WO2020189586A1

WO2020189586A1 - Refrigeration cycle device

Info

Publication number: WO2020189586A1
Application number: PCT/JP2020/011286
Authority: WO
Inventors: 広司中島; 陽冨山
Original assignee: ダイキン工業株式会社
Priority date: 2019-03-20
Filing date: 2020-03-13
Publication date: 2020-09-24
Also published as: JP2020153604A

Abstract

The purpose of the present invention is to provide a refrigeration cycle device such that it is possible to sufficiently melt frost that is attached to an outdoor heat exchanger. An air-conditioning device (1) comprises: a refrigerant circuit (10) which is configured by a compressor (21), an outdoor heat exchanger (23), an outdoor expansion valve (24), and an indoor heat exchanger (31) being sequentially connected, and has a four-way switching valve (22) that can switch between a cooling operation connection state and a heating operation connection state and a bypass pipe (48) that extends from the discharge side of the compressor (21) to between the outdoor heat exchanger (23) and the outdoor expansion valve (24); and a controller (7). During defrosting of the outdoor heat exchanger (23), the controller (7) performs hot gas bypass defrost operation in which the refrigerant is sent from the compressor (21) to the outdoor heat exchanger (23) through the bypass pipe (48) while the refrigerant discharged from the compressor (21) is sent to the indoor heat exchanger (31) in the heating operation connection state, then switches the four-way switching valve (22) to the cooling operation connection state to perform reverse cycle defrost operation in which the refrigerant is sent from the compressor (21) to the outdoor heat exchanger (23).

Description

Refrigeration cycle equipment

This disclosure relates to a refrigeration cycle device.

Conventionally, in refrigeration cycle devices such as air conditioners, frost adheres to the outdoor heat exchanger during heating operation in which the outdoor heat exchanger functions as a refrigerant evaporator and the indoor heat exchanger functions as a refrigerant radiator. Therefore, a defrost operation is performed to melt the frost.

For example, according to Patent Document 1 (International Publication No. 2015/162696), there is a hot gas bypass circuit that connects the discharge side of the compressor and the outdoor heat exchanger and the expansion valve, and the hot gas bypass circuit is provided. An air conditioner has been proposed in which either defrost operation using a gas bypass circuit or reverse cycle defrost operation is selected and executed.

Specifically, in the air conditioner, the hot gas bypass defrost operation in which the refrigerant discharged from the compressor is sent to the outdoor heat exchanger via the hot gas bypass circuit and the refrigerant discharged from the compressor are switched in four ways. Either of the reverse cycle defrost operation, which is sent to the outdoor heat exchanger via the valve, is selected and executed according to the amount of frost formed in the outdoor heat exchanger.

In the air conditioner described in Patent Document 1, the hot gas bypass defrost operation and the reverse cycle defrost operation are selectively executed, but when the reverse cycle defrost operation is selected and executed, it is outdoors. The frost on the downstream side of the refrigerant flow in the heat exchanger may remain undissolved.

The contents of the present disclosure are intended to provide a refrigeration cycle apparatus capable of sufficiently melting the frost adhering to the outdoor heat exchanger.

The refrigeration cycle device according to the first aspect includes a refrigerant circuit and a control unit. In the refrigerant circuit, a compressor, an outdoor heat exchanger, an expansion mechanism, and an indoor heat exchanger are connected in this order. Refrigerant circulates inside the refrigerant circuit. The refrigerant circuit has a switching valve. The switching valve can switch between the first state and the second state. In the first state, the refrigerant discharged from the compressor flows through the indoor heat exchanger to make the indoor heat exchanger function as a radiator. In the second state, the refrigerant discharged from the compressor flows through the outdoor heat exchanger to make the outdoor heat exchanger function as a radiator. The refrigerant circuit has a bypass pipe. The bypass pipe connects between the discharge side of the compressor and the switching valve, between the outdoor heat exchanger and the expansion mechanism, or a portion of the outdoor heat exchanger close to the expansion mechanism. The control unit performs the first control when defrosting the outdoor heat exchanger, and performs the second control after the first control. In the first control, in the first state, the refrigerant discharged from the compressor is sent to the indoor heat exchanger, and the refrigerant is sent from the compressor to the outdoor heat exchanger via the bypass pipe. The second control switches the switching valve to the second state and sends the refrigerant from the compressor to the outdoor heat exchanger.

Here, the part closer to the expansion mechanism in the outdoor heat exchanger means that the effective length of the refrigerant path through which the refrigerant flows in the outdoor heat exchanger is closer to the expansion mechanism than the center.

This refrigeration cycle apparatus melts the frost in the part of the outdoor heat exchanger near the expansion mechanism by performing the first control of sending the refrigerant from the compressor to the frosted outdoor heat exchanger via the bypass pipe. Can be done. Furthermore, by switching the switching valve to the second state and performing the second control to defrost the outdoor heat exchanger by sending the refrigerant from the compressor to the outdoor heat exchanger, it becomes the expansion mechanism of the outdoor heat exchanger. Frost can be melted from the near part to the far part. This makes it possible to sufficiently melt the frost adhering to the outdoor heat exchanger.

The refrigeration cycle device according to the second aspect is the refrigeration cycle device according to the first aspect, and the refrigerant circuit further has a control valve. The control valve is provided in the middle of the bypass pipe.

This refrigeration cycle device can control the flow of refrigerant in the bypass piping by controlling the control valve.

The refrigeration cycle device according to the third aspect is the refrigeration cycle device according to the second aspect, and the control valve is an expansion valve whose valve opening degree can be adjusted.

This refrigeration cycle device can control the flow rate of the refrigerant in the bypass pipe by adjusting the opening degree of the control valve, so that the refrigerant required for melting the frost can flow.

The refrigeration cycle device according to the fourth aspect is the refrigeration cycle device of the second aspect or the third aspect, and the control unit closes the control valve while performing the second control.

Note that closing the control valve while performing the second control means closing the control valve at the same time as the start of the second control, or closing the control valve after the start of the second control and before the end of the second control. included.

In this refrigeration cycle device, the flow of the refrigerant in the bypass pipe is restricted by closing the control valve during the second control, so that the frost melts in the part of the outdoor heat exchanger far from the part near the expansion mechanism. Can be done efficiently.

The refrigerating cycle device according to the fifth aspect is the refrigerating cycle device according to the fourth aspect, and the control unit opens the closed control valve when a predetermined protection condition is satisfied during the second control. ..

The prescribed protection conditions are not particularly limited. As the predetermined protection condition, for example, the temperature of the refrigerant discharged from the compressor, the temperature of the refrigerant sucked into the compressor, and the like may be equal to or less than a predetermined value.

This refrigeration cycle device makes it possible to suppress an abnormality in the temperature of the refrigerant discharged from the compressor and the occurrence of liquid compression in the compressor during the second control.

The refrigeration cycle apparatus according to the sixth aspect is any refrigeration cycle apparatus from the first aspect to the fifth aspect, and the control unit is a third control for lowering the rotation speed of the compressor while performing the first control. I do.

By lowering the rotation speed of the compressor, this refrigeration cycle device can reduce the switching noise that may occur in the switching valve when the switching valve is switched to the second state by using the pressure difference of the refrigerant circuit. .. In this case, by performing the first control using the time required to reduce the rotation speed of the compressor, it is possible to start the second control at an early stage while suppressing the switching sound of the switching valve to be small. ..

The refrigeration cycle device according to the seventh aspect is any of the refrigeration cycle devices from the first aspect to the fifth aspect, and the control unit performs the fourth control while performing the first control. In the fourth control, the rotation speed of the compressor is reduced after maintaining the rotation speed of the compressor.

This refrigeration cycle device is provided with a step of maintaining the rotation speed of the compressor before lowering the rotation speed of the compressor during the first control. By maintaining the rotation speed of the compressor during the first control, it becomes possible to efficiently melt the frost in the portion close to the expansion mechanism of the outdoor heat exchanger.

The refrigeration cycle device according to the eighth viewpoint is any of the refrigeration cycle devices from the first viewpoint to the seventh viewpoint, and the expansion mechanism is an expansion valve whose valve opening degree can be adjusted. During the first control, the control unit controls the valve opening of the expansion mechanism to be smaller than the valve opening during operation immediately before the first control.

Note that the control for making the valve opening of the expansion mechanism smaller than the valve opening during operation immediately before the first control is not particularly limited. As such a control, for example, when the valve opening degree of the expansion mechanism is fixed during the operation immediately before the first control, the control may be smaller than the fixed opening degree. Further, such a control may be a control that is smaller than the control opening degree when the valve opening degree of the expansion mechanism is controlled during the operation immediately before the first control. For example, the opening degree may be smaller than the target valve opening degree by controlling the expansion mechanism immediately before the first control.

In this refrigeration cycle device, during the first control, the valve opening of the expansion mechanism is controlled to be smaller than the valve opening during the operation immediately before the first control, so that the indoor heat exchanger is used via the expansion mechanism. The amount of refrigerant flowing toward the outdoor heat exchanger is suppressed. As a result, it is possible to suppress the degree to which the temperature of the refrigerant supplied to the portion close to the expansion mechanism of the outdoor heat exchanger is lowered by the refrigerant flowing from the indoor heat exchanger to the outdoor heat exchanger via the expansion mechanism. It will be possible.

The refrigeration cycle device according to the ninth aspect is any of the refrigeration cycle devices from the first aspect to the eighth aspect, and further includes a refrigerant temperature sensor. The refrigerant temperature sensor detects the temperature of the refrigerant flowing in a portion close to the expansion mechanism in the outdoor heat exchanger or the temperature of the refrigerant flowing between the outdoor heat exchanger and the expansion mechanism. The control unit ends the second control when a predetermined time elapses from the start of the second control and the detection value of the refrigerant temperature sensor satisfies the predetermined end condition.

This refrigeration cycle device determines the predetermined end condition by using the value detected by the refrigerant temperature sensor after a predetermined time has elapsed from the start of the second control. Therefore, it is possible to prevent the predetermined end condition from being satisfied when the first control is being performed.

The refrigeration cycle apparatus according to the tenth aspect is any of the refrigeration cycle apparatuss from the first aspect to the ninth aspect, and the outdoor heat exchanger has a flat heat transfer tube containing aluminum or an aluminum alloy. ..

In general, outdoor heat exchangers with flat heat transfer tubes containing aluminum or aluminum alloys have lower melted frost than conventional cross fin tube heat exchangers that use cylindrical copper heat transfer tubes. It is hard to flow. In this way, even when using an outdoor heat exchanger in which the melted frost does not easily flow down, the refrigeration cycle device makes it possible to keep the degree to which the melted frost does not easily flow down. Become.

The refrigeration cycle apparatus according to the eleventh aspect is any refrigeration cycle apparatus from the first aspect to the tenth aspect, and the outdoor heat exchanger is the first transmission in which a plurality of heat transfer tubes are arranged side by side in the vertical direction. It has a heat tube group and a second heat transfer tube group. The first heat transfer tube group and the second heat transfer tube group are arranged side by side in the horizontal direction.

This refrigeration cycle device also suppresses the undissolved frost in the part of the outdoor heat exchanger near the expansion mechanism, even for the outdoor heat exchanger in which the refrigerant flows sequentially through the first heat transfer tube group and the second heat transfer tube group. Becomes possible.

It is a schematic block diagram of an air conditioner. It is a schematic block block diagram of an air conditioner. It is an external perspective view of an outdoor heat exchanger. It is explanatory drawing which shows the state of the refrigerant flowing through the outdoor heat exchanger in the cooling operation connection state. It is a layout block diagram of a flat multi-hole tube and a heat transfer fin. It is a time chart of defrost operation. It is a flowchart of defrost operation (No. 1). It is a flowchart of defrost operation (No. 2). It is a schematic block diagram of the air conditioner which concerns on modification A.

Hereinafter, the air conditioner 1 as the refrigeration cycle device according to the present embodiment will be described with reference to FIG. 1 which is a schematic configuration diagram of the refrigerant circuit and FIG. 2 which is a schematic control block configuration diagram.

(1) Outline of Air Conditioning Device 1 The air conditioning device 1 is a device that harmonizes the air in the target space by performing a vapor compression refrigeration cycle.

The air conditioner 1 mainly serves as an outdoor unit 20, an indoor unit 30, a liquid side refrigerant connecting pipe 6 and a gas side refrigerant connecting pipe 5 connecting the outdoor unit 20 and the indoor unit 30, and an input device and an output device. It has a remote controller 8 and a controller 7 that controls the operation of the air conditioner 1.

In the air conditioner 1, a refrigeration cycle is performed in which the refrigerant sealed in the refrigerant circuit 10 is compressed, dissipated (condensed), depressurized, evaporated, and then compressed again. In the present embodiment, the refrigerant circuit 10 is filled with a refrigerant for performing a vapor compression refrigeration cycle.

(1-1) Outdoor unit 20
The outdoor unit 20 is connected to the indoor unit 30 via a liquid-side refrigerant connecting pipe 6 and a gas-side refrigerant connecting pipe 5, and constitutes a part of the refrigerant circuit 10. The outdoor unit 20 mainly includes a compressor 21, a four-way switching valve 22, an outdoor heat exchanger 23, an outdoor expansion valve 24, a low pressure receiver 26, an outdoor fan 25, a liquid side closing valve 29, and a gas. It has a side closing valve 28 and a bypass pipe 48.

The compressor 21 is a device that compresses the low-pressure refrigerant in the refrigeration cycle until it reaches a high pressure. As the compressor 21, for example, a compressor in which a rotary type or scroll type compression element (not shown) is rotationally driven by a compressor motor is used. The compressor motor is for changing the capacity, and the rotation speed can be controlled by an inverter.

The four-way switching valve 22 connects the suction side of the compressor 21 and the gas side closing valve 28 while connecting the discharge side of the compressor 21 and the outdoor heat exchanger 23 by switching the connection state in the refrigerant circuit 10. Heating operation connection between the cooling operation connection state (see the solid line in FIG. 1) and the suction side of the compressor 21 and the outdoor heat exchanger 23 while connecting the discharge side of the compressor 21 and the gas side closing valve 28. The state (see the dotted line in FIG. 1) can be switched. More specifically, the four-way switching valve 22 has a discharge pipe 47 extending from the discharge side of the compressor 21 to one of the connection ports of the four-way switching valve 22 and the outdoor heat exchanger 23 in the cooling operation connection state. Connection of the first pipe 41 and the four-way switching valve 22 for connecting the gas-side closing valve 28 and one of the connection ports of the four-way switching valve 22 while connecting the third pipe 43 extending from the gas side end. A second pipe 42 extending from one of the ports to the low pressure receiver 26 is connected. Further, the four-way switching valve 22 connects the third pipe 43 and the second pipe 42 while connecting the discharge pipe 47 and the first pipe 41 in the heating operation connected state.

The outdoor heat exchanger 23 is a heat exchanger that functions as a radiator or a condenser of a high-pressure refrigerant in a refrigeration cycle during a cooling operation and as an evaporator of a low-pressure refrigerant in a refrigeration cycle during a heating operation.

The outdoor fan 25 supplies the outdoor air into the outdoor unit 20 to the outdoor heat exchanger 23, exchanges heat with the refrigerant in the outdoor heat exchanger 23, and then discharges the air flow to the outside of the outdoor unit 20. Give rise. The outdoor fan 25 is rotationally driven by an outdoor fan motor.

The outdoor expansion valve 24 is provided between the liquid side end of the outdoor heat exchanger 23 and the liquid side closing valve 29. More specifically, the outdoor expansion valve 24 is provided between the fourth pipe 44 extending from the gas side end of the outdoor heat exchanger 23 and the fifth pipe 45 extending from the liquid side closing valve 29. .. As the outdoor expansion valve 24, for example, an electric expansion valve whose valve opening degree can be adjusted by control can be used.

The low pressure receiver 26 is provided between the suction side of the compressor 21 and one of the connection ports of the four-way switching valve 22. Inside the low pressure receiver 26, the end of the second pipe 42 extending from one of the connection ports of the four-way switching valve 22 and the end of the suction pipe 46 extending from the suction side of the compressor 21 are located. There is. The low pressure receiver 26 is a refrigerant container capable of storing the surplus refrigerant in the refrigerant circuit 10 as a liquid refrigerant.

The liquid side closing valve 29 is a manual valve arranged at a connection portion with the liquid side refrigerant connecting pipe 6 in the outdoor unit 20.

The gas side closing valve 28 is a manual valve arranged in the outdoor unit 20 at the connection portion with the gas side refrigerant connecting pipe 5.

The bypass pipe 48 constitutes a refrigerant path connecting the discharge pipe 47 and the fourth pipe 44. A capillary tube 48a that functions as a decompression unit for the passing refrigerant is provided in the middle of the bypass pipe 48. Of the bypass pipe 48, a bypass valve 49, which is an electromagnetic on-off valve whose opening and closing is controlled, is provided between the branch portion from the discharge pipe 47 and the capillary tube 48a.

The outdoor unit 20 has an outdoor unit control unit 27 that controls the operation of each unit constituting the outdoor unit 20. The outdoor unit control unit 27 has a microcomputer including a CPU, a memory, and the like. The outdoor unit control unit 27 is connected to the indoor unit control unit 34 of each indoor unit 30 via a communication line, and transmits and receives control signals and the like.

The outdoor unit 20 is provided with a discharge temperature sensor 83, a suction temperature sensor 84, an outdoor heat exchange temperature sensor 85, an outside air temperature sensor 86, and the like. Each of these sensors is electrically connected to the outdoor unit control unit 27, and transmits a detection signal to the outdoor unit control unit 27. The discharge temperature sensor 83 detects the temperature of the refrigerant flowing through the discharge pipe 47. The suction temperature sensor 84 detects the temperature of the refrigerant flowing through the suction pipe 46. The outdoor heat exchange temperature sensor 85 detects the temperature of the refrigerant flowing through the outlet on the liquid side. The outside air temperature sensor 86 detects the outdoor air temperature before passing through the outdoor heat exchanger 23.

(1-1-1) Outdoor heat exchanger 23
FIG. 3 shows an external perspective view of the outdoor heat exchanger 23, and FIG. 4 shows an explanatory view showing a state of the refrigerant flowing through the outdoor heat exchanger 23 in the cooling operation connected state.

The outdoor heat exchanger 23 has a heat exchange unit 50, a gas side header 54, a liquid side header 56, a first folded header 53, and a second folded header 55. All of these elements of the outdoor heat exchanger 23 are made of aluminum or an aluminum alloy.

The heat exchange unit 50 is arranged on the downstream side in the air flow direction away from the first heat exchange unit 51 and the first heat exchange unit 51 formed on the upstream side in the air flow direction formed by the outdoor fan 25. It also has a second heat exchange unit 52. The first heat exchange unit 51 and the second heat exchange unit 52 are arranged so as to overlap each other in the air flow direction. The first heat exchange unit 51 has a first upper heat exchange unit 51a and a first lower heat exchange unit 51b located below the first upper heat exchange unit 51a. The second heat exchange unit 52 has a second upper heat exchange unit 52a and a second lower heat exchange unit 52b located below the second upper heat exchange unit 52a.

As shown in FIG. 5, the first heat exchange unit 51 and the second heat exchange unit 52 each have a plurality of flat multi-hole tubes 48 and a plurality of heat transfer fins 59. In each of the first heat exchange section 51 and the second heat exchange section 52, the plurality of flat multi-hole pipes 58 are arranged side by side in the vertical direction with the flat surface 58a facing the vertical direction. The flat multi-hole pipe 58 has a plurality of refrigerant flow paths 58b configured side by side along the air flow direction. In each of the first heat exchange section 51 and the second heat exchange section 52, the plurality of heat transfer fins 59 are fixed to the plurality of flat multi-hole tubes. The heat transfer fin 59 has a notch 59a for inserting and fixing the flat multi-hole tube 58.

The gas side header 54 is provided so as to connect the third pipe 43 and the first upper heat exchange unit 51a. Specifically, one end of the third pipe 43 is connected to the gas side header 54, and one end of the plurality of flat multi-hole pipes 58 included in the first upper heat exchange portion 51a is connected to the gas side header 54, respectively. There is.

The liquid side header 56 is provided so as to connect the fourth pipe 44 and the first lower heat exchange section 51b. Specifically, one end of the fourth pipe 44 is connected to the liquid side header 56, and one end of the plurality of flat multi-hole pipes 58 included in the first lower heat exchange portion 51b is connected to the liquid side header 56, respectively. There is.

The first folded header 53 has a first upper folded header 53a and a first downward folded header 53b. The first upper heat exchange header 53a is an end of the first upper heat exchange portion 51a opposite to the gas side header 54 side and an end of the second upper heat exchange portion 52a opposite to the second folded header 55 side. It is provided to contact the department. Specifically, the first upper folded header 53a of the present embodiment includes a plurality of flat multi-hole pipes 58 of the first upper heat exchange portion 51a and a plurality of flat multi-hole pipes 58 of the second upper heat exchange portion 52a. , Are configured to communicate with each other at the same height position. The first lower heat exchange header 53b has an end of the first lower heat exchange portion 51b opposite to the liquid side header 56 side and an end of the second lower heat exchange portion 52b opposite to the second folded header 55 side. It is provided to contact the department. Specifically, the first lower folded header 53b of the present embodiment includes a plurality of flat multi-hole pipes 58 of the first lower heat exchange portion 51b and a plurality of flat multi-hole pipes 58 of the second lower heat exchange portion 52b. , Are configured to communicate with each other at the same height position.

The second folded header 55 is provided so as to connect the second upper heat exchange unit 52a and the second lower heat exchange unit 52b. In the present embodiment, the internal space of the second folded header 55 is separated for each height position, and the spaces separated from each other are connected to each other via a plurality of connecting pipes 55a.

In the above outdoor heat exchanger 23, when the four-way switching valve 22 is in the cooling operation connection state, the refrigerant flows in the direction indicated by the arrow in FIGS. 3 and 4. Specifically, the refrigerant flowing into the gas side header 54 from the third pipe 43 is diverted in the height direction in the gas side header 54, and is a flat multi-hole pipe at each height position of the first upper heat exchange portion 51a. It flows to 58. The refrigerant that has flowed through the first upper heat exchange section 51a flows into the flat multi-hole pipe 58 at each height position of the second upper heat exchange section 52a while maintaining the height position in the first upper folded header 53a. The refrigerant that has flowed through the second upper heat exchange section 52a flows through the second folded header 55 into the flat multi-hole pipe 58 at each height position of the second lower heat exchange section 52b. The refrigerant that has flowed through the second lower heat exchange section 52b flows into the flat multi-hole pipe 58 at each height position of the first lower heat exchange section 51b while maintaining the height position in the first lower folded header 53b. The refrigerant that has flowed through the first lower heat exchange section 51b merges with the liquid side header 56 and flows into the fourth pipe 44. When the four-way switching valve 22 is connected to the heating operation, the refrigerant flow is opposite to the above.

(1-2) Indoor unit 30
The indoor unit 30 is installed on the wall surface, ceiling, or the like of the room, which is the target space. The indoor unit 30 is connected to the outdoor unit 20 via a liquid-side refrigerant connecting pipe 6 and a gas-side refrigerant connecting pipe 5, and constitutes a part of the refrigerant circuit 10.

The indoor unit 30 has an indoor heat exchanger 31 and an indoor fan 32.

The liquid side of the indoor heat exchanger 31 is connected to the liquid side refrigerant connecting pipe 6, and the gas side end is connected to the gas side refrigerant connecting pipe 5. The indoor heat exchanger 31 is a heat exchanger that functions as an evaporator of the low-pressure refrigerant in the refrigeration cycle during the cooling operation and as a radiator or a condenser of the high-pressure refrigerant in the refrigeration cycle during the heating operation.

The indoor fan 32 sucks the indoor air, which is the space to be air-conditioned, into the indoor unit 30, exchanges heat with the refrigerant in the indoor heat exchanger 31, and then discharges the air flow to the outside of the indoor unit 30. Give rise. The indoor fan 32 is rotationally driven by the indoor fan motor.

Further, the indoor unit 30 has an indoor unit control unit 34 that controls the operation of each unit constituting the indoor unit 30. The indoor unit control unit 34 has a microcomputer including a CPU, a memory, and the like. The indoor unit control unit 34 is connected to the outdoor unit control unit 27 via a communication line, and transmits and receives control signals and the like.

The indoor unit 30 is provided with an indoor liquid side heat exchange temperature sensor 91, an indoor air temperature sensor 92, and the like. Each of these sensors is electrically connected to the indoor unit control unit 34, and transmits a detection signal to the indoor unit control unit 34. The indoor liquid side heat exchange temperature sensor 91 detects the temperature of the refrigerant flowing through the liquid side outlet on the side opposite to the side to which the gas side refrigerant connecting pipe 5 is connected in the indoor heat exchanger 31. The indoor air temperature sensor 92 detects the indoor air temperature before passing through the indoor heat exchanger 31.

(1-3) Controller 7
In the air conditioner 1, a controller 7 that controls the operation of the air conditioner 1 is configured by connecting the outdoor unit control unit 27 and the indoor unit control unit 34 via a communication line.

The controller 7 mainly has a CPU (Central Processing Unit) and memories such as ROM and RAM. It should be noted that various processes and controls by the controller 7 are realized by the functions of the outdoor unit control unit 27 and / or the indoor unit control unit 34 in an integrated manner.

(1-4) Remote control 8
The remote controller 8 is arranged in a room which is an air-conditioned space or a specific space of a building including the air-conditioned space, and is used by a user or the like to perform an operation control command of the air conditioner 1 and monitor an operating state. ..

(2) Operation mode The operation mode will be described below.

As the operation mode, a cooling operation mode and a heating operation mode are provided.

The controller 7 determines whether it is the cooling operation mode or the heating operation mode based on the instruction received from the remote controller 8, and executes it.

(2-1) Cooling operation mode In the cooling operation mode, the air conditioner 1 sets the four-way switching valve 22 in the cooling operation connected state and executes the cooling operation.

In the cooling operation, the rotation speed of the compressor 21 is controlled so that, for example, the evaporation temperature of the refrigerant in the refrigerant circuit 10 reaches the target evaporation temperature. The bypass valve 49 is closed during the cooling operation.

The gas refrigerant discharged from the compressor 21 flows through the discharge pipe 47, the four-way switching valve 22, and the third pipe 43, and flows into the outdoor heat exchanger 23. The refrigerant flowing through the outdoor heat exchanger 23 dissipates heat or condenses by exchanging heat with the outdoor air, and flows toward the outdoor expansion valve 24.

Here, the valve opening degree of the outdoor expansion valve 24 is controlled so as to satisfy a predetermined condition such that the degree of supercooling of the refrigerant flowing through the liquid side outlet of the outdoor heat exchanger 23 becomes a target value.

The refrigerant decompressed by the outdoor expansion valve 24 flows into the indoor unit 30 via the liquid side closing valve 29 and the liquid side refrigerant connecting pipe 6, and evaporates in the indoor heat exchanger 31. The refrigerant evaporated in the indoor heat exchanger 31 flows into the outdoor unit 20 from the gas side closing valve 28 via the gas side refrigerant connecting pipe 5. The refrigerant flowing into the outdoor unit 20 is sucked into the compressor 21 again through the second pipe 42, the four-way switching valve 22, the first pipe 41, the low pressure receiver 26, and the suction pipe 46. In the low pressure receiver 26, the liquid refrigerant that could not be completely evaporated in the indoor heat exchanger 31 is stored as a surplus refrigerant.

(2-2) Heating operation mode In the heating operation mode, the air conditioner 1 executes while switching between the heating operation and the defrost operation.

In the heating operation, the number of revolutions of the compressor 21 is controlled so as to generate a predetermined capacity, for example. For example, the rotation speed is controlled so that the condensation temperature of the refrigerant in the refrigerant circuit 10 reaches the target condensation temperature. The bypass valve 49 is closed during the cooling operation.

The gas refrigerant discharged from the compressor 21 flows into the indoor unit 30 after flowing through the discharge pipe 47, the four-way switching valve 22, the second pipe 42, and the gas-side refrigerant connecting pipe 5.

The refrigerant that has flowed into the indoor unit 30 flows into the indoor heat exchanger 31 and exchanges heat with the indoor air in the indoor heat exchanger 31 to dissipate heat or condense. The refrigerant radiated or condensed by the indoor heat exchanger 31 flows into the outdoor unit 20 from the liquid side closing valve 29 via the liquid side refrigerant connecting pipe 6. The refrigerant that has flowed into the outdoor unit 20 is depressurized by the outdoor expansion valve 24.

Here, the valve opening degree of the outdoor expansion valve 24 is controlled so as to satisfy a predetermined condition such that the degree of supercooling of the refrigerant flowing through the liquid side outlet of the indoor heat exchanger 31 becomes a target value.

The refrigerant decompressed by the outdoor expansion valve 24 flows into the outdoor heat exchanger 23 and evaporates by exchanging heat with the outdoor air. The refrigerant evaporated in the outdoor heat exchanger 23 is sucked into the compressor 21 again through the third pipe 43, the four-way switching valve 22, the first pipe 41, the low pressure receiver 26, and the suction pipe 46. In the low pressure receiver 26, the liquid refrigerant that could not be completely evaporated in the outdoor heat exchanger 23 is stored as a surplus refrigerant.

If a predetermined defrost start condition is satisfied during the heating operation in the heating operation mode, the defrost operation is performed to melt the frost adhering to the outdoor heat exchanger 23. Although the details will be described later, when a predetermined defrost start condition is satisfied, the bypass valve 49 is opened while maintaining the connection state of the four-way switching valve 22 in the heating operation connection state, and the refrigerant discharged from the compressor 21 is bypassed. The hot gas bypass defrost operation of sending to the outdoor heat exchanger 23 via 48 is performed. After that, the connection state of the four-way switching valve 22 is switched from the heating operation connection state to the cooling operation connection state, and the reverse cycle defrost operation is performed in which the refrigerant discharged from the compressor 21 is sent to the outdoor heat exchanger 23. Further, when the predetermined defrost end condition is satisfied, the connection state of the four-way switching valve 22 is returned from the cooling operation connection state to the heating operation connection state, and the heating operation is restarted.

(3) Details of Defrost Operation and Operations Before and After Defrost Operation The details of the operation of the air conditioner 1 from performing the defrost operation during the heating operation to returning to the heating operation will be described below.

FIG. 6 shows a timing chart of each element of the air conditioner 1. 7 and 8 show a flowchart of the defrost operation. The portion indicated by "A" in FIG. 7 and the portion indicated by "A" in FIG. 8 indicate that the processing is continuing, and are indicated by the portion indicated by "B" in FIG. 8 and the portion indicated by "B" in FIG. The location indicates that the process is continuing.

In FIG. 6, the column of "compressor" shows the rotation speed of the compressor 21, the column of "indoor fan" shows the airflow by the indoor fan 32, and the column of "outdoor fan" shows the airflow by the outdoor fan 25. The column of "outdoor expansion valve" indicates the valve opening degree of the outdoor expansion valve 24, and all of them indicate that the upper value is higher and the lower value is lower. Further, in FIG. 6, the column of "four-way switching valve" shows the connection state of the four-way switching valve 22, the upper stage is the heating operation connection state, and the lower stage is the cooling operation connection state. It shows each of them. Further, in FIG. 6, the column of "bypass valve" shows the open / closed state of the bypass valve 49, that the bypass valve 49 is open in the upper stage and the bypass valve 49 is closed in the lower stage. Are shown respectively.

In the following, the explanation will start from the state where the heating operation is being performed.

During the heating operation, the four-way switching valve 22 is switched to the heating operation connection state, and the bypass valve 49 is closed. Then, during the heating operation, the rotation speed is controlled so that the compressor 21 produces the required capacity, the indoor fan 32 is controlled to have a set air volume, and the outdoor fan 25 has a predetermined air volume. The outdoor expansion valve 24 is controlled so as to have a predetermined valve opening degree. During the heating operation, the outdoor expansion valve 24 is controlled so as to satisfy a predetermined condition such that the degree of supercooling of the refrigerant flowing through the liquid side outlet of the indoor heat exchanger 31 becomes a target value.

In step S10, the controller 7 determines whether or not the predetermined defrost start condition is satisfied. The predetermined defrost start condition is not particularly limited, but may be, for example, a condition to be satisfied when the temperature and / or the outside air temperature of the refrigerant flowing through the outdoor heat exchanger 23 continues to be equal to or lower than a predetermined value for a predetermined time. .. Here, as the temperature of the refrigerant flowing through the outdoor heat exchanger 23, for example, the detection temperature of the outdoor heat exchange temperature sensor 85 can be used, and as the outside air temperature, the detection temperature of the outside air temperature sensor 86 can be used. .. Here, if it is determined that the predetermined defrost start condition is satisfied, the process proceeds to step S11, and if it is determined that the condition is not satisfied, the heating operation is continued.

In step S11, as pre-defrost control, the controller 7 opens the bypass valve 49 and starts the hot gas bypass defrost operation while maintaining the connection state of the four-way switching valve 22 in the heating operation connection state. In the hot gas bypass defrost operation, the refrigerant discharged from the compressor 21 flows in from the gas side end of the outdoor heat exchanger 23 via the bypass circuit 48 having the capillary tube 48a. As a result, the high-temperature and high-pressure refrigerant discharged from the compressor 21 and having little heat dissipation loss can be supplied to the gas side region of the outdoor heat exchanger 23, and the frost adhering to the region can be removed. It can be melted.

In step S12, the controller 7 controls to reduce the rotation speed of the compressor 21. This makes it possible to suppress the switching sound at the time of switching the four-way switching valve 22, which will be described later, to a small value.

Further, the controller 7 controls to reduce the valve opening degree of the outdoor expansion valve 24 in accordance with the decrease in the rotation speed of the compressor 21. Here, the outdoor expansion valve 24 is controlled so that the valve opening degree is smaller than the valve opening degree during the heating operation. More specifically, the outdoor expansion valve 24 is opened smaller than the valve opening degree controlled so that the degree of supercooling of the refrigerant flowing through the liquid side outlet of the indoor heat exchanger 31 becomes the target value during the heating operation. It is controlled to be a degree. More specifically, the temperature of the refrigerant after merging the refrigerant flowing through the bypass pipe 48 and the refrigerant flowing through the indoor heat exchanger 31, the liquid side refrigerant connecting pipe 6 and the outdoor expansion valve 24 is predetermined. The valve opening degree of the outdoor expansion valve 24 is controlled so as to reach the target temperature of. In the present embodiment, the valve opening degree of the outdoor expansion valve 24 is controlled so that the detection temperature of the outdoor heat exchange temperature sensor 85 becomes a predetermined target temperature.

Further, the controller 7 controls to reduce the air volume without stopping the indoor fan 32. As a result, it is possible to continue heating the room, although the capacity corresponds to the decrease in the number of revolutions of the compressor 21.

Perform each of the above processes and move to step S13.

In step S13, the controller 7 determines whether or not the rotation speed of the compressor 21 that started to be lowered in step S12 is equal to or less than a predetermined value. Here, when the rotation speed of the compressor 21 is equal to or less than a predetermined value, the process proceeds to step S14. If the number of revolutions of the compressor 21 is not equal to or less than a predetermined value, processing such as lowering the number of revolutions of the compressor 21 is continued.

In step S14, the controller 7 closes the bypass valve 49 and ends the hot gas bypass defrost operation.

In step S15, the controller 7 waits for a predetermined time to elapse after the bypass valve 49 is closed, and then proceeds to step S16.

In step S16, the controller 7 ends the pre-defrost control and starts the control during the defrost. Here, the controller 7 switches the connection state of the four-way switching valve 22 from the heating operation connection state to the cooling operation connection state, sets the valve opening of the outdoor expansion valve 24 to the fully open state, and stops the indoor fan 32 and the outdoor fan 25. Control to make it.

In step S17, the controller 7 increases the number of revolutions of the compressor 21 and starts the reverse cycle defrost operation.

In step S18, the controller 7 waits for a predetermined time to elapse after the hot gas bypass defrost operation is completed, and then proceeds to step S19.

In step S19, the controller 7 determines whether or not the predetermined defrost end condition is satisfied. The predetermined defrost end condition is not particularly limited, but may be, for example, a condition to be satisfied when the temperature of the refrigerant flowing through the outdoor heat exchanger 23 becomes equal to or higher than the predetermined temperature. Here, as the temperature of the refrigerant flowing through the outdoor heat exchanger 23, for example, the detection temperature of the outdoor heat exchange temperature sensor 85 can be used.

The detection temperature of the outdoor heat exchange temperature sensor 85, which had risen due to the hot gas bypass defrost operation, decreases as the reverse cycle defrost operation is performed. Then, since the detection temperature of the outdoor heat exchange temperature sensor 85 has decreased due to waiting for the elapse of a predetermined time in step S18, the detection temperature of the outdoor heat exchange temperature sensor 85 raised by the hot gas bypass defrost operation determines the temperature. It is possible to avoid satisfying the defrost termination condition of.

Here, if it is determined that the predetermined defrost end condition is satisfied, the process proceeds to step S20, and if it is determined that the condition is not satisfied, the reverse cycle defrost operation is continued.

In step S20, the controller 7 ends the reverse cycle defrost operation by lowering the rotation speed of the compressor 21 and reducing the valve opening degree of the outdoor expansion valve 24.

In step S21, the controller 7 waits for a predetermined time to elapse after the reverse cycle defrost operation is completed, and then proceeds to step S22.

In step S22, the controller 7 ends the control during defrost and starts the control after defrost. Here, the controller 7 switches the connection state of the four-way switching valve 22 from the cooling operation connection state to the heating operation connection state. Here, in step S21, since the rotation speed of the compressor 21 was lowered and a predetermined time was waited after the reverse cycle defrost operation was completed, the height differential pressure in the refrigerant circuit 10 could be reduced, and the four-way switching valve could be reduced. It is possible to suppress the switching sound of 22 to be small.

In step S23, the controller 7 controls to increase the rotation speed of the compressor 21, increase the valve opening degree of the outdoor expansion valve 24, and increase the air volume of the outdoor fan 25.

In step S24, the controller 7 restarts the heating operation by increasing the air volume of the indoor fan 32 so that a predetermined capacity can be secured.

After resuming the heating operation, the process returns to step S10 and the above process is repeated.

(4) Features of this embodiment (4-1)
In the air conditioner 1 of the present embodiment, the hot gas bypass defrost operation of sending the refrigerant from the compressor 21 to the frosted outdoor heat exchanger 23 via the bypass pipe 48 is performed to perform the hot gas bypass defrost operation of the outdoor heat exchanger 23. The frost adhering to the portion close to the outdoor expansion valve 24 can be melted. More specifically, the frost adhering to the portion of the outdoor heat exchanger 23 near the liquid side end can be melted.

Further, after performing the hot gas bypass defrost operation, the four-way switching valve 22 is connected to the cooling operation and the reverse cycle defrost operation is performed, so that the outdoor heat exchanger 23 is far from the portion close to the outdoor expansion valve 24. The frost attached to the part can be melted. More specifically, the frost adhering to the portion of the outdoor heat exchanger 23 near the gas side end can be melted.

As a result, it is possible to suppress the undissolved residue of frost adhering to the portion of the outdoor heat exchanger 23 near the liquid side end portion, and to melt the frost adhering to various parts of the outdoor heat exchanger 23 as a whole.

In the hot gas bypass defrost operation, it is not always necessary to melt all the frost adhering to the portion of the outdoor heat exchanger 23 near the liquid side end. At the time when the hot gas bypass defrost operation is completed, even if frost remains in the part of the outdoor heat exchanger 23 near the liquid side end, it can be in a melted state to some extent. It is easy to melt by reverse cycle defrost operation.

(4-2)
In the air conditioner 1 of the present embodiment, a part of the refrigerant discharged from the compressor 21 is sent to the indoor heat exchanger 31 during the hot gas bypass defrost operation. Therefore, even during the hot gas bypass defrost operation, the indoor heat exchanger 31 can function as a radiator or a condenser of the refrigerant. This makes it possible to suppress a decrease in the indoor temperature until the reverse cycle defrost operation is started.

Further, in the air conditioner 1 of the present embodiment, when the hot gas bypass defrost operation is performed, the valve opening degree of the outdoor expansion valve 24 is controlled to be smaller than the valve opening degree controlled during the immediately preceding heating operation. Is going. As a result, a large amount of the refrigerant discharged from the compressor 21 and radiated or condensed in the indoor heat exchanger 31 is sent to the liquid side of the outdoor heat exchanger 23 via the liquid side refrigerant connecting pipe 6 and the outdoor expansion valve 24. It is possible to suppress this. As a result, during the hot gas bypass defrost operation, the high-temperature and high-pressure refrigerant discharged from the compressor 21 and flowing through the bypass pipe 48 passes through the indoor heat exchanger 31, the liquid-side refrigerant connecting pipe 6, and the outdoor expansion valve 24. It is possible to keep the degree of cooling by the refrigerant sent to the liquid side of the outdoor heat exchanger 23 small and to increase the melting efficiency of frost on the liquid side of the outdoor heat exchanger 23.

Further, by reducing the valve opening degree of the outdoor expansion valve 24, it becomes possible to store a large amount of liquid refrigerant in the indoor heat exchanger 31 during the hot gas bypass defrost operation. As a result, when the hot gas bypass defrost operation is completed and the reverse cycle defrost operation is started, a large amount of refrigerant, which is a heat source, can be retained on the suction side of the compressor 21. This makes it possible to efficiently melt the frost adhering to the outdoor heat exchanger 23 by the reverse cycle defrost operation.

(4-3)
In the air conditioner 1 of the present embodiment, the rotation speed of the compressor 21 is lowered before the four-way switching valve 22 is switched from the heating operation connection state to the cooling operation connection state. As a result, when the connection state of the four-way switching valve 22 is switched by using the pressure difference of the refrigerant in the refrigerant circuit 10, it is possible to suppress the switching sound generated at the time of switching to be small.

Moreover, in the air conditioner 1 of the present embodiment, the hot gas bypass defrost operation is performed by utilizing the time required for controlling the decrease in the rotation speed of the compressor 21 for suppressing the switching sound of the four-way switching valve 22 to be small. This makes it possible to melt the frost near the gas side end of the outdoor heat exchanger 23. Therefore, the reverse cycle defrost operation can be started early after the defrost start condition is satisfied. Moreover, since the frost near the gas side end of the outdoor heat exchanger 23 has already melted at the start of the reverse cycle defrost operation, the reverse cycle defrost operation can be ended early. As described above, it is possible to shorten the time required from satisfying the defrost start condition to satisfying the defrost end condition, improve the continuity of the heating operation, and suppress the decrease in the indoor temperature. ..

(4-4)
In the air conditioner 1 of the present embodiment, the bypass valve 49 of the bypass pipe 48 is closed during the reverse cycle defrost operation. Therefore, the high-temperature and high-pressure refrigerant discharged from the compressor 21 can be efficiently supplied to the gas side end of the outdoor heat exchanger 23.

(4-5)
In the air conditioner 1 of the present embodiment, the determination of the predetermined defrost operation end condition is performed not immediately after the end of the hot gas bypass defrost operation but after a predetermined time has elapsed from the start of the reverse cycle defrost operation. .. As a result, even if the detection temperature of the outdoor heat exchange temperature sensor 85 may rise due to the hot gas bypass defrost operation, the detection temperature of the outdoor heat exchange temperature sensor 85 will decrease again due to the subsequent reverse cycle defrost operation. , It is possible to prevent the predetermined defrost operation end condition from being unintentionally and early satisfied. This makes it possible to more reliably melt the frost adhering to the outdoor heat exchanger 23.

(4-6)
In the air conditioner 1 of the present embodiment, the outdoor heat exchanger 23 has a flat multi-hole tube 58 having a flat shape containing aluminum or an aluminum alloy. Therefore, as compared with the conventional cross-fin tube heat exchanger in which a cylindrical copper heat transfer tube is used, the melted frost tends to remain on the upper surface of the flat multi-hole tube 58, and it is difficult for the frost to flow downward. As described above, even when the outdoor heat exchanger 23 in which the melted frost does not easily flow downward is used, the defrost operation is performed in the air conditioner 1 of the present embodiment, so that the melted frost is lowered. It is possible to keep the degree of difficulty in flowing small. As a result, for example, refreezing due to frost remaining on the upper surface of the flat multi-hole tube 58 can be suppressed.

Further, the flat multi-hole pipe 58 included in the outdoor heat exchanger 23 has a flat shape, and a plurality of refrigerant flow paths 58b are provided inside. Therefore, the heat exchange efficiency in the outdoor heat exchanger 23 can be improved.

When such an outdoor heat exchanger 23 having high heat exchange efficiency is used, the high temperature and high pressure refrigerant discharged from the compressor 21 is supplied to the outdoor heat exchanger 23 in order to melt the frost adhering during the heating operation. Even in such a case, the refrigerant rapidly loses heat while passing through the inside of the outdoor heat exchanger 23. Therefore, on the side of the outdoor heat exchanger 23 opposite to the inlet side of the high-temperature and high-pressure refrigerant, undissolved frost is particularly likely to occur.

Further, in the outdoor heat exchanger 23 of the present embodiment, as shown in FIG. 4, the refrigerant discharged from the compressor 21 during the reverse cycle defrost operation is the gas side header 54, the first upper heat exchange section 51a, and the first. The upper folded header 53a, the second upper heat exchange section 52a, the second folded header 55, the second lower heat exchange section 52b, the first lower folded header 53b, the first lower heat exchange section 51b, and the liquid side header 56 flow in this order. For this reason, in particular, the refrigerant that has reached the first lower heat exchange section 51b has already released a large amount of heat, and its temperature tends to be low. For this reason, it tends to be difficult to efficiently melt the frost adhering to the first lower heat exchange portion 51b.

On the other hand, in the air conditioner 1 of the present embodiment, the hot gas bypass defrost operation is performed by flowing a high temperature and high pressure refrigerant through the bypass pipe 48 before performing the reverse cycle defrost operation. This makes it possible to efficiently melt the frost adhering to the first lower heat exchange section 51b, which is a portion near the liquid side end portion of the outdoor heat exchanger 23.

(5) Modification example (5-1) Modification example A
In the above embodiment, the case where the capillary tube 48a and the bypass valve 49 which is an electromagnetic on-off valve are provided in the bypass pipe 48 has been described as an example.

On the other hand, for example, as shown in FIG. 9, in the bypass pipe 48, instead of providing the capillary tube 48a and the bypass valve 49 which is an electromagnetic on-off valve, the bypass valve which is an electric expansion valve capable of controlling the valve opening degree. 49a may be provided.

In this case, by controlling the valve opening degree of the bypass valve 49a, it is possible to control the amount of the refrigerant flowing through the bypass pipe 48.

(5-2) Modification B
In the above embodiment, a case where the bypass valve 49 is controlled to be closed when performing the reverse cycle defrost operation has been described as an example.

On the other hand, for example, during the reverse cycle defrost operation, the bypass valve 49 may be controlled to be opened when a predetermined protection condition is satisfied. As a result, a part of the refrigerant discharged from the compressor 21 via the bypass pipe 48 can be supplied to the liquid side of the outdoor heat exchanger 23. Here, during the reverse cycle defrost operation, since the indoor fan 32 is stopped, it may not be possible to sufficiently evaporate the refrigerant in the indoor heat exchanger 31, but even in that case, the indoor heat exchange Since the discharged refrigerant flowing through the bypass pipe 48 can be mixed with the refrigerant sent to the vessel 31, the refrigerant passing through the indoor heat exchanger 31 can be made slightly dry. This makes it possible to suppress the occurrence of liquid compression in the compressor 21.

The predetermined protection condition is not particularly limited, and examples thereof include the temperature of the refrigerant discharged from the compressor 21 and the temperature of the refrigerant sucked into the compressor 21 being equal to or less than a predetermined value.

(5-3) Modification C
In the above embodiment, a case where the rotation speed of the compressor 21 is lowered to start the hot gas bypass defrost operation when a predetermined defrost start condition is satisfied has been described as an example.

On the other hand, for example, when a predetermined defrost start condition is satisfied, the hot gas is controlled to maintain the compressor 21 without lowering the rotation speed before lowering the rotation speed of the compressor 21. The bypass defrost operation may be started. Here, the process of maintaining the rotation speed of the compressor 21 may be performed for a predetermined time, for example, and then the rotation speed of the compressor 21 may be lowered.

As a result, the high-temperature and high-pressure refrigerant discharged from the compressor 21 maintained at a high rotation speed can be supplied to the liquid side end of the outdoor heat exchanger 23 via the bypass pipe 48. This makes it possible to increase the melting efficiency of frost near the liquid side end of the outdoor heat exchanger 23 at the initial stage of the hot gas bypass defrost operation.

(5-4) Modification D
In the above embodiment, the case where the hot gas bypass defrost operation is terminated when the rotation speed of the compressor 21 is sufficiently lowered has been described as an example.

On the other hand, for example, the hot gas bypass defrost operation may be executed for a predetermined time and then terminated.

Further, for example, a refrigerant temperature sensor is provided near the center of the refrigerant path in the outdoor heat exchanger 23, and when the detection value of the temperature sensor exceeds a predetermined value, the hot gas bypass defrost operation is terminated. You may. As such a sensor, for example, it may be a sensor that detects the temperature of the refrigerant passing through the second folded header 55 of the outdoor heat exchanger 23 of the above embodiment.

(5-5) Modification E
In the above embodiment, a case where a predetermined defrost end condition is determined by using the outdoor heat exchange temperature sensor 85 that detects the temperature of the refrigerant flowing through the outlet on the liquid side has been described as an example.

On the other hand, for example, in the fourth pipe 44 of the refrigerant circuit 10, a sensor for detecting the temperature of the refrigerant flowing between the merging portion with the bypass pipe 48 and the outdoor expansion valve 24 is provided, and the detection value of the sensor is provided. May be used to determine a predetermined defrost termination condition. In this case, since the sensor does not detect the temperature of the high-temperature refrigerant discharged from the compressor 21 during the hot gas bypass defrost operation, it is not necessary to wait for a predetermined time described in step S18 of the above embodiment. It becomes possible to do.

Although the embodiments of the present disclosure have been described above, it will be understood that various modifications of the forms and details are possible without departing from the purpose and scope of the present disclosure described in the claims. ..

1 Air conditioner (refrigeration cycle device)
4 Liquid side refrigerant communication pipe 5 Gas side refrigerant communication pipe 7 Controller (control unit)
10 Refrigerant circuit 20 Outdoor unit 21 Compressor 22 Four-way switching valve (switching valve)
23 Outdoor heat exchanger 24 Outdoor expansion valve (expansion mechanism, expansion valve)
30 Indoor unit 31 Indoor heat exchanger 41-45 1st to 5th pipes 46 Suction pipe 47 Discharge pipe 48 Bypass pipe 48a Capillary tube 49 Bypass valve (control valve, on / off valve)
49a Bypass valve (control valve, expansion valve)
58 Flat multi-hole tube (flat heat transfer tube)
83 Discharge temperature sensor 84 Suction temperature sensor 85 Outdoor heat exchange temperature sensor (refrigerant temperature sensor)
86 Outside air temperature sensor

International Publication No. 2015/162696

Claims

A compressor (21), an outdoor heat exchanger (23), an expansion mechanism (24), and an indoor heat exchanger (31) are connected in this order, and a refrigerant circuit (10) in which a refrigerant circulates inside is used.
Control unit (7) and
With
The refrigerant circuit
The first state in which the indoor heat exchanger functions as a radiator by flowing the refrigerant discharged from the compressor through the indoor heat exchanger, and the refrigerant discharged from the compressor is flowed through the outdoor heat exchanger. A switching valve (22) capable of switching between the second state in which the outdoor heat exchanger functions as a radiator and the second state.
A bypass pipe (48) that connects between the discharge side of the compressor and the switching valve, between the outdoor heat exchanger and the expansion mechanism, or a portion of the outdoor heat exchanger close to the expansion mechanism. )When,
Have and
The control unit is used when defrosting the outdoor heat exchanger.
In the first state, while sending the refrigerant discharged from the compressor to the indoor heat exchanger, the first control of sending the refrigerant from the compressor to the outdoor heat exchanger via the bypass pipe is performed.
After the first control, the switching valve is switched to the second state to perform the second control of sending the refrigerant from the compressor to the outdoor heat exchanger.
Refrigeration cycle device (1).
The refrigerant circuit further includes a control valve (49, 49a) provided in the middle of the bypass pipe.
The refrigeration cycle apparatus according to claim 1.
The control valve is an expansion valve (49a) whose valve opening degree can be adjusted.
The refrigeration cycle apparatus according to claim 2.
The control unit closes the control valve while performing the second control.
The refrigeration cycle apparatus according to claim 2 or 3.
The control unit opens the closed control valve when a predetermined protection condition is satisfied during the second control.
The refrigeration cycle apparatus according to claim 4.
While performing the first control, the control unit performs a third control for lowering the rotation speed of the compressor.
The refrigeration cycle apparatus according to any one of claims 1 to 5.
While performing the first control, the control unit performs a fourth control for lowering the rotation speed of the compressor after maintaining the rotation speed of the compressor.
The refrigeration cycle apparatus according to any one of claims 1 to 5.
The expansion mechanism is an expansion valve whose valve opening degree can be adjusted.
While performing the first control, the control unit controls the valve opening of the expansion mechanism to be smaller than the valve opening during operation immediately before the first control.
The refrigeration cycle apparatus according to any one of claims 1 to 7.
A refrigerant temperature sensor (85) for detecting the temperature of the refrigerant flowing in a portion of the outdoor heat exchanger close to the expansion mechanism or the temperature of the refrigerant flowing between the outdoor heat exchanger and the expansion mechanism is further provided.
The control unit terminates the second control when a predetermined time elapses from the start of the second control and the detection value of the refrigerant temperature sensor satisfies the predetermined termination condition.
The refrigeration cycle apparatus according to any one of claims 1 to 8.
The outdoor heat exchanger has a flat heat transfer tube (58) containing aluminum or an aluminum alloy.
The refrigeration cycle apparatus according to any one of claims 1 to 9.
The outdoor heat exchanger has a first heat transfer tube group and a second heat transfer tube group in which a plurality of heat transfer tubes are arranged side by side in the vertical direction.
The first heat transfer tube group and the second heat transfer tube group are arranged side by side in the horizontal direction.
The refrigeration cycle apparatus according to any one of claims 1 to 10.