected to the oil separator (11), and which is connected to the oil return path (RP) at a connection point provided on the oil return path (RP); a cooling device (17D) configured to cool a fluid passing through the oil measurement path (17B);and a temperature sensor (17E) configured to detect the temperature of a section of the oil measuring path (17B) after it has passed through the cooling device (17D).

Description

TECHNICAL AREA The present disclosure relates to a refrigeration circuit device. Many thermal devices, such as commercial air conditioners with a large-scale refrigerant circuit, may incorporate an oil return path to reduce the amount of oil in the refrigerant circuit. Japanese Patent No. 3874980 (PTL 1) discloses an air conditioner with an oil return path. The oil return path is connected at one end to an oil separator and at the other end to a refrigerant line leading from an evaporator to a compressor. REFERENCE LIST PATENT LITERATURE PTL 1: Japanese Patent No. 3874980 SUMMARY OF THE INVENTION TECHNICAL PROBLEM In the configuration disclosed in Japanese Patent No. 3874980, refrigerant may flow into the oil return path if the oil separator contains a small amount of oil. When refrigerant flows into the oil return path, the non-performance refrigerant circulates through the compressor and the oil return path. As a result, the workload of the compressor increases, and the refrigeration circuit has a detrimentally reduced coefficient of performance (COP). The present disclosure was made to describe an embodiment to solve such a problem as explained above, and considers a refrigeration circuit device that is able to return refrigeration oil to a compressor in an adequate manner while avoiding a reduced COP. SOLUTION TO THE PROBLEM The present disclosure relates to a refrigeration circuit device. The refrigeration circuit device comprises 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 the refrigerant circulates. The refrigeration circuit device further comprises an oil return path configured to return refrigeration oil from the oil separator to an inlet of the compressor, a flow rate adjustment mechanism arranged on the oil return path, and an oil quantity measuring device configured to detect a quantity of refrigeration oil stored in the oil separator.The flow rate adjustment mechanism is set up to operate in response to an output from the oil quantity measuring device in order to control the flow rate of a fluid passing through the oil return path. ADVANTAGEOUS EFFECTS OF THE INVENTION The refrigeration circuit device presented here can reduce the flow rate of a fluid passing through an oil return path when there is a possibility that refrigerant will be introduced into the oil return path, and the refrigeration circuit device can thus adequately return refrigeration oil to the compressor while avoiding a reduced COP. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing a configuration of a refrigeration circuit device according to a first embodiment. Fig. 2 is a flow diagram illustrating how a flow rate adjustment mechanism is controlled according to the first embodiment. Fig. 3 is a diagram showing a configuration of a refrigeration circuit device according to a second embodiment. Fig. 4 is a diagram showing a configuration of a refrigeration circuit device according to a third embodiment. Fig. 5 is a diagram showing how the temperature of the refrigeration oil changes when the refrigeration oil flows through an oil measuring path 17B. Fig. 6 is a diagram showing how the temperature of the refrigeration oil changes when the refrigerant flows through the oil measuring path 17B. Fig. 7 is a diagram showing a configuration of a refrigeration circuit device according to a fourth embodiment.Figure 8 is a diagram showing a configuration of a refrigeration circuit device according to a fifth embodiment. Figure 9 is a diagram showing a configuration of a refrigeration circuit device according to a sixth embodiment. Figure 10 is a diagram showing a configuration of a refrigeration circuit device according to a seventh embodiment. Figure 11 is a flowchart illustrating how a flow rate adjustment mechanism is controlled according to an eighth embodiment. DESCRIPTION OF THE EXECUTION FORMS Embodiments of the present invention are described in detail below with reference to the accompanying drawings. Although a multitude of embodiments are described below, at the time of filing the present application it was originally intended to combine the configurations described in the embodiments in an appropriate manner. In the drawings, identical or equivalent components are designated identically and are not described repeatedly. First embodiment. Fig. 1 is a representation showing a configuration of a refrigeration circuit device according to a first embodiment. A refrigeration circuit device 1001 comprises a compressor 10, an oil separator 11, a heat exchanger 13, an expansion valve 14, a heat exchanger 15, and a control unit 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 refrigerant circulates. In cooling operation, the heat exchanger 13 acts as a condenser, and the heat exchanger 15 acts as an evaporator. The refrigeration circuit device 1001 further comprises an oil return path RP, which is configured to return refrigeration oil from an oil discharge outlet of the oil separator 11 to an inlet of the compressor 10; a flow rate adjustment mechanism 16, which is arranged on the oil return path RP; an oil quantity measuring device 17, which is configured to detect a quantity of oil stored in the oil separator 11; and a control unit 600, which is configured to control the flow rate adjustment mechanism 16 in response to an output from the oil quantity measuring device 17. The refrigeration oil is returned to the inlet of the compressor 10 via the oil return path RP. The flow rate adjustment mechanism 16 operates in response to a command received from the control unit 600 to control the flow rate of a fluid (refrigeration oil and refrigerant) passing through the oil return path RP. Although not shown, a liquid collector may be provided between the heat exchanger 13 and the expansion valve 14. Furthermore, although not shown, the heat exchangers 13 and 15 are each equipped with a fan. The control unit 600 comprises a CPU (central processing unit) 601, a memory 602 (ROM (read-only memory) and RAM (random access memory)), an input / output buffer (not shown), and the like. The CPU 601 loads a program stored in ROM into RAM or the like and executes the program. The program stored in ROM describes a processing sequence for the control unit 600. The control unit 600 controls each component in the refrigeration circuit device according to these programs. This control is not limited to software processing but can also be performed by dedicated hardware (or electronic circuitry). It should be noted that the control unit 600 can be distributed between an indoor unit and an outdoor unit and connected via communication. Fig. 2 is a flowchart illustrating how the flow rate adjustment mechanism is controlled according to the first embodiment. In step S1, the control unit 600 determines, based on an output from the oil quantity measuring device 17, whether the oil separator 11 contains a reduced amount of refrigeration oil. If there is an insufficient amount of refrigeration oil in the oil separator 11, refrigerant may flow through the oil return path RP. Refrigerant flowing through the oil return path RP, bypassing the heat exchanger 13, the expansion valve 14, and the heat exchanger 15 of the refrigerant circuit C1, and returning to the compressor 10, is hereinafter referred to as bypass refrigerant. If the oil separator has a reduced amount of oil (JA in S1), the control unit 600 regulates the flow rate adjustment mechanism 16 to reduce the flow rate of a fluid flowing through the oil return path RP in step S2. If, on the other hand, the oil separator does not show a reduced oil quantity (NO in S1), the control unit 600 regulates the flow rate adjustment mechanism 16 to increase the flow rate of the fluid flowing through the oil return path RP in step S3. In this way, the flow rate adjustment mechanism 16 can be controlled to retain a certain amount of refrigeration oil in the oil separator 11, thereby reducing the amount of bypass refrigerant flowing through the oil return path RP when the oil separator contains a reduced amount of oil. This prevents refrigerant that does not contribute to cooling capacity from circulating through the compressor 10 and the oil return path RP, thus preventing increased workload on the compressor 10 and consequently a reduced COP. Second embodiment. In a second embodiment, a first concrete example of the oil quantity measuring device 17, which is described in the first embodiment, is explained. Fig. 3 is a representation showing a configuration of a refrigeration circuit device according to the second embodiment. In a refrigeration circuit device 1002 shown in Fig. 3, the oil quantity measuring device 17 comprises an oil level sensor 17A, which is configured to measure the level of oil on the surface of the oil in the oil separator 11. The remainder of the refrigeration circuit device 1002 is constructed similarly to the refrigeration circuit device 1001 shown in Fig. 1 and is therefore not described again. It should be noted that the control unit 600 is not shown in the following figures. The oil level sensor 17A can be, for example, a float-type sensor, a capacity sensor, a self-heating sensor, or the like. The float-type sensor has a mechanism in which a float, which floats on the surface of the oil in the oil separator 11, moves up and down, and the float-type sensor measures an oil level depending on the position of the float. The capacitance sensor includes a parallel-plate capacitor. Since the dielectric constant between the electrodes changes in response to immersion in oil, the capacitor's capacitance also changes. By detecting this change in capacitance, it's possible to determine whether the refrigeration oil level exceeds a reference value. The self-heating sensor has a resistive element that conducts electricity and generates heat. When the resistive element is immersed in oil, its temperature changes, and consequently, so does its resistance value. By detecting this change in resistance, it's possible to determine whether the refrigeration oil level exceeds the reference value. By using an oil level sensor as the oil quantity measuring device to control the flow rate adjustment mechanism, the amount of bypass refrigerant flowing through the oil return path RP can be reduced when the oil separator has a reduced oil quantity. This prevents refrigerant that does not contribute to cooling capacity from circulating through the compressor 10 and the oil return path RP, thus preventing increased workload on the compressor 10 and a reduced COP. Third embodiment In a third embodiment, a second concrete example of the oil quantity measuring device 17, which is described in the first embodiment, is explained. Fig. 4 is a representation showing a configuration of a refrigeration circuit device according to the third embodiment. In a refrigeration circuit device 1003 shown in Fig. 4, the oil quantity measuring device 17 comprises an oil measuring path 17B, a solenoid valve 17C, a cooling device 17D, and a temperature sensor 17E. The remainder of the refrigeration circuit device 1003 is constructed similarly to the refrigeration circuit device 1001 shown in Fig. 1 and is therefore not described again. The cooling device 17D includes an internal heat exchanger 171. The internal heat exchanger 171 is configured so that a low-temperature, low-pressure gaseous refrigerant that has passed through the heat exchanger 15 and a fluid (refrigeration oil and / or gaseous refrigerant) that passes through the oil measuring path 17B exchange heat. The oil measuring path 17B has an intake inlet P3, which is set to a predetermined level at the oil separator 11. The intake inlet P3 is at a higher level than an oil discharge outlet P4 of the oil separator 11 and at a lower level than a gas flow inlet P1 and a gas discharge outlet P2. Along the oil sensing path 17B, the solenoid valve 17C, the internal heat exchanger 171, and the temperature sensor 17E are arranged in this order. The oil sensing path 17B connects to the oil return path at a junction point P5 upstream of the flow rate adjustment mechanism 16. Fig. 5 is a diagram showing how the temperature of the refrigeration oil changes as the refrigeration oil flows through oil measuring path 17B. Fig. 6 is a diagram showing how the temperature of the refrigeration oil changes as the refrigerant flows through oil measuring path 17B. As shown in Fig. 5, refrigeration oil flows through the oil measuring path 17B when the oil level is higher than the level of the intake inlet P3. When the refrigeration oil is cooled by the internal heat exchanger 171, its temperature drops from a temperature T1 to a temperature T2 that is equal to or lower than the temperature of the saturated gas. Conversely, as shown in Fig. 6, refrigerant flows through the oil measuring path 17B when the oil level is lower than the level of the intake inlet P3. When the refrigerant is cooled by the internal heat exchanger 171, its temperature drops only to the temperature T3 of the saturated gas. If the internal heat exchanger 171 is adequately designed, the temperature difference shown in Figs. 5 and 6 can be achieved. Accordingly, when the oil level is detected, the solenoid valve 17C opens and the temperature sensor 17E measures the temperature. If the temperature measured by temperature sensor 17E is lower than the temperature of the saturated gas, which is converted from the pressure measured by a high-pressure sensor (not shown), it can be determined that the oil level is lower than the level of the intake inlet P3. As described above, if the oil quantity measuring device detects an oil level based on the temperature change of a fluid flowing through oil measurement path 17B as the fluid cools, and the flow rate adjustment mechanism is controlled, the amount of bypass refrigerant flowing through oil return path RP can be reduced when the oil separator has a reduced oil quantity. This prevents refrigerant that does not contribute to cooling capacity from circulating through compressor 10 and oil return path RP, thus preventing increased workload on compressor 10 and consequently a reduced COP. Fourth embodiment. In a fourth embodiment, a third concrete example of the oil quantity measuring device 17, which is explained in the first embodiment, is described. Fig. 7 is a representation showing a configuration of a refrigeration circuit device according to the fourth embodiment. A refrigeration circuit device 1004 shown in Fig. 7 comprises, in addition to the configuration of the refrigeration circuit device 1001 shown in Fig. 1, a bypass flow path BP, a heat exchanger 19, and an expansion valve 20. The heat exchanger 19 has a first and a second flow path and is designed for heat exchange between the refrigerant flowing through the flow paths. The first flow path of the heat exchanger 19 carries refrigerant that has passed through the heat exchanger 13. The bypass flow path BP branches off from a junction point between an outlet of the first flow path of the heat exchanger 19 and the expansion valve 14 and opens into the refrigerant circuit C1 near the inlet of the compressor 10. The oil quantity measuring device 17 further comprises an oil measuring path 17B, a solenoid valve 17C, a cooling device 17D and a temperature sensor 17E. The remainder of the refrigeration circuit device 1004 is similar in design to the refrigeration circuit device 1001 shown in Fig. 1 and is therefore not described again. The cooling device 17D in the fourth embodiment comprises an internal heat exchanger 172. The internal heat exchanger 172 is arranged such that the refrigerant in the bypass flow path BP, after passing through the heat exchanger 19, and a fluid (refrigeration oil and / or gaseous refrigerant) passing through the oil measuring path 17B exchange heat. The oil measuring path 17B has an intake inlet P3, which is set to a predetermined level at the oil separator 11. The intake inlet P3 is at a higher level than an oil discharge outlet P4 of the oil separator 11 and at a lower level than a gas flow inlet P1 and a gas discharge outlet P2. Along the oil measuring path 17B, the solenoid valve 17C, the internal heat exchanger 172, and the temperature sensor 17E are arranged in this order. The oil measuring path 17B connects to the oil return path at a junction point P5 upstream of the flow rate adjustment mechanism 16. In the fourth embodiment, the design of the internal heat exchanger 172, which causes the temperature difference shown in Fig. 5 and Fig. 6, also enables the detection of an oil level. Like the third embodiment, the fourth embodiment can also prevent increased work of the compressor 10 and thus a reduced COP. Furthermore, the expansion valve 20 can be used to control the flow rate of the refrigerant flowing through the bypass flow path BP, so that the amount of heat exchanged in the heat exchanger 172 can be adjusted to any desired value, and even during a change of state in the refrigeration cycle, this can be managed over a wide range, which simplifies the design of the heat exchanger 172. Fifth embodiment. In a fifth embodiment, a first concrete example of the flow rate adjustment mechanism described in the first embodiment is explained. Fig. 8 is a representation showing a configuration of a refrigeration circuit device according to the fifth embodiment. A refrigeration circuit device 1005 shown in Fig. 8 comprises a linear expansion valve (LEV) 16A as a flow rate adjustment mechanism 16. The remainder of the refrigeration circuit device 1005 is similar in design to the refrigeration circuit device 1001 shown in Fig. 1 and is therefore not described again. The use of the linear expansion valve 16A enables the control unit 600 to increase / decrease the flow rate of a fluid (refrigerant and refrigeration oil) flowing through the oil return path RP in response to an output from the oil quantity measuring device 17. In the fifth embodiment, the oil quantity measuring device 17 can have one of the configurations described in the second to fourth embodiments. Furthermore, the control unit 600 can apply the control described in the first embodiment to regulate a flow rate. Sixth embodiment. In a sixth embodiment, a second concrete example of the flow rate adjustment mechanism described in the first embodiment is explained. Fig. 9 is a representation showing a configuration of a refrigeration circuit device according to the sixth embodiment. In a refrigeration circuit device 1006 shown in Fig. 9, the flow rate adjustment mechanism 16 comprises a solenoid valve 16B and a capillary line 16C, which are arranged in series on the oil return path RP. The remainder of the refrigeration circuit device 1006 is similar in design to the refrigeration circuit device 1001 shown in Fig. 1 and is therefore not described again. As described above, the oil return path RP is equipped with a capillary line 16C and a solenoid valve 16B. The solenoid valve 16B is controlled to open when the flow rate increases and to close when the flow rate decreases. Thus, the control unit 600 can adjust the flow rate of the refrigerant and refrigeration oil passing through the oil return path RP. In the sixth embodiment, the oil quantity measuring device 17 can have one of the configurations described in the second to fourth embodiments. Furthermore, the control unit 600 can apply the control described in the first embodiment to regulate a flow rate. If the oil return path RP, as explained in the fifth embodiment, is equipped with a LEV, a component other than the expansion valve 14 is preferably used. The oil return path RP carries the refrigeration oil and refrigerant discharged from the compressor 10 at high temperature, which is why the LEV must be particularly heat-resistant. The LEV in the oil return path RP, as used in Fig. 8, must therefore have a special specification and can be an expensive component. In contrast, a capillary tube and a solenoid valve are simple in design and also significantly more heat-resistant, so that common components can be used for the oil return path and the flow rate adjustment mechanism can be designed cost-effectively. Seventh embodiment. In a seventh embodiment, a third specific example of the flow rate adjustment mechanism described in the first embodiment is explained. Fig. 10 is a representation showing a configuration of a refrigeration circuit device according to the seventh embodiment. In a refrigeration circuit device 1007 shown in Fig. 10, the oil return path RP branches at a branching point BP1 into a flow path RP1 and a flow path RP2, which are subsequently joined at a merging point MP1. The flow rate adjustment mechanism 16 comprises 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. In the seventh embodiment, the oil quantity measuring device 17 can have one of the configurations described in the second to fourth embodiments. Furthermore, the control unit 600 can apply the control described in the first embodiment to regulate a flow rate. As shown in Fig. 10, the oil return path RP branches into parallel flow paths RP1 and RP2, which are equipped with capillary lines 16C and 16D respectively, and one flow path RP1 is equipped with a solenoid valve 16B. The control unit 600 can adjust a flow rate by opening the solenoid valve 16B when the flow rate is to be increased and closing the solenoid valve 16B when the flow rate is to be decreased. In the configuration shown in Fig. 9, the flow rate is set to zero when the flow rate decreases, whereas in the configuration shown in Fig. 10, a certain amount of refrigeration oil can be returned to the compressor 10 even when the flow rate decreases. Eighth embodiment. In the first embodiment, during operation of the refrigeration circuit device, the quantity of refrigerant flowing through the oil return path RP is continuously monitored, and the flow rate adjustment mechanism 16 regulates a flow rate. The flow rate adjustment mechanism 16 also has a moving part, so it is advantageous with regard to the durability of the device if the moving part is moved less frequently. Accordingly, in an eighth embodiment, the control shown in Fig. 2 is only applied in a situation where the refrigerant flows easily into the oil return path RP. Fig. 11 is a flow diagram illustrating how a flow rate adaptation mechanism according to the eighth embodiment is controlled. In step S11, the control unit 600 determines whether a condition for determining whether the flow rate adaptation control should be applied is met. For example, control unit 600 determines that the condition of step S11 is met if the operating frequency of compressor 10 is lower than a reference frequency. The reference frequency can be a frequency that is, for example, half the upper limit of the compressor's operating frequency. When compressor 10 operates at a low frequency, it discharges a reduced amount of refrigeration oil. The oil separator 11 contains a reduced amount of refrigeration oil, and refrigerant is thus more easily returned to the oil return path (RP). Conversely, when oil separator 11 contains a large amount of refrigeration oil, the oil return path (RP) carries mostly refrigeration oil, and the COP is unlikely to decrease due to the presence of the oil return path. Therefore, the determination of whether to apply the flow rate adaptation control is made, as described above, based on the compressor's operating frequency. It should be noted that the condition for applying the flow rate matching control is not limited to this. For example, the control unit 600 can determine that the condition in step S11 for applying the flow rate matching control is met if a pressure difference between the inlet and outlet of compressor 10 is less than a reference threshold. In this case, the reference threshold can be half of a maximum value of the pressure difference. For a given diameter of a fluid flow limiting unit of the flow rate adaptation mechanism, a larger differential pressure increases the amount of fluid passing through the oil return path RP, thus promoting refrigerant return. The determination of whether the flow rate adaptation control should be applied can therefore be made, as described above, based on the magnitude of the differential pressure. If the condition for applying the flow rate adaptation control is not met (NO in S11), the control unit 600 sets the flow rate of the flow rate adaptation mechanism 16 to a default value in step S15. This allows the flow rate adaptation mechanism 16 to have a moving part that needs to be moved less frequently, which is beneficial for the product's longevity. If the condition for applying the flow rate adaptation control is met (YES in S11), the control unit 600 proceeds to step S12 to determine, based on an output from the oil quantity measuring device 17, whether there is a reduced quantity of refrigeration oil in the oil separator 11. If there is an insufficient quantity of refrigeration oil in the oil separator 11, there is a possibility that refrigerant may flow through the oil return path RP. If the oil separator has a reduced amount of refrigeration oil (JA in S12), the control unit 600 regulates the flow rate adjustment mechanism 16 to reduce the flow rate of a fluid flowing through the oil return path RP in step S13. If, on the other hand, the oil separator does not have a reduced amount of refrigeration oil (NO in S12), the control unit 600 regulates the flow rate adjustment mechanism 16 to increase the flow rate of the fluid flowing through the oil return path RP in step S14. Thus, by controlling the flow rate adjustment mechanism 16, a certain amount of refrigeration oil can be retained in the oil separator 11 to reduce the amount of bypass refrigerant flowing through the oil return path RP when the oil separator contains a reduced amount of refrigeration oil. This prevents refrigerant that does not contribute to cooling capacity from circulating through the compressor 10 and the oil return path RP, thereby preventing increased workload on the compressor 10 and a reduced COP. In the eighth embodiment, the oil quantity measuring device 17 can have one of the configurations described in the second to fourth embodiments. Furthermore, the flow rate adjustment mechanism 16 can have any of the configurations described in the fifth to seventh embodiments. The eighth embodiment can achieve a similar effect to the first to seventh embodiments and, in addition, can design the flow rate adjustment mechanism 16 with regard to durability for a longer period than in the first to seventh embodiments. (Summary) Reference is made again below to the drawings in order to summarize the embodiments. (1) A refrigeration circuit device 1001 of the present disclosure, shown in Fig. 1, comprises 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 form a refrigerant circuit C1 through which refrigerant circulates. The refrigeration circuit device 1001 further comprises an oil return path RP, which is configured to return refrigeration oil from the oil separator 11 to the inlet of the compressor 10, a flow rate adjustment mechanism 16, which is arranged on the oil return path RP, and an oil quantity measuring device 17, which is configured to detect a quantity of refrigeration oil stored in the oil separator 11.The flow rate adjustment mechanism 16 is set up to operate in response to an output from the oil quantity measuring device 17 in order to control a flow rate of a fluid passing through the oil return path RP. (2) In section 1, as shown in Fig. 3, the oil quantity measuring device 17 comprises an oil level sensor 17A which is configured to detect a level of oil on a surface in the oil separator. (3) In section 1, as shown in Fig. 4, the oil quantity measuring device 17 comprises an oil measuring path 17B connected to the oil separator 11 at an intake inlet P3 which is level higher than an oil discharge outlet P4, at which the oil return path RP is connected at one end to the oil separator 11, and which is connected to the oil return path RP at a junction point P5 provided on the oil return path RP, a cooling device 17D which is configured to cool a fluid passing through the oil measuring path 17B, and a temperature sensor 17E which is configured to detect a temperature of a section of the oil measuring path 17B after passing through the cooling device 17D. (4) In section 3, as shown in Fig. 4, the cooling device 17D includes a heat exchanger 171 which is configured to exchange heat between refrigerant which is routed in refrigerant circuit C1 from the heat exchanger 15 to the compressor 10 and the fluid which passes through the oil measuring path 17B. (5) In paragraph 3, as shown in Fig. 7, the refrigeration circuit device 1004 further comprises a bypass flow path BP, which is configured to divert a portion of the refrigerant flowing in refrigerant circuit C1 from the heat exchanger 13 to the expansion valve 14 and return that portion to the compressor 10. The cooling device 17D comprises a heat exchanger 172, which is configured to exchange heat between the refrigerant passing through the bypass flow path BP and the fluid passing through the oil measuring path 17B. (6) In one of sections 1 to 5, as shown in Fig. 8, the flow rate adjustment mechanism 16 comprises a linear expansion valve 16A. (7) In one of sections 1 to 5, as shown in Fig. 9, the flow rate adjustment mechanism 16 comprises a solenoid valve 16B and a capillary line 16C arranged in series on the oil return path RP. (8) In one of sections 1 to 5, as shown in Fig. 10, the oil return path RP branches at a branching point BP1 into a flow path RP1 and a flow path RP2, and the flow paths RP1 and RP2 are subsequently merged at a merging point MP. The flow rate adjustment mechanism 16 comprises a solenoid valve 16B and a capillary line 16C arranged in series in flow path RP1, and a capillary line 16D arranged in flow path RP2. (9) In one of sections 1 to 8, the refrigeration circuit device 1001 further comprises a control unit 600, which is configured to control the compressor 10 and a flow rate adjustment mechanism 16. As shown in Fig. 11, the control unit 600 is configured to apply a first control (S15) or a second control (S12 to S14) while the compressor 10 is operating. The control unit 600 is configured to set a flow rate of the flow rate adjustment mechanism 16 in the first control. The control unit 600 is configured to control a flow rate of the flow rate adjustment mechanism 16 in response to the output of the oil quantity measuring device 17 in the second control. (10) In section 9, as shown in Fig. 11, the control unit 600 is set up to apply the first control (S15) when the operating frequency of the compressor 10 is higher than a threshold value, and to apply the second control (S12 to S14) when the operating frequency of the compressor is lower than the threshold value. (11) In section 9, as shown in Fig. 11, the control unit 600 is configured to apply the first control (S15) when the pressure difference between the inlet and outlet of the compressor 10 is less than a threshold value, and to apply the second control (S12 to S14) when the pressure difference is lower than the threshold value. It goes without saying that the embodiments disclosed herein are in every respect illustrative and not limiting. The scope of this disclosure is defined by the terms of the claims and not by the above description of the embodiments, and is intended to include all modifications within the meaning and scope that correspond to the terms of the claims. REFERENCE MARK LIST 10 Compressor, 11 Oil separator, 13, 15, 19, 171, 172 Heat exchanger, 14, 20 Expansion valve, 16 Flow rate adjustment mechanism, 16A Linear expansion valve, 16B, 17C Solenoid valve, 16C, 16D Capillary line, 17 Oil quantity measuring device, 17A Oil level sensor, 17B Oil measuring path, 17D Cooling device, 17E Temperature sensor, 600 Control unit, 601 CPU, 602 Memory, 1001-1007 Refrigeration circuit device, BP Bypass flow path, BP1 Branch point, C1 Refrigerant circuit, MP, MP1, P5 Merge point, P1 Gas flow inlet, P2 Gas discharge outlet, P3 Intake inlet, P4 Oil discharge outlet, RP oil return path, RP1, RP2 flow path.

Claims

Refrigeration circuit device (1001), comprising: a compressor (10), an oil separator (11), a first heat exchanger (13), an expansion valve (14) and a second heat exchanger (15), wherein the compressor (10), the oil separator (11), the first heat exchanger (13), the expansion valve (14) and the second heat exchanger (15) form a refrigerant circuit (C1) through which refrigerant circulates; an oil return path (RP) configured to return refrigeration oil from the oil separator (11) to an inlet of the compressor (10); a flow rate adjustment mechanism (16) arranged in the oil return path (RP);and an oil quantity measuring device (17) configured to measure a quantity of refrigeration oil stored in the oil separator (11), wherein the flow rate adjustment mechanism (16) is configured to operate in response to an output from the oil quantity measuring device (17) to control a flow rate of a fluid passing through the oil return path (RP), wherein the oil quantity measuring device (17) comprises: an oil measurement path (17B) connected to the oil separator (11) at a point which is level higher than a point at which an end of the oil return path (RP) is connected to the oil separator (11), and which is connected to the oil return path (RP) at a connection point provided on the oil return path (RP); a cooling device (17D) configured to cool a fluid passing through the oil measurement path (17B);and a temperature sensor (17E) configured to detect the temperature of a section of the oil measuring path (17B) after it has passed through the cooling device (17D). Refrigeration circuit device according to claim 1, wherein the oil quantity measuring device (17) comprises an oil level sensor (17A) which is configured to detect a level of oil on a surface in the oil separator (11). Refrigeration circuit device according to claim 1, wherein the cooling device (17D) comprises a third heat exchanger (171) which is configured to exchange heat between refrigerant which is conveyed in the refrigerant circuit (C1) from the second heat exchanger (15) to the compressor (10) and the fluid which passes through the oil measuring path (17B). Refrigeration circuit device (1004) according to claim 1, further comprising a bypass flow path (BP) configured to divert a portion of the refrigerant flowing in the refrigerant circuit (C1) from the first heat exchanger (13) to the expansion valve (14) and return this portion to the compressor (10), wherein the cooling device (17D) comprises a third heat exchanger (172) configured to exchange heat between refrigerant flowing through the bypass flow path (BP) and the fluid flowing through the oil sensing path (17B). Refrigeration circuit device according to one of claims 1 to 4, wherein the flow rate adjustment mechanism (16) comprises a linear expansion valve (16A). Refrigeration circuit device according to one of claims 1 to 4, wherein the flow path adaptation mechanism (16) comprises a solenoid valve (16B) and a capillary line (16C) which are arranged in series on the oil return path (RP). Refrigeration circuit device according to one of claims 1 to 4, wherein the oil return path (RP) branches at a branching point (RP1) into a first flow path (RP1) and a second flow path (RP2), wherein the first and the second flow paths (RP1, RP2) are subsequently merged at a merging point (MP), and the flow rate adjustment mechanism (16) comprises: a solenoid valve (16B) and a first capillary tube (16C) arranged in series in the first flow path (RP1); and a second capillary tube (16D) arranged at the second flow path (RP2). Refrigeration circuit device (1001) according to one of claims 1 to 7, further comprising a control unit (600) configured to control the compressor (10) and the flow rate adjustment mechanism (16), wherein the control unit (600) is configured to apply a first control or a second control while the compressor (10) is in operation, wherein the control unit (600) is configured to set a flow rate of the flow rate adjustment mechanism (16) in the first control, wherein the control unit (600) is configured to control a flow rate of the flow rate adjustment mechanism (16) in response to the output of the oil quantity measuring device (17) in the second control. Refrigeration circuit device according to claim 8, wherein the control unit (600) is configured to apply the first control when the operating frequency of the compressor (10) is higher than a threshold value, and to apply the second control when the operating frequency of the compressor (10) is lower than the threshold value. Refrigeration circuit device according to claim 8, wherein the control unit (600) is configured to apply the first control when a pressure difference between the inlet of the compressor (10) and an outlet of the compressor (10) is less than a threshold value, and to apply the second control when the pressure difference is greater than the threshold value.

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