Refrigeration cycle equipment

Abstract

To suppress heat loss.SOLUTION: A refrigeration cycle device (1) includes a refrigerant main circuit (10), and a control unit (6). A compressor (21), a heat source heat exchanger (24), a decompression device (25), and a utilization heat exchanger (31) are connected in order in the refrigerant main circuit. The control unit (6) executes a pause mode for temporarily stopping the compressor (22) when a first condition related to temperature or humidity of a space as a cooling or heating target is satisfied. In the pause mode, the control unit (6) maintains the decompression device (25) in a first state in which a decompression degree is high.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This relates to a refrigeration cycle device. [Background technology]

[0002] As disclosed in Patent Document 1 (JP 2018-128158 A), there is an air conditioner that performs air conditioning operation (cooling operation or heating operation) so that the indoor temperature reaches a target temperature. In such air conditioning operation, when the indoor temperature reaches the target temperature and air conditioning operation is no longer necessary, a thermo-off operation is performed, which stops the compressor and suspends air conditioning operation. Furthermore, if the indoor temperature deviates from the target indoor temperature after thermo-off and air conditioning operation is required, a thermo-on operation is performed, which restarts the compressor and resumes air conditioning operation. Summary of the Invention [Problem to be solved by the invention]

[0003] Generally, immediately after the thermostat is turned off in an air conditioner such as that described in Patent Document 1, the expansion valve is fully opened to perform pressure equalization control, which equalizes the pressure in the circuits between the utilization units and the heat source unit. However, performing pressure equalization control increases the heat loss of the refrigerant during the thermostat-off state. [Means for solving the problem]

[0004] A refrigeration cycle apparatus according to a first aspect includes a main refrigerant circuit and a control unit. The main refrigerant circuit has a compressor, a heat source heat exchanger, a pressure reduction device, and a utilization heat exchanger connected in this order. The control unit executes a pause mode in which the compressor is temporarily stopped when a first condition related to the temperature or humidity of a space to be cooled or heated is satisfied. In the pause mode, the control unit maintains the pressure reduction device in a first state in which the degree of pressure reduction is high.

[0005] According to the refrigeration cycle apparatus of the first aspect, in the pause mode in which the compressor is temporarily stopped, the pressure reducing device maintains a high degree of pressure reduction. This makes it possible to suppress the movement of refrigerant in the main refrigerant circuit during the pause mode, thereby suppressing heat loss of the refrigerant in the main refrigerant circuit.

[0006] A refrigeration cycle apparatus according to a second aspect is the refrigeration cycle apparatus of the first aspect, in which the pressure reducing device is a valve whose opening is variable, and the first state of the pressure reducing device is a state in which the opening of the valve is 10% or less of the maximum opening of the valve.

[0007] In the refrigeration cycle apparatus according to the second aspect, in the pause mode, the valve opening is maintained in the first state in which the degree of pressure reduction is very high, that is, 10% or less. This further suppresses the movement of the refrigerant in the main refrigerant circuit during the pause mode, thereby further suppressing heat loss of the refrigerant.

[0008] A refrigeration cycle apparatus according to a third aspect is the refrigeration cycle apparatus of the first aspect, wherein the pressure reducing device is a valve whose opening is variable, and the first state of the pressure reducing device is a state in which the opening of the valve is smaller than the opening of the valve immediately before execution of the pause mode.

[0009] In the refrigeration cycle apparatus according to the third aspect, the opening of the valve is reduced when the refrigerant is in the pause mode, thereby easily realizing a refrigeration cycle apparatus that can suppress the movement of the refrigerant in the main refrigerant circuit during the pause mode, thereby suppressing heat loss of the refrigerant.

[0010] A refrigeration cycle apparatus according to a fourth aspect is the refrigeration cycle apparatus according to the first aspect to the third aspect, wherein the control unit maintains the pressure reducing device in a first state in which the degree of pressure reduction is high for at least two minutes or more in the pause mode.

[0011] In the refrigeration cycle apparatus according to the fourth aspect, the first state is maintained for two minutes or more in the pause mode, thereby further suppressing the movement of the refrigerant in the main refrigerant circuit during the pause mode, thereby further suppressing heat loss of the refrigerant.

[0012] A refrigeration cycle device according to a fifth aspect is a refrigeration cycle device according to any one of the first to fourth aspects, wherein the main refrigerant circuit is provided with a backflow prevention device in the piping on the refrigerant discharge side of the compressor to prevent the refrigerant from flowing back into the compressor.

[0013] In the refrigeration cycle apparatus according to the fifth aspect, the backflow prevention device can prevent the refrigerant from flowing back into the compressor from the discharge side during the pause mode, thereby further reducing heat loss of the refrigerant.

[0014] A refrigeration cycle apparatus according to a sixth aspect is the refrigeration cycle apparatus according to the first to fifth aspects, wherein the main refrigerant circuit is divided into a high-pressure flow path upstream of the pressure reducing device and a low-pressure flow path downstream of the pressure reducing device. The refrigeration cycle apparatus further includes a differential pressure detection device that detects the difference in pressure between the refrigerant flowing through the high-pressure flow path and the refrigerant flowing through the low-pressure flow path.

[0015] In the refrigeration cycle apparatus according to the sixth aspect, the differential pressure detection device can confirm the differential pressure between the pressure of the refrigerant flowing through the high-pressure passage and the pressure of the refrigerant flowing through the low-pressure passage, and therefore the compressor can be restarted after confirming the differential pressure.

[0016] A refrigeration cycle apparatus according to a seventh aspect is the refrigeration cycle apparatus according to the first to sixth aspects, wherein the main refrigerant circuit is divided into a high-pressure flow path upstream of the pressure reducing device and a low-pressure flow path downstream of the pressure reducing device. The refrigeration cycle apparatus further includes a bypass pipe and a relief mechanism. The bypass pipe connects the high-pressure flow path and the low-pressure flow path. The relief mechanism relieves pressure on the high-pressure flow path side of the bypass pipe to the low-pressure flow path side.

[0017] In the refrigeration cycle apparatus according to the seventh aspect, the pressure on the high-pressure passage side can be released to the low-pressure passage side by the release mechanism immediately before restarting the compressor, thereby making it possible to easily restart the compressor.

[0018] A refrigeration cycle apparatus according to an eighth aspect is the refrigeration cycle apparatus according to any one of the first to seventh aspects, in which the control unit transitions from the pause mode to a restart mode for resuming normal operation when a second condition related to temperature or humidity is satisfied. In the restart mode, the control unit restarts the compressor at a predetermined low capacity and gradually reduces the degree of pressure reduction of the pressure reducing device.

[0019] In the refrigeration cycle apparatus according to the eighth aspect, the compressor is restarted at a low capacity in the restart mode, so that the load on the compressor can be reduced.

[0020] A refrigeration cycle apparatus according to a ninth aspect is the refrigeration cycle apparatus according to any one of the first to seventh aspects, in which the control unit transitions from the pause mode to a restart mode for resuming normal operation when a second condition related to temperature or humidity is satisfied. In the restart mode, first, the degree of pressure reduction of the pressure reduction device is reduced, and then the compressor is restarted.

[0021] In the refrigeration cycle apparatus according to the ninth aspect, in the restart mode, the degree of pressure reduction of the pressure reducing device is reduced, thereby reducing the pressure difference between the pressure of the refrigerant flowing through the high-pressure passage and the pressure of the refrigerant flowing through the low-pressure passage. In this way, the pressure difference can be reduced before the compressor is restarted, thereby reducing the burden on the compressor.

[0022] A refrigeration cycle apparatus according to a tenth aspect is the refrigeration cycle apparatus according to the ninth aspect, further including a heat source fan and a utilization fan. The heat source fan passes air as a heat source through the heat source heat exchanger. The utilization fan passes air in space through the utilization heat exchanger. In the restart mode, the control unit operates the heat source fan, the utilization fan, or both the heat source fan and the utilization fan before restarting the compressor.

[0023] In the refrigeration cycle apparatus according to the tenth aspect, by operating the heat source fan, the utilization fan, or both the heat source fan and the utilization fan, heat exchange of the refrigerant is promoted in the heat source unit, the utilization unit, or both the heat source unit and the utilization unit. This makes it possible to further reduce the differential pressure before restarting the compressor, thereby further reducing the burden on the compressor. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic configuration diagram of a refrigeration cycle device according to an embodiment of the present disclosure. [Figure 2] 3 is a diagram showing the operation (flow of refrigerant) during cooling operation of the refrigeration cycle device according to the embodiment of the present disclosure. FIG. [Figure 3] 3 is a diagram showing the operation (flow of refrigerant) during heating operation of the refrigeration cycle device according to the embodiment of the present disclosure. FIG. [Figure 4] FIG. 2 is a control block diagram of a refrigeration cycle device according to an embodiment of the present disclosure. [Figure 5] 4 is a flowchart illustrating a control method for a refrigeration cycle device according to an embodiment of the present disclosure. [Figure 6] 10 is a flowchart illustrating a control method for a refrigeration cycle device according to a modified example of the present disclosure. [Figure 7] FIG. 10 is a schematic configuration diagram of a refrigeration cycle device according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0025] (1) Refrigeration cycle equipment configuration As shown in FIG. 1 , a refrigeration cycle apparatus 1 according to one embodiment of the present disclosure is an apparatus for air-conditioning the interior of a building or the like using a vapor compression refrigeration cycle. The refrigeration cycle apparatus 1 mainly includes a heat source unit 2, a utilization unit 3, and a communication pipe 4 connecting the heat source unit 2 and the utilization unit 3. A vapor compression refrigerant main circuit 10 of the refrigeration cycle apparatus 1 is configured by connecting the heat source unit 2 and the utilization unit 3 via the communication pipe 4. The refrigerant main circuit 10 includes a compressor 21, a heat source heat exchanger 24, a pressure reducing device 25, and a utilization heat exchanger 31, connected in this order. As shown in FIGS. 2 and 3 , the refrigerant main circuit 10 is divided into a high-pressure flow path 11 upstream of the pressure reducing device 25 in the refrigerant flow direction and a low-pressure flow path 12 downstream of the pressure reducing device 25. Note that in FIGS. 2 and 3 , the location of the high-pressure refrigerant in the refrigeration cycle is indicated by diagonal lines, and the location of the low-pressure refrigerant in the refrigeration cycle is indicated by dots.

[0026] (1-1) Heat source unit The heat source unit 2 shown in Figures 1 to 3 is installed outdoors (on the roof of a building, near the exterior wall of a building, etc.). As described above, the heat source unit 2 is connected to the utilization units 3 via the connecting pipes 4, and constitutes part of the main refrigerant circuit 10. The heat source unit 2 mainly has a compressor 21, a backflow prevention device 22, a four-way switching valve 23, a heat source heat exchanger 24, a pressure reducing device 25, and a heat source fan 26.

[0027] The compressor 21 is a mechanism that compresses a low-pressure refrigerant in the refrigeration cycle to a high pressure. Here, a compressor of a sealed structure in which a rotary, scroll, or other positive displacement compression element (not shown) is rotationally driven by a compressor motor is used as the compressor 21. In addition, the rotation speed (frequency) of the compressor motor can be controlled by an inverter or the like, thereby controlling the capacity of the compressor 21.

[0028] The backflow prevention device 22 is provided in the piping on the refrigerant discharge side of the compressor 21 in the main refrigerant circuit 10. The backflow prevention device 22 prevents the refrigerant from flowing back into the compressor 21. In other words, the backflow prevention device 22 only allows the refrigerant to flow from the compressor 21 toward the four-way switching valve 23. The backflow prevention device 22 is a check valve, a solenoid valve, or the like, and is a check valve in this example.

[0029] The four-way switching valve 23 is a valve for switching the direction of refrigerant flow when switching between cooling operation or dehumidification operation and heating operation. During cooling operation or dehumidification operation, the four-way switching valve 23 connects the discharge side of the compressor 21 to the gas side of the heat source heat exchanger 24, and also connects the gas side of a utilization heat exchanger 31 (described later) to the suction side of the compressor 21 via the gas side connection pipe 4 (see the solid lines of the four-way switching valve 23 in FIG. 1). During heating operation, the four-way switching valve 23 connects the discharge side of the compressor 21 to the gas side of the utilization heat exchanger 31 via the gas side connection pipe 4, and also connects the gas side of the heat source heat exchanger 24 to the suction side of the compressor 21 (see the dashed lines of the four-way switching valve 23 in FIG. 1).

[0030] The heat source heat exchanger 24 is a heat exchanger that functions as a refrigerant radiator during cooling or dehumidifying operation and as a refrigerant evaporator during heating operation. The liquid side of the heat source heat exchanger 24 is connected to the pressure reducing device 25, and the gas side is connected to the four-way switching valve 23.

[0031] The pressure reducing device 25 is an expansion mechanism that can reduce the pressure of the high-pressure liquid refrigerant that has dissipated heat in the heat source heat exchanger 24 before sending it to the utilization heat exchanger 31 during cooling operation or dehumidification operation, and can reduce the pressure of the high-pressure liquid refrigerant that has dissipated heat in the utilization heat exchanger 31 before sending it to the heat source heat exchanger 24 during heating operation. Here, the pressure reducing device 25 is a valve whose opening degree can be changed. In this embodiment, an electric expansion valve whose opening degree can be controlled is used as the pressure reducing device 25.

[0032] The heat source fan 26 passes air as a heat source through the heat source heat exchanger 24. Specifically, the heat source fan 26 draws outdoor air into the heat source unit 2, supplies the outdoor air to the heat source heat exchanger 24, and then expels the air to the outside of the heat source unit 2. Therefore, the heat source heat exchanger 24 uses the outdoor air as a cooling or heating source to dissipate heat or evaporate the refrigerant. The heat source fan 26 is rotationally driven by a heat source fan motor.

[0033] The heat source unit 2 is also provided with a bypass pipe 13 that connects the high-pressure flow path 11 and the low-pressure flow path 12 of the main refrigerant circuit 10. In this embodiment, the bypass pipe 13 connects the discharge pipe of the compressor 21 as the high-pressure flow path 11 and the suction pipe of the compressor 21 as the low-pressure flow path 12. The discharge pipe and suction pipe of the compressor 21 do not change the high-pressure flow path 11 and the low-pressure flow path 12 during cooling operation and heating operation.

[0034] The bypass pipe 13 is provided with a differential pressure detection device 14 and a pressure relief mechanism 15. Here, the bypass pipe 13 branches into two, with the differential pressure detection device 14 provided in one branch pipe and the pressure relief mechanism 15 provided in the other branch pipe.

[0035] The differential pressure detection device 14 detects the difference between the pressure of the refrigerant flowing through the high-pressure flow path 11 and the pressure of the refrigerant flowing through the low-pressure flow path 12. Here, the differential pressure detection device 14 is a differential pressure sensor.

[0036] The relief mechanism 15 relieves the pressure on the high-pressure flow path 11 side to the low-pressure flow path 12 side in the bypass pipe 13. Here, the relief mechanism 15 is a pressure relief valve.

[0037] Various sensors are also provided in the heat source unit 2. Specifically, as shown in Fig. 4, the heat source unit 2 is provided with a suction pressure sensor 28a that detects the suction pressure of the compressor 21, a suction temperature sensor 28b that detects the suction temperature of the compressor 21, a discharge pressure sensor 29a that detects the discharge pressure of the compressor 21, and a discharge temperature sensor 29b that detects the discharge temperature of the compressor 21.

[0038] (1-2) Connecting piping The connecting pipes 4 are refrigerant pipes that are installed on-site when the refrigeration cycle apparatus 1 is installed in an installation location such as a building. One end of the liquid-side connecting pipe 4 (the lower connecting pipe 4 in FIG. 1) is connected to the pressure reducing device 25 side of the heat source unit 2, and the other end of the liquid-side connecting pipe 4 is connected to the liquid side of the utilization heat exchanger 31 of the utilization unit 3. One end of the gas-side connecting pipe 4 (the upper connecting pipe 4 in FIG. 1) is connected to the four-way switching valve 23 side of the heat source unit 2, and the other end of the gas-side connecting pipe 4 is connected to the gas side of the utilization heat exchanger 31 of the utilization unit 3.

[0039] (1-3) Usage unit The utilization unit 3 is installed indoors (inside the building). As described above, the utilization unit 3 is connected to the heat source unit 2 via the connecting pipe 4, and constitutes part of the refrigerant main circuit 10. The utilization unit 3 mainly has a utilization heat exchanger 31 and a utilization fan 32.

[0040] The utilization heat exchanger 31 exchanges heat between the indoor air and the refrigerant to generate conditioned air. The utilization heat exchanger 31 is a heat exchanger that functions as a refrigerant evaporator during cooling or dehumidifying operation, and as a refrigerant radiator during heating operation. The utilization heat exchanger 31 has its liquid side connected to the liquid-side connecting pipe 4 and its gas side connected to the gas-side connecting pipe 4.

[0041] The utilization fan 32 passes air through the space (indoor space) to be cooled or heated. Specifically, the utilization fan 32 draws indoor air into the utilization heat exchanger 31, and then blows conditioned air from the utilization heat exchanger 31 into the space. Therefore, the utilization heat exchanger 31 uses the indoor air as a cooling or heating source to dissipate heat or evaporate the refrigerant. The utilization fan 32 is driven to rotate by a utilization fan motor. Here, the rotation speed (frequency) of the utilization fan motor can be controlled by an inverter or the like, and this allows the air volume of the utilization fan 32 to be controlled.

[0042] Various sensors are also provided in the utilization unit 3. Specifically, as shown in Fig. 4, the utilization unit 3 is provided with an indoor temperature sensor 34 and an indoor humidity sensor 35 that detect the temperature (indoor temperature Tr) and humidity (indoor humidity Hr) of the indoor air drawn into the utilization unit 3.

[0043] (2) Control configuration of the refrigeration cycle device As shown in Fig. 4, the refrigeration cycle apparatus 1 has a control unit 6 in which a heat source control unit 20, a usage control unit 30, and a remote control 60 are connected via transmission lines and communication lines in order to control the operation of the constituent devices. The heat source control unit 20 is provided in the heat source unit 2. The usage control unit 30 is provided in the usage unit 3. The remote control 60 is provided indoors. Note that here, the heat source control unit 20, the usage control unit 30, and the remote control 60 are connected via a wired connection via transmission lines and communication lines, but they may also be connected wirelessly.

[0044] The heat source control unit 20, the usage control unit 30, and the control device of the remote controller 60 of the refrigeration cycle apparatus 1 perform various calculations and processes, and are realized by an arithmetic processing unit such as a CPU.

[0045] (2-1) Heat source control unit As described above, the heat source control unit 20 is provided in the heat source unit 2 and mainly includes a heat source CPU 20a, a heat source transmission unit 20b, and a heat source storage unit 20c. The heat source control unit 20 is configured to be able to receive detection signals from the suction pressure sensor 28a, the suction temperature sensor 28b, the discharge pressure sensor 29a, the discharge temperature sensor 29b, and the differential pressure detection device 14.

[0046] The heat source CPU 20a is connected to a heat source transmission unit 20b and a heat source storage unit 20c. The heat source transmission unit 20b transmits control data and the like to and from the usage control unit 30. The heat source storage unit 20c stores control data and the like. The heat source CPU 20a transmits and reads and writes control data and the like via the heat source transmission unit 20b and the heat source storage unit 20c, while controlling the operation of the components of the heat source unit 2, such as the compressor 21, four-way switching valve 23, pressure reducing device 25, heat source fan 26, and pressure relief mechanism 15.

[0047] (2-2) Usage Control Unit As described above, the usage control unit 30 is provided in the usage unit 3, and mainly includes a usage CPU 30a, a usage transmission unit 30b, a usage storage unit 30c, and a usage communication unit 30d. The usage control unit 30 is configured to be able to receive detection signals from the indoor temperature sensor 34 and the indoor humidity sensor 35.

[0048] The usage CPU 30a is connected to a usage transmission unit 30b, a usage memory unit 30c, and a usage communication unit 30d. The usage transmission unit 30b transmits control data and the like to and from the heat source control unit 20. The usage memory unit 30c stores control data and the like. The usage communication unit 30d transmits and receives control data and the like to and from the remote control 60. The usage CPU 30a transmits, reads, writes, and transmits and receives control data and the like via the usage transmission unit 30b, the usage memory unit 30c, and the usage communication unit 30d, while controlling the operation of the usage fan 32 and the like as components of the usage unit 3.

[0049] (2-3) Remote Control As described above, the remote control 60 is installed indoors, and mainly includes a remote control CPU 61, a remote control storage unit 62, a remote control communication unit 63, a remote control operation unit 64, and a remote control display unit 65.

[0050] The remote control CPU 61 is connected to a remote control storage unit 62, a remote control communication unit 63, a remote control operation unit 64, and a remote control display unit 65. The remote control storage unit 62 stores control data and the like. The remote control communication unit 63 transmits and receives control data and the like to and from the usage communication unit 30d. The remote control operation unit 64 accepts input of control commands and the like from the user. The remote control display unit 65 displays operation and the like. The remote control CPU 61 accepts input of operation commands, control commands and the like via the remote control operation unit 64, reads and writes control data and the like to the remote control storage unit 62, displays the operation status and control status on the remote control display unit 65, and issues control commands and the like to the usage control unit 30 via the remote control communication unit 63.

[0051] As described above, the refrigeration cycle apparatus 1 has a control unit 6 that controls the operation of the constituent devices. The control unit 6 controls the constituent devices, such as the compressor 21, the four-way switching valve 23, the pressure reducing device 25, the heat source fan 26, the pressure relief mechanism 15, and the utilization fan 32, based on detection signals from the suction pressure sensor 28a, the suction temperature sensor 28b, the discharge pressure sensor 29a, the discharge temperature sensor 29b, the differential pressure detection device 14, the indoor temperature sensor 34, and the indoor humidity sensor 35, thereby enabling air conditioning operations such as cooling operation, dehumidification operation, and heating operation, as well as various controls.

[0052] (3) Driving behavior Next, a description will be given of the operation of the refrigeration cycle apparatus 1. The refrigeration cycle apparatus 1 of this embodiment performs heating operation, cooling operation, and dehumidifying operation as air conditioning operations.

[0053] (3-1) Heating operation Heating operation is performed by the control unit 6 receiving a command for heating operation via the remote control operation unit 64, which controls the operation of the compressor 21, four-way switching valve 23, pressure reducing device 25, heat source fan 26, utilization fan 32, etc., which are components of the heat source unit 2 and utilization unit 3.

[0054] In heating operation, the four-way switching valve 23 is switched so that the heat source heat exchanger 24 functions as an evaporator of the refrigerant and the utilization heat exchanger 31 functions as a radiator of the refrigerant (the state shown by the dashed line of the four-way switching valve 23 in Figure 1).

[0055] In the main refrigerant circuit 10 in this state, as shown in FIG. 3, low-pressure refrigerant in the refrigeration cycle is drawn into the compressor 21, compressed to the high-pressure refrigeration cycle, and then discharged. The high-pressure refrigerant discharged from the compressor 21 is sent to the utilization heat exchanger 31 through the backflow prevention device 22, the four-way switching valve 23, and the connecting pipe 4. In the utilization heat exchanger 31, the high-pressure refrigerant exchanges heat with indoor air supplied by the utilization fan 32 and dissipates heat. As a result, the indoor air is heated and blown into the room. The high-pressure refrigerant that has dissipated heat in the utilization heat exchanger 31 is sent to the pressure reducing device 25 through the connecting pipe 4 and is depressurized to the low pressure in the refrigeration cycle. The low-pressure refrigerant depressurized in the depressurizing device 25 is sent to the heat-source heat exchanger 24. In the heat-source heat exchanger 24, the low-pressure refrigerant exchanges heat with outdoor air supplied by the heat-source fan 26 and evaporates. The low-pressure refrigerant evaporated in the heat-source heat exchanger 24 is sucked back into the compressor 21 through the four-way selector valve 23. In this way, during heating operation, the control unit 6 controls the refrigerant sealed in the main refrigerant circuit 10 to circulate through the compressor 21, the utilization heat exchanger 31, the pressure reducing device 25, and the heat-source heat exchanger 24 in this order.

[0056] During heating operation, the control unit 6 performs capacity control to control the capacity of the compressor 21 so that the condensation temperature Tc of the refrigerant in the main refrigerant circuit 10 approaches a predetermined target condensation temperature Tcs. The capacity control of the compressor 21 is performed by controlling the rotation speed (frequency) of the compressor motor.

[0057] The predetermined target condensing temperature is determined, for example, by the temperature difference between the room temperature Tr detected by the room temperature sensor 34 and the set temperature Trs set by the user through the remote control operation unit 64 of the remote controller 60.

[0058] The refrigerant condensation temperature Tc is obtained by converting the discharge pressure detected by the discharge pressure sensor 29a into the saturation temperature of the refrigerant. The refrigerant condensation temperature Tc means a temperature obtained by converting the pressure (the condensation pressure of the refrigerant in the main refrigerant circuit 10) representative of the high-pressure refrigerant flowing from the discharge side of the compressor 21 through the utilization heat exchanger 31 and into the pressure reducing device 25 during heating operation into the saturation temperature of the refrigerant, or the saturation temperature of the refrigerant in the utilization heat exchanger 31 that functions as a refrigerant radiator. Therefore, if a temperature sensor is provided in the utilization heat exchanger 31, the refrigerant temperature detected by this temperature sensor may be used as the refrigerant condensation temperature Tc.

[0059] (3-2) Cooling operation The cooling operation is performed by the control unit 6 receiving a command for cooling operation via the remote control operation unit 64, which controls the operation of the compressor 21, four-way switching valve 23, pressure reducing device 25, heat source fan 26, utilization fan 32, etc., which are components of the heat source unit 2 and utilization unit 3.

[0060] In cooling operation, the four-way switching valve 23 is switched so that the heat source heat exchanger 24 functions as a refrigerant radiator and the utilization heat exchanger 31 functions as a refrigerant evaporator (the state shown by the solid line of the four-way switching valve 23 in Figure 1).

[0061] In the main refrigerant circuit 10 in this state, as shown in FIG. 2, low-pressure refrigerant in the refrigeration cycle is drawn into the compressor 21, compressed to the high-pressure refrigeration cycle, and then discharged. The high-pressure refrigerant discharged from the compressor 21 is sent to the heat-source heat exchanger 24 via the backflow prevention device 22 and the four-way switching valve 23. In the heat-source heat exchanger 24, the high-pressure refrigerant exchanges heat with outdoor air supplied by a heat-source fan 26, dissipating heat. The high-pressure refrigerant that has dissipated heat in the heat-source heat exchanger 24 is sent to the pressure reduction device 25, where it is reduced in pressure to the low pressure in the refrigeration cycle. The low-pressure refrigerant reduced in the pressure reduction device 25 is sent to the utilization heat exchanger 31 through the connecting pipe 4. In the utilization heat exchanger 31, the low-pressure refrigerant exchanges heat with indoor air supplied by a utilization fan 32, and evaporates. This cools the indoor air and blows it into the room. The low-pressure refrigerant evaporated in the utilization heat exchanger 31 is sucked back into the compressor 21 through the gas-side connecting pipe 4 and the four-way switching valve 23. In this way, during cooling operation, the control unit 6 controls the refrigerant sealed in the main refrigerant circuit 10 to circulate through the compressor 21, heat-source heat exchanger 24, pressure reducing device 25, and utilization heat exchanger 31 in this order.

[0062] During cooling operation, the control unit 6 performs capacity control to control the capacity of the compressor 21 so that the evaporation temperature Te of the refrigerant in the main refrigerant circuit 10 approaches a predetermined target evaporation temperature Teds. The capacity control of the compressor 21 is performed by controlling the rotation speed (frequency) of the compression motor.

[0063] The predetermined target evaporation temperature Teds is determined, for example, by the temperature difference between the room temperature Tr detected by the room temperature sensor 34 and the set temperature Trs set by the user through the remote control operation unit 64 of the remote controller 60.

[0064] The evaporation temperature Te of the refrigerant is obtained by converting the suction pressure detected by the suction pressure sensor 28a into the saturation temperature of the refrigerant. The evaporation temperature Te of the refrigerant means a temperature obtained by converting the pressure (evaporation pressure of the refrigerant in the main refrigerant circuit 10) representative of the low-pressure refrigerant in the refrigeration cycle that flows from the outlet of the pressure reducing device 25 through the utilization heat exchanger 31 to the suction side of the compressor 21 during cooling operation, or the saturation temperature of the refrigerant in the utilization heat exchanger 31 that functions as a refrigerant evaporator. Therefore, if a temperature sensor is provided in the utilization heat exchanger 31, the refrigerant temperature detected by this temperature sensor may be used as the evaporation temperature Te of the refrigerant.

[0065] (3-3) Dehumidification operation The dehumidification operation is performed by the control unit 6 receiving a command for dehumidification operation via the remote control operation unit 64, and controlling the operation of the compressor 21, four-way switching valve 23, pressure reducing device 25, heat source fan 26, utilization fan 32, etc., which are components of the heat source unit 2 and utilization unit 3.

[0066] In dehumidifying operation, as in cooling operation, the four-way switching valve 23 is switched so that the heat source heat exchanger 24 functions as a refrigerant radiator and the utilization heat exchanger 31 functions as a refrigerant evaporator (the state shown by the solid line of the four-way switching valve 23 in Figure 1).

[0067] In the main refrigerant circuit 10 in this state, low-pressure refrigerant in the refrigeration cycle is drawn into the compressor 21, compressed to the high-pressure level in the refrigeration cycle, and then discharged. The high-pressure refrigerant discharged from the compressor 21 is sent to the heat-source heat exchanger 24 via the four-way switching valve 23. In the heat-source heat exchanger 24, the high-pressure refrigerant exchanges heat with outdoor air supplied by a heat-source fan 26, dissipating heat. The high-pressure refrigerant that has dissipated heat in the heat-source heat exchanger 24 is sent to the pressure reducing device 25, where it is reduced in pressure to the low pressure level in the refrigeration cycle. The low-pressure refrigerant reduced in the pressure reducing device 25 is sent to the utilization heat exchanger 31 via the connecting pipe 4. In the utilization heat exchanger 31, the low-pressure refrigerant exchanges heat with indoor air supplied by a utilization fan 32, and evaporates. As a result, the indoor air is dehumidified and blown out into the room. The low-pressure refrigerant evaporated in the utilization heat exchanger 31 is sucked back into the compressor 21 through the gas-side connecting pipe 4 and the four-way switching valve 23. In this way, during dehumidification operation, the control unit 6 controls the refrigerant sealed in the main refrigerant circuit 10 to circulate through the compressor 21, the heat-source heat exchanger 24, the pressure reducing device 25, and the utilization heat exchanger 31 in this order.

[0068] The capacity control of the compressor 21 during dehumidifying operation is basically the same as the capacity control of the compressor 21 during cooling operation, except that the target evaporation temperature Tecs is set to the target evaporation temperature Teds. The target evaporation temperature Teds during dehumidifying operation is set to a value equal to or lower than the target evaporation temperature Tecs during cooling operation.

[0069] (4) Control of sleep mode and resume mode When a first condition related to the temperature or humidity of the space to be cooled or heated is satisfied, the control unit 6 executes a pause mode in which the compressor 21 is temporarily stopped. The pause mode is thermo-off.

[0070] The first condition related to temperature or humidity is that the difference between the set temperature and the room temperature, or the difference between the set humidity and the room humidity, falls within a predetermined range. For example, during cooling operation, if the set temperature is 25°C and the room temperature falls below 24.5°C, the first condition for the sleep mode is met. Also, during heating operation, if the set temperature is 22°C and the room temperature exceeds 22.5°C, the first condition for the sleep mode is met.

[0071] Furthermore, when a second condition related to temperature or humidity is satisfied, the control unit 6 transitions from the pause mode to a restart mode for restarting normal operation. The restart mode is thermo-on.

[0072] The second condition related to temperature or humidity is that the difference between the set temperature and the room temperature, or the difference between the set humidity and the room humidity, falls within a predetermined range. For example, if the set temperature is 25°C during cooling operation and the room temperature exceeds 25.5°C due to the pause mode, the second condition for the resume mode is met. Also, if the set temperature is 22°C during heating operation and the room temperature falls below 21.5°C due to the pause mode, the second condition for the resume mode is met.

[0073] The set temperature and set humidity are the target indoor temperature (set temperature Trs) and target indoor humidity set by the remote control operation unit 64. The indoor temperature is the temperature (indoor temperature Tr) measured by the indoor temperature sensor 34. The indoor humidity is the humidity (indoor humidity Hr) measured by the indoor humidity sensor 35.

[0074] In the pause mode, the control unit 6 maintains the pressure reduction device 25 in a first state in which the degree of pressure reduction is high. Here, "maintaining in the first state" means maintaining the first state for at least half of the time during the pause mode. In this embodiment, the first state is maintained for at least two-thirds of the time during the pause mode.

[0075] The first state of pressure reducing device 25 in this embodiment is a state in which the valve opening is 10% or less of the maximum valve opening. In other words, the first state may be a state in which the valve opening is 10% or less of the maximum valve opening, or a state in which the valve is fully closed. In this embodiment, the first state is a state in which the opening of the expansion valve serving as pressure reducing device 25 is zero (fully closed) or the minimum opening.

[0076] In the pause mode, the control unit 6 maintains the pressure reducing device 25 in the first state, in which the degree of pressure reduction is high, for preferably at least 2 minutes, more preferably at least 3 minutes. The upper limit of the time for maintaining the pressure reducing device 25 in the first state is the entire pause mode, and is preferably the time for the entire pause mode excluding the operation time for alleviating the pressure difference, which will be described later. The upper limit is, for example, 10 minutes.

[0077] The timing at which compressor 21 is temporarily stopped and the timing at which pressure reduction device 25 is set to the first state with a high degree of pressure reduction may be simultaneous, or one of them may occur first. In the latter case, the time difference between them is small.

[0078] When the mode shifts from the pause mode to the restart mode, the control unit 6 restarts the compressor 21 and reduces the degree of pressure reduction of the pressure reducing device 25. In this embodiment, the differential pressure driving is performed within the range of differential pressure allowed by the compressor 21.

[0079] The timing of restarting the compressor 21 and the timing of lowering the degree of pressure reduction of the pressure reducing device 25 may be simultaneous, or one of them may occur first. In the latter case, the time difference between them is small.

[0080] Here, in the restart mode, the control unit 6 restarts the compressor 21 at a predetermined low capacity, gradually decreasing the degree of pressure reduction of the pressure reduction device 25. In this embodiment, when transitioning from the pause mode to the restart mode, the control unit 6 starts the compressor 21 at a low speed, and then gradually increases the opening of the expansion valve serving as the pressure reduction device 25.

[0081] When normal operation is resumed after the transition to the restart mode, the control unit 6 controls the air conditioning operation as described above, and therefore the opening degree of the pressure reducing device 25 is controlled in accordance with the air conditioning load and the like.

[0082] Furthermore, before restarting the compressor 21, the control unit 6 acquires the differential pressure between the refrigerant pressure in the high-pressure flow path 11 and the refrigerant pressure in the low-pressure flow path 12 from the differential pressure detection device 14, and if the differential pressure is greater than a predetermined value, the relief mechanism 15 releases the pressure on the high-pressure flow path 11 side to the low-pressure flow path 12 side. In this embodiment, the relief mechanism 15 is a pressure relief valve. The predetermined value is a differential pressure at which the load applied to the compressor 21 is outside the allowable range.

[0083] From the viewpoint of reducing the load on the compressor 21, the control unit 6 may activate the relief mechanism 15 immediately before restarting the compressor 21 without checking the differential pressure.

[0084] (5) Control method of pause mode and resume mode 6, the control unit 6 starts air conditioning operation (step S1) based on an air conditioning operation command set by the user using the remote control 60. Once air conditioning operation starts, the normal operation described above in (3) is continued.

[0085] The control unit 6 determines whether a first condition related to the temperature or humidity of the indoor space to be cooled or heated is satisfied (step S2). If it is determined in step S2 that the first condition is not satisfied, the air conditioning operation continues (step S1). On the other hand, if it is determined in step S2 that the first condition is satisfied, the control unit 6 executes a pause mode in which the compressor 21 is temporarily stopped (step S3).

[0086] In the pause mode, the pressure reducing device 25 is maintained in a first state where the degree of pressure reduction is high (step S4). In this step S4, as the first state, the opening degree of the expansion valve serving as the pressure reducing device 25 is set to 10% or less of the maximum opening degree. The first state is maintained for more than half of the time during the pause mode. Here, the first state is maintained for more than two minutes.

[0087] In addition, immediately after performing step S3 of stopping compressor 21, step S4 of setting pressure reduction device 25 to the first state where the degree of pressure reduction is high may be performed, or step S3 of stopping compressor 21 and step S4 of setting pressure reduction device 25 to the first state where the degree of pressure reduction is high may be performed simultaneously.

[0088] Implementing step S4 of setting pressure reduction device 25 to the first state where the degree of pressure reduction is high makes it possible to suppress the movement of refrigerant between high-pressure flow path 11 on the upstream side of pressure reduction device 25 and low-pressure flow path 12 on the downstream side of pressure reduction device 25. Furthermore, during implementation of step S4 of setting pressure reduction device 25 to the first state where the degree of pressure reduction is high, backflow prevention device 22 can prevent refrigerant in the piping on the discharge side of compressor 21 from flowing back into compressor 21.

[0089] Next, the control unit 6 determines whether a second condition related to the temperature or humidity of the indoor space to be cooled or heated is satisfied (step S5). If it is determined in step S5 that the second condition is not satisfied, the sleep mode continues (step S3). On the other hand, if it is determined in step S5 that the second condition is satisfied, the sleep mode is switched to a resume mode for resuming normal operation.

[0090] In the restart mode, it is determined whether the differential pressure between the refrigerant pressure in the high-pressure flow path 11 and the refrigerant pressure in the low-pressure flow path 12 is equal to or less than a predetermined value (step S6). In this step S6, the differential pressure detection device 14 detects the differential pressure between the refrigerant pressure in the high-pressure flow path 11 and the refrigerant pressure in the low-pressure flow path 12. The control unit 6 receives the differential pressure from the differential pressure detection device 14 and determines whether the differential pressure is equal to or less than the predetermined value.

[0091] In step S6, if the differential pressure exceeds a predetermined value, taking into consideration the load on compressor 21, the pressure relief valve serving as relief mechanism 15 is opened to release the pressure on the high-pressure flow path 11 side to the low-pressure flow path 12 side (step S7). Note that steps S6 and S7 may be omitted.

[0092] In step S6, if the differential pressure is equal to or less than the predetermined value, and if the differential pressure becomes equal to or less than the predetermined value in step S7, the compressor 21 is restarted (step S8). In step S8, the compressor 21 is differentially driven in a state where the refrigerant is divided into high pressure and low pressure in the refrigeration cycle. In step S8 of the present embodiment, the compressor 21 is restarted at a predetermined low capacity.

[0093] Next, the opening degree of the expansion valve serving as the pressure reducing device 25 is increased (step S9). By performing this step S9, the movement of the refrigerant is promoted, and the high-pressure refrigerant and the low-pressure refrigerant are mixed. In step S9 of the present embodiment, the degree of pressure reduction of the pressure reducing device 25 is gradually reduced.

[0094] Note that step S8 of restarting the compressor 21 and step S9 of increasing the opening degree of the expansion valve may be performed simultaneously.

[0095] Normal air conditioning operation is performed by performing step S8 of restarting the compressor 21 and step S9 of increasing the opening of the expansion valve.

[0096] (6) Features (6-1) As described above, air conditioners such as those described in Patent Document 1 generally perform pressure equalization control, which fully opens the expansion valve immediately after the thermostat is turned off to equalize the pressure in the circuits between the utilization units and the heat source unit. However, performing pressure equalization control poses the problem of refrigerant heat loss due to refrigerant heat transfer between the utilization units and the heat source unit as the refrigerant moves during thermostat off. In particular, with recent improvements in insulation performance, air conditioning systems may operate at a low load where the indoor temperature approaches the set temperature and the air conditioning load is below a predetermined level. During low-load operation, thermostat on / off, which repeatedly switches between on and off, is more likely to occur. The more frequently the thermostat is turned on / off, the greater the problem of heat loss becomes when pressure equalization control is performed during thermostat off.

[0097] Therefore, the present inventors came up with the idea of ​​preventing heat loss due to pressure equalization control by not performing pressure equalization control when the thermostat is turned off, and completed the refrigeration cycle device 1 of this embodiment.

[0098] The refrigeration cycle apparatus 1 of this embodiment includes a refrigerant main circuit 10 and a control unit 6. The refrigerant main circuit 10 is connected in this order to a compressor 21, a heat source heat exchanger 24, a pressure reducing device 25, and a utilization heat exchanger 31. The control unit 6 executes a pause mode in which the compressor 21 is temporarily stopped when a first condition related to the temperature or humidity of the space to be cooled or heated is satisfied. In the pause mode, the control unit 6 maintains the pressure reducing device 25 in a first state in which the degree of pressure reduction is high.

[0099] According to the refrigeration cycle apparatus 1 of this embodiment, the pressure reducing device 25 is maintained in a throttled state in the pause mode. This makes it possible to suppress the movement of refrigerant in the main refrigerant circuit 10 in the pause mode. This makes it possible to suppress the mixing of high-pressure refrigerant and low-pressure refrigerant in the pause mode. In other words, it is possible to delay the condensation and evaporation of refrigerant in the pause mode. Therefore, until the mode shifts from the pause mode to the resume mode, most of the refrigerant in the main refrigerant circuit 10 can be maintained in the state it was in before the pause mode. This makes it possible to suppress heat loss of the refrigerant in the main refrigerant circuit 10.

[0100] In this way, the refrigeration cycle device 1 of this embodiment is particularly effective during low load operation because it can suppress heat loss during pause mode by maintaining the differential pressure in pause mode and driving the compressor 21 by differential pressure in resume mode.

[0101] "Low load operation" is an operation in which a substitute value indicating the load during air conditioning operation satisfies a predetermined condition. The substitute value is, for example, the rated capacity of the refrigeration cycle device 1, and the predetermined condition is 45% or less of the rated capacity. In other words, low load operation occurs when the load is 45% or less of the rated capacity. The rated capacity is a value equivalent to the "nominal capacity" listed in the product catalog or instruction manual.

[0102] (6-2) Here, the pressure reducing device 25 is a valve whose opening degree can be changed. The first state of the pressure reducing device 25 is a state in which the valve opening degree is 10% or less of the maximum valve opening degree. In the first state, the degree of pressure reduction is very high, so that the movement of the refrigerant in the main refrigerant circuit 10 can be further suppressed during the pause mode. Therefore, heat loss of the refrigerant can be further suppressed.

[0103] In particular, during low-load operation, the heat loss effect can be enhanced in the first state where the valve is fully closed or very small. From this perspective, the first state of pressure reducing device 25 is preferably a state where the valve is minimum open or fully closed.

[0104] (6-3) Here, in the pause mode, the control unit 6 maintains the pressure reducing device 25 in the first state, in which the degree of pressure reduction is high, for at least two minutes or more. This further suppresses the movement of the refrigerant in the main refrigerant circuit 10 during the pause mode, thereby further suppressing heat loss of the refrigerant.

[0105] (6-4) Here, the refrigerant main circuit 10 is provided with a backflow prevention device 22 in the piping on the refrigerant discharge side of the compressor 21, which prevents the refrigerant from flowing back into the compressor 21. The backflow prevention device 22 can prevent the refrigerant from entering the compressor 21 from the discharge side during the pause mode. This can prevent the refrigerant from moving in the refrigerant main circuit 10, thereby further reducing heat loss of the refrigerant.

[0106] (6-5) Here, the main refrigerant circuit 10 is divided into a high-pressure flow path 11 on the upstream side of the pressure reducing device 25 in the refrigerant flow direction, and a low-pressure flow path 12 on the downstream side of the refrigerant flow direction of the pressure reducing device 25. The refrigeration cycle apparatus 1 further includes a differential pressure detection device 14. The differential pressure detection device 14 detects the difference between the pressure of the refrigerant flowing through the high-pressure flow path 11 and the pressure of the refrigerant flowing through the low-pressure flow path 12. The differential pressure detection device 14 can confirm the differential pressure between the pressure of the refrigerant flowing through the high-pressure flow path 11 and the pressure of the refrigerant flowing through the low-pressure flow path 12. Therefore, the compressor 21 can be restarted only after confirming that the differential pressure is at a level that allows restarting the compressor 21.

[0107] (6-6) Here, the refrigeration cycle apparatus 1 further includes a bypass pipe 13 and a pressure relief mechanism 15. The bypass pipe 13 connects the high-pressure flow path 11 and the low-pressure flow path 12. The relief mechanism 15 relieves the pressure on the high-pressure flow path 11 side of the bypass pipe 13 to the low-pressure flow path 12 side. As a result, the relief mechanism 15 can relieve the pressure on the high-pressure flow path 11 side to the low-pressure flow path 12 side just before restarting the compressor 21. Therefore, the relief mechanism 15 can reduce the differential pressure to a level at which restarting the compressor 21 is permitted, reduce the load on the compressor 21 to a low differential pressure, etc.

[0108] Just before restarting the compressor 21, the pressure on the high-pressure flow path 11 side is released to the low-pressure flow path 12 side by the release mechanism 15, so the refrigerant moves in a short time. Also, the purpose is not to release the pressure until it is equalized, but to reduce the pressure difference taking into account the load on the compressor 21. Therefore, the effect of heat loss is small, and heat loss can be reduced compared to when conventional pressure equalization control is performed.

[0109] (6-7) Here, when a second condition related to temperature or humidity is satisfied, the control unit 6 transitions from the pause mode to a restart mode for resuming normal operation. In the restart mode, the control unit 6 restarts the compressor 21 at a predetermined low capacity, gradually decreasing the degree of pressure reduction of the pressure reducing device 25. This reduces the load on the compressor 21 due to the pressure difference when transitioning from the pause mode to the restart mode.

[0110] (7) Variations (7-1) Variation 1 In the above-described embodiment, in the pause mode, the valve opening of pressure reducing device 25 is maintained in the first state at 10% or less of the maximum opening, but in the present disclosure, the present invention is not limited to this as long as the degree of pressure reduction of pressure reducing device 25 is increased in order to suppress the movement of refrigerant during the pause mode. In this modification, when transitioning to the pause mode, control unit 6 reduces the valve opening to a smaller value than the valve opening immediately before the pause mode.

[0111] 5, when the compressor 21 is stopped (step S3), the control unit 6 reduces the opening of the expansion valve to a smaller opening than that immediately before the compressor 21 was stopped. In other words, when the control unit 6 stops the compressor 21 (step S3), the control unit 6 reduces the opening of the expansion valve to a smaller opening than that immediately before the compressor 21 was stopped (step S4). This results in a first state in which the degree of pressure reduction of the expansion valve is high, and this first state is maintained in the pause mode.

[0112] As described above, in this modification, the pressure reducing device 25 is a valve whose opening degree can be changed. The first state of the pressure reducing device 25 is a state in which the opening degree of the valve is smaller than the opening degree of the valve immediately before the pause mode is executed. This makes it possible to suppress the movement of the refrigerant in the main refrigerant circuit 10 during the pause mode. Therefore, it is possible to easily realize a refrigeration cycle apparatus 1 that can suppress heat loss of the refrigerant.

[0113] (7-2) Variation 2 In the above-described embodiment, in the restart mode, the compressor 21 is restarted at a predetermined low capacity, and the degree of pressure reduction of the pressure reducing device 25 is gradually reduced, but the present invention is not limited to this.

[0114] In this modification, in the restart mode, first the degree of pressure reduction of the pressure reduction device 25 is reduced, and then the compressor 21 is restarted. Furthermore, in the restart mode, the control unit 6 operates the heat source fan 26, the utilization fan 32, or both the heat source fan 26 and the utilization fan 32 before restarting the compressor 21. In other words, when transitioning from the pause mode to the restart mode, the control unit 6 operates the heat source fan 26, the utilization fan 32, or both the heat source fan 26 and the utilization fan 32, and then increases the opening of the expansion valve serving as the pressure reduction device 25 before restarting the compressor 21.

[0115] 6, when the second condition related to temperature or humidity is satisfied in step S5 and the mode transitions from the pause mode to the resume mode for resuming normal operation, the control unit 6 activates the heat source fan 26, the utilization fan 32, or both the heat source fan 26 and the utilization fan 32 (step S10). In other words, when transitioning from the pause mode to the resume mode, the control unit 6 activates the heat source fan 26, the utilization fan 32, or both the heat source fan 26 and the utilization fan 32 (step S10) before restarting the compressor 21 (step S8).

[0116] Note that step S7 of activating the release mechanism 15 and step S10 of activating the fan may be performed either first or simultaneously. Also, at least one of steps S7 and S10 may be omitted.

[0117] Next, the control unit 6 decreases the degree of pressure reduction of the pressure reducing device 25 (step S9). In this step S9, the opening degree of the expansion valve serving as the pressure reducing device 25 is increased.

[0118] Next, the control unit 6 restarts the compressor 21 (step S9). In this step S9, the compressor 21 is restarted at the normal capacity, not at the low capacity.

[0119] Thus, in this modified example, when transitioning from pause mode to resume mode, the control unit 6 activates the heat source fan 26, the utilization fan 32, or both the heat source fan 26 and the utilization fan 32 (step S10), then increases the opening of the valve of the pressure reducing device 25 (step S9), and then restarts the compressor 21 (step S8).

[0120] In addition, from the viewpoint of reducing the load on the compressor 21, the control unit 6 may operate the heat source fan 26, the utilization fan 32, or both the heat source fan 26 and the utilization fan 32 without checking the differential pressure immediately before restarting the compressor 21.

[0121] In the refrigeration cycle apparatus 1 of this modified example, in the restart mode, the control unit 6 first reduces the degree of pressure reduction of the pressure reduction device 25, and then restarts the compressor 21. This reduces the pressure difference between the pressure of the refrigerant flowing through the high-pressure flow path 11 and the pressure of the refrigerant flowing through the low-pressure flow path 12. In this way, the pressure difference can be reduced before restarting the compressor 21, thereby reducing the burden on the compressor 21.

[0122] Furthermore, when the differential pressure is large, the control of this modified example (control in which, in the restart mode, the degree of pressure reduction of the pressure reduction device 25 is first reduced and then the compressor 21 is restarted) is advantageous, whereas when the differential pressure is small, the control of the embodiment (control in which, in the restart mode, the compressor 21 is restarted at a predetermined low capacity and the degree of pressure reduction of the pressure reduction device 25 is gradually reduced) is advantageous. For this reason, if the differential pressure is equal to or lower than a predetermined value and exceeds the first threshold in S6, it is preferable to first reduce the degree of pressure reduction of the pressure reduction device 25 and then restart the compressor 21 in the restart mode, and if the differential pressure is equal to or lower than the first threshold, to restart the compressor 21 at a predetermined low capacity and gradually reduce the degree of pressure reduction of the pressure reduction device 25 in the restart mode.

[0123] This modified example further includes a heat source fan 26 and a utilization fan 32. The heat source fan 26 passes air as a heat source through the heat source heat exchanger 24. The utilization fan 32 passes air from the space to be cooled or heated through the utilization heat exchanger 31. In the restart mode, the control unit 6 operates the heat source fan 26, the utilization fan 32, or both the heat source fan 26 and the utilization fan 32 before restarting the compressor 21. This promotes heat exchange of the refrigerant in the heat source unit 2, the utilization unit 3, or both the heat source unit 2 and the utilization unit 3. Therefore, the differential pressure can be further reduced before restarting the compressor 21, thereby further reducing the burden on the compressor 21.

[0124] The heat source fan 26, the utilization fan 32, or both the heat source fan 26 and the utilization fan 32 are operated immediately before restarting the compressor 21, so the movement of the refrigerant is short. Furthermore, the operation of the heat source fan 26, the utilization fan 32, or both the heat source fan 26 and the utilization fan 32 is not continued until the pressure is equalized, but is aimed at reducing the pressure difference in consideration of the load on the compressor 21. Therefore, the effect of heat loss is small, and heat loss can be reduced compared to when conventional pressure equalization control is performed.

[0125] (7-3) Variation 3 In the above-described embodiment, the differential pressure detection device 14 is provided in the bypass pipe 13 connecting the discharge pipe and the suction pipe of the compressor 21, but the present invention is not limited to this. In this modified example, as shown in Fig. 7, the differential pressure detection device 14 is provided in the bypass pipe 16 connecting the liquid side and the gas side of the pressure reducing device 25. Note that the high-pressure flow path 11 and the low-pressure flow path 12 of the liquid side pipe and the gas side pipe of the pressure reducing device 25 are interchanged during cooling operation shown in Fig. 2 and heating operation shown in Fig. 3.

[0126] (7-4) Variation 4 In the above-described embodiment and Modification 3, the differential pressure detection device 14 is provided to check the differential pressure, but the differential pressure detection device 14 may be omitted. In this modification, the temperature of the heat source heat exchanger 24 or the utilization heat exchanger 31 immediately before entering the sleep mode is used to check the differential pressure. Specifically, the control unit 6 determines the differential pressure from the condensation temperature and evaporation temperature of the main refrigerant circuit 10.

[0127] (7-5) Variation 5 In the above-described embodiment, the pressure relief mechanism 15 is provided in the bypass pipe 13 connecting the discharge pipe and the suction pipe of the compressor 21, but is not limited to this. The pressure relief mechanism 15 is provided, for example, in the bypass pipe 16 connecting the liquid side and the gas side of the pressure reducing device 25.

[0128] (7-6) Variation 6 In the above-described embodiment, the refrigeration cycle apparatus 1 performs cooling, dehumidifying, and heating operations, but the refrigeration cycle apparatus of the present disclosure is not limited to this as long as it performs air-conditioning operations. The refrigeration cycle apparatus of this modification is, for example, dedicated to cooling.

[0129] (7-7) Variation 7 In the above-described embodiment, an air conditioner has been described as an example of a refrigeration cycle apparatus, but the refrigeration cycle apparatus of the present disclosure is not limited to this. The refrigeration cycle apparatus of the present disclosure may be, for example, a heat pump water heater.

[0130] Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as defined in the claims. [Explanation of symbols]

[0131] 1: Refrigeration cycle device 6: Control section 10: Refrigerant main circuit 11: High-pressure flow path 12: Low pressure flow path 13,16: Bypass piping 14: Differential pressure detection device 15: Escape mechanism 21: Compressor 22: Backflow prevention device 24:Heat source heat exchanger 25: Pressure reducing device 26: Heat source fan 31: Utilization heat exchanger 32: Fans in use [Prior art documents] [Patent documents]

[0132] [Patent Document 1] Japanese Patent Application Publication No. 2018-128158

Claims

1. a refrigerant main circuit (10) in which a compressor (21), a heat source heat exchanger (24), a pressure reducing device (25), and a utilization heat exchanger (31) are connected in this order; a control unit (6) that executes a pause mode in which the compressor is temporarily stopped when a first condition related to the temperature or humidity of the space to be cooled or heated is satisfied; Equipped with The control unit maintains the decompression device in a first state in which the degree of decompression is high in the pause mode, The control unit transitioning from the pause mode to a resume mode for resuming normal operation when a second condition related to the temperature or the humidity is satisfied; The main refrigerant circuit is divided into a high-pressure flow path (11) on the upstream side of the pressure reducing device in the refrigerant flow direction and a low-pressure flow path (12) on the downstream side of the refrigerant flow direction of the pressure reducing device, a differential pressure detection device (14) for detecting a difference between the pressure of the refrigerant flowing through the high-pressure flow path and the pressure of the refrigerant flowing through the low-pressure flow path, The control unit Before restarting the compressor, a differential pressure between the pressure of the refrigerant in the high-pressure flow path and the pressure of the refrigerant in the low-pressure flow path is obtained from the differential pressure detection device; If the differential pressure is equal to or less than a predetermined value and exceeds a first threshold value, in the restart mode, first, the degree of pressure reduction of the pressure reducing device is reduced, and then the compressor is restarted; If the difference is equal to or less than the first threshold, in the restart mode, the compressor is restarted at a predetermined low capacity, and the degree of pressure reduction of the pressure reducing device is gradually reduced. Refrigeration cycle device (1).

2. The pressure reducing device is a valve whose opening degree can be changed, The first state of the pressure reducing device is a state in which the opening degree of the valve is 10% or less of the maximum opening degree of the valve. The refrigeration cycle device according to claim 1.

3. The pressure reducing device is a valve whose opening degree can be changed, The first state of the pressure reducing device is a state in which an opening degree of the valve is smaller than an opening degree of the valve immediately before the execution of the pause mode. The refrigeration cycle device according to claim 1.

4. The control unit maintains the decompression device in a first state in which the degree of decompression is high for at least two minutes in the pause mode. The refrigeration cycle device according to any one of claims 1 to 3.

5. The main refrigerant circuit is provided with a backflow prevention device (22) in a pipe on the refrigerant discharge side of the compressor, the backflow prevention device preventing the refrigerant from flowing back into the compressor. The refrigeration cycle device according to any one of claims 1 to 4.

6. A bypass pipe (13) connecting the high-pressure flow path and the low-pressure flow path; a mechanism (15) for releasing pressure from the high-pressure flow path side to the low-pressure flow path side in the bypass piping; Further provided with The refrigeration cycle device according to any one of claims 1 to 5.

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