Refrigeration Cycle Equipment

Abstract

This refrigeration cycle device has: a refrigerant circuit in which a compressor, a condenser, and an evaporator are connected by refrigerant piping; a low pressure sensor for detecting low pressure; a flow regulation valve provided between the condenser and the evaporator; and, a controller. The controller has: a valve control means for switching the flow regulation valve from an open state to a closed state after keeping the flow regulation valve in the open state until one or both of a first condition, in which the low pressure is equal to or greater than a predetermined reference value with the compressor stopped, and a second condition, in which the elapsed time from when the compressor is stopped is equal to or greater than a predetermined reference time, are satisfied; a compressor control means for causing the compressor to execute a pump-down operation when the flow regulation valve switches from the open state to the closed state; and, an assessment means for assessing, when the compressor completes the pump-down operation, whether a refrigerant is leaking on the basis of the state of the refrigerant or an apparatus constituting the refrigerant circuit.

Description

[Technical field]

[0001] The present disclosure relates to a refrigeration cycle device including a refrigerant circuit. [Background technology]

[0002] 2. Description of the Related Art Conventionally, refrigeration cycle devices such as refrigeration systems and air conditioners circulate a refrigerant through a refrigeration cycle circuit to perform cooling or heating operation, and exchange heat between the refrigerant and a fluid such as air, water, or brine.

[0003] In a refrigeration cycle device, an excess or shortage of the amount of refrigerant not only reduces the capacity of the refrigeration cycle device, but also causes damage to the devices that constitute the refrigeration cycle circuit. In order to prevent such problems from occurring, there is a refrigeration cycle device that has a function for determining whether the amount of refrigerant filled in the refrigeration cycle circuit is excessive or insufficient.

[0004] Conventionally, an example of a refrigeration device that determines whether or not the amount of refrigerant is insufficient has been proposed (for example, see Patent Document 1). The refrigeration device disclosed in Patent Document 1 determines whether or not the refrigerant filled in the refrigerant circuit is leaking based on the temperature efficiency of the subcooling heat exchanger, which is a value obtained by dividing the degree of subcooling of the refrigerant at the outlet of the subcooling heat exchanger by the maximum temperature difference of the subcooling heat exchanger. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5674452 Summary of the Invention [Problem to be solved by the invention]

[0006] The refrigeration device disclosed in Patent Document 1 judges the presence or absence of a refrigerant leak based on a temperature efficiency calculated using the degree of subcooling at the outlet of the subcooling heat exchanger while the compressor is operating and a preset judgment threshold value. However, when the compressor repeatedly operates and stops in a short cycle, the temperature and pressure of the refrigerant flowing through each refrigeration device including the subcooling heat exchanger are not stable. In this case, the refrigeration device may not be able to correctly judge the presence or absence of a refrigerant leak, resulting in an erroneous judgment.

[0007] On the other hand, in order to prevent erroneous judgment, when the refrigeration device disclosed in Patent Document 1 tries to judge the presence or absence of refrigerant leakage while the compressor is not operating, the change in the temperature and pressure of the refrigerant in each refrigerant device becomes small. Therefore, the difference in the temperature and pressure of the refrigerant in each refrigerant device between a normal case where there is no refrigerant leakage and a case where there is a refrigerant leakage is not easily reflected in the temperature efficiency of the subcooling heat exchanger. As a result, the accuracy of the judgment of the presence or absence of refrigerant leakage may be reduced.

[0008] The present disclosure has been made to solve the above-mentioned problems, and provides a refrigeration cycle device that can accurately detect refrigerant leakage when the compressor is stopped. [Means for solving the problem]

[0009] The refrigeration cycle device according to the present disclosure includes a refrigerant circuit in which a compressor, a condenser, and an evaporator are connected by a refrigerant pipe and a refrigerant circulates through the refrigerant pipe, a low pressure sensor provided between the compressor and the evaporator and detecting a low pressure which is a pressure of the refrigerant flowing through the refrigerant pipe, a flow rate control valve provided between the condenser and the evaporator, and a controller for controlling the compressor and the flow rate control valve, and the controller is configured to detect a time elapsed since the compressor was stopped. In the pump-down operation, the compressor is operated for a certain period of time. a valve control means for switching the flow rate control valve from the open state to a closed state after the flow rate control valve is kept in an open state until a reference time has elapsed; and a valve control means for recovering the refrigerant in the refrigerant circuit into the condenser when the flow rate control valve is switched from the open state to the closed state. The aboveThe refrigerant control device includes a compressor control means for causing the compressor to perform pump-down operation, and a determination means for determining whether or not the refrigerant is leaking based on the state of the equipment constituting the refrigerant circuit or the state of the refrigerant when the compressor finishes the pump-down operation. Effect of the Invention

[0010] According to the present disclosure, when the compressor is stopped, a series of processes are performed from increasing the low pressure in the refrigerant circuit to recovering the refrigerant in the condenser. Therefore, the temperature and pressure of the refrigerant in each device and between the devices in the refrigerant circuit change by a large amount, and the difference from the temperature and pressure of the refrigerant in a normal state without refrigerant leakage becomes noticeable. Since a state suitable for refrigerant leakage determination is generated, refrigerant leakage can be detected with high accuracy even when the compressor is stopped. [Brief description of the drawings]

[0011] [Figure 1] 1 is a refrigerant circuit diagram showing a configuration example of a refrigeration cycle device according to a first embodiment. [Diagram 2] 2 is a functional block diagram showing a configuration example of a controller shown in FIG. 1. [Diagram 3] 3 is a hardware configuration diagram showing an example of the configuration of a controller shown in FIG. 2. [Figure 4] 3 is a hardware configuration diagram showing another example of the configuration of the controller shown in FIG. 2. [Diagram 5] 4 is a flowchart showing an example of an operation procedure of the refrigeration cycle device according to the first embodiment. [Figure 6] FIG. 4 is a refrigerant circuit diagram showing another configuration example of the refrigeration cycle device according to the first embodiment. [Figure 7] 10 is a functional block diagram showing a configuration example of a controller shown in FIG. 1 in a refrigeration cycle device according to a second embodiment. FIG. [Figure 8] FIG. 11 is a refrigerant circuit diagram showing a configuration example of a refrigeration cycle device according to a third embodiment. [Figure 9]9 is a functional block diagram showing an example of the configuration of a controller shown in FIG. 8. [Figure 10] FIG. 11 is a refrigerant circuit diagram showing a configuration example of a refrigeration cycle device according to a fourth embodiment. [Figure 11] 11 is a functional block diagram showing an example of the configuration of a controller shown in FIG. 10. [Figure 12] FIG. 11 is a refrigerant circuit diagram showing a configuration example of a refrigeration cycle device according to a fifth embodiment. [Figure 13] 13 is a functional block diagram showing an example of the configuration of a controller shown in FIG. 12. [Figure 14] 13 is a flowchart showing an operation procedure of the refrigeration cycle device according to the fifth embodiment. [Figure 15] FIG. 13 is a refrigerant circuit diagram showing a configuration example of a refrigeration cycle device according to a sixth embodiment. [Figure 16] FIG. 13 is a refrigerant circuit diagram showing a configuration example of a refrigeration cycle device according to a seventh embodiment. [Figure 17] 17 is a functional block diagram showing an example of the configuration of a controller shown in FIG. 16. [Figure 18] FIG. 13 is a refrigerant circuit diagram showing a configuration example of a refrigeration cycle device according to an eighth embodiment. [Figure 19] 19 is a functional block diagram showing an example of the configuration of a controller shown in FIG. 18. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Embodiment 1 The configuration of the refrigeration cycle device of the present embodiment 1 will be described. Fig. 1 is a refrigerant circuit diagram showing a configuration example of the refrigeration cycle device according to the embodiment 1. As shown in Fig. 1, the refrigeration cycle device 200 has a heat source side unit 100 and a load side unit 110.

[0013] The heat source side unit 100 is installed outdoors. The heat source side unit 100 generates heat to be supplied to the load side unit 110. The load side unit 110 is installed in a space to be air-conditioned, which is a source of heat load of the refrigeration cycle device 200. The load side unit 110 supplies the heat supplied from the heat source side unit 100 to the heat load. In the first embodiment, the space to be air-conditioned is a room in which one or both of objects and people that generate heat are present, and a case will be described in which the load side unit 110 cools the air in the room.

[0014] The heat source side unit 100 has a compressor 1, a heat source side heat exchanger functioning as a condenser 4, and a controller 30. The load side unit 110 has a pressure reducing device 11, and a load side heat exchanger functioning as an evaporator 12. The compressor 1, the condenser 4, the pressure reducing device 11, and the evaporator 12 are connected by a refrigerant piping 21 to form a refrigerant circuit 20 in which the refrigerant circulates. In the present embodiment 1, a flow rate control valve 10 is provided in the refrigerant piping 21 between the condenser 4 and the pressure reducing device 11.

[0015] The compressor 1 draws in a low-temperature and low-pressure refrigerant, compresses the drawn refrigerant, and discharges it as a high-temperature and high-pressure refrigerant. The compressor 1 is, for example, an inverter compressor whose capacity can be adjusted by changing the operating frequency fc. The condenser 4 exchanges heat between a fluid and the refrigerant. The condenser 4 condenses the refrigerant by dissipating heat from the refrigerant. The fluid that exchanges heat with the refrigerant in the condenser 4 is outside air. The condenser 4 is, for example, a fin-and-tube type heat exchanger having a heat transfer tube and a plurality of heat dissipation fins. The compressor 1 is connected to the controller 30 via a signal line 25.

[0016] The pressure reducing device 11 reduces the pressure of the liquid refrigerant flowing in from the condenser 4 and expands it. The pressure reducing device 11 also serves to adjust the flow rate of the refrigerant flowing in from the condenser 4. The pressure reducing device 11 is, for example, an expansion valve. In the present embodiment 1, the pressure reducing device 11 is an expansion valve. The evaporator 12 exchanges heat between a fluid and the refrigerant. The evaporator 12 absorbs heat from the refrigerant decompressed and expanded by the pressure reducing device 11 to evaporate the refrigerant. The fluid that exchanges heat with the refrigerant in the evaporator 12 is the air in the space to be air-conditioned. The evaporator 12 is, for example, a fin-and-tube type heat exchanger having a heat transfer tube and a plurality of heat dissipation fins. The pressure reducing device 11 is connected to the controller 30 via a signal line (not shown).

[0017] In the heat source side unit 100, a low pressure sensor 9 is provided on the refrigerant suction port side of the compressor 1. The low pressure sensor 9 detects the suction pressure, which is the pressure of the refrigerant sucked into the compressor 1. The suction pressure corresponds to the low pressure Lp, which is the pressure on the low pressure side in the refrigerant circuit 20. In addition, a high pressure sensor 3 is provided on the refrigerant discharge port side of the compressor 1. The high pressure sensor 3 detects the discharge pressure, which is the pressure of the refrigerant discharged from the compressor 1. The discharge pressure corresponds to the high pressure Hp, which is the pressure on the high pressure side in the refrigerant circuit 20. The low pressure sensor 9 and the high pressure sensor 3 are connected to the controller 30 via a signal line (not shown).

[0018] The load side unit 110 is provided with a room temperature sensor 23 that detects the room temperature. The room temperature sensor 23 is, for example, a thermistor. The room temperature sensor 23 is connected to the controller 30 via a signal line (not shown). The load side unit 110 is provided with an alarm device 50 that notifies a user that a refrigerant has leaked. The alarm device 50 is connected to the controller 30 via a signal line (not shown).

[0019] The notification device 50 is equipped with, for example, one or both of a display (not shown) that displays information and a speaker (not shown) that outputs an alarm sound. When the notification device 50 is equipped with a display (not shown), upon receiving a refrigerant leakage alarm signal from the controller 30 indicating that refrigerant is leaking, the notification device 50 displays a message indicating that refrigerant is leaking on the display (not shown). When the notification device 50 is equipped with a speaker (not shown), upon receiving a refrigerant leakage alarm signal from the controller 30, the notification device 50 outputs an alarm sound from the speaker (not shown).

[0020] The flow rate regulating valve 10 is, for example, a solenoid valve. The opening and closing of the flow rate regulating valve 10 is controlled by a controller 30. The flow rate regulating valve 10 maintains an open state while the compressor 1 is in operation. The flow rate regulating valve 10 is connected to the controller 30 via a signal line (not shown).

[0021] Next, the configuration of the controller 30 will be described. Fig. 2 is a functional block diagram showing an example of the configuration of the controller shown in Fig. 1. The controller 30 is, for example, a microcomputer. The controller 30 has a refrigeration cycle control means 31, a valve control means 32, a compressor control means 33, a determination means 34, and a timer 35 that measures time.

[0022] When the operation mode of the load side unit 110 is cooling operation, the refrigeration cycle control means 31 controls the compressor 1 and the pressure reducing device 11 so that the room temperature detected by the room temperature sensor 23 matches the set temperature. Specifically, the refrigeration cycle control means 31 calculates the operation frequency fc of the compressor 1 and the opening degree ve of the pressure reducing device 11 that brings the room temperature close to the set temperature or maintains the room temperature at the set temperature at a predetermined constant period. Then, the refrigeration cycle control means 31 transmits information on the calculated opening degree ve to the valve control means 32 and transmits information on the calculated operation frequency fc to the compressor control means 33. The set temperature is input to the controller 30 by the user.

[0023] When the valve control means 32 receives information on the opening degree ve from the refrigeration cycle control means 31, it controls the opening degree of the pressure reducing device 11 so that the opening degree becomes ve. Furthermore, the valve control means 32 opens the flow control valve 10 until a first condition is satisfied in which the low pressure Lp detected by the low pressure sensor 9 becomes equal to or greater than a predetermined reference value Pref when the compressor 1 is stopped. The valve control means 32 may open the flow control valve 10 until a second condition is satisfied in which the elapsed time from when the compressor 1 is stopped becomes equal to or greater than a predetermined reference time tref. The valve control means 32 determines the elapsed time from when the compressor 1 is stopped by referring to the time measured by the timer 35. Furthermore, the valve control means 32 may open the flow control valve 10 until both the first condition and the second condition are satisfied. When one or both of the first condition and the second condition are satisfied, the valve control means 32 switches the flow control valve 10 from the open state to the closed state.

[0024] When the compressor control means 33 receives information on the operation frequency fc from the refrigeration cycle control means 31, it operates the compressor 1 at the operation frequency fc. Furthermore, when the flow control valve 10 switches from an open state to a closed state while the compressor 1 is stopped, the compressor control means 33 causes the compressor 1 to execute a pump-down operation. The pump-down operation is a operation of the compressor 1 for the purpose of recovering the refrigerant in the condenser 4 until the low pressure Lp falls to a predetermined end pressure value.

[0025] When the compressor 1 finishes the pump-down operation, the determination means 34 performs a refrigerant leakage determination process to determine whether or not the refrigerant is leaking based on the state of the devices and refrigerant that constitute the refrigerant circuit 20. For example, when the determination parameter for determining the presence or absence of refrigerant leakage is the high-pressure pressure Hp, the determination means 34 determines whether or not the high-pressure pressure Hp is equal to or lower than a predetermined pressure threshold Pth. When the refrigerant is leaking, the high-pressure pressure Hp after the pump-down operation tends to be lower than in a normal case where the refrigerant is not leaking. Therefore, when the high-pressure pressure Hp is equal to or lower than the pressure threshold Pth as a result of the determination, the determination means 34 determines that the refrigerant is leaking. On the other hand, when the high-pressure pressure Hp is greater than the pressure threshold Pth, the determination means 34 determines that the refrigerant is not leaking. When the determination means 34 determines that the refrigerant is leaking, it transmits a refrigerant leakage notification signal to the notification device 50.

[0026] Here, an example of the hardware of the controller 30 shown in Fig. 2 will be described. Fig. 3 is a hardware configuration diagram showing an example of the configuration of the controller shown in Fig. 2. When the various functions of the controller 30 are executed by hardware, the controller 30 shown in Fig. 2 is configured by a processing circuit 90 as shown in Fig. 3. Each function of the refrigeration cycle control means 31, the valve control means 32, the compressor control means 33, the determination means 34, and the timer 35 shown in Fig. 2 is realized by the processing circuit 90.

[0027] When each function is executed by hardware, the processing circuit 90 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination of these. Each of the functions of the refrigeration cycle control means 31, the valve control means 32, the compressor control means 33, the determination means 34, and the timer 35 may be realized by the processing circuit 90. Also, the functions of the refrigeration cycle control means 31, the valve control means 32, the compressor control means 33, the determination means 34, and the timer 35 may be realized by one processing circuit 90.

[0028] Another example of hardware of the controller 30 shown in Fig. 2 will be described. Fig. 4 is a hardware configuration diagram showing another example of the configuration of the controller shown in Fig. 2. When the various functions of the controller 30 are executed by software, the controller 30 shown in Fig. 2 is composed of a processor 91 such as a CPU (Central Processing Unit) and a memory 92 as shown in Fig. 4. The functions of the refrigeration cycle control means 31, the valve control means 32, the compressor control means 33, the determination means 34, and the timer 35 are realized by the processor 91 and the memory 92. Fig. 4 shows that the processor 91 and the memory 92 are connected to each other via a bus 93 so as to be able to communicate with each other.

[0029] When each function is executed by software, the functions of the refrigeration cycle control means 31, the valve control means 32, the compressor control means 33, the determination means 34 and the timer 35 are realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in the memory 92. The processor 91 realizes the function of each means by reading and executing the programs stored in the memory 92.

[0030] For example, non-volatile semiconductor memories such as ROM (Read Only Memory), flash memory, EPROM (Erasable and Programmable ROM), and EEPROM (Electrically Erasable and Programmable ROM) are used as the memory 92. Also, volatile semiconductor memories such as RAM (Random Access Memory) may be used as the memory 92. Furthermore, removable recording media such as magnetic disks, flexible disks, optical disks, CDs (Compact Discs), MDs (Mini Discs), and DVDs (Digital Versatile Discs) may be used as the memory 92.

[0031] 1 shows a configuration in which the controller 30 is provided in the heat source unit 100, but the controller 30 may be provided in the load unit 110. FIG. 1 shows a configuration in which the flow rate control valve 10 and the pressure reducing device 11 are provided in the load unit 110, but one or both of the flow rate control valve 10 and the pressure reducing device 11 may be provided in the heat source unit 100. In addition, in the first embodiment, the case where the notification device 50 is provided in the refrigeration cycle device 200 is described, but the notification device 50 does not have to be provided. The case where the controller 30 and the devices such as the compressor 1 and the sensors such as the low pressure sensor 9 are connected by wires has been described, but they may be connected wirelessly.

[0032] The refrigeration cycle device 200 of this embodiment 1 is characterized in that while the compressor 1 is stopped, the flow control valve 10 is opened to increase the low pressure Lp, and then the flow control valve 10 is closed, and then a pump-down operation is performed before determining whether or not there is a refrigerant leak.

[0033] Next, the operation of the refrigeration cycle apparatus 200 of the first embodiment will be described. Fig. 5 is a flow chart showing an example of an operation procedure of the refrigeration cycle apparatus according to the first embodiment. Here, the first condition out of two conditions for maintaining the flow rate control valve 10 in an open state from when the compressor 1 stops will be described. The refrigeration cycle apparatus 200 performs the process shown in Fig. 5, for example, during a time period when it is not operating.

[0034] When a command to stop the refrigeration cycle device 200 is input from a user, the refrigeration cycle control means 31 transmits a stop signal, which is a signal to instruct stopping the compressor 1, to the compressor control means 33. When the compressor control means 33 receives the stop signal from the refrigeration cycle control means 31, it stops the compressor 1 (step S101).

[0035] The valve control means 32 maintains the flow rate control valve 10 in an open state while the compressor 1 is stopped (step S102). As a result, the refrigerant on the high-pressure side moves to the low-pressure side, and the low-pressure pressure Lp increases. The controller 30 waits until the low-pressure pressure Lp increases to the reference value Pref. The purpose of increasing the low-pressure pressure Lp is to ensure a certain period of operation of the compressor 1 in the subsequent pump-down operation, thereby increasing the range of change in temperature and pressure of the refrigerant in each device of the refrigerant circuit 20 and between the devices.

[0036] The valve control means 32 judges whether the low pressure Lp is equal to or greater than the reference value Pref (step S103). When the low pressure Lp is equal to or greater than the reference value Pref, the valve control means 32 switches the flow rate control valve 10 from an open state to a closed state (step S104). When the flow rate control valve 10 switches from an open state to a closed state, the compressor control means 33 starts the compressor 1 (step S105) and causes the compressor 1 to perform a pump-down operation. This causes the refrigerant in the refrigerant circuit 20 to be recovered in the condenser 4. The compressor control means 33 judges whether the recovery of the refrigerant in the refrigerant circuit 20 has been completed (step S106). Specifically, the compressor control means 33 judges whether the low pressure Lp has been reduced to an end pressure value. When the low pressure Lp has been reduced to an end pressure value, the compressor control means 33 judges that the recovery of the refrigerant in the condenser 4 has been completed. When it is determined in the process of step S106 that the recovery of the refrigerant has been completed, the compressor control means 33 stops the compressor 1 (step S107) and ends the pump-down operation.

[0037] After the process of step S107, the determination means 34 determines whether or not the refrigerant is leaking using the determination parameter. In the present embodiment 1, the case where the determination parameter is the high pressure pressure Hp will be described. The determination means 34 determines whether or not the high pressure pressure Hp is equal to or lower than the pressure threshold value Pth (step S108). If the high pressure pressure Hp is equal to or lower than the pressure threshold value Pth, the determination means 34 determines that the refrigerant is leaking (step S109). This is because if the refrigerant is leaking, the high pressure pressure Hp after the pump-down operation will be lower than in the normal case. In step S109, the determination means 34 may transmit a refrigerant leakage notification signal to the notification device 50.

[0038] On the other hand, when the result of the judgment in step S108 is that the high pressure Hp is greater than the pressure threshold value Pth and the judgment means 34 judges that the refrigerant is not leaking, the controller 30 ends the process. Next, after the refrigeration cycle apparatus 200 starts operation, the controller 30 suspends the process in step S101 until an instruction to stop the refrigeration cycle apparatus 200 is input from the user.

[0039] In this way, the refrigeration cycle apparatus 200 increases the low pressure Lp while the compressor 1 is stopped, closes the flow control valve 10, and then performs pump-down operation before determining whether or not there is a refrigerant leak. By performing a series of processes from increasing the low pressure LP to recovering the refrigerant to the condenser 4, the temperature and pressure of the refrigerant in each device of the refrigerant circuit 20 and between the devices vary widely, and the difference from the temperature or pressure of the refrigerant in a normal state without refrigerant leakage becomes noticeable. Therefore, the refrigeration cycle apparatus 200 can accurately detect a refrigerant leak even when the compressor 1 is stopped, and can take early action against the refrigerant leak.

[0040] 5, when the compressor control means 33 stops the compressor 1, the valve control means 32 maintains the flow rate adjustment valve 10 in the open state. However, the valve control means 32 may close the flow rate adjustment valve 10 once. In this case, the valve control means 32 may switch the flow rate adjustment valve 10 from the closed state to the open state in step S102 after a period of time has elapsed until the refrigerant pressures on the high-pressure side and the low-pressure side of the refrigerant circuit 20 have stabilized. The period of time until the refrigerant pressures on the high-pressure side and the low-pressure side of the refrigerant circuit 20 have stabilized is, for example, 30 minutes or more.

[0041] An example of the case where the valve control means 32 closes the flow rate control valve 10 after the compressor 1 stops will be described. For example, if the refrigeration cycle apparatus 200 does not operate for several days after the compressor 1 stops, the valve control means 32 closes the flow rate control valve 10. In this case, the controller 30 judges the presence or absence of refrigerant leakage once a day according to the flow shown in FIG. 5. In this case, even if the refrigeration cycle apparatus 200 stops for a long period of time, the controller 30 judges the presence or absence of refrigerant leakage once a day. This makes it possible to prevent refrigerant from leaking for a long period of time.

[0042] The refrigeration cycle device 200 of the present embodiment 1 includes a refrigerant circuit 20 in which a compressor 1, a condenser 4, and an evaporator 12 are connected by a refrigerant pipe 21 and a refrigerant circulates through the refrigerant pipe 21, a low pressure sensor 9, a flow rate control valve 10, and a controller 30. The low pressure sensor 9 is provided between the compressor 1 and the evaporator 12, and detects a low pressure Lp, which is the pressure of the refrigerant circulating through the refrigerant pipe 21. The flow rate control valve 10 is provided between the condenser 4 and the evaporator 12. The controller 30 controls the compressor 1 and the flow rate control valve 10. The controller 30 includes a valve control means 32, a compressor control means 33, and a determination means 34. The valve control means 32 opens the flow rate control valve 10 until one or both of the first and second conditions are satisfied while the compressor 1 is stopped, and then switches the flow rate control valve 10 from the open state to the closed state. The first condition is that the low pressure Lp becomes equal to or greater than a reference value Pref when the compressor 1 is stopped. The second condition is that the elapsed time from when the compressor 1 is stopped becomes equal to or greater than a reference time tref. When the flow control valve 10 switches from an open state to a closed state, the compressor control means 33 causes the compressor 1 to perform a pump-down operation for recovering the refrigerant in the refrigerant circuit 20 to the condenser 4. When the compressor 1 ends the pump-down operation, the determination means 34 determines whether or not the refrigerant is leaking based on the state of the devices or refrigerant constituting the refrigerant circuit 20.

[0043] Some conventional refrigeration systems determine the presence or absence of a refrigerant leak using the temperature and pressure values ​​of the refrigerant in the refrigerant equipment while the compressor is operating, as disclosed in Patent Document 1. However, when the compressor repeatedly operates and stops in short cycles, the temperature and pressure of the refrigerant flowing through each refrigerant equipment, including the subcooling heat exchanger, are not stable, and there is a risk of erroneous determination of the presence or absence of a refrigerant leak.

[0044] On the other hand, in order to prevent erroneous judgment, when a conventional refrigeration system tries to judge the presence or absence of a refrigerant leak while the compressor is not operating, the change in the temperature and pressure of the refrigerant in each refrigeration device becomes small. Therefore, the difference in the temperature and pressure of the refrigerant in the refrigeration device between a normal state where there is no refrigerant leak and a state where there is a refrigerant leak is not easily reflected in the judgment parameters. As a result, the accuracy of the judgment of the presence or absence of a refrigerant leak in the conventional refrigeration system may decrease.

[0045] In contrast, the refrigeration cycle device 200 of the present embodiment 1 opens the flow control valve 10 while the compressor 1 is stopped to increase the low pressure Lp, then closes the flow control valve 10, and performs pump-down operation before determining whether or not there is a refrigerant leak. According to the present embodiment 1, a series of processes from the increase in the low pressure LP to the recovery of the refrigerant to the condenser 4 are performed while the compressor 1 is stopped. As a result, the range of change in the temperature and pressure of the refrigerant of each device and between the devices in the refrigerant circuit 20 becomes large, and the difference from the temperature and pressure of the refrigerant in a normal case without refrigerant leakage becomes noticeable. Since a state suitable for refrigerant leakage determination is generated, the refrigeration cycle device 200 can accurately detect a refrigerant leak even when the change in the temperature or pressure of the refrigerant is small, that is, when the compressor 1 is stopped. As a result, the refrigeration cycle device 200 can take early action against a refrigerant leak.

[0046] (Variation 1) In the refrigeration cycle apparatus 200 of the first embodiment, the flow rate control valve 10 may have a function as the pressure reducing device 11. FIG. 6 is a refrigerant circuit diagram showing another configuration example of the refrigeration cycle apparatus according to the first embodiment. When the refrigeration cycle apparatus 200 is in cooling operation, the valve control means 32 may control the flow rate control valve 10 to function as the pressure reducing device 11. In this case, it is not necessary to separately provide the pressure reducing device 11 shown in FIG. 1 in the refrigerant circuit. On the other hand, in the configuration example described with reference to FIG. 1, the flow rate control valve 10 may have at least a function as an opening / closing valve that switches between an open state and a closed state.

[0047] Embodiment 2 In the first embodiment, a series of processes from the increase in the low pressure LP to the recovery of the refrigerant in the condenser 4 is performed to create a state suitable for refrigerant leakage determination, and then the presence or absence of refrigerant leakage is determined using the high pressure Hp as a determination parameter. In the second embodiment, the presence or absence of refrigerant leakage is determined using the time of the pump-down operation as a determination parameter. In the second embodiment, the same components as those described in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0048] The configuration of the refrigeration cycle device of the second embodiment will be described. The overall configuration of the refrigeration cycle device 200 of the second embodiment is similar to the configuration described with reference to Fig. 1, so detailed description of each component will be omitted. Fig. 7 is a functional block diagram showing a configuration example of the controller shown in Fig. 1 in the refrigeration cycle device according to the second embodiment.

[0049] The determination means 34 of the second embodiment determines whether or not the time of the pump-down operation is shorter than a predetermined time threshold value tith. When refrigerant is leaking, the amount of refrigerant in the refrigerant circuit 20 decreases, so that when the compressor 1 performs the pump-down operation after the low pressure Lp reaches the reference value, the time required for the pump-down operation to end tends to be shorter. In other words, the time required for the low pressure Lp to drop to the end pressure value tends to be shorter than in a normal case without refrigerant leakage. Therefore, when the time of the pump-down operation is shorter than the time threshold value tith, the determination means 34 determines that the refrigerant is leaking, and when the time of the pump-down operation is equal to or greater than the time threshold value tith, the determination means 34 determines that the refrigerant is not leaking.

[0050] Next, the operation of the refrigeration cycle apparatus 200 of the second embodiment will be described with reference to Fig. 5. Among the processes of steps S101 to S109 shown in Fig. 5, the processes other than steps S105, S107, and S108 are similar to those of the first embodiment, and therefore detailed descriptions thereof will be omitted.

[0051] In the second embodiment, when the compressor control means 33 starts the compressor 1 in step S105, the determination means 34 causes the timer 35 to start measuring time. When the compressor control means 33 stops the compressor 1 in step S107, the determination means 34 determines the time of the pump-down operation of the compressor 1 by referring to the time measured by the timer 35. In step S108, the determination means 34 determines whether the time of the pump-down operation is shorter than the time threshold value tith.

[0052] If the result of the determination in step S108 is that the time of the pump-down operation is shorter than the time threshold value tith, the determination means 34 determines that the refrigerant is leaking (step S109). This is because if the time required from the state in which the low pressure Lp is at the reference value Pref until the pump-down operation ends is shorter than the time threshold value tith required in the absence of refrigerant leakage, it is considered that a refrigerant leakage has occurred and the amount of refrigerant in the refrigerant circuit 20 has decreased.

[0053] The refrigeration cycle apparatus 200 of the second embodiment determines whether or not the time of the pump-down operation is shorter than the time threshold value tith, and determines that the refrigerant is leaking if the time of the pump-down operation is shorter than the time threshold value tith. According to the second embodiment, as in the first embodiment, even if the compressor 1 is stopped, it is possible to accurately detect the refrigerant leakage and to take early action against the refrigerant leakage.

[0054] Embodiment 3 In the first and second embodiments, after the compressor 1 is stopped and a state suitable for refrigerant leakage determination is generated, the determination of refrigerant leakage is performed using the high pressure HP as the determination parameter in the first embodiment, and the pump-down operation time as the determination parameter in the second embodiment. In the third embodiment, refrigerant leakage is determined based on the degree of subcooling SC. In the third embodiment, the same components as those described in the first and second embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0055] A configuration of a refrigeration cycle apparatus according to the present embodiment 3 will be described. Fig. 8 is a refrigerant circuit diagram showing a configuration example of a refrigeration cycle apparatus according to the embodiment 3. As shown in Fig. 8, a refrigeration cycle apparatus 200a has a heat source side unit 100a and a load side unit 110.

[0056] As shown in Fig. 8, a receiver 5 and a subcooling heat exchanger 6 are connected in this order to a refrigerant pipe 21 between a condenser 4 and a flow control valve 10. The receiver 5 temporarily retains the refrigerant flowing out from the condenser 4 and separates the gas-liquid two-phase refrigerant into liquid refrigerant and gas refrigerant. The receiver 5 also serves to recover the refrigerant during pump-down operation. The subcooling heat exchanger 6 puts the refrigerant flowing out from the receiver 5 into a subcooled state.

[0057] A refrigerant temperature sensor 7 that detects the temperature of the refrigerant flowing through the refrigerant pipe 21 is provided between the subcooling heat exchanger 6 and the flow rate regulating valve 10. The refrigerant temperature sensor 7 detects the temperature of the subcooled liquid refrigerant that flows out from the subcooling heat exchanger 6. The refrigerant temperature sensor 7 is connected to the controller 30 via a signal line (not shown).

[0058] Fig. 9 is a functional block diagram showing a configuration example of the controller shown in Fig. 8. The controller 30 of the third embodiment has a calculation means 36 in addition to the refrigeration cycle control means 31, the valve control means 32, the compressor control means 33, the determination means 34, and the timer 35 shown in Fig. 2.

[0059] The calculation means 36 calculates the degree of subcooling SC from the temperature difference between the saturated gas temperature calculated from the high pressure Hp and the temperature of the refrigerant detected by the refrigerant temperature sensor 7. The determination means 34 determines whether the degree of subcooling SC calculated by the calculation means 36 is smaller than a predetermined subcooling threshold SCth. When the refrigerant is leaking, the amount of refrigerant in the refrigerant circuit 20 decreases and there is no excess refrigerant in the receiver 5, so that the degree of subcooling SC may be smaller than in a normal state where there is no refrigerant leakage. Therefore, when the degree of subcooling SC is smaller than the subcooling threshold Scth, the determination means 34 determines that the refrigerant is leaking, and when the degree of subcooling SC is equal to or greater than the subcooling threshold Scth, it determines that the refrigerant is not leaking.

[0060] Next, the operation of the refrigeration cycle apparatus 200a of the third embodiment will be described with reference to Fig. 5. Among the processes of steps S101 to S109 shown in Fig. 5, the processes other than step S108 are similar to those of the first embodiment, and therefore detailed description thereof will be omitted.

[0061] In the third embodiment, in step S108, the calculation means 36 calculates the degree of subcooling SC from the temperature difference between the saturated gas temperature calculated from the high pressure Hp and the refrigerant temperature detected by the refrigerant temperature sensor 7. The determination means 34 determines whether the degree of subcooling SC calculated by the calculation means 36 is smaller than the subcooling threshold value SCth.

[0062] If the result of the determination in step S108 is that the degree of subcooling SC is smaller than the subcooling threshold SCth, the determination means 34 determines that refrigerant is leaking (step S109). This is because it is considered that the degree of subcooling SC is smaller than the subcooling threshold SCth in the normal case because a refrigerant leak occurs, the amount of refrigerant in the refrigerant circuit 20 decreases, and there is no excess refrigerant in the receiver 5.

[0063] The refrigeration cycle apparatus 200a of the third embodiment determines whether the degree of supercooling SC is smaller than the supercooling threshold SCth, and determines that the refrigerant is leaking if the degree of supercooling SC is smaller than the supercooling threshold SCth. According to the third embodiment, as in the first embodiment, even if the compressor 1 is stopped, it is possible to accurately detect the refrigerant leakage and to take early action against the refrigerant leakage.

[0064] Embodiment 4 In the first and second embodiments, after the compressor 1 is stopped and a state suitable for refrigerant leakage determination is generated, the refrigerant leakage determination is performed using the high pressure HP as the determination parameter in the first embodiment, and the pump-down operation time as the determination parameter in the second embodiment. In the third embodiment, after the compressor 1 is stopped and a state suitable for refrigerant leakage determination is generated, the refrigerant leakage determination is performed using the subcooling degree SC as the determination parameter. In the fourth embodiment, a refrigerant leakage is determined based on the temperature of the refrigerant discharged from the compressor 1. In the fourth embodiment, the same components as those described in the first to third embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0065] A configuration of a refrigeration cycle apparatus according to the present embodiment 4 will be described. Fig. 10 is a refrigerant circuit diagram showing a configuration example of a refrigeration cycle apparatus according to the embodiment 4. As shown in Fig. 10, a refrigeration cycle apparatus 200b has a heat source side unit 100b and a load side unit 110.

[0066] 10, a discharge temperature sensor 2 is provided in a refrigerant pipe 21 between a compressor 1 and a condenser 4. The discharge temperature sensor 2 is provided on the refrigerant discharge port side of the compressor 1, and detects a discharge temperature DT, which is the temperature of the refrigerant discharged from the compressor 1.

[0067] Fig. 11 is a functional block diagram showing a configuration example of the controller shown in Fig. 10. The determination means 34 of the fourth embodiment determines whether or not the discharge temperature DT detected by the discharge temperature sensor 2 is equal to or higher than a predetermined temperature threshold Teth. When refrigerant is leaking, the amount of refrigerant in the refrigerant circuit 20 is reduced, so the discharge temperature DT of the compressor 1 tends to rise. Therefore, when the discharge temperature DT is equal to or higher than the temperature threshold Teth, the determination means 34 determines that refrigerant is leaking. When the discharge temperature DT is less than the temperature threshold Teth, the determination means 34 determines that refrigerant is not leaking.

[0068] Next, the operation of the refrigeration cycle apparatus 200b according to the fourth embodiment will be described with reference to Fig. 5. Among the processes of steps S101 to S109 shown in Fig. 5, the processes except for step S108 are similar to those of the first embodiment, and therefore detailed description thereof will be omitted.

[0069] In the fourth embodiment, in step S108, the determination means 34 determines whether or not the discharge temperature DT is equal to or higher than the temperature threshold value Teth. If the result of the determination in step S108 is that the discharge temperature DT is equal to or higher than the temperature threshold value Teth, the determination means 34 determines that the refrigerant is leaking (step S109). This is because it is considered that the discharge temperature DT of the compressor 1 is rising due to the occurrence of refrigerant leakage and the reduction in the amount of refrigerant in the refrigerant circuit 20.

[0070] The refrigeration cycle apparatus 200b of the fourth embodiment determines whether the discharge temperature DT is equal to or higher than the temperature threshold value Teth, and determines that the refrigerant is leaking if the discharge temperature DT is equal to or higher than the temperature threshold value Teth. According to the fourth embodiment, as in the first embodiment, even if the compressor 1 is stopped, it is possible to accurately detect the refrigerant leakage and to take early action against the refrigerant leakage.

[0071] Embodiment 5. In the first to fourth embodiments, when the flow rate control valve 10 is opened while the compressor 1 is stopped before the compressor 1 performs the pump-down operation, the refrigerant on the high pressure side moves to the low pressure side. Therefore, the compressor 1 may perform an operation in which liquid refrigerant is sucked in immediately after starting the pump-down operation. In the fifth embodiment, the operating frequency of the compressor 1 is controlled to prevent the compressor 1 from sucking in the liquid refrigerant when performing the pump-down operation. In the fifth embodiment, the same components as those described in the first to fourth embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0072] A configuration of a refrigeration cycle apparatus according to the present embodiment 5 will be described. Fig. 12 is a refrigerant circuit diagram showing a configuration example of a refrigeration cycle apparatus according to the embodiment 5. As shown in Fig. 12, a refrigeration cycle apparatus 200c has a heat source side unit 100c and a load side unit 110.

[0073] 12, a suction temperature sensor 8 is provided in the refrigerant piping 21 between the compressor 1 and the evaporator 12. The suction temperature sensor 8 is provided on the refrigerant suction port side of the compressor 1, and detects a suction temperature ST, which is the temperature of the refrigerant sucked into the compressor 1.

[0074] Fig. 13 is a functional block diagram showing a configuration example of the controller shown in Fig. 12. The controller 30 of the fifth embodiment has a calculation means 36 in addition to the refrigeration cycle control means 31, the valve control means 32, the compressor control means 33, the determination means 34, and the timer 35 shown in Fig. 2.

[0075] The calculation means 36 calculates the degree of superheat (suction SH) from the temperature difference between the saturated gas temperature calculated from the low pressure LP and the suction temperature ST detected by the suction temperature sensor 8 during the pump-down operation of the compressor 1. The determination means 34 determines whether the degree of superheat calculated by the calculation means 36 is equal to or lower than a predetermined superheat threshold SHth. When the compressor 1 draws in liquid refrigerant, the degree of superheat of the refrigerant drawn by the compressor 1 becomes small. Therefore, when the degree of superheat calculated by the calculation means 36 is equal to or lower than the superheat threshold SHth, the determination means 34 determines that the compressor 1 is drawing in liquid refrigerant. When the determination means 34 determines that the degree of superheat is equal to or lower than the superheat threshold SHth, the compressor control means 33 reduces the operating frequency fc of the compressor 1 by a predetermined constant value of frequency Δf from the operating frequency when the pump-down operation is started. In the fifth embodiment, the minimum frequency of the operating frequency fc of the compressor 1 is set to fcmin.

[0076] An operation of the refrigeration cycle apparatus 200b of the fifth embodiment will be described. Fig. 14 is a flowchart showing the operation procedure of the refrigeration cycle apparatus according to the fifth embodiment. Fig. 14 shows an example of a control method for suppressing the intake of liquid refrigerant when the compressor 1 performs pump-down operation. During the pump-down operation in steps S105 to S106 shown in Fig. 5, the controller 30 controls the compressor 1 in accordance with the procedure shown in Fig. 14.

[0077] In step S201, the compressor control means 33 starts the compressor 1. In step S202, the calculation means 36 calculates the degree of superheat (suction SH) from the temperature difference between the saturated gas temperature calculated from the low pressure LP and the suction temperature ST detected by the suction temperature sensor 8. The determination means 34 determines whether the degree of superheat (suction SH) is equal to or lower than the superheat threshold SHth.

[0078] When the compressor 1 draws in liquid refrigerant, the degree of superheat of the refrigerant drawn in by the compressor 1 decreases. Therefore, in the determination process of step S202, when the determination means 34 determines that the degree of superheat (suction SH) is equal to or lower than the superheat threshold SHth, it determines that the compressor 1 is drawing in liquid refrigerant. In this case, the compressor control means 33 reduces the operating frequency fc of the compressor 1 by the frequency Δf (step S203).

[0079] After the process of step S203, the compressor control means 33 judges whether or not the operation frequency fc of the compressor 1 is equal to the minimum frequency fcmin (step S204). If the operation frequency fc of the compressor 1 is not equal to the minimum frequency fcmin, the controller 30 returns to step S202. The calculation means 36 calculates the degree of superheat again, and the judgment means 34 judges whether or not the degree of superheat is equal to or less than the superheat threshold value SHth. On the other hand, if the result of the judgment in step S204 is that the operation frequency fc of the compressor 1 is equal to the minimum frequency fcmin, the compressor control means 33 maintains the operation frequency fc at the minimum frequency fcmin during the pump-down operation (step S205).

[0080] In this way, when the degree of superheat is equal to or lower than the superheat threshold value SHth, the compressor control means 33 eventually reduces the operation frequency fc of the compressor 1 until it reaches the minimum frequency fcmin. Therefore, even if the compressor 1 is in a state of sucking in liquid refrigerant during pump-down operation, the operation frequency fc is reduced so as not to suck in the liquid refrigerant, and damage to the compressor 1 can be suppressed. Note that the refrigerant leakage determination process by the refrigeration cycle apparatus 200c of the fifth embodiment is the same as the procedure described with reference to FIG. 5, and therefore a detailed description thereof will be omitted. With the aim of suppressing the suction of liquid refrigerant into the compressor 1, the fifth embodiment can be applied to any of the first to fourth embodiments.

[0081] In the refrigeration cycle apparatus 200c of the present embodiment 5, the low pressure Lp is increased while the compressor 1 is stopped, and then the compressor 1 is made to perform pump-down operation, but the compressor 1 is controlled so as not to draw in liquid refrigerant based on the degree of superheat. According to the present embodiment 5, it is possible to accurately determine the leakage of refrigerant while protecting the compressor 1, similar to the embodiment 1.

[0082] Embodiment 6 In the fifth embodiment, the operating frequency fc of the compressor 1 is controlled based on the degree of superheat in order to prevent the compressor 1 from sucking in liquid refrigerant when performing pump-down operation. In the sixth embodiment, an accumulator is provided on the refrigerant suction port side of the compressor 1 in order to prevent the compressor 1 from sucking in liquid refrigerant. In the sixth embodiment, the same components as those described in the first to fifth embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0083] A configuration of a refrigeration cycle apparatus according to the present embodiment 6 will be described. Fig. 15 is a refrigerant circuit diagram showing a configuration example of a refrigeration cycle apparatus according to the embodiment 6. As shown in Fig. 15, a refrigeration cycle apparatus 200d has a heat source side unit 100d and a load side unit 110d.

[0084] 15, an accumulator 14 is provided between the evaporator 12 and the compressor 1. The accumulator 14 separates the refrigerant flowing in from the evaporator 12 into a liquid refrigerant and a gas refrigerant, and causes the gas refrigerant to flow out to the compressor 1.

[0085] In the refrigeration cycle apparatus 200c of the fifth embodiment, when the compressor 1 performs pump-down operation, the operating frequency fc is reduced to suppress the compressor 1 from sucking in liquid refrigerant and prevent damage to the compressor 1. However, because the operating frequency fc of the compressor 1 is lower than that in the case of normal pump-down operation, the time from the start to the end of the pump-down operation becomes longer than in the normal case, and the time until a refrigerant leak is detected also becomes longer.

[0086] In contrast, in the sixth embodiment, as shown in Fig. 15, an accumulator 14 is provided between the evaporator 12 and the compressor 1. By providing the accumulator 14 between the evaporator 12 and the compressor 1, it is possible to suppress the inflow of liquid refrigerant into the compressor 1. This suppresses a decrease in the degree of superheat (suction SH) calculated from the temperature difference between the saturated gas temperature calculated from the low pressure LP of the compressor 1 and the suction temperature ST detected by the suction temperature sensor 8. As a result, the compressor control means 33 is suppressed from reducing the operation frequency fc of the compressor 1, and it is possible to suppress the time from the start to the end of the pump-down operation becoming longer than in the normal case.

[0087] The refrigerant leakage determination process by the refrigeration cycle apparatus 200d of the sixth embodiment is similar to the procedure described with reference to Fig. 5, and therefore a detailed description thereof will be omitted. Although the sixth embodiment has been described based on the fifth embodiment, the sixth embodiment can be applied to any of the first to fourth embodiments and the embodiments described later, with the aim of suppressing the intake of liquid refrigerant into the compressor 1.

[0088] The refrigeration cycle apparatus 200d of the sixth embodiment increases the low pressure Lp while the compressor 1 is stopped, and then causes the compressor 1 to perform pump-down operation, but has an accumulator 14 that prevents the compressor 1 from drawing in liquid refrigerant. According to the fifth embodiment, it is possible to accurately determine refrigerant leakage, similar to the first embodiment, while preventing the pump-down operation time from becoming long and protecting the compressor 1.

[0089] Embodiment 7 In the seventh embodiment, a fan is provided in the load unit, and the rotation speed of the fan is controlled to prevent the compressor 1 from sucking in liquid refrigerant during pump-down operation. In the seventh embodiment, the same components as those described in the first to sixth embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0090] A configuration of a refrigeration cycle apparatus according to the seventh embodiment will be described. Fig. 16 is a refrigerant circuit diagram showing a configuration example of a refrigeration cycle apparatus according to the seventh embodiment. As shown in Fig. 16, a refrigeration cycle apparatus 200e has a heat source side unit 100e and a load side unit 110e.

[0091] 16, the load side unit 110e is provided with a fan 13 that supplies air to the evaporator 12. The fan 13 has a fan motor 41 and a propeller 42 connected to the fan motor 41 via a shaft. The fan motor 41 is connected to the controller 30 via a signal line (not shown).

[0092] Fig. 17 is a functional block diagram showing a configuration example of the controller shown in Fig. 16. The controller 30 of the seventh embodiment has a fan control means 37 in addition to the multiple means shown in Fig. 13. The fan control means 37 controls the number of rotations N of the fan 13. The number of rotations N is the number of rotations per unit time (for example, one minute).

[0093] The calculation means 36 calculates the degree of superheat (suction SH) from the temperature difference between the saturated gas temperature calculated from the low pressure LP and the suction temperature ST detected by the suction temperature sensor 8 during the pump-down operation of the compressor 1. The determination means 34 determines whether the degree of superheat calculated by the calculation means 36 is equal to or lower than a predetermined superheat threshold SHth. When the determination means 34 determines that the degree of superheat is equal to or lower than the superheat threshold SHth, the fan control means 37 increases the rotation speed N of the fan 13 by a predetermined constant value of rotation speed ΔN from the rotation speed at the start of the pump-down operation. In the seventh embodiment, the maximum rotation speed N of the fan 13 is set to Nmax.

[0094] 16, when the cooling method of the evaporator 12 provided in the load side unit 110e is an air-cooling type using a fan 13, the evaporation of the liquid refrigerant can be promoted by increasing the rotation speed of the fan 13 to increase the amount of air flowing to the evaporator 12. As a result, the inflow of the liquid refrigerant into the compressor 1 is suppressed, and the decrease in the degree of superheat can be suppressed.

[0095] The operation of the refrigeration cycle apparatus 200e of the seventh embodiment will be described with reference to Fig. 14. Among the processes of steps S201 to S205 shown in Fig. 14, the processes of steps S201 to S202 are similar to those of the fifth embodiment, and therefore detailed description thereof will be omitted.

[0096] In step S202, when the determination means 34 determines that the degree of superheat (intake SH) is equal to or lower than the superheat threshold SHth, in step S203, the fan control means 37 increases the rotation speed N of the fan 13 by the rotation speed ΔN. In step S204, the fan control means 37 determines whether the rotation speed N of the fan 13 is the same as the maximum rotation speed Nmax. If the rotation speed N of the fan 13 is the same as the maximum rotation speed Nmax, in step S205, the fan control means 37 maintains the rotation speed N at the maximum rotation speed Nmax during the pump-down operation.

[0097] The refrigerant leakage determination process by the refrigeration cycle apparatus 200e of the seventh embodiment is similar to the procedure described with reference to Fig. 5, and therefore a detailed description thereof will be omitted. Although the sixth embodiment has been described based on the fifth embodiment, it can be applied to any of the first to fourth embodiments with the aim of suppressing the intake of liquid refrigerant into the compressor 1.

[0098] In the refrigeration cycle apparatus 200e of the seventh embodiment, the low pressure Lp is increased while the compressor 1 is stopped, and then the compressor 1 is made to perform pump-down operation, but the fan 13 provided in the load side unit 110e is controlled so that the compressor 1 does not suck in liquid refrigerant. According to the seventh embodiment, it is possible to prevent the pump-down operation time from becoming long and to protect the compressor 1, while accurately determining whether or not there is a refrigerant leak, similar to the first embodiment.

[0099] Embodiment 8 The refrigeration cycle device of the present embodiment 8 has a plurality of load side units. In the present embodiment 8, the same components as those described in the embodiments 1 to 7 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0100] The configuration of the refrigeration cycle apparatus of the eighth embodiment will be described. Fig. 18 is a refrigerant circuit diagram showing one configuration example of the refrigeration cycle apparatus according to the eighth embodiment. As shown in Fig. 18, the refrigeration cycle apparatus 200f has a heat source side unit 100 and a plurality of load side units 110-1 and 110-2. The plurality of load side units 110-1 and 110-2 are connected in parallel to the heat source side unit 100. Fig. 18 shows a case where there are two load side units 110 shown in Fig. 1, but the number of load side units 110 is not limited to two and may be three or more.

[0101] The load side unit 110-1 has a flow control valve 10a, a pressure reducing device 11a, an evaporator 12a, a room temperature sensor 23a, and an alarm device 50. The load side unit 110-2 has a flow control valve 10b, a pressure reducing device 11b, an evaporator 12b, and a room temperature sensor 23b. The flow control valves 10a and 10b have the same configuration as the flow control valve 10, the pressure reducing devices 11a and 11b have the same configuration as the pressure reducing device 11, and the evaporators 12a and 12b have the same configuration as the evaporator 12, so detailed explanations of these will be omitted. The room temperature sensors 23a and 23b have the same configuration as the room temperature sensor 23, so detailed explanations of them will be omitted. The alarm device 50 may be provided in the load side unit 110-2 instead of the load side unit 110-1, or may be provided in both the load side units 110-1 and 110-2.

[0102] As shown in Fig. 18, the refrigerant pipe 21 extending from the condenser 4 branches into refrigerant pipes 21a and 21b, and the flow control valve 10a, pressure reducing device 11a, and evaporator 12a of the load side unit 110-1 are connected in sequence via the refrigerant pipe 21a. The flow control valve 10b, pressure reducing device 11b, and evaporator 12b of the load side unit 110-2 are connected in sequence via the refrigerant pipe 21b. The refrigerant pipe 21a extending from the load side unit 110-1 and the refrigerant pipe 21b extending from the load side unit 110-2 join together and are connected to the refrigerant suction port of the compressor 1.

[0103] Fig. 19 is a functional block diagram showing one configuration example of the controller shown in Fig. 18. Valve control means 32 controls pressure reducing devices 11a and 11b and flow rate regulating valves 10a and 10b.

[0104] Next, the operation of the refrigeration cycle apparatus 200f according to the eighth embodiment will be described with reference to Fig. 5. In the fifth embodiment, among steps S101 to S109 shown in Fig. 5, except for step S102, the process is the same as that described with reference to the first and fifth embodiments, and therefore detailed description thereof will be omitted.

[0105] In step S102, the valve control means 32 switches all of the flow control valves 10a provided in the load side unit 110-1 and the flow control valves 10b provided in the load side unit 110-2, which are in a closed state, to an open state, thereby allowing the refrigerant to flow through the evaporator 12 of the load side unit 110, through which the refrigerant had not flowed before.

[0106] When the flow rate regulating valve 10 opens and the liquid refrigerant on the high pressure side moves to the low pressure side, the liquid refrigerant can be evaporated by the evaporators 12 of all the load side units 110, rather than evaporating the liquid refrigerant only by the evaporators 12 of the load side units 110 that were operating before the compressor 1 was stopped. Therefore, the inflow of liquid refrigerant into the compressor 1 can be suppressed, and a decrease in the degree of superheat (suction SH) can be suppressed.

[0107] Although the eighth embodiment has been described based on the fifth embodiment, it can be applied to any of the first to fourth embodiments in order to suppress the intake of liquid refrigerant into the compressor 1.

[0108] In the refrigeration cycle apparatus 200f of the eighth embodiment, after increasing the low pressure Lp while the compressor 1 is stopped, the compressor 1 is made to perform pump-down operation, but all of the flow control valves 10 provided in the multiple load side units 110 are opened. According to the eighth embodiment, it is possible to prevent the pump-down operation time from becoming long and to protect the compressor 1, while accurately determining the leakage of the refrigerant, similarly to the first embodiment.

[0109] In the above-mentioned first to eighth embodiments, the load-side heat exchanger provided in the load-side unit 110 functions as the evaporator 12. However, the load-side heat exchanger may function as the condenser 4. A four-way valve for switching the refrigerant flow direction in the refrigerant circuit 20 may be provided in the heat source unit 100, so that the operation mode of the load-side unit 110 can be switched between cooling operation and heating operation. In this case, the load-side heat exchanger functions as the evaporator 12 or the condenser 4 depending on the operation mode of the load-side unit 110.

[0110] The refrigeration cycle devices 200 to 200f described with reference to the first to eighth embodiments can be applied to refrigerant leakage determination when the compressor 1 is stopped for a long period of time. Two or more of the first to eighth embodiments described above may be combined so as not to cause any mutual contradiction. [Explanation of symbols]

[0111] 1 compressor, 2 discharge temperature sensor, 3 high pressure sensor, 4 condenser, 5 receiver, 6 subcooling heat exchanger, 7 refrigerant temperature sensor, 8 suction temperature sensor, 9 low pressure sensor, 10, 10a, 10b flow control valve, 11, 11a, 11b pressure reducing device, 12, 12a, 12b evaporator, 13 fan, 14 accumulator, 20 refrigerant circuit, 21, 21a, 21b refrigerant piping, 23, 23a, 23b room temperature sensor, 25 signal line, 30 controller, 31 refrigeration cycle control means, 32 valve control means, 33 compressor control means, 34 determination means, 35 timer, 36 calculation means, 37 fan control means, 41 fan motor, 42 propeller, 50 alarm device, 90 processing circuit, 91 processor, 92 memory, 93 Bus, 100, 100a to 100e heat source side units, 110, 110-1, 110-2, 110d, 110e load side units, 200, 200a to 200f refrigeration cycle devices.

Claims

1. a refrigerant circuit in which a compressor, a condenser, and an evaporator are connected by a refrigerant pipe, and a refrigerant circulates through the refrigerant pipe; a low pressure sensor provided between the compressor and the evaporator for detecting a low pressure, which is a pressure of the refrigerant flowing through the refrigerant pipe; a flow rate control valve provided between the condenser and the evaporator; a controller for controlling the compressor and the flow rate control valve, The controller: a valve control means for switching the flow control valve from the open state to a closed state after keeping the flow control valve in an open state until the elapsed time from when the compressor was stopped is equal to or longer than a reference time for ensuring a certain operating time of the compressor in a pump-down operation; a compressor control means for causing the compressor to execute the pump-down operation in which the refrigerant in the refrigerant circuit is recovered in the condenser when the flow rate control valve is switched from the open state to the closed state; a determination unit that determines whether or not the refrigerant is leaking based on a state of a device constituting the refrigerant circuit or the state of the refrigerant when the compressor finishes the pump-down operation; A refrigeration cycle device having the above structure.

2. a refrigerant circuit in which a compressor, a condenser, and an evaporator are connected by a refrigerant pipe, and a refrigerant circulates through the refrigerant pipe; a low pressure sensor provided between the compressor and the evaporator for detecting a low pressure, which is a pressure of the refrigerant flowing through the refrigerant pipe; a flow rate control valve provided between the condenser and the evaporator; a controller for controlling the compressor and the flow rate control valve, The controller: a valve control means for opening the flow control valve until the low pressure becomes equal to or higher than a reference value for ensuring a certain period of operation of the compressor in a pump-down operation while the compressor is stopped, and then switching the flow control valve from the open state to a closed state; a compressor control means for causing the compressor to execute the pump-down operation in which the refrigerant in the refrigerant circuit is recovered in the condenser when the flow rate control valve is switched from the open state to the closed state; a determination unit that determines whether or not the refrigerant is leaking based on a state of a device constituting the refrigerant circuit or the state of the refrigerant when the compressor finishes the pump-down operation; A refrigeration cycle device having the above structure.

3. The determination means is If the time of the pump-down operation is shorter than a predetermined time threshold, it is determined that the refrigerant is leaking. The refrigeration cycle device according to claim 1 or 2.

4. a high-pressure sensor provided between the compressor and the condenser for detecting a high-pressure pressure of the refrigerant flowing through the refrigerant pipe; The determination means is If the high pressure is equal to or lower than a predetermined pressure threshold, it is determined that the refrigerant is leaking. The refrigeration cycle device according to claim 1 or 2.

5. a receiver provided between the condenser and the flow rate control valve; a subcooling heat exchanger provided between the receiver and the flow rate control valve; a high-pressure sensor provided between the compressor and the condenser and configured to detect a high-pressure pressure of the refrigerant flowing through the refrigerant pipe; a refrigerant temperature sensor provided between the subcooling heat exchanger and the flow rate regulating valve for detecting a temperature of the refrigerant flowing out from the subcooling heat exchanger, The controller: a calculation means for calculating a degree of subcooling from a temperature difference between a saturated gas temperature calculated from the high pressure and a temperature of the refrigerant detected by the refrigerant temperature sensor; The determination means is When the degree of subcooling calculated by the calculation means is smaller than a predetermined subcooling threshold value, it is determined that the refrigerant is leaking. The refrigeration cycle device according to claim 1 or 2.

6. a discharge temperature sensor provided between the compressor and the condenser for detecting a discharge temperature of the refrigerant discharged from the compressor; The determination means is When the discharge temperature detected by the discharge temperature sensor is equal to or higher than a predetermined temperature threshold, it is determined that the refrigerant is leaking. The refrigeration cycle device according to claim 1 or 2.

7. A refrigerant circuit in which a compressor, a condenser, and an evaporator are connected by a refrigerant piping, and a refrigerant circulates through the refrigerant piping; a low pressure sensor provided between the compressor and the evaporator for detecting a low pressure, which is a pressure of the refrigerant flowing through the refrigerant pipe; an intake temperature sensor provided between the compressor and the evaporator for detecting an intake temperature, which is a temperature of a refrigerant sucked into the compressor; a flow rate control valve provided between the condenser and the evaporator; a controller for controlling the compressor and the flow rate control valve, The controller: a valve control means for switching the flow rate control valve from the open state to a closed state after keeping the flow rate control valve in an open state until the elapsed time from when the compressor was stopped becomes equal to or longer than a predetermined reference time; a compressor control means for causing the compressor to perform a pump-down operation in which the refrigerant in the refrigerant circuit is recovered in the condenser when the flow rate control valve is switched from the open state to the closed state; a determination unit that determines whether or not the refrigerant is leaking based on a state of a device constituting the refrigerant circuit or the state of the refrigerant when the compressor finishes the pump-down operation; a calculation means for calculating a degree of superheat from a temperature difference between a saturated gas temperature calculated from the low pressure and the intake temperature detected by the intake temperature sensor during the pump-down operation, The determination means is Determining whether the degree of superheat calculated by the calculation means is equal to or less than a predetermined superheat threshold value; The compressor control means When the determination means determines that the degree of superheat is equal to or lower than the superheat threshold value, an operation frequency of the compressor is made lower than an operation frequency at the start of the pump-down operation.

8. A refrigerant circuit in which a compressor, a condenser, and an evaporator are connected by a refrigerant piping, and a refrigerant circulates through the refrigerant piping; a low pressure sensor provided between the compressor and the evaporator for detecting a low pressure, which is a pressure of the refrigerant flowing through the refrigerant pipe; an intake temperature sensor provided between the compressor and the evaporator for detecting an intake temperature, which is a temperature of a refrigerant sucked into the compressor; a flow rate control valve provided between the condenser and the evaporator; a controller for controlling the compressor and the flow rate control valve, The controller: a valve control means for opening the flow control valve until the low pressure reaches a predetermined reference value or more while the compressor is stopped, and then switching the flow control valve from the open state to a closed state; a compressor control means for causing the compressor to perform a pump-down operation in which the refrigerant in the refrigerant circuit is recovered in the condenser when the flow rate control valve is switched from the open state to the closed state; a determination unit that determines whether or not the refrigerant is leaking based on a state of a device constituting the refrigerant circuit or the state of the refrigerant when the compressor finishes the pump-down operation; a calculation means for calculating a degree of superheat from a temperature difference between a saturated gas temperature calculated from the low pressure and the intake temperature detected by the intake temperature sensor during the pump-down operation, The determination means is Determining whether the degree of superheat calculated by the calculation means is equal to or less than a predetermined superheat threshold value; The compressor control means When the determination means determines that the degree of superheat is equal to or lower than the superheat threshold value, an operation frequency of the compressor is made lower than an operation frequency at the start of the pump-down operation.

9. A refrigerant circuit in which a compressor, a condenser, and an evaporator are connected by a refrigerant piping, and a refrigerant circulates through the refrigerant piping; a low pressure sensor provided between the compressor and the evaporator for detecting a low pressure, which is a pressure of the refrigerant flowing through the refrigerant pipe; A fan for supplying air to the evaporator; an intake temperature sensor provided between the compressor and the evaporator for detecting an intake temperature, which is a temperature of a refrigerant sucked into the compressor; a flow rate control valve provided between the condenser and the evaporator; a controller for controlling the compressor and the flow rate control valve, The controller: a valve control means for switching the flow rate control valve from the open state to a closed state after keeping the flow rate control valve in an open state until the elapsed time from when the compressor was stopped becomes equal to or longer than a predetermined reference time; a compressor control means for causing the compressor to perform a pump-down operation in which the refrigerant in the refrigerant circuit is recovered in the condenser when the flow rate control valve is switched from the open state to the closed state; a determination unit that determines whether or not the refrigerant is leaking based on a state of a device constituting the refrigerant circuit or the state of the refrigerant when the compressor finishes the pump-down operation; a calculation means for calculating a degree of superheat from a temperature difference between a saturated gas temperature calculated from the low pressure and the suction temperature detected by the suction temperature sensor during the pump-down operation; A fan control means for controlling the rotation speed of the fan, The determination means is Determining whether the degree of superheat calculated by the calculation means is equal to or less than a predetermined superheat threshold value; The fan control means When the determining means determines that the degree of superheat is equal to or lower than the superheat threshold value, the rotation speed of the fan is increased above the rotation speed at the start of the pump-down operation.

10. A refrigerant circuit in which a compressor, a condenser, and an evaporator are connected by a refrigerant pipe, and a refrigerant circulates through the refrigerant pipe; a low pressure sensor provided between the compressor and the evaporator for detecting a low pressure, which is a pressure of the refrigerant flowing through the refrigerant pipe; A fan for supplying air to the evaporator; an intake temperature sensor provided between the compressor and the evaporator for detecting an intake temperature, which is a temperature of a refrigerant sucked into the compressor; a flow rate control valve provided between the condenser and the evaporator; a controller for controlling the compressor and the flow rate control valve, The controller: a valve control means for opening the flow control valve until the low pressure reaches a predetermined reference value or more while the compressor is stopped, and then switching the flow control valve from the open state to a closed state; a compressor control means for causing the compressor to perform a pump-down operation in which the refrigerant in the refrigerant circuit is recovered in the condenser when the flow rate control valve is switched from the open state to the closed state; a determination unit that determines whether or not the refrigerant is leaking based on a state of a device constituting the refrigerant circuit or the state of the refrigerant when the compressor finishes the pump-down operation; a calculation means for calculating a degree of superheat from a temperature difference between a saturated gas temperature calculated from the low pressure and the suction temperature detected by the suction temperature sensor during the pump-down operation; A fan control means for controlling the rotation speed of the fan, The determination means is Determining whether the degree of superheat calculated by the calculation means is equal to or less than a predetermined superheat threshold value; The fan control means When the determining means determines that the degree of superheat is equal to or lower than the superheat threshold value, the rotation speed of the fan is increased above the rotation speed at the start of the pump-down operation.

11. The cooling system further includes an accumulator disposed between the evaporator and the compressor. The refrigeration cycle device according to any one of claims 1 to 10.

12. The refrigerant circuit includes a plurality of load-side units each including the condenser or the evaporator and the flow rate control valve, The valve control means when switching the flow rate control valves from the open state to the closed state, all of the flow rate control valves provided in each of the plurality of load side units that are in the closed state are switched to the open state. The refrigeration cycle device according to any one of claims 1 to 6.

13. The flow rate regulating valve is a pressure reducing device that reduces the pressure of the refrigerant to expand it. The refrigeration cycle device according to any one of claims 1 to 12.

14. a pressure reducing device provided between the condenser and the evaporator in the refrigerant circuit, The flow rate control valve is provided between the condenser and the pressure reducing device. The refrigeration cycle device according to any one of claims 1 to 12.

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