Refrigeration cycle apparatus

Abstract

This refrigeration cycle apparatus comprises a refrigerant circuit and a control device. The refrigerant circuit has a first path and a second path as refrigerant paths during heating operation. The refrigerant circuit has a third path as a refrigerant path during first defrosting operation. The third path passes from a compressor through a first flow path switching device, a first outdoor heat exchanger, a second throttle device, a third throttle device, a second outdoor heat exchanger, and a second flow path switching device, and then returns to the compressor. The refrigerant circuit has a fourth path as a refrigerant path during second defrosting operation. The fourth path passes from the compressor through the second flow path switching device, the second outdoor heat exchanger, the third throttle device, the second throttle device, the first outdoor heat exchanger, and the first flow path switching device, and then returns to the compressor. The control device brings a flow control valve and a first throttle device into a fully closed state during the first defrosting operation and the second defrosting operation.

Description

Refrigeration cycle equipment

[0001] The present disclosure relates to a refrigeration cycle device.

[0002] The refrigeration cycle device has a heat exchanger. The heat exchanger functions as a condenser mounted in, for example, an indoor unit. In the refrigeration cycle device, liquid refrigerant condensed in the heat exchanger is decompressed by a throttling device and becomes a gas-liquid two-phase state in which gas refrigerant and liquid refrigerant are mixed. Then, in a heat exchanger functioning as an evaporator mounted in the outdoor unit, the liquid refrigerant in the gas-liquid two-phase state evaporates to become a low-pressure gas refrigerant. The low-pressure gas refrigerant sent out from the heat exchanger then flows into a compressor, where it is compressed into a high-temperature, high-pressure gas refrigerant, which is then discharged from the compressor again. This cycle is repeated in the refrigeration cycle device.

[0003] In such a refrigeration cycle system, when heating operation is performed under conditions where the outdoor air temperature is low, condensed water freezes and frost forms in the outdoor heat exchanger, making it impossible to continue heating operation. In such a situation, a defrosting operation is performed in which the air flow to the indoor heat exchanger is stopped and high-temperature refrigerant discharged from the compressor is supplied to the outdoor heat exchanger. Once the frost on the outdoor heat exchanger is removed by the defrosting operation, heating operation can be resumed.

[0004] During defrosting, liquid refrigerant condensed in the outdoor heat exchanger flows into the compressor without evaporating in the indoor heat exchanger. This dilutes the refrigeration oil in the compressor and is carried out of the compressor along with the refrigerant. This can result in the compressor oil running out, which can cause excessive friction and lead to compressor failure or reduced air conditioner performance. To solve this problem, there is a technology that separates the outdoor heat exchanger, prevents refrigerant from flowing through the indoor heat exchanger, and alternately defrosts the two outdoor heat exchangers (see, for example, Patent Document 1).

[0005] JP 2016-20784 A

[0006] However, in the configuration of Patent Document 1, the circuit connected to the indoor heat exchanger is connected to a circuit that defrosts the outdoor heat exchanger. Furthermore, the refrigerant pressure in the indoor heat exchanger during heating operation is higher than the refrigerant discharge pressure from the compressor during defrost operation. Therefore, when switching from heating operation to defrost operation, the high-pressure liquid refrigerant in the indoor heat exchanger flows into the defrost circuit, driven by the pressure difference between the pressure in the indoor heat exchanger and the pressure in the compressor during defrost operation. This causes the liquid refrigerant to be drawn into the compressor, potentially causing compressor failure.

[0007] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a refrigeration cycle device that can suppress compressor failures.

[0008] A refrigeration cycle device according to the present disclosure includes a refrigerant circuit having a compressor, an indoor heat exchanger, a first outdoor heat exchanger, and a second outdoor heat exchanger, and a control device, wherein the refrigerant circuit has a first path and a second path as refrigerant paths during heating operation in which the indoor heat exchanger functions as a condenser, the first path being a path from the compressor passing through a flow control valve, the indoor heat exchanger, a first throttling device, a second throttling device, the first outdoor heat exchanger, and a first flow path switching device and returning to the compressor, and the second path being a path from the compressor passing through the flow control valve, the indoor heat exchanger, the first throttling device, a third throttling device, the second outdoor heat exchanger, and a second flow path switching device and returning to the compressor, and the refrigerant circuit is configured to operate in a first defrosting operation in which the first outdoor heat exchanger functions as a condenser and the second outdoor heat exchanger functions as an evaporator. The refrigerant circuit has a third path as a refrigerant path during a second defrost operation in which the second outdoor heat exchanger functions as a condenser and the first outdoor heat exchanger functions as an evaporator, and the third path is a path that runs from the compressor through the first flow path switching device, the first outdoor heat exchanger, the second throttling device, the third throttling device, the second outdoor heat exchanger, and the second flow path switching device, and returns to the compressor.The refrigerant circuit has a fourth path as a refrigerant path during a second defrost operation in which the second outdoor heat exchanger functions as a condenser and the first outdoor heat exchanger functions as an evaporator, and the fourth path is a path that runs from the compressor through the second flow path switching device, the second outdoor heat exchanger, the third throttling device, the second throttling device, the first outdoor heat exchanger, and the first flow path switching device, and returns to the compressor.The control device keeps the flow control valve and the first throttling device fully closed during the first defrost operation and the second defrost operation.

[0009] According to the present disclosure, compressor failures can be suppressed.

[0010] 1 is a circuit diagram showing a schematic configuration of a refrigeration cycle apparatus according to Embodiment 1 during heating operation. FIG. 2 is a diagram showing control details of each operation mode by a control device of the refrigeration cycle apparatus according to Embodiment 1. FIG. 3 is a circuit diagram showing a schematic configuration of a refrigeration cycle apparatus according to Embodiment 1 during a first defrost operation. FIG. 4 is a circuit diagram showing a schematic configuration of a refrigeration cycle apparatus according to Modification 1 of Embodiment 1. FIG. 5 is a circuit diagram showing a schematic configuration of a refrigeration cycle apparatus according to Modification 2 of Embodiment 1 during heating operation. FIG. 6 is a circuit diagram showing a schematic configuration of a refrigeration cycle apparatus according to Modification 2 of Embodiment 1 during a first defrost operation. FIG. 7 is a circuit diagram showing a schematic configuration of a refrigeration cycle apparatus according to Modification 2 of Embodiment 1 during a second defrost operation. FIG. 8 is a diagram showing control details of each operation mode by a control device of a refrigeration cycle apparatus according to Embodiment 2. FIG. 9 is a circuit diagram showing a schematic configuration of a refrigeration cycle apparatus according to Modification 1 of Embodiment 3 during a second defrost operation. FIG. 10 is a circuit diagram showing a schematic configuration of a refrigeration cycle apparatus according to Modification 2 of Embodiment 3 during a second defrost operation. FIG. 11 is a circuit diagram showing a schematic configuration of a refrigeration cycle apparatus according to Modification 2 of Embodiment 3 during a second defrost operation.

[0011] Embodiments of the present disclosure will be described below with reference to the drawings. The present disclosure is not limited to the following embodiments and can be modified in various ways without departing from the spirit and scope of the present disclosure. Furthermore, the present disclosure includes all possible combinations of the configurations shown in the following embodiments. In particular, the combinations of components are not limited to the combinations in each embodiment; components described in one embodiment can be applied to another embodiment. In the following description, directional terms (e.g., "up," "down," "right," "left," "front," "rear," etc.) are used as appropriate to facilitate understanding, but these are for explanatory purposes and do not limit the present disclosure. In each drawing, components designated with the same reference numerals are identical or equivalent, and this applies throughout the entire specification. Note that the relative dimensional relationships or shapes of each component in each drawing may differ from those in actuality.

[0012] Embodiment 1. A refrigeration cycle apparatus according to embodiment 1 will be described. The refrigeration cycle apparatus according to this embodiment is used for refrigeration or air conditioning purposes, such as refrigerators, freezers, vending machines, air conditioners, refrigeration systems, and water heaters. Fig. 1 is a circuit diagram showing a schematic configuration of the refrigeration cycle apparatus according to this embodiment during heating operation. In Fig. 1 and the drawings described below, the blackened portions of the valve symbols indicate that the flow paths are open.

[0013] 1 , the refrigeration cycle apparatus 200 includes a heat source unit 201 and a heat load unit 202. The heat source unit 201 and the heat load unit 202 are connected via a gas pipe 203 and a liquid pipe 204.

[0014] The heat source unit 201 is equipped with a compressor 10, a flow path switching device 11, a flow control valve 12, flow path switching devices 13a and 13b, expansion devices 32a and 32b, outdoor heat exchangers 40a and 40b, and outdoor fans 41a and 41b. The heat load unit 202 is equipped with an indoor heat exchanger 20, an indoor fan 21, and an expansion device 31.

[0015] The outdoor heat exchanger 40a and the outdoor heat exchanger 40b are provided in parallel in the refrigerant circuit during heating operation of the refrigeration cycle apparatus 200. The refrigerant circuit during heating operation has, as main circuits, a first path passing through the outdoor heat exchanger 40a and a second path passing through the outdoor heat exchanger 40b.

[0016] The first path passes through the compressor 10, the flow path switching device 11, the branching section 14a, the branching section 14b, the flow control valve 12, the indoor heat exchanger 20, the expansion device 31, the branching section 33, the expansion device 32a, the outdoor heat exchanger 40a, the flow path switching device 13a, the branching section 42, and the flow path switching device 11 in this order, and returns to the compressor 10. The second path passes through the compressor 10, the flow path switching device 11, the branching section 14a, the branching section 14b, the flow control valve 12, the indoor heat exchanger 20, the expansion device 31, the branching section 33, the expansion device 32b, the outdoor heat exchanger 40b, the flow path switching device 13b, the branching section 42, and the flow path switching device 11 in this order, and returns to the compressor 10. The second path branches from the first path at the branching section 33 and merges with the first path at the branching section 42.

[0017] The refrigerant circuit of the refrigeration cycle device 200 also has, as paths during defrosting operation, a third path for defrosting the outdoor heat exchanger 40a and a fourth path for defrosting the outdoor heat exchanger 40b.

[0018] The third path passes through the compressor 10, flow path switching device 11, flow path switching device 13a, outdoor heat exchanger 40a, expansion device 32a, expansion device 32b, outdoor heat exchanger 40b, flow path switching device 13b, and flow path switching device 11 in this order, and returns to the compressor 10. The fourth path passes through the compressor 10, flow path switching device 11, flow path switching device 13b, outdoor heat exchanger 40b, expansion device 32b, expansion device 32a, outdoor heat exchanger 40a, flow path switching device 13a, and flow path switching device 11 in this order, and returns to the compressor 10.

[0019] The compressor 10 draws in a refrigerant, compresses it, and discharges it in a high-temperature, high-pressure state. The refrigerant compressed by the compressor 10 is discharged and sent to the flow path switching device 11. The compressor 10 is configured as, for example, a rotary compressor, a scroll compressor, a screw compressor, or a reciprocating compressor. The compressor 10 may be a high-pressure shell type or a low-pressure shell type, but the oil outflow suppression effect of this embodiment is particularly significant when the compressor 10 is a high-pressure shell type.

[0020] The flow path switching device 11 is, for example, a four-way valve that switches the direction of refrigerant flow in the refrigerant circuit. The flow path switching device 11 is controlled by a control device 210, which will be described later. During heating operation, the flow path switching device 11 is switched to state A, in which the discharge side of the compressor 10 is connected to the indoor heat exchanger 20 and the suction side of the compressor 10 is connected to the outdoor heat exchangers 40a and 40b. During cooling operation, the flow path switching device 11 is switched to state B, in which the discharge side of the compressor 10 is connected to the outdoor heat exchangers 40a and 40b and the suction side of the compressor 10 is connected to the indoor heat exchanger 20. In this embodiment, during defrosting operation, the flow path switching device 11 is set to state B, the same as during cooling operation.

[0021] The flow rate adjustment valve 12 is provided between the branch portion 14b and the indoor heat exchanger 20. The flow rate adjustment valve 12 is an on-off valve that can be fully closed. The flow rate adjustment valve 12 is controlled by the control device 210. The branch portion 14a and the branch portion 14b are both provided between the flow path switching device 11 and the flow rate adjustment valve 12.

[0022] The flow path switching device 13a is, for example, a three-way valve. The flow path switching device 13a is provided in the first path between the outdoor heat exchanger 40a and the branching portion 42. The flow path switching device 13a has a first port P1, a second port P2, and a third port P3. The first port P1 is connected to the branching portion 42 side of the first path. The second port P2 is connected to the outdoor heat exchanger 40a side of the first path. The third port P3 is connected to the branching portion 14a via a refrigerant pipe. The flow path switching device 13a is controlled by the control device 210. The flow path switching device 13a can be set to at least a state C in which the first port P1 and the second port P2 are connected to each other and the third port P3 is closed, and a state D in which the second port P2 and the third port P3 are connected to each other and the first port P1 is closed. During heating operation, cooling operation, and defrosting operation of the outdoor heat exchanger 40a, the flow path switching device 13a is set to state C. On the other hand, during defrosting operation of the outdoor heat exchanger 40b, the flow path switching device 13a is set to state D.

[0023] The flow path switching device 13b is, for example, a three-way valve. The flow path switching device 13b is provided in the second path between the outdoor heat exchanger 40b and the branching portion 42. The flow path switching device 13b has a first port P1, a second port P2, and a third port P3. The first port P1 is connected to the branching portion 42 side of the second path. The second port P2 is connected to the outdoor heat exchanger 40b side of the second path. The third port P3 is connected to the branching portion 14b via a refrigerant pipe. The flow path switching device 13b is controlled by the control device 210. The flow path switching device 13b can be set to at least a state C in which the first port P1 and the second port P2 are connected to each other and the third port P3 is closed, and a state D in which the second port P2 and the third port P3 are connected to each other and the first port P1 is closed. During heating operation, cooling operation, and defrosting operation of the outdoor heat exchanger 40b, the flow path switching device 13b is set to state C. On the other hand, during defrosting operation of the outdoor heat exchanger 40a, the flow path switching device 13b is set to state D.

[0024] The indoor heat exchanger 20 is a heat exchanger that exchanges heat between the refrigerant flowing through the refrigerant circuit and air supplied by the indoor blower 21. The indoor blower 21 is controlled by a control device 210.

[0025] The expansion device 31 is provided between the indoor heat exchanger 20 and the branch section 33. The expansion device 31 is a fully closable expansion valve. For example, an electronic expansion valve is used as the expansion device 31. The expansion device 31 is controlled by the control device 210.

[0026] The expansion device 32a is provided between the branching section 33 and the outdoor heat exchanger 40a. The expansion device 32b is provided between the branching section 33 and the outdoor heat exchanger 40b. The expansion devices 32a and 32b are each a fully closable expansion valve. For example, electronic expansion valves are used as the expansion devices 32a and 32b. The expansion devices 32a and 32b are controlled by the control device 210.

[0027] The outdoor heat exchanger 40a is a heat exchanger that exchanges heat between the refrigerant flowing through the refrigerant circuit and air supplied by the outdoor fan 41a. The outdoor heat exchanger 40b is a heat exchanger that exchanges heat between the refrigerant flowing through the refrigerant circuit and air supplied by the outdoor fan 41b. The outdoor fan 41a and the outdoor fan 41b are controlled by the control device 210.

[0028] The control device 210 is configured to control the entire refrigeration cycle device including the compressor 10, the flow path switching device 11, the flow control valve 12, the expansion device 31, the expansion device 32a, the expansion device 32b, the indoor blower 21, and the outdoor blowers 41a and 41b. These controls may be realized by a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., or may be realized by dedicated hardware. The control device 210 may be provided in the heat source unit 201 or in the heat load unit 202.

[0029] Next, the operation during heating operation will be described. FIG. 2 is a diagram showing the control contents of each operation mode by the control device of the refrigeration cycle apparatus according to this embodiment. As shown in FIG. 2, during heating operation, the flow path switching device 11 is set to state A. This connects the discharge side of the compressor 10 to the indoor heat exchanger 20, and connects the suction side of the compressor 10 to the outdoor heat exchangers 40a and 40b. The flow path switching devices 13a and 13b are both set to state C. The flow control valve 12 is set to fully open. The expansion device 31 is set to fully open. The expansion device 32a is controlled, for example, so that the degree of superheat of the outlet refrigerant of the outdoor heat exchanger 40a is constant. The expansion device 32b is controlled, for example, so that the degree of superheat of the outlet refrigerant of the outdoor heat exchanger 40b is constant. The outdoor blowers 41a and 41b are set to on.

[0030] During heating operation, high-temperature, high-pressure gas refrigerant discharged from the compressor 10 flows into the indoor heat exchanger 20 via the flow switching device 11, the flow control valve 12, and the gas pipe 203. During heating operation, the indoor heat exchanger 20 functions as a condenser. That is, in the indoor heat exchanger 20, heat exchange occurs between the refrigerant flowing therethrough and the indoor air blown by the indoor blower 21, and the heat of condensation of the refrigerant is dissipated to the indoor air. As a result, the refrigerant that has flowed into the indoor heat exchanger 20 condenses into high-pressure liquid refrigerant. Furthermore, the indoor air blown by the indoor blower 21 is heated by the heat dissipation effect of the refrigerant.

[0031] The high-pressure liquid refrigerant flowing out of the indoor heat exchanger 20 flows into the throttling device 32a and the throttling device 32b via the throttling device 31 and the liquid pipe 204, where it is decompressed and becomes a low-pressure two-phase refrigerant. The low-pressure two-phase refrigerant flows into the outdoor heat exchangers 40a and 40b. During heating operation, the outdoor heat exchangers 40a and 40b function as evaporators. That is, the outdoor heat exchangers 40a and 40b exchange heat between the refrigerant flowing therethrough and the outdoor air blown by the outdoor fans 41a and 41b, and the refrigerant absorbs heat of evaporation from the outdoor air. As a result, the refrigerant flowing into the outdoor heat exchangers 40a and 40b evaporates and becomes a low-pressure gas refrigerant or two-phase refrigerant. The low-pressure gas refrigerant or two-phase refrigerant flowing out of the outdoor heat exchanger 40a passes through the flow switching device 13a and the flow switching device 11 and is drawn into the compressor 10. The gas refrigerant or two-phase refrigerant flowing out from the outdoor heat exchanger 40b passes through the flow switching device 13b and the flow switching device 11 and is drawn into the compressor 10. In the heating operation, the above cycle is continuously repeated.

[0032] When the heating operation is performed under conditions where the outdoor air temperature is low, condensed water freezes and frosts on the outdoor heat exchangers 40a and 40b, which may make it impossible to continue the heating operation. For this reason, defrosting operations are periodically performed to defrost the outdoor heat exchangers 40a and 40b. The defrosting operations include a first defrosting operation to defrost one outdoor heat exchanger 40a and a second defrosting operation to defrost the other outdoor heat exchanger 40b. In the first defrosting operation, the refrigerant flows through the third path, and in the second defrosting operation, the refrigerant flows through the fourth path.

[0033] The first defrosting operation and the second defrosting operation are alternately performed after, for example, the heating operation. That is, the first defrosting operation is performed after the heating operation or after the second defrosting operation. The second defrosting operation is performed after the heating operation or after the first defrosting operation. After defrosting is completed by the first defrosting operation and the second defrosting operation, the operation returns to the heating operation.

[0034] FIG. 3 is a circuit diagram showing a schematic configuration of the refrigeration cycle apparatus according to this embodiment during the first defrosting operation. As shown in FIG. 3, during the first defrosting operation, the flow path switching device 11 is set to state B. The flow path switching device 13a is set to state C. The flow path switching device 13b is set to state D. As a result, the discharge side of the compressor 10 is connected to the outdoor heat exchanger 40a, and the suction side of the compressor 10 is connected to the outdoor heat exchanger 40b. The flow control valve 12 is set to fully closed. The expansion device 31 is set to fully closed. The expansion devices 32a and 32b are controlled so that a pressure difference is generated between the outdoor heat exchanger 40a and the outdoor heat exchanger 40b. The outdoor blower 41a is set to off or on. The outdoor blower 41b is set to on.

[0035] The high-temperature, high-pressure gas refrigerant discharged from the compressor 10 flows into the outdoor heat exchanger 40a via the flow path switching device 11 and the flow path switching device 13a. During the first defrosting operation, the outdoor heat exchanger 40a functions as a condenser. That is, in the outdoor heat exchanger 40a, heat is exchanged between the refrigerant flowing therethrough and the frost on the surface of the outdoor heat exchanger 40a, and the frost melts due to the heat of condensation of the refrigerant. This defrosts the outdoor heat exchanger 40a. The refrigerant flows out of the outdoor heat exchanger 40a as a high-pressure two-phase refrigerant or liquid refrigerant.

[0036] The high-pressure two-phase refrigerant or liquid refrigerant flowing out of the outdoor heat exchanger 40a is decompressed by the expansion device 32a and the expansion device 32b, becoming a low-pressure two-phase refrigerant and flowing into the outdoor heat exchanger 40b. During the first defrosting operation, the outdoor heat exchanger 40b functions as an evaporator. That is, in the outdoor heat exchanger 40b, heat is exchanged between the refrigerant flowing therethrough and the outdoor air blown by the outdoor blower 41b. The refrigerant absorbs heat from the outdoor air and evaporates, becoming a low-pressure gas refrigerant. The low-pressure gas refrigerant flowing out of the outdoor heat exchanger 40b is drawn into the compressor 10 via the flow path switching device 13b and the flow path switching device 11.

[0037] In this manner, during the first defrost operation, the compressor 10, the flow path switching device 11, the flow path switching device 13a, the outdoor heat exchanger 40a, the expansion device 32a, the expansion device 32b, the outdoor heat exchanger 40b, the flow path switching device 13b, the flow path switching device 11, and the compressor 10 are connected in this order, thereby forming a third path, which is a refrigerant path during the first defrost operation.

[0038] When switching from heating operation to first defrost operation, the flow control valve 12 and the expansion device 31 are switched from fully open to fully closed. As a result, the liquid refrigerant that was present in the indoor heat exchanger 20 during heating operation is trapped between the flow control valve 12 and the expansion device 31 and remains in the indoor heat exchanger 20 during the first defrost operation. Therefore, even if the refrigerant pressure in the indoor heat exchanger 20 is higher than the refrigerant discharge pressure of the compressor 10 during the first defrost operation, the amount of liquid refrigerant flowing from the indoor heat exchanger 20 to the compressor 10 can be reduced. Therefore, breakdowns in the compressor 10 can be suppressed.

[0039] Furthermore, during the first defrosting operation, the outdoor blower 41b operates, promoting evaporation of the refrigerant in the outdoor heat exchanger 40b. This further reduces the amount of liquid refrigerant flowing into the compressor 10. Furthermore, by operating the outdoor heat exchanger 40b, which is not subject to defrosting, as an evaporator, the latent heat of the refrigerant can be used for defrosting, shortening the defrosting time. This allows for an early return to heating operation from defrosting operation, improving heating capacity.

[0040] After the first defrost operation is completed, the second defrost operation is performed. The second defrost operation may be performed after the first defrost operation is completed, with a heating operation in between. Although the refrigerant circuit is not illustrated, the second defrost operation is performed in the same manner as the first defrost operation. During the second defrost operation, the flow path switching device 11 is set to state B. The flow path switching device 13a is set to state D. The flow path switching device 13b is set to state C. As a result, the discharge side of the compressor 10 is connected to the outdoor heat exchanger 40b, and the suction side of the compressor 10 is connected to the outdoor heat exchanger 40a. The flow control valve 12 is set to fully closed. The expansion device 31 is set to fully closed. The expansion devices 32a and 32b are controlled so that a pressure difference is generated between the outdoor heat exchanger 40a and the outdoor heat exchanger 40b. The outdoor blower 41a is set to on. The exterior blower 41b is set to either off or on.

[0041] During the second defrosting operation, the compressor 10, the flow path switching device 11, the flow path switching device 13b, the outdoor heat exchanger 40b, the expansion device 32b, the expansion device 32a, the outdoor heat exchanger 40a, the flow path switching device 13a, the flow path switching device 11, and the compressor 10 are connected in this order. This forms a fourth path, which is a refrigerant path during the second defrosting operation.

[0042] During the second defrost operation, the flow control valve 12 and the expansion device 31 are also set to fully closed. As a result, the liquid refrigerant that was present in the indoor heat exchanger 20 during the heating operation is trapped between the flow control valve 12 and the expansion device 31 and remains in the indoor heat exchanger 20 during the second defrost operation. Therefore, even if the refrigerant pressure in the indoor heat exchanger 20 is higher than the refrigerant discharge pressure of the compressor 10 during the second defrost operation, the amount of liquid refrigerant flowing from the indoor heat exchanger 20 into the compressor 10 can be reduced. Therefore, breakdowns in the compressor 10 can be suppressed.

[0043] Furthermore, during the second defrosting operation, the outdoor blower 41a operates, promoting evaporation of the refrigerant in the outdoor heat exchanger 40a. This further reduces the amount of liquid refrigerant flowing into the compressor 10. Furthermore, by operating the outdoor heat exchanger 40a, which is not the target for defrosting, as an evaporator, the latent heat of the refrigerant can be utilized to shorten the defrosting time. This allows for an early return to heating operation from defrosting operation, improving heating capacity.

[0044] After the second defrosting operation is completed, if it is determined that a certain amount of frost has formed on the outdoor heat exchanger 40 a, the first defrosting operation may be performed again. If it is determined that defrosting of all the outdoor heat exchangers 40 a, 40 b is completed, the flow control valve 12 and the expansion device 31 are opened, and the heating operation is resumed.

[0045] In this embodiment, it is sufficient that the flow control valve 12 and the expansion device 31 in the first path can cause the refrigerant to stagnate in the indoor heat exchanger 20, and that the outdoor heat exchangers 40a and 40b can be operated separately as an evaporator and a condenser. Therefore, the configuration of the path from the compressor 10 to the outdoor heat exchangers 40a and 40b during defrosting operation may be different.

[0046] FIG. 4 is a circuit diagram showing a schematic configuration of a refrigeration cycle apparatus according to a first modification of the present embodiment. As shown in FIG. 4 , in this modification, four-way valves are used as the flow path switching devices 13a and 13b. The flow path switching device 13a has a first port P1, a second port P2, a third port P3, and a fourth port P4. The first port P1 is connected to the branching portion 42 side of the first path. The second port P2 is connected to the outdoor heat exchanger 40a side of the first path. The third port P3 is connected to the branching portion 14a via a refrigerant pipe. The fourth port P4 is closed. The flow path switching device 13a can be set to at least a state C in which the first port P1 and the second port P2 are in communication with each other and the third port P3 and the fourth port P4 are in communication with each other, and a state D in which the second port P2 and the third port P3 are in communication with each other and the fourth port P4 is in communication with the first port P1. The flow path switching device 13b has the same configuration as the flow path switching device 13a. In this modified example, the flow path switching device 13b can be operated in the same manner as in FIGS.

[0047] Fig. 5 is a circuit diagram showing a schematic configuration of a refrigeration cycle apparatus according to Modification 2 of the present embodiment during heating operation. Fig. 6 is a circuit diagram showing a schematic configuration of a refrigeration cycle apparatus according to Modification 2 of the present embodiment during first defrost operation. As shown in Figs. 5 and 6, in this modification, the path from the compressor 10 to the outdoor heat exchangers 40a, 40b during defrost operation is configured by a combination of two flow path switching devices 13a, 13b with a four-way valve structure and two on-off valves 18a, 18b. This modification can also be operated in the same manner as in Figs. 1 to 3.

[0048] As described above, the refrigeration cycle apparatus 200 includes a refrigerant circuit having the compressor 10, the indoor heat exchanger 20, the first outdoor heat exchanger 40a, and the second outdoor heat exchanger 40b, and a control device 210. The refrigerant circuit has a first path and a second path as refrigerant paths during heating operation when the indoor heat exchanger 20 functions as a condenser. The first path is a path from the compressor 10 through the flow control valve 12, the indoor heat exchanger 20, the first throttling device 31, the second throttling device 32a, the first outdoor heat exchanger 40a, and the first flow switching device 13a, and returns to the compressor 10. The second path is a path from the compressor 10 through the flow control valve 12, the indoor heat exchanger 20, the first throttling device 31, the third throttling device 32b, the second outdoor heat exchanger 40b, and the second flow switching device 13b, and returns to the compressor 10.

[0049] The refrigerant circuit has a third path as a refrigerant path during a first defrosting operation in which the first outdoor heat exchanger 40a functions as a condenser and the second outdoor heat exchanger 40b functions as an evaporator. The third path runs from the compressor 10 through the first flow switching device 13a, the first outdoor heat exchanger 40a, the second throttling device 32a, the third throttling device 32b, the second outdoor heat exchanger 40b, and the second flow switching device 13b before returning to the compressor 10. The refrigerant circuit has a fourth path as a refrigerant path during a second defrosting operation in which the second outdoor heat exchanger 40b functions as a condenser and the first outdoor heat exchanger 40a functions as an evaporator. The fourth path is a path that runs from the compressor 10 through the second flow switching device 13b, the second outdoor heat exchanger 40b, the third throttling device 32b, the second throttling device 32a, the first outdoor heat exchanger 40a, and the first flow switching device 13a, and returns to the compressor 10. During the first defrosting operation and the second defrosting operation, the control device 210 fully closes the flow control valve 12 and the first throttling device 31.

[0050] According to this configuration, during the first defrost operation and the second defrost operation, the liquid refrigerant that was present in the indoor heat exchanger 20 during heating operation is trapped between the flow control valve 12 and the expansion device 31 and remains in the indoor heat exchanger 20. Therefore, even if the refrigerant pressure in the indoor heat exchanger 20 is higher than the refrigerant discharge pressure of the compressor 10 during the defrost operation, the amount of liquid refrigerant flowing from the indoor heat exchanger 20 into the compressor 10 can be reduced. Therefore, breakdowns in the compressor 10 can be suppressed.

[0051] Furthermore, with this configuration, since one outdoor heat exchanger can recover the latent heat of evaporation of the refrigerant while the other outdoor heat exchanger is defrosted, the amount of frost defrosted per unit time can be increased compared to defrosting methods without an evaporator, thereby shortening the defrosting time.

[0052] In the refrigeration cycle apparatus 200 according to this embodiment, a first branch portion 14a and a second branch portion 14b are provided in the first and second paths between the compressor 10 and the flow control valve 12. The first flow path switching device 13a is a valve having a first port P1 and a second port P2 provided on the first path and a third port P3 connected to the first branch portion 14a via a refrigerant pipe. The second flow path switching device 13b is a valve having a first port P1 and a second port P2 provided on the second path and a third port P3 connected to the second branch portion 14b via a refrigerant pipe. This configuration facilitates the construction of a refrigerant circuit.

[0053] The refrigeration cycle apparatus 200 according to this embodiment further includes a first outdoor fan 41a that supplies air to the first outdoor heat exchanger 40a, and a second outdoor fan 41b that supplies air to the second outdoor heat exchanger 40b. The control device 210 operates the second outdoor fan 41b during the first defrosting operation, and operates the first outdoor fan 41a during the second defrosting operation.

[0054] According to this configuration, during the first defrost operation and the second defrost operation, the evaporation of the refrigerant in the outdoor heat exchanger functioning as an evaporator is promoted, thereby further reducing the amount of liquid refrigerant flowing into the compressor 10.

[0055] Embodiment 2 A refrigeration cycle apparatus according to embodiment 2 will be described. Fig. 7 is a circuit diagram showing a schematic configuration of the refrigeration cycle apparatus according to this embodiment during the second defrosting operation. As shown in Fig. 7, the refrigeration cycle apparatus of this embodiment has a circuit configuration similar to the circuit configuration shown in Fig. 1.

[0056] Fig. 8 is a diagram showing the control contents of each operation mode by the control device of the refrigeration cycle apparatus according to this embodiment. As shown in Fig. 8, the flow path switching device 11 of this embodiment is set to state A in all of the heating operation, the first defrost operation, and the second defrost operation. That is, in this embodiment, the flow path switching device 11 is not switched when transitioning from the heating operation to the first defrost operation or the second defrost operation. Although not shown in Fig. 8, during the cooling operation, the flow path switching device 11 is set to state B. In the first defrost operation and the second defrost operation, the flow control valve 12 and the expansion device 31 are fully closed, as in the first embodiment.

[0057] The second defrosting operation will be described with reference to Figure 7. During the second defrosting operation, the flow path switching device 13a is set to state C, and the flow path switching device 13b is set to state D. As a result, the discharge side of the compressor 10 is connected to the outdoor heat exchanger 40b, and the suction side of the compressor 10 is connected to the outdoor heat exchanger 40a.

[0058] The high-temperature, high-pressure gas refrigerant discharged from the compressor 10 flows into the outdoor heat exchanger 40b via the flow path switching device 11 and the flow path switching device 13b. During the second defrosting operation, the outdoor heat exchanger 40b functions as a condenser. That is, in the outdoor heat exchanger 40b, heat is exchanged between the refrigerant flowing therethrough and the frost on the surface of the outdoor heat exchanger 40b, and the frost melts due to the heat of condensation of the refrigerant. This defrosts the outdoor heat exchanger 40b. The refrigerant flows out of the outdoor heat exchanger 40b as a high-pressure two-phase refrigerant or liquid refrigerant.

[0059] The high-pressure two-phase refrigerant or liquid refrigerant flowing out of the outdoor heat exchanger 40b is decompressed by the expansion device 32b and the expansion device 32a, becoming a low-pressure two-phase refrigerant and flowing into the outdoor heat exchanger 40a. During the second defrosting operation, the outdoor heat exchanger 40a functions as an evaporator. That is, the outdoor heat exchanger 40a exchanges heat between the refrigerant flowing therethrough and the outdoor air blown by the outdoor blower 41a. The refrigerant absorbs heat from the outdoor air and evaporates, becoming a low-pressure gas refrigerant. The low-pressure gas refrigerant flowing out of the outdoor heat exchanger 40a is drawn into the compressor 10 via the flow path switching device 13a and the flow path switching device 11.

[0060] In this manner, during the second defrosting operation, the compressor 10, the flow path switching device 11, the flow path switching device 13b, the outdoor heat exchanger 40b, the expansion device 32b, the expansion device 32a, the outdoor heat exchanger 40a, the flow path switching device 13a, the flow path switching device 11, and the compressor 10 are connected in this order. This forms a path for the second defrosting operation. Although not shown in the figure, the first defrosting operation is also performed in the same manner as the second defrosting operation.

[0061] As described above, in the refrigeration cycle apparatus 200 according to this embodiment, the refrigerant circuit further includes the flow path switching device 11. The flow path switching device 11 is a four-way valve that switches the flow path between the heating operation and the cooling operation. The flow path of the flow path switching device 11 cannot be switched between the heating operation and the first defrost operation, or between the heating operation and the second defrost operation.

[0062] According to this configuration, when the operation mode is switched from the heating mode to the first defrosting mode or the second defrosting mode, the stop time of the compressor 10 can be shortened, and therefore the time required to return to the heating mode can be shortened.

[0063] Embodiment 3. A refrigeration cycle apparatus according to Embodiment 3 will be described. FIG. 9 is a circuit diagram showing a schematic configuration of the refrigeration cycle apparatus according to this embodiment during the second defrosting operation. As shown in FIG. 9, the refrigeration cycle apparatus 200 includes, as outdoor-side units, a compressor-mounted unit 205 and one or more outdoor heat exchanger units 206a, 206b. The compressor-mounted unit 205, the outdoor heat exchanger unit 206a, and the outdoor heat exchanger unit 206b are formed separately from one another. The compressor-mounted unit 205 is connected to the outdoor heat exchanger unit 206a and the outdoor heat exchanger unit 206b via refrigerant piping. The substantial circuit configuration of the refrigeration cycle apparatus 200 is similar to the circuit configurations shown in FIGS. 1 and 7.

[0064] The compressor mounting unit 205 is equipped with the compressor 10, the flow path switching device 11, the flow path switching devices 13a and 13b, and the flow control valve 12. The outdoor heat exchanger unit 206a is equipped with the expansion device 32a, the outdoor heat exchanger 40a, and the outdoor blower 41a. The outdoor heat exchanger unit 206b is equipped with the expansion device 32b, the outdoor heat exchanger 40b, and the outdoor blower 41b.

[0065] For example, during the second defrost operation, if frost forms on the outdoor heat exchanger 40a, which serves as an evaporator, the capacity of the outdoor heat exchanger 40a decreases. As a result, there is a risk that liquid refrigerant flowing out of the outdoor heat exchanger 40a due to poor evaporation may flow into the compressor 10. In contrast, in the present embodiment, the compressor 10 and the outdoor heat exchangers 40a and 40b are mounted in separate units, thereby ensuring a large piping volume from each of the outdoor heat exchangers 40a and 40b to the compressor 10. As a result, even if the capacity of the outdoor heat exchanger, which serves as an evaporator, decreases during the first defrost operation and the second defrost operation, the amount of liquid refrigerant flowing from the outdoor heat exchanger to the compressor 10 can be reduced.

[0066] Fig. 10 is a circuit diagram showing a schematic configuration of a refrigeration cycle apparatus according to Modification 1 of this embodiment during the second defrosting operation. Fig. 11 is a circuit diagram showing a schematic configuration of a refrigeration cycle apparatus according to Modification 2 of this embodiment during the second defrosting operation. Fig. 12 is a circuit diagram showing a schematic configuration of a refrigeration cycle apparatus according to Modification 3 of this embodiment during the first defrosting operation.

[0067] As shown in Figures 10 to 12, the refrigeration cycle apparatus 200 has, as outdoor-side units, a compressor-mounted unit 205, a relay unit 207, and one or more outdoor heat exchanger units 206a, 206b. The substantial circuit configuration of Figure 10 is similar to the circuit configurations shown in Figures 1 and 7. The substantial circuit configuration of Figure 11 is similar to the circuit configuration shown in Figure 4. The substantial circuit configuration of Figure 12 is similar to the circuit configuration shown in Figure 5.

[0068] The compressor mounting unit 205 is equipped with a compressor 10 and a flow path switching device 11. The relay unit 207 is equipped with flow path switching devices 13a and 13b and a flow control valve 12. The outdoor heat exchanger unit 206a is equipped with an expansion device 32a, an outdoor heat exchanger 40a, and an outdoor blower 41a. The outdoor heat exchanger unit 206b is equipped with an expansion device 32b, an outdoor heat exchanger 40b, and an outdoor blower 41b.

[0069] 10 to 12, heat is retained during heating operation in the piping from the compressor-mounted unit 205 to the relay unit 207, which can be installed closer to the heat load unit 202. This heat can be used for defrosting during defrosting operation, thereby shortening the defrosting time and shortening the time until heating is restored.

[0070] As described above, the refrigeration cycle apparatus 200 according to this embodiment further includes the compressor mounting unit 205 and one or more outdoor heat exchanger units 206 a, 206 b. The compressor 10 is mounted in the compressor mounting unit 205. The first outdoor heat exchanger 40 a and the second outdoor heat exchanger 40 b are mounted in the outdoor heat exchanger unit 206 a and the outdoor heat exchanger unit 206 b, respectively.

[0071] According to this configuration, the compressor 10 and the first and second outdoor heat exchangers 40a, 40b are mounted in separate units, thereby ensuring a large piping volume from each of the first and second outdoor heat exchangers 40a, 40b to the compressor 10. Therefore, even if the capacity of the outdoor heat exchanger serving as an evaporator decreases during the first defrost operation and the second defrost operation, the amount of liquid refrigerant flowing from the outdoor heat exchanger to the compressor 10 can be reduced.

[0072] Embodiment 4 A refrigeration cycle apparatus according to embodiment 4 will be described. In this embodiment, for example, a refrigeration cycle apparatus having the same configuration as that shown in Fig. 7 is used. Fig. 13 is a diagram showing the control contents of each operation mode by the control device of the refrigeration cycle apparatus according to this embodiment.

[0073] 13, the refrigeration cycle apparatus of this embodiment can perform a first heating defrost operation and a second heating defrost operation in addition to a heating operation, a first defrost operation, and a second defrost operation. In the first heating defrost operation and the second heating defrost operation, the flow control valve 12 and the expansion device 31 are opened. For example, the flow control valve 12 is fully opened, and the expansion device 31 is controlled to a required opening degree.

[0074] The first heating defrosting operation is an operation in which high-temperature, high-pressure refrigerant discharged from the compressor 10 is supplied to both the outdoor heat exchanger 40a and the indoor heat exchanger 20, and heating is performed while defrosting the outdoor heat exchanger 40a. That is, in the first heating defrosting operation, the refrigerant flows through both the second path and the third path.

[0075] The second heating defrosting operation is an operation in which high-temperature, high-pressure refrigerant discharged from the compressor 10 is supplied to both the outdoor heat exchanger 40b and the indoor heat exchanger 20, and heating is performed while defrosting the outdoor heat exchanger 40b. That is, in the second heating defrosting operation, the refrigerant flows through both the first path and the fourth path.

[0076] In this embodiment, the first heating defrosting operation and the second heating defrosting operation are permitted to be performed only when the outdoor air temperature is higher than a threshold temperature T. The outdoor air temperature is detected, for example, by a temperature sensor provided in the heat source unit 201. The threshold temperature T is stored in advance in the memory of the control device 210. The threshold temperature T is set, for example, to a temperature within a range of -10°C or higher and -2°C or lower. This makes it possible to suppress a decrease in the average heating capacity relative to the outdoor air temperature.

[0077] For example, when the defrosting start condition is satisfied during heating operation and the outdoor air temperature is higher than the threshold temperature T, the first heating defrosting operation and the second heating defrosting operation are alternately executed. When the defrosting start condition is satisfied during heating operation and the outdoor air temperature is higher than the threshold temperature T, the first defrosting operation and the second defrosting operation are alternately executed.

[0078] In this embodiment, when the outdoor air temperature is high and the evaporation saturation temperature is 0° C. or higher, no defrosting operation is performed, and heating operation is performed in which all outdoor heat exchangers 40 a, 40 b function as evaporators, thereby improving heating capacity.

[0079] As described above, in the refrigeration cycle apparatus 200 according to this embodiment, the control device 210 executes the first heating defrosting operation and the second heating defrosting operation only when the outdoor air temperature is higher than the threshold temperature T. The first heating defrosting operation is an operation in which the flow control valve 12 and the first throttling device 31 are set to an open state, refrigerant flows through the second and third paths, and heating is performed while defrosting the first outdoor heat exchanger 40a. The second heating defrosting operation is an operation in which the flow control valve 12 and the first throttling device 31 are set to an open state, refrigerant flows through the first and fourth paths, and heating is performed while defrosting the second outdoor heat exchanger 40b.

[0080] According to this configuration, under conditions where the amount of frost formed per unit time is small, it is possible to defrost the first outdoor heat exchanger 40 a and the second outdoor heat exchanger 40 b while continuing heating. On the other hand, under conditions where the amount of frost formed per unit time is large, if the first heating defrosting operation and the second heating defrosting operation are performed, the defrosting capacity will be insufficient and the heating capacity will decrease, so the first heating defrosting operation and the second heating defrosting operation are not performed.

[0081] In the refrigeration cycle apparatus 200 according to this embodiment, the control device 210 executes the first defrosting operation and the second defrosting operation when the outdoor air temperature is lower than 0°C.

[0082] According to this configuration, under conditions where the amount of frost formed per hour is large, the outdoor heat exchangers 40a, 40b can be defrosted without supplying heat to the indoor heat exchanger 20. This ensures defrosting capacity and shortens the defrosting time, thereby improving the average heating capacity per hour.

[0083] REFRIGERATION CYCLE DEVICE, 10 COMPRESSOR, 11 FLOW CHANGING DEVICE (FOUR-WAY VALVE), 12 FLOW CONTROL VALVE, 13a FLOW CHANGING DEVICE (FIRST FLOW CHANGING DEVICE), 13b FLOW CHANGING DEVICE (SECOND FLOW CHANGING DEVICE), 14a BRANCHING PORTION (FIRST BRANCHING PORTION), 14b BRANCHING PORTION (SECOND BRANCHING PORTION), 18a ON / OFF VALVE, 18b ON / OFF VALVE, 20 INDOOR HEAT EXCHANGER, 21 INDOOR BLOWER, 31 THROTTING DEVICE (FIRST THROTTING DEVICE), 32a THROTTING DEVICE (SECOND THROTTING DEVICE), 32b THROTTING DEVICE (SECOND THROTTING DEVICE), 33 BRANCHING PORTION, 40a OUTDOOR HEAT EXCHANGER (FIRST OUTDOOR HEAT EXCHANGER), 40b OUTDOOR HEAT EXCHANGER (SECOND OUTDOOR HEAT EXCHANGER), 41a OUTDOOR BLOWER (FIRST OUTDOOR BLOWER), 41b OUTDOOR BLOWER (SECOND OUTDOOR BLOWER), 42 BRANCHING PORTION, 200 REFRIGERATION CYCLE DEVICE, 201 HEAT SOURCE UNIT, 202 Heat load unit, 203 gas pipe, 204 liquid pipe, 205 compressor mounting unit, 206a outdoor heat exchanger unit, 206b outdoor heat exchanger unit, 207 relay unit, 210 control device.

Claims

1. a refrigerant circuit having a compressor, an indoor heat exchanger, a first outdoor heat exchanger, and a second outdoor heat exchanger; a control device; the refrigerant circuit has a first path and a second path as paths of the refrigerant during heating operation in which the indoor heat exchanger functions as a condenser, the first path is a path that runs from the compressor through a flow control valve, the indoor heat exchanger, a first throttle device, a second throttle device, the first outdoor heat exchanger, and a first flow path switching device and returns to the compressor; the second path is a path that runs from the compressor through the flow rate control valve, the indoor heat exchanger, the first throttle device, the third throttle device, the second outdoor heat exchanger, and a second flow path switching device and returns to the compressor, the refrigerant circuit has a third path as a path of the refrigerant during a first defrosting operation in which the first outdoor heat exchanger functions as a condenser and the second outdoor heat exchanger functions as an evaporator, the third path is a path that runs from the compressor through the first flow path switching device, the first outdoor heat exchanger, the second expansion device, the third expansion device, the second outdoor heat exchanger, and the second flow path switching device, and returns to the compressor; the refrigerant circuit has a fourth path as a path of the refrigerant during a second defrosting operation in which the second outdoor heat exchanger functions as a condenser and the first outdoor heat exchanger functions as an evaporator, the fourth path is a path that runs from the compressor through the second flow path switching device, the second outdoor heat exchanger, the third expansion device, the second expansion device, the first outdoor heat exchanger, and the first flow path switching device, and returns to the compressor; The control device fully closes the flow rate adjustment valve and the first throttle device during the first defrosting operation and the second defrosting operation.

2. a first branch portion and a second branch portion are provided in the first path and the second path between the compressor and the flow rate adjustment valve, the first flow path switching device is a valve having two ports provided on the first path and one port connected to the first branch portion via a refrigerant pipe, 2. The refrigeration cycle apparatus according to claim 1, wherein the second flow path switching device is a valve having two ports provided on the second path and one port connected to the second branch portion via a refrigerant pipe.

3. a first outdoor fan that supplies air to the first outdoor heat exchanger; a second outdoor fan that supplies air to the second outdoor heat exchanger; Furthermore, 3. The refrigeration cycle apparatus according to claim 1, wherein the control device operates the second outdoor fan during the first defrosting operation and operates the first outdoor fan during the second defrosting operation.

4. The refrigeration cycle apparatus according to claim 1 or 2, wherein the control device executes the first defrosting operation and the second defrosting operation when the outdoor air temperature is lower than 0°C.

5. the refrigerant circuit further includes a four-way valve that switches a flow path between the heating operation and the cooling operation, 3. The refrigeration cycle apparatus according to claim 1, wherein the flow path of the four-way valve cannot be switched between the heating operation and the first defrosting operation, and between the heating operation and the second defrosting operation.

6. a compressor mounting unit on which the compressor is mounted; one or more outdoor heat exchanger units each including the first outdoor heat exchanger and the second outdoor heat exchanger; The refrigeration cycle device according to claim 1 or 2, further comprising:

7. the control device executes the first heating defrosting operation and the second heating defrosting operation only when the outdoor air temperature is higher than a threshold temperature, The first heating defrosting operation is an operation in which the flow control valve and the first expansion device are set to an open state, a refrigerant flows through the second path and the third path, and heating is performed while defrosting the first outdoor heat exchanger, 3. The refrigeration cycle device according to claim 1, wherein the second heating defrosting operation is an operation in which the flow control valve and the first throttling device are set to an open state, refrigerant flows through the first path and the fourth path, and heating is performed while defrosting the second outdoor heat exchanger.

8. A heat source unit equipped with the compressor, the first flow path switching device, the second flow path switching device, the second throttling device, the third throttling device, the first outdoor heat exchanger, and the second outdoor heat exchanger; a heat load unit equipped with the indoor heat exchanger and the first expansion device; Furthermore, The refrigeration cycle apparatus according to claim 1 or 2, wherein the flow rate adjustment valve is mounted on the heat source unit.