JP7783480B2 - Refrigeration cycle equipment - Google Patents

Description

Regarding refrigeration cycle equipment.

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. During this type of air conditioning operation, when the indoor temperature reaches the target temperature and air conditioning operation is no longer necessary, the compressor is stopped and thermo-off is performed, pausing air conditioning operation. Furthermore, if the indoor temperature deviates from the target indoor temperature after thermo-off and air conditioning operation is required, the compressor is restarted and thermo-on is performed, resuming air conditioning operation.

Generally, immediately after an air conditioner like the one described in Patent Document 1 switches off its thermostat, it performs pressure equalization control, which fully opens the expansion valve to equalize the pressure in the circuits between the utilization units and the heat source unit. However, performing pressure equalization control results in significant heat loss from the refrigerant during the thermostat off period.

A refrigeration cycle device according to a first aspect includes a main refrigerant circuit and a control unit. The main refrigerant circuit is connected in order to a compressor, a heat source heat exchanger, a pressure reduction device, and a utilization heat exchanger. 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 the space to be cooled or heated is met. 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.

According to the refrigeration cycle device of the first aspect, in the pause mode in which the compressor is temporarily stopped, the pressure reduction 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. Therefore, it is possible to suppress heat loss of the refrigerant in the main refrigerant circuit.

A refrigeration cycle apparatus according to a second aspect is the refrigeration cycle apparatus according to the first aspect, in which the pressure reducing device is a valve whose opening degree is changeable. 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.

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

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

In the refrigeration cycle device according to the third aspect, the valve opening is reduced when the device is in pause mode. This makes it easy to realize a refrigeration cycle device that can suppress refrigerant heat loss by suppressing the movement of refrigerant in the main refrigerant circuit during pause mode.

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

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

The refrigeration cycle apparatus according to a fifth aspect is the refrigeration cycle apparatus 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, which prevents refrigerant from flowing back into the compressor.

In the refrigeration cycle apparatus according to the fifth aspect, the backflow prevention device can prevent refrigerant from flowing back into the compressor from the discharge side during pause mode. This further reduces heat loss from the refrigerant.

A refrigeration cycle apparatus according to a sixth aspect is a refrigeration cycle apparatus according to any one of 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. The differential pressure detection device detects the 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.

In the refrigeration cycle apparatus according to the sixth aspect, the differential pressure detection device can confirm the pressure 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. Therefore, the compressor can be restarted after confirming the differential pressure.

A refrigeration cycle apparatus according to a seventh aspect is a refrigeration cycle apparatus according to any one of 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.

In the refrigeration cycle apparatus according to the seventh aspect, the pressure in the high-pressure flow path can be released to the low-pressure flow path by the relief mechanism just before restarting the compressor. This makes it easy to restart the compressor.

The 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, gradually reducing the degree of pressure reduction of the pressure-reducing device.

In the refrigeration cycle device according to the eighth aspect, the compressor is restarted at a low capacity in restart mode, thereby reducing the load on the compressor.

A refrigeration cycle apparatus according to a ninth aspect is a 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 degree of pressure reduction of the pressure reduction device is first reduced, and then the compressor is restarted.

In the refrigeration cycle apparatus according to the ninth aspect, in restart mode, the degree of pressure reduction of the pressure reducing device can be reduced, thereby reducing the pressure 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. In this way, the pressure difference can be reduced before the compressor is restarted, thereby reducing the burden on the compressor.

A refrigeration cycle apparatus according to a tenth aspect is the refrigeration cycle apparatus according to the ninth aspect, further comprising 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 from the 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.

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 allows the pressure difference to be reduced further before the compressor is restarted, thereby further reducing the burden on the compressor.

1 is a schematic configuration diagram of a refrigeration cycle device according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating the operation (flow of refrigerant) during cooling operation of the refrigeration cycle device according to the embodiment of the present disclosure. FIG. 2 is a diagram illustrating an operation (flow of refrigerant) during heating operation of the refrigeration cycle device according to the embodiment of the present disclosure. FIG. 2 is a control block diagram of a refrigeration cycle device according to an embodiment of the present disclosure. 4 is a flowchart illustrating a control method for a refrigeration cycle device according to an embodiment of the present disclosure. 10 is a flowchart illustrating a control method for a refrigeration cycle device according to a modified example of the present disclosure. FIG. 10 is a schematic configuration diagram of a refrigeration cycle device according to a modified example.

(1) Equipment Configuration of the Refrigeration Cycle Apparatus 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. The 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.

(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 communication 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.

The compressor 21 is a mechanism that compresses low-pressure refrigerant in the refrigeration cycle to high pressure. Here, a sealed compressor is used as the compressor 21, in which a rotary, scroll, or other volumetric compression element (not shown) is driven and rotated by a compressor motor. The compressor motor's rotation speed (frequency) can be controlled using an inverter or similar, allowing the capacity of the compressor 21 to be controlled.

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

The four-way switching valve 23 switches the direction of refrigerant flow when switching between cooling or dehumidifying operation and heating operation. During cooling or dehumidifying 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 the utilization heat exchanger 31 (described below) to the suction side of the compressor 21 via the gas side connecting pipe 4 (see the solid lines of the four-way switching valve 23 in Figure 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 connecting 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 Figure 1).

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.

The pressure reducing device 25 is an expansion mechanism that reduces 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 or dehumidifying operation, and that reduces 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.

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 it outside 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 driven to rotate by a heat source fan motor.

The heat source unit 2 also has a bypass pipe 13 that connects the high-pressure flow path 11 and 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, which serves as the high-pressure flow path 11, and the suction pipe of the compressor 21, which serves as the low-pressure flow path 12. The discharge pipe and suction pipe of the compressor 21 do not change between the high-pressure flow path 11 and the low-pressure flow path 12 during cooling operation and heating operation.

The bypass pipe 13 is equipped with a differential pressure detection device 14 and a pressure relief mechanism 15. In this example, the bypass pipe 13 branches into two, with the differential pressure detection device 14 installed in one branch pipe and the pressure relief mechanism 15 installed in the other branch pipe.

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. In this case, the differential pressure detection device 14 is a differential pressure sensor.

The relief mechanism 15 relieves pressure on the high-pressure flow path 11 side of the bypass piping 13 to the low-pressure flow path 12 side. In this case, the relief mechanism 15 is a pressure relief valve.

The heat source unit 2 is also provided with various sensors. Specifically, as shown in FIG. 4, the heat source unit 2 is provided with an intake pressure sensor 28a that detects the intake pressure of the compressor 21, an intake temperature sensor 28b that detects the intake 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.

(1-2) Communication Pipe The communication pipe 4 is a refrigerant pipe that is 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 communication pipe 4 (the lower communication 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 communication 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 communication pipe 4 (the upper communication 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 communication pipe 4 is connected to the gas side of the utilization heat exchanger 31 of the utilization unit 3.

(1-3) User Unit The user unit 3 is installed indoors (inside the building). As described above, the user 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 user unit 3 mainly has a user heat exchanger 31 and a user fan 32.

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 liquid side of the utilization heat exchanger 31 is connected to the liquid side connecting pipe 4, and its gas side is connected to the gas side connecting pipe 4.

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 using an inverter or the like, which allows the airflow volume of the utilization fan 32 to be controlled.

The utilization unit 3 is also provided with various sensors. 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.

(2) Control configuration of the refrigeration cycle device As shown in Fig. 4, the refrigeration cycle device 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.

The heat source control unit 20, usage control unit 30, and remote control 60 control devices of the refrigeration cycle device 1 perform various calculations and processes, and are realized, for example, by a processing unit such as a CPU.

(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 memory 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.

The heat source CPU 20a is connected to the heat source transmission unit 20b and the heat source memory 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 memory unit 20c stores control data and the like. The heat source CPU 20a transmits and reads/writes control data and the like via the heat source transmission unit 20b and the heat source memory 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.

(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.

The usage CPU 30a is connected to the usage transmission unit 30b, usage memory unit 30c, and 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, usage memory unit 30c, and usage communication unit 30d, while controlling the operation of the usage fan 32 and other components provided in the usage unit 3.

(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 memory unit 62, a remote control communication unit 63, a remote control operation unit 64, and a remote control display unit 65.

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, etc. The remote control communication unit 63 sends and receives control data, etc., to and from the usage communication unit 30d. The remote control operation unit 64 accepts control commands, etc., input from the user. The remote control display unit 65 displays operation information, etc. The remote control CPU 61 accepts input of operation commands, control commands, etc., via the remote control operation unit 64, reads and writes control data, etc., to the remote control storage unit 62, and issues control commands, etc., to the usage control unit 30 via the remote control communication unit 63 while displaying the operation status and control status on the remote control display unit 65.

As such, the refrigeration cycle system 1 has a control unit 6 that controls the operation of the component equipment. The control unit 6 controls the component equipment, such as the compressor 21, four-way switching valve 23, pressure reducing device 25, heat source fan 26, pressure relief mechanism 15, and utilization fan 32, based on detection signals from the suction pressure sensor 28a, suction temperature sensor 28b, discharge pressure sensor 29a, discharge temperature sensor 29b, differential pressure detection device 14, indoor temperature sensor 34, and indoor humidity sensor 35, and is configured to perform air conditioning operations such as cooling, dehumidification, and heating, as well as various controls.

(3) Operation 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 dehumidification operation as air conditioning operations.

(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, 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.

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

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 via the backflow prevention device 22, four-way switching valve 23, and connecting piping 4. In the utilization heat exchanger 31, the high-pressure refrigerant exchanges heat with indoor air supplied by the utilization fan 32, dissipating heat. This heats the indoor air and blows it into the room. The high-pressure refrigerant that has dissipated heat in the utilization heat exchanger 31 is sent to the pressure reduction device 25 via the connecting piping 4 and reduced in pressure to the low pressure in the refrigeration cycle. The low-pressure refrigerant reduced in pressure reduction 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, evaporating. The low-pressure refrigerant that has evaporated in the heat source heat exchanger 24 is sucked back into the compressor 21 through the four-way switching valve 23. In this way, during heating operation, the control unit 6 causes the refrigerant sealed in the main refrigerant circuit 10 to circulate through the compressor 21, utilization heat exchanger 31, pressure reducing device 25, and heat source heat exchanger 24 in that order.

During heating operation, the control unit 6 performs capacity control to adjust 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.

The specified target condensing temperature is determined, for example, by the temperature difference between the indoor temperature Tr detected by the indoor temperature sensor 34 and the set temperature Trs set by the user via the remote control operation unit 64 of the remote control 60.

The refrigerant condensation temperature Tc is obtained by converting the discharge pressure detected by the discharge pressure sensor 29a to the refrigerant saturation temperature. The refrigerant condensation temperature Tc refers to the temperature obtained by converting the pressure (refrigerant condensation pressure 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, or the refrigerant saturation temperature in the utilization heat exchanger 31, which 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.

(3-2) Cooling operation Cooling operation is performed by the control unit 6, which receives a command for cooling operation via the remote control operation unit 64, 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.

During 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).

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 four-way switching valve 23. The high-pressure refrigerant sent to the heat-source heat exchanger 24 exchanges heat with outdoor air supplied by the heat-source fan 26 in the heat-source heat exchanger 24, 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. The low-pressure refrigerant sent to the utilization heat exchanger 31 exchanges heat with indoor air supplied by the utilization fan 32 in the utilization heat exchanger 31, evaporating. This cools the indoor air and blows it into the room. The low-pressure refrigerant that has evaporated in the utilization heat exchanger 31 is sucked back into the compressor 21 via the gas-side connecting pipe 4 and the four-way switching valve 23. In this way, during cooling operation, the control unit 6 causes 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 that order.

During cooling operation, the control unit 6 performs capacity control to adjust 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.

The predetermined target evaporation temperature Teds is determined, for example, by the temperature difference between the indoor temperature Tr detected by the indoor temperature sensor 34 and the set temperature Trs set by the user via the remote control operation unit 64 of the remote control 60.

The refrigerant evaporation temperature Te is obtained by converting the suction pressure detected by the suction pressure sensor 28a to the saturation temperature of the refrigerant. The refrigerant evaporation temperature Te refers to the 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, via 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, which 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 refrigerant evaporation temperature Te.

(3-3) Dehumidification operation The dehumidification operation is performed by the control unit 6, which receives a command for dehumidification operation via the remote control operation unit 64, 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.

In dehumidification 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).

In this state of the main refrigerant circuit 10, low-pressure refrigerant in the refrigeration cycle is drawn into the compressor 21, compressed to the high-pressure level of 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. The high-pressure refrigerant sent to the heat-source heat exchanger 24 exchanges heat with outdoor air supplied by the heat-source fan 26 in the heat-source heat exchanger 24, 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 of the refrigeration cycle. The low-pressure refrigerant reduced in the pressure reduction device 25 is sent to the utilization heat exchanger 31 via the connecting pipe 4. The low-pressure refrigerant sent to the utilization heat exchanger 31 exchanges heat with indoor air supplied by the utilization fan 32 in the utilization heat exchanger 31, evaporating. This dehumidifies the indoor air and blows it out into the room. The low-pressure refrigerant that has evaporated in the utilization heat exchanger 31 is sucked back into the compressor 21 via the gas-side connecting pipe 4 and the four-way switching valve 23. In this way, during dehumidification operation, the control unit 6 causes 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 that order.

Capacity control of the compressor 21 during dehumidification operation is basically the same as 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 dehumidification operation is set to a value lower than the target evaporation temperature Tecs during cooling operation.

(4) Control of Pause 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.

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 specified 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 pause 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 pause mode is met.

Furthermore, when a second condition related to temperature or humidity is met, the control unit 6 transitions from the sleep mode to a resume mode to resume normal operation. The resume mode is thermo-on.

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 specified range. For example, if the set temperature is 25°C during cooling operation and the room temperature exceeds 25.5°C due to pause mode, the second condition for 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 pause mode, the second condition for resume mode is met.

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

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 more than half of the time during the pause mode. In this embodiment, the first state is maintained for more than two-thirds of the time during the pause mode.

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

In the pause mode, the control unit 6 maintains the pressure reduction device 25 in the first state, which has a high degree of pressure reduction, for preferably at least two minutes, and more preferably at least three minutes. The upper limit for the time that the pressure reduction device 25 is maintained in the first state is the entire pause mode, and is preferably the entire pause mode excluding the operating time for alleviating the pressure difference, which will be described later. The upper limit is, for example, 10 minutes.

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

When the control unit 6 transitions from pause mode to resume mode, it restarts the compressor 21 and reduces the degree of pressure reduction of the pressure reduction device 25. In this embodiment, differential pressure driving is performed within the differential pressure range allowed by the compressor 21.

Note that the timing for restarting the compressor 21 and the timing for reducing the degree of pressure reduction of the pressure reduction device 25 may be simultaneous, or one may occur first. In the latter case, the time difference between them is small.

Here, in restart mode, the control unit 6 restarts the compressor 21 at a predetermined low capacity, gradually reducing the degree of pressure reduction by the pressure reduction device 25. In this embodiment, when transitioning from pause mode to 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.

When normal operation resumes after switching to restart mode, the control unit 6 controls the air conditioning operation as described above, and the opening degree of the pressure reducing device 25 is controlled according to the air conditioning load, etc.

In addition, before restarting the compressor 21, the control unit 6 obtains 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 the differential pressure at which the load applied to the compressor 21 is outside the allowable range.

In addition, from the perspective of reducing the load on the compressor 21, the control unit 6 may activate the relief mechanism 15 without checking the differential pressure immediately before restarting the compressor 21.

(5) Control Method of Pause Mode and Resume Mode As shown in Fig. 6, the control unit 6 starts air conditioning operation (step S1) based on an air conditioning operation command set by the user via the remote controller 60. Once air conditioning operation starts, the normal operation described in (3) above continues.

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 met (step S2). If it is determined in step S2 that the first condition is not met, air conditioning operation continues (step S1). On the other hand, if it is determined in step S2 that the first condition is met, a pause mode is executed, in which the compressor 21 is temporarily stopped (step S3).

In the pause mode, the pressure reducing device 25 is maintained in a first state in which the degree of pressure reduction is high (step S4). In this step S4, the opening of the expansion valve serving as the pressure reducing device 25 is set to 10% or less of its maximum opening as the first state. 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.

In addition, step S4 of setting the pressure reduction device 25 to the first state with a high degree of pressure reduction may be performed immediately after step S3 of stopping the compressor 21, or step S3 of stopping the compressor 21 and step S4 of setting the pressure reduction device 25 to the first state with a high degree of pressure reduction may be performed simultaneously.

By performing step S4, which sets the pressure reduction device 25 to the first state with a high degree of pressure reduction, it is possible to suppress the movement of refrigerant between the high-pressure flow path 11 upstream of the pressure reduction device 25 and the low-pressure flow path 12 downstream of the pressure reduction device 25. Furthermore, while performing step S4, which sets the pressure reduction device 25 to the first state with a high degree of pressure reduction, the backflow prevention device 22 can prevent refrigerant in the piping on the discharge side of the compressor 21 from flowing back into the compressor 21.

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 met (step S5). If it is determined in step S5 that the second condition is not met, the sleep mode continues (step S3). On the other hand, if it is determined in step S5 that the second condition is met, the system transitions from the sleep mode to a resume mode to resume normal operation.

In 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 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.

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

If the differential pressure is equal to or less than the predetermined value in step S6, or 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 while the refrigerant is divided into high-pressure and low-pressure refrigerants in the refrigeration cycle. In step S8 of this embodiment, the compressor 21 is restarted at a predetermined low capacity.

Next, the opening of the expansion valve serving as the pressure reducing device 25 is increased (step S9). Performing step S9 promotes refrigerant movement, resulting in mixing of high-pressure refrigerant and low-pressure refrigerant. In step S9 of this embodiment, the degree of pressure reduction by the pressure reducing device 25 is gradually reduced.

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

Normal air conditioning operation is performed by performing step S8, which restarts the compressor 21, and step S9, which increases the opening of the expansion valve.

(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 cycles between thermostat on and thermostat off, is more likely to occur. The more frequently the thermostat is turned on/off, the greater the problem of heat loss becomes if pressure equalization control is performed during thermostat off.

The inventors therefore came up with the idea of preventing heat loss associated with 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.

The refrigeration cycle apparatus 1 of this embodiment includes a main refrigerant circuit 10 and a control unit 6. The main refrigerant circuit 10 is connected in order to a compressor 21, a heat source heat exchanger 24, a pressure reduction 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 met. 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.

In the refrigeration cycle apparatus 1 of this embodiment, the pressure reducing device 25 is maintained in a throttled state in pause mode. This suppresses the movement of refrigerant in the main refrigerant circuit 10 during pause mode. This prevents high-pressure refrigerant and low-pressure refrigerant from mixing during pause mode. In other words, condensation and evaporation of refrigerant can be delayed during pause mode. Therefore, until transitioning from pause mode to resume mode, much of the refrigerant in the main refrigerant circuit 10 can be maintained in the state it was in before pause mode. This suppresses heat loss of the refrigerant in the main refrigerant circuit 10.

In this way, the refrigeration cycle device 1 of this embodiment maintains the differential pressure in pause mode and drives the compressor 21 with the differential pressure in resume mode, thereby suppressing heat loss during pause mode, making it particularly effective during low-load operation.

Note that "low-load operation" refers to operation in which a substitute value indicating the load during air conditioning operation satisfies a specified condition. The substitute value is, for example, the rated capacity of the refrigeration cycle device 1, and the specified 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. Note that the rated capacity is the same value as the "nominal capacity" listed in the product catalog or instruction manual.

(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 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.

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 the pressure reducing device 25 is preferably one in which the valve is at its smallest opening or fully closed.

(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.

(6-4)
Here, the main refrigerant 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 main refrigerant circuit 10, thereby further reducing heat loss of the refrigerant.

(6-5)
Here, the main refrigerant 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. 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.

(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 immediately 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 differential pressure to a level at which the load on the compressor 21 is low, and so on.

In addition, just before the compressor 21 is restarted, 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 for a short time. Furthermore, rather than releasing the pressure until it is equalized, the purpose is to reduce the pressure difference taking into account the load on the compressor 21. As a result, the impact of heat loss is small, and heat loss can be reduced compared to conventional pressure equalization control.

(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 by 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.

(7) Modifications (7-1) Modification 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 disclosure 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.

Specifically, in step S4 of FIG. 5, when the compressor 21 is stopped (step S3), the control unit 6 opens the expansion valve to a smaller degree than the opening degree immediately before the compressor 21 was stopped. In other words, when the control unit 6 stops the compressor 21 (step S3), it narrows the opening degree of the expansion valve to a degree less than the opening degree of the expansion valve 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.

In this way, in this modified example, 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 smaller than the valve opening degree immediately before the pause mode is executed. This makes it possible to suppress the movement of refrigerant in the main refrigerant circuit 10 during the pause mode. Therefore, it is easy to realize a refrigeration cycle system 1 that can suppress heat loss of the refrigerant.

(7-2) Modification 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.

In this modified example, in restart mode, the degree of pressure reduction of the pressure reduction device 25 is first reduced, and then the compressor 21 is restarted. Furthermore, in 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 pause mode to 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, then increases the opening of the expansion valve serving as the pressure reduction device 25, and then restarts the compressor 21.

Specifically, as shown in FIG. 6 , when the second temperature or humidity condition is met in step S5 and the system transitions from pause mode to 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 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) before restarting the compressor 21 (step S8).

Note that step S7, which activates the release mechanism 15, and step S10, which activates the fan, may be performed either first or simultaneously. Furthermore, at least one of steps S7 and S10 may be omitted.

Next, the control unit 6 reduces 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.

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

In this manner, 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).

In addition, from the perspective 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.

In the refrigeration cycle apparatus 1 of this modified example, in restart mode, the control unit 6 first reduces the degree of pressure reduction in 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.

Furthermore, when the pressure difference is large, the control of this modified example (in restart mode, first reducing the degree of pressure reduction by the pressure reduction device 25 and then restarting the compressor 21) is advantageous, while when the pressure difference is small, the control of the embodiment (in restart mode, restarting the compressor 21 at a predetermined low capacity and gradually reducing the degree of pressure reduction by the pressure reduction device 25) is advantageous. Therefore, if the pressure difference is below a predetermined level and exceeds the first threshold in S6, it is preferable to first reduce the degree of pressure reduction by the pressure reduction device 25 and then restart the compressor 21 in restart mode, and if it is below the first threshold, restarting the compressor 21 at a predetermined low capacity in restart mode and gradually reducing the degree of pressure reduction by the pressure reduction device 25.

This modified example also 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 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 refrigerant heat exchange in the heat source unit 2, the utilization unit 3, or both the heat source unit 2 and the utilization unit 3. As a result, the pressure difference can be reduced before restarting the compressor 21, thereby further reducing the burden on the compressor 21.

In addition, 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 refrigerant moves for a short time. Furthermore, the heat source fan 26, the utilization fan 32, or both the heat source fan 26 and the utilization fan 32 are not operated until the pressure is equalized, but rather with the aim of reducing the pressure difference taking into account the load on the compressor 21. Therefore, the impact of heat loss is small, and heat loss can be reduced compared to conventional pressure equalization control.

(7-3) Modification 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 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 switched between the cooling operation shown in Fig. 2 and the heating operation shown in Fig. 3.

(7-4) Modification 4
In the above-described embodiment and modified example 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 modified example, the temperature of the heat source heat exchanger 24 or the utilization heat exchanger 31 immediately before entering the pause mode is used to check the differential pressure. Specifically, the control unit 6 determines the differential pressure from the condensing temperature and evaporating temperature of the main refrigerant circuit 10.

(7-5) Modification 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 may be provided, for example, in the bypass pipe 16 connecting the liquid side and the gas side of the pressure reducing device 25.

(7-6) Modification 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.

(7-7) Modification 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.

Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details may be made without departing from the spirit and scope of the present disclosure as set forth in the claims.

1: Refrigeration cycle device 6: Control unit 10: Refrigerant main circuit 11: High-pressure flow path 12: Low-pressure flow paths 13, 16: Bypass piping 14: Differential pressure detection device 15: Relief mechanism 21: Compressor 22: Backflow prevention device 24: Heat source heat exchanger 25: Pressure reduction device 26: Heat source fan 31: Utilization heat exchanger 32: Utilization fan

Japanese Patent Application Laid-Open No. 2018-128158

Claims (6)

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). 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. 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. 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. 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. 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 .