JP7042906B2 - Air conditioner - Google Patents

Description

The present invention relates to an air conditioner that simultaneously defrosts an outdoor heat exchanger and heats the room.

Conventionally, there is an air conditioner that simultaneously defrosts an outdoor heat exchanger and heats the room (see, for example, Patent Document 1). Patent Document 1 has a refrigerant circuit in which a compressor, a four-way valve, an indoor heat exchanger, a decompression device, and an outdoor heat exchanger are connected by a refrigerant pipe, and hot gas is flowed from the discharge side of the compressor to the outdoor heat exchanger. A bypass circuit is provided. The outdoor heat exchanger is divided into two upper and lower refrigerant circuits to form a lower heat exchanger and an upper heat exchanger.

Then, the control device opens and closes the main circuit opening / closing mechanism and the second throttle device, heats the upper heat exchanger with the lower heat exchanger while defrosting, and then defrosts the lower heat exchanger to heat the upper side. Performs heating defrost operation, which heats with a exchanger. By performing the heating defrost operation in this way, it is possible to suppress a decrease in the temperature inside the room while suppressing a decrease in the heating capacity of the indoor unit. Therefore, it is possible to prevent the indoor comfort from being lost while defrosting.

Japanese Unexamined Patent Publication No. 2008-64381

According to Patent Document 1, when the upper heat exchanger is defrosted during the heating defrost operation, the melted drain water flows down on the heat transfer fin of the outdoor heat exchanger, but flows on the heat transfer fin by the air flow of the outdoor fan. The drain water that flows down is drawn to the leeward side of the outdoor heat exchanger. Then, as the frost in the upper heat exchanger melts, the amount of drain water on the leeward side of the heat transfer fins of the outdoor heat exchanger becomes larger than the amount of drain water on the leeward side, and the flow capacity of the drain water on the leeward side is saturated. Then, a certain amount of drain water is held on the leeward side of the outdoor heat exchanger. In this case, when the upper heat exchanger functions as an evaporator after that, the retained drain water refreezes and obstructs the air flow of the heat transfer fins of the outdoor heat exchanger, resulting in a decrease in heating capacity. There was a problem.

The present invention has been made to solve the above problems. After defrosting the upper heat exchanger, when the upper heat exchanger functions as an evaporator, the drain water held at the time of defrosting refreezes. It is an object of the present invention to provide an air conditioner capable of suppressing a decrease in heating capacity.

The air conditioner according to the present invention is condensed by a compressor that compresses and discharges a refrigerant, an indoor heat exchanger that exchanges heat between the refrigerant discharged from the compressor and indoor air, and the indoor heat exchanger. It is composed of a first drawing device that decompresses the decompressed refrigerant, and an upper heat exchanger and a lower heat exchanger whose flow paths are independent of each other, and exchanges heat between the refrigerant that has passed through the first drawing device and the outside air. An outdoor heat exchanger and a flow path switching device that selectively switches the flow path to the upper heat exchanger side or the lower heat exchanger side are sequentially connected by pipes, and a refrigerant circuit in which the refrigerant circulates and the outdoor An outdoor fan that supplies air to the heat exchanger, a hot gas bypass pipe that connects the discharge side of the compressor and the flow path switching device, a second throttle device provided in the hot gas bypass pipe, and heating. A control device for performing a heating defrost operation in which the upper heat exchanger and the lower heat exchanger are alternately defrosted while performing a normal operation is provided, and the control device comprises the upper heat exchanger during the heating defrost operation. When defrosting, the rotation speed of the outdoor fan is controlled to the minimum rotation speed that can be taken during normal heating operation, and when defrosting the lower heat exchanger, the rotation speed of the outdoor fan is set to the minimum speed. The rotation speed is controlled to be higher than the rotation speed, and after the defrosting of the lower heat exchanger, the defrosting of the upper heat exchanger is performed, and the defrosting of the lower heat exchanger is performed again . ..

According to the air conditioner according to the present invention, when the upper heat exchanger is defrosted during the heating defrost operation, the rotation speed of the outdoor fan is controlled to the minimum rotation speed that can be taken during the normal heating operation, and the lower side is controlled. When defrosting the heat exchanger, the rotation speed of the outdoor fan is controlled to be higher than the minimum rotation speed. By doing so, it was possible to suppress the amount of drain water held on the leeward side of the upper heat exchanger during defrosting of the upper heat exchanger, and after defrosting the upper heat exchanger, the upper heat exchanger functioned as an evaporator. At that time, it is possible to secure the heating capacity while suppressing the drain water held on the leeward side of the upper heat exchanger from refreezing and reducing the heating capacity.

It is a refrigerant circuit diagram of the air conditioner which concerns on embodiment of this invention. It is a refrigerant circuit diagram of the modification of the air conditioner which concerns on embodiment of this invention. It is a schematic diagram which shows the cross section of the outdoor heat exchanger of the air conditioner which concerns on embodiment of this invention, and the outdoor fan. It is the first figure which shows the control flow of the outdoor fan at the time of the heating operation of the air conditioner which concerns on embodiment of this invention. It is a 2nd figure which shows the control flow of the outdoor fan at the time of the heating operation of the air conditioner which concerns on embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below. Further, in the drawings below, the relationship between the sizes of the constituent members may differ from the actual one.

Embodiment.
FIG. 1 is a refrigerant circuit diagram of an air conditioner 100 according to an embodiment of the present invention.
The air conditioner 100 according to the present embodiment includes an outdoor unit 1 and an indoor unit 2, and the outdoor unit 1 and the indoor unit 2 are separately connected by refrigerant pipes 83 and 84 and electrical wiring (not shown). It is a shape.

[Outdoor unit]
The outdoor unit 1 includes a compressor 10, a first flow path switching device 20, a first throttle device 30, a second throttle device 60, a second flow path switching device 70, an outdoor heat exchanger 50, and an outdoor fan. It includes 500, an outside air temperature detecting device 200 for detecting the outside air temperature, and a control device 300.

[Indoor unit]
The indoor unit 2 includes an indoor heat exchanger 40 and an indoor fan 400.

In the air conditioner 100, the compressor 10, the first flow path switching device 20, the indoor heat exchanger 40, the first throttle device 30, the outdoor heat exchanger 50, and the second flow path switching device 70 are refrigerant pipes 81 to 85. , 86A to 87A and 86B to 87B, 89, 91 are sequentially connected to have a refrigerant circuit in which the refrigerant circulates. Various refrigerants can be used to circulate in this refrigerant circuit, such as R32 and R410A.

Further, the discharge side of the compressor 10 and the A port of the second flow path switching device 70 are connected by hot gas bypass pipes 80 and 88, and the hot gas bypass pipes 80 and 88 are provided with a second throttle device 60. Has been done.

[Refrigerant piping, hot gas bypass piping]
The refrigerant pipe 81 is connected to the discharge side of the compressor 10, and branches into the hot gas bypass pipe 80 and the refrigerant pipe 82 on the way. The refrigerant pipe 82 is connected to the G port of the first flow path switching device 20, and the hot gas bypass pipe 80 is connected to the second throttle device 60. The refrigerant pipe 83 connects the H port of the first flow path switching device 20 and the indoor heat exchanger 40. The refrigerant pipe 84 connects the indoor heat exchanger 40 and the first throttle device 30. The refrigerant pipe 85 is connected to the first throttle device 30, branches to the refrigerant pipe 86A and the refrigerant pipe 86B on the way, the refrigerant pipe 86A is connected to the upper heat exchanger 50A of the outdoor heat exchanger 50, and the refrigerant pipe 86B is connected to the upper heat exchanger 50A. It is connected to the lower heat exchanger 50B of the outdoor heat exchanger 50. The refrigerant pipe 87A connects the upper heat exchanger 50A and the B2 port of the second flow path switching device 70, and the refrigerant pipe 87B connects the lower heat exchanger 50B and the B1 port of the second flow path switching device 70. .. The hot gas bypass pipe 88 connects the second throttle device 60 and the A port of the second flow path switching device 70. The refrigerant pipe 89 connects the C port of the second flow path switching device 70 and the E port of the first flow path switching device 20. The refrigerant pipe 91 connects the F port of the first flow path switching device 20 to the suction side of the compressor 10.

[Control device 300]
The control device 300 is composed of, for example, dedicated hardware or a CPU (also referred to as a central processing unit, a processing unit, a computing device, a microprocessor, a microcomputer, or a processor) that executes a program stored in a memory. Has been done.

There are two types of operating operations of the air conditioner 100 according to the present embodiment: cooling operation and heating operation. Further, in the heating operation, one of the upper heat exchanger 50A and the lower heat exchanger 50B is an evaporator in the heating normal operation in which both the upper heat exchanger 50A and the lower heat exchanger 50B function as evaporators. There are two types: heating defrost operation, in which the other functions as a condenser. Then, the control device 300 performs one of these operation operations according to the selection by the user or the like.

The compressor 10 is configured so that the operating frequency can be changed by a control signal received from the control device 300. The output of the compressor 10 can be adjusted by changing the operating frequency of the compressor 10. Various types of the compressor 10 can be adopted, for example, a rotary type, a reciprocating type, a scroll type, a screw type and the like.

The first flow path switching device 20 is a device for switching between cooling operation and heating operation, for example, a four-way valve, but a two-way valve and a three-way valve may be combined and configured. In the heating operation, as shown by the solid line in FIG. 1, the refrigerant pipe 82, which is the discharge pipe of the compressor 10, and the refrigerant pipe 83 are connected, and the refrigerant pipe 89 and the refrigerant pipe 91, which is the compressor suction pipe, are connected. do. Further, in the cooling operation, as shown by the broken line in FIG. 1, the refrigerant pipe 82 and the refrigerant pipe 89 are connected, and the refrigerant pipe 83 and the refrigerant pipe 91 are connected.

The first throttle device 30 is a device for reducing the pressure of the refrigerant flowing into the first throttle device 30, for example, an expansion valve.

The indoor fan 400 is attached to the indoor heat exchanger 40 and supplies air to the indoor heat exchanger 40.

The outdoor fan 500 is attached to the outdoor heat exchanger 50 and supplies air to the outdoor heat exchanger 50.

The outdoor heat exchanger 50 is a fin tube type heat exchanger having a plurality of heat transfer pipes and a plurality of heat transfer fins. The outdoor heat exchanger 50 is composed of, for example, an upper heat exchanger 50A and a lower heat exchanger 50B divided into upper and lower parts as shown in FIG. 3, and the upper heat exchanger 50A and the lower heat exchanger 50B are vertically divided. They are placed in parallel and connected in parallel with each other. Further, the heat transfer fins of the upper heat exchanger 50A and the lower heat exchanger 50B are divided. The flow direction of the refrigerant will be described in the explanation of the operating operation.

The hot gas bypass pipes 80 and 88 are provided to use a part of the refrigerant discharged from the compressor 10 for defrosting the upper heat exchanger 50A and the lower heat exchanger 50B. As a throttle mechanism, for example, a second throttle device 60, which is an expansion valve, is connected to the hot gas bypass pipe 80, and after depressurizing a part of the discharged refrigerant of the compressor 10 to a medium pressure, the second flow path is switched. The refrigerant is guided to the defrost target among the upper heat exchanger 50A and the lower heat exchanger 50B via the device 70.

Next, the operating operation of the air conditioner 100 according to the present embodiment will be described.

[Cooling operation]
First, the cooling operation will be described. The compressor 10 sucks the refrigerant from the refrigerant pipe 91 and compresses it. The compressed high-temperature and high-pressure gas refrigerant is discharged from the compressor 10 and flows to the refrigerant pipe 89 via the refrigerant pipe 81, the refrigerant pipe 82, and the first flow path switching device 20.

The gas refrigerant flowing through the refrigerant pipe 89 is branched by the second flow path switching device 70 as shown by the solid line in FIG. 1, one flows from the port B2 to the refrigerant pipe 87A, and the other flows from the port B1 to the refrigerant pipe 87B. The gas refrigerant branched to the refrigerant pipe 87A flows to the upper heat exchanger 50A, exchanges heat with the outdoor air in the upper heat exchanger 50A, condenses and flows to the refrigerant pipe 86A as a high-pressure liquid refrigerant. Further, the gas refrigerant branched to the refrigerant pipe 87B flows to the lower heat exchanger 50B, exchanges heat with the outdoor air in the lower heat exchanger 50B, condenses and flows to the refrigerant pipe 86B as a high-pressure liquid refrigerant. Here, the control device 300 can adjust the rotation speed of the outdoor fan 500 by the control signal. At this time, by adjusting the rotation speed of the outdoor fan 500 by the control device 300, the amount of air transported to the outdoor heat exchanger 50 changes, and the amount of heat exchanged between the refrigerant and the air in the outdoor heat exchanger 50 is adjusted. be able to.

The liquid refrigerant flowing through the refrigerant pipe 86A and the liquid refrigerant flowing through the refrigerant pipe 86B merge at the confluence of the refrigerant pipes 86A and 86B and the refrigerant pipe 85, flow into the refrigerant pipe 85, and are depressurized by the first drawing device 30. , It becomes a low temperature and low pressure two-phase refrigerant and flows to the refrigerant pipe 84. Here, the control device 300 can adjust the opening degree of the first throttle device 30 by the control signal. At this time, the decompression amount of the refrigerant can be adjusted by adjusting the opening degree of the first throttle device 30 by the control device 300. When the opening degree of the first drawing device 30 is changed in the opening direction, the refrigerant pressure on the outlet side of the first drawing device 30 increases, and the dryness of the refrigerant decreases. On the other hand, when the opening degree of the first drawing device 30 is changed in the closing direction, the refrigerant pressure on the outlet side of the first drawing device 30 decreases, and the dryness of the refrigerant increases.

The liquid refrigerant flowing through the refrigerant pipe 84 flows into the indoor heat exchanger 40, exchanges heat with the indoor air in the indoor heat exchanger 40, evaporates and becomes a low-temperature low-pressure gas refrigerant, and flows to the refrigerant pipe 83. Here, the control device 300 can adjust the rotation speed of the indoor fan 400 by the control signal. At this time, by adjusting the rotation speed of the indoor fan 400 by the control device 300, the amount of air transported to the indoor heat exchanger 40 changes, and the amount of heat exchanged between the refrigerant and the air in the indoor heat exchanger 40 is adjusted. be able to.

The gas refrigerant flowing through the refrigerant pipe 83 flows from the refrigerant pipe 91 to the compressor 10 again via the first flow path switching device 20.

[Heating normal operation]
Next, the heating normal operation will be described. The compressor 10 sucks the refrigerant from the refrigerant pipe 91 and compresses it. The compressed high-temperature and high-pressure gas refrigerant is discharged from the compressor 10 and flows to the refrigerant pipe 83 via the refrigerant pipe 81, the refrigerant pipe 82, and the first flow path switching device 20.

The gas refrigerant flowing into the indoor heat exchanger 40 from the refrigerant pipe 83 exchanges heat with the indoor air in the indoor heat exchanger 40, condenses and becomes a high-pressure liquid refrigerant, and flows to the refrigerant pipe 84. At this time, by adjusting the rotation speed of the indoor fan 400 by the control device 300, the amount of air transported to the indoor heat exchanger 40 changes, and the amount of heat exchanged between the refrigerant and the air in the indoor heat exchanger 40 is adjusted. Can be done.

The liquid refrigerant flowing out of the indoor heat exchanger 40 passes through the refrigerant pipe 84, is depressurized by the first throttle device 30, becomes a low-temperature low-pressure two-phase refrigerant, and flows to the refrigerant pipe 85. At this time, the decompression amount of the refrigerant can be adjusted by adjusting the opening degree of the first throttle device 30 by the control device 300. When the opening degree of the first drawing device 30 is changed in the opening direction, the refrigerant pressure on the outlet side of the first drawing device 30 increases, and the dryness of the refrigerant decreases. On the other hand, when the opening degree of the first drawing device 30 is changed in the closing direction, the refrigerant pressure on the outlet side of the first drawing device 30 decreases, and the dryness of the refrigerant increases.

The two-phase refrigerant flowing through the refrigerant pipe 85 branches into the refrigerant pipe 86A and the refrigerant pipe 86B. The two-phase refrigerant branched to the refrigerant pipe 86A flows to the upper heat exchanger 50A, exchanges heat with the outdoor air in the upper heat exchanger 50A, evaporates and becomes a low-temperature low-pressure gas refrigerant, and flows to the refrigerant pipe 87A. Further, the two-phase refrigerant branched to the refrigerant pipe 86B flows to the lower heat exchanger 50B, exchanges heat with the outdoor air in the lower heat exchanger 50B, evaporates and becomes a low-temperature low-pressure gas refrigerant in the refrigerant pipe 87B. It flows. At this time, by adjusting the rotation speed of the outdoor fan 500 by the control device 300, the amount of air transported to the outdoor heat exchanger 50 changes, and the amount of heat exchanged between the refrigerant and the air in the outdoor heat exchanger 50 is adjusted. Can be done.

The gas refrigerant flowing through the refrigerant pipe 87A and the gas refrigerant flowing through the refrigerant pipe 87B are merged by the second flow path switching device 70 as shown by the solid line in FIG. 1, and flow from the C port to the refrigerant pipe 89. The gas refrigerant flowing through the refrigerant pipe 89 flows from the refrigerant pipe 91 to the compressor 10 again.

While the normal heating operation is being performed, the opening degree of the second throttle device 60 may be open or fully closed. Since the second flow path switching device 70 communicates the port B1 and the port C and communicates the port B2 and the port C, even if the refrigerant is present in the hot gas bypass pipe 88, the other is from the port A. Refrigerant does not flow out to the port.

During the normal heating operation as described above, the outdoor heat exchanger 50 may be frosted and need to be defrosted. In that case, it is conceivable to temporarily stop the normal heating operation, switch to the cooling operation, and perform the defrost operation in which the high-temperature and high-pressure gas refrigerant compressed by the compressor 10 flows to the outdoor heat exchanger 50. In this case, the normal heating operation is interrupted, and the comfort of the room is lost.

[Heating defrost operation]
Next, the heating defrost operation will be described.
In the heating defrost operation, the second flow path switching device 70 is operated to alternately defrost the upper heat exchanger 50A and the lower heat exchanger 50B while continuing the normal heating operation.

When the outdoor heat exchanger 50 is frosted during the normal heating operation, for example, when it becomes necessary to defrost the upper heat exchanger 50A, the hot gas bypass pipe 88 and the refrigerant pipe 87A are connected to each other. The second flow path switching device 70 is operated so that the refrigerant pipe 87B and the refrigerant pipe 89 are connected. As a result, a part of the high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows into the hot gas bypass pipe 80, and the remaining gas refrigerant passes through the refrigerant pipe 82, the first flow path switching device 20, and the refrigerant pipe 83. And flows to the indoor heat exchanger 40.

The refrigerant flowing into the hot gas bypass pipe 80 is decompressed by the second throttle device 60, and passes through the hot gas bypass pipe 88, the second flow path switching device 70, and the refrigerant pipe 87A to the upper heat exchanger 50A to be defrosted. It flows in. The refrigerant that has flowed into the upper heat exchanger 50A condenses while exchanging heat with frost, and defrosts the upper heat exchanger 50A.

At this time, by changing the opening degree of the second throttle device 60 by the control device 300, the amount of the refrigerant flowing into the upper heat exchanger 50A, which is the target of defrosting, is adjusted, and the amount of heat exchanged between the refrigerant and the frost is adjusted. Can be done.

When the opening degree of the second throttle device 60 is changed in the opening direction, the amount of refrigerant at the outlet of the second throttle device 60 increases, the amount of refrigerant flowing through the upper heat exchanger 50A increases, and the amount of heat exchanged between the refrigerant and frost increases. Will increase. At this time, the amount of the refrigerant flowing through the indoor heat exchanger 40 decreases, so that the heating capacity decreases.

On the other hand, when the opening degree of the second throttle device 60 is changed in the closing direction, the amount of the refrigerant at the outlet of the second throttle device 60 decreases, the amount of the refrigerant flowing through the upper heat exchanger 50A decreases, and the refrigerant and the frost The amount of heat exchange is reduced. At this time, the amount of the refrigerant flowing through the indoor heat exchanger 40 increases, so that the heating capacity increases.

The refrigerant condensed by the upper heat exchanger 50A merges with the refrigerant condensed by the indoor heat exchanger 40 and decompressed by the first throttle device 30 at the confluence of the refrigerant pipe 86A and the refrigerant pipe 85, and joins the refrigerant pipe 86B. It flows.

The refrigerant flowing in the refrigerant pipe 86B flows into the lower heat exchanger 50B and evaporates. After that, it flows from the refrigerant pipe 91 to the compressor 10 again via the refrigerant pipe 87B, the second flow path switching device 70, and the refrigerant pipe 89.

Further, when the outdoor heat exchanger 50 is frosted during the normal heating operation and it becomes necessary to defrost the lower heat exchanger 50B, for example, the hot gas bypass pipe 88 and the refrigerant pipe 87B are connected. The second flow path switching device 70 is operated so as to be connected and the refrigerant pipe 87A and the refrigerant pipe 89 are connected. As a result, a part of the high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows into the hot gas bypass pipe 80, and the remaining gas refrigerant passes through the refrigerant pipe 82, the first flow path switching device 20, and the refrigerant pipe 83. And flows to the indoor heat exchanger 40.

The refrigerant flowing into the hot gas bypass pipe 80 is decompressed by the second throttle device 60, and is a lower heat exchanger to be defrosted via the hot gas bypass pipe 88, the second flow path switching device 70, and the refrigerant pipe 87B. It flows into 50B. The refrigerant that has flowed into the lower heat exchanger 50B condenses while exchanging heat with frost, and defrosts the lower heat exchanger 50B.

The refrigerant condensed by the lower heat exchanger 50B merges with the refrigerant condensed by the indoor heat exchanger 40 and depressurized by the first throttle device 30 at the confluence of the refrigerant pipe 86B and the refrigerant pipe 85, and is merged with the refrigerant pipe 86A. Flow to.

The refrigerant flowing in the refrigerant pipe 86A flows into the upper heat exchanger 50A and evaporates. After that, it flows from the refrigerant pipe 91 to the compressor 10 again via the refrigerant pipe 87A, the second flow path switching device 70, and the refrigerant pipe 89.

FIG. 2 is a refrigerant circuit diagram of a modified example of the air conditioner 100 according to the embodiment of the present invention.
The refrigerant circuit of FIG. 1 can be substituted with the refrigerant circuit of FIG. 2, and the same effect as that of FIG. 1 can be obtained. The refrigerant circuit configuration of FIG. 2 will be described below.

The four-way valves 600 and 700 are examples of devices for switching between cooling operation, heating normal operation, and heating defrost operation. The K port of the four-way valve 600 and the Q port of the four-way valve 700 are sealed so that the refrigerant does not flow out. Further, the four-way valves 600 and 700 may be configured by combining a two-way valve and a three-way valve.

The first flow path switching device 20 is a device that switches between cooling operation and heating operation, and is, for example, a four-way valve, but may be configured by combining a two-way valve and a three-way valve. In the heating operation, as shown by the solid line in FIG. 2, the refrigerant pipe 82 and the refrigerant pipe 83, which are the discharge pipes of the compressor 10, are connected, and the refrigerant pipe 95 and the refrigerant pipe 92 are connected. In the cooling operation, as shown by the broken line in FIG. 2, the refrigerant pipe 82 and the refrigerant pipe 92 are connected, and the refrigerant pipe 83 and the refrigerant pipe 95 are connected.

The check valve 90 is an example of a device configured to allow the refrigerant to flow in only one direction. Due to the connection direction as shown in FIG. 2, the refrigerant flows out from the refrigerant pipe 92 in the direction of the refrigerant pipe 96, and the refrigerant does not flow out from the refrigerant pipe 96 in the direction of the refrigerant pipe 92.

The refrigerant pipe 87A is connected to the M port of the four-way valve 600, and the refrigerant pipe 93 is connected to the L port. Further, the refrigerant pipe 87B is connected to the S port of the four-way valve 700, and the refrigerant pipe 94 is connected to the R port. Further, the refrigerant pipes 93 and 94 merge and are connected to the refrigerant pipe 89 at the merging portion.

The hot gas bypass pipe 88 is branched into two and is connected to the J port of the four-way valve 600 and the P port of the four-way valve 700, respectively.

Next, the operation operation of the modified example of the air conditioner 100 according to the present embodiment will be described.

[Cooling operation]
First, the cooling operation will be described. In the cooling operation, the four-way valve 600 is operated so that the J port and the M port are connected and the L port and the K port are connected. Further, the four-way valve 700 is operated so that the P port and the S port are connected and the R port and the Q port are connected. Further, the second throttle device 60 is fully opened, but the second throttle device 60 is fully opened because a large pressure loss occurs when the refrigerant flows only through the check valve 90.

The high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows from the refrigerant pipe 82 to the refrigerant pipe 92 via the first flow path switching device 20, passes through the check valve 90, and bypasses the hot gas from the refrigerant pipe 96. It flows to the pipe 88. After that, the refrigerant branches and flows into the J port of the four-way valve 600 and the P port of the four-way valve 700, respectively. The gas refrigerant that has flowed into the J port of the four-way valve 600 flows through the refrigerant pipe 87A, then exchanges heat with the outdoor air in the upper heat exchanger 50A, condenses into a high-pressure liquid refrigerant, and flows to the refrigerant pipe 86A in all directions. The gas refrigerant that has flowed into the P port of the valve 700 flows through the refrigerant pipe 87B, then exchanges heat with the outdoor air in the lower heat exchanger 50B, condenses and flows into the refrigerant pipe 86B as a high-pressure liquid refrigerant.

The liquid refrigerant flowing through the refrigerant pipe 86A and the liquid refrigerant flowing through the refrigerant pipe 86B merge at the confluence of the refrigerant pipes 86A and 86B and the refrigerant pipe 85, flow into the refrigerant pipe 85, and are depressurized by the first drawing device 30. , It becomes a low temperature and low pressure two-phase refrigerant and flows to the refrigerant pipe 84. The liquid refrigerant flowing through the refrigerant pipe 84 flows into the indoor heat exchanger 40, exchanges heat with the indoor air in the indoor heat exchanger 40, evaporates and becomes a low-temperature low-pressure gas refrigerant, and flows to the refrigerant pipe 83. The gas refrigerant flowing through the refrigerant pipe 83 flows from the refrigerant pipe 91 to the compressor 10 again via the first flow path switching device 20 and the refrigerant pipe 95.

[Heating normal operation]
Next, the heating normal operation will be described. In normal heating operation, the four-way valve 600 operates so that the M port and the L port are connected and the J port and the K port are connected. Further, the four-way valve 700 is operated so that the S port and the R port are connected and the P port and the Q port are connected. Further, although the second throttle device 60 is opened, the refrigerant in the hot gas bypass pipe 88 does not flow out from the J port of the four-way valve 600 to the L port or the M port, and R from the P port of the four-way valve 700. It does not flow out to the port or S port.

The high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows to the refrigerant pipe 83 via the refrigerant pipe 81, the refrigerant pipe 82, and the first flow path switching device 20. The gas refrigerant flowing into the indoor heat exchanger 40 from the refrigerant pipe 83 exchanges heat with the indoor air in the indoor heat exchanger 40, condenses and becomes a high-pressure liquid refrigerant, and flows to the refrigerant pipe 84.

The liquid refrigerant flowing out of the indoor heat exchanger 40 passes through the refrigerant pipe 84, is depressurized by the first throttle device 30, becomes a low-temperature low-pressure two-phase refrigerant, and flows to the refrigerant pipe 85. The two-phase refrigerant flowing through the refrigerant pipe 85 branches into the refrigerant pipe 86A and the refrigerant pipe 86B. The two-phase refrigerant branched to the refrigerant pipe 86A flows to the upper heat exchanger 50A, exchanges heat with the outdoor air in the upper heat exchanger 50A, and evaporates to become a low-temperature low-pressure gas refrigerant. Further, the two-phase refrigerant branched to the refrigerant pipe 86B flows to the lower heat exchanger 50B, exchanges heat with the outdoor air in the lower heat exchanger 50B, and evaporates to become a low-temperature low-pressure gas refrigerant.

The refrigerant discharged from the upper heat exchanger 50A flows from the refrigerant pipe 87A through the four-way valve 600 and flows to the refrigerant pipe 93. Further, the refrigerant discharged from the lower heat exchanger 50B flows from the refrigerant pipe 87B through the four-way valve 700 and flows to the refrigerant pipe 94. The refrigerant flowing through the refrigerant pipe 93 and the refrigerant flowing through the refrigerant pipe 94 merge at the confluence of the refrigerant pipes 93 and 94 and the refrigerant pipe 89, flow into the refrigerant pipe 89, and flow from the refrigerant pipe 91 to the compressor 10 again.

[Heating defrost operation]
Next, the heating defrost operation will be described.

If the outdoor heat exchanger 50 is frosted during normal heating operation and it becomes necessary to defrost the upper heat exchanger 50A, for example, the J port and the M port are connected, and the K port and the L port are connected. The four-way valve 600 is operated so that it is connected to the port.

A part of the high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows into the hot gas bypass pipe 80, and the remaining gas refrigerant passes through the refrigerant pipe 82, the first flow path switching device 20, and the refrigerant pipe 83 to heat the room. It flows to the exchanger 40.

The refrigerant flowing into the hot gas bypass pipe 80 is depressurized by the second throttle device 60, and flows into the upper heat exchanger 50A to be defrosted via the hot gas bypass pipe 88, the four-way valve 600, and the refrigerant pipe 87A. The refrigerant that has flowed into the upper heat exchanger 50A condenses while exchanging heat with frost, and defrosts the upper heat exchanger 50A.

At this time, by changing the opening degree of the second throttle device 60 by the control device 300, the amount of the refrigerant flowing into the upper heat exchanger 50A, which is the target of defrosting, is adjusted, and the amount of heat exchanged between the refrigerant and the frost is adjusted. Can be done.

When the opening degree of the second throttle device 60 is changed in the opening direction, the amount of refrigerant at the outlet of the second throttle device 60 increases, the amount of refrigerant flowing through the upper heat exchanger 50A increases, and the amount of heat exchanged between the refrigerant and frost increases. Will increase. At this time, the amount of the refrigerant flowing through the indoor heat exchanger 40 decreases, so that the heating capacity decreases.

On the other hand, when the opening degree of the second throttle device 60 is changed in the closing direction, the amount of the refrigerant at the outlet of the second throttle device 60 decreases, the amount of the refrigerant flowing through the upper heat exchanger 50A decreases, and the refrigerant and the frost The amount of heat exchange is reduced. At this time, the amount of the refrigerant flowing through the indoor heat exchanger 40 increases, so that the heating capacity increases.

The refrigerant condensed by the upper heat exchanger 50A merges with the refrigerant condensed by the indoor heat exchanger 40 and decompressed by the first throttle device 30 at the confluence of the refrigerant pipe 86A and the refrigerant pipe 85, and joins the refrigerant pipe 86B. It flows.

The refrigerant flowing in the refrigerant pipe 86B flows into the lower heat exchanger 50B and evaporates. After that, it flows from the refrigerant pipe 91 to the compressor 10 again via the refrigerant pipe 87B, the four-way valve 700, and the refrigerant pipes 94 and 89.

Further, when the outdoor heat exchanger 50 is frosted during the normal heating operation and it becomes necessary to defrost the lower heat exchanger 50B, for example, the P port and the S port are connected, and Q. The four-way valve 700 is operated so that the port and the R port are connected. As a result, a part of the high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows into the hot gas bypass pipe 80, and the remaining gas refrigerant passes through the refrigerant pipe 82, the first flow path switching device 20, and the refrigerant pipe 83. And flows to the indoor heat exchanger 40.

The refrigerant flowing into the hot gas bypass pipe 80 is depressurized by the second throttle device 60, and flows into the lower heat exchanger 50B to be defrosted via the hot gas bypass pipe 88, the four-way valve 700, and the refrigerant pipe 87B. The refrigerant that has flowed into the lower heat exchanger 50B condenses while exchanging heat with frost, and defrosts the lower heat exchanger 50B.

The refrigerant condensed by the lower heat exchanger 50B merges with the refrigerant condensed by the indoor heat exchanger 40 and depressurized by the first throttle device 30 at the confluence of the refrigerant pipe 86B and the refrigerant pipe 85, and is merged with the refrigerant pipe 86A. Flow to.

The refrigerant flowing in the refrigerant pipe 86A flows into the upper heat exchanger 50A and evaporates. After that, it flows from the refrigerant pipe 91 to the compressor 10 again via the refrigerant pipe 87A, the four-way valve 600, and the refrigerant pipes 93 and 89.

The order of defrosting the upper heat exchanger 50A and the lower heat exchanger 50B connected in parallel with each other is such that after defrosting the lower heat exchanger 50B, defrosting the upper heat exchanger 50A is performed, and then the lower side is again defrosted. It is desirable to defrost the heat exchanger 50B. The reason will be explained below.

For example, consider a case where the lower heat exchanger 50B is defrosted after the upper heat exchanger 50A is defrosted. During the defrosting of the upper heat exchanger 50A, the frost adhering to the heat transfer fins melts into water droplets, which flow down on the heat transfer fin surface of the upper heat exchanger 50A. Hereinafter, water droplets or water streams in which frost has melted are referred to as drain water. A part of the drain water flowing from the upper heat exchanger 50A to the lower heat exchanger 50B is re-frozen in the lower heat exchanger 50B functioning as an evaporator.

After that, when defrosting the lower heat exchanger 50B, the frost generated on the heat transfer fins of the lower heat exchanger 50B during the normal heating operation and the drain water flowing down from the upper heat exchanger 50A and refreezing. And must be defrosted, which increases the time required to complete the defrost. At this time, since the upper heat exchanger 50A functions as an evaporator, the amount of frost attached to the upper heat exchanger 50A increases. Then, at the time of the next defrosting of the upper heat exchanger 50A, the time required to complete the defrosting becomes long.

Therefore, the lower heat exchanger 50B is first defrosted to defrost the frost generated during the normal heating operation, and then the upper heat exchanger 50A is defrosted to defrost the frost generated during the normal heating operation. Finally, the lower heat exchanger 50B is defrosted again in order to defrost a part of the drain water that has flowed down from the upper heat exchanger 50A and has been re-frozen. As a result, the defrost time can be shortened.

Next, a problem in heating defrost operation in a refrigerant circuit having an outdoor heat exchanger 50 composed of an upper heat exchanger 50A and a lower heat exchanger 50B divided into upper and lower parts will be described.

FIG. 3 is a schematic view showing a cross section of the outdoor heat exchanger 50 of the air conditioner 100 according to the embodiment of the present invention and the outdoor fan 500. The number of stages of the outdoor heat exchanger 50 in FIG. 3, the number of stages of division, the number of rows, the path set, and the like are merely examples, and are not limited to the configuration of the outdoor heat exchanger 50 shown in FIG.

When the upper heat exchanger 50A arranged on the upper side of the lower heat exchanger 50B is defrosted, the frost adhering to the heat transfer fins melts and flows down on the heat transfer fin surface of the upper heat exchanger 50A. .. A part of the drain water that has reached the lower end of the heat transfer fin of the upper heat exchanger 50A falls on the heat transfer fin surface of the lower heat exchanger 50B. Further, a part of the drain water flowing down on the heat transfer fin of the upper heat exchanger 50A is attracted to the leeward side of the heat transfer fin by the air blown by the outdoor fan 500.

As the defrosting of the upper heat exchanger 50A progresses, the amount of drain water on the leeward side at the lower end of the heat transfer fin of the upper heat exchanger 50A becomes larger than the amount of drain water on the windward side of the heat transfer fin surface. Then, the leeward capacity (the leeward drainage path 900 in FIG. 3) is saturated, and a certain amount of drain water is held on the leeward side of the lower end of the heat transfer fin of the upper heat exchanger 50A. ..

After that, when the defrosting of the upper heat exchanger 50A is completed and the upper heat exchanger 50A functions as an evaporator, the drain water held on the leeward side of the lower end of the heat transfer fin of the upper heat exchanger 50A refreezes. .. Then, the re-frozen drain water obstructs the air flow by the outdoor fan 500 and the amount of exchanged heat decreases, which causes a decrease in the heating capacity. Further, the evaporation temperature of the refrigerant flowing in the evaporator is lowered, and the amount of frost on the heat transfer fins of the evaporator is increased. When the upper heat exchanger 50A is defrosted again due to the increase in the amount of frost formation, problems such as a decrease in heating capacity and a long defrost completion time (hereinafter referred to as the first problem) occur.

The above first problem can be prevented by increasing the rotation speed of the outdoor fan 500 and blowing off the drain water held on the leeward side of the lower end of the heat transfer fin of the upper heat exchanger 50A. However, when this is done, drain water adheres to the outdoor fan 500 held on the leeward side of the upper heat exchanger 50A during defrosting of the upper heat exchanger 50A and refreezes, and the amount of freezing increases, so that the outdoor fan 500 A second problem, which is different from the first problem described above, arises, which causes damage. Therefore, it is not preferable to increase the rotation speed of the outdoor fan 500 to blow off the drain water held on the leeward side of the lower end of the heat transfer fin of the upper heat exchanger 50A.

Next, regarding means for solving the above-mentioned first problem by controlling the rotation speed of the outdoor fan 500 for each of the case of defrosting the upper heat exchanger 50A and the case of defrosting the lower heat exchanger 50B. explain.

Let t = t1 be the time when the control device 300, which is performing the normal heating operation, starts the heating defrost operation and starts the defrost of the lower heat exchanger 50B. Further, the time for terminating the defrosting of the lower heat exchanger 50B and starting the defrosting of the upper heat exchanger 50A is set to t = t2. Further, the time for terminating the defrosting of the upper heat exchanger 50A and starting the defrosting of the lower heat exchanger 50B is set to t = t3. Further, the time for ending the defrosting of the lower heat exchanger 50B and ending the heating defrosting operation is set to t = t4.

Further, the rotation speed of the outdoor fan 500 during normal heating operation is Ra, the rotation speed of the outdoor fan 500 of t = t1 to t2 is Rb, the rotation speed of the outdoor fan 500 of t = t2 to t3 is Rc, and t = t3. Let Rd be the rotation speed of the outdoor fan 500 of t4.

FIG. 4 is a first diagram showing a control flow of the outdoor fan 500 during the heating operation of the air conditioner 100 according to the embodiment of the present invention. FIG. 5 is a second diagram showing a control flow of the outdoor fan 500 during the heating operation of the air conditioner 100 according to the embodiment of the present invention.
Hereinafter, the control flow of the outdoor fan 500 during the heating operation of the air conditioner 100 according to the present embodiment will be described with reference to FIGS. 4 and 5.

After the start of the heating operation, first, after the start of the normal heating operation, the control device 300 determines whether or not the time t1 has elapsed (step S1). In step S1, when it is determined that the time t1 has elapsed (Yes in step S1), the control device 300 starts the heating defrost operation and starts the defrost of the lower heat exchanger 50B (step S2).

After step S2, the control device 300 changes the rotation speed of the outdoor fan 500 from the rotation speed Ra during normal heating operation to Rb based on the outside air temperature detected by the outside air temperature detection device 200 (steps S3 and S4). ).

After step S4, the control device 300 determines whether or not the time t2 has elapsed (step S5). In step S5, when it is determined that the time t2 has elapsed (Yes in step S5), the control device 300 ends the defrosting of the lower heat exchanger 50B and starts the defrosting of the upper heat exchanger 50A (step S6). ). Then, the control device 300 changes the rotation speed of the outdoor fan 500 from Rb to Rc (step S7).

After step S7, the control device 300 determines whether or not the time t3 has elapsed (step S8). In step S8, when it is determined that the time t3 has elapsed (Yes in step S8), the control device 300 ends the defrosting of the upper heat exchanger 50A and starts the defrosting of the lower heat exchanger 50B (step S9). ).

After step S9, the control device 300 changes the rotation speed of the outdoor fan 500 from Rc to Rd based on the outside air temperature detected by the outside air temperature detecting device 200 (steps S10 and S11).

After step S11, the control device 300 determines whether or not the time t4 has elapsed (step S12). In step S12, when it is determined that the time t4 has elapsed (Yes in step S12), the control device 300 ends the defrosting of the lower heat exchanger 50B and ends the heating defrosting operation (step S13), and the heating is normal. Return to operation.

Next, when the lower heat exchanger 50B is defrosted, the rotation speed of the outdoor fan 500 when the outside air temperature detected by the outside air temperature detecting device 200 is higher than or lower than the preset temperature explain. In this embodiment, the freezing temperature is assumed as a preset temperature, and is set to, for example, 0 ° C.

First, a case where the outside air temperature detected by the outside air temperature detecting device 200 is larger than 0 ° C. will be described.
When defrosting the lower heat exchanger 50B, the rotation speed of the outdoor fan 500 is set to Ra0 or more during the normal heating operation immediately before the start of the heating defrost operation. However, if the rotation speed Ra0 of the outdoor fan 500 during the normal heating operation immediately before the start of the heating defrost operation is the maximum rotation speed Rmax that can be taken during the normal heating operation, the rotation speed of the outdoor fan 500 is set to the maximum rotation speed Rmax. And. By doing so, in the upper heat exchanger 50A, heat can be efficiently collected from the outside air, and the heating capacity can be improved. Further, in the lower heat exchanger 50B, which is a condenser, defrosting can be efficiently promoted by applying a large amount of outside air having a temperature higher than 0 ° C. to frost and using the heat energy of the outside air for defrosting.

When defrosting the upper heat exchanger 50A, the drain water on the heat transfer fin surface of the upper heat exchanger 50A is attracted to the leeward side by the air flow from the outdoor fan 500, and the leeward side of the lower end portion on the heat transfer fin surface. It is preferable to set the rotation speed R so as not to refreeze when the upper heat exchanger 50A becomes an evaporator. The rotation speed R of the outdoor fan 500 is set to a value smaller than the rotation speed Ra0 during the normal heating operation immediately before the start of the heating defrost operation.

Further, since the degree of the force that the drain water is attracted to the leeward side differs depending on the heat transfer fin material of the outdoor heat exchanger 50 and the fin spacing, the rotation speed R of the outdoor fan 500 is experimental for each heat exchanger. It is desirable to decide on. The larger the rotation speed R of the experimentally determined outdoor fan 500 is larger than the minimum rotation speed Rmin that can be taken during the normal heating operation, the more efficiently the evaporator can collect heat from the outside air. Therefore, it is possible to secure the heating capacity while suppressing the drain water held at the lower end of the heat transfer fin of the upper heat exchanger 50A from refreezing and reducing the heating capacity.

However, even if the rotation speed R of the outdoor fan 500 is experimentally determined, it is difficult to verify that the rotation speed is suitable for any cold region, and the rotation speed is not necessarily a versatile rotation speed. ..

Therefore, it is possible to allow a slight decrease in the heating capacity and set the rotation speed R of the outdoor fan 500 to the minimum rotation speed Rmin that can be taken during the normal heating operation. By doing so, the amount of drain water held on the leeward side of the upper heat exchanger 50A can be suppressed, and the above-mentioned first problem can be avoided. Furthermore, the second problem described above does not occur.

Next, a case where the outside air temperature detected by the outside air temperature detecting device 200 is 0 ° C. or less will be described.
When defrosting the lower heat exchanger 50B, the rotation speed of the outdoor fan 500 is less than the rotation speed Ra0 during the normal heating operation immediately before the start of the heating defrost operation, and is larger than the rotation speed R, that is, heating. It should be larger than the minimum rotation speed Rmin that can be taken during normal operation. By doing so, the upper heat exchanger 50A, which is an evaporator, can efficiently collect heat from the outside air and suppress a decrease in heating capacity. Further, in the lower heat exchanger 50B, which is a condenser, the amount of heat taken away from the refrigerant flowing inside is reduced by reducing the outside air of 0 ° C. or lower supplied to the outdoor heat exchanger 50, and the defrosting efficiency is improved. You can proceed well.

When defrosting the upper heat exchanger 50A, the rotation speed of the upper heat exchanger 50A is set to the same rotation speed as when the outside air temperature is higher than 0 ° C. , that is, the minimum rotation speed Rmin that can be taken during the normal heating operation. By doing so, the amount of drain water held on the leeward side of the outdoor heat exchanger 50 can be suppressed, and the above-mentioned first problem can be avoided.

As described above, the air conditioner 100 according to the present embodiment includes a compressor 10 that compresses and discharges the refrigerant, an indoor heat exchanger 40 that exchanges heat between the refrigerant discharged from the compressor 10 and the indoor air, and the indoor heat exchanger 40. The first drawing device 30 is composed of a first drawing device 30 for reducing the pressure of the refrigerant condensed by the heat exchanger 40, and an upper heat exchanger 50A and a lower heat exchanger 50B having independent flow paths. The outdoor heat exchanger 50 that exchanges heat between the passed refrigerant and the outside air, and the second flow path switching device 70 that selectively switches the flow path to the upper heat exchanger 50A side or the lower heat exchanger side 50B, sequentially. A hot gas bypass pipe 80 that connects a refrigerant circuit that is connected by pipes and circulates refrigerant, an outdoor fan 500 that supplies air to the outdoor heat exchanger 50, and a discharge side of the compressor 10 and a second flow path switching device 70. , 88, the second throttle device 60 provided in the hot gas bypass pipes 80 and 88, and the heating defrost operation in which the upper heat exchanger 50A and the lower heat exchanger 50B are alternately defrosted while performing normal heating operation. A control device 300 is provided, and the control device 300 sets the rotation speed of the outdoor fan 500 to the minimum rotation speed Rmin that can be taken during the normal heating operation when the upper heat exchanger 50A is defrosted during the heating defrost operation. When controlling and defrosting the lower heat exchanger 50B, the rotation speed of the outdoor fan 500 is controlled to be higher than the minimum rotation speed Rmin.

According to the air conditioner 100 according to the present embodiment, when the upper heat exchanger 50A is defrosted during the heating defrost operation, the rotation speed of the outdoor fan 500 is set to the minimum rotation speed Rmin that can be taken during the normal heating operation. When defrosting the lower heat exchanger 50B, the rotation speed of the outdoor fan 500 is controlled to be higher than the minimum rotation speed Rmin. By doing so, the amount of drain water held on the leeward side of the upper heat exchanger 50A can be suppressed during the defrosting of the upper heat exchanger 50A, and the upper heat exchanger 50A evaporates after the defrosting of the upper heat exchanger 50A. When functioning as a vessel, it is possible to secure the heating capacity while suppressing the drain water held on the leeward side of the upper heat exchanger 50A from refreezing and reducing the heating capacity.

Further, the air conditioner 100 according to the present embodiment includes an outside air temperature detecting device 200 for detecting the outside air temperature, and the control device 300 has an outside air temperature detected by the outside air temperature detecting device 200 during the heating defrost operation. When the temperature is higher than the preset temperature, when defrosting the lower heat exchanger 50B, the rotation speed of the outdoor fan 500 is controlled to be equal to or higher than the rotation speed Ra0 during the normal heating operation immediately before the start of the heating defrost operation. When the outside air temperature detected by the outside air temperature detection device 200 is equal to or lower than the preset temperature, when defrosting the lower heat exchanger 50B, the rotation speed of the outdoor fan 500 is set to the heating immediately before the start of the heating defrost operation. It is controlled to have a rotation speed of Ra0 or less during normal operation.

According to the air conditioner 100 according to the present embodiment, when the outside air temperature is higher than the preset temperature during the heating defrost operation, the rotation speed of the outdoor fan 500 is increased when the lower heat exchanger 50B is defrosted. Is controlled to the rotation speed Ra0 or more during the normal heating operation immediately before the start of the heating defrost operation. By doing so, in the upper heat exchanger 50A, heat can be efficiently collected from the outside air, and the heating capacity can be improved. Further, in the lower heat exchanger 50B, which is a condenser, defrosting can be efficiently promoted by applying a large amount of high-temperature outside air to frost and using the heat energy of the outside air for defrosting.

Further, when the outside air temperature is equal to or lower than the preset temperature during the heating defrost operation, when the lower heat exchanger 50B is defrosted, the rotation speed of the outdoor fan 500 is set to the normal heating immediately before the start of the heating defrost operation. It is controlled to the rotation speed Ra0 or less during operation. By doing so, the upper heat exchanger 50A, which is an evaporator, can efficiently collect heat from the outside air and suppress a decrease in heating capacity. Further, in the lower heat exchanger 50B, which is a condenser, the amount of heat taken away from the outside air from the refrigerant flowing inside can be reduced, and defrosting can be efficiently promoted.

During the heating defrost operation, the opening degree of the second throttle device 60, the operating frequency of the compressor 10, and the opening degree of the first throttle device 30 may be changed as necessary. For example, if it is desired to increase the exchange heat amount of the indoor heat exchanger 40 during the heating defrost operation, the operating frequency of the compressor 10 may be increased. Further, when it is desired to increase the exchange heat amount of the indoor heat exchanger 40, the opening degree of the second throttle device 60 may be changed in the closing direction. In this case, since the flow rate of the refrigerant flowing through the hot gas bypass pipe 88 decreases, the amount of heat exchanged in the heat exchanger to be defrosted decreases. Further, if it is desired to lower the temperature of the refrigerant discharged from the compressor 10, the opening degree of the first drawing device 30 may be changed in the opening direction.

1 outdoor unit, 2 indoor unit, 10 compressor, 20 first flow path switching device, 30 first throttle device, 40 indoor heat exchanger, 50 outdoor heat exchanger, 50A upper heat exchanger, 50B lower heat exchanger, 60 Second throttle device, 70 Second flow path switching device, 80 Hot gas bypass piping, 81-85 refrigerant piping, 86A refrigerant piping, 86B refrigerant piping, 87A refrigerant piping, 87B refrigerant piping, 88 hot gas bypass piping, 89 refrigerant Piping, 90 check valve, 91-96 refrigerant piping, 100 air conditioner, 200 outside air temperature detector, 300 controller, 400 indoor fan, 500 outdoor fan, 600 four-way valve, 700 four-way valve, 900 leeward drainage path.

Claims (2)

A compressor that compresses and discharges the refrigerant,
An indoor heat exchanger that exchanges heat between the refrigerant discharged from the compressor and the indoor air,
The first throttle device that decompresses the refrigerant condensed in the indoor heat exchanger, and
An outdoor heat exchanger that is composed of an upper heat exchanger and a lower heat exchanger whose flow paths are independent of each other and exchanges heat between the refrigerant and the outside air that have passed through the first throttle device.
A refrigerant circuit in which a flow path switching device that selectively switches a flow path to the upper heat exchanger side or the lower heat exchanger side is sequentially connected by piping and a refrigerant circulates.
An outdoor fan that supplies air to the outdoor heat exchanger,
A hot gas bypass pipe connecting the discharge side of the compressor and the flow path switching device, and
The second throttle device provided in the hot gas bypass pipe and
A control device for performing a heating defrost operation in which the upper heat exchanger and the lower heat exchanger are alternately defrosted while performing a normal heating operation is provided.
The control device is
During heating defrost operation
When defrosting the upper heat exchanger, the rotation speed of the outdoor fan is controlled to the minimum rotation speed that can be taken during normal heating operation.
When defrosting the lower heat exchanger, the rotation speed of the outdoor fan is controlled to a rotation speed higher than the minimum rotation speed.
After the defrosting of the lower heat exchanger, the defrosting of the upper heat exchanger is performed, and the defrosting of the lower heat exchanger is performed again.
Air conditioner. Equipped with an outside air temperature detector that detects the outside air temperature,
The control device is
During heating defrost operation
When the outside air temperature detected by the outside air temperature detection device is larger than the preset temperature,
When defrosting the lower heat exchanger, the rotation speed of the outdoor fan is controlled to be equal to or higher than the rotation speed during the normal heating operation immediately before the start of the heating defrost operation.
When the outside air temperature detected by the outside air temperature detection device is equal to or less than the preset temperature,
The air conditioner according to claim 1 , wherein when the lower heat exchanger is defrosted, the rotation speed of the outdoor fan is controlled to be less than the rotation speed during the normal heating operation immediately before the start of the heating defrost operation.

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