Air conditioning system

Abstract

To provide an air conditioner which easily contributes to energy saving while maintaining or improving comfort in operation.SOLUTION: An air conditioner comprises an indoor heat exchanger, an outdoor heat exchanger, first piping, second piping, a first expansion valve, an air / liquid separator, an opening / closing valve, a compressor, a four-way valve, third piping, a refrigerant heat exchanger and fourth piping. The third piping has one side which is connected to the second piping located between the air / liquid separator and the opening / closing valve via a first three-way valve or to the first piping between the four-way valve and the indoor heat exchanger, and the other side which is connected to the second piping located between the opening / closing valve and the indoor heat exchanger via a second three-way valve or to the second piping between the first expansion valve and the outdoor heat exchanger. The refrigerant heat exchanger exchanges heat between a refrigerant flowing between the first three-way valve and the second three-way valve in the third piping, and a refrigerant flowing out of the four-way valve in the first piping, and returning to the compressor.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to an air conditioner.

Background Art

[0002] An air conditioner such as an air conditioner adjusts the indoor temperature by condensing and evaporating a refrigerant in a refrigeration cycle. As one method of improving the comfort related to air conditioning during the operation of the air conditioner, it is to make the temperature of the blown air blown out from the indoor unit reach the set temperature required by the user quickly. That is, during the cooling operation, the blown temperature of the indoor unit is quickly lowered, and during the heating operation, the blown temperature of the indoor unit is quickly raised to improve the comfort related to air conditioning. Therefore, various proposals have been made, for example, to improve the heat exchange efficiency in the indoor unit and the outdoor unit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As one method of improving the heat exchange efficiency in the indoor unit and the outdoor unit, it is conceivable to increase the pressure of the gaseous refrigerant discharged from the compressor toward the indoor heat exchanger of the indoor unit or the outdoor heat exchanger of the outdoor unit. That is, by increasing the workload of the compressor, it becomes possible to improve the comfort related to air conditioning during operation. However, there is a problem that inconveniences such as an increase in power consumption (a decrease in energy saving) or an increase in noise and vibration during operation (a decrease in operation comfort) are likely to occur as the workload of the compressor increases (the comfort of air conditioning improves).

[0005] <亮 One example of a problem that the present invention aims to solve is to provide an air conditioning system that maintains or improves comfort during operation (air conditioning comfort, driving comfort) while also contributing to energy conservation. [Means for solving the problem]

[0006] An air conditioning system according to one embodiment of the present invention comprises an indoor heat exchanger, an outdoor heat exchanger, a first pipe, a second pipe, a first expansion valve, a gas-liquid separator, an on-off valve, a compressor, a four-way valve, a third pipe, a refrigerant heat exchanger, and a fourth pipe. The indoor heat exchanger is provided in the indoor unit. The outdoor heat exchanger is provided in the outdoor unit. The first pipe connects the indoor heat exchanger and the outdoor heat exchanger, through which the refrigerant flows. The second pipe connects the outdoor heat exchanger and the indoor heat exchanger, through which the refrigerant flows. The first expansion valve is provided in the second pipe. The gas-liquid separator is provided in the second pipe between the first expansion valve and the indoor heat exchanger. The on-off valve is provided in the second pipe between the gas-liquid separator and the indoor heat exchanger. The compressor is provided in the first piping and has an intake port for drawing in the refrigerant and an outlet port for discharging the refrigerant. A four-way valve is provided in the first piping and can change the direction in which the refrigerant flows. The third piping is connected on one side via a first three-way valve to the second piping between the gas-liquid separator and the on-off valve, or to the first piping between the four-way valve and the outdoor heat exchanger, and on the other side via a second three-way valve to the second piping between the on-off valve and the indoor heat exchanger, or to the second piping between the first expansion valve and the outdoor heat exchanger. The refrigerant heat exchanger performs heat exchange between the refrigerant flowing between the first three-way valve and the second three-way valve in the third piping and the refrigerant flowing out of the four-way valve in the first piping and returning to the compressor. The fourth piping introduces the gaseous refrigerant separated in the gas-liquid separator into the first piping between the refrigerant heat exchanger and the compressor.

[0007] Furthermore, the air conditioning system may include, for example, a second expansion valve between the four-way valve and the refrigerant heat exchanger.

[0008] Furthermore, the air conditioning system may also include, for example, a third expansion valve in the third piping that connects the second three-way valve, the first expansion valve, and the outdoor heat exchanger.

[0009] With the above air conditioning system, for example, the refrigerant returned to the compressor can be gasified in the refrigerant heat exchanger and returned to the compressor with increased pressure. As a result, the workload of the compressor can be reduced, while suppressing, maintaining, or increasing the pressure drop of the gaseous refrigerant discharged from the compressor to the outdoor heat exchanger or indoor heat exchanger, thereby maintaining or improving air conditioning capacity. Furthermore, it becomes possible to suppress, maintain, or increase the capacity of the outdoor heat exchanger or indoor heat exchanger. Therefore, it is possible to provide an air conditioning system that can reduce the workload of the compressor while maintaining or improving comfort related to air conditioning and comfort during operation. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a refrigerant system diagram of an air conditioning system according to an embodiment, and is also an illustrative and schematic diagram showing the flow of refrigerant during cooling operation. [Figure 2] Figure 2 is an exemplary and schematic block diagram showing the control device for an air conditioning system according to an embodiment and the configuration controlled by the control device. [Figure 3] Figure 3 is a refrigerant system diagram of an air conditioning system according to an embodiment, and is also an illustrative and schematic diagram showing the flow of refrigerant during heating operation. [Modes for carrying out the invention]

[0011] Several embodiments will be described below with reference to Figures 1 to 3. Note that in this specification, components and descriptions of such components may be expressed in multiple ways. The components and their descriptions are examples and are not limited by the expressions used herein. Components may also be identified by names different from those used herein. Furthermore, components may be described using expressions different from those used herein.

[0012] Figure 1 is an illustrative and schematic diagram showing the refrigerant system diagram of an air conditioning system 10 according to an embodiment. The air conditioning system 10 is, for example, a household air conditioner. However, the air conditioning system 10 is not limited to this example and may be other air conditioning systems such as commercial air conditioners.

[0013] As shown in Figure 1, the air conditioning system 10 includes an outdoor unit 11, an indoor unit 12, refrigerant piping 13, and a control device 14. The outdoor unit 11 is located outdoors, for example. The indoor unit 12 is located indoors, for example.

[0014] The air conditioning system 10 includes a refrigeration cycle in which an outdoor unit 11 and an indoor unit 12 are connected by refrigerant piping 13. Refrigerant flows between the outdoor unit 11 and the indoor unit 12 through the refrigerant piping 13. The outdoor unit 11 and the indoor unit 12 are also electrically connected to each other, for example, by electrical wiring.

[0015] The outdoor unit 11 includes an outdoor heat exchanger 21, an outdoor blower fan 22, a compressor 23, an accumulator 24, a four-way valve 25, a first expansion valve 31, a second expansion valve 32, a third expansion valve 33, a first three-way valve 34, a second three-way valve 35, a solenoid valve 36 (sometimes called an on / off valve), a first service valve 37, a second service valve 38, a gas-liquid separator 61, a refrigerant heat exchanger 62, etc. The indoor unit 12 includes an indoor heat exchanger 41 and an indoor blower fan 42.

[0016] The refrigerant piping 13 is a pipe made of a metal such as copper or aluminum. The refrigerant piping 13 includes a first pipe 51, a second pipe 52, a third pipe 53, a fourth pipe 54, and so on.

[0017] The first piping 51 connects the indoor heat exchanger 41 and the outdoor heat exchanger 21. The compressor 23, accumulator 24, four-way valve 25, second expansion valve 32, first service valve 37, and refrigerant heat exchanger 62 (heated side) are provided in the first piping 51. The first piping 51 has a first region 51a, a second region 51b, a third region 51c, and a fourth region 51d. The first region 51a is the piping region connecting the four-way valve 25 and the indoor heat exchanger 41. The second region 51b is the piping region connecting the four-way valve 25 and the accumulator 24 via the refrigerant heat exchanger 62 (heated side). The third region 51c is the piping region connecting the four-way valve 25 and the outdoor heat exchanger 21. The fourth area 51d is the piping area connecting the four-way valve 25 and the discharge port 23b of the compressor 23.

[0018] The second piping 52 connects the outdoor heat exchanger 21 and the indoor heat exchanger 41. The first expansion valve 31, solenoid valve 36, second service valve 38, and gas-liquid separator 61 are provided in the second piping 52. The second piping 52 has a fifth region 52a and a sixth region 52b. The fifth region 52a is the piping region connecting the first expansion valve 31 and the indoor heat exchanger 41 via the gas-liquid separator 61. The sixth region 52b is the piping region connecting the first expansion valve 31 and the outdoor heat exchanger 21.

[0019] The third pipe 53 connects the first pipe 51 and the second pipe 52. The third expansion valve 33, the first three-way valve 34, the second three-way valve 35, and the refrigerant heat exchanger 62 (heating side) are provided in the third pipe 53. The third pipe 53 has a seventh region 53a, an eighth region 53b, a ninth region 53c, and a tenth region 53d. The third pipe 53 has the seventh region 53a and the eighth region 53b on one side, and the ninth region 53c and the tenth region 53d on the other side. The seventh region 53a is a pipe region that connects the refrigerant heat exchanger 62 to the second pipe 52 (the fifth region 52a) between the gas-liquid separator 61 and the electromagnetic valve 36 (on-off valve) via the first three-way valve 34. Also, the eighth region 53b is a pipe region that connects the refrigerant heat exchanger 62 to the first pipe 51 (the third region 51c) between the four-way valve 25 and the outdoor heat exchanger 21 via the first three-way valve 34. Also, the ninth region 53c is a pipe region that connects the refrigerant heat exchanger 62 to the second pipe 52 (the fifth region 52a) between the electromagnetic valve 36 (on-off valve) and the indoor heat exchanger 41 via the second three-way valve 35. The tenth region 53d is a pipe region that connects the refrigerant heat exchanger 62 to the second pipe 52 (the sixth region 52b) between the first expansion valve 31 and the outdoor heat exchanger 21 via the second three-way valve 35.

[0020] The fourth pipe 54 connects the gas-liquid separator 61 and the first pipe 51. That is, the fourth pipe 54 is a pipe for introducing the gaseous refrigerant separated by the gas-liquid separator 61 into the first pipe 51 (the region between the refrigerant heat exchanger 62 and the accumulator 24 in the second region 51b) through which the refrigerant gasified by the refrigerant heat exchanger 62 flows.

[0021] In the cooling operation, the refrigerant flows from the indoor heat exchanger 41 to the outdoor heat exchanger 21 through the first pipe 51 and from the outdoor heat exchanger 21 to the indoor heat exchanger 41 through the second pipe 52. Also, in the heating operation, the refrigerant flows from the outdoor heat exchanger 21 to the indoor heat exchanger 41 through the first pipe 51 and from the indoor heat exchanger 41 to the outdoor heat exchanger 21 through the second pipe 52.

[0022] The outdoor heat exchanger 21 of the outdoor unit 11 absorbs heat of the refrigerant as an evaporator or releases heat of the refrigerant as a condenser according to the flow direction of the refrigerant. The outdoor blower fan 22 blows air to the outdoor heat exchanger 21 to promote the heat exchange between the refrigerant and the air in the outdoor heat exchanger 21. In other words, the outdoor blower fan 22 generates an air flow that exchanges heat with the outdoor heat exchanger 21.

[0023] The compressor 23 has a suction port 23a and a discharge port 23b. The compressor 23 sucks the refrigerant from the suction port 23a and discharges the compressed refrigerant from the discharge port 23b. Thereby, the compressor 23 compresses the refrigerant in the refrigeration cycle and causes the circulation of the refrigerant.

[0024] The accumulator 24 is connected to the suction port 23a of the compressor 23. The accumulator 24 separates the gaseous refrigerant and the liquid refrigerant. Thereby, the compressor 23 can suck the gaseous refrigerant that has passed through the accumulator 24 from the suction port 23a. The accumulator 24 can also serve as the suction port of the compressor 23 by being integrally formed with the compressor 23.

[0025] The four-way valve 25 is connected to the outdoor heat exchanger 21, the indoor heat exchanger 41, the discharge port 23b of the compressor 23, and the accumulator 24 (the suction port 23a of the compressor 23) via the second expansion valve 32 and the refrigerant heat exchanger 62. The four-way valve 25 switches the flow paths connected to the outdoor heat exchanger 21, the indoor heat exchanger 41, the discharge port 23b of the compressor 23, the second expansion valve 32, and the accumulator 24 via the refrigerant heat exchanger 62 during the heating operation and the cooling operation, and changes the direction in which the refrigerant flows.

[0026] During cooling operation, the four-way valve 25 connects the discharge port 23b of the compressor 23 to the outdoor heat exchanger 21. Furthermore, during cooling operation, the four-way valve 25 connects the indoor heat exchanger 41 to the accumulator 24. As a result, the refrigerant compressed by the compressor 23 flows to the outdoor heat exchanger 21, and the refrigerant that has undergone heat exchange (evaporated) in the indoor heat exchanger 41 flows to the accumulator 24. As will be described later, in the cooling operation of this embodiment, the indoor heat exchanger 41 does not completely gasify the refrigerant, but discharges a portion of the refrigerant in liquid form. The four-way valve 25 then flows the liquid-gas refrigerant to the refrigerant heat exchanger 62 via the second expansion valve 32. The liquid refrigerant is gasified (pressurized) in the refrigerant heat exchanger 62 and returns to the compressor 23 via the accumulator 24. Furthermore, during heating operation, the four-way valve 25 connects the outdoor heat exchanger 21 and the accumulator 24. In addition, during heating operation, the four-way valve 25 connects the discharge port 23b of the compressor 23 to the indoor heat exchanger 41. As a result, the refrigerant compressed by the compressor 23 flows to the indoor heat exchanger 41, and the refrigerant that has undergone heat exchange (evaporated) in the outdoor heat exchanger 21 flows to the accumulator 24. Note that during heating operation, the refrigerant discharged from the outdoor heat exchanger 21 passes through the four-way valve 25 to the second expansion valve 32 and the refrigerant heat exchanger 62 before returning to the accumulator 24. As a result, the liquid refrigerant is gasified (pressurized) in the refrigerant heat exchanger 62 and returns to the compressor 23 via the accumulator 24. Details of the refrigerant heat exchanger 62 will be described later.

[0027] The first expansion valve 31 provided in the second pipe 52, the second expansion valve 32 provided in the first pipe 51, and the third expansion valve 33 provided in the third pipe 53 are, for example, solenoid expansion valves. However, the first expansion valve 31, the second expansion valve 32, and the third expansion valve 33 may be other types of expansion valves. Also, the second expansion valve 32 and the third expansion valve 33 may be other types of valves. The first expansion valve 31, the second expansion valve 32, and the third expansion valve 33 regulate the amount of refrigerant passing through by controlling their opening degree. Note that either the second expansion valve 32 or the third expansion valve 33, or both, may be omitted.

[0028] The first three-way valve 34 is connected to the refrigerant heat exchanger 62, the second pipe 52, and the first pipe 51 on one side of the third pipe 53. The first three-way valve 34 switches between a flow path connecting the refrigerant heat exchanger 62 to the second pipe 52 and a flow path connecting it to the first pipe 51, depending on whether it is in cooling operation or heating operation.

[0029] The second three-way valve 35 connects the refrigerant heat exchanger 62 to the fifth region 52a and the sixth region 52b of the second pipe 52 on the other side of the third pipe 53. The second three-way valve 35 switches the flow path connecting the refrigerant heat exchanger 62 to the fifth region 52a and the flow path connecting it to the sixth region 52b depending on whether it is in cooling operation or heating operation.

[0030] The solenoid valve 36 is, for example, an on / off valve. During cooling operation, it is open, allowing the liquid refrigerant separated in the gas-liquid separator 61 to flow into the indoor heat exchanger 41. During heating operation, it is closed, preventing the refrigerant flowing out of the indoor heat exchanger 41 from flowing directly into the gas-liquid separator 61, and instead allowing it to flow to the gas-liquid separator 61 via the refrigerant heat exchanger 62. The solenoid valve 36 may be replaced with any other valve body that can open, close, or switch the flow path.

[0031] The first service valve 37 provided in the first piping and the second service valve 38 provided in the second piping are, for example, manually operated valves. The first service valve 37 and the second service valve 38 are closed, for example, in a factory, when the outdoor unit 11 is being manufactured and the first piping 51 to the fourth piping 54 of the outdoor unit 11 are filled with refrigerant. Then, when the air conditioning system 10 is installed (when the outdoor unit 11 and indoor unit 12 are installed), the first service valve 37 and the second service valve 38 are opened to fill the indoor unit 12 with the refrigerant that has been filled in the outdoor unit 11, thus completing the installation work. Therefore, the first service valve 37 and the second service valve 38 are fixed in an open state after the installation work is completed and before normal operation begins.

[0032] The gas-liquid separator 61 separates the two-phase liquid gas refrigerant flowing in from the first expansion valve 31 side during cooling operation, and the liquid gas refrigerant flowing in from the refrigerant heat exchanger 62 side (indoor heat exchanger 41 side) during heating operation, into a liquid medium and a gaseous medium. During cooling operation, the liquid refrigerant is sent to the indoor heat exchanger 41 side. During heating operation, the liquid refrigerant is sent to the outdoor heat exchanger 21 side. The separated gaseous refrigerant is sent to the accumulator 24 (compressor 23) through the fourth pipe 54.

[0033] The refrigerant heat exchanger 62 can utilize well-known double-pipe heat exchangers, plate heat exchangers, etc., and performs heat exchange between refrigerants flowing at different temperatures in a heating-side region (flow path, piping) and a heated-side region (flow path, piping), which are independent of each other. This raises the temperature of the liquid refrigerant on the lower temperature side, causing it to gasify. The pressure of the gasified refrigerant increases, and this high-pressure refrigerant is returned to the accumulator 24 (compressor 23). For example, during cooling operation, the high-pressure, high-temperature gaseous refrigerant discharged from the compressor 23 is received in the heating-side heat exchange section of the refrigerant heat exchanger 62 via the eighth region 53b and the first three-way valve 34. In addition, the liquid gaseous refrigerant discharged from the indoor heat exchanger 41 is received in the heated-side of the refrigerant heat exchanger 62 via the four-way valve 25 and the second expansion valve 32. On the other hand, during heating operation, the high-pressure, medium-temperature refrigerant discharged from the indoor heat exchanger 41 is received into the heated heat exchange section of the refrigerant heat exchanger 62 via the ninth region 53c and the second three-way valve 35. In addition, the heat-exchanged refrigerant discharged from the outdoor heat exchanger 21 is not returned directly to the accumulator 24 (compressor 23), but is received into the heated side of the refrigerant heat exchanger 62 via the four-way valve 25 and the second expansion valve 32. In both cooling and heating operation, the refrigerant heat exchanger 62 receives liquid refrigerant into the heated side, promoting gasification of the refrigerant through heat exchange with the heated side. In other words, the refrigerant pressure is increased by gasification and returned to the accumulator 24 (compressor 23).

[0034] The indoor heat exchanger 41 of the indoor unit 12 absorbs heat as an evaporator or releases heat as a condenser, depending on the direction of the refrigerant flow. The indoor blower fan 42 blows air toward the indoor heat exchanger 41, promoting heat exchange between the indoor heat exchanger 41 and the air. In other words, the indoor blower fan 42 generates an airflow that exchanges heat with the indoor heat exchanger 41.

[0035] The control device 14 controls the compressor 23, outdoor fan 22, indoor fan 42, valves, etc., located in the outdoor unit 11 and indoor unit 12, and performs cooling operation, heating operation, dehumidification operation, defrosting operation, and other operation control. The control device 14 is, for example, located in the indoor unit 12. In this case, the control device 14 may be controlled by receiving signals from, for example, a remote controller, or by receiving signals from an information terminal such as a smartphone via a communication device. In another embodiment, the control device 14 may be located on the outdoor unit 11 side. Alternatively, an outdoor control device may be provided separately for controlling the outdoor unit 11 side, and an indoor control device may be provided separately for controlling the indoor unit 12 side. The control device 14 is, for example, a computer having a control device such as a CPU (Central Processing Unit) or microcontroller, ROM (Read Only Memory), RAM (Random Access Memory), and a storage device such as flash memory. Note that the control device 14 is not limited to this example.

[0036] Figure 2 is an exemplary and schematic block diagram showing the control device 14 of the air conditioning system 10 of this embodiment and the configuration controlled by the control device 14. As shown in Figure 2, the air conditioning system 10 of this embodiment includes an outdoor fan drive circuit 81, an indoor fan drive circuit 82, an inverter circuit 83, a four-way valve drive circuit 84, a first expansion valve drive circuit 85, a second expansion valve drive circuit 86, a third expansion valve drive circuit 87, a first three-way valve drive circuit 88, a second three-way valve drive circuit 89, and a solenoid valve drive circuit 90.

[0037] The outdoor fan drive circuit 81 is the drive circuit for the outdoor blower fan 22. The indoor fan drive circuit 82 is the drive circuit for the indoor blower fan 42. The inverter circuit 83 controls the compressor 23 with an inverter and changes the frequency of the compressor 23. The inverter circuit 83 is, for example, a PAM (Pulse Amplitude Modulation) type inverter circuit. Note that the inverter circuit 83 is not limited to this example.

[0038] The four-way valve drive circuit 84 is the drive circuit for the four-way valve 25. The first expansion valve drive circuit 85 is the drive circuit for the first expansion valve 31. The second expansion valve drive circuit 86 is the drive circuit for the second expansion valve 32. The third expansion valve drive circuit 87 is the drive circuit for the third expansion valve 33. The first three-way valve drive circuit 88 is the drive circuit for the first three-way valve 34. The second three-way valve drive circuit 89 is the drive circuit for the second three-way valve 35. The solenoid valve drive circuit 90 is the drive circuit for the solenoid valve 36.

[0039] The control device 14 is connected to temperature sensors T1 to T8 and temperature sensor Su, an outdoor fan drive circuit 81, an indoor fan drive circuit 82, an inverter circuit 83, a four-way valve drive circuit 84, a first expansion valve drive circuit 85, a second expansion valve drive circuit 86, a third expansion valve drive circuit 87, a first three-way valve drive circuit 88, a second three-way valve drive circuit 89, and a solenoid valve drive circuit 90. The control device 14 also includes a temperature acquisition unit 91, an operation switching unit 92, an outdoor fan control unit 93, an indoor fan control unit 94, a compressor control unit 95, and a valve control unit 96.

[0040] The temperature acquisition unit 91 measures the temperature of each part in the refrigeration cycle using temperature sensors T1 to T8 and temperature sensor Su. For example, temperature sensor T1 detects the temperature of the refrigerant near the indoor heat exchanger 41 (value T1) between the indoor heat exchanger 41 and the four-way valve 25. Temperature sensor T2 detects the temperature of the refrigerant inside the indoor heat exchanger 41 (value T2). Temperature sensor T3 detects the temperature of the refrigerant inside the outdoor heat exchanger 21 (value T3). Temperature sensor T4 detects the temperature of the refrigerant near the outdoor heat exchanger 21 (value T4) between the outdoor heat exchanger 21 and the first expansion valve 31. Temperature sensor T5 detects the temperature of the refrigerant inside the refrigerant heat exchanger 62 (value T5). Temperature sensor T6 detects the temperature of the refrigerant near the third expansion valve 33 (value T6) in the 10th region 53d of the third piping 53, between the third expansion valve 33 and the second three-way valve 35. Temperature sensor T7 detects the temperature of the refrigerant (T7 value) between the first expansion valve 31 and the gas-liquid separator 61. Temperature sensor T8 detects the temperature of the refrigerant near the outdoor heat exchanger 21 (T8 value) between the four-way valve 25 and the outdoor heat exchanger 21. Temperature sensor Su detects the temperature of the refrigerant (Su value) at the refrigerant inlet of the accumulator.

[0041] The operation switching unit 92 switches between cooling operation, heating operation, dehumidification operation, defrosting operation, and other operations in the air conditioning system 10.

[0042] The outdoor fan control unit 93 controls the outdoor blower fan 22. For example, the outdoor fan control unit 93 controls the rotation speed of the motor of the outdoor blower fan 22 by controlling the outdoor fan drive circuit 81.

[0043] The indoor fan control unit 94 controls the indoor blower fan 42. For example, the indoor fan control unit 94 controls the rotation speed of the motor of the indoor blower fan 42 by controlling the indoor fan drive circuit 82.

[0044] The compressor control unit 95 controls the compressor 23. For example, the compressor control unit 95 controls the inverter circuit 83, thereby controlling the frequency (operating frequency) of the compressor 23 through inverter control.

[0045] The valve control unit 96 controls the four-way valve 25, the first expansion valve 31, the second expansion valve 32, the third expansion valve 33, the first three-way valve 34, the second three-way valve 35, and the solenoid valve 36. The valve control unit 96 drives the actuator of the four-way valve 25 by controlling the four-way valve drive circuit 84, thereby changing the direction in which the refrigerant flows through the four-way valve 25. The valve control unit 96 changes the opening degree of the first expansion valve 31, the second expansion valve drive circuit 86, and the third expansion valve drive circuit 87. By changing the opening degree of the first expansion valve 31, the second expansion valve 32, and the third expansion valve 33, the amount of refrigerant flowing through each valve is adjusted to control the flow rate (pressure) of the refrigerant supplied to the downstream side. Furthermore, the valve control unit 96 controls the first three-way valve drive circuit 88 and the second three-way valve drive circuit 89 to drive the actuators of the first three-way valve 34 and the second three-way valve 35, thereby changing the direction in which the refrigerant flows. In addition, the valve control unit 96 controls the solenoid valve drive circuit 90 to switch between the open and closed states of the solenoid valve 36, thereby changing the piping through which the refrigerant flows.

[0046] The cooling and heating operations of the air conditioning system 10 of this embodiment will be described below. Note that the air conditioning system 10 can perform other operations besides cooling and heating, such as dehumidification, defrosting, and sterilization. Furthermore, the cooling and heating operations of the air conditioning system 10 are not limited to the examples described below.

[0047] First, the cooling operation will be explained based on the flow pattern of the medium shown in Figure 1. For example, when the air conditioner 10 is started and the cooling operation starts at the same time, the outdoor blower fan 22, the compressor 23, and the indoor blower fan 42 are stopped. In this case, the outdoor fan control unit 93, the indoor fan control unit 94, and the compressor control unit 95 start the outdoor blower fan 22, the compressor 23, and the indoor blower fan 42 when the cooling operation starts.

[0048] During cooling operation, the outdoor fan control unit 93 adjusts the rotation speed of the outdoor blower fan 22. The indoor fan control unit 94 adjusts the rotation speed of the indoor blower fan 42. The compressor control unit 95 adjusts the frequency of the compressor 23. For example, the indoor fan control unit 94 controls the indoor blower fan 42 between low-speed and high-speed operation depending on the temperature of the room in which the indoor unit 12 is installed or a signal input from the remote controller.

[0049] When cooling operation begins, the valve control unit 96 controls the four-way valve drive circuit 84, the first three-way valve drive circuit 88, and the second three-way valve drive circuit 89 to change the direction of refrigerant flow in the four-way valve 25, the first three-way valve 34, and the second three-way valve 35 to cooling. The valve control unit 96 also controls the solenoid valve drive circuit 90 to open the solenoid valve 36. As a result, the outdoor heat exchanger 21 and the discharge port 23b of the compressor 23 are connected, and the indoor heat exchanger 41 and the accumulator 24 (the suction port 23a of the compressor 23) are connected via the refrigerant heat exchanger 62. In addition, the first three-way valve 34 is connected to the third region 51c of the first piping 51, and the third region 51c of the first piping 51 is connected to one side of the refrigerant heat exchanger 62. Furthermore, the second three-way valve 35 is connected to the sixth region 52b of the second piping 52, and the sixth region 52b of the second piping 52 is connected to the other side of the refrigerant heat exchanger 62. In addition, when the solenoid valve 36 is opened, the liquid refrigerant separated in the gas-liquid separator 61 flows into the indoor heat exchanger 41. That is, the control device 14 performs cooling operation by controlling the four-way valve 25 so that refrigerant flows from the discharge port 23b of the compressor 23 to the outdoor heat exchanger 21. Furthermore, by controlling the four-way valve 25, the control device 14 enables heat exchange control between refrigerants by ensuring that after the refrigerant flows from the discharge port 23b of the compressor 23 to the heating side flow path of the refrigerant heat exchanger 62, the refrigerant flows to the first expansion valve 31, and the refrigerant flowing out of the indoor heat exchanger 41 returns to the accumulator 24 (compressor 23) via the refrigerant heat exchanger 62.

[0050] In the case of cooling operation in the air conditioning system 10 of this embodiment, as described above, heat exchange is performed between refrigerants in the refrigerant heat exchanger 62 provided in the outdoor unit 11, and the workload of the compressor 23 is reduced by increasing the pressure of the gaseous refrigerant returned to the accumulator 24 (compressor 23).

[0051] Specifically, in the case of the air conditioning system 10 of this embodiment, during cooling operation, the high-pressure, high-temperature refrigerant discharged from the compressor 23 flows to the outdoor heat exchanger 21, and a portion of it flows to the heated heat exchange section of the refrigerant heat exchanger 62 via the eighth region 53b and the first three-way valve 34. In conventional air conditioning systems, the refrigerant undergoes a certain degree of superheating on the indoor unit 12 side before being returned to the outdoor unit 11. On the other hand, in the indoor unit 12 (indoor heat exchanger 41) of this embodiment, no superheating SH is achieved at all. That is, the refrigerant is not completely gasified, and the refrigerant is returned to the outdoor unit 11 side with a superheating SH of, for example, around -3°C. Therefore, some of the refrigerant remains in liquid form and flows to the heated side of the refrigerant heat exchanger 62 via the four-way valve 25 and the second expansion valve 32. The second expansion valve 32 adjusts the amount of refrigerant flowing to the refrigerant heat exchanger 62, that is, the heat exchange efficiency in the refrigerant heat exchanger 62.

[0052] Normally, the liquid refrigerant flowing into the indoor unit 12 is controlled to evaporate sufficiently in the indoor heat exchanger 41 and blow cool air into the room. However, in this embodiment, the air conditioning system 10 intentionally does not allow sufficient evaporation in the indoor heat exchanger 41 in order to supply liquid refrigerant to the refrigerant heat exchanger 62. Instead, it returns the liquid refrigerant to the outdoor unit 11 and evaporates it in the refrigerant heat exchanger 62. In this case, the amount of refrigerant evaporated in the indoor unit 12 decreases, resulting in a reduction in cooling capacity. Therefore, in this embodiment, a gas-liquid separator 61 is provided in the second piping 52 between the indoor heat exchanger 41 and the first expansion valve 31 to minimize, and preferably eliminate, the inclusion of gaseous refrigerant in the refrigerant flowing into the indoor heat exchanger 41, allowing only liquid refrigerant (refrigerant in a full liquid state) to flow. In the indoor heat exchanger 41 during cooling operation, gaseous refrigerant does not contribute to heat exchange. By removing gaseous refrigerant from the refrigerant flowing into the indoor heat exchanger 41, and making it almost entirely liquid refrigerant, the heat exchange efficiency can be improved. In other words, even if liquid refrigerant is flowed through the refrigerant heat exchanger 62, by increasing the amount of liquid refrigerant flowing into the indoor heat exchanger 41 (excluding gaseous refrigerant), it becomes possible to maintain or increase the cooling capacity while draining the liquid refrigerant from the indoor heat exchanger 41. Furthermore, by converting the refrigerant flowing into the indoor heat exchanger 41 into a liquid state through the operation of the gas-liquid separator 61, the heat exchange efficiency (cooling capacity) of the indoor heat exchanger 41 can be improved. In other words, it becomes possible to reduce the capacity of the indoor heat exchanger 41, which can contribute to the miniaturization of the indoor heat exchanger 41, and thus to the miniaturization of the indoor unit 12.

[0053] As described above, the liquid refrigerant flowing out of the indoor heat exchanger 41 flows to the heated side of the refrigerant heat exchanger 62 via the four-way valve 25 and the second expansion valve 32. There, in the refrigerant heat exchanger 62, heat exchange takes place with the high-temperature, high-pressure refrigerant flowing on the heated side, and the liquid refrigerant is vaporized. When the liquid refrigerant is heated and vaporized, its volume expands, and its pressure can be greatly increased. In other words, it becomes possible to return the high-pressure gaseous refrigerant to the compressor 23 via the accumulator 24. Since the refrigerant returns to the compressor 23 in a high-pressure gaseous state, the amount of increase (compression) required in the compressor 23 to raise the refrigerant pressure to the level required for cooling operation can be reduced compared to when the refrigerant heat exchanger 62 is not present. In other words, the workload of the compressor 23 can be reduced, contributing to energy saving. In the case of the air conditioning system 10 of this embodiment, as described above, the liquid refrigerant is supplied to the indoor heat exchanger 41 by the gas-liquid separator 61, so even if liquid refrigerant is supplied to the refrigerant heat exchanger 62, a decrease in cooling capacity (comfort during cooling) can be suppressed. Therefore, an air conditioning system 10 can be provided that maintains or improves comfort during cooling operation while also contributing to energy saving. Furthermore, since the workload of the compressor 23 can be reduced, vibrations and noise (operating noise) can also be reduced, contributing to improved operating comfort.

[0054] The refrigerant that has undergone heat exchange treatment by flowing through the heating side piping of the refrigerant heat exchanger 62 flows through the 10th region 53d of the third piping, merges with the heat-exchanged refrigerant that has flowed out from the outdoor heat exchanger 21, and flows through the first expansion valve 31 to the gas-liquid separator 61. The liquid refrigerant separated in the gas-liquid separator 61 is sent to the indoor heat exchanger 41 side in its entirety, as described above. The gaseous refrigerant separated in the gas-liquid separator 61 flows into the fourth piping, merges with the refrigerant that has been gasified in the refrigerant heat exchanger 62, and is returned to the accumulator 24 (compressor 23) side.

[0055] Furthermore, when performing control that contributes to maintaining (or improving) comfort and saving energy as described above, the control device 14 controls the superheat SH1 on the indoor unit 12 side by controlling the first expansion valve 31. That is, it controls the flow rate of the first expansion valve 31 so that the refrigerant temperature detected by the temperature sensor T1 becomes, for example, SH1 = T1 = -4℃. The control device 14 also controls the superheat SH2 of the compressor 23 by controlling the second expansion valve 32. The superheat SH2 of the compressor 23 can be obtained using the Su value, which is the detected value of the temperature sensor Su, and the T5 value, which is the detected value of the temperature sensor T5, and for example, it controls the flow rate of the second expansion valve 32 so that SH2 = Su - T5 ≥ 2℃. The control device 14 also controls the subcooling SC1 of the refrigerant heat exchanger 62 by controlling the third expansion valve 33. The subcooling SC1 of the refrigerant heat exchanger 62 can be obtained using the T6 value, which is the detected value of temperature sensor T6, and the T5 value, which is the detected value of temperature sensor T5. For example, the flow rate of the third expansion valve 33 is controlled so that SC1 = T6 - T5 ≈ 5°C. The control device 14 also controls the subcooling SC2 of the indoor heat exchanger 41 by controlling the first expansion valve 31. The subcooling SC2 of the indoor heat exchanger 41 can be obtained using the T4 value, which is the detected value of temperature sensor T4, and the T3 value, which is the detected value of temperature sensor T3. For example, the flow rate of the first expansion valve 31 may be controlled so that SC2 = T4 - T3 ≈ 5°C. In this case, the control device 14 may prioritize control so that SH1 = T1 = -4°C.

[0056] Next, the heating operation will be explained based on the flow pattern of the medium shown in Figure 3. In the case of heating operation, for example, if the startup of the air conditioning unit 10 and the start of heating operation are simultaneous, the outdoor blower fan 22, the compressor 23, and the indoor blower fan 42 are stopped. In this case, the outdoor fan control unit 93, the indoor fan control unit 94, and the compressor control unit 95 start the outdoor blower fan 22, the compressor 23, and the indoor blower fan 42 when the heating operation starts.

[0057] During heating operation, the outdoor fan control unit 93 adjusts the rotation speed of the outdoor blower fan 22. The indoor fan control unit 94 adjusts the rotation speed of the indoor blower fan 42. The compressor control unit 95 adjusts the frequency of the compressor 23. For example, the indoor fan control unit 94 controls the indoor blower fan 42 between low-speed and high-speed operation depending on the temperature of the room in which the indoor unit 12 is installed or a signal input from the remote controller.

[0058] When heating operation begins, the valve control unit 96 controls the four-way valve drive circuit 84, the first three-way valve drive circuit 88, and the second three-way valve drive circuit 89 to change the direction of refrigerant flow in the four-way valve 25, the first three-way valve 34, and the second three-way valve 35 for heating. The valve control unit 96 also controls the solenoid valve drive circuit 90 to close the solenoid valve 36. As a result, the indoor heat exchanger 41 is connected to the discharge port 23b of the compressor 23, and the outdoor heat exchanger 21 is connected to the accumulator 24 (the suction port 23a of the compressor 23) via the refrigerant heat exchanger 62. In addition, the first three-way valve 34 is connected to the fifth region 52a in the second piping 52 between the solenoid valve 36 and the gas-liquid separator 61, and the gas-liquid separator 61 is connected to one side of the refrigerant heat exchanger 62. Furthermore, the second three-way valve 35 is connected to a fifth region 52a in the second piping 52 between the indoor heat exchanger 41 and the solenoid valve 36, connecting the indoor heat exchanger 41 to the other side of the refrigerant heat exchanger 62. In addition, closing the solenoid valve 36 disconnects the direct connection between the indoor heat exchanger 41 and the gas-liquid separator 61. That is, the control device 14 performs heating operation by controlling the four-way valve 25 so that refrigerant flows from the discharge port 23b of the compressor 23 to the indoor heat exchanger 41. The control device 14 also enables heat exchange control between refrigerants by controlling the four-way valve 25 so that the liquid refrigerant flowing out of the outdoor heat exchanger 21 flows through the heated side of the refrigerant heat exchanger 62 and returns to the accumulator 24 (compressor 23), and the medium-temperature refrigerant flowing out of the indoor heat exchanger 41 passes through the heated side flow path of the refrigerant heat exchanger 62. In the case of heating operation in the air conditioning system 10 of this embodiment, as described above, heat exchange is performed between refrigerants in the refrigerant heat exchanger 62 provided in the outdoor unit 11, and by increasing the pressure of the gaseous refrigerant returned to the accumulator 24 (compressor 23), the workload of the compressor 23 can be reduced.

[0059] Specifically, in the case of the air conditioning system 10 of this embodiment, during heating operation, the high-pressure, high-temperature refrigerant discharged from the compressor 23 flows to the outdoor heat exchanger 21 for heat exchange, and blows warm air into the room where the indoor unit 12 is installed. The liquid-gas mixed refrigerant, which has become medium temperature and high pressure due to heat exchange, flows through the heating side piping of the refrigerant heat exchanger 62 via the second three-way valve 35. The refrigerant that has undergone heat exchange treatment by flowing through the heating side piping of the refrigerant heat exchanger 62 flows through the seventh region 53a of the third piping 53 and flows to the gas-liquid separator 61. The liquid refrigerant separated in the gas-liquid separator 61 is sent to the outdoor heat exchanger 21 side. The gaseous refrigerant separated in the gas-liquid separator 61 flows to the fourth piping, merges with the refrigerant that has been gasified in the refrigerant heat exchanger 62, and is returned to the accumulator 24 (compressor 23) side. Furthermore, the liquid refrigerant flowing out of the outdoor heat exchanger 21 flows through the four-way valve 25 to the heating side piping of the refrigerant heat exchanger 62. The liquid refrigerant flowing through the heating side piping is vaporized through heat exchange with the medium-temperature refrigerant flowing on the heating side, similar to during cooling operation. When the liquid refrigerant is heated and vaporized, its volume expands, significantly increasing its pressure. In other words, it becomes possible to return the high-pressure gaseous refrigerant to the compressor 23 via the accumulator 24. Because the refrigerant returns to the compressor 23 in a high-pressure gaseous state, the amount of compression required to increase the refrigerant pressure to the level needed during heating operation can be reduced compared to when the refrigerant heat exchanger 62 is not present. In other words, the workload of the compressor 23 can be reduced, contributing to energy saving. In addition, since the workload of the compressor 23 can be reduced even during heating operation, vibrations and noise (operating noise) can also be reduced, contributing to improved operating comfort.

[0060] In conventional indoor units, an auxiliary sub-heat exchanger is sometimes installed internally to save energy during heating operation, allowing for excessive overcooling on the indoor unit side and returning the excess to the outdoor unit side. However, increasing the amount of liquid refrigerant on the indoor unit side can reduce the heat exchange efficiency in the indoor heat exchanger, and the low-temperature liquid refrigerant may accumulate in part of the indoor heat exchanger, lowering the discharge temperature. To suppress this phenomenon, it was sometimes necessary to increase the pressure of the refrigerant flowing through the indoor heat exchanger 41 (increasing the workload of the compressor). On the other hand, in the air conditioning system 10 of this embodiment, during heating operation, the refrigerant heat exchanger 62 on the outdoor unit 11 side performs some of the overcooling that was conventionally performed in the indoor heat exchanger 41. As a result, it is possible to reduce the accumulation of low-temperature refrigerant in the indoor heat exchanger 41, thereby suppressing the problem of a decrease in discharge temperature. Furthermore, it is possible to suppress an excessive increase in the pressure of the refrigerant supplied to the indoor heat exchanger 41. In other words, the workload of the compressor 23 can be reduced. Furthermore, similar to cooling operation, high-pressure gaseous refrigerant can be returned from the refrigerant heat exchanger 62 to the compressor 23. In this respect as well, the air conditioning system 10 of this embodiment can reduce the workload of the compressor 23 and contribute to energy saving. Therefore, an air conditioning system 10 can be provided that maintains or improves comfort during heating operation while also contributing to energy saving. In addition, since part of the refrigerant liquefaction can be performed on the outdoor unit 11 side by the refrigerant heat exchanger 62, a sub-heat exchanger or similar configuration is not required on the indoor unit 12 side, which can contribute to miniaturization of the indoor unit 12.

[0061] Furthermore, when performing control that contributes to maintaining (or improving) comfort and saving energy as described above, the control device 14 controls the first expansion valve 31 to control the supercooling SC3 on the indoor unit 12 side. The supercooling SC3 on the indoor unit 12 side can be obtained using the T7 value, which is the detected value of the temperature sensor T7, and the T5 value, which is the detected value of the temperature sensor T5. For example, the flow rate of the first expansion valve 31 is controlled so that SC3 = T7 - ​​T5 = 5°C. In this case, the indoor heat exchanger 41 is, for example, a heat exchanger with a supercooling degree of -5°C. The control device 14 also controls the superheating degree SH3 of the compressor 23 by controlling the second expansion valve 32. The superheating degree SH3 of the compressor 23 can be obtained using the Su value, which is the detected value of the temperature sensor Su, and the T5 value, which is the detected value of the temperature sensor T5. For example, the flow rate of the second expansion valve 32 is controlled so that SH3 = Su - T5 ≥ 2°C. Furthermore, the control device 14 controls the superheating degree SH4 of the outdoor unit 11 by controlling the first expansion valve 31. The superheating degree SH4 on the outdoor unit 11 side can be obtained using the T8 value, which is the detected value of the temperature sensor T8, and the T3 value, which is the detected value of the temperature sensor T3. For example, the flow rate of the first expansion valve 31 is controlled so that SH4 = T8 - T3 = -3℃. In this case, the control device 14 may prioritize the control of the supercooling SC3 on the indoor unit 12 side.

[0062] The air conditioning system 10 according to the embodiment described above comprises an indoor heat exchanger 41, an outdoor heat exchanger 21, a first pipe 51, a second pipe 52, a first expansion valve 31, a gas-liquid separator 61, a solenoid valve 36 (on-off valve), a compressor 23, a four-way valve 25, a third pipe 53, a refrigerant heat exchanger 62, and a fourth pipe 54. The indoor heat exchanger 41 is installed in the indoor unit 12. The outdoor heat exchanger 21 is installed in the outdoor unit 11. The first pipe 51 connects the indoor heat exchanger 41 and the outdoor heat exchanger 21, through which the refrigerant flows. The second pipe 52 connects the outdoor heat exchanger 21 and the indoor heat exchanger 41, through which the refrigerant flows. The first expansion valve 31 is installed in the second pipe 52. The gas-liquid separator 61 is installed in the second piping 52 between the first expansion valve 31 and the indoor heat exchanger 41. The solenoid valve 36 is installed in the second piping 52 between the gas-liquid separator 61 and the indoor heat exchanger 41. The compressor 23 is installed in the first piping 51 and has an intake port 23a for drawing in refrigerant and an outlet port 23b for discharging refrigerant. The four-way valve 25 is installed in the first piping 51 and can change the direction in which the refrigerant flows. The third pipe 53 is connected on one end via the first three-way valve 34 to the second pipe 52 between the gas-liquid separator 61 and the solenoid valve 36, or to the first pipe 51 between the four-way valve 25 and the outdoor heat exchanger 21, and on the other end via the second three-way valve 35 to the second pipe 52 between the solenoid valve 36 and the indoor heat exchanger 41, or to the second pipe 52 between the first expansion valve 31 and the outdoor heat exchanger 21. The refrigerant heat exchanger 62 performs heat exchange between the refrigerant flowing between the first three-way valve 34 and the second three-way valve 35 in the third pipe 53 and the refrigerant flowing out of the four-way valve 25 in the first pipe 51 and returning to the compressor 23, thereby gasifying the refrigerant. The fourth pipe 54 introduces the gaseous refrigerant separated in the gas-liquid separator 61 into the first pipe 51 through which the refrigerant gasified in the refrigerant heat exchanger 62 flows. With this configuration, for example, the refrigerant to be returned to the compressor 23 can be gasified in the refrigerant heat exchanger 62 and returned to the compressor 23 with increased pressure. As a result, the workload of the compressor 23 can be reduced, and the decrease in pressure of the gaseous refrigerant discharged from the compressor 23 toward the outdoor heat exchanger 21 or indoor heat exchanger 41 can be suppressed, maintained, or increased, thereby maintaining or improving the air conditioning capacity.Furthermore, it becomes possible to suppress, maintain, or increase the performance of the outdoor heat exchanger 21 or the indoor heat exchanger 41. Therefore, it is possible to provide an air conditioning system 10 that can maintain or improve comfort related to air conditioning while reducing the workload of the compressor 23.

[0063] Furthermore, the air conditioning system 10 may also include, for example, a second expansion valve 32 between the four-way valve 25 and the refrigerant heat exchanger 62. With this configuration, the amount of refrigerant flowing through the refrigerant heat exchanger 62 can be easily controlled, and the heat exchange efficiency in the refrigerant heat exchanger 62 can be easily controlled.

[0064] Furthermore, the air conditioning system 10 may also be equipped with a third expansion valve 33 in a third pipe 53 that connects a second three-way valve 35, a second pipe 52 that connects a first expansion valve 31 and an outdoor heat exchanger 21, and a third expansion valve 33. With this configuration, the amount of refrigerant flowing through the second pipe 52 during cooling operation can be easily controlled, and the heat exchange efficiency in the indoor heat exchanger 41 can be easily controlled.

[0065] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0066] 10...Air conditioning unit, 11...Outdoor unit, 12...Indoor unit, 13...Refrigerant piping, 14...Control device, 21...Outdoor heat exchanger, 23...Compressor, 25...Four-way valve, 31...First expansion valve, 32...Second expansion valve, 33...Third expansion valve, 34...First three-way valve, 35...Second three-way valve, 36...Solenoid valve (on / off valve), 41...Indoor heat exchanger, 51...First piping, 52...Second piping, 53...Third piping, 54...Fourth piping, 61...Gas-liquid separator, 62...Refrigerant heat exchanger.

Claims

1. The indoor heat exchanger installed in the indoor unit, The outdoor heat exchanger installed on the outdoor unit, A first pipe connects the indoor heat exchanger and the outdoor heat exchanger, through which the refrigerant flows, A second pipe connects the outdoor heat exchanger and the indoor heat exchanger, through which the refrigerant flows, The first expansion valve provided in the second piping, In the second piping, a gas-liquid separator is provided between the first expansion valve and the indoor heat exchanger, In the second piping, an on / off valve is provided between the gas-liquid separator and the indoor heat exchanger, A compressor provided in the first piping, having an inlet for drawing in the refrigerant and an outlet for discharging the refrigerant, A four-way valve is provided in the first piping, which can change the direction in which the refrigerant flows, A third pipe, one end of which is connected via a first three-way valve to a second pipe between the gas-liquid separator and the on-off valve, or to the first pipe between the four-way valve and the outdoor heat exchanger, and the other end of which is connected via a second three-way valve to the second pipe between the on-off valve and the indoor heat exchanger, or to the second pipe between the first expansion valve and the outdoor heat exchanger, A refrigerant heat exchanger that performs heat exchange between the refrigerant flowing between the first three-way valve and the second three-way valve in the third piping and the refrigerant flowing out of the four-way valve in the first piping and returning to the compressor, A fourth pipe for introducing the gaseous refrigerant separated by the gas-liquid separator into the first pipe between the refrigerant heat exchanger and the compressor, An air conditioning system equipped with the following features.

2. The air conditioning device according to claim 1, further comprising a second expansion valve between the four-way valve and the refrigerant heat exchanger.

3. The air conditioning device according to claim 1 or claim 2, wherein the third expansion valve is provided in the third piping that connects the second three-way valve and the second piping that connects the first expansion valve and the outdoor heat exchanger.

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