JP7630722B2 - Air Conditioning Equipment - Google Patents

Description

The present disclosure relates to an air conditioning system having a reheater and an evaporator installed indoors and a condenser installed outdoors.

Conventionally, air conditioners having a reheater and an evaporator installed indoors and a condenser installed outdoors have been known (see, for example, Patent Document 1). The air conditioner of Patent Document 1 is designed to control the dehumidification capacity of the evaporator by adjusting the amount of refrigerant flowing through the reheater and the amount of refrigerant flowing through the condenser.

JP 2011-133171 A

However, in the air conditioning system of Patent Document 1, differences in outside air temperature can cause uneven distribution of refrigerant among the heat exchangers, which can lead to liquid backflow and overheating when cooling or dehumidifying. If liquid backflow occurs, liquid compression can occur in the compressor, which can lead to compressor failure. In addition, if overheating occurs, there is an issue that the amount of refrigerant circulating between the compressor, reheater, expansion valve, and evaporator is insufficient, reducing capacity and causing the discharge temperature to rise, making it difficult to operate efficiently.

The present disclosure has been made to solve the above problems, and aims to provide an air conditioning system that can prevent imbalances in the refrigerant distributed to each heat exchanger before performing cooling or dehumidification operation.

The air-conditioning apparatus according to the present disclosure includes a main circuit in which a compressor, a first on-off valve, a reheater, a first expansion valve, and an evaporator are sequentially connected by a main pipe, a cooling circuit in which a second on-off valve, a condenser, and a second expansion valve are sequentially connected by a cooling pipe connecting between the compressor and the first on-off valve and between the first expansion valve and the evaporator, a bypass circuit having a bypass pipe connecting from a discharge side of the compressor to between the reheater and the first expansion valve and a third on-off valve for opening and closing the bypass pipe, and a refrigerant circuit in which a refrigerant circulates, and a control device for controlling the refrigerant circuit, wherein the reheater and the evaporator are disposed in an air-conditioned space, and the condenser is disposed outside the air-conditioned space, and the control device controls the first on-off valve and the second on-off valve to be in an open state and the third on-off valve to be in a closed state, and controls the first expansion valve to be in a closed state before switching the operation to a cooling operation for cooling the air in the air-conditioned space or a dehumidification operation for dehumidifying the air in the air-conditioned space. An operation switching control is implemented in which the degree of superheat on the suction side of the compressor is controlled and the degree of subcooling of the condenser is controlled using the second expansion valve, and during the cooling operation, refrigerant distribution control is implemented based on the degree of subcooling of the condenser, the condensing temperature of the condenser and an internal liquid temperature which is the temperature of the refrigerant flowing through the reheater, or the condensing temperature of the condenser or the internal liquid temperature, and when the degree of subcooling of the condenser is equal to or lower than a preset value and the condensing temperature of the condenser is not lower than a value at which high pressure protection is implemented which is a control for lowering the frequency of the compressor or stopping the compressor, or when the internal liquid temperature is not higher than the evaporation temperature of the evaporator, the first on-off valve and the second on-off valve are opened and the third on-off valve is closed, and the degree of subcooling of the reheater is controlled using the first expansion valve and the degree of supercooling on the suction side of the compressor is controlled using the second expansion valve .

According to the air conditioning device of the present disclosure, before switching the operation to the cooling operation or the dehumidification operation, the control device performs operation switching control by opening the first on-off valve and the second on-off valve, closing the third on-off valve, controlling the degree of superheat on the suction side of the compressor using the first expansion valve, and controlling the degree of subcooling of the condenser using the second expansion valve. By performing this operation switching control, the amount of refrigerant is adjusted to an appropriate value, so that it is possible to suppress the occurrence of an imbalance in the refrigerant distributed to each heat exchanger before the cooling operation or the dehumidification operation is performed.

1 is an overall configuration diagram of an air conditioning apparatus according to a first embodiment. 2 is a block diagram illustrating a schematic functional configuration of a control device illustrated in FIG. 1 . 2 is an explanatory diagram showing a state of a refrigerant circuit during a dehumidification operation of the air conditioner shown in FIG. 1. FIG. 2 is an explanatory diagram showing a state of the refrigerant circuit during intermediate operation of the air conditioning apparatus shown in FIG. 1 . 2 is an explanatory diagram showing a state of a refrigerant circuit during cooling operation of the air conditioning apparatus shown in FIG. 1. 2 is an explanatory diagram showing a state of a refrigerant circuit during a defrosting operation of the air conditioner shown in FIG. 1. 4 is a flowchart illustrating an example of operation switching control of the air conditioning apparatus shown in FIG. 1 . 4 is a flowchart illustrating a refrigerant distribution control during a cooling operation of the air conditioning apparatus shown in FIG. 1 . 4 is a flowchart illustrating a refrigerant distribution control during a dehumidification operation of the air conditioner shown in FIG. 1 . 4 is a diagram showing an example of the operation of each opening/closing valve and each expansion valve when refrigerant leaks from the air conditioning device according to embodiment 1. FIG. FIG. 11 is an overall configuration diagram of an air conditioning apparatus according to a second embodiment.

Below, an embodiment of the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited to the embodiment described below. Also, the size relationships of the components in the following drawings may differ from the actual ones.

Embodiment 1.
Fig. 1 is an overall configuration diagram of an air conditioning apparatus 100 according to embodiment 1. The air conditioning apparatus 100 according to embodiment 1 adjusts the temperature and humidity of air in an air-conditioned space such as a room. As shown in Fig. 1, the air conditioning apparatus 100 has an indoor unit 70 installed in the air-conditioned space, and an outdoor unit 80 installed outside the air-conditioned space. The indoor unit 70 and the outdoor unit 80 are connected by a refrigerant piping 20. Hereinafter, the inside of the air-conditioned space will also be referred to as the indoors, and the outside of the air-conditioned space will also be referred to as the outdoors.

The indoor unit 70 is, for example, a floor-mounted dehumidifier placed on the floor of the air-conditioned space, or a ceiling-embedded or ceiling-suspended dehumidifier installed on the ceiling. The indoor unit 70 contains a compressor 1, a first on-off valve 2, a reheater 3, a first expansion valve 4, an indoor heat exchanger 5, a second on-off valve 6, a second expansion valve 9, and a third on-off valve 10. The outdoor unit 80 is installed outdoors or in a machine room. The outdoor unit 80 contains an outdoor heat exchanger 7 and a liquid reservoir 8. That is, the air-conditioning device 100 has a refrigerant circuit 30 in which the compressor 1, the first on-off valve 2, the reheater 3, the first expansion valve 4, the indoor heat exchanger 5, the second on-off valve 6, the outdoor heat exchanger 7, the liquid reservoir 8, the second expansion valve 9, and the third on-off valve 10 are connected by a refrigerant piping 20, and the refrigerant circulates. In the following description, the indoor heat exchanger 5 is also referred to as an evaporator, and the outdoor heat exchanger 7 is also referred to as a condenser.

The refrigerant circulating through the refrigerant circuit 30 may be a single mixed refrigerant, a pseudo single mixed refrigerant, or a non-azeotropic mixed refrigerant. For example, a mixed refrigerant of R32, R125, R134a, r1234yf, and _CO2 may be used as the non-azeotropic mixed refrigerant. This non-azeotropic mixed refrigerant has a composition ratio of 49 wt% to 55 wt% of R32, 16 wt% to 22 wt% of R125, 7 wt% to 13 wt% of R134a, 6 wt% to 12 wt% of R1234yf, and 7 wt% to 13 wt% of _CO2 , totaling 100 wt%. In addition, as the non-azeotropic mixed refrigerant, R448A, R449A, R407F, or the like, which is a non-azeotropic mixed refrigerant having a composition other than the above, may be used.

The refrigerant piping 20 is composed of a main piping 21, a cooling piping 22, and a bypass piping 23. The main piping 21 is a piping that sequentially connects the compressor 1, the first on-off valve 2, the reheater 3, the first expansion valve 4, and the indoor heat exchanger 5 in a ring shape. In other words, the refrigerant circuit 30 includes a main circuit 31 formed by connecting the compressor 1, the first on-off valve 2, the reheater 3, the first expansion valve 4, and the indoor heat exchanger 5 by the main piping 21.

The cooling pipe 22 is a pipe that connects between the compressor 1 and the reheater 3 and between the first expansion valve 4 and the indoor heat exchanger 5. More specifically, the cooling pipe 22 is a pipe that connects the main pipe 21 between the compressor 1 and the first on-off valve 2 and the main pipe 21 between the first expansion valve 4 and the indoor heat exchanger 5, and connects the second on-off valve 6, the outdoor heat exchanger 7, the liquid reservoir 8, and the second expansion valve 9. In other words, the refrigerant circuit 30 includes a cooling circuit 32 that is an open circuit in which the second on-off valve 6, the outdoor heat exchanger 7, the liquid reservoir 8, and the second expansion valve 9 are connected by the cooling pipe 22. Here, the connection part between the main pipe 21 between the compressor 1 and the first on-off valve 2 and the cooling pipe 22 is referred to as the first connection part M. Also, the connection part between the main pipe 21 between the first expansion valve 4 and the indoor heat exchanger 5 and the cooling pipe 22 is referred to as the second connection part N.

The bypass piping 23 is a piping that connects the discharge side of the compressor 1 to between the reheater 3 and the first expansion valve 4. In this embodiment 1, the discharge side of the compressor 1 is between the compressor 1 and the first connection part M. More specifically, the bypass piping 23 is a piping that connects the main piping 21 between the compressor 1 and the first connection part M and the main piping 21 between the reheater 3 and the first expansion valve 4, and a third opening and closing valve 10 that opens and closes the bypass piping 23 is provided. In other words, the refrigerant circuit 30 includes a bypass circuit 33 that is an open circuit in which the third opening and closing valve 10 is provided in the bypass piping 23. Here, as shown in FIG. 1, the reheater 3 and the first expansion valve 4, and the outdoor heat exchanger 7 and the second expansion valve 9 are connected in parallel.

The compressor 1 draws in the refrigerant, compresses it, and discharges it in a high-temperature, high-pressure gas state. The compressor 1 is a compressor whose rotation speed is controlled by, for example, an inverter circuit, etc., and the amount of refrigerant discharged can be adjusted. However, the compressor 1 may also be a constant-speed compressor that operates at a constant rotation speed.

The reheater 3, the indoor heat exchanger 5, and the outdoor heat exchanger 7 are, for example, fin-and-tube type heat exchangers formed by piping through which the refrigerant flows and fins attached to the piping. The reheater 3 condenses the refrigerant by exchanging heat between the refrigerant compressed by the compressor 1 and the air. In the air conditioning device 100, the indoor heat exchanger 5 and the reheater 3 are provided on a common air duct. Then, on the same air duct, the indoor heat exchanger 5 having a dehumidifying function is arranged on the upwind side, and the reheater 3 having a heating function is arranged on the downwind side, and operation is performed by adjusting the blowing temperature, which is the temperature of the air blown out from the indoor unit 70 into the air-conditioned space. The indoor heat exchanger 5 is an air heat exchanger that functions as an evaporator (cooler) that evaporates the refrigerant. In other words, the indoor heat exchanger 5 evaporates the refrigerant by exchanging heat between the refrigerant expanded by at least one of the first expansion valve 4 and the second expansion valve 9 and the air. The outdoor heat exchanger 7 is an air heat exchanger that functions as a condenser that condenses the refrigerant. That is, the outdoor heat exchanger 7 condenses the refrigerant by exchanging heat between the refrigerant compressed by the compressor 1 and air.

The first expansion valve 4 is, for example, an electronic expansion valve, and is arranged downstream of the reheater 3. The first expansion valve 4 expands the refrigerant condensed in the reheater 3. The second expansion valve 9 is, for example, an electronic expansion valve, and is arranged downstream of the outdoor heat exchanger 7. The second expansion valve 9 expands the refrigerant condensed in the outdoor heat exchanger 7.

The first on-off valve 2, the second on-off valve 6, and the third on-off valve 10 are, for example, solenoid valves that have an open state and a closed state, and allow refrigerant to pass when in the open state. When in the closed state, the first on-off valve 2 blocks refrigerant attempting to flow to the reheater 3 via the first connection part M. When in the closed state, the second on-off valve 6 blocks refrigerant attempting to flow to the outdoor heat exchanger 7 via the first connection part M. When in the closed state, the third on-off valve 10 blocks refrigerant attempting to flow to the bypass piping 23. The liquid reservoir 8 is a member that stores excess refrigerant.

The indoor unit 70 is provided with an indoor blower 11 that blows air to the indoor heat exchanger 5 and the reheater 3. The outdoor unit 80 is provided with an outdoor blower 12 that is attached to the outdoor heat exchanger 7 and blows air to the outdoor heat exchanger 7. In this embodiment 1, the indoor blower 11 and the outdoor blower 12 are blowers whose rotation speeds are controlled, for example, by an inverter circuit or the like, and the amount of air blown can be adjusted.

Furthermore, the indoor unit 70 is provided with an indoor refrigerant leakage sensor 41, a control device 50, pressure sensors 61-63, refrigerant temperature sensors 65-68, and an air temperature sensor 91. The outdoor unit 80 is provided with an outdoor refrigerant leakage sensor 42, a pressure sensor 64, a refrigerant temperature sensor 69, and an air temperature sensor 92.

Pressure sensor 61 is provided on the suction side of compressor 1 and measures the low pressure, which is the pressure of the refrigerant sucked in by compressor 1. Pressure sensor 62 is provided on the discharge side of compressor 1 and measures the high pressure, which is the pressure of the refrigerant discharged from compressor 1. Pressure sensor 63 is provided on the outlet side of reheater 3, i.e., at or near the outlet of reheater 3, and measures the reheater outlet pressure, which is the pressure of the refrigerant flowing out from reheater 3. Pressure sensor 64 is provided on the outlet side of outdoor heat exchanger 7, i.e., at or near the outlet of outdoor heat exchanger 7, and measures the condenser outlet pressure, which is the pressure of the refrigerant flowing out from outdoor heat exchanger 7.

The refrigerant temperature sensors 65 to 69 are, for example, thermistors. The refrigerant temperature sensor 65 is provided on the suction side of the compressor 1 and measures the suction temperature, which is the temperature of the refrigerant suctioned into the compressor 1. The refrigerant temperature sensor 66 is provided on the discharge side of the compressor 1 and measures the discharge temperature, which is the temperature of the refrigerant discharged from the compressor 1. The refrigerant temperature sensor 67 is provided on the outlet side of the reheater 3 and measures the reheater outlet temperature, which is the temperature of the refrigerant flowing out from the reheater 3. The refrigerant temperature sensor 68 is provided on the outlet side of the indoor heat exchanger 5 and measures the evaporator outlet temperature, which is the temperature of the refrigerant flowing out from the indoor heat exchanger 5. The refrigerant temperature sensor 69 is provided on the outlet side of the outdoor heat exchanger 7 and measures the condenser outlet temperature, which is the temperature of the refrigerant flowing out from the outdoor heat exchanger 7.

The air temperature sensors 91 and 92 are, for example, thermistors. The air temperature sensor 91 is provided at the intake port of the indoor unit 70, and measures the temperature of the air-conditioned space as the indoor temperature. The air temperature sensor 92 is provided at the outdoor unit 80, and measures the temperature outdoors or in the machine room as the outside air temperature.

The indoor refrigerant leakage sensor 41 is provided in the air-conditioned space and detects refrigerant leakage. The outdoor refrigerant leakage sensor 42 is provided outside the air-conditioned space and detects refrigerant leakage. When the indoor refrigerant leakage sensor 41 and the outdoor refrigerant leakage sensor 42 detect a refrigerant leakage, they output a leakage signal indicating the occurrence of a refrigerant leakage to the control device 50. Each pressure sensor outputs measured pressure data to the control device 50. Each temperature sensor outputs measured temperature data to the control device 50. That is, each refrigerant leakage sensor, each pressure sensor, and each temperature sensor are electrically or optically connected to the control device 50.

The indoor unit 70 is also provided with an abnormality alarm 45 that includes at least one of a speaker and a light emitter. An LED (light emitting diode) or the like can be used as the light emitter. The abnormality alarm 45 outputs sound, voice, light, or the like in response to an instruction from the control device 50 to notify the occurrence of an abnormality.

The control device 50 controls the refrigerant circuit 30. That is, the control device 50 acquires the output of each pressure sensor and each temperature sensor, and controls various actuators such as the compressor 1, the first on-off valve 2, the first expansion valve 4, the second on-off valve 6, the second expansion valve 9, and the third on-off valve 10. Furthermore, the control device 50 causes the abnormality alarm 45 to notify the occurrence of an abnormality when an abnormality occurs. The control device 50 according to the first embodiment causes the abnormality alarm 45 to output sound, voice, light, or the like when the refrigerant leakage sensors detect an abnormality in refrigerant leakage.

The control device 50 is configured to include, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory). The RAM is a volatile storage medium that stores various data. The ROM is a non-volatile storage medium that stores operation programs and the like for causing the control device 50 to execute operation control in each operation mode described below. The control device 50 appropriately controls the compressor 1, the first opening and closing valve 2, the first expansion valve 4, the second opening and closing valve 6, the second expansion valve 9, and the third opening and closing valve 10, etc., according to the operation program in the ROM, and performs air conditioning in each operation mode. In other words, the control device 50 can be configured by a calculation device such as a CPU and an operation program that cooperates with the calculation device to realize the following various functions.

Here, the flow of air in the indoor unit 70 will be briefly described. When the indoor blower 11 operates, air is taken into the indoor unit 70. The air taken into the indoor unit 70 passes through the indoor heat exchanger 5, which functions as an evaporator, and the absolute humidity decreases. In other words, when the air containing moisture passes through the indoor heat exchanger 5, the moisture in the air condenses on the indoor heat exchanger 5, and the absolute humidity of the air decreases. The air that has a lower absolute humidity and a lower temperature by passing through the indoor heat exchanger 5 becomes cold air with a high relative humidity. The air that has passed through the indoor heat exchanger 5 is reheated by passing through the reheater 3, and the relative humidity decreases. Then, the air that has passed through the reheater 3 and has a lowered relative humidity is blown out into the room. As described above, the air taken into the indoor unit 70 is blown out into the room with a lowered relative humidity, and therefore the relative humidity in the room decreases. This is the flow of air in the indoor unit 70 during dehumidification operation or intermediate operation, which will be described later.

Figure 2 is a block diagram showing a schematic functional configuration of the control device 50 shown in Figure 1. The control device 50 has an arithmetic processing unit 51 and a memory unit 52. The arithmetic processing unit 51 has a setting processing unit 51a, an operation control unit 51b, an excess refrigerant detection unit 51c, and a leakage processing unit 51d. The setting processing unit 51a receives an operation signal indicating the contents of the user's operation and settings from a remote controller (not shown) for operating the air conditioning device 100, etc. Then, the setting processing unit 51a sets the operation mode, target temperature, target humidity, etc. in response to the operation signal.

The surplus refrigerant detection unit 51c detects the occurrence of surplus refrigerant by any of the following methods, and outputs a detection signal to the operation control unit 51b when it detects the occurrence of surplus refrigerant. For example, the surplus refrigerant detection unit 51c can be configured to calculate the degree of supercooling and determine whether the calculated degree of supercooling is greater than a subcooling threshold. This determination makes use of the fact that the degree of supercooling increases when surplus refrigerant occurs. In other words, the surplus refrigerant detection unit 51c outputs a detection signal to the operation control unit 51b when the calculated degree of supercooling is greater than the subcooling threshold.

In addition, the detection of surplus refrigerant may utilize the fact that the discharge temperature of the refrigerant is low when surplus refrigerant occurs. In other words, the surplus refrigerant detection unit 51c may obtain the discharge temperature from the refrigerant temperature sensor 66 and determine whether the obtained discharge temperature is lower than the discharge threshold. Then, the surplus refrigerant detection unit 51c may output a detection signal to the operation control unit 51b when the discharge temperature is lower than the discharge threshold.

Furthermore, the detection of surplus refrigerant may utilize the fact that the high-pressure pressure increases when surplus refrigerant occurs. That is, the surplus refrigerant detection unit 51c may acquire the high-pressure pressure from the pressure sensor 62 and determine whether the acquired high-pressure pressure is greater than a high-pressure threshold. Then, the surplus refrigerant detection unit 51c may output a detection signal to the operation control unit 51b when the high-pressure pressure is greater than the high-pressure threshold.

In addition, the detection of surplus refrigerant may utilize the fact that the low-pressure pressure increases when surplus refrigerant occurs. That is, the surplus refrigerant detection unit 51c may obtain the low-pressure pressure from the pressure sensor 61 and determine whether the obtained low-pressure pressure is greater than a low-pressure threshold. Then, the surplus refrigerant detection unit 51c may output a detection signal to the operation control unit 51b when the low-pressure pressure is greater than the low-pressure threshold.

The leakage processing unit 51d acquires leakage signals from the indoor refrigerant leakage sensor 41 and the outdoor refrigerant leakage sensor 42. When a leakage signal is output from the indoor refrigerant leakage sensor 41, the leakage processing unit 51d outputs an indoor leakage signal indicating the occurrence of a refrigerant leakage indoors to the operation control unit 51b. When a leakage signal is output from the outdoor refrigerant leakage sensor 42, the leakage processing unit 51d outputs an outdoor leakage signal indicating the occurrence of a refrigerant leakage outdoors to the operation control unit 51b.

Furthermore, the leakage processing unit 51d causes the abnormality alarm 45 to output a sound, voice, light, or the like when a leakage signal is output from at least one of the indoor refrigerant leakage sensor 41 and the outdoor refrigerant leakage sensor 42. The leakage processing unit 51d may cause the abnormality alarm 45 to output a different sound, voice, light, or the like when a leakage signal is acquired from the indoor refrigerant leakage sensor 41 and when a leakage signal is acquired from the outdoor refrigerant leakage sensor 42.

The operation control unit 51b periodically acquires measurement data from each pressure sensor and each temperature sensor. The operation control unit 51b then uses the acquired measurement data to control the operation of each actuator of the air conditioning device 100 according to the settings made by the setting processing unit 51a. The operation control unit 51b controls, for example, the rotation speeds of the compressor motor 1a of the compressor 1, the fan motor 11a of the indoor blower 11, and the fan motor 12a of the outdoor blower 12.

When the operation mode is set to the dehumidification operation mode by user operation or default setting, the operation control unit 51b causes the air conditioning device 100 to perform a dehumidification operation to dehumidify the air in the air-conditioned space. When the operation mode is set to the intermediate operation mode, the operation control unit 51b causes the air conditioning device 100 to perform an intermediate operation to simultaneously dehumidify and cool the air in the air-conditioned space. When the operation mode is set to the cooling operation mode, the operation control unit 51b causes the air conditioning device 100 to perform a cooling operation to cool the air in the air-conditioned space. When the operation mode is set to the defrost operation mode, the operation control unit 51b causes the air conditioning device 100 to perform a defrost operation to melt the frost adhering to the indoor heat exchanger 5.

For example, the operation control unit 51b closes the second opening/closing valve 6 during dehumidification operation. The operation control unit 51b may also fully close the second expansion valve 9 during dehumidification operation. In this way, it is possible to prevent refrigerant from flowing from the cooling circuit 32 into the main circuit 31. The operation control unit 51b also closes the first opening/closing valve 2 during cooling operation. The operation control unit 51b may also fully close the first expansion valve 4 during cooling operation. In this way, it is possible to prevent refrigerant remaining in the reheater 3 or the like from flowing into the indoor heat exchanger 5.

Furthermore, when excess refrigerant occurs, the operation control unit 51b causes the air conditioning device 100 to execute a refrigerant amount adjustment operation, which will be described later. That is, when a detection signal is output from the excess refrigerant detection unit 51c, the operation control unit 51b performs refrigerant amount adjustment control to store the excess refrigerant in the liquid reservoir 8 while maintaining the performance of the reheater 3. Furthermore, when the refrigerant does not move due to the pressure difference between the outside and inside of the room, the operation control unit 51b performs refrigerant amount adjustment control according to each situation.

Furthermore, when the indoor refrigerant leakage sensor 41 detects a refrigerant leakage, that is, when an indoor leakage signal is output from the leakage processing unit 51d, the operation control unit 51b closes the first opening/closing valve 2 and fully closes the second expansion valve 9. This blocks the refrigerant flowing from the first connection part M to the reheater 3, and the indoor refrigerant can be stored in the outdoor heat exchanger 7 and the liquid reservoir 8 via the second opening/closing valve 6, thereby suppressing the leakage of refrigerant into the room. The operation control unit 51b may also fully close the first expansion valve 4 when a refrigerant leakage is detected by the indoor refrigerant leakage sensor 41. In this way, it is possible to prevent the refrigerant remaining in the reheater 3, etc. from flowing into the indoor heat exchanger 5. Therefore, when the refrigerant leakage point is present in the flow path from the second connection part N through the indoor heat exchanger 5 and the compressor 1 to the first connection part M, further refrigerant leakage into the room can be suppressed. In addition, when a refrigerant leak is detected by the indoor refrigerant leak sensor 41, the operation control unit 51b may fully close the first on-off valve 2 and the first expansion valve 4, and isolate the section of the refrigerant circuit 30 from the first on-off valve 2 to the first expansion valve 4, thereby facilitating the process of identifying the location of the refrigerant leak.

In addition, when the outdoor refrigerant leakage sensor 42 detects a refrigerant leakage, that is, when an outdoor leakage signal is output from the leakage processing unit 51d, the operation control unit 51b closes the second opening/closing valve 6 and fully closes the first expansion valve 4. This blocks the flow of refrigerant to the outside and allows the outdoor refrigerant to be stored in the indoor heat exchanger 5, thereby suppressing outdoor refrigerant leakage. In addition, when the outdoor refrigerant leakage sensor 42 detects a refrigerant leakage, the operation control unit 51b may fully close the second opening/closing valve 6 and the second expansion valve 9, and separate the portion of the refrigerant circuit 30 from the second opening/closing valve 6 to the second expansion valve 9, thereby facilitating the process of identifying the refrigerant leakage location.

The memory unit 52 stores the operating program of the control device 50. The memory unit 52 also stores various data related to air conditioning control. For example, the memory unit 52 stores data on settings such as the operation mode, target temperature, and target humidity. The memory unit 52 also stores information on thresholds that serve as criteria for detecting the occurrence of excess refrigerant, such as the subcooling threshold, discharge threshold, high pressure threshold, and low pressure threshold. The subcooling threshold, discharge threshold, high pressure threshold, and low pressure threshold are preset and can be changed as appropriate.

Figure 3 is an explanatory diagram showing the state of the refrigerant circuit 30 during dehumidification operation of the air conditioning apparatus 100 shown in Figure 1. Figure 4 is an explanatory diagram showing the state of the refrigerant circuit 30 during intermediate operation of the air conditioning apparatus 100 shown in Figure 1. Figure 5 is an explanatory diagram showing the state of the refrigerant circuit 30 during cooling operation of the air conditioning apparatus 100 shown in Figure 1. Figure 6 is an explanatory diagram showing the state of the refrigerant circuit 30 during defrost operation of the air conditioning apparatus 100 shown in Figure 1. In Figures 3 to 6, the open/close valves are shown in white, and the closed/close valves are shown in black. In addition, in Figures 3 to 6, the flow of refrigerant is shown by a dashed line with an arrow. Valve control and refrigerant flow in each operation mode will be described with reference to Figures 3 to 6.

[Dehumidification operation]
3, during the dehumidification operation, the second on-off valve 6 and the third on-off valve 10 are closed, and the first on-off valve 2 is open. In other words, when the control device 50 is set to the dehumidification operation mode, it opens the first on-off valve 2 and closes the second on-off valve 6 and the third on-off valve 10.

Therefore, the high-temperature, high-pressure gas refrigerant discharged from the compressor 1 flows into the reheater 3 through the discharge piping (piping between the compressor 1 and the outdoor heat exchanger 7). Here, the indoor air blown by the indoor blower 11 and passing through the indoor heat exchanger 5 passes through the reheater 3. Therefore, the high-temperature, high-pressure gas refrigerant that flows into the reheater 3 exchanges heat with the indoor air passing through the reheater 3, releases heat, and condenses and liquefies. Then, the refrigerant that flows out of the reheater 3 passes through the liquid piping (piping between the reheater 3 and the first expansion valve 4), is depressurized by the first expansion valve 4, and flows into the indoor heat exchanger 5 as a two-phase gas-liquid refrigerant. The two-phase gas-liquid refrigerant that flows into the indoor heat exchanger 5 absorbs heat and gasifies through heat exchange with the indoor air blown by the indoor blower 11, and returns to the compressor 1 as a low-temperature, low-pressure gas refrigerant.

Here, the air circulated through the indoor unit 70 by the indoor blower 11 is cooled by the low-temperature, low-pressure, gas-liquid two-phase refrigerant flowing through the indoor heat exchanger 5, and its temperature drops to below the dew point. This causes moisture in the indoor air to condense on the surface of the indoor heat exchanger 5, dehumidifying the indoor air. The air that has passed through the indoor heat exchanger 5 is then heated by the high-temperature, high-pressure gas refrigerant in the reheater 3, raising its temperature and reducing its relative humidity.

In this way, the air conditioning device 100 dissipates all of the heat in the refrigeration cycle indoors by closing the second on-off valve 6 during dehumidification operation. In other words, the air conditioning device 100 operates to heat the indoor air by the amount of heat added to the refrigerant by the compressor 1 and the latent heat of condensation of water vapor in the air. Therefore, indoor air drawn into the air conditioning device 100 during dehumidification operation is heated and dehumidified at the same time.

[Intermediate operation]
4, during intermediate operation in which the air in the air-conditioned space is dehumidified and cooled simultaneously, the first on-off valve 2 and the second on-off valve 6 are open, and the third on-off valve 10 is closed. In other words, when the control device 50 is set to the intermediate operation mode, it opens the first on-off valve 2 and the second on-off valve 6, and closes the third on-off valve 10.

Therefore, the high-temperature, high-pressure gas refrigerant discharged from the compressor 1 flows into the outdoor heat exchanger 7 and the reheater 3 through the discharge piping. The refrigerant that dissipates heat and is liquefied in the outdoor heat exchanger 7 and the reheater 3 is decompressed by the second expansion valve 9 and the first expansion valve 4 installed downstream of the liquid piping (the piping between the outdoor heat exchanger 7 and the second expansion valve 9 and the piping between the reheater 3 and the first expansion valve 4) to become a gas-liquid two-phase refrigerant, and after merging at the second connection part N, flows into the indoor heat exchanger 5. The gas-liquid two-phase refrigerant that flows into the indoor heat exchanger 5 absorbs heat and gasifies in the indoor heat exchanger 5, and is sucked into the compressor 1 through the suction piping (the piping between the indoor heat exchanger 5 and the compressor 1). In intermediate operation, the control device 50 performs on/off control of the outdoor blower 12 according to the outdoor temperature and the high pressure, and controls the indoor blower 11 to be always on. During intermediate operation when adjusting the amount of refrigerant, the fan speed is controlled according to the internal liquid SC and the external liquid SC. Here, the internal liquid SC refers to the degree of subcooling of the reheater 3, and the external liquid SC refers to the degree of subcooling of the outdoor heat exchanger 7.

[Cooling operation]
5, during cooling operation for cooling the air in the air-conditioned space, the second on-off valve 6 is open, and the first on-off valve 2 and the third on-off valve 10 are closed. In other words, when the control device 50 is set to the cooling operation mode, it opens the second on-off valve 6 and closes the first on-off valve 2 and the third on-off valve 10.

Therefore, the high-temperature, high-pressure gas refrigerant discharged from the compressor 1 flows into the outdoor heat exchanger 7 through the discharge piping, exchanges heat with the outdoor air blown by the outdoor blower 12, releases heat, and condenses and liquefies. The refrigerant flowing out from the outdoor heat exchanger 7 passes through the liquid piping (piping between the outdoor heat exchanger 7 and the second expansion valve 9) and is depressurized by the second expansion valve 9 to become a two-phase gas-liquid refrigerant, which then flows into the indoor heat exchanger 5. The two-phase gas-liquid refrigerant that flows into the indoor heat exchanger 5 exchanges heat with the indoor air blown by the indoor blower 11, absorbs heat, and gasifies, becoming a low-temperature, low-pressure gas refrigerant and returning to the compressor 1. In other words, the air circulated by the indoor blower 11 is cooled by the low-temperature, low-pressure two-phase gas-liquid refrigerant in the indoor heat exchanger 5. The surplus refrigerant during cooling operation is appropriately stored in the liquid reservoir 8.

Here, cooling operation should be performed when the absolute humidity in the room is low or when lowering the indoor temperature is a high priority. This is because when the air temperature drops due to cooling operation, the relative humidity increases. And when the relative humidity increases, not only does it reduce comfort, but it also causes inconveniences such as the room becoming more susceptible to condensation. Also, for example, when the air temperature drops below the dew point due to cooling operation, the moisture in the indoor air condenses on the surface of the indoor heat exchanger 5, increasing ventilation resistance and reducing heat exchange capacity.

[Defrosting operation]
The defrosting operation is a defrosting operation carried out when frost forms on the indoor heat exchanger 5 and its performance as a heat exchanger is reduced. As shown in Fig. 6, during the defrosting operation, the first on-off valve 2 and the second on-off valve 6 are closed, and the third on-off valve 10 is open. In other words, when the control device 50 is set to the defrosting operation mode, it closes the first on-off valve 2 and the second on-off valve 6 and opens the third on-off valve 10. Therefore, the high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the discharge piping and the bypass circuit 33, is decompressed by the first expansion valve 4, and flows into the indoor heat exchanger 5.

Here, the indoor heat exchanger 5 is heated by the refrigerant and exchanges heat with the frost to melt the frost. The refrigerant that flows into the indoor heat exchanger 5 is cooled by heat exchange with the frost, and then exchanges heat with the suction pipe to absorb heat and gasify, becoming a low-temperature, low-pressure gas refrigerant that returns to the compressor 1. At this time, the control device 50 adjusts the amount of refrigerant passing through the indoor heat exchanger 5 by opening the first expansion valve 4 to the minimum degree, thereby preventing the liquefied refrigerant from entering the compressor 1. The control device 50 also turns off the indoor blower 11. Therefore, during defrosting operation, heat exchange is simply performed between the refrigerant passing through the indoor heat exchanger 5 and the frost that has adhered to the indoor heat exchanger 5.

Of the above operations, the intermediate operation shown in FIG. 4 requires a relatively large amount of refrigerant because it flows through the reheater 3 and the outdoor heat exchanger 7. On the other hand, the dehumidification operation shown in FIG. 3 requires a smaller amount of refrigerant than the intermediate operation. This is because in the dehumidification operation, refrigerant flows through the reheater 3 but does not flow through the outdoor heat exchanger 7. Therefore, when the dehumidification operation is performed, surplus refrigerant may be generated. If surplus refrigerant is generated, there is a risk of abnormalities such as an increase in high-pressure. In addition, when there is a large temperature difference between the outside and inside of the room, there is a risk of surplus refrigerant being generated in the cooling operation and dehumidification operation due to refrigerant imbalance.

Therefore, the air conditioning apparatus 100 according to the first embodiment performs operation switching control for the purpose of refrigerant leveling before switching to cooling operation or dehumidification operation. In addition, after switching to each operation, it performs refrigerant distribution control based on the state values during operation. First, we will explain the operation switching control performed by the operation control unit 51b before switching to cooling operation or dehumidification operation.

[Operation switching control]
FIG. 7 is a flowchart illustrating an example of operation switching control of the air conditioning apparatus 100 shown in FIG.

The operation control unit 51b performs operation switching control for the purpose of leveling the refrigerant when switching to cooling operation or dehumidification operation. An example of the timing for performing operation switching control is the timing of transition from cooling operation to dehumidification operation or from dehumidification operation to cooling operation. In other words, when performing cooling operation, the room cools but the relative humidity increases, so a trigger to switch to dehumidification operation occurs when a certain humidity is exceeded, and conversely, when performing dehumidification operation, the relative humidity decreases but the room temperature increases, so a trigger to switch to cooling operation occurs when a certain temperature is exceeded, so operation switching control is performed according to that trigger.

The operation control unit 51b executes the intermediate operation shown in FIG. 4, opening both the first on-off valve 2 and the second on-off valve 6, and closing the third on-off valve 10 (step S101). The operation control unit 51b then performs operation switching control using the first expansion valve 4 provided downstream of the reheater 3 and the second expansion valve 9 provided downstream of the outdoor heat exchanger 7. In the operation switching control, the operation control unit 51b performs, for example, SH control with the first expansion valve 4 and internal liquid SC control with the second expansion valve 9.

The operation control unit 51b uses the second expansion valve 9 provided downstream of the outdoor heat exchanger 7 to control the SC (degree of subcooling) of the refrigerant condensed in the outdoor heat exchanger 7, thereby making the amount of refrigerant distributed to the outdoor heat exchanger 7 appropriate. In addition, the operation control unit 51b uses the first expansion valve 4 provided downstream of the reheater 3 to control the SH (degree of superheat) of the refrigerant that evaporates in the indoor heat exchanger 5 and flows out, thereby preventing liquid backflow due to excess refrigerant and storing the refrigerant in the reheater 3 and the outdoor heat exchanger 7.

When the external liquid SC and suction SH satisfy the judgment value or the operation time has elapsed for a predetermined time, the operation control unit 51b ends the operation switching control and transitions to cooling operation or dehumidification operation. Specifically, when the external liquid SC ≒ 5K and suction SH ≒ 5K are satisfied (YES in step S102), or when the operation time has elapsed for 5 minutes (YES in step S103), the operation control unit 51b ends the operation switching control and transitions to cooling operation or dehumidification operation (step S104). At this time, the judgment value of the external liquid SC and suction SH for step S102 is 5K, but a width of ±α may be given. In other words, the external liquid SC and suction SH do not have to completely match the judgment value of 5K, and the condition is also satisfied when 5-αK ≦ external liquid SC and SH ≦ 5 + αK. Here, suction SH refers to the degree of superheat on the suction side of the compressor 1. With regard to step S103, although operation switching control can standardize the refrigerant, it results in incomplete operation, so it is not desirable to perform this for too long. Since it can be considered that a certain degree of leveling has been achieved after five minutes has elapsed, it is determined whether the operation time has elapsed for five minutes.

Figure 8 is a flowchart illustrating the refrigerant distribution control during cooling operation of the air conditioning device 100 shown in Figure 1. Next, we will explain the refrigerant distribution control performed based on the state values during operation after transitioning to each operation.

Refrigerant distribution control is performed when the aforementioned operation switching control is executed and the operation mode is switched to cooling operation or dehumidification operation, and is determined from the state values during operation.

[Refrigerant distribution control during cooling operation]
The operation control unit 51b determines whether the amount of refrigerant in the cooling operation is excessive or insufficient using the external liquid SC (step S201).

(When external liquid SC≦5K (refrigerant shortage))
When the external liquid SC≦5K (NO in step S201), the operation control unit 51b judges that there is a refrigerant shortage and moves to the next judgment formula. In the next judgment formula, it is judged whether the outdoor condensing temperature CTout, which is the condensing temperature of the outdoor heat exchanger 7, is lower than the value CTout_max-5K at which high pressure protection control, which is a control to lower the frequency of the compressor 1 or stop the compressor 1, is performed, and the internal liquid temperature, which is the temperature of the refrigerant flowing through the reheater 3, is higher than the evaporation temperature ET, which is the evaporation temperature of the indoor heat exchanger 5, is satisfied (step S209). The judgment formula for the outdoor condensing temperature CTout is intended to prevent high pressure abnormality when the refrigerant distribution is increased toward the outdoor side, and the judgment formula for the evaporation temperature ET is intended to judge whether or not the refrigerant can be discharged due to the pressure difference when the refrigerant is discharged from the indoor side, which will be described next. When the operation control unit 51b judges that the above judgment formula is not satisfied and that it is difficult to discharge the refrigerant from the indoor side (NO in step S209), it performs further refrigerant amount adjustment operation by intermediate operation (step S213). This is to forcibly circulate the refrigerant that has become difficult to discharge from the indoor side due to the pressure difference, so that it becomes the intended external liquid SC.

In this intermediate operation, the second expansion valve 9 is subjected to SH control, and the first expansion valve 4 is subjected to internal liquid SC control. In addition, the rotation speed of the outdoor blower 12 is reduced, and the external liquid SC is increased. This is intended to facilitate the accumulation of refrigerant in the liquid reservoir 8 and the outdoor heat exchanger 7 by controlling the internal liquid SC with the first expansion valve 4, which opens the first expansion valve 4 and discharges the refrigerant accumulated in the reheater 3, and to forcibly circulate refrigerant that could not be discharged due to the pressure difference by controlling the SH with the second expansion valve 9. If the operation control unit 51b determines that the external liquid SC ≈ 5K is reached (YES in step S214), it ends this control (step S215).

If the operation control unit 51b determines that the above judgment formula is satisfied and that the refrigerant can be discharged from the indoor side (YES in step S209), it changes the control target of the first expansion valve 4 to external liquid SC ≒ 5K (step S210) and controls the first expansion valve 4 to open from the closed state to the minimum opening so that the external liquid SC ≒ 5K. Then, if the operation control unit 51b determines that the external liquid SC ≒ 5K is satisfied (YES in step S211), it fully closes the first expansion valve 4 and ends this control (step S212). Note that by not executing this control for a certain period of time after implementing this control, deterioration caused by frequently adjusting the opening of the first expansion valve 4 from fully closed is prevented, and deterioration of reliability is prevented.

(When external liquid SC>5K (excess refrigerant))
When the external liquid SC>5K (YES in step S201), the operation control unit 51b determines that there is an excess of refrigerant and proceeds to the next judgment formula. In the next judgment formula, it is determined whether the outdoor condensation temperature CTout is higher than the internal liquid temperature (step S202). This is to determine whether or not the refrigerant can be discharged due to the pressure difference when discharging the refrigerant from the outdoor side, which will be described next. When the operation control unit 51b determines that the above judgment formula is not satisfied and that it is difficult to discharge the refrigerant from the indoor side (NO in step S202), it performs further refrigerant amount adjustment operation by intermediate operation (step S206). This is to forcibly circulate the refrigerant that has become difficult to discharge due to the pressure difference, so that the intended external liquid SC is obtained.

In intermediate operation at this time, external liquid SC control is performed by the second expansion valve 9, and SH control is performed by the first expansion valve 4. In addition, the rotation speed of the indoor blower 11 is reduced and the internal liquid SC is increased. The purpose of this is to make it easier to accumulate refrigerant in the reheater 3 by controlling the external liquid SC by the second expansion valve 9, and to forcibly circulate refrigerant that cannot be discharged due to the pressure difference by controlling the SH by the first expansion valve 4. If the operation control unit 51b determines that the external liquid SC ≒ 5K is reached (YES in step S207), it ends this control (step S208).

When the operation control unit 51b determines that the above judgment formula is satisfied and that the refrigerant can be discharged from the indoor side (YES in step S202), it opens the first opening/closing valve 2 (step S203). This is intended to store the refrigerant in the reheater 3. Then, the operation control unit 51b controls the first expansion valve 4 to open from the closed state to the minimum opening degree so that the external liquid SC ≒ 5K. Then, when the operation control unit 51b determines that the external liquid SC ≒ 5K is satisfied (YES in step S204), it fully closes the first opening/closing valve 2 and ends this control (step S205). Note that by not executing this control for a certain period of time after implementing this control, deterioration due to frequent opening and closing of the first opening/closing valve 2 is prevented, and deterioration of reliability is prevented.

[Refrigerant distribution control during dehumidification operation]
FIG. 9 is a flowchart illustrating refrigerant distribution control during dehumidification operation of the air conditioning apparatus 100 shown in FIG.

The operation control unit 51b determines whether the amount of refrigerant is excessive or insufficient during dehumidification operation using the internal liquid SC (step S301).

(When internal liquid SC < 5K (refrigerant shortage))
When the internal liquid SC<5K (NO in step S301), the operation control unit 51b judges that there is a refrigerant shortage, and proceeds to the next judgment formula. In the next judgment formula, it is judged whether the indoor condensing temperature CTin, which is the condensing temperature of the reheater 3, is lower than the value CTin_max-5K at which the high pressure protection control is performed, and the external liquid temperature, which is the temperature of the refrigerant flowing through the outdoor heat exchanger 7, is higher than the evaporation temperature ET (step S309). The judgment formula for the indoor condensing temperature CTin is intended to prevent a high pressure abnormality when the refrigerant distribution is increased toward the indoor side, and the judgment formula for the evaporation temperature ET is intended to judge whether or not the refrigerant can be discharged due to the pressure difference when discharging the refrigerant from the outdoor side, which will be described next. When the operation control unit 51b judges that the refrigerant is difficult to discharge from the outdoor side because the above judgment formula is not satisfied (NO in step S309), it performs further refrigerant amount adjustment operation by intermediate operation (step S313). This is intended to forcibly circulate the refrigerant that has become difficult to discharge due to the pressure difference, so that the intended internal liquid SC is obtained.

In intermediate operation at this time, external liquid SC control is performed by the second expansion valve 9, and SH control is performed by the first expansion valve 4. At this time, the rotation speed of the indoor blower 11 is reduced, and the internal liquid SC is increased. This is intended to facilitate the circulation of more refrigerant to the reheater 3 by controlling the external liquid SC by the second expansion valve 9, thereby discharging the refrigerant accumulated in the outdoor heat exchanger 7, and to forcibly circulate refrigerant that could not be discharged due to the pressure difference by controlling the SH by the first expansion valve 4. If the operation control unit 51b determines that the internal liquid SC ≈ 5K is reached (YES in step S314), it ends this control (step S315).

If the operation control unit 51b determines that the above judgment formula is satisfied and that the refrigerant can be discharged from the outdoor side (YES in step S309), it changes the control target of the second expansion valve 9 to internal liquid SC ≒ 5K (step S310) and controls the second expansion valve 9 to open from the closed state to the minimum opening so that the internal liquid SC ≒ 5K. Then, if the operation control unit 51b determines that the internal liquid SC ≒ 5K is satisfied (YES in step S311), it fully closes the second expansion valve 9 and ends this control (step S312). Note that by not executing this control for a certain period of time after implementing this control, deterioration of the second expansion valve 9 due to frequent adjustment of the opening from fully closed is prevented, and deterioration of reliability is prevented.

(When internal liquid SC>5K (excess refrigerant))
When the internal liquid SC>5K (YES in step S301), the operation control unit 51b determines that there is an excess of refrigerant and proceeds to the next judgment formula. In the next judgment formula, it is determined whether the indoor condensation temperature CTin is higher than the external liquid temperature (step S302). This is to determine whether or not the refrigerant can be discharged due to the pressure difference when discharging the refrigerant from the outdoor side, which will be described next. When the operation control unit 51b determines that the above judgment formula is not satisfied and that it is difficult to discharge the refrigerant from the outdoor side (NO in step S302), it performs further refrigerant amount adjustment operation by intermediate operation (step S306). This is to forcibly circulate the refrigerant that has become difficult to discharge due to the pressure difference, so that the intended internal liquid SC is obtained.

In the intermediate operation at this time, the second expansion valve 9 performs SH control and the first expansion valve 4 performs internal liquid SC control. At this time, the rotation speed of the indoor blower 11 is increased to reduce the internal liquid SC. In addition, the rotation speed of the outdoor blower 12 is decreased to increase the external liquid SC. This is intended to facilitate the accumulation of refrigerant in the liquid reservoir 8 and the outdoor heat exchanger 7 by controlling the internal liquid SC with the first expansion valve 4, and to forcibly circulate refrigerant that cannot be discharged due to the pressure difference by controlling the internal liquid SC with the first expansion valve 4 (YES in step S307).

When the operation control unit 51b determines that the above judgment formula is satisfied and that the refrigerant can be discharged from the outdoor side (YES in step S302), it opens the second opening/closing valve 6 (step S303). This is intended to store the refrigerant in the outdoor heat exchanger 7. Then, the operation control unit 51b controls the second expansion valve 9 to open from the closed state to the minimum opening degree so that the internal liquid SC ≒ 5K. Then, when the operation control unit 51b determines that the internal liquid SC ≒ 5K is filled (YES in step S304), it fully closes the second opening/closing valve 6 and ends this control (step S305). Note that by not executing this control for a certain period of time after implementing this control, deterioration due to frequent opening and closing of the second opening/closing valve 6 is prevented, and deterioration of reliability is prevented.

For both refrigerant distribution control during cooling operation and refrigerant distribution control during dehumidification operation, a range is set for the target SC judgment value at the end, and it is not necessary for it to be a perfect match. In other words, for steps S204, S207, S211, S214, S304, S307, S311, and S314, the judgment value for external liquid SC or internal liquid SC is 5K, but a range of ±α may be set. In other words, the external liquid SC or internal liquid SC does not have to be a perfect match with the judgment value of 5K, and the condition is also satisfied if 5-αK≦external liquid SC or internal liquid SC≦5+αK.

In addition, in steps S204, S207, S211, S214, and steps S304, S307, S311, and S314, if a preset time has elapsed, the process may proceed to YES even if the conditions are not met.

The operation control unit 51b according to the first embodiment adjusts the amount of refrigerant to an appropriate value by the operation switching control and refrigerant distribution control described above. Therefore, in the dehumidification operation, the reheat amount of the reheater 3 required during the dehumidification operation is secured, and the necessary and sufficient dehumidification capacity can be exhibited, and in the cooling operation, the condensation amount of the outdoor heat exchanger 7 required during the cooling operation is secured, and the necessary and sufficient cooling capacity can be exhibited. Even in a situation where it is determined that it is difficult to discharge the refrigerant from the outside or inside of the room due to the pressure difference, the state can be transitioned to the intended refrigeration cycle by forcibly circulating the refrigerant in the intermediate operation, and ideal cooling capacity can be exhibited.

More specifically, during operation switching control, the operation control unit 51b controls the opening degree of the second expansion valve 9, for example, using the temperature of the refrigerant at the outlet of the outdoor heat exchanger 7. That is, the operation control unit 51b uses the outdoor heat exchanger outlet temperature measured by the refrigerant temperature sensor 69 to determine the degree of subcooling of the outdoor heat exchanger 7. When determining the degree of subcooling of the outdoor heat exchanger 7, the operation control unit 51b acquires the high-pressure pressure from the pressure sensor 62 and the outdoor heat exchanger outlet temperature measured by the refrigerant temperature sensor 69. Then, the operation control unit 51b converts the high-pressure pressure to saturation to obtain the condensing temperature, and subtracts the outdoor heat exchanger outlet temperature from the condensing temperature to obtain the degree of subcooling of the outdoor heat exchanger 7. Then, the operation control unit 51b controls the second expansion valve 9 according to the obtained degree of subcooling. This adjusts the amount of refrigerant distributed to the outdoor heat exchanger 7. Note that the condensing temperature may be a value converted to saturation from the pressure sensor 64.

In addition, the operation control unit 51b performs SH control of the first expansion valve 4 so as to maintain the degree of superheat by the reheater 3 at or above the judgment value. As a result, excess refrigerant is stored in the liquid reservoir 8, and liquid backflow to the compressor 1 is suppressed. In this embodiment 1, when determining the degree of superheat of the indoor heat exchanger 5, the operation control unit 51b obtains the low pressure from the pressure sensor 61 and the suction temperature from the refrigerant temperature sensor 65. The operation control unit 51b then obtains the evaporation temperature ET by converting the low pressure to saturation, and obtains the degree of superheat of the indoor heat exchanger 5 by subtracting the evaporation temperature ET from the suction temperature. However, a refrigerant temperature sensor (not shown) may be provided in the middle of the indoor heat exchanger 5, and the temperature measured by the refrigerant temperature sensor may be used as the evaporation temperature ET.

During refrigerant distribution control during cooling operation, the operation control unit 51b controls the opening degree of the second expansion valve 9, for example, using the temperature of the refrigerant at the outlet of the outdoor heat exchanger 7. That is, the operation control unit 51b uses the outdoor heat exchanger outlet temperature measured by the refrigerant temperature sensor 69 to determine the degree of subcooling of the outdoor heat exchanger 7. When determining the degree of subcooling of the outdoor heat exchanger 7, the operation control unit 51b acquires the high-pressure pressure from the pressure sensor 62 and the outdoor heat exchanger outlet temperature from the refrigerant temperature sensor 69. Then, the operation control unit 51b converts the high-pressure pressure to saturation to obtain the condensation temperature, and subtracts the outdoor heat exchanger outlet temperature from the condensation temperature to obtain the degree of subcooling of the outdoor heat exchanger 7. Then, the operation control unit 51b controls the second expansion valve 9 according to the obtained degree of subcooling, and adjusts the amount of refrigerant distributed to the outdoor heat exchanger 7 by controlling the first opening/closing valve 2, the second opening/closing valve 6, and the first expansion valve 4. The condensation temperature may be a value calculated based on the saturation pressure from the pressure sensor 64 .

During refrigerant distribution control during dehumidification operation, the operation control unit 51b controls the opening degree of the first expansion valve 4, for example, using the temperature of the refrigerant at the outlet of the reheater 3. That is, the operation control unit 51b uses the reheater outlet temperature measured by the refrigerant temperature sensor 67 to determine the degree of subcooling of the reheater 3. When determining the degree of subcooling of the reheater 3, the operation control unit 51b acquires the high-pressure pressure from the pressure sensor 62 and the reheater outlet temperature from the refrigerant temperature sensor 67. Then, the operation control unit 51b converts the high-pressure pressure to saturation to obtain the condensing temperature, and subtracts the reheater outlet temperature from the condensing temperature to obtain the degree of subcooling of the reheater 3. Then, the operation control unit 51b controls the first expansion valve 4 according to the obtained degree of subcooling, and controls the second opening/closing valve 6, the third opening/closing valve 10, and the second expansion valve 9 to adjust the amount of refrigerant distributed to the reheater 3. The condensing temperature may be a value converted to saturation from the pressure sensor 63.

[Processing and operation in the event of a refrigerant leak]
FIG. 10 is a diagram showing an example of the operation of each on-off valve and each expansion valve when refrigerant leakage occurs in the air conditioning apparatus 200 according to Embodiment 1.

Next, we will explain an example of the processing performed by the control device 50 when a refrigerant leak occurs, and the operation of each opening/closing valve and each expansion valve.

(When the indoor refrigerant leakage sensor 41 detects a refrigerant leakage)
When the indoor refrigerant leakage sensor 41 detects a refrigerant leakage, as shown in FIG. 10, the control device 50 closes the first on-off valve 2, opens the second on-off valve 6, closes the third on-off valve 10, fully opens the first expansion valve 4, fully closes the second expansion valve 9, and operates the compressor 1 to perform a pump-down operation. When performing the pump-down operation, the control device 50 may increase the rotation speed of the indoor blower 11 and the outdoor blower 12 to be higher than the rotation speed during normal operation. This is to increase the blowing amount to diffuse the leaked refrigerant so that the leaked refrigerant does not create a high concentration area. By the above-mentioned valve control and pump-down operation, when a refrigerant leakage occurs indoors, the refrigerant can be stored in the piping from the second on-off valve 6 to the outdoor heat exchanger 7, the outdoor heat exchanger 7, the piping from the outdoor heat exchanger 7 to the liquid reservoir 8, the liquid reservoir 8, and the piping from the liquid reservoir 8 to the second expansion valve 9.

Furthermore, the control device 50 stops the operation of the compressor 1 when the pressure on the suction side of the compressor 1 becomes lower than the set value, or when the pressure on the discharge side of the compressor 1 becomes higher than the set value. Then, after stopping the operation of the compressor 1, the control device 50 closes the second on-off valve 6. In this way, by closing the second on-off valve 6 after the compressor 1 is stopped, it is possible to suppress backflow of the refrigerant. And by gradually stopping the operation of the air conditioning device 100 as described above, it is possible to improve safety.

After performing the pump-down operation, if there is no problem in circulating the refrigerant through the compressor 1, the outdoor heat exchanger 7, the second expansion valve 9, and the indoor heat exchanger 5, the second on-off valve 6 can be opened to perform the cooling operation. By performing the cooling operation, it is possible to prevent the temperature in the air-conditioned space from rising, thereby suppressing a decrease in comfort. As a situation in which there is no problem in circulating the refrigerant through the compressor 1, the outdoor heat exchanger 7, the second expansion valve 9, and the indoor heat exchanger 5, it is assumed that the refrigerant leakage point is identified as between the first on-off valve 2 and the first expansion valve 4, or between the third on-off valve 10 and the first expansion valve 4, etc.

(When the outdoor refrigerant leakage sensor 42 detects a refrigerant leakage)
When the outdoor refrigerant leakage sensor 42 detects a refrigerant leakage, as shown in Fig. 10, the control device 50 opens the first on-off valve 2, closes the second on-off valve 6, closes the third on-off valve 10, fully closes the first expansion valve 4, fully opens the second expansion valve 9, and operates the compressor 1 to perform a pump-down operation. When performing the pump-down operation, the control device 50 may increase the rotation speed of the indoor blower 11 and the outdoor blower 12 to be higher than the rotation speed during normal operation. By performing the above-mentioned valve control and pump-down operation, when a refrigerant leakage occurs outdoors, the refrigerant can be stored in the piping from the first on-off valve 2 to the reheater 3, the reheater 3, and the piping from the reheater 3 to the first expansion valve 4.

Furthermore, the control device 50 stops the operation of the compressor 1 when the pressure on the suction side of the compressor 1 becomes lower than the set value, or when the pressure on the discharge side of the compressor 1 becomes higher than the set value. Then, after stopping the operation of the compressor 1, the control device 50 closes the first on-off valve 2. In this way, by closing the first on-off valve 2 after the compressor 1 is stopped, it is possible to suppress backflow of the refrigerant. And by gradually stopping the operation of the air conditioning device 100 as described above, it is possible to increase safety.

If there is no problem in circulating the refrigerant through the compressor 1, the reheater 3, the first expansion valve 4, and the indoor heat exchanger 5 after performing the pump-down operation, the first on-off valve 2 can be opened to perform the dehumidification operation. By continuing the dehumidification operation, it is possible to prevent an increase in humidity in the air-conditioned space, thereby suppressing a decrease in comfort. An example of a situation in which there is no problem in circulating the refrigerant through the compressor 1, the reheater 3, the first expansion valve 4, and the indoor heat exchanger 5 is when the refrigerant leakage point has been identified as between the second on-off valve 6 and the second expansion valve 9, for example.

As described above, in the air conditioning apparatus 100 according to the first embodiment, the control device 50 closes the second opening/closing valve 6 during dehumidification operation, thereby preventing refrigerant from stagnation in the outdoor heat exchanger 7, thereby suppressing a decrease in dehumidification capacity and enabling efficient dehumidification operation. The control device 50 may also fully close the second expansion valve 9 during dehumidification operation. In this way, it is possible to prevent refrigerant from flowing from the cooling circuit 32 into the main circuit 31, thereby improving the operating efficiency of the dehumidification operation.

The main circuit 31 also has a first on-off valve 2 that opens and closes between the first connection part M, which is the connection part between the main pipe 21 between the compressor 1 and the reheater 3 and the cooling pipe 22, and the reheater 3. The control device 50 is configured to close the first on-off valve 2 during cooling operation. This can prevent the refrigerant from flowing into the reheater 3, thereby improving the operating efficiency as well as smoothing the refrigerant circulation during cooling operation. In addition, the control device 50 may fully close the first expansion valve 4 during cooling operation. In this way, the refrigerant remaining in the flow path from the first connection part M through the reheater 3 and the first expansion valve 4 to the second connection part N can be prevented from flowing into the indoor heat exchanger 5, thereby further improving the operating efficiency during cooling operation.

Furthermore, when the indoor refrigerant leakage sensor 41 detects a refrigerant leak, the control device 50 closes the first opening/closing valve 2 and fully closes the second expansion valve 9. This prevents the refrigerant from flowing into the main circuit 31 installed in the room, and the refrigerant can be stored in the outdoor heat exchanger 7 and the liquid reservoir 8, thereby suppressing the leakage of the refrigerant into the room. In addition, the control device 50 may fully close the first expansion valve 4 when the indoor refrigerant leakage sensor 41 detects a refrigerant leak. In this way, it is possible to prevent the refrigerant remaining in the reheater 3 or the like from flowing into the indoor heat exchanger 5, so that if the refrigerant leakage point is not on the flow path from the first opening/closing valve 2 through the reheater 3 to the first expansion valve 4, the refrigerant leakage into the room can be reduced. In addition, the first opening/closing valve 2, the third opening/closing valve 10, and the first expansion valve 4 may be closed, and the portion of the refrigerant circuit 30 from the first opening/closing valve 2 to the first expansion valve 4 may be isolated to facilitate the process of identifying the refrigerant leakage point.

Furthermore, when the outdoor refrigerant leakage sensor 42 detects a refrigerant leak, the control device 50 closes the second opening/closing valve 6 and fully closes the first expansion valve 4. This makes it possible to block the flow of refrigerant to the outdoors, and also allows the outdoor refrigerant to be stored in the indoor heat exchanger 5, thereby suppressing outdoor refrigerant leakage. In addition, the control device 50 may fully close the second expansion valve 9 when the outdoor refrigerant leakage sensor 42 detects a refrigerant leak. In this way, the portion of the refrigerant circuit 30 from the second opening/closing valve 6 to the second expansion valve 9 can be separated, and the location of the refrigerant leak can be quickly identified.

However, if operation switching control or refrigerant distribution control is not performed, the refrigerant will flow more easily to the side where the indoor or outdoor temperature is lower. In other words, if operation switching control or refrigerant distribution control is not performed, when the indoor temperature is lower than the outdoor temperature, the refrigerant will flow more easily to the reheater 3, so the indoor temperature will rise above the desired temperature and the relative humidity will fall below the desired humidity. On the other hand, when the outdoor temperature is lower than the indoor temperature, the refrigerant will not flow easily to the reheater 3, so the indoor temperature will fall below the desired temperature and the relative humidity will rise above the desired humidity. In this regard, the control device 50 can adjust the refrigerant distribution to an appropriate amount as described above. Therefore, the amount of heat provided by the reheater 3 can be secured, allowing the indoor unit 70 to demonstrate its dehumidification capacity.

In addition, if only the second expansion valve 9 is controlled to keep the degree of supercooling of the outdoor heat exchanger 7 above the judgment value, liquid backflow may occur. This is because controlling only the second expansion valve 9 cannot reduce excess refrigerant. In this regard, as described above, the control device 50 executes SH control of the first expansion valve 4 to keep the degree of superheating by the reheater 3 above the judgment value, and executes SH control of the second expansion valve 9 (only partial control of the refrigerant amount adjustment control) to keep the degree of superheating by the outdoor heat exchanger 7 above the judgment value. As a result, the excess refrigerant is stored in the liquid reservoir 8, and the refrigerant can be stored in the outdoor heat exchanger 7 and can also be stored in the reheater 3 (only partial control of the refrigerant amount adjustment control), so the occurrence of liquid backflow can be suppressed. In other words, according to the air conditioning apparatus 100 of this embodiment 1, by combining SC control and SH control (only partial control of the refrigerant amount adjustment control) at the second expansion valve 9 with SH control and SC control (only partial control of the refrigerant amount adjustment control) at the first expansion valve 4, it is possible to suppress a decrease in reheat capacity and avoid damage to the compressor 1 due to liquid backflow.

In addition, by using a non-azeotropic refrigerant as the refrigerant circulating through the refrigerant circuit 30, the temperature of the inlet side of the indoor heat exchanger 5 is lower than the temperature of the outlet side of the refrigerant. In addition, the temperature of the inlet side of the refrigerant of the reheater 3 is higher than the temperature of the outlet side of the refrigerant. The indoor heat exchanger 5 and the reheater 3 are arranged so that the air that has passed through the inlet side of the refrigerant of the indoor heat exchanger 5 passes through the outlet side of the refrigerant of the reheater 3, and the air that has passed through the outlet side of the refrigerant of the indoor heat exchanger 5 passes through the inlet side of the refrigerant of the reheater 3. For example, the part of the indoor heat exchanger 5 where the refrigerant temperature is relatively low faces the part of the reheater 3 where the refrigerant temperature is relatively high, and the part of the indoor heat exchanger 5 where the refrigerant temperature is relatively high faces the part of the reheater 3 where the refrigerant temperature is relatively low. In other words, the indoor heat exchanger 5 and the reheater 3 are arranged so that the refrigerant flows from the top to the bottom in both cases. By arranging the indoor heat exchanger 5 and the reheater 3 in this manner, it is possible to reduce the variation in the discharge temperature, which is the temperature of the air blown out from the indoor unit 70 into the air-conditioned space, and the humidity unevenness caused by the variation in the discharge temperature. Therefore, it is possible to suppress the variation in the humidity of the air blown out from the indoor unit 70 into the air-conditioned space, and to stabilize the state of the air in the room.

As described above, the air conditioning device 100 according to the first embodiment includes a main circuit 31 in which the compressor 1, the first on-off valve 2, the reheater 3, the first expansion valve 4, and the evaporator are sequentially connected by the main pipe 21, a cooling circuit 32 in which the second on-off valve 6, the condenser, and the second expansion valve 9 are sequentially connected by the cooling pipe 22 connecting between the compressor 1 and the first on-off valve 2 and between the first expansion valve 4 and the evaporator, and a bypass circuit 33 having a bypass pipe 23 connecting between the discharge side of the compressor 1 and the reheater 3 and the first expansion valve 4 and a third on-off valve 10 for opening and closing the bypass pipe 23, and a refrigerant is The system is equipped with a circulating refrigerant circuit 30 and a control device 50 that controls the refrigerant circuit 30, with the reheater 3 and evaporator being arranged in the air-conditioned space and the condenser being arranged outside the air-conditioned space, and the control device 50 performs operation switching control by opening the first on-off valve 2 and the second on-off valve 6 and closing the third on-off valve 10, using the first expansion valve 4 to control the degree of superheat on the suction side of the compressor 1, and using the second expansion valve 9 to control the degree of subcooling of the condenser before switching operation to a cooling operation that cools the air in the air-conditioned space or a dehumidification operation that dehumidifies the air in the air-conditioned space.

According to the air conditioning device 100 of the first embodiment, the control device 50 performs operation switching control before switching the operation to the cooling operation or the dehumidification operation, by opening the first opening/closing valve 2 and the second opening/closing valve 6, closing the third opening/closing valve 10, controlling the degree of superheat on the suction side of the compressor 1 using the first expansion valve 4, and controlling the degree of subcooling of the condenser using the second expansion valve 9. By performing this operation switching control, the amount of refrigerant is adjusted to an appropriate value, so that it is possible to suppress the occurrence of an imbalance in the refrigerant distributed to each heat exchanger before the cooling operation or the dehumidification operation is performed.

In addition, in the air conditioning apparatus 100 according to embodiment 1, the control device 50 switches operation to cooling operation or dehumidification operation when the degree of subcooling of the condenser and the degree of superheat on the suction side of the compressor 1 reach preset values, or when a preset time has elapsed, during operation switching control.

According to the air conditioning device 100 of embodiment 1, after the amount of refrigerant is adjusted to an appropriate value, operation can be switched to cooling operation or dehumidification operation at an appropriate time.

In addition, in the air conditioning apparatus 100 according to embodiment 1, during cooling operation, when the degree of subcooling of the condenser is equal to or lower than a preset value, the condensing temperature of the condenser is lower than the value at which high pressure protection is implemented, which is a control for lowering the frequency of compressor 1 or stopping compressor 1, and the internal liquid temperature is higher than the evaporation temperature of the evaporator, the control device 50 performs refrigerant distribution control, which controls the first expansion valve 4 so that the degree of subcooling of the condenser becomes a preset value.

According to the air conditioning device 100 of the first embodiment, during cooling operation, the amount of condensation of the outdoor heat exchanger 7 required during cooling operation is secured, and necessary and sufficient cooling capacity can be exhibited. In addition, when adjusting the amount of refrigerant to an appropriate value, discharge of the refrigerant from the indoor side can be performed by differential pressure, and high pressure abnormalities do not occur when the refrigerant is discharged from the indoor side to distribute the refrigerant more toward the outdoor side.

In addition, in the air conditioning apparatus 100 according to embodiment 1, during cooling operation, when the degree of subcooling of the condenser is equal to or lower than a preset value, and the condensing temperature of the condenser is not lower than the value at which high pressure protection, which is a control to lower the frequency of compressor 1 or stop compressor 1, is implemented, or the internal liquid temperature is not higher than the evaporation temperature of the evaporator, the control device 50 performs refrigerant distribution control by opening the first on-off valve 2 and the second on-off valve 6 and closing the third on-off valve 10, and using the first expansion valve 4 to control the degree of subcooling of the reheater 3 and using the second expansion valve 9 to control the degree of superheat on the suction side of compressor 1.

According to the air conditioning device 100 of embodiment 1, even in a situation during cooling operation where it is determined that it is difficult to discharge the refrigerant from the indoor side due to a pressure difference, the state can be transitioned to the intended refrigeration cycle by forcibly circulating the refrigerant in intermediate operation, thereby achieving ideal cooling capacity.

In addition, in the air conditioning apparatus 100 according to embodiment 1, when the degree of subcooling of the condenser is greater than a preset value during cooling operation and the condensing temperature of the condenser is higher than the internal liquid temperature, the control device 50 performs refrigerant distribution control by opening the first opening/closing valve 2 and controlling the first expansion valve 4 so that the degree of subcooling of the condenser becomes the preset value.

According to the air conditioning device 100 of the first embodiment, during cooling operation, the amount of condensation in the outdoor heat exchanger 7 required during cooling operation can be secured, and sufficient cooling capacity can be achieved. In addition, when adjusting the amount of refrigerant to an appropriate value, differential pressure can be used to discharge the refrigerant from the indoor side.

In addition, in the air conditioning apparatus 100 according to embodiment 1, during cooling operation, when the degree of subcooling of the condenser is greater than a preset value and the condensing temperature of the condenser is not higher than the internal liquid temperature, the control device 50 performs refrigerant distribution control by opening the first on-off valve 2 and the second on-off valve 6, closing the third on-off valve 10, and using the first expansion valve 4 to control the degree of superheat on the suction side of the compressor 1 and using the second expansion valve 9 to control the degree of subcooling of the condenser.

According to the air conditioning device 100 of embodiment 1, even in a situation during cooling operation where it is determined that it is difficult to discharge the refrigerant from the indoor side due to a pressure difference, the state can be transitioned to the intended refrigeration cycle by forcibly circulating the refrigerant in intermediate operation, thereby achieving ideal cooling capacity.

In addition, in the air conditioning apparatus 100 according to embodiment 1, the control device 50 performs refrigerant distribution control during dehumidification operation by controlling the second expansion valve 9 so that the degree of subcooling in the reheater 3 becomes a preset value when the degree of subcooling in the reheater 3 is equal to or lower than a preset value, the condensing temperature of the reheater 3 is lower than the value at which high pressure protection is implemented, which is a control for lowering the frequency of the compressor 1 or stopping the compressor 1, and the external liquid temperature is higher than the evaporation temperature of the evaporator.

According to the air conditioning device 100 of the first embodiment, during dehumidification operation, the reheat amount of the reheater 3 required during dehumidification operation is secured, and the necessary and sufficient dehumidification capacity can be exhibited. In addition, when adjusting the amount of refrigerant to an appropriate value, discharge by differential pressure can be performed when discharging refrigerant from the outside of the room, and high pressure abnormalities can be avoided when discharging refrigerant from the outside of the room to increase the distribution of refrigerant to the inside of the room.

In addition, in the air conditioning apparatus 100 according to embodiment 1, during dehumidification operation, when the degree of subcooling of the reheater 3 is equal to or lower than a preset value, and the condensing temperature of the reheater 3 is not lower than the value at which high pressure protection, which is a control to lower the frequency of the compressor 1 or stop the compressor 1, is implemented, or the external liquid temperature is not higher than the evaporation temperature of the evaporator, the control device 50 performs refrigerant distribution control by opening the first on-off valve 2 and the second on-off valve 6 and closing the third on-off valve 10, and using the first expansion valve 4 to control the degree of superheat on the suction side of the compressor 1 and using the second expansion valve 9 to control the degree of subcooling of the condenser.

According to the air conditioning device 100 of embodiment 1, even in a situation during dehumidification operation where it is determined that it is difficult to discharge the refrigerant from the outside of the room due to a pressure difference, the state can be transitioned to the intended refrigeration cycle by forcibly circulating the refrigerant in intermediate operation, thereby achieving ideal cooling capacity.

In addition, in the air conditioning apparatus 100 according to embodiment 1, when the degree of subcooling of the reheater 3 is greater than a predetermined value during dehumidification operation and the condensing temperature of the reheater 3 is higher than the external liquid temperature, the control device 50 performs refrigerant distribution control by opening the second opening/closing valve 6 and controlling the second expansion valve 9 so that the degree of subcooling of the reheater 3 becomes the predetermined value.

According to the air conditioning device 100 of the first embodiment, during dehumidification operation, the amount of condensation in the reheater 3 required during dehumidification operation can be secured, and sufficient cooling capacity can be achieved. In addition, when adjusting the amount of refrigerant to an appropriate value, differential pressure discharge can be used to discharge the refrigerant from the outdoor side.

In addition, in the air conditioning apparatus 100 according to embodiment 1, when the degree of subcooling of the reheater 3 is greater than a preset value during dehumidification operation and the condensing temperature of the reheater 3 is not higher than the external liquid temperature, the control device 50 performs refrigerant distribution control by opening the first on-off valve 2 and the second on-off valve 6, closing the third on-off valve 10, and using the first expansion valve 4 to control the degree of subcooling of the reheater 3 and using the second expansion valve 9 to control the degree of superheat on the suction side of the compressor 1.

According to the air conditioning device 100 of embodiment 1, even in a situation during dehumidification operation where it is determined that it is difficult to discharge the refrigerant from the outside of the room due to a pressure difference, the state can be transitioned to the intended refrigeration cycle by forcibly circulating the refrigerant in intermediate operation, thereby achieving ideal cooling capacity.

In addition, the air conditioning device 100 according to embodiment 1 has an indoor refrigerant leakage sensor 41 that is provided in the air-conditioned space and detects refrigerant leakage, and the control device 50 closes the first opening/closing valve 2 when refrigerant leakage is detected by the indoor refrigerant leakage sensor 41.

In addition, in the air conditioning apparatus 100 of embodiment 1, the control device 50 brings the second expansion valve 9 into a fully closed state when a refrigerant leak is detected by the indoor refrigerant leak sensor 41.

According to the air conditioning device 100 of embodiment 1, it is possible to prevent the refrigerant from flowing into the main circuit 31 installed indoors, and the refrigerant can be stored in the outdoor heat exchanger 7 and the liquid reservoir 8, thereby suppressing leakage of the refrigerant into the room.

In addition, the air conditioning device 100 according to embodiment 1 has an outdoor refrigerant leakage sensor 42 that is provided outside the air-conditioned space and detects refrigerant leakage, and the control device 50 closes the second opening/closing valve 6 when refrigerant leakage is detected by the outdoor refrigerant leakage sensor 42.

In addition, in the air conditioning apparatus 100 according to embodiment 1, the control device 50 brings the first expansion valve 4 into a fully closed state when a refrigerant leak is detected by the outdoor refrigerant leak sensor 42.

According to the air conditioning device 100 of embodiment 1, the flow of refrigerant to the outdoors can be blocked, and the outdoor refrigerant can be stored in the indoor heat exchanger 5, thereby suppressing leakage of refrigerant outdoors.

In addition, the air conditioning apparatus 100 of embodiment 1 uses a non-azeotropic refrigerant mixture as the refrigerant circulating through the refrigerant circuit 30.

In addition, in the air conditioning apparatus 100 relating to embodiment 1, the evaporator and the reheater 3 are arranged so that air that has passed through the refrigerant inlet side of the evaporator passes through the refrigerant outlet side of the reheater 3, and air that has passed through the refrigerant outlet side of the evaporator passes through the refrigerant inlet side of the reheater 3.

In addition, in the air conditioning device 100 according to embodiment 1, both the evaporator and the reheater 3 are arranged so that the refrigerant flows from top to bottom.

According to the air conditioning device 100 of the first embodiment, by using a non-azeotropic refrigerant as the refrigerant circulating in the refrigerant circuit 30, the temperature of the inlet side of the refrigerant in the indoor heat exchanger 5 is lower than the temperature of the outlet side of the refrigerant. Also, the temperature of the inlet side of the refrigerant in the reheater 3 is higher than the temperature of the outlet side of the refrigerant. The indoor heat exchanger 5 and the reheater 3 are arranged so that the air that has passed through the inlet side of the refrigerant in the indoor heat exchanger 5 passes through the outlet side of the refrigerant in the reheater 3, and the air that has passed through the outlet side of the refrigerant in the indoor heat exchanger 5 passes through the inlet side of the refrigerant in the reheater 3. For example, the part of the indoor heat exchanger 5 where the refrigerant temperature is relatively low faces the part of the reheater 3 where the refrigerant temperature is relatively high, and the part of the indoor heat exchanger 5 where the refrigerant temperature is relatively high faces the part of the reheater 3 where the refrigerant temperature is relatively low. In other words, the indoor heat exchanger 5 and the reheater 3 are arranged so that the refrigerant flows from the top to the bottom in both cases. By arranging the indoor heat exchanger 5 and the reheater 3 in this manner, it is possible to reduce the variation in the discharge temperature, which is the temperature of the air blown out from the indoor unit 70 into the air-conditioned space, and the humidity unevenness caused by the variation in the discharge temperature. Therefore, it is possible to suppress the variation in the humidity of the air blown out from the indoor unit 70 into the air-conditioned space, and to stabilize the state of the air in the room.

Embodiment 2.
Hereinafter, the second embodiment will be described, but explanations of parts that overlap with the first embodiment will be omitted, and parts that are the same as or equivalent to the first embodiment will be given the same reference numerals.

Figure 11 is an overall configuration diagram of an air conditioning apparatus 200 relating to embodiment 2. In the air conditioning apparatus 200 relating to embodiment 2, part of the configuration of the refrigerant circuit 30 is different from that of the air conditioning apparatus 100 relating to embodiment 1.

As shown in Figure 11, the refrigerant circuit 30 according to the second embodiment differs from the first embodiment in that it does not have a liquid reservoir 8, but has an accumulator 18 instead, but otherwise has the same configuration as the first embodiment. During transient liquid backflow, the air conditioning device 200 can store refrigerant in the accumulator 18 provided between the compressor 1 and the indoor heat exchanger 5, further reducing the risk of damage to the compressor 1.

In the second embodiment, the operation switching control, the refrigerant distribution control during cooling operation, or the refrigerant distribution during dehumidification operation described in the first embodiment is performed, thereby enabling operation with the optimal amount of refrigerant in each of the reheater 3 and the outdoor heat exchanger 7. Therefore, the capacity of the air-conditioning device 200 can be properly maintained, and the excess refrigerant that occurs transiently can be stored in the inexpensive accumulator 18. In other words, even if the refrigerant returns to the compressor 1 due to liquid backflow, the action of the accumulator 18 can suppress liquid compression in the compressor 1, so that a highly reliable air-conditioning device 200 can be provided. The degree of subcooling of the reheater 3 is obtained from the high-pressure pressure obtained from the pressure sensor 62 and the reheater outlet temperature obtained from the refrigerant temperature sensor 67. The high-pressure pressure is converted to saturation to obtain the condensation temperature, and the degree of subcooling of the reheater 3 can be obtained by subtracting the reheater outlet temperature from the condensation temperature. The degree of subcooling of the outdoor heat exchanger 7 is obtained from the high-pressure pressure obtained from the pressure sensor 64 and the outdoor heat exchanger outlet temperature obtained from the refrigerant temperature sensor 69. The high-pressure pressure is converted to saturation to obtain the condensation temperature, and the degree of subcooling at the outdoor heat exchanger outlet can be obtained by subtracting the outdoor heat exchanger outlet temperature from the condensation temperature. Note that when obtaining the degree of subcooling of the outdoor heat exchanger 7, the high-pressure pressure obtained from the pressure sensor 62 may be used.

The control of each opening/closing valve and each expansion valve in the event of refrigerant leakage indoors or outdoors is the same as in embodiment 1 described above.

As described above, the air conditioning apparatus 200 of the second embodiment can also suppress the decline in dehumidification capacity and perform dehumidification operation efficiently. However, in the refrigerant circuit 30 equipped with the liquid reservoir 8 as in the first embodiment, it is necessary to perform an operation to ensure the degree of superheat for the second expansion valve 9 in order to protect against liquid backflow. Therefore, in order to store the surplus refrigerant, an expensive high-pressure vessel such as the large-capacity liquid reservoir 8 is required.

In this regard, in the air conditioning apparatus 200 according to the second embodiment, even if the refrigerant returns to the compressor 1 due to liquid backflow, the action of the accumulator 18 can suppress liquid compression in the compressor 1 even without a liquid reservoir, thereby improving the reliability of the air conditioning apparatus 200.

The air conditioning device 200 separates the non-azeotropic refrigerant mixture into gas and liquid using the accumulator 18, stores the high boiling point refrigerant in the accumulator 18, and uses the low boiling point refrigerant to increase the heat capacity during defrosting operation. In other words, during defrosting operation, the air conditioning device 200 stores the high boiling point refrigerant contained in the non-azeotropic refrigerant mixture in the accumulator 18, and circulates the low boiling point refrigerant contained in the non-azeotropic refrigerant mixture to the refrigerant circuit 30. This makes it possible to shorten the defrosting time. Other effects are the same as those of the first embodiment.

The operation of each opening/closing valve and each expansion valve in the event of a refrigerant leak, as illustrated in Figure 10, can also be applied to the configuration of embodiment 2.

The above-mentioned embodiments are preferred specific examples of the air conditioning apparatus 100, 200, and the technical scope of the present disclosure is not limited to these embodiments. For example, the air conditioning apparatus 100, 200 may not have the function of performing cooling operation and defrosting operation, in which case the first opening and closing valve 2 is not required. Thus, the main circuit 31 is a circuit in which the compressor 1, the reheater 3, the first expansion valve 4, and the indoor heat exchanger 5 are sequentially connected by the main pipe 21. In addition, in the first embodiment, an example in which the refrigerant circuit 30 is provided with a liquid reservoir 8 is shown, but this is not limited thereto, and the refrigerant circuit 30 according to the first embodiment may not have a liquid reservoir 8. Furthermore, in the above-mentioned embodiments, a case in which the main circuit 31 is arranged in the air-conditioned space is shown, but this is not limited thereto, and it is sufficient that at least the reheater 3 and the indoor heat exchanger 5 of the main circuit 31 are arranged in the air-conditioned space. In addition, the refrigerant circuit 30 according to the first embodiment may not have a bypass circuit 33. However, if the bypass circuit 33 is not provided in the refrigerant circuit 30, the defrosting operation in the flow path as in the first embodiment is not possible.

1 and 11 show an example in which the indoor refrigerant leakage sensor 41 is provided inside the indoor unit 70, but this is not limiting and the indoor refrigerant leakage sensor 41 may be provided inside the air-conditioned space and outside the indoor unit 70. Similarly, while FIG. 1 and 11 show an example in which the outdoor refrigerant leakage sensor 42 is provided inside the outdoor unit 80, this is not limiting and the outdoor refrigerant leakage sensor 42 may be provided outside the air-conditioned space and the outdoor unit 80.

1 and 11 show an example in which the control device 50 is provided inside the indoor unit 70, but this is not limiting, and the control device 50 may be provided inside the outdoor unit 80. In addition, the outdoor unit 80 may be provided with an outdoor control device that controls the operation of each actuator of the outdoor unit 80, such as the outdoor blower 12, and the control device 50 and the outdoor control device may work together to control the air conditioning devices 100, 200.

As described above, in the air conditioning apparatus 200 relating to embodiment 2, the refrigerant circuit 30 is provided with an accumulator 18 arranged between the compressor 1 and the evaporator.

According to the air conditioning apparatus 200 of embodiment 2, even if the refrigerant returns to the compressor 1 due to liquid backflow, the action of the accumulator 18 can suppress liquid compression in the compressor 1, thereby improving the reliability of the air conditioning apparatus 200.

1 Compressor, 1a Compressor motor, 2 First on-off valve, 3 Reheater, 4 First expansion valve, 5 Indoor heat exchanger, 6 Second on-off valve, 7 Outdoor heat exchanger, 8 Liquid reservoir, 9 Second expansion valve, 10 Third on-off valve, 11 Indoor blower, 11a Fan motor, 12 Outdoor blower, 12a Fan motor, 18 Accumulator, 20 Refrigerant piping, 21 Main piping, 22 Cooling piping, 23 Bypass piping, 30 Refrigerant circuit, 31 Main circuit, 32 Cooling circuit, 33 Bypass circuit, 41 Indoor refrigerant leakage sensor, 42 Outdoor refrigerant leakage sensor, 45 Abnormality alarm, 50 Control device, 51 Calculation processing unit, 51a Setting processing unit, 51b Operation control unit, 51c Excess refrigerant detection unit, 51d Leakage processing unit, 52 Memory unit, 61 Pressure sensor, 62 Pressure sensor, 63 pressure sensor, 64 pressure sensor, 65 refrigerant temperature sensor, 66 refrigerant temperature sensor, 67 refrigerant temperature sensor, 68 refrigerant temperature sensor, 69 refrigerant temperature sensor, 70 indoor unit, 80 outdoor unit, 91 air temperature sensor, 92 air temperature sensor, 100 air conditioner, 200 air conditioner.

Claims (9)

a refrigerant circuit including: a main circuit in which a compressor, a first on-off valve, a reheater, a first expansion valve, and an evaporator are successively connected by a main pipe; a cooling circuit in which a second on-off valve, a condenser, and a second expansion valve are successively connected by a cooling pipe connecting between the compressor and the first on-off valve and between the first expansion valve and the evaporator; and a bypass circuit having a bypass pipe connecting from the discharge side of the compressor to between the reheater and the first expansion valve and a third on-off valve for opening and closing the bypass pipe, in which a refrigerant circulates;
A control device for controlling the refrigerant circuit,
The reheater and the evaporator are disposed in an air-conditioning space,
The condenser is disposed outside the air-conditioned space,
The control device includes:
Before switching the operation to a cooling operation for cooling the air in the air-conditioned space or a dehumidification operation for dehumidifying the air in the air-conditioned space,
The first on-off valve and the second on-off valve are opened, and the third on-off valve is closed.
Implementing an operation switching control in which the first expansion valve is used to control the degree of superheat on the suction side of the compressor and the second expansion valve is used to control the degree of subcooling of the condenser;
During the cooling operation,
A refrigerant distribution control is performed based on a degree of subcooling of the condenser, a condensing temperature of the condenser and an internal liquid temperature which is a temperature of the refrigerant flowing through the reheater, or based on the condensing temperature of the condenser or the internal liquid temperature;
When the degree of subcooling of the condenser is equal to or lower than a preset value,
The condensation temperature of the condenser is not lower than a value at which high pressure protection, which is a control to reduce the frequency of the compressor or stop the compressor, is performed, or the internal liquid temperature is not higher than the evaporation temperature of the evaporator,
The first on-off valve and the second on-off valve are opened, and the third on-off valve is closed.
The first expansion valve is used to control the degree of subcooling of the reheater;
The second expansion valve is used to control the degree of superheat on the suction side of the compressor, thereby performing refrigerant distribution control.
Air conditioning units. a refrigerant circuit including: a main circuit in which a compressor, a first on-off valve, a reheater, a first expansion valve, and an evaporator are successively connected by a main pipe; a cooling circuit in which a second on-off valve, a condenser, and a second expansion valve are successively connected by a cooling pipe connecting between the compressor and the first on-off valve and between the first expansion valve and the evaporator; and a bypass circuit having a bypass pipe connecting from the discharge side of the compressor to between the reheater and the first expansion valve and a third on-off valve for opening and closing the bypass pipe, in which a refrigerant circulates;
A control device for controlling the refrigerant circuit,
The reheater and the evaporator are disposed in an air-conditioning space,
The condenser is disposed outside the air-conditioned space,
The control device includes:
Before switching the operation to a cooling operation for cooling the air in the air-conditioned space or a dehumidification operation for dehumidifying the air in the air-conditioned space,
The first on-off valve and the second on-off valve are opened, and the third on-off valve is closed.
Implementing an operation switching control in which the first expansion valve is used to control the degree of superheat on the suction side of the compressor and the second expansion valve is used to control the degree of subcooling of the condenser;
During the cooling operation,
A refrigerant distribution control is performed based on a degree of subcooling of the condenser, a condensing temperature of the condenser and an internal liquid temperature which is a temperature of the refrigerant flowing through the reheater, or based on the condensing temperature of the condenser or the internal liquid temperature;
When the degree of subcooling of the condenser is greater than a preset value,
When the condensation temperature of the condenser is higher than the internal liquid temperature,
The first opening/closing valve is opened, and the first expansion valve is controlled so that the degree of subcooling of the condenser becomes a preset value, thereby performing refrigerant distribution control.
Air conditioning units. a refrigerant circuit including: a main circuit in which a compressor, a first on-off valve, a reheater, a first expansion valve, and an evaporator are successively connected by a main pipe; a cooling circuit in which a second on-off valve, a condenser, and a second expansion valve are successively connected by a cooling pipe connecting between the compressor and the first on-off valve and between the first expansion valve and the evaporator; and a bypass circuit having a bypass pipe connecting from the discharge side of the compressor to between the reheater and the first expansion valve and a third on-off valve for opening and closing the bypass pipe, in which a refrigerant circulates;
A control device for controlling the refrigerant circuit,
The reheater and the evaporator are disposed in an air-conditioning space,
The condenser is disposed outside the air-conditioned space,
The control device includes:
Before switching the operation to a cooling operation for cooling the air in the air-conditioned space or a dehumidification operation for dehumidifying the air in the air-conditioned space,
The first on-off valve and the second on-off valve are opened, and the third on-off valve is closed.
Implementing an operation switching control in which the first expansion valve is used to control the degree of superheat on the suction side of the compressor and the second expansion valve is used to control the degree of subcooling of the condenser;
During the cooling operation,
A refrigerant distribution control is performed based on a degree of subcooling of the condenser, a condensing temperature of the condenser and an internal liquid temperature which is a temperature of the refrigerant flowing through the reheater, or based on the condensing temperature of the condenser or the internal liquid temperature;
When the degree of subcooling of the condenser is greater than a preset value,
When the condensation temperature of the condenser is not higher than the internal liquid temperature,
The first on-off valve and the second on-off valve are opened, and the third on-off valve is closed.
The first expansion valve is used to control the degree of superheat on the intake side of the compressor;
The second expansion valve is used to control the degree of subcooling of the condenser, and refrigerant distribution control is performed.
Air conditioning units. a refrigerant circuit including: a main circuit in which a compressor, a first on-off valve, a reheater, a first expansion valve, and an evaporator are successively connected by a main pipe; a cooling circuit in which a second on-off valve, a condenser, and a second expansion valve are successively connected by a cooling pipe connecting between the compressor and the first on-off valve and between the first expansion valve and the evaporator; and a bypass circuit having a bypass pipe connecting from the discharge side of the compressor to between the reheater and the first expansion valve and a third on-off valve for opening and closing the bypass pipe, in which a refrigerant circulates;
A control device for controlling the refrigerant circuit,
The reheater and the evaporator are disposed in an air-conditioning space,
The condenser is disposed outside the air-conditioned space,
The control device includes:
Before switching the operation to a cooling operation for cooling the air in the air-conditioned space or a dehumidification operation for dehumidifying the air in the air-conditioned space,
The first on-off valve and the second on-off valve are opened, and the third on-off valve is closed.
Implementing an operation switching control in which the first expansion valve is used to control the degree of superheat on the suction side of the compressor and the second expansion valve is used to control the degree of subcooling of the condenser;
During the dehumidification operation,
A refrigerant distribution control is performed based on the degree of subcooling of the reheater, the condensing temperature of the reheater and an external liquid temperature which is the temperature of the refrigerant flowing through the condenser, or the condensing temperature of the reheater or the external liquid temperature;
When the degree of subcooling of the reheater is equal to or lower than a preset value,
The condensation temperature of the reheater is not lower than a value at which high pressure protection, which is a control to reduce the frequency of the compressor or stop the compressor, is performed, or the external liquid temperature is not higher than the evaporation temperature of the evaporator,
The first on-off valve and the second on-off valve are opened, and the third on-off valve is closed.
The first expansion valve is used to control the degree of superheat on the intake side of the compressor;
The second expansion valve is used to control the degree of subcooling of the condenser, and refrigerant distribution control is performed.
Air conditioning units. a refrigerant circuit including: a main circuit in which a compressor, a first on-off valve, a reheater, a first expansion valve, and an evaporator are successively connected by a main pipe; a cooling circuit in which a second on-off valve, a condenser, and a second expansion valve are successively connected by a cooling pipe connecting between the compressor and the first on-off valve and between the first expansion valve and the evaporator; and a bypass circuit having a bypass pipe connecting from the discharge side of the compressor to between the reheater and the first expansion valve and a third on-off valve for opening and closing the bypass pipe, in which a refrigerant circulates;
A control device for controlling the refrigerant circuit,
The reheater and the evaporator are disposed in an air-conditioning space,
The condenser is disposed outside the air-conditioned space,
The control device includes:
Before switching the operation to a cooling operation for cooling the air in the air-conditioned space or a dehumidification operation for dehumidifying the air in the air-conditioned space,
The first on-off valve and the second on-off valve are opened, and the third on-off valve is closed.
Implementing an operation switching control in which the first expansion valve is used to control the degree of superheat on the suction side of the compressor and the second expansion valve is used to control the degree of subcooling of the condenser;
During the dehumidification operation,
A refrigerant distribution control is performed based on the degree of subcooling of the reheater, the condensing temperature of the reheater and an external liquid temperature which is the temperature of the refrigerant flowing through the condenser, or the condensing temperature of the reheater or the external liquid temperature;
When the degree of subcooling of the reheater is greater than a preset value,
When the condensation temperature of the reheater is higher than the external liquid temperature,
The second opening/closing valve is opened, and the second expansion valve is controlled so that the degree of subcooling of the reheater becomes a preset value, thereby performing refrigerant distribution control.
Air conditioning units. a refrigerant circuit including: a main circuit in which a compressor, a first on-off valve, a reheater, a first expansion valve, and an evaporator are successively connected by a main pipe; a cooling circuit in which a second on-off valve, a condenser, and a second expansion valve are successively connected by a cooling pipe connecting between the compressor and the first on-off valve and between the first expansion valve and the evaporator; and a bypass circuit having a bypass pipe connecting from the discharge side of the compressor to between the reheater and the first expansion valve and a third on-off valve for opening and closing the bypass pipe, in which a refrigerant circulates;
A control device for controlling the refrigerant circuit,
The reheater and the evaporator are disposed in an air-conditioning space,
The condenser is disposed outside the air-conditioned space,
The control device includes:
Before switching the operation to a cooling operation for cooling the air in the air-conditioned space or a dehumidification operation for dehumidifying the air in the air-conditioned space,
The first on-off valve and the second on-off valve are opened, and the third on-off valve is closed.
Implementing an operation switching control in which the first expansion valve is used to control the degree of superheat on the suction side of the compressor and the second expansion valve is used to control the degree of subcooling of the condenser;
During the dehumidification operation,
Refrigerant distribution control is performed based on the degree of subcooling of the reheater, the condensing temperature of the reheater and an external liquid temperature which is the temperature of the refrigerant flowing through the condenser, or the condensing temperature of the reheater or the external liquid temperature;
When the degree of subcooling of the reheater is greater than a preset value,
The condensation temperature of the reheater is not higher than the external liquid temperature,
The first on-off valve and the second on-off valve are opened, and the third on-off valve is closed.
The first expansion valve is used to control the degree of subcooling of the reheater;
The second expansion valve is used to control the degree of superheat on the suction side of the compressor, and refrigerant distribution control is performed.
Air conditioning units. The control device includes:
During the operation switching control,
An air-conditioning apparatus as described in any one of claims 1 to 6, wherein when the degree of subcooling of the condenser and the degree of superheat on the suction side of the compressor reach a preset value, or when a preset time has elapsed, operation is switched to the cooling operation or the dehumidification operation. The control device includes:
During the cooling operation,
When the degree of subcooling of the condenser is equal to or lower than a preset value,
When the condensation temperature of the condenser is lower than a value at which high pressure protection, which is a control to reduce the frequency of the compressor or stop the compressor, is performed, and the internal liquid temperature is higher than the evaporation temperature of the evaporator,
The air-conditioning apparatus according to any one of claims 1 to 3, further comprising: a refrigerant distribution control that controls the first expansion valve so that the degree of subcooling of the condenser becomes a preset value. The control device includes:
During the dehumidification operation,
When the degree of subcooling of the reheater is equal to or lower than a preset value,
When the condensation temperature of the reheater is lower than a value at which high pressure protection, which is a control to reduce the frequency of the compressor or stop the compressor, is performed, and the external liquid temperature is higher than the evaporation temperature of the evaporator,
The air-conditioning apparatus according to any one of claims 4 to 6, wherein refrigerant distribution control is performed to control the second expansion valve so that the degree of subcooling of the reheater becomes a preset value.

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