Refrigeration cycle device

Abstract

Provided is a refrigeration cycle device capable of suppressing operation failure of a four-way valve at low outdoor temperature. The refrigeration cycle device comprises a four-way valve and a control unit. A refrigerant circuit includes a compressor, an indoor heat exchanger, an expansion valve, and an outdoor heat exchanger, and a refrigerant compressed by the compressor circulates in the refrigerant circuit. The four-way valve is connected to the refrigerant circuit and switches the flow direction of the refrigerant circulating in the refrigerant circuit. The control unit controls the compressor, and switches, by switching the four-way valve, between a heating operation in which the refrigerant is circulated in a heating cycle, a cooling operation in which the refrigerant is circulated in a cooling cycle in the flow direction opposite to that of the heating cycle, and a defrosting operation in which defrosting of the outdoor heat exchanger frosted due to the heating operation is performed in the cooling cycle. If the defrosting operation is being performed at the time of reception of an operation stop signal, the control unit stops the compressor after the defrosting operation is finished and the heating operation is performed for a prescribed time or more.

Description

Refrigeration cycle device

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

[0002] The refrigeration cycle device includes an indoor unit having an indoor heat exchanger, and an outdoor unit having an outdoor heat exchanger, a compressor, and a four-way valve. Further, the indoor heat exchanger and the outdoor heat exchanger are connected by a refrigerant circuit through which refrigerant flows. The refrigeration cycle device can perform a cooling operation, a heating operation, or a defrosting operation by switching the flow direction of the refrigerant compressed by the compressor with the four-way valve.

[0003] However, when the four-way valve fails to operate normally due to abnormalities such as foreign matter intrusion or clogging, the refrigeration cycle device may not be able to correctly perform a cooling operation, a heating operation, or a defrosting operation. Therefore, in the above refrigeration cycle device, a technique has been proposed to reduce the occurrence of a malfunction of the four-way valve due to poor plunger movement caused by foreign matter or the like by extending the energization time to the four-way valve during a malfunction (switching malfunction) (for example, Patent Document 1).

[0004] Japanese Unexamined Patent Application Publication No. 2021-4698

[0005] By the way, the above four-way valve switches the refrigerant flow path by moving the position of the slide valve using the high and low pressure difference of the refrigerant. However, when the outside air temperature is low, it is known that the refrigerant density decreases and it becomes difficult for the pressure on the high-pressure side of the refrigerant to rise, so the high and low pressure difference becomes small and it becomes difficult for the slide valve to move. In the technique disclosed in Patent Document 1, the malfunction of the four-way valve caused by the decrease in the high and low pressure difference is not sufficiently considered, and there is a possibility that the four-way valve may malfunction at low outside air temperatures.

[0006] The present invention has been made by paying attention to the conventional unsolved problems, and an object thereof is to provide a refrigeration cycle device capable of suppressing the malfunction of the four-way valve at low outside air temperatures.

[0007] To achieve the above objective, according to one aspect of the present invention, a refrigeration cycle device is provided which includes a compressor, an indoor heat exchanger, an expansion valve, and an outdoor heat exchanger, and comprises a refrigerant circuit through which a refrigerant compressed by the compressor circulates, a four-way valve connected to the refrigerant circuit and switching the direction of flow of the refrigerant circulating in the refrigerant circuit, and a control unit that controls the compressor and switches between a heating operation in which the refrigerant is circulated in a heating cycle, a cooling operation in which the refrigerant is circulated in a cooling cycle with a flow direction opposite to that of the heating cycle, and a defrosting operation in which frost has formed on the outdoor heat exchanger due to the heating operation is defrosted in the cooling cycle, by switching the four-way valve, wherein if the control unit is performing a defrosting operation when it receives an operation stop signal, it stops the compressor after performing a heating operation for a predetermined time or longer after the completion of the defrosting operation.

[0008] According to one aspect of the present invention, a refrigeration cycle device can be obtained that can suppress malfunctions of the four-way valve at low ambient temperatures.

[0009] This is a refrigerant circuit diagram showing an overview of a refrigeration cycle device according to the first embodiment of this disclosure. This is a first diagram showing the functional configuration of a four-way valve according to the first embodiment of this disclosure. This is a second diagram showing the functional configuration of a four-way valve according to the first embodiment of this disclosure. This is a block diagram showing the functional configuration of a control device according to the first embodiment of this disclosure. This diagram shows the state in which the slide valve of the four-way valve in the first embodiment of this disclosure is stopped in the intermediate position. This is a timing chart for explaining an example of the operation of the control device according to the first embodiment of this disclosure. This is a flowchart showing the control processing procedure of the control device according to the first embodiment of this disclosure. This is a block diagram showing the functional configuration of a control device according to the second embodiment of this disclosure. This is a flowchart showing the control processing procedure of the control device according to the second embodiment of this disclosure.

[0010] Next, embodiments of the present invention will be described with reference to the drawings. In the following drawings, identical or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic. Furthermore, the embodiments shown below are illustrative examples of devices and methods for realizing the technical idea of ​​the present invention, and the technical idea of ​​the present invention is not limited to the structure, arrangement, etc. of the components described below. Various modifications can be made to the technical idea of ​​the present invention within the technical scope defined by the claims described in the patent claims.

[0011] <First Embodiment> (Overall Configuration) Figure 1 is a refrigerant circuit diagram showing an overview of a refrigeration cycle device according to the first embodiment of the present disclosure. As shown in Figure 1, the refrigeration cycle device 100 according to the first embodiment of the present disclosure comprises a refrigerant circuit 1 including a compressor 2, an indoor heat exchanger 3, an outdoor heat exchanger 4, an expansion valve 5, a four-way valve 6, and refrigerant piping 7 connecting these, and a control device 20 that controls the refrigerant circuit 1. For example, the indoor heat exchanger 3 is provided in the indoor unit 8, and the compressor 2, outdoor heat exchanger 4, expansion valve 5, and four-way valve 6 are provided in the outdoor unit 9. The indoor heat exchanger 3 is also provided with an indoor heat exchanger temperature sensor 11 for detecting the temperature of the indoor heat exchanger 3.

[0012] The outdoor unit 9 is also equipped with an outside air temperature sensor 12, an outdoor fan 13, and an outdoor heat exchanger temperature sensor 16. The outside air temperature sensor 12 uses, for example, a thermistor and outputs a voltage value that changes according to the outside air temperature as the outside air temperature detection value (hereinafter referred to as outside air temperature) to the control device 20A (an example of a control unit). The outdoor fan 13 is driven by a motor (not shown) to take in outside air into the outdoor unit 9 and generate an airflow to release the outside air that has exchanged heat with the refrigerant in the outdoor heat exchanger 4 to the outside of the outdoor unit 9. The outdoor heat exchanger temperature sensor 16 detects the temperature of the outdoor heat exchanger 4.

[0013] Furthermore, the indoor unit 8 is equipped with an indoor fan 14 and a room temperature sensor 15. The indoor fan 14 is driven by a motor (not shown) to draw in indoor air into the indoor unit 8 and generate an airflow for releasing the air that has exchanged heat with the refrigerant in the indoor heat exchanger 3 back into the room. The room temperature sensor 15 uses, for example, a thermistor and outputs a voltage value that changes according to the indoor temperature as a room temperature detection value to the control device 20A. The compressor 2 compresses the refrigerant and discharges the high-temperature, high-pressure refrigerant after compression into the refrigerant piping 7 (hereinafter referred to as 7-1) for supply. The high-pressure refrigerant compressed by the compressor 2 flows into the port 6a of the four-way valve 6 via the refrigerant piping 7-1.

[0014] During heating operation, the control device 20A controls the four-way valve 6 to connect ports 6a and 6b, and ports 6c and 6d. As a result, during heating operation, the refrigerant flows in the direction of arrow A1. That is, high-temperature, high-pressure refrigerant is supplied to the indoor heat exchanger 3 via the four-way valve 6. The refrigerant releases heat and condenses in the indoor heat exchanger 3. The refrigerant condensed in the indoor heat exchanger 3 is then depressurized by the expansion valve 5, becoming low-pressure refrigerant. This low-pressure refrigerant is supplied to the outdoor heat exchanger 4, where it evaporates, for example, by absorbing heat from the outside air. In other words, during heating operation, the indoor heat exchanger 3 functions as a condenser, and the outdoor heat exchanger 4 functions as an evaporator. The refrigerant evaporated in the outdoor heat exchanger 4 is then drawn into the compressor 2 via the four-way valve 6. The compressor 2 compresses the low-pressure refrigerant again to discharge high-temperature, high-pressure refrigerant.

[0015] On the other hand, during cooling operation, the control device 20A controls the four-way valve 6 to connect ports 6a and 6d, and ports 6b and 6c. As a result, during cooling operation, the refrigerant flows in the direction of arrow A2. That is, the high-temperature, high-pressure refrigerant is supplied to the outdoor heat exchanger 4 via the four-way valve 6, where it condenses by releasing heat into the outside air. The refrigerant condensed in the outdoor heat exchanger 4 is then depressurized by the expansion valve 5 and supplied to the indoor heat exchanger 3. In the indoor heat exchanger 3, the refrigerant evaporates, for example, by absorbing heat from the indoor air. In other words, during cooling operation, the outdoor heat exchanger 4 functions as a condenser, and the indoor heat exchanger 3 functions as an evaporator. The refrigerant evaporated in the indoor heat exchanger 3 is then drawn into the compressor 2 via the four-way valve 6. The compressor 2 compresses the low-pressure refrigerant again to discharge the high-temperature, high-pressure refrigerant.

[0016] The refrigeration cycle device 100 performs heating or cooling by circulating the refrigerant through the repeated process described above. The control device 20A switches between heating and cooling operation by controlling the four-way valve 6. The control device 20A also adjusts the rotation speed of the compressor 2 so that the room temperature reaches the set temperature, based on the difference between the temperature measured by the room temperature sensor 15 and the set temperature set by the user, and performs heating or cooling operation.

[0017] Furthermore, when heating is performed in an environment with low outside temperatures, frost may form on the outdoor heat exchanger 4. To prevent a decrease in heating capacity due to frost formation, the refrigeration cycle device 100 performs a defrosting operation to remove frost from the outdoor heat exchanger 4. During the defrosting operation, the control device 20A switches the four-way valve 6 to set the direction of refrigerant flow to the same direction as during cooling operation (arrow A2 in Figure 1). This supplies high-temperature, high-pressure refrigerant to the outdoor heat exchanger 4 to defrost it.

[0018] (Functional Configuration of the Four-Way Valve) Figure 2 is a first diagram showing the functional configuration of a four-way valve according to the first embodiment of the present disclosure. Figure 3 is a second diagram showing the functional configuration of a four-way valve according to the first embodiment of the present disclosure. As shown in Figures 2 and 3, the four-way valve 6 has a main valve 60 that switches the direction of flow of the refrigerant and a pilot valve 64. The four-way valve 6 according to the first embodiment of the present disclosure is an AC (alternating current) type four-way valve.

[0019] The main valve 60 is formed in a cylindrical shape extending in the direction of the axis O1 and has a slide valve 61 and a pair of pistons 62 inside. The pair of pistons 62 are arranged to face each other on one side and the other side in the direction of the axis O1, dividing the inside of the main valve 60 into a region R1 on one side in the direction of the axis O1 (left side in Figures 2 and 3) and a region R2 on the other side (right side in Figures 2 and 3). The pistons 62 are connected to the slide valve 61 by a connecting member 63 and move the slide valve 61 by moving to one side or the other side in the direction of the axis O1 due to the pressure of the refrigerant introduced into the main valve 60 from the pilot valve 64 described later. As the slide valve 61 moves in conjunction with the movement of the pistons 62, the main valve 60 selectively connects port 6a, into which high-pressure refrigerant from the compressor 2 is introduced, to either port 6b or port 6d, which discharges high-pressure refrigerant.

[0020] The pilot valve 64 is formed in a cylindrical shape extending in the direction of the axis O2, and contains a pilot valve body 65, a solenoid 66, a plunger 67, a coil spring 68, and a permanent magnet 69 inside. A conduit P1 branching from the refrigerant piping 7-1 that connects the compressor 2 and the port 6a of the four-way valve 6 (main valve 60) is connected to one end of the pilot valve 64 in the direction of the axis O2, and high-pressure refrigerant is introduced from this conduit P1. In addition, the pilot valve 64 is connected to a conduit P2 that communicates with region R1 of the main valve 60, a conduit P2 that communicates with region R2, and a conduit P3 branching from the refrigerant piping 7 (hereinafter referred to as 7-2) that connects to the port 6c of the main valve 60.

[0021] The plunger 67 is housed radially inside the solenoid 66 and is biased by the coil spring 68 toward one side in the direction of axis O2 (left side in Figure 3). When heating operation is started, current is applied to the solenoid 66. As a result, as shown in Figure 2, the plunger 67 is attracted by the solenoid 66 toward the other side in the direction of axis O2 (direction of arrow B1 in Figure 2) and is held by the permanent magnet 69.

[0022] At this time, the pilot valve body 65 moves toward the other side in the direction of axis O2 (direction of arrow B1 in Figure 2) as the plunger 67 moves. As a result, conduits P3 and P4 are connected inside the pilot valve body 65, and conduits P1 and P2 are connected outside. The high-pressure refrigerant introduced into the pilot valve 64 from conduit P1 flows into region R1 on the other side of the main valve 60 from conduit P2. At this time, region R1 has a higher pressure than region R2, so the piston 62 of the main valve 60 moves toward the other side in the direction of axis O1 (direction of arrow C1 in Figure 2). As a result, ports 6c and 6d are connected inside the slide valve 61 which has moved with the piston 62, and ports 6a and 6b are connected via region R3 between the pair of pistons. In this way, the high-pressure refrigerant supplied from the compressor 2 is supplied to the indoor heat exchanger 3.

[0023] On the other hand, when cooling operation is started, no current is applied to the solenoid 66. In this case, as shown in Figure 3, the plunger 67 is pushed away from the permanent magnet 69 by the solenoid 66 and biased by the coil spring 68 toward one side in the direction of axis O2 (direction of arrow B2 in Figure 3).

[0024] At this time, the pilot valve body 65 moves toward one side in the direction of axis O2 (direction of arrow B2 in Figure 2) as the plunger 67 moves. As a result, conduits P2 and P3 are connected inside the pilot valve body 65, and conduits P1 and P4 are connected outside. The high-pressure refrigerant introduced from conduit P1 to the pilot valve 64 flows from conduit P4 into region R2 on the other side of the main valve 60. At this time, region R2 has a higher pressure than region R1, so the piston 62 of the main valve 60 moves toward one side in the direction of axis O1 (direction of arrow C2 in Figure 3). As a result, ports 6b and 6c are connected inside the slide valve 61 which has moved with the piston 62, and ports 6a and 6d are connected via region R3 between the pair of pistons. In this way, the high-pressure refrigerant supplied from the compressor 2 is supplied to the outdoor heat exchanger 4. Furthermore, when defrosting operation is started, the four-way valve 6 operates in the same way as in cooling operation.

[0025] (Functional Configuration of Control Device) Figure 4 is a block diagram showing the functional configuration of a control device according to the first embodiment of the present disclosure. The control device 20A according to the first embodiment of the present disclosure includes a temperature acquisition unit 200, an operating mode determination unit 201, a four-way valve control unit 202, and a storage unit 203.

[0026] The temperature acquisition unit 200 acquires the temperature of the indoor heat exchanger 3 from the indoor heat exchanger temperature sensor 11 and the outside air temperature from the outside air temperature sensor 12. The temperature acquisition unit 200 also acquires the indoor temperature from the room temperature sensor 15 and the temperature of the outdoor heat exchanger 4 from the outdoor heat exchanger temperature sensor 16. The operation mode determination unit 201 determines the current operation mode of the refrigeration cycle device 100. The operation mode of the refrigeration cycle device 100 is one of the following: heating operation mode, cooling operation mode, or defrosting operation mode.

[0027] The four-way valve control unit 202 switches the direction of refrigerant flow in the refrigerant circuit 1 by selectively energizing or de-energizing the four-way valve 6. The memory unit 203 stores various data used, acquired, and generated in the processing of each part of the control device 20A. The memory unit 203 also stores a control program that performs the control according to the first embodiment. The control device 20A operates according to the control program stored in the memory unit 203 when the refrigeration cycle device 100 is in heating operation or cooling operation.

[0028] In this first embodiment of the present disclosure, the refrigeration cycle device 100 is equipped with a user-operable remote controller (not shown), and when the user operates the remote controller to start or stop the heating or cooling operation of the refrigeration cycle device 100, the control device 20A executes the start or stop of the heating or cooling operation of the refrigeration cycle device 100.

[0029] (Regarding the behavior when the slide valve of the four-way valve in the first embodiment of this disclosure stops in the intermediate position) Figure 5 shows the state when the slide valve of the four-way valve in the first embodiment of this disclosure stops in the intermediate position. When heating is started, that is, when heating operation begins, the slide valve 61 of the four-way valve 6 may move from the state in which it was stopped in the cooling position due to a defrost operation performed before the operation was stopped, and stop in the intermediate position. In this case, as shown by arrow D1 in Figure 5 (shown as a solid line in Figure 5), the high-pressure refrigerant from the compressor 2 flows to ports 6b and 6d, so that almost no refrigerant flows into port 6c, and the refrigerant does not circulate sufficiently in the refrigerant circuit 1.

[0030] As a result, when the amount of refrigerant flowing out of port 6c decreases and port 6c becomes close to a vacuum, the low pressure decreases. On the other hand, when a small amount of compressed gas (high-pressure gas) is drawn in from the parts E1 and E2 circled in Figure 5 and flows into port 6c as shown by arrow D2 in Figure 5 (shown as a dashed line in Figure 5), operation continues in a state where the high and low pressure difference is small, and the slide valve 61 remains stopped in the intermediate position. Furthermore, this phenomenon of the slide valve 61 stopping in the intermediate position is more likely to occur as the size of the four-way valve 6 increases relative to the exhaust volume of the compressor 2 (the amount of refrigerant circulated is small relative to the size of the slide valve 61).

[0031] (Solution according to the first embodiment of the present disclosure) In the first embodiment of the present disclosure, if the control device 20A receives an operation stop signal while performing defrosting operation, it stops the compressor 2 after performing heating operation for a predetermined time after the completion of defrosting operation. Figure 6 is a timing chart for illustrating an example of the operation of the control device 20A according to the first embodiment of the present disclosure. In Figure 6, the vertical axis shows the rotational speed of the compressor 2 (compressor Hz) and the polarity of the four-way valve 6, and the horizontal axis shows time.

[0032] At time t11, when the control device 20A receives a stop signal from the remote controller held by the user, it terminates the heating operation. If the control device 20A determines that defrosting is necessary, at time t12, it switches the four-way valve 6 to the cooling side and performs defrosting in the cooling cycle for an operating period tm1 until the defrosting operation is completed at time t13. Here, the operating period tm1 is, for example, 15 minutes, or the time until the temperature of the outdoor heat exchanger 4 reaches, for example, 16°C or higher.

[0033] When the defrosting operation is completed, the control device 20A switches the four-way valve 6 to the heating side at time t14 and starts the heating operation. Then, after performing the heating operation for an operating period tm2 from time t14 to time t15, it terminates. This heating operation (hereinafter referred to as pre-stop heating operation) moves the position of the slide valve 61 to the heating side. Here, the operating period tm2 is, for example, 60 seconds, or the time it takes for the slide valve 61 to move completely to the heating position. Furthermore, the rotational speed of the compressor 2 during the pre-stop heating operation should be such that there is a high-low pressure difference sufficient to move the slide valve 61 to the heating position. In other words, the rotational speed of the compressor 2 during the pre-stop heating operation can be lower than that during normal heating operation and defrosting operation.

[0034] Figure 7 is a flowchart showing the control processing procedure of the control device 20A according to the first embodiment of the present disclosure. First, the control device 20A determines whether or not it has received an operation stop signal from a remote controller held by the user during heating operation (step ST7a). If it determines that it has not received an operation stop signal (step ST7a: No), the control device 20A continues the process of determining whether or not it has received an operation stop signal in the process of step ST7a. At this time, the control device 20A monitors what the current operating mode is using the operation mode determination unit 201.

[0035] On the other hand, if it is determined that a stop operation signal has been received (step ST7a: Yes), the control device 20A determines whether defrosting operation is necessary using the temperature acquisition unit 200 and the operation mode determination unit 201 (step ST7b). The conditions under which defrosting operation is necessary are as follows: (1) When a stop operation signal is received during heating operation, the cumulative operating time of heating operation is equal to or greater than a predetermined time (e.g., 30 minutes), the continuous operating time is equal to or greater than a predetermined time (e.g., 10 minutes), and the temperature of the outdoor heat exchanger 4 is equal to or less than a predetermined temperature (e.g., -4°C). (2) When a stop operation signal is received during defrosting operation, the time of defrosting operation is less than the operating period tm1 from time t12 to time t13 as shown in Figure 6.

[0036] If the control device 20A determines that defrosting is necessary (step ST7b: Yes), the temperature acquisition unit 200 determines whether the outside air temperature read from the outside air temperature sensor 12 is at or above a predetermined temperature, for example, -15°C (step ST7c). If it determines that the temperature is below the predetermined temperature (step ST7c: Yes), the control device 20A switches the four-way valve 6 to the cooling side using the four-way valve control unit 202 and performs defrosting (step ST7d), and terminates the defrosting operation by the time t13 shown in Figure 6 (step ST7e).

[0037] Then, the control device 20A, using the four-way valve control unit 202, switches the four-way valve 6 to the heating side and performs heating operation for an operating period tm2 or longer from time t14 to time t15 as shown in Figure 6 (step ST7f), and after time t15 has elapsed, stops the compressor 2 (step ST7g).

[0038] On the other hand, if it is determined in step ST7c that the temperature is above a predetermined level (step ST7c: No), the control device 20A switches the four-way valve 6 to the cooling side using the four-way valve control unit 202 and performs defrosting (step ST7h). The defrosting operation is completed by the time t13 shown in Figure 6 (step ST7i), and the device proceeds to the process of step ST7g without performing pre-stop heating operation to stop the compressor 2. Also, if it is determined in the process of step ST7b that defrosting is not necessary (step ST7b: No), the control device 20A proceeds to the process of step ST7i and stops the compressor 2.

[0039] <Effects of the First Embodiment> As described above, according to the first embodiment, by performing a pre-stop heating operation when the unit is stopped, the four-way valve 6 is switched to the heating position in advance, thereby suppressing switching failures when restarting the heating system. Furthermore, the first embodiment of this disclosure is particularly effective when a four-way valve 6 of a size larger than the exhaust volume of the compressor 2 is selected. In addition, according to the first embodiment, when the outside air temperature is above a predetermined temperature and the possibility of switching failures occurring is low, the time until the unit is stopped can be shortened by not performing a heating operation, thereby contributing to energy saving.

[0040] <Second Embodiment> The second embodiment of this disclosure relates to indoor comfort. The refrigeration cycle device 100 according to the first embodiment is applicable to the refrigeration cycle device according to the second embodiment. Hereinafter, an example of a control device for the refrigeration cycle device according to the second embodiment to which the refrigeration cycle device 100 according to the first embodiment is applied will be described.

[0041] Figure 8 is a block diagram showing the functional configuration of a control device 20B according to a second embodiment of the present disclosure. In Figure 8, the same reference numerals are used for parts that are the same as in Figure 4, and detailed descriptions are omitted. The control device 20B includes an indoor fan control unit 204. The indoor fan control unit 204 controls the driving or stopping of the indoor fan 14.

[0042] FIG. 9 is a flowchart showing the control processing procedure of the control device 20B according to the second embodiment of the present disclosure. First, during the heating operation, the control device 20B determines whether it has received an operation stop signal from the remote controller held by the user (step ST9a). Here, if it is determined that the operation stop signal has not been received (step ST9a: No), the control device 20B continues the determination process of whether the operation stop signal has been received in the process of step ST9a.

[0043] On the other hand, if it is determined that the operation stop signal has been received (step ST9a: Yes), the control device 20B determines whether defrosting operation is necessary by the temperature acquisition unit 200 and the operation mode determination unit 201 (step ST9b). The conditions for the defrosting operation to be necessary are the same as those in the previous first embodiment. Here, if it is determined that the defrosting operation is necessary (step ST9b: Yes), the control device 20B determines whether the outside air temperature read from the outside air temperature sensor 12 by the temperature acquisition unit 200 is equal to or higher than a predetermined temperature, for example, -15°C (step ST9c).

[0044] Here, if it is determined that the temperature is lower than the predetermined temperature (step ST9c: Yes), the control device 20B switches the four-way valve 6 to the cooling side by the four-way valve control unit 202 to execute the defrosting operation (step ST9d), and drives the indoor fan 14 by the indoor fan control unit 204 (step ST9e). Then, the control device 20B ends the defrosting operation until the time t13 shown in FIG. 6 (step ST9f), and stops the indoor fan 14 by the indoor fan control unit 204 (step ST9g).

[0045] Then, the control device 20B switches the four-way valve 6 to the heating side by the four-way valve control unit 202, and executes the pre-stop heating operation during the operation period tm2 from the time t14 to the time t15 shown in FIG. 6 (step ST9h). After the time t15 has elapsed, the compressor 2 is stopped (step ST9i). During this operation period tm2, the control device 20B maintains the stopped state of the indoor fan 14 so as not to drive the indoor fan 14 by the indoor fan control unit 204.

[0046] On the other hand, in step ST9c, when it is determined that the temperature is at or above a predetermined temperature (step ST9c: No), the control device 20B switches the four-way valve 6 to the cooling side by the four-way valve control unit 202 to execute a defrosting operation (step ST9j), and drives the indoor fan 14 by the indoor fan control unit 204 (step ST9k). Then, the control device 20B ends the defrosting operation by the time t13 shown in FIG. 6 (step ST9l), stops the indoor fan 14 by the indoor fan control unit 204 (step ST9m), and proceeds to the process of step ST9i without performing the pre-stop heating operation to stop the compressor 2. Further, in the process of step ST9b, when it is determined that a defrosting operation is not necessary (step ST9b: No), the control device 20B proceeds to the process of step ST9i to stop the compressor 2.

[0047] <Effect of the Second Embodiment> According to the second embodiment as described above, the same effects as those of the previous first embodiment can be obtained, and while the defrosting operation is being performed, by driving the indoor fan 14, defrosting of the outdoor heat exchanger 4 can be efficiently performed. Further, according to the second embodiment, after the user operates the remote controller to instruct operation stop, the indoor fan control unit 204 maintains the indoor fan 14 in a stopped state, and by not blowing air from the indoor fan 14 into the room, a decrease in comfort can be suppressed.

[0048] <Other Embodiments> As described above, the present invention has been described with reference to the first and second embodiments, but it should not be understood that the discussions and drawings forming part of this disclosure limit the present invention. It will be apparent to those skilled in the art that various alternative embodiments, examples, and operation techniques can be included in the present invention if the gist of the technical content disclosed in the above embodiments is understood. Further, the configurations disclosed in the first and second embodiments can be appropriately combined within a range where no contradiction occurs. For example, the configurations disclosed in a plurality of different embodiments may be combined, or the configurations disclosed in a plurality of different modifications of the same embodiment may be combined.

[0049] 1 Refrigerant circuit 2 Compressor 3 Indoor heat exchanger 4 Outdoor heat exchanger 5 Expansion valve 6 Four-way valves 6a, 6b, 6c, 6d Ports 7, 7-1, 7-2 Refrigerant piping 8 Indoor unit 9 Outdoor unit 11 Indoor heat exchanger temperature sensor 12 Outdoor air temperature sensor 13 Outdoor fan 14 Indoor fan 15 Room temperature sensor 16 Outdoor heat exchanger temperature sensor 20A, 20B Control device 60 Main valve 61 Slide valve 62 Piston 63 Connecting member 64 Pilot valve 65 Pilot valve body 66 Solenoid 67 Plunger 68 Coil spring 69 Permanent magnet 100 Refrigeration cycle device 200 Temperature acquisition unit 201 Operating mode determination unit 202 Four-way valve control unit 203 Memory unit 204 Indoor fan control unit P1, P2, P3, P4 conduit R1, R2 area

Claims

1. A refrigeration cycle device comprising: a compressor, an indoor heat exchanger, an expansion valve, and an outdoor heat exchanger, wherein a refrigerant compressed by the compressor circulates through a refrigerant circuit; a four-way valve connected to the refrigerant circuit and switching the direction of flow of the refrigerant circulating through the refrigerant circuit; and a control unit that controls the compressor and switches between a heating operation in which the refrigerant is circulated in a heating cycle, a cooling operation in which the refrigerant is circulated in a cooling cycle with a flow direction opposite to that of the heating cycle, and a defrosting operation in which frost has formed on the outdoor heat exchanger due to the heating operation is defrosted in the cooling cycle, wherein if the control unit is performing the defrosting operation when it receives an operation stop signal, it stops the compressor after performing the heating operation for a predetermined time or longer after the completion of the defrosting operation.

2. The refrigeration cycle apparatus according to claim 1, comprising an outside air temperature sensor for detecting the outside air temperature, wherein when the control unit receives the operation stop signal, if the outside air temperature detected by the outside air temperature sensor is above a predetermined temperature, it stops the compressor without performing the heating operation after the defrosting operation is completed.

3. The refrigeration cycle apparatus according to claim 1, comprising: an indoor fan that takes in indoor air and releases the air, which has exchanged heat with the refrigerant by the indoor heat exchanger, back into the room; and a fan control unit that controls the indoor fan, wherein the fan control unit drives the indoor fan while the defrosting operation is being performed.

4. The refrigeration cycle apparatus according to claim 3, wherein the fan control unit maintains the indoor fan in a stopped state when the heating operation is performed for a predetermined time or longer after the completion of the defrosting operation.

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