Refrigeration cycle device

Abstract

The present invention suppresses noise accompanying operation of a flow path switching mechanism when switching functions of first and second heat source heat exchangers while continuing operation of a compressor. This air conditioning device is provided with a compressor, a first heat source heat exchanger and a second heat source heat exchanger, a first switching valve, a second switching valve, and a control unit. The first switching valve switches the state of the first heat source heat exchanger between a radiator and an evaporator. The second switching valve switches the state of the second heat source heat exchanger between a radiator and an evaporator. When the control unit changes from a state in which the second heat source heat exchanger functions as an evaporator and the first heat source heat exchanger functions as a radiator to a state in which the second heat source heat exchanger functions as a radiator and the first heat source heat exchanger functions as an evaporator, while continuing the operation of the compressor, the rotational speed of the compressor is a predetermined rotational speed (Rc) smaller than the maximum rotational speed (Rmax) of the compressor.

Description

Refrigeration Cycle Equipment

[0001] This relates to a refrigeration cycle device.

[0002] Conventionally, as in Patent Document 1 (Publication No. 9-318206), a refrigeration cycle device has been known in which a plurality of heat source heat exchangers are provided, and some of the heat source heat exchangers are used as evaporators while the other heat source heat exchangers are used as radiators.

[0003] In the refrigeration cycle device of Patent Document 1 (Publication No. 7-318206), it is possible to perform heating operation using some of the heat source heat exchangers while defrosting other heat source heat exchangers, so there is no need to interrupt heating operation for defrosting, and defrosting can be performed while ensuring user comfort.

[0004] In the refrigeration cycle device of Patent Document 1 (Publication No. 7-318206), when switching between a heat source heat exchanger used as an evaporator and a heat source heat exchanger used as a radiator while continuing heating operation, the compressor continues to operate while a flow path switching mechanism is operated to switch the flow direction of the refrigerant in the heat source heat exchanger.

[0005] Therefore, in this refrigeration cycle device, there is a possibility that multiple flow path switching mechanisms will be operated when a high pressure difference exists within the refrigerant circuit, and noise generated when the flow path switching mechanisms operate can easily become a problem.

[0006] A refrigeration cycle apparatus according to a first aspect includes a compressor, a first heat source heat exchanger, a second heat source heat exchanger, a first switching mechanism, a second switching mechanism, and a control unit. The first switching mechanism switches between a state in which refrigerant discharged from a discharge port of the compressor flows into the first heat source heat exchanger to function as a radiator, and a state in which refrigerant that has passed through the first heat source heat exchanger functioning as an evaporator flows into a suction port of the compressor. The second switching mechanism switches between a state in which refrigerant discharged from a discharge port of the compressor flows into the second heat source heat exchanger to function as a radiator, and a state in which refrigerant that has passed through the second heat source heat exchanger functioning as an evaporator flows into a suction port of the compressor. The control unit controls the operation of the compressor, the first switching mechanism, and the second switching mechanism. When the control unit changes the state from one in which the second heat source heat exchanger functions as an evaporator and the first heat source heat exchanger functions as a radiator to one in which the second heat source heat exchanger functions as a radiator and the first heat source heat exchanger functions as an evaporator while continuing to operate the compressor, the rotation speed of the compressor is a predetermined rotation speed that is smaller than the maximum rotation speed of the compressor.

[0007] In the refrigeration cycle device of the first aspect, when switching the functions of the first and second heat source heat exchangers while continuing to operate the compressor, the compressor rotation speed is kept lower than the maximum rotation speed, thereby suppressing noise associated with the operation of the flow path switching mechanism.

[0008] A refrigeration cycle apparatus according to a second aspect is the refrigeration cycle apparatus according to the first aspect, wherein the predetermined rotation speed is smaller than half of the maximum rotation speed.

[0009] In the refrigeration cycle device of the second aspect, when switching the functions of the first and second heat source heat exchangers while continuing to operate the compressor, the compressor rotation speed is kept lower than half the maximum rotation speed, which makes it easier to suppress noise associated with the operation of the flow path switching mechanism.

[0010] A refrigeration cycle device of a third aspect is a refrigeration cycle device of the first or second aspect, wherein the rotation speed of the compressor when the control unit changes from a state in which both the first heat source heat exchanger and the second heat source heat exchanger function as evaporators to a state in which one of the first heat source heat exchanger and the second heat source heat exchanger functions as a radiator while continuing to operate the compressor is a rotation speed that is smaller than the maximum rotation speed of the compressor.

[0011] In the refrigeration cycle device of the third aspect, even when the function of one of the first and second heat source heat exchangers functioning as an evaporator is switched to a radiator while the compressor continues to operate, the compressor rotation speed is kept lower than the maximum rotation speed, thereby suppressing noise associated with the operation of the flow path switching mechanism.

[0012] A refrigeration cycle apparatus according to a fourth aspect is the refrigeration cycle apparatus according to any one of the first aspect to the third aspect, further comprising a utilization heat exchanger, piping, and a sound-absorbing member. The piping connects the utilization heat exchanger with the first switching mechanism and the second switching mechanism. The sound-absorbing member is installed in the piping.

[0013] In the refrigeration cycle device of the fourth aspect, by providing a sound-absorbing member in the piping, it is possible to suppress the propagation of noise to the space in which the utilization heat exchanger is installed (for example, the space to be air-conditioned if air conditioning is performed using the utilization heat exchanger) or a space nearby.

[0014] A refrigeration cycle apparatus according to a fifth aspect is the refrigeration cycle apparatus according to the fourth aspect, further comprising a casing that houses the first heat source heat exchanger, the second heat source heat exchanger, the first switching mechanism, and the second switching mechanism. A single sound-absorbing member is installed within the casing.

[0015] In the refrigeration cycle apparatus of the fifth aspect, the single sound-deadening member can suppress the propagation of noise to the space in which the utilization heat exchanger is installed, while suppressing an increase in the number of parts.

[0016] A refrigeration cycle apparatus according to a sixth aspect is the refrigeration cycle apparatus according to any one of the first to fifth aspects, further comprising: a first valve that adjusts a flow rate of refrigerant flowing through the first heat source heat exchanger; and a second valve that adjusts a flow rate of refrigerant flowing through the second heat source heat exchanger. The control unit further controls operation of the first valve and the second valve. When using the first heat source heat exchanger as an evaporator and the second heat source heat exchanger as a radiator to defrost the second heat source heat exchanger, the control unit increases the opening degree of the second valve to a value greater than the opening degree of the second valve when using the second heat source heat exchanger as an evaporator.

[0017] If liquid refrigerant accumulates in the second heat source heat exchanger during defrosting, the time required to defrost the second heat source heat exchanger increases, and there is a possibility that unmelted frost will occur. In contrast, in the refrigeration cycle device of the sixth aspect, the opening degree of the second valve corresponding to the first heat source heat exchanger where defrosting is performed is larger than the opening degree of the second valve when the second heat source heat exchanger is used as an evaporator, so that liquid refrigerant is less likely to accumulate in the second heat source heat exchanger during defrosting. Therefore, the refrigeration cycle device of the sixth aspect can shorten the time required for defrosting and suppress the occurrence of unmelted frost.

[0018] A refrigeration cycle device of a seventh aspect is a refrigeration cycle device of any one of the first aspect to the sixth aspect, wherein the control unit uses the first heat source heat exchanger as an evaporator while using the second heat source heat exchanger as a radiator, and when a predetermined condition is satisfied when defrosting the second heat source heat exchanger, increases the opening degree of the first valve.

[0019] When the second heat source heat exchanger is used as a radiator and the first heat source heat exchanger is used as an evaporator, a portion of the refrigerant that has passed through the second heat source heat exchanger is sent to the first heat source heat exchanger. In the refrigeration cycle device of the seventh aspect, the opening degree of the second valve is increased when a predetermined condition is satisfied, which facilitates refrigerant flow through the first heat source heat exchanger. Therefore, even if liquid refrigerant accumulates in the second heat source heat exchanger where defrosting is performed, this liquid refrigerant is more likely to be discharged from the second heat source heat exchanger. As a result, the refrigeration cycle device of the seventh aspect can shorten the time required to defrost the second heat source heat exchanger and reduce the amount of frost remaining in the second heat source heat exchanger.

[0020] A refrigeration cycle apparatus of an eighth aspect is the refrigeration cycle apparatus of any one of the first aspect to the seventh aspect, further comprising a first refrigerant pipe, a suction pipe, a bypass pipe, and a bypass valve. A first heat source heat exchanger and a second heat source heat exchanger are connected in parallel to one end of the first refrigerant pipe, and a utilization heat exchanger is connected to the other end of the first refrigerant pipe. The suction pipe is connected to a suction port of the compressor. The bypass pipe connects the first refrigerant pipe and the suction pipe. The bypass valve is provided in the bypass pipe. The control unit further controls operation of the bypass valve. When using the first heat source heat exchanger as an evaporator and the second heat source heat exchanger as a radiator to defrost the second heat source heat exchanger, the control unit opens the closed bypass valve or increases the opening degree of the open bypass valve when a predetermined condition is satisfied.

[0021] In the refrigeration cycle apparatus of the eighth aspect, by opening the bypass valve that was closed or by increasing the opening degree of the bypass valve that was open, a portion of the refrigerant flowing to the first heat source heat exchanger flows through the bypass pipe, so that even if liquid refrigerant accumulates in the second heat source heat exchanger where defrosting is performed, this liquid refrigerant is easily discharged to the outside of the second heat source heat exchanger. As a result, in the refrigeration cycle apparatus of the eighth aspect, the time required to defrost the second heat source heat exchanger can be shortened and the amount of frost remaining in the second heat source heat exchanger can be reduced.

[0022] A refrigeration cycle apparatus according to a ninth aspect is the refrigeration cycle apparatus according to either the seventh or eighth aspect, wherein the predetermined condition is that defrosting of the second heat source heat exchanger is not completed within a predetermined time.

[0023] From the viewpoint of defrosting efficiency, it is preferable not to open the first valve or the bypass valve unnecessarily large. However, if liquid refrigerant accumulates in the second heat source heat exchanger, as described above, the time required for defrosting may be prolonged or some frost may remain unmelted.

[0024] In the refrigeration cycle device of the ninth aspect, if defrosting is not completed within a specified time, the opening degree of the first valve and the bypass valve is increased, thereby preventing a decrease in defrosting efficiency while preventing the defrosting time from being extended or frost from remaining unmelted.

[0025] 1 is a diagram showing a schematic refrigerant circuit of an air conditioner as one embodiment of the refrigeration cycle apparatus of the present disclosure. It is a block diagram showing the electrical connections between a control unit of the air conditioner of FIG. 1 and various components. It is a diagram explaining an example of the arrangement of a first heat source heat exchanger and a second heat source heat exchanger of the air conditioner of FIG. 1. It is a diagram showing the state of the refrigerant circuit during cooling operation in the air conditioner of FIG. 1, in which cooling operation is performed using both the first heat source heat exchanger and the second heat source heat exchanger as radiators. It is a diagram showing the state of the refrigerant circuit during first heating operation in the air conditioner of FIG. 1, in which heating operation is performed using both the first heat source heat exchanger and the second heat source heat exchanger as evaporators. It is a diagram showing the state of the refrigerant circuit during second heating operation in the air conditioner of FIG. 1, in which heating operation is performed using the second heat source heat exchanger as an evaporator while defrosting the first heat source heat exchanger (state of the refrigerant circuit during first defrost operation). 1 is a diagram showing the state of the refrigerant circuit during third heating operation (state of the refrigerant circuit during second defrost operation) in the air conditioning apparatus of FIG. 1 , in which heating operation is performed using the first heat source heat exchanger as an evaporator while defrosting the second heat source heat exchanger. FIG. 1 is a diagram for explaining the operating states of various devices when the operation of the air conditioning apparatus of FIG. 1 is switched between first heating operation, first defrost operation (second heating operation), second defrost operation (third heating operation), and first heating operation in this order. FIG. 1 is a diagram showing a schematic refrigerant circuit of an air conditioning apparatus as an embodiment of a refrigeration cycle apparatus of Modification D. FIG. 1 is a diagram showing a schematic refrigerant circuit of an air conditioning apparatus as an embodiment of a refrigeration cycle apparatus of Modification E. FIG. 1 is a diagram showing a schematic refrigerant circuit of an air conditioning apparatus as an embodiment of a refrigeration cycle apparatus of Modification F. FIG. 1 is a diagram showing a schematic refrigerant circuit of an air conditioning apparatus as an embodiment of a refrigeration cycle apparatus of Modification G.

[0026] (1) Configuration of the Air Conditioning Apparatus An overview of an air conditioning apparatus 100, which is one embodiment of the refrigeration cycle apparatus of the present disclosure, will be described with reference to the drawings. Fig. 1 is a diagram showing a schematic refrigerant circuit of the air conditioning apparatus 100. Fig. 2 is a block diagram showing the electrical connections between a control unit 90 of the air conditioning apparatus 100 and various components of the air conditioning apparatus 100.

[0027] The air conditioning apparatus 100 is an apparatus that performs heating and cooling of the interior of a building or the like by performing a vapor compression refrigeration cycle operation. Note that the refrigeration cycle operation of the present disclosure is not limited to air conditioning apparatuses. For example, the refrigeration cycle apparatus may be an apparatus that adjusts the temperature of a liquid such as water, such as a water heater or a floor heating apparatus.

[0028] The air conditioning apparatus 100 mainly has one heat source unit 10, multiple utilization units 50a, 50b, and refrigerant communication pipes 32, 34, 36 that connect the heat source unit 10 and the utilization units 50a, 50b. Note that while Fig. 1 depicts two utilization units 50a, 50b, Fig. 1 does not limit the number of utilization units 50a, 50b, and the number of utilization units may be three or more, or may be one.

[0029] The refrigerant circuit 40 of the air conditioning apparatus 100 is configured by connecting the heat source unit 10 and the utilization units 50a, 50b by refrigerant communication pipes 32, 34, 36. In the air conditioning apparatus 100 of this embodiment, each utilization unit 50a, 50b can also perform cooling operation or heating operation independently.

[0030] An appropriate refrigerant is used in the refrigerant circuit 40. For example, the refrigerant may be an HFC refrigerant such as R32, an HFO refrigerant, or a natural refrigerant such as CO2. In this embodiment, the following description will be given taking the case where the refrigerant is R32 as an example.

[0031] (1-1) Utilization Units The utilization units 50 a and 50 b are connected to the heat source unit 10 via refrigerant communication pipes 32 , 34 , and 36 , and form part of the refrigerant circuit 40 .

[0032] The utilization units 50a, 50b cool / heat the air in the space to be air-conditioned, which is the temperature adjustment target, using a refrigerant, thereby cooling / heating the space to be air-conditioned.

[0033] The utilization units 50a and 50b are installed, for example, indoors (spaces to be air-conditioned) in a building, etc. The type of the utilization units 50a and 50b is not particularly limited, and various types can be used, such as a ceiling-embedded type, a ceiling-suspended type, a wall-mounted type, and a floor-standing type.

[0034] The utilization unit 50a has a utilization heat exchanger 52a, a utilization expansion valve 54a, a utilization fan 56a, and a utilization control unit 94a. The utilization unit 50b has a utilization heat exchanger 52b, a utilization expansion valve 54b, a utilization fan 56b, and a utilization control unit 94b. The utilization units 50a and 50b are similar devices.

[0035] (1-1-1) Utilization Heat Exchanger The utilization heat exchangers 52a and 52b are, for example, fin-and-tube heat exchangers configured with a large number of heat transfer tubes and fins.

[0036] One end (liquid side) of the utilization heat exchanger 52a is connected via piping to the liquid refrigerant connection pipe 32, and the other end (gas side) is connected via piping to the gas refrigerant connection pipe 34. One end (liquid side) of the utilization heat exchanger 52b is connected via piping to the liquid refrigerant connection pipe 32, and the other end (gas side) is connected via piping to the gas refrigerant connection pipe 36.

[0037] In the utilization heat exchangers 52a and 52b, heat is exchanged between the refrigerant flowing through the utilization heat exchangers 52a and 52b and the air in the space to be air-conditioned.

[0038] The utilization heat exchanger 52a functions as a refrigerant heat radiator (condenser) or an evaporator (heat absorber) depending on the piping connection state of a third switching valve 16c (described later). The utilization heat exchanger 52b functions as a refrigerant heat radiator (condenser) or an evaporator (heat absorber) depending on the piping connection state of a fourth switching valve 16d (described later).

[0039] (1-1-2) Use Expansion Valve The use expansion valve 54a is arranged in the piping connecting the use heat exchanger 52a and the liquid refrigerant communication pipe 32 (the piping on the use heat exchanger 52a side from the branching part where the piping connected to the liquid refrigerant communication pipe 32 branches). The use expansion valve 54b is arranged in the piping connecting the use heat exchanger 52b and the liquid refrigerant communication pipe 32 (the piping on the use heat exchanger 52b side from the branching part where the piping connected to the liquid refrigerant communication pipe 32 branches).

[0040] The utilization expansion valves 54a, 54b are electrically operated valves with adjustable openings. The utilization expansion valves 54a, 54b adjust the flow rate of the refrigerant. The utilization expansion valves 54a, 54b also reduce the pressure (expand) the refrigerant passing through them depending on their openings.

[0041] (1-1-3) Usage Fans The usage fans 56a, 56b are fans that supply air to the corresponding usage heat exchangers 52a, 52b in order to promote heat exchange between the air and the refrigerant in the corresponding usage heat exchangers 52a, 52b. The usage fans 56a, 56b are fans with variable rotation speeds. The type of fan used as the usage fans 56a, 56b may be selected as appropriate.

[0042] The utilization fan 56a is provided corresponding to the utilization heat exchanger 52a (so as to supply air to the utilization heat exchanger 52a), and the utilization fan 56b is provided corresponding to the utilization heat exchanger 52b (so as to supply air to the utilization heat exchanger 52b).

[0043] The utilization fan 56a draws in air from the space to be air-conditioned of the utilization unit 50a and supplies the drawn-in air to the utilization heat exchanger 52a. The air that has exchanged heat with the refrigerant in the utilization heat exchanger 52a is blown out from the utilization unit 50a into the space to be air-conditioned of the utilization unit 50a.

[0044] The utilization fan 56b draws in air from the space to be air-conditioned of the utilization unit 50b and supplies the drawn-in air to the utilization heat exchanger 52b. The air that has exchanged heat with the refrigerant in the utilization heat exchanger 52b is blown out from the utilization unit 50b into the space to be air-conditioned of the utilization unit 50b.

[0045] (1-1-4) Usage Control Unit The usage control unit 94a is a control device that controls the usage unit 50a, and the usage control unit 94b is a control device that controls the usage unit 50b. The usage control units 94a and 94b mainly have a CPU (processor) and a memory.

[0046] The usage control unit 94a is electrically connected to the usage expansion valve 54a and the usage fan 56a. The usage control unit 94a is also electrically connected to various sensors, such as a temperature sensor (not shown), installed in the usage unit 50a, and acquires measurement values ​​from the sensors. The usage control unit 94b is electrically connected to the usage expansion valve 54b and the usage fan 56b. The usage control unit 94b is also electrically connected to various sensors, such as a temperature sensor (not shown), installed in the usage unit 50b, and acquires measurement values ​​from the sensors.

[0047] The usage control units 94 a and 94 b are communicably connected to a heat source control unit 92 , which will be described later, and function as a control unit 90 that controls the operation of the air conditioning apparatus 100 together with the heat source control unit 92 .

[0048] The control of the various devices of the air conditioner 100 by the control unit 90 will be explained in the explanation of the operation of the air conditioner 100.

[0049] (1-2) Heat Source Unit The refrigeration cycle device of the present disclosure has a plurality of heat source heat exchangers that can be individually switched between a state where they function as a refrigerant radiator (condenser) and a state where they function as a refrigerant evaporator (heat absorber). In particular, the heat source unit 10 of the air conditioning device 100 has two heat source heat exchangers (a first heat source heat exchanger 18a and a second heat source heat exchanger 18b) that can individually switch between a state where they function as a refrigerant radiator and a state where they function as a refrigerant evaporator.

[0050] The heat source unit 10 mainly includes a compressor 12, a first switching valve 16a, a second switching valve 16b, a third switching valve 16c, a fourth switching valve 16d, a first heat source heat exchanger 18a, a second heat source heat exchanger 18b, a first heat source expansion valve 20a, a second heat source expansion valve 20b, a subcooling heat exchanger 22, a subcooling valve 24, a liquid stop valve 26, gas stop valves 28a, 28b, an accumulator 14, a first heat source fan 17a, a second heat source fan 17b, and a heat source control unit 92. These components of the heat source unit 10 are housed in a casing 10a of the heat source unit 10.

[0051] The compressor 12, the first switching valve 16a, the second switching valve 16b, the third switching valve 16c, the fourth switching valve 16d, the first heat source heat exchanger 18a, the second heat source heat exchanger 18b, the first heat source expansion valve 20a, the second heat source expansion valve 20b, the subcooling heat exchanger 22, the subcooling valve 24, the liquid stop valve 26, the gas stop valves 28a and 28b, and the accumulator 14 are devices that make up the refrigerant circuit 40. These devices that make up the refrigerant circuit 40 are connected within the heat source unit 10 by pipes P1 to P6 as follows.

[0052] A discharge port 12b of the compressor 12, from which the refrigerant compressed by the compressor 12 is discharged, is connected to each of the first to fourth switching valves 16a to 16d via a discharge pipe P2 that branches into a plurality of outlets.

[0053] It is preferable that a sound-absorbing member 25 be provided on the discharge pipe P2 to prevent noise caused by the operation of the first switching valve 16a and the second switching valve 16b from propagating to the utilization units 50a and 50b. The discharge pipe P2 constitutes part of the piping (discharge pipe P2 and refrigerant connection pipes 34 and 36) connecting the first switching valve 16a and the second switching valve 16b with the utilization heat exchangers 52a and 52b. In other words, the discharge pipe P2 is an example of the piping connecting the first switching valve 16a and the second switching valve 16b with the utilization heat exchangers 52a and 52b. The sound-absorbing member 25 is, for example, a muffler having an expanded section. Only one muffler serving as the sound-absorbing member 25 is provided downstream (toward the utilization units 50a and 50b) of a position where the discharge pipe P2 extending from the discharge port 12b of the compressor 12 to the first to fourth switching valves 16a to 16d branches into a pipe extending to the first switching valve 16a and a pipe extending to the second switching valve 16b, and upstream (toward the compressor 12) of a position where the discharge pipe P2 branches into a pipe extending to the third switching valve 16c and a pipe extending to the fourth switching valve 16d (see FIG. 1). In another example, one muffler serving as the sound-absorbing member 25 may be provided in each of the pipes extending to the third switching valve 16c and the fourth switching valve 16d (not shown). Alternatively, mufflers serving as the silencing members 25 may be provided on the gas refrigerant communication pipes 34, 36, which are an example of pipes connecting the first and second switching valves 16a, 16b to the heat utilization exchangers 52a, 52b, respectively.

[0054] Furthermore, the sound-absorbing member 25 may not be a muffler, but may be a weight attached to the discharge pipe P2 or the gas refrigerant communication pipes 34, 36. By attaching weights to the discharge pipe P2 or the gas refrigerant communication pipes 34, 36, noise caused by the operation of the first switching valve 16a and the second switching valve 16b is less likely to propagate to the utilization units 50a, 50b.

[0055] The suction port 12a of the compressor 12, into which the refrigerant to be compressed by the compressor 12 flows, is connected to the first to fourth switching valves 16a to 16d via a suction pipe P1 that branches into multiple branches. One end of a bypass pipe P6, which will be described later, is connected to the suction pipe P1. An accumulator 14 is installed in the suction pipe P1. The accumulator 14 is located in a portion of the suction pipe P1 where a total of four pipes extending from the first to fourth switching valves 16a to 16d join together to form a single pipe that is connected to the suction port 12a of the compressor 12. The accumulator 14 is also located in the suction pipe P1 closer to the suction port 12a of the compressor 12 than the position where the bypass pipe P6 joins the suction pipe P1.

[0056] The first switching valve 16a and one end (gas side) of the first heat source heat exchanger 18a are connected via a first gas pipe P3a, and the second switching valve 16b and one end (gas side) of the second heat source heat exchanger 18b are connected via a first gas pipe P3b.

[0057] The other end (liquid side) of the first heat source heat exchanger 18a and the other end (liquid side) of the second heat source heat exchanger 18b are connected to a liquid shutoff valve 26 via a liquid pipe P4. One end of the liquid pipe P4 is connected to the liquid shutoff valve 26, and the other end branches into two liquid pipes P4a and P4b. One end of the liquid pipe P4a (the end opposite the branching point from the liquid pipe P4) is connected to the first heat source heat exchanger 18a, and one end of the liquid pipe P4b (the end opposite the branching point from the liquid pipe P4) is connected to the second heat source heat exchanger 18b. A first heat source expansion valve 20a is disposed in the liquid pipe P4a. A second heat source expansion valve 20b is disposed in the liquid pipe P4b.

[0058] The liquid pipe P4 is connected to one end of a bypass pipe P6, the other end of which is connected to the suction pipe P1 as described above. The bypass pipe P6 is connected to the liquid pipe P4 between the first heat source heat exchanger 18a and the second heat source heat exchanger 18b (described later) and the subcooling heat exchanger 22. The subcooling heat exchanger 22 is disposed so as to straddle the liquid pipe P4 and the bypass pipe P6. In other words, the subcooling heat exchanger 22 is disposed between the liquid pipe P4 and the bypass pipe P6 so that the refrigerant flowing through the liquid pipe P4 and the refrigerant flowing through the bypass pipe P6 flow into the subcooling heat exchanger 22, and the refrigerant flowing from the liquid pipe P4 and the refrigerant flowing from the bypass pipe P6 exchange heat with each other.

[0059] The third switching valve 16c and the gas shutoff valve 28a are connected via a second gas pipe P5a, and the fourth switching valve 16d and the gas shutoff valve 28b are connected via a second gas pipe P5b.

[0060] Various configurations of the heat source unit 10 will be described below.

[0061] (1-2-1) Compressor The compressor 12 is a device that compresses the refrigerant using a compression mechanism (not shown). The compressor 12 is an inverter compressor with a variable capacity (with a variable motor rotation speed). The compressor 12 is, for example, a positive displacement compressor such as a scroll type, but the type of compressor may be determined as appropriate.

[0062] The compressor 12 has a suction port 12 a and a discharge port 12 b. The compressor 12 compresses low-pressure gas refrigerant drawn from a suction pipe P1 through the suction port 12 a using a compression mechanism, and discharges the compressed high-pressure gas refrigerant into a discharge pipe P2 through the discharge port 12 b.

[0063] (1-2-2) First Switching Valve and Second Switching Valve The first switching valve 16a is a flow path switching mechanism that switches the direction of the refrigerant flowing through the first heat source heat exchanger 18a. The first switching valve 16a is an example of the first switching mechanism or the second switching mechanism set forth in the claims.

[0064] The second switching valve 16b is a flow path switching mechanism that switches the direction of the refrigerant flowing through the second heat source heat exchanger 18b. The second switching valve 16b is an example of a first switching mechanism or a second switching mechanism in the claims.

[0065] In this embodiment, an example will be described in which the first heat source heat exchanger 18a corresponds to the first heat source heat exchanger in the claims, the second heat source heat exchanger 18b corresponds to the second heat source heat exchanger in the claims, the first switching valve 16a corresponds to the first switching mechanism in the claims, and the second switching valve 16b corresponds to the second switching mechanism in the claims.

[0066] However, without being limited to this, the first heat source heat exchanger 18a may be interpreted as corresponding to the second heat source heat exchanger in the claims, the second heat source heat exchanger 18b may be interpreted as corresponding to the first heat source heat exchanger in the claims, the first switching valve 16a may be interpreted as corresponding to the second switching mechanism in the claims, and the second switching valve 16b may be interpreted as corresponding to the first switching mechanism in the claims.

[0067] The first switching valve 16a switches between a state in which the refrigerant discharged from the discharge port 12b of the compressor 12 flows into the first heat source heat exchanger 18a and functions as a radiator, and a state in which the refrigerant that has passed through the first heat source heat exchanger 18a and functions as an evaporator flows into the suction port 12a of the compressor 12.

[0068] In this embodiment, the first switching valve 16a is a four-way switching valve in which one of four ports is blocked (see FIG. 1). In FIG. 1, a black circle attached to one of the ports of the first switching valve 16a indicates a blocked port. When the first heat source heat exchanger 18a functions as a refrigerant radiator, the first switching valve 16a connects the first gas pipe P3a to the discharge pipe P2 (see the solid line in the first switching valve 16a in FIG. 1). When the first heat source heat exchanger 18a functions as a refrigerant evaporator, the first switching valve 16a connects the first gas pipe P3a to the suction pipe P1 (see the dashed line in the first switching valve 16a in FIG. 1).

[0069] The second switching valve 16b switches between a state in which the refrigerant discharged from the discharge port 12b of the compressor 12 flows into the second heat source heat exchanger 18b and functions as a radiator, and a state in which the refrigerant that has passed through the second heat source heat exchanger 18b and functions as an evaporator flows into the suction port 12a of the compressor 12.

[0070] The second switching valve 16b is a four-way switching valve in which one of four ports is closed (see FIG. 1). In FIG. 1, a black circle attached to one of the ports of the second switching valve 16b indicates a closed port. When the second heat source heat exchanger 18b functions as a refrigerant radiator, the second switching valve 16b connects the first gas pipe P3b to the discharge pipe P2 (see the solid line in the second switching valve 16b in FIG. 1). When the second heat source heat exchanger 18b functions as a refrigerant evaporator, the second switching valve 16b connects the first gas pipe P3b to the suction pipe P1 (see the dashed line in the second switching valve 16b in FIG. 1).

[0071] The first and second switching mechanisms in the claims do not have to be four-way switching valves with one of four ports blocked, like the first and second switching valves 16a and 16b. As long as they are capable of switching the refrigerant flow path as described above, the first and second switching valves 16a and 16b may be flow path switching mechanisms configured by connecting multiple valves and pipes. Furthermore, the first and second switching valves 16a and 16b may be three-way valves.

[0072] (1-2-3) Third switching valve and fourth switching valve The third switching valve 16c is a flow path switching mechanism that switches between a state in which the refrigerant discharged from the discharge port 12b of the compressor 12 flows into the utilization heat exchanger 52a and functions as a radiator, and a state in which the refrigerant that has passed through the utilization heat exchanger 52a and functions as an evaporator flows into the suction port 12a of the compressor 12.

[0073] In this embodiment, the third switching valve 16c is a four-way switching valve in which one of four ports is blocked (see FIG. 1). In FIG. 1, a black circle attached to one of the ports of the third switching valve 16c indicates a blocked port. When the utilization heat exchanger 52a functions as a refrigerant radiator, the third switching valve 16c connects the second gas pipe P5a to the discharge pipe P2 (see the dashed line in the third switching valve 16c in FIG. 1). When the utilization heat exchanger 52a functions as a refrigerant evaporator, the third switching valve 16c connects the second gas pipe P5a to the suction pipe P1 (see the solid line in the third switching valve 16c in FIG. 1).

[0074] The fourth switching valve 16d is a flow path switching mechanism that switches between a state in which the refrigerant discharged from the discharge port 12b of the compressor 12 flows into the utilization heat exchanger 52b and functions as a radiator, and a state in which the refrigerant that has passed through the utilization heat exchanger 52b and functions as an evaporator flows into the intake port 12a of the compressor 12.

[0075] In this embodiment, the fourth switching valve 16d is a four-way switching valve in which one of four ports is closed (see FIG. 1). In FIG. 1, a black circle attached to one of the ports of the fourth switching valve 16d indicates a closed port. When the utilization heat exchanger 52b functions as a refrigerant radiator, the fourth switching valve 16d connects the second gas pipe P5b to the discharge pipe P2 (see the dashed line in the fourth switching valve 16d in FIG. 1). When the utilization heat exchanger 52b functions as a refrigerant evaporator, the fourth switching valve 16d connects the second gas pipe P5b to the suction pipe P1 (see the solid line in the fourth switching valve 16d in FIG. 1).

[0076] Although the third switching valve 16c and the fourth switching valve 16d are here four-way switching valves in which one of the four ports is blocked, if it is possible to switch the refrigerant flow path as described above, a flow path switching mechanism consisting of multiple valves and piping connected together may be used instead of such a four-way switching valve.

[0077] (1-2-4) First Heat Source Heat Exchanger and Second Heat Source Heat Exchanger The first heat source heat exchanger 18a and the second heat source heat exchanger 18b are, for example, fin-and-tube heat exchangers configured with a large number of heat transfer tubes and fins.

[0078] 3, a single heat exchanger is divided into two sections, an upper section and a lower section (the heat exchanger is divided into two sections so that the refrigerant flowing through the upper heat transfer tube does not directly communicate with the refrigerant flowing through the lower heat transfer tube), and the upper section is used as the first heat source heat exchanger 18a, and the lower section is used as the second heat source heat exchanger 18b. For example, one end of the upper heat transfer tube functioning as the first heat source heat exchanger 18a is connected to a header pipe that communicates with the first gas pipe P3a, and the other end of the upper heat transfer tube functioning as the first heat source heat exchanger 18a is connected to a header pipe that communicates with the liquid pipe P4a. 3 shows conceptually an example of the shape and structure of the first heat source heat exchanger 18a and the second heat source heat exchanger 18b (heat exchangers used as the first heat source heat exchanger 18a and the second heat source heat exchanger 18b), and the shape and structure of the first heat source heat exchanger 18a and the second heat source heat exchanger 18b (heat exchangers used as the first heat source heat exchanger 18a and the second heat source heat exchanger 18b) may be selected as appropriate.

[0079] Furthermore, the first heat source heat exchanger 18a and the second heat source heat exchanger 18b may be heat exchangers independent of each other, or the first heat source heat exchanger 18a may be placed on top of the second heat source heat exchanger 18b.

[0080] Furthermore, the first heat source heat exchanger 18a and the second heat source heat exchanger 18b are heat exchangers independent of each other, and the first heat source heat exchanger 18a and the second heat source heat exchanger 18b may be arranged horizontally or side by side, front to back.

[0081] In this embodiment, the volume of the first heat source heat exchanger 18a (the internal volume of the heat transfer tubes that constitute the first heat source heat exchanger 18a) is equal to the volume of the second heat source heat exchanger 18b (the internal volume of the heat transfer tubes that constitute the first heat source heat exchanger 18a).

[0082] However, the volumes of the first heat source heat exchanger 18a and the second heat source heat exchanger 18b do not have to be the same. However, by making the volumes of the first heat source heat exchanger 18a and the second heat source heat exchanger 18b the same or by making the volumes of the first heat source heat exchanger 18a and the second heat source heat exchanger 18b similar, as described below, when one of the first heat source heat exchanger 18a and the second heat source heat exchanger 18b is used as an evaporator for heating while the other of the first heat source heat exchanger 18a and the second heat source heat exchanger 18b is used as a radiator for defrosting operation, it is possible to prevent the heat source heat exchangers 18a and 18b from becoming larger and to prevent insufficient capacity from occurring.

[0083] (1-2-5) First Heat Source Fan and Second Heat Source Fan The first heat source fan 17a is a fan that mainly supplies air to the first heat source heat exchanger 18a in order to promote heat exchange between the air and the refrigerant in the corresponding first heat source heat exchanger 18a. The second heat source fan 17b is a fan that mainly supplies air to the second heat source heat exchanger 18b in order to promote heat exchange between the air and the refrigerant in the corresponding second heat source heat exchanger 18b. The first heat source fan 17a and the second heat source fan 17b are variable rotation speed fans whose rotation speed can be changed according to the desired air volume. The types of fans used as the first heat source fan 17a and the second heat source fan 17b may be selected as appropriate.

[0084] The first heat source fan 17a draws in air from the space to be air-conditioned outside the casing 10a and supplies the drawn-in air mainly to the first heat source heat exchanger 18a. The air that has exchanged heat with the refrigerant in the first heat source heat exchanger 18a is blown out of the casing 10a.

[0085] The second heat source fan 17b draws in air from the space to be air-conditioned outside the casing 10a and supplies the drawn-in air mainly to the second heat source heat exchanger 18b. The air that has exchanged heat with the refrigerant in the second heat source heat exchanger 18b is blown out of the casing 10a.

[0086] In this embodiment, the first heat source fan 17a is provided corresponding to the first heat source heat exchanger 18a, and the second heat source fan 17b is provided corresponding to the second heat source heat exchanger 18b, but this is not limited to this. For example, instead of providing two heat source fans in the air conditioning apparatus 100, a single heat source fan shared by the first heat source heat exchanger 18a and the second heat source heat exchanger 18b may be provided.

[0087] (1-2-6) First heat source expansion valve and second heat source expansion valve The first heat source expansion valve 20a is an example of the first valve or the second valve in the claims, and the second heat source expansion valve 20b is an example of the second valve or the first valve in the claims.

[0088] In this embodiment, the first heat source heat exchanger 18a corresponds to the first heat source heat exchanger in the claims, the second heat source heat exchanger 18b corresponds to the second heat source heat exchanger in the claims, the first heat source expansion valve 20a corresponds to the first valve in the claims, and the second heat source expansion valve 20b corresponds to the second valve in the claims. However, this is not limited to this, and it may be interpreted as the first heat source heat exchanger 18a corresponds to the second heat source heat exchanger in the claims, the second heat source heat exchanger 18b corresponds to the first heat source heat exchanger in the claims, the first heat source expansion valve 20a corresponds to the second valve in the claims, and the second heat source expansion valve 20b corresponds to the first valve in the claims.

[0089] The first heat source expansion valve 20a is disposed on the liquid pipe P4a, and the second heat source expansion valve 20b is disposed on the liquid pipe P4b.

[0090] The first heat source expansion valve 20a and the second heat source expansion valve 20b are motor-operated valves with adjustable openings. The first heat source expansion valve 20a and the second heat source expansion valve 20b directly adjust the flow rate of the refrigerant. Furthermore, the first heat source expansion valve 20a and the second heat source expansion valve 20b decompress (expand) the refrigerant passing through them depending on their openings.

[0091] (1-2-7) Subcooling Heat Exchanger and Subcooling Valve As described above, the subcooling heat exchanger 22 is disposed in the liquid pipe P4 and the bypass pipe P6, and exchanges heat between the refrigerant flowing through the bypass pipe P6 and the refrigerant flowing through the liquid pipe P4, thereby cooling (subcooling) the refrigerant flowing through the liquid pipe P4 with the refrigerant flowing through the bypass pipe P6.

[0092] The subcooling valve 24 is disposed in the bypass pipe P6. Specifically, the subcooling valve 24 is disposed in the bypass pipe P6 between the connection between the bypass pipe P6 and the liquid pipe P4 and the connection between the bypass pipe P6 and the subcooling heat exchanger 22. The subcooling valve 24 adjusts the flow rate of the refrigerant flowing from the bypass pipe P6 into the subcooling heat exchanger 22, and also reduces the pressure of (expands) the refrigerant passing through the subcooling valve 24.

[0093] (1-2-8) Accumulator The accumulator 14 is disposed in the suction pipe P1. The accumulator 14 captures and stores therein liquid refrigerant mixed in with the refrigerant flowing in from the suction pipe P1, thereby preventing the liquid refrigerant from flowing into the suction port 12a of the compressor 12. The gas refrigerant that has flowed into the accumulator 14 passes through the accumulator 14 and flows through the suction pipe P1 into the suction port 12a of the compressor 12.

[0094] (1-2-9) Liquid Shut-Off Valve and Gas Shut-Off Valve The liquid shut-off valve 26 is a shut-off valve that cuts off one end of the liquid pipe P4. The gas shut-off valve 28a is a shut-off valve that is connected to one end of the second gas pipe P5a. The gas shut-off valve 28b is a shut-off valve that is connected to one end of the second gas pipe P5b.

[0095] Furthermore, a liquid refrigerant communication pipe 32 is connected to the liquid shutoff valve 26. A gas refrigerant communication pipe 34 is connected to the gas shutoff valve 28a. A gas refrigerant communication pipe 36 is connected to the gas shutoff valve 28b. The liquid shutoff valve 26, the gas shutoff valve 28a, and the gas shutoff valve 28b are valves that are opened and closed manually, and are normally open.

[0096] (1-2-10) Heat Source Control Unit The heat source control unit 92 is a control device that controls the heat source unit 10, and mainly includes a CPU (processor) and a memory.

[0097] The heat source control unit 92 is electrically connected to the compressor 12, the first switching valve 16a to the fourth switching valve 16d, the first heat source expansion valve 20a, the first heat source expansion valve 20a, the subcooling valve 24, the first heat source fan 17a, and the second heat source fan 17b. The heat source control unit 92 is also electrically connected to sensors such as pressure sensors and temperature sensors (not shown) installed in the heat source control unit 92, and acquires measurement data from the sensors. The heat source control unit 92 is also communicatively connected to usage control units 94a and 94b, and functions as a control unit 90 that controls the operation of the air conditioning apparatus 100 together with the usage control units 94a and 94b.

[0098] The control of the air conditioner 100 by the control unit 90 will be explained in the explanation of the operation of the air conditioner 100.

[0099] (2) Operation of the Air Conditioning Apparatus The operation of the air conditioning apparatus 100 will be briefly described below.

[0100] In addition to the cooling operation, first heating operation, second heating operation, and third heating operation described below, the air conditioning apparatus 100 is also capable of simultaneous cooling and heating operation, in which one of the utilization heat exchangers 52a and 52b is used as a radiator to perform heating, and the other of the utilization heat exchangers 52a and 52b is used as an evaporator to perform cooling. However, to avoid complicating the explanation, a description of simultaneous cooling and heating operation will be omitted here.

[0101] (2-1) Cooling Operation Fig. 4 shows the state of the refrigerant circuit 40 of the air conditioner 100 during cooling operation. In Fig. 4, heat exchangers that function as radiators are hatched, and heat exchangers that function as evaporators are not hatched.

[0102] During cooling operation, the control unit 90 controls the first to fourth switching valves 16a to 16d so that the first switching valve 16a connects the discharge pipe P2 to the first gas pipe P3a, the second switching valve 16b connects the discharge pipe P2 to the first gas pipe P3b, the third switching valve 16c connects the suction pipe P1 to the second gas pipe P5a, and the fourth switching valve 16d connects the suction pipe P1 to the second gas pipe P5b. During cooling operation, the first heat source heat exchanger 18a and the second heat source heat exchanger 18b function as condensers, and the utilization heat exchangers 52a and 52b function as evaporators.

[0103] During cooling operation, the control unit 90 controls the rotation speed of the compressor 12 as appropriate according to the capacity required of the air conditioning apparatus 100. The high-pressure gas refrigerant discharged from the discharge port 12b of the compressor 12 passes through the discharge pipe P2, the first switching valve 16a and the second switching valve 16b, and is condensed as it passes through the first heat source heat exchanger 18a and the second heat source heat exchanger 18b, becoming a high-pressure liquid refrigerant.

[0104] During cooling operation, the control unit 90 controls both the first heat source expansion valve 20 a and the second heat source expansion valve 20 b to be fully open. The control unit 90 also controls the opening degree of the subcooling valve 24 based on the degree of subcooling detected by a sensor (not shown).

[0105] In this specification, the meaning of the word "detection" is not limited to detection by a single sensor, but is also used to include cases where a value is calculated based on the detection results of multiple sensors.

[0106] Most of the high-pressure liquid refrigerant flowing out of the first heat source heat exchanger 18a and the second heat source heat exchanger 18b passes through the liquid pipe P4 and flows into the liquid refrigerant communication pipe 32. A portion of the high-pressure liquid refrigerant flowing out of the first heat source heat exchanger 18a and the second heat source heat exchanger 18b passes through the bypass pipe P6 and flows into the suction pipe P1. The refrigerant flowing from the liquid pipe P4 into the subcooling heat exchanger 22 exchanges heat with the refrigerant flowing into the subcooling heat exchanger 22 from the bypass pipe P6 and is subcooled.

[0107] The high-pressure liquid refrigerant that has passed through the subcooling heat exchanger 22 further flows through the liquid pipe P4 and the liquid refrigerant connection pipe 32, and in the example of Figure 1, flows into the two user units 50a, 50b. The high-pressure liquid refrigerant that has flowed into the user units 50a, 50b is reduced in pressure as it passes through the user expansion valves 54a, 54b, which the control unit 90 controls to an appropriate opening based on the detection results of the sensors, to become a gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant is evaporated in the user heat exchangers 52a, 52b to become low-pressure gas refrigerant, which cools the air in the air-conditioned spaces of the user units 50a, 50b. The low-pressure gas refrigerant that has passed through the user heat exchanger 52a passes through the gas refrigerant connection pipe 34, flows into the second gas pipe P5a, passes through the third switching valve 16c, and flows into the suction pipe P1. The low-pressure gas refrigerant that has passed through the utilization heat exchanger 52b passes through the gas refrigerant communication pipe 36, flows into the second gas pipe P5b, passes through the fourth switching valve 16d, and flows into the suction pipe P1. The low-pressure gas refrigerant that has flowed into the suction pipe P1 passes through the accumulator 14, and is then drawn into the compressor 12 from the suction port 12a.

[0108] (2-2) First Heating Operation The first heating operation is an operation in which both the heat source heat exchangers 18a and 18b are used as evaporators to heat the space to be air-conditioned.

[0109] Fig. 5 shows the state of the refrigerant circuit 40 of the air conditioner 100 during the first heating operation. In Fig. 5, heat exchangers that function as radiators are hatched, and heat exchangers that function as evaporators are not hatched.

[0110] During the first heating operation, the control unit 90 controls the first to fourth switching valves 16a to 16d so that the first switching valve 16a connects the suction pipe P1 to the first gas pipe P3a, the second switching valve 16b connects the suction pipe P1 to the first gas pipe P3b, the third switching valve 16c connects the discharge pipe P2 to the second gas pipe P5a, and the fourth switching valve 16d connects the discharge pipe P2 to the second gas pipe P5b. During the first heating operation, the first heat source heat exchanger 18a and the second heat source heat exchanger 18b function as evaporators, and the utilization heat exchangers 52a and 52b function as radiators.

[0111] During the first heating operation, the control unit 90 appropriately controls the rotation speed of the compressor 12 in accordance with the capacity required of the air conditioning apparatus 100. The high-pressure gas refrigerant discharged from the discharge port 12b of the compressor 12 passes through the discharge pipe P2, the third switching valve 16c, and the fourth switching valve 16d, and is condensed in the utilization heat exchangers 52a, 52b to become high-pressure liquid refrigerant. As the high-pressure gas refrigerant becomes high-pressure liquid refrigerant in the utilization heat exchangers 52a, 52b, the refrigerant heats the air in the air-conditioned spaces of the utilization units 50a, 50b. During the first heating operation, the control unit 90 appropriately controls the openings of the utilization expansion valves 54a, 54b based on detection results from sensors (not shown), etc.

[0112] The high-pressure liquid refrigerant that has passed through the utilization heat exchangers 52a, 52b passes through the liquid refrigerant connection pipe 32 and flows into the heat source unit 10, then flows through the liquid pipe P4. A portion of the high-pressure liquid refrigerant flowing through the liquid pipe P4 flows through the liquid pipe P4a and is decompressed as it passes through the first heat source expansion valve 20a, becoming a two-phase gas-liquid refrigerant, which then flows into the first heat source heat exchanger 18a. The remainder of the high-pressure liquid refrigerant flowing through the liquid pipe P4b and is decompressed as it passes through the second heat source expansion valve 20b, becoming a two-phase gas-liquid refrigerant, which then flows into the second heat source heat exchanger 18b. During the first heating operation, the control unit 90 controls the apertures of the first heat source expansion valve 20a and the second heat source expansion valve 20b based on the detection results of the sensors (e.g., based on the degree of subcooling determined from the detection results of the sensors). The gas-liquid two-phase refrigerant is evaporated in the first heat source heat exchanger 18a and the second heat source heat exchanger 18b to become low-pressure gas refrigerant. The low-pressure gas refrigerant flowing out of the first heat source heat exchanger 18a flows into the first gas pipe P3a, passes through the first switching valve 16a, and flows into the suction pipe P1. The low-pressure gas refrigerant flowing out of the second heat source heat exchanger 18b flows into the first gas pipe P3b, passes through the second switching valve 16b, and flows into the suction pipe P1. The low-pressure gas refrigerant that has flowed into the suction pipe P1 passes through the accumulator 14, and is then drawn into the compressor 12 from the suction port 12a.

[0113] (2-3) Second heating operation (first defrosting operation) Fig. 6 shows the state of the refrigerant circuit 40 of the air conditioning apparatus 100 during the second heating operation. In Fig. 6, heat exchangers that function as radiators are hatched, and heat exchangers that function as evaporators are not hatched.

[0114] The second heating operation is an operation in which the first heat source heat exchanger 18a functions as a condenser to melt frost that has adhered to the first heat source heat exchanger 18a, while the second heat source heat exchanger 18b functions as an evaporator and the utilization heat exchangers 52a, 52b function as condensers to heat the space to be air-conditioned. By performing such an operation, the user of the air conditioning apparatus 100 can continue to use the heating function even while the first heat source heat exchanger 18a is being defrosted. Because the second heating operation also defrosts the first heat source heat exchanger 18a, it is sometimes referred to as the first defrost operation below.

[0115] During the second heating operation, the control unit 90 controls the first to fourth switching valves 16a to 16d so that the first switching valve 16a connects the discharge pipe P2 to the first gas pipe P3a, the second switching valve 16b connects the suction pipe P1 to the first gas pipe P3b, the third switching valve 16c connects the discharge pipe P2 to the second gas pipe P5a, and the fourth switching valve 16d connects the discharge pipe P2 to the second gas pipe P5b. During the second heating operation, the second heat source heat exchanger 18b functions as an evaporator, and the first heat source heat exchanger 18a and the utilization heat exchangers 52a and 52b function as radiators.

[0116] The high-pressure gas refrigerant discharged from the discharge port 12b of the compressor 12 is sent from the discharge pipe P2 to the utilization heat exchangers 52a, 52b, as in the first heating operation, and a portion of the refrigerant passes through the first switching valve 16a and is sent to the first heat source heat exchanger 18a. The high-pressure gas refrigerant that has flowed into the first heat source heat exchanger 18a releases heat in the first heat source heat exchanger 18a, melting frost that has adhered to the first heat source heat exchanger 18a.

[0117] As in the first heating operation, the high-pressure gas refrigerant sent to the utilization heat exchangers 52a, 52b condenses in the utilization heat exchangers 52a, 52b to become high-pressure liquid refrigerant, which heats the air in the space to be air-conditioned. During the second heating operation, the control unit 90 appropriately controls the opening degrees of the utilization expansion valves 54a, 54b based on detection results from sensors (not shown). The high-pressure liquid refrigerant that has passed through the utilization heat exchangers 52a, 52b passes through the liquid refrigerant communication pipe 32, flows into the heat source unit 10, and flows through the liquid pipe P4. The high-pressure liquid refrigerant flowing through the liquid pipe P4 flows through the liquid pipe P4b, and is decompressed as it passes through the second heat source expansion valve 20b, becoming a gas-liquid two-phase refrigerant and flowing into the second heat source heat exchanger 18b.

[0118] In addition, the high-pressure liquid refrigerant flowing out from the first heat source heat exchanger 18a flows through the liquid pipe P4a, then through the liquid pipe P4b, and is reduced in pressure as it passes through the second heat source expansion valve 20b, becoming a gas-liquid two-phase refrigerant and flowing into the second heat source heat exchanger 18b.

[0119] The gas-liquid two-phase refrigerant that has flowed into the second heat source heat exchanger 18b is evaporated in the second heat source heat exchanger 18b to become low-pressure gas refrigerant, which then flows into the first gas pipe P3b, passes through the second switching valve 16b, and flows into the suction pipe P1. The low-pressure gas refrigerant that has flowed into the suction pipe P1 passes through the accumulator 14, and is then drawn into the compressor 12 from the suction port 12a.

[0120] The control of the compressor 12, the first heat source expansion valve 20a, the second heat source expansion valve 20b, the subcooling valve 24, the first heat source fan 17a and the second heat source fan 17b during the second heating operation (first defrost operation) will be described later.

[0121] (2-4) Third heating operation (second defrosting operation) Fig. 7 shows the state of the refrigerant circuit 40 of the air conditioning apparatus 100 during the third heating operation. In Fig. 7, heat exchangers that function as radiators are hatched, and heat exchangers that function as evaporators are not hatched.

[0122] The third heating operation is the opposite of the second heating operation, in that it heats the air-conditioned space by making the first heat source heat exchanger 18a function as an evaporator and making the utilization heat exchangers 52a and 52b function as condensers while performing a defrosting operation in which the second heat source heat exchanger 18b functions as a condenser to melt frost that has adhered to the second heat source heat exchanger 18b. By performing such an operation, the user of the air conditioning apparatus 100 can continue to use the heating function even while the second heat source heat exchanger 18b is being defrosted. Because the third heating operation also defrosts the second heat source heat exchanger 18b, it is sometimes called the second defrosting operation.

[0123] During the third heating operation, the control unit 90 controls the first to fourth switching valves 16a to 16d so that the first switching valve 16a connects the suction pipe P1 to the first gas pipe P3a, the second switching valve 16b connects the discharge pipe P2 to the first gas pipe P3b, the third switching valve 16c connects the discharge pipe P2 to the second gas pipe P5a, and the fourth switching valve 16d connects the discharge pipe P2 to the second gas pipe P5b. During the third heating operation, the first heat source heat exchanger 18a functions as an evaporator, and the second heat source heat exchanger 18b and the utilization heat exchangers 52a and 52b function as radiators.

[0124] The high-pressure gas refrigerant discharged from the discharge port 12b of the compressor 12 is sent from the discharge pipe P2 to the heat utilization exchangers 52a, 52b, as in the first heating operation, and a portion of the refrigerant passes through the second switching valve 16b and is sent to the second heat source heat exchanger 18b. The high-pressure gas refrigerant that has flowed into the second heat source heat exchanger 18b releases heat in the second heat source heat exchanger 18b, melting the frost that has adhered to the second heat source heat exchanger 18b.

[0125] As in the first heating operation, the high-pressure gas refrigerant sent to the utilization heat exchangers 52a, 52b condenses in the utilization heat exchangers 52a, 52b to become high-pressure liquid refrigerant, which heats the air in the space to be air-conditioned. During the third heating operation, the control unit 90 appropriately controls the opening degrees of the utilization expansion valves 54a, 54b based on the detection results of sensors (not shown). The high-pressure liquid refrigerant that has passed through the utilization heat exchangers 52a, 52b passes through the liquid refrigerant communication pipe 32 and flows into the heat source unit 10, and then flows through the liquid pipe P4. The high-pressure liquid refrigerant flowing through the liquid pipe P4 flows through the liquid pipe P4a and is decompressed as it passes through the first heat source expansion valve 20a, becoming a gas-liquid two-phase refrigerant and flowing into the first heat source heat exchanger 18a.

[0126] In addition, the high-pressure liquid refrigerant flowing out from the second heat source heat exchanger 18b flows through the liquid pipe P4b, then through the liquid pipe P4a, and is reduced in pressure as it passes through the first heat source expansion valve 20a, becoming a gas-liquid two-phase refrigerant and flowing into the first heat source heat exchanger 18a.

[0127] The gas-liquid two-phase refrigerant that has flowed into the first heat source heat exchanger 18a is evaporated in the first heat source heat exchanger 18a to become low-pressure gas refrigerant, which then flows into the first gas pipe P3a, passes through the first switching valve 16a, and flows into the suction pipe P1. The low-pressure gas refrigerant that has flowed into the suction pipe P1 passes through the accumulator 14, and is then drawn into the compressor 12 from the suction port 12a.

[0128] The control of the compressor 12, the first heat source expansion valve 20a, the second heat source expansion valve 20b, the subcooling valve 24, the first heat source fan 17a and the second heat source fan 17b during the third heating operation (second defrost operation) will be described later.

[0129] (3) Alternating defrost operation When predetermined defrost conditions are met during the first heating operation, the control unit 90 performs alternating defrost operation in which the air conditioning device 100 performs the first defrost operation (second heating operation) to defrost the first heat source heat exchanger 18a, and then performs the second defrost operation (third heating operation) to defrost the second heat source heat exchanger 18b.

[0130] During the alternating defrost operation, the air conditioning apparatus 100 switches operation without stopping the compressor 12. Therefore, the user can continue to use the heating function while the air conditioning apparatus 100 defrosts the first heat source heat exchanger 18a and the second heat source heat exchanger 18b. The predetermined defrost condition is not limited to, but may be, for example, a condition in which the measurement values ​​of temperature sensors (not shown) provided in the first heat source heat exchanger 18a and the second heat source heat exchanger 18b are below a predetermined temperature for a predetermined period of time. However, the predetermined defrost condition is not limited to, and may be, for example, a condition in which the measurement values ​​of temperature sensors (not shown) provided in the first heat source heat exchanger 18a and the second heat source heat exchanger 18b are below a predetermined temperature or a condition in which the first heating operation has been performed for a predetermined period of time.

[0131] The control of the compressor 12, the first heat source expansion valve 20a, the second heat source expansion valve 20b, the subcooling valve 24, the first heat source fan 17a, and the second heat source fan 17b by the control unit 90 when performing alternate defrost operation will be described, including control during transition states of each operation, with reference to Fig. 8. Fig. 8 is a diagram for explaining the operation of various devices when the operation of the air conditioning apparatus 100 is switched between the first heating operation, the first defrost operation (second heating operation), the second defrost operation (third heating operation), and the first heating operation in this order.

[0132] Note that, here, an example will be described in which the first defrost operation and the second defrost operation are each performed once in the alternating defrost operation, but one of the first defrost operation and the second defrost operation may be performed multiple times in the alternating defrost operation. For example, in the alternating defrost operation, the operation of the air conditioning apparatus 100 may be switched in the following order: first heating operation, second defrost operation (third heating operation), first defrost operation (second heating operation), second defrost operation (third heating operation), and first heating operation.

[0133] Furthermore, in the alternate defrost operation, the operation of the air conditioning apparatus 100 may be switched in the following order: first heating operation, second defrost operation (third heating operation), first defrost operation (second heating operation), and first heating operation. However, when the first heat source heat exchanger 18a is disposed above the second heat source heat exchanger 18b as in Fig. 3, in the alternate defrost operation, it is preferable that the operation of the air conditioning apparatus 100 be switched in the following order: first heating operation, first defrost operation (second heating operation), second defrost operation (third heating operation), and first heating operation.

[0134] (3-1) First Switching Valve and Second Switching Valve During the first heating operation, the first switching valve 16a connects the suction pipe P1 and the first gas pipe P3a. This state is shown as the ON state in Fig. 8. When the defrosting condition is met during the first heating operation, the control unit 90 controls the first switching valve 16a to connect the discharge pipe P2 and the first gas pipe P3a to perform the first defrosting operation. This state is shown as the OFF state in Fig. 8.

[0135] In addition, when the first defrost operation is completed, the control unit 90 controls the first switching valve 16a so that the first switching valve 16a connects the intake pipe P1 and the first gas pipe P3a (to the ON state) in order to start the second defrost operation.

[0136] Note that, although not limited to, the control unit 90 determines that the first defrost operation is completed when, for example, the measurement value of a temperature sensor (not shown) provided in the first heat source heat exchanger 18a exceeds a predetermined temperature for a predetermined period of time. Furthermore, although not limited to, the control unit 90 also terminates the first defrost operation when, for example, the measurement value of the temperature sensor provided in the first heat source heat exchanger 18a does not exceed the predetermined temperature for a predetermined maximum period of time Tmax1.

[0137] In addition, when starting the first heating operation after the second defrost operation has ended, the control unit 90 keeps the first switching valve 16a in the ON state (in other words, the first switching valve 16a is not operated).

[0138] During the first heating operation, the second switching valve 16b connects the intake pipe P1 and the first gas pipe P3b. This state is represented as the ON state in Fig. 8. When the defrosting condition is met during the first heating operation, the air conditioning apparatus 100 performs the first defrosting operation. In this case, the control unit 90 keeps the second switching valve 16b in the ON state (in other words, the second switching valve 16b is not operated).

[0139] When the first defrosting operation ends, the control unit 90 controls the second switching valve 16b to connect the discharge pipe P2 and the first gas pipe P3b to start the second defrosting operation. This state is represented as the OFF state in Fig. 8. Note that, in Fig. 8, the first switching valve 16a and the second switching valve 16b are operated at the same timing, but this is not limited thereto. For example, the control unit 90 may operate the second switching valve 16b at a slightly different timing after the operation of the first switching valve 16a.

[0140] When the second defrost operation is completed, the control unit 90 controls the second switching valve 16b so that the second switching valve 16b connects the intake pipe P1 and the first gas pipe P3a (to the ON state) in order to start the first heating operation.

[0141] Note that, although not limited to, the control unit 90 determines that the second defrost operation is completed when, for example, the measurement value of a temperature sensor (not shown) provided in the second heat source heat exchanger 18b exceeds a predetermined temperature for a predetermined period of time. Also, although not limited to, the control unit 90 also terminates the second defrost operation when, for example, the measurement value of the temperature sensor provided in the second heat source heat exchanger 18b does not exceed the predetermined temperature for a predetermined maximum period of time Tmax1.

[0142] (3-2) Compressor When the defrost condition is met during the first heating operation, the control unit 90 changes the rotation speed of the compressor 12 to a predetermined rotation speed Rc while continuing the operation of the compressor 12. The predetermined rotation speed Rc is a rotation speed that is smaller than the maximum rotation speed Rmax of the compressor 12.

[0143] The maximum rotation speed Rmax of the compressor 12 is defined as follows: In the first heating operation, the control unit 90 changes the rotation speed of the compressor 12 within a predetermined range of rotation speeds in accordance with the required capacity. The maximum value of the rotation speed within this predetermined range of rotation speeds is the maximum rotation speed Rmax.

[0144] In other words, when the defrost condition is met during the first heating operation, the control unit 90 controls the rotation speed of the compressor 12 so that it does not become excessively high while continuing to operate the compressor 12. By performing such control, noise that occurs when the first switching valve 16a is switched from the ON state to the OFF state while the compressor 12 is operating is likely to be suppressed.

[0145] The predetermined rotation speed Rc is preferably a value smaller than half the maximum rotation speed Rmax, and from the viewpoint of noise suppression, it is more preferable that the predetermined rotation speed Rc is 10 to 15% of the maximum rotation speed Rmax.

[0146] Preferably, when the defrost condition is met during the first heating operation, the control unit 90 sets the rotation speed of the compressor 12 to the predetermined rotation speed Rc, and then switches the first switching valve 16a to the OFF state after a predetermined time (e.g., one minute) has elapsed. However, this is not limited to this, and for example, the control unit 90 may switch the first switching valve 16a to the OFF state at the timing when the rotation speed of the compressor 12 is changed to the predetermined rotation speed Rc. Alternatively, for example, the control unit 90 may change the rotation speed of the compressor 12 to the predetermined rotation speed Rc after switching the first switching valve 16a to the OFF state.

[0147] During the first defrost operation, the control unit 90 changes the rotation speed of the compressor 12 to a second rotation speed Rb. To promote defrosting of the first heat source heat exchanger 18a, it is preferable that the second rotation speed Rb be as large as possible. For example, the second rotation speed Rb is a value that is greater than half the maximum rotation speed Rmax and equal to or less than the maximum rotation speed Rmax.

[0148] When the first defrost operation is terminated under the above conditions, the control unit 90 changes the rotation speed of the compressor 12 to a predetermined rotation speed Rc while continuing the operation of the compressor 12 when transitioning to the second defrost operation. As described above, the predetermined rotation speed Rc is a value smaller than the maximum rotation speed Rmax. Preferably, the predetermined rotation speed Rc is a value smaller than half the maximum rotation speed Rmax. From the viewpoint of noise suppression, the predetermined rotation speed Rc is more preferably 10 to 15% of the maximum rotation speed Rmax.

[0149] At the timing of transition from the first defrost operation to the second defrost operation, the air conditioning apparatus 100 changes from a state in which the second heat source heat exchanger 18b functions as an evaporator and the first heat source heat exchanger 18a functions as a radiator to a state in which the second heat source heat exchanger 18b functions as a radiator and the first heat source heat exchanger 18a functions as an evaporator, while continuing to operate the compressor 12. In other words, at the timing of transition from the first defrost operation to the second defrost operation, the compressor 12 is in operation, and both the first switching valve 16a and the second switching valve 16b operate, as shown in FIG. 8 . Therefore, at the timing of transition from the first defrost operation to the second defrost operation, loud noises are likely to be generated due to the switching of the first switching valve 16a and the second switching valve 16b. In contrast, by setting the rotation speed of the compressor 12 to a predetermined rotation speed Rc at the timing of transition from the first defrost operation to the second defrost operation, the noise generated when switching the states of the first switching valve 16a and the second switching valve 16b while the compressor 12 is operating is more likely to be suppressed.

[0150] Furthermore, by providing the sound-absorbing member 25, the sound-absorbing member 25 can also make it difficult for noise generated when the states of the first switching valve 16a and the second switching valve 16b are switched to be transmitted to the space to be air-conditioned.

[0151] 8, the predetermined rotation speed Rc at the timing of transition from the first defrost operation to the second defrost operation and the predetermined rotation speed Rc at the timing of transition from the first heating operation to the first defrost operation are described as being the same value. However, this is not limited to this, and for example, the predetermined rotation speed at the timing of transition from the first defrost operation to the second defrost operation may be a value smaller than the predetermined rotation speed at the timing of transition from the first heating operation to the first defrost operation.

[0152] Preferably, when the first defrost operation is completed, the control unit 90 sets the rotation speed of the compressor 12 to the predetermined rotation speed Rc, and then switches the first switching valve 16a to the ON state and the second switching valve 16b to the OFF state after a predetermined time (e.g., one minute) has elapsed. Note that, when switching from the first defrost operation to the second defrost operation, the control unit 90 may switch the first switching valve 16a to the ON state and the second switching valve 16b to the OFF state after a longer time (e.g., two minutes) has elapsed after the rotation speed of the compressor 12 is set to the predetermined rotation speed Rc, compared to when switching from the first heating operation to the first defrost operation.

[0153] However, the timing of the operation of the first switching valve 16a and the second switching valve 16b is not limited to the above-described embodiment, and for example, the control unit 90 may switch the first switching valve 16a and the second switching valve 16b to the OFF state at the timing when the rotation speed of the compressor 12 is changed to the predetermined rotation speed Rc. Alternatively, for example, the control unit 90 may change the rotation speed of the compressor 12 to the predetermined rotation speed Rc after switching the first switching valve 16a and the second switching valve 16b to the OFF state.

[0154] During the second defrosting operation, the control unit 90 changes the rotation speed of the compressor 12 to a first rotation speed Ra. To promote defrosting of the first heat source heat exchanger 18a, it is preferable that the first rotation speed Ra be as large as possible. For example, the first rotation speed Ra is a value that is greater than the second rotation speed Rb and equal to or less than the maximum rotation speed Rmax.

[0155] Note that making the first rotation speed Ra greater than the second rotation speed Rb provides the following effect. When the second heat source heat exchanger 18b is disposed below the first heat source heat exchanger 18a, as in this embodiment, there is a risk that water used for defrosting the first heat source heat exchanger 18a may get on the second heat source heat exchanger 18b and freeze. Therefore, defrosting the second heat source heat exchanger 18b tends to require a larger amount of heat than defrosting the first heat source heat exchanger 18a. In contrast, making the first rotation speed Ra greater than the second rotation speed Rb makes it easier to reliably defrost the second heat source heat exchanger 18b as well.

[0156] However, the present invention is not limited to this, and the first rotation speed Ra and the second rotation speed Rb may be the same value.

[0157] When the second defrosting operation is terminated under the above conditions, the control unit 90 changes the rotation speed of the compressor 12 to the predetermined rotation speed Rc while continuing the operation of the compressor 12 when transitioning to the first heating operation. The predetermined rotation speed Rc is as described above.

[0158] Preferably, when the second defrost operation ends, the control unit 90 sets the rotation speed of the compressor 12 to the predetermined rotation speed Rc, and then switches the second switching valve 16b to the ON state after a predetermined time (e.g., one minute) has elapsed. However, this is not limited to this, and for example, the control unit 90 may switch the second switching valve 16b to the ON state at the timing when the rotation speed of the compressor 12 is changed to the predetermined rotation speed Rc. Alternatively, for example, the control unit 90 may change the rotation speed of the compressor 12 to the predetermined rotation speed Rc after switching the second switching valve 16b to the ON state.

[0159] (3-3) First heat source expansion valve and second heat source expansion valve During the first heating operation, as described above, the control unit 90 controls the opening degree of the first heat source expansion valve 20a and the second heat source expansion valve 20b, for example, depending on the degree of subcooling.

[0160] When the defrost condition is met, the control unit 90 changes the opening degree of the first heat source expansion valve 20a to an opening degree Op12 and the opening degree of the second heat source expansion valve 20b to an opening degree Op22 while continuing the operation of the compressor 12. The opening degrees Op12 and Op22 may be maximum opening degrees.

[0161] When the operation mode shifts to the first defrosting operation, the control unit 90 changes the opening degree of the first heat source expansion valve 20a corresponding to the first heat source heat exchanger 18a where defrosting is performed to the opening degree Op11. The opening degree Op11 is preferably as large as possible. The opening degree Op11 will be specifically described.

[0162] When the first heat source heat exchanger 18a is used as an evaporator (in other words, when the air conditioning apparatus 100 performs the first heating operation or the third heating operation using the first heat source heat exchanger 18a as an evaporator), the control unit 90 controls the opening degree of the first heat source expansion valve 20a within a predetermined opening degree range. Preferably, the opening degree Op11 is larger than this predetermined opening degree range. In other words, the opening degree Op11 is larger than the opening degree of the first heat source expansion valve 20a when the first heat source heat exchanger 18a is used as an evaporator. The opening degree Op11 may be the maximum opening degree that the first heat source expansion valve 20a can have.

[0163] In addition, when the control unit 90 transitions to the first defrost operation, it controls the opening degree of the second heat source expansion valve 20b corresponding to the second heat source heat exchanger 18b, which functions as an evaporator, basically within a range not exceeding 1 / 2 of the maximum possible opening degree, for example, according to the degree of subcooling, etc. (see solid line in Figure 8).

[0164] However, the control unit 90 checks the accumulation of liquid refrigerant in the first heat source heat exchanger 18a and stops the normal control of the opening of the second heat source expansion valve 20b (within a range not exceeding 1 / 2 of the maximum possible opening), and increases the opening of the second heat source expansion valve 20b to a larger opening than the previous opening of the second heat source expansion valve 20b (see dashed line in Figure 8).

[0165] Specifically, when a predetermined condition is satisfied, the control unit 90 stops the normal control of the opening degree of the second heat source expansion valve 20b and gradually increases the opening degree of the second heat source expansion valve 20b to an opening degree greater than the previous opening degree of the second heat source expansion valve 20b (to an opening degree greater than 1 / 2 of the maximum opening degree, if necessary).

[0166] The predetermined condition here is that the defrosting of the first heat source heat exchanger 18a is not completed within a predetermined time. For example, the control unit 90 measures the time from the start of the first defrosting operation, and if it is determined that the first defrosting operation has not been completed even after the predetermined time T1 (<maximum time Tmax1) has elapsed, the control unit 90 gradually increases the opening degree of the second heat source expansion valve 20b.

[0167] Alternatively, the control unit 90 stores the time required for defrosting the last time the first defrosting operation was performed and whether the first defrosting operation was completed within the maximum time Tmax1, and based on this result, if it is predicted that the defrosting of the first heat source heat exchanger 18a will not be completed within the maximum time Tmax1, the control unit 90 gradually increases the opening of the second heat source expansion valve 20b after a predetermined time T1 (< maximum time Tmax1) has elapsed.

[0168] By performing this control, the refrigerant flows more easily through the second heat source heat exchanger 18b, and therefore, even if liquid refrigerant accumulates in the first heat source heat exchanger 18a where defrosting is performed, this liquid refrigerant is more easily discharged to the outside of the first heat source heat exchanger 18a. As a result, the time required to defrost the first heat source heat exchanger 18a can be shortened, and the amount of frost remaining in the first heat source heat exchanger 18a can be reduced.

[0169] When the first defrost operation ends, the control unit 90 changes the opening degree of the first heat source expansion valve 20a to an opening degree Op12 and the opening degree of the second heat source expansion valve 20b to an opening degree Op22 while continuing the operation of the compressor 12. As described above, the opening degrees Op12 and Op22 may be maximum opening degrees.

[0170] When the operation mode shifts to the second defrosting operation, the control unit 90 changes the opening degree of the second heat source expansion valve 20b corresponding to the second heat source heat exchanger 18b for which defrosting is performed to the opening degree Op21. The opening degree Op21 is preferably as large as possible. The opening degree Op21 will be specifically described.

[0171] When the second heat source heat exchanger 18b is used as an evaporator (in other words, when the air conditioning apparatus 100 performs the first heating operation or the second heating operation using the second heat source heat exchanger 18b as an evaporator), the control unit 90 controls the opening degree of the second heat source heat exchanger 18b within a predetermined opening degree range. Preferably, the opening degree Op21 is larger than this predetermined opening degree range. In other words, the opening degree Op21 is larger than the opening degree of the second heat source expansion valve 20b when the second heat source heat exchanger 18b is used as an evaporator. The opening degree Op21 may be the maximum opening degree that the second heat source expansion valve 20b can achieve.

[0172] In addition, when the control unit 90 transitions to the second defrost operation, it controls the opening degree of the first heat source expansion valve 20a corresponding to the first heat source heat exchanger 18a, which functions as an evaporator, basically within a range not exceeding 1 / 2 of the maximum possible opening degree, for example, according to the degree of subcooling, etc. (see solid line in Figure 8).

[0173] However, the control unit 90 checks the accumulation of liquid refrigerant in the second heat source heat exchanger 18b and stops the normal control of the opening of the first heat source expansion valve 20a (within a range not exceeding 1 / 2 of the maximum possible opening) and increases the opening of the first heat source expansion valve 20a to a larger opening than the previous opening of the first heat source expansion valve 20a (see dashed line in Figure 8).

[0174] Specifically, when a predetermined condition is satisfied, the control unit 90 stops the normal control of the opening degree of the first heat source expansion valve 20a and gradually increases the opening degree of the first heat source expansion valve 20a to an opening degree greater than the previous opening degree of the first heat source expansion valve 20a (if necessary, to an opening degree greater than 1 / 2 of the maximum opening degree).

[0175] The predetermined condition here is that the defrosting of the second heat source heat exchanger 18b is not completed within a predetermined time. For example, the control unit 90 measures the time from the start of the second defrosting operation, and if it is determined that the second defrosting operation has not been completed even after the predetermined time T2 (<maximum time Tmax2) has elapsed, the control unit 90 gradually increases the opening of the first heat source expansion valve 20a.

[0176] Alternatively, the control unit 90 stores the time required for defrosting the last time the second defrosting operation was performed and whether the second defrosting operation was completed within the maximum time Tmax2, and based on this result, if it is predicted that the defrosting of the second heat source heat exchanger 18b will not be completed within the maximum time Tmax2, the opening of the first heat source expansion valve 20a is gradually increased after a predetermined time T2 (< maximum time Tmax2) has elapsed.

[0177] By performing this control, the refrigerant flows more easily through the first heat source expansion valve 20a, and therefore, even if liquid refrigerant accumulates in the second heat source heat exchanger 18b where defrosting is performed, this liquid refrigerant is more easily discharged to the outside of the second heat source heat exchanger 18b. As a result, the time required to defrost the second heat source heat exchanger 18b can be shortened, and the amount of frost remaining in the second heat source heat exchanger 18b can be reduced.

[0178] When the second defrost operation ends, the control unit 90 changes the opening degree of the first heat source expansion valve 20a to an opening degree Op12 and the opening degree of the second heat source expansion valve 20b to an opening degree Op22 while continuing the operation of the compressor 12. The opening degrees Op12 and Op22 may be maximum opening degrees.

[0179] After the first heating operation is started, the control unit 90 controls the opening degrees of the first heat source expansion valve 20a and the second heat source expansion valve 20b as described above.

[0180] (3-4) Subcooling Valve The subcooling valve 24 is an example of a bypass valve defined in the claims.

[0181] The control unit 90 closes the subcooling valve 24 during the first heating operation, but during the first defrost operation and the second defrost operation, it basically controls the subcooling valve 24 to a predetermined opening Op31, and bypasses some of the refrigerant flowing from the utilization heat exchangers 52a, 52b to the suction pipe P1.

[0182] However, the control unit 90 checks the amount of liquid refrigerant accumulated in the first heat source heat exchanger 18a in which defrosting is being performed, or checks the amount of liquid refrigerant accumulated in the second heat source heat exchanger 18b in which defrosting is being performed, and increases the opening degree of the subcooling valve 24 beyond the opening degree Op31. Specifically, when a predetermined condition is satisfied during the first defrosting operation or the second defrosting operation, the control unit 90 increases the opening degree of the subcooling valve 24 beyond the opening degree Op31.

[0183] The predetermined condition here is that the first defrosting operation or the second defrosting operation is not completed within a predetermined time. For example, the control unit 90 measures the time from the start of the first defrosting operation, and if it is determined that the first defrosting operation is not completed even after a predetermined time T1' (< maximum time Tmax1) has elapsed, or if it is determined that the second defrosting operation is not completed even after a predetermined time T2' (< maximum time Tmax2) has elapsed, the control unit 90 increases the opening degree of the subcooling valve 24 beyond the opening degree Op31. Alternatively, the control unit 90 stores the time required for defrosting the previous time the first defrost operation or the second defrost operation was performed, and whether the first defrost operation or the second defrost operation was completed within the maximum time Tmax1 or Tmax, respectively.Based on this result, if it is predicted that the first defrost operation will not be completed within the maximum time Tmax1 or the second defrost operation will not be completed within the maximum time Tmax2, the control unit 90 increases the opening of the subcooling valve 24 from opening Op31 when a predetermined time T1' (< maximum time Tmax1) has elapsed in the case of the first defrost operation, or when a predetermined time T2' (< maximum time Tmax2) has elapsed in the case of the second defrost operation.

[0184] By performing this control, even if liquid refrigerant accumulates in the heat source heat exchangers 18a, 18b where defrosting is being performed, this liquid refrigerant is more likely to be discharged to the outside of the heat source heat exchangers 18a, 18b, thereby shortening the time required to defrost the heat source heat exchangers 18a, 18b and reducing the amount of frost remaining in the heat source heat exchangers 18a, 18b.

[0185] In another embodiment, the control unit 90 may basically close the subcooling valve 24 during the first defrosting operation and the second defrosting operation. The control unit 90 may then control the subcooling valve 24 to open when the above-described predetermined conditions are satisfied during the first defrosting operation or the second defrosting operation.

[0186] (3-5) First heat source fan and second heat source fan When the heat source heat exchangers 18a, 18b are used as evaporators, the control unit 90 controls the rotation speed of the heat source fans 17a, 17b corresponding to the heat source heat exchangers 18a, 18b in accordance with the capacity required of the air conditioning device 100.

[0187] In addition, during the first defrost operation and the second defrost operation, when defrosting of the heat source heat exchangers 18a, 18b is performed, the control unit 90 preferably stops the heat source fans 17a, 17b corresponding to the heat source heat exchangers 18a, 18b being defrosted.

[0188] (4) Features In the following, an air conditioning apparatus 100, which is an example of a refrigeration cycle apparatus of the present disclosure, will be described using an example in which the first heat source heat exchanger 18a corresponds to the first heat source heat exchanger in the claims and the second heat source heat exchanger 18b corresponds to the second heat source heat exchanger in the claims.

[0189] However, as mentioned above, it is also possible to interpret the first heat source heat exchanger 18a as corresponding to the second heat source heat exchanger in the claims, and the second heat source heat exchanger 18b as corresponding to the first heat source heat exchanger in the claims. Note that when such interpretation is made, the first switching mechanism, the second switching mechanism, the first valve, and the second valve also need to be interpreted appropriately.

[0190] (4-1) The air conditioning apparatus 100 includes a compressor 12, a first heat source heat exchanger 18a as an example of a first heat source heat exchanger, a second heat source heat exchanger 18b as an example of a second heat source heat exchanger, a first switching valve 16a as an example of a first switching mechanism, a second switching valve 16b as an example of a second switching mechanism, and a control unit 90. The first switching valve 16a switches between a state in which refrigerant discharged from a discharge port 12b of the compressor 12 flows into the first heat source heat exchanger 18a to function as a radiator, and a state in which refrigerant that has passed through the first heat source heat exchanger 18a, which functions as an evaporator, flows into the suction port 12a of the compressor 12. The second switching valve 16b switches between a state in which refrigerant discharged from the discharge port 12b of the compressor 12 flows into the second heat source heat exchanger 18b and functions as a radiator, and a state in which refrigerant that has passed through the second heat source heat exchanger 18b, which functions as an evaporator, flows into the suction port 12a of the compressor 12. The control unit 90 controls the operation of the compressor 12, the first switching valve 16a, and the second switching valve 16b. While continuing to operate the compressor 12, the control unit 90 changes the state from one in which the second heat source heat exchanger 18b functions as an evaporator and the first heat source heat exchanger 18a functions as a radiator (first defrost operation state) to one in which the second heat source heat exchanger 18b functions as a radiator and the first heat source heat exchanger 18a functions as an evaporator (second defrost operation state). The rotation speed of the compressor 12 during this change is a predetermined rotation speed Rc that is lower than the maximum rotation speed Rmax of the compressor 12 .

[0191] In the air conditioning device 100, when switching the functions of the heat source heat exchangers 18a, 18b while continuing to operate the compressor 12, the rotation speed of the compressor 12 is kept lower than the maximum rotation speed Rmax, thereby suppressing noise associated with the operation of the switching valves 16a, 16b.

[0192] (4-2) In the air conditioning device 100, the predetermined rotation speed Rc is smaller than half the maximum rotation speed Rmax.

[0193] In the air conditioning device 100, when switching the functions of the heat source heat exchangers 18a, 18b while continuing to operate the compressor 12, the rotation speed of the compressor 12 is kept lower than half the maximum rotation speed Rmax, which makes it easier to suppress noise associated with the operation of the switching valves 16a, 16b.

[0194] (4-3) In the air conditioning apparatus 100, the control unit 90 changes the state in which both the first heat source heat exchanger 18 a and the second heat source heat exchanger 18 b function as evaporators (first heating operation state) to a state in which one of the first heat source heat exchanger 18 a and the second heat source heat exchanger 18 b functions as a radiator (first defrost operation state or second defrost operation state) while continuing to operate the compressor 12. The rotation speed of the compressor 12 during this change is lower than the maximum rotation speed Rmax of the compressor 12.

[0195] In the air conditioning device 100, even when the function of one of the heat source heat exchangers 18a, 18b, which function as an evaporator, is switched to a radiator while the compressor 12 continues to operate, the rotation speed of the compressor 12 is kept lower than the maximum rotation speed Rmax, thereby suppressing noise associated with the operation of the switching valves 16a, 16b.

[0196] (4-4) The air conditioning apparatus 100 includes utilization heat exchangers 52a, 52b, a discharge pipe P2 as an example of piping, and a sound-absorbing member 25. The discharge pipe P2 connects the first and second switching valves 16a, 16b to the utilization heat exchangers 52a, 52b (the discharge pipe P2 is part of the piping connecting the first and second switching valves 16a, 16b to the utilization heat exchangers 52a, 52b). The sound-absorbing member 25 is installed in the discharge pipe P2.

[0197] In the air conditioning device 100, by providing a sound-absorbing member 25 on the discharge pipe P2, it is possible to suppress the propagation of noise to the space in which the utilization heat exchangers 52a, 52b are installed (for example, the space to be air-conditioned if air conditioning is performed using the utilization heat exchanger) or a space nearby.

[0198] (4-5) The air conditioning apparatus 100 includes a casing 10a that houses the first heat source heat exchanger 18a, the second heat source heat exchanger 18b, the first switching valve 16a, and the second switching valve 16b. A single sound-absorbing member 25 is installed within the casing 10a.

[0199] In the air conditioning apparatus 100, the single sound deadening member 25 can suppress the propagation of noise to the space in which the utilization heat exchangers 52a, 52b are installed, while suppressing an increase in the number of parts.

[0200] (4-6) The air conditioning apparatus 100 includes a first heat source expansion valve 20a as an example of a first valve that adjusts the flow rate of refrigerant flowing through the first heat source heat exchanger 18a, and a second heat source expansion valve 20b as an example of a second valve that adjusts the flow rate of refrigerant flowing through the second heat source heat exchanger 18b. The control unit 90 controls the operation of the first heat source expansion valve 20a and the second heat source expansion valve 20b. When using the first heat source heat exchanger 18a as an evaporator and the second heat source heat exchanger 18b as a radiator to defrost the second heat source heat exchanger 18b, the control unit 90 sets the opening degree of the second heat source expansion valve 20b to be larger than the opening degree of the second heat source expansion valve 20b when using the second heat source heat exchanger 18b as an evaporator.

[0201] If liquid refrigerant accumulates in the second heat source heat exchanger 18b during defrosting, the time required to defrost the second heat source heat exchanger 18b increases, and there is a possibility that unmelted frost will occur. In contrast, in this air conditioning apparatus 100, the opening degree of the second heat source expansion valve 20b corresponding to the first heat source heat exchanger 18a where defrosting is performed is set larger than the opening degree of the second heat source expansion valve 20b when the second heat source heat exchanger 18b is used as an evaporator, so that liquid refrigerant is less likely to accumulate in the second heat source heat exchanger 18b during defrosting. Therefore, in this air conditioning apparatus 100, the time required for defrosting can be shortened and unmelted frost can be suppressed.

[0202] (4-7) In the air conditioning apparatus 100, the control unit 90 uses the first heat source heat exchanger 18a as an evaporator while using the second heat source heat exchanger 18b as a radiator, and when defrosting the second heat source heat exchanger 18b, if a predetermined condition is satisfied, increases the opening of the first heat source expansion valve 20a.

[0203] When the second heat source heat exchanger 18b is used as a radiator and the first heat source heat exchanger 18a is used as an evaporator, a portion of the refrigerant that passes through the second heat source heat exchanger 18b is sent to the first heat source heat exchanger 18a. This air conditioning device 100 increases the opening of the second heat source expansion valve 20b when a predetermined condition is met, making it easier for refrigerant to flow through the first heat source heat exchanger 18a. Therefore, even if liquid refrigerant accumulates in the second heat source heat exchanger 18b where defrosting is performed, this liquid refrigerant is more easily discharged from the second heat source heat exchanger 18b. As a result, this air conditioning device 100 shortens the time required to defrost the second heat source heat exchanger 18b and reduces the amount of frost remaining in the second heat source heat exchanger 18b.

[0204] (4-8) The air conditioning apparatus 100 includes a first refrigerant pipe (liquid pipe P4 and liquid refrigerant communication pipe 32), a suction pipe P1, a bypass pipe P6, and a subcooling valve 24 as an example of a bypass valve. A first heat source heat exchanger 18a and a second heat source heat exchanger 18b are connected in parallel to one end of the first refrigerant pipe, and utility heat exchangers 52a and 52b are connected to the other end of the first refrigerant pipe. The suction pipe P1 is connected to the suction port 12a of the compressor 12. The bypass pipe P6 connects the first refrigerant pipe and the suction pipe P1. The subcooling valve 24 is provided in the bypass pipe P6. A controller 90 controls the operation of the subcooling valve 24. The control unit 90 uses the first heat source heat exchanger 18a as an evaporator and the second heat source heat exchanger 18b as a radiator, and when defrosting the second heat source heat exchanger 18b, if a predetermined condition is met, opens the closed supercooling valve 24 or increases the opening degree of the open supercooling valve 24.

[0205] In the air conditioning apparatus 100, by opening the closed subcooling valve 24 or increasing the opening of the open subcooling valve 24, a portion of the refrigerant flowing to the first heat source heat exchanger 18a flows through the bypass pipe P6, so even if liquid refrigerant accumulates in the second heat source heat exchanger 18b where defrosting is performed, this liquid refrigerant is more likely to be discharged to the outside of the second heat source heat exchanger 18b. As a result, in the air conditioning apparatus 100, the time required to defrost the second heat source heat exchanger 18b can be shortened and the amount of frost remaining in the second heat source heat exchanger 18b can be reduced.

[0206] (4-9) In the air conditioning apparatus 100, the predetermined condition in (4-8) and (4-9) is that defrosting of the second heat source heat exchanger 18b is not completed within a predetermined time.

[0207] From the viewpoint of defrosting efficiency, it is preferable not to unnecessarily increase the opening of the first heat source expansion valve 20a or the subcooling valve 24. However, if liquid refrigerant accumulates in the second heat source heat exchanger 18b, as described above, there is a risk that the time required for defrosting will be prolonged or that some frost will remain unmelted.

[0208] In the air conditioning device 100, if defrosting is not completed within a specified time, the opening degree of the first heat source expansion valve 20a and the subcooling valve 24 is increased, thereby preventing a decrease in defrosting efficiency while preventing the defrosting time from being extended or frost from remaining unmelted.

[0209] (5) Modifications Modifications of the above embodiment are shown below. The following modifications may be combined as appropriate as long as they do not contradict each other.

[0210] (5-1) Modification A In the above embodiment, the air conditioning apparatus 100 has only one compressor, but multiple compressors may be provided. For example, the air conditioning apparatus 100 may have two compressors, with the discharge pipe extending from the discharge port of one compressor connected to the first switching valve 16a and the discharge pipe extending from the discharge port of the other compressor connected to the second switching valve 16b.

[0211] (5-2) Modification B In the above embodiment, for the purpose of switching the functions of the utilization heat exchangers 52a, 52b, the third switching valve 16c and the fourth switching valve 16d are provided in the heat source unit 10. However, this is not limited to this aspect, and instead of providing the heat source unit 10 with the third switching valve 16c and the fourth switching valve 16d, a flow path switching unit for switching the functions of the utilization heat exchangers 52a, 52b may be individually provided for each of the utilization units 50a, 50b.

[0212] (5-3) Modification C In the above embodiment, the subcooling valve 24 is used as a bypass valve. However, the refrigeration cycle device may be provided with a bypass valve, separate from the subcooling valve 24, in a bypass pipe other than the bypass pipe P6 that connects the first refrigerant pipe (liquid pipe P4 and liquid refrigerant communication pipe 32) and the suction pipe P1.

[0213] (5-4) Variation D In the above embodiment, it is described that the first heat source expansion valve 20a is provided in the liquid pipe P4a to adjust the flow rate of the refrigerant passing through the first heat source heat exchanger 18a, and the second heat source expansion valve 20b is provided in the liquid pipe P4b to adjust the flow rate of the refrigerant passing through the second heat source heat exchanger 18b.

[0214] However, the present invention is not limited to this, and for example, a regulating valve 21a may be provided in the first gas pipe P3a to directly regulate the flow rate of the refrigerant passing through the first heat source heat exchanger 18a, and a regulating valve 21b may be provided in the first gas pipe P3b to directly regulate the flow rate of the refrigerant passing through the second heat source heat exchanger 18b (see FIG. 9). The regulating valves 21a and 21b are, for example, electrically operated valves with variable opening.

[0215] 9, the control unit 90 may control only the aperture of the adjustment valve 21a to adjust the flow rate of the refrigerant passing through the first heat source heat exchanger 18a, or may control the aperture of the adjustment valve 21a and the aperture of the first heat source expansion valve 20a to adjust the flow rate of the refrigerant passing through the first heat source heat exchanger 18a. Also, the control unit 90 may control only the aperture of the adjustment valve 21b to adjust the flow rate of the refrigerant passing through the second heat source heat exchanger 18b, or may control the aperture of the adjustment valve 21b and the aperture of the second heat source expansion valve 20b to adjust the flow rate of the refrigerant passing through the second heat source heat exchanger 18b.

[0216] (5-5) Modification E The air conditioning apparatus as a refrigeration cycle apparatus may be an air conditioning apparatus 100A having a utilization unit 150 instead of the utilization units 50a and 50b of the above embodiment, as shown in Fig. 10. Only one utilization unit 150 is depicted in Fig. 10. However, this is not limited to this, and the air conditioning apparatus 100A may have multiple utilization units 150, and the multiple utilization units 150 may be connected in parallel in the refrigerant circuit 40A.

[0217] The air conditioning apparatus 100A having the utilization unit 150 differs from the air conditioning apparatus 100 of the above embodiment having the utilization units 50a and 50b mainly in that it can perform reheat dehumidification operation in addition to cooling operation and heating operation. The reheat dehumidification operation is an operation that dehumidifies the air in the air-conditioned space of the utilization unit 150 while preventing the air in the air-conditioned space from becoming too cold.

[0218] The following mainly describes the main differences between the air conditioning apparatus 100A and the air conditioning apparatus 100 of the above embodiment, namely the configuration of the utilization unit 150 and the operation of the air conditioning apparatus 100A.

[0219] The utilization unit 150 is connected to the heat source unit 10 via the refrigerant communication pipes 32, 34, and 36, and constitutes part of the refrigerant circuit 40A. The utilization unit 150 is installed, for example, indoors (air-conditioned space) of a building or the like, or in the ceiling of the air-conditioned space.

[0220] The utilization unit 150 mainly includes a first heat exchanger 152a, a second heat exchanger 152b, a first expansion valve 154a, a second expansion valve 154b, a utilization fan 156, and a utilization control unit 94A.

[0221] The heat exchangers 152a and 152b are, for example, fin-and-tube heat exchangers configured with a large number of heat transfer tubes and fins. In the heat exchangers 152a and 152b, heat is exchanged between the refrigerant flowing therethrough and the air in the space to be air-conditioned.

[0222] One end (liquid side) of the first heat exchanger 152a is connected via piping to the liquid refrigerant connection pipe 32, and the other end (gas side) is connected via piping to the gas refrigerant connection pipe 36. One end (liquid side) of the second heat exchanger 152b is connected via piping to the liquid refrigerant connection pipe 32, and the other end (gas side) is connected via piping to the gas refrigerant connection pipe 34.

[0223] The first heat exchanger 152a functions as a refrigerant heat radiator (condenser) or an evaporator (heat absorber) depending on the piping connection state of the fourth selector valve 16d. The second heat exchanger 152b functions as a refrigerant heat radiator (condenser) or an evaporator (heat absorber) depending on the piping connection state of the third selector valve 16c.

[0224] The first expansion valve 154a is disposed in the piping connecting the first heat exchanger 152a and the liquid refrigerant communication pipe 32 (the piping on the first heat exchanger 152a side from the branching point where the piping connected to the liquid refrigerant communication pipe 32 branches). The second expansion valve 154b is disposed in the piping connecting the second heat exchanger 152b and the liquid refrigerant communication pipe 32 (the piping on the second heat exchanger 152b side from the branching point where the piping connected to the liquid refrigerant communication pipe 32 branches).

[0225] The expansion valves 154a and 154b are electrically operated valves with adjustable openings. The expansion valves 154a and 154b adjust the flow rate of the refrigerant. The expansion valves 154a and 154b also reduce the pressure (expand) of the refrigerant passing through them depending on their openings.

[0226] The utilization fan 156 takes in air from the space to be air-conditioned, supplies it to the heat exchangers 152a and 152b, and blows the air that has exchanged heat with the refrigerant in the heat exchangers 152a and 152b into the space to be air-conditioned in order to promote heat exchange between the air and the refrigerant in the heat exchangers 152a and 152b. In the direction of the airflow generated by the fans, the second heat exchanger 152b is disposed downstream of the first heat exchanger 152a. Therefore, the air that has passed through the first heat exchanger 152a (the air that has exchanged heat with the refrigerant in the first heat exchanger 152a) is sent to the second heat exchanger 152b. The utilization fan 156 is a fan with a variable rotation speed. The type of fan used as the utilization fan 156 may be selected as appropriate.

[0227] The usage control unit 94A functions as a control unit 90A that controls the operation of the air conditioning apparatus 100A together with the heat source control unit 92. The physical configuration of the usage control unit 94A is similar to the usage control units 94a and 94b in the above embodiment, and therefore a description thereof will be omitted.

[0228] During cooling operation, the control unit 90A controls the first to fourth switching valves 16a to 16d so that the first heat exchanger 152a and the second heat exchanger 152b of the utilization unit 150 function as evaporators and the heat source heat exchangers 18a and 18b function as condensers. The control of the operation of the various devices by the control unit 90A is the same as during cooling operation in the above embodiment, and therefore a detailed description thereof will be omitted.

[0229] The flow of refrigerant in the refrigerant circuit 40A during refrigerant operation will be briefly described.

[0230] The high-pressure gas refrigerant discharged from the discharge port 12b of the compressor 12 passes through the discharge pipe P2, the first switching valve 16a and the second switching valve 16b, and is condensed as it passes through the first heat source heat exchanger 18a and the second heat source heat exchanger 18b, becoming a high-pressure liquid refrigerant.

[0231] Most of the high-pressure liquid refrigerant flowing out of the first heat source heat exchanger 18a and the second heat source heat exchanger 18b passes through the liquid pipe P4 and flows into the liquid refrigerant communication pipe 32. A portion of the high-pressure liquid refrigerant flowing out of the first heat source heat exchanger 18a and the second heat source heat exchanger 18b passes through the bypass pipe P6 and flows into the suction pipe P1. The refrigerant flowing from the liquid pipe P4 into the subcooling heat exchanger 22 exchanges heat with the refrigerant flowing into the subcooling heat exchanger 22 from the bypass pipe P6 and is subcooled.

[0232] The high-pressure liquid refrigerant that has passed through the subcooling heat exchanger 22 further flows through the liquid pipe P4 and the liquid refrigerant connection pipe 32, before flowing into the utilization units 150. The high-pressure liquid refrigerant that has flowed into the utilization units 150 is reduced in pressure as it passes through expansion valves 154a, 154b, the opening of which is controlled by the control unit 90A to an appropriate value based on the detection results of the sensors, to become a two-phase gas-liquid refrigerant. The two-phase gas-liquid refrigerant is evaporated in the heat exchangers 152a, 152b to become a low-pressure gas refrigerant, which cools the air in the air-conditioned spaces of the utilization units 150. The low-pressure gas refrigerant that has passed through the first heat exchanger 152a passes through the gas refrigerant connection pipe 36, flows into the second gas pipe P5b, passes through the fourth switching valve 16d, and flows into the suction pipe P1. The low-pressure gas refrigerant that has passed through the second heat exchanger 152b passes through the gas refrigerant communication pipe 34, flows into the second gas pipe P5a, passes through the third switching valve 16c, and flows into the suction pipe P1. The low-pressure gas refrigerant that has flowed into the suction pipe P1 passes through the accumulator 14, and is then sucked into the compressor 12 from the suction port 12a.

[0233] During reheat dehumidification operation, the control unit 90A controls the first switching valve 16a to the fourth switching valve 16d so that the first heat exchanger 152a functions as an evaporator, the second heat exchanger 152b functions as a condenser, and the heat source heat exchangers 18a and 18b function as condensers.

[0234] A brief description will be given of the main flow of refrigerant in the refrigerant circuit 40A during the reheat dehumidification operation.

[0235] During reheat dehumidification operation, a portion of the high-pressure gas refrigerant discharged from the discharge port 12b of the compressor 12 passes through the discharge pipe P2, the first switching valve 16a and the second switching valve 16b, and is condensed as it passes through the first heat source heat exchanger 18a and the second heat source heat exchanger 18b, as in cooling operation. Also, a portion of the high-pressure gas refrigerant discharged from the discharge port 12b of the compressor 12 passes through the discharge pipe P2, the third switching valve 16c, and is condensed as it passes through the second heat exchanger 152b, becoming a high-pressure liquid refrigerant.

[0236] Most of the high-pressure liquid refrigerant flowing out of the first heat source heat exchanger 18a and the second heat source heat exchanger 18b passes through the liquid pipe P4 and flows into the liquid refrigerant communication pipe 32. A portion of the high-pressure liquid refrigerant flowing out of the first heat source heat exchanger 18a and the second heat source heat exchanger 18b passes through the bypass pipe P6 and flows into the suction pipe P1. The refrigerant flowing from the liquid pipe P4 into the subcooling heat exchanger 22 exchanges heat with the refrigerant flowing into the subcooling heat exchanger 22 from the bypass pipe P6 and is subcooled.

[0237] The subcooled high-pressure liquid refrigerant that has passed through the subcooling heat exchanger 22 further flows through the liquid pipe P4, passes through the liquid refrigerant connection pipe 32, and flows into the first heat exchanger 152a of the utilization unit 150. The high-pressure liquid refrigerant condensed while passing through the second heat exchanger 152b merges with the high-pressure liquid refrigerant flowing from the heat source unit 10 and flows into the first heat exchanger 152a. The refrigerant heading toward the first heat exchanger 152a is reduced in pressure as it passes through the first expansion valve 154a, which the control unit 90A controls to an appropriate opening based on the detection results of the sensor, to become a two-phase gas-liquid refrigerant. As the two-phase gas-liquid refrigerant evaporates in the first heat exchanger 152a and becomes low-pressure gas refrigerant, it cools the air in the air-conditioned space supplied by the fan 156 and condenses (condenses) the water vapor in the air to dehumidify it. The air dehumidified by the first heat exchanger 152a is heated (reheated) by the second heat exchanger 152b, which functions as a condenser, and then blown out into the space to be air-conditioned.

[0238] The low-pressure gas refrigerant that has passed through the first heat exchanger 152a passes through the gas refrigerant communication pipe 36, flows into the second gas pipe P5b, passes through the fourth switching valve 16d, and flows into the suction pipe P1. The low-pressure gas refrigerant that has flowed into the suction pipe P1 passes through the accumulator 14, and is then sucked into the compressor 12 from the suction port 12a.

[0239] During heating operation (first heating operation), the control unit 90A controls the first to fourth switching valves 16a to 16d so that the first heat exchanger 152a and the second heat exchanger 152b of the utilization unit 150 function as condensers and the heat source heat exchangers 18a and 18b function as evaporators. The control of the operation of the various devices by the control unit 90A is the same as during heating operation in the above embodiment, and therefore a detailed description thereof will be omitted.

[0240] The flow of refrigerant in the refrigerant circuit 40A during the heating operation (first heating operation) will be briefly described.

[0241] The high-pressure gas refrigerant discharged from the discharge port 12b of the compressor 12 passes through the discharge pipe P2, the third switching valve 16c, and the fourth switching valve 16d, and is condensed into high-pressure liquid refrigerant in the heat exchangers 152b and 152a. In the process of the high-pressure gas refrigerant being converted into high-pressure liquid refrigerant in the heat exchangers 152a and 152b, the refrigerant heats the air in the space to be air-conditioned in the utilization unit 150.

[0242] The high-pressure liquid refrigerant that has passed through the heat exchangers 152a, 152b passes through the liquid refrigerant connection pipe 32 and flows into the heat source unit 10, then flows through the liquid pipe P4. A portion of the high-pressure liquid refrigerant flowing through the liquid pipe P4 flows through the liquid pipe P4a and is decompressed as it passes through the first heat source expansion valve 20a, becoming a gas-liquid two-phase refrigerant, which then flows into the first heat source heat exchanger 18a. The remainder of the high-pressure liquid refrigerant flowing through the liquid pipe P4b and is decompressed as it passes through the second heat source expansion valve 20b, becoming a gas-liquid two-phase refrigerant, which then flows into the second heat source heat exchanger 18b. The gas-liquid two-phase refrigerant is evaporated in the first heat source heat exchanger 18a and the second heat source heat exchanger 18b, becoming a low-pressure gas refrigerant. The low-pressure gas refrigerant flowing out of the first heat source heat exchanger 18a flows into the first gas pipe P3a, passes through the first switching valve 16a, and flows into the suction pipe P1. The low-pressure gas refrigerant flowing out of the second heat source heat exchanger 18b flows into the first gas pipe P3b, passes through the second switching valve 16b, and flows into the suction pipe P1. The low-pressure gas refrigerant that has flowed into the suction pipe P1 passes through the accumulator 14, and is then drawn into the compressor 12 through the suction port 12a.

[0243] Note that the control of the compressor 12, the first switching valve 16a, the second switching valve 16b, the first heat source expansion valve 20a, the second heat source expansion valve 20b, the first heat source fan 17a, the second heat source fan 17b, and the subcooling valve 24 during the period from when the first heating operation is interrupted to when alternating defrosting (the second heating operation (first defrost operation) and the third heating operation (second defrost operation)) is performed until the first heating operation is resumed is the same as the control described with reference to Figure 8 in the above embodiment, and therefore will not be described here.

[0244] (5-6) Modification F In the air conditioning apparatus 100 of the above embodiment, the heat source unit 10 and the multiple utilization units 50a, 50b are connected by three refrigerant communication pipes 32, 34, 36, but the present invention is not limited to this.

[0245] 11 , the heat source unit 10 and multiple utilization units 50a, 50b may be connected by two refrigerant connection pipes 32, 34. This air conditioning apparatus 100B does not have a fourth switching valve 16d, gas refrigerant connection pipe 36, gas shut-off valve 28b, or second gas pipe P5a. In this air conditioning apparatus 100B, one end (liquid side) of the utilization heat exchanger 52b is connected to the liquid refrigerant connection pipe 32 via piping, and the other end (gas side) is connected to the gas refrigerant connection pipe 34 via piping.

[0246] The main difference between the air conditioning apparatus 100B and the air conditioning apparatus 100 is that the air conditioning apparatus 100B cannot operate in a manner that uses one of the utilization heat exchangers 52a and 52b as a condenser and the other of the utilization heat exchangers 52a and 52b as an evaporator. In other words, the air conditioning apparatus 100B can only perform either an operation in which both the utilization heat exchangers 52a and 52b are used as condensers, or an operation in which both the utilization heat exchangers 52a and 52b are used as evaporators.

[0247] The air conditioning apparatus 100B is otherwise similar to the air conditioning apparatus 100 of the above embodiment. For example, the control of the compressor 12, first switching valve 16a, second switching valve 16b, first heat source expansion valve 20a, second heat source expansion valve 20b, first heat source fan 17a, second heat source fan 17b, and subcooling valve 24 when the first heating operation is interrupted and alternating defrosting (second heating operation (first defrost operation) and third heating operation (second defrost operation)) is performed, and until the first heating operation is resumed, is similar to the control described with reference to FIG. 8 in the above embodiment. Therefore, a description of the other aspects of the air conditioning apparatus 100B will be omitted.

[0248] (5-7) Modification G In the above embodiment, the first switching valve 16a and the second switching valve 16b are used to switch between a state in which both the first heat source heat exchanger 18a and the second heat source heat exchanger 18b function as condensers, a state in which both the first heat source heat exchanger 18a and the second heat source heat exchanger 18b function as evaporators, a state in which the first heat source heat exchanger 18a functions as a condenser and the second heat source heat exchanger 18b functions as an evaporator, and a state in which the first heat source heat exchanger 18a functions as an evaporator and the second heat source heat exchanger 18b functions as a condenser. However, this may be achieved by other configurations.

[0249] For example, the air conditioning apparatus 100C in Fig. 12 does not include a first switching valve 16a. A discharge pipe P2, a first gas pipe P3a, a first gas pipe P3b, and a bypass pipe P6 are connected to the four ports of a second switching valve 16b, which is a four-way switching valve. The first gas pipe P3a and the first gas pipe P3b are connected by a bypass pipe P7. A solenoid valve 29a is disposed between the end of the first gas pipe P3a connected to the second switching valve 16b and the branch point of the first gas pipe P3a and the bypass pipe P7. A solenoid valve 29b is disposed on the bypass pipe P7.

[0250] In this configuration, when both the first heat source heat exchanger 18a and the second heat source heat exchanger 18b function as condensers, the second switching valve 16b connects the discharge pipe P2 to the first gas pipe P3b and connects the first gas pipe P3a to the bypass pipe P6. Furthermore, when both the first heat source heat exchanger 18a and the second heat source heat exchanger 18b function as condensers, the solenoid valve 29a is closed and the solenoid valve 29b is open.

[0251] When both the first heat source heat exchanger 18a and the second heat source heat exchanger 18b function as evaporators, the second switching valve 16b connects the discharge pipe P2 to the first gas pipe P3a and connects the first gas pipe P3b to the bypass pipe P6. When both the first heat source heat exchanger 18a and the second heat source heat exchanger 18b function as condensers, the solenoid valve 29a is closed and the solenoid valve 29b is open.

[0252] When the first heat source heat exchanger 18a functions as a condenser and the second heat source heat exchanger 18b functions as an evaporator, the second switching valve 16b connects the discharge pipe P2 to the first gas pipe P3b and connects the first gas pipe P3a to the bypass pipe P6. When the first heat source heat exchanger 18a functions as a condenser and the second heat source heat exchanger 18b functions as an evaporator, the solenoid valve 29a is opened and the solenoid valve 29b is closed.

[0253] When the first heat source heat exchanger 18a functions as an evaporator and the second heat source heat exchanger 18b functions as a condenser, the second switching valve 16b connects the discharge pipe P2 to the first gas pipe P3a and connects the first gas pipe P3b to the bypass pipe P6. When the first heat source heat exchanger 18a functions as an evaporator and the second heat source heat exchanger 18b functions as a condenser, the solenoid valve 29a is opened and the solenoid valve 29b is closed.

[0254] <Additional Note> Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the present disclosure as defined in the claims.

[0255] DESCRIPTION OF SYMBOLS 10a Casing 12 Compressor 12a Intake port 12b Discharge port 16a First switching valve (first switching mechanism, second switching mechanism) 16b Second switching valve (second switching mechanism, first switching mechanism) 18a First heat source heat exchanger (first heat source heat exchanger, second heat source heat exchanger) 18b Second heat source heat exchanger (second heat source heat exchanger, first heat source heat exchanger) 20a First heat source expansion valve (first valve, second valve) 20b Second heat source expansion valve (second valve, first valve) 21a Adjusting valve (first valve, second valve) 21b Adjusting valve (second valve, first valve) 24 Subcooling valve (bypass valve) 29a, 29b Solenoid valve (second switching mechanism, first switching mechanism) 25 Silencer 52a, 52b Utilization heat exchangers 152a First heat exchanger (utilization heat exchanger) 152b Second heat exchanger (utilization heat exchanger) 90 Control unit 90A Control unit 100 Air conditioner (refrigeration cycle device) 100A Air conditioner (refrigeration cycle device) 100B Air conditioner (refrigeration cycle device) 100C Air conditioner (refrigeration cycle device) P1 Intake pipe P2 Discharge pipe P6 Bypass pipe Rmax Maximum rotation speed

[0256] Publication No. 9-318206

Claims

1. A compressor (12); a first heat source heat exchanger (18a, 18b) and a second heat source heat exchanger (18b, 18a); a first switching mechanism (16a, 16b, 29a, 29b) that switches between a state in which refrigerant discharged from a discharge port (12b) of the compressor flows into the first heat source heat exchanger and functions as a radiator, and a state in which refrigerant that has passed through the first heat source heat exchanger and functions as an evaporator flows into the suction port (12a) of the compressor; a second switching mechanism (16b, 16a, 29a, 29b) that switches between a state in which refrigerant discharged from the discharge port of the compressor flows into the second heat source heat exchanger and functions as a radiator, and a state in which refrigerant that has passed through the second heat source heat exchanger and functions as an evaporator flows into the suction port of the compressor; and a control unit (90) that controls the operation of the compressor, the first switching mechanism, and the second switching mechanism, the control unit, while continuing operation of the compressor, changes the rotation speed of the compressor from a state in which the second heat source heat exchanger functions as an evaporator and the first heat source heat exchanger functions as a radiator to a state in which the second heat source heat exchanger functions as a radiator and the first heat source heat exchanger functions as an evaporator, a predetermined rotation speed that is lower than a maximum rotation speed (Rmax) of the compressor.

2. The refrigeration cycle device according to claim 1, wherein the predetermined rotation speed is smaller than half of the maximum rotation speed.

3. A refrigeration cycle device as described in claim 1 or 2, wherein the rotation speed of the compressor when the control unit changes from a state in which both the first heat source heat exchanger and the second heat source heat exchanger function as evaporators to a state in which one of the first heat source heat exchanger and the second heat source heat exchanger functions as a radiator while continuing to operate the compressor is smaller than the maximum rotation speed.

4. The refrigeration cycle device according to any one of claims 1 to 3, further comprising: a utilization heat exchanger (52a, 52b, 152a, 152b); a pipe (P2) connecting the first switching mechanism, the second switching mechanism, and the utilization heat exchanger; and a sound-absorbing member (25) installed on the pipe.

5. The refrigeration cycle device according to claim 4, further comprising a casing (10a) that houses the first heat source heat exchanger, the second heat source heat exchanger, the first switching mechanism, and the second switching mechanism, and a single sound-absorbing member is installed inside the casing.

6. A refrigeration cycle device as described in any one of claims 1 to 5, further comprising: a first valve (20a, 20b, 21a, 21b) that adjusts the flow rate of refrigerant flowing through the first heat source heat exchanger (18a, 18b); and a second valve (20b, 20a, 21b, 21a) that adjusts the flow rate of refrigerant flowing through the second heat source heat exchanger (18b, 18a), wherein the control unit further controls the operation of the first valve and the second valve, and the control unit uses the first heat source heat exchanger as an evaporator while using the second heat source heat exchanger as a radiator to defrost the second heat source heat exchanger, and sets the opening degree of the second valve to be larger than the opening degree of the second valve when using the second heat source heat exchanger as an evaporator.

7. A refrigeration cycle device according to any one of claims 1 to 6, wherein the control unit increases the opening of the first valve when a predetermined condition is satisfied when defrosting the second heat source heat exchanger by using the first heat source heat exchanger as an evaporator and the second heat source heat exchanger as a radiator.

8. The refrigeration cycle device according to any one of claims 1 to 7, further comprising: a first refrigerant pipe having one end to which the first heat source heat exchanger and the second heat source heat exchanger are connected in parallel and the other end to which a utilization heat exchanger is connected; a suction pipe (P1) connected to the suction port of the compressor; a bypass pipe (P6) connecting the first refrigerant pipe and the suction pipe; and a bypass valve (24) provided in the bypass pipe, wherein the control unit further controls the operation of the bypass valve, and the control unit uses the first heat source heat exchanger as an evaporator and the second heat source heat exchanger as a radiator to defrost the second heat source heat exchanger, and when a predetermined condition is satisfied, opens the bypass valve that has been closed or increases the opening degree of the bypass valve that has been open.

9. The refrigeration cycle apparatus according to claim 7 or 8, wherein the predetermined condition is that defrosting of the second heat source heat exchanger is not completed within a predetermined time.

Images