Air conditioner and control method

Abstract

Provided is an air conditioner having a function for preventing pooling of refrigerant when an air-warming operation is thermally off or stopped. A multi-type air conditioner having an outdoor unit, a plurality of indoor units, and a control device, the outdoor unit and the plurality of indoor units being connected by refrigerant piping, wherein the control device has: a means for stopping a fan provided to an indoor unit that is executing an air-warming operation when the indoor unit is thermally off, where the indoor temperature has reached a set temperature so that heat exchange in the indoor heat exchanger is unnecessary, or when the indoor unit assumes an air-warming stop state in which the air-warming operation is stopped; a means for increasing the opening degree of an expansion valve provided to the indoor unit when the indoor unit assumes the air-warming stop state; and a means for blocking refrigerant from flowing into and out of the indoor heat exchanger provided to the indoor unit after the fan has been stopped and the opening degree of the expansion valve has been increased.

Description

Technical Field

[0001] The present disclosure relates to an air conditioner and a control method. The present disclosure claims priority based on Japanese Patent Application No. 2023-019760 filed in Japan on February 13, 2023, the contents of which are incorporated herein by reference.Background Art

[0002] As illustrated in Fig. 1, a multi-type air conditioner 100 including a plurality of indoor units 20, 21, 22, and 23 for one outdoor unit 10 is provided. In the multi-type air conditioner 100, since a refrigerant sent out by the outdoor unit 10 is shared by the indoor units 20 to 23, in a case where the refrigerant is excessively accumulated in an indoor heat exchanger of the indoor unit 20, for example, the amount of the refrigerant supplied to the indoor units 21 to 23 is reduced, and the air conditioning capacity of the indoor units 21 to 23 deteriorates. For example, in a case of a thermostat OFF state (the thermostat OFF state means that an indoor temperature reaches a set temperature and the operation state in which heat exchange between the refrigerant flowing through the indoor heat exchanger of the indoor unit 20 and the indoor air is unnecessary) during heating operation of the indoor unit 20, a gas refrigerant supplied to the indoor heat exchanger is condensed and liquefied, and the refrigerant is accumulated in the indoor heat exchanger of the indoor unit 20. This is because, in the multi-type air conditioner 100, even in a case of the thermostat OFF state, the refrigerant is supplied to the indoor heat exchanger and is condensed by operation of a fan or the like. The same event occurs even in a case where the heating operation of the indoor unit 20 is stopped. In recent years, from the viewpoint of safety, the amount of refrigerant sealed in the air conditioner 100 has been reduced, and in a case where refrigerant is accumulated in the indoor heat exchanger, a decrease in air conditioning capacity due to a shortage of refrigerant becomes more noticeable.

[0003] In order to prevent the refrigerant from being excessively accumulated in the indoor heat exchanger of the indoor unit in thermostat OFF state or in which the heating operation is stopped, a control of suppressing condensation of the refrigerant has been provided by controlling the fan or the expansion valve of the indoor unit 20 in the related art, but many of the controls may cause overheating, insufficient heating, generation of abnormal sound, and the like. PTL 1 discloses control of preventing refrigerant from being accumulated in an indoor heat exchanger by opening a gas pipe on an inlet side of the indoor heat exchanger and closing a liquid pipe on an outlet side of the indoor heat exchanger at the time of a thermostat OFF state of heating operation.Citation ListPatent Literature

[0004] [PTL 1] Japanese Unexamined Patent Application Publication No. 5-302765Summary of InventionTechnical Problem

[0005] A control method that can reduce the amount of refrigerant accumulated in the indoor heat exchanger at the time of the thermostat OFF state in the heating operation or at the time of the stop of the heating operation has been demanded.

[0006] The present disclosure provides an air conditioner and a control method capable of solving the above-described problems.Solution to Problem

[0007] According to one aspect of the present disclosure, there is provided a multi-type air conditioner including: an outdoor unit; a plurality of indoor units; and a control device, the outdoor unit and the plurality of indoor units are connected by refrigerant piping, and the control device includes means for stopping a fan provided in the indoor unit in a case where an indoor temperature reaches a set temperature and the indoor unit that is executing a heating operation enters a thermostat OFF state in which heat exchange in an indoor heat exchanger provided in the indoor unit is unnecessary, or enters a heating stop state in which the heating operation is stopped, means for increasing an opening degree of an expansion valve provided in the indoor unit in a case where the heating stop state is reached, and means for shutting off refrigerant flowing into and out from the indoor heat exchanger provided in the indoor unit after the fan is stopped and the opening degree of the expansion valve is increased.

[0008] According to an aspect of the present disclosure, there is provided a control method for a multi-type air conditioner including: an outdoor unit; a plurality of indoor units; and a control device, in which the outdoor unit and the plurality of indoor units are connected by refrigerant piping, the method including: a step of stopping a fan provided in the indoor unit in a case where an indoor temperature reaches a set temperature and the indoor unit that is executing a heating operation enters a thermostat OFF state in which heat exchange in an indoor heat exchanger provided in the indoor unit is unnecessary, or enters a heating stop state in which the heating operation is stopped, a step of increasing an opening degree of an expansion valve provided in the indoor unit in a case where the heating stop state is reached, and a step of shutting off refrigerant flowing into and out from the indoor heat exchanger provided in the indoor unit after the fan is stopped and the opening degree of the expansion valve is increased.Advantageous Effects of Invention

[0009] According to the air conditioner and the control method, the amount of refrigerant accumulated in the indoor heat exchanger can be reduced in thermostat OFF state of the heating operation or in a case where the heating operation is stopped.Brief Description of Drawings

[0010] Fig. 1 is a schematic diagram of a multi-type air conditioner according to an embodiment. Fig. 2 is a schematic diagram illustrating an example of a refrigerant circuit of the multi-type air conditioner according to the embodiment. Fig. 3 is a diagram illustrating an example of a control device of an indoor unit according to the embodiment. Fig. 4 is a first diagram for describing control of a refrigerant temperature on an outlet side of an indoor unit heat exchanger according to the embodiment. Fig. 5 is a second diagram for describing control of a refrigerant temperature on an outlet side of an indoor unit heat exchanger according to the embodiment. Fig. 6 is a flowchart illustrating an example of control for reducing the amount of refrigerant accumulated in the indoor heat exchanger according to the embodiment. Description of Embodiments <Embodiment>

[0011] Hereinafter, an air conditioner and a control method according to an embodiment of the present disclosure will be described with reference to Figs. 1 to 6.(Configuration)

[0012] Fig. 1 is a schematic diagram illustrating an example of a multi-type air conditioner according to the embodiment. The multi-type air conditioner is an air conditioner in which a plurality of indoor units are connected to one outdoor unit. An air conditioner 100 in Fig. 1 is a multi-type air conditioning system including an outdoor unit 10 and a plurality of indoor units 20, 21, 22, and 23. The outdoor unit 10 and each of the indoor units 20 to 23 are connected to each other by refrigerant piping 30 through which a refrigerant passes. The number of the outdoor unit 10, the indoor unit 20, and the like is not limited to the number illustrated in Fig. 1. For example, the number of the indoor units 20 or the like may be two or three, or five or more. The number of the outdoor units 10 may be two or more.

[0013] Fig. 2 illustrates a schematic configuration of a refrigerant circuit of the multi-type air conditioner 100 in a case where one outdoor unit 10, two indoor units 20 (20 and 21), and the like are provided. As illustrated in Fig. 2, the outdoor unit 10 includes a compressor 11, a four-way valve 12, an outdoor heat exchanger 13, and a control device 14. The discharge side of the compressor 11 and the four-way valve 12 are connected to each other by a pipe 34, the four-way valve 12 and the outdoor heat exchanger 13 are connected to each other by a pipe 32, and the four-way valve 12 and the suction side of the compressor 11 are connected to each other by a pipe 33. The four-way valve 12 and the joint 3A are connected to each other by a pipe 35. The outdoor heat exchanger 13 and the joint 3B are connected to each other by a pipe 31. The control device 14 performs control of the compressor 11 or the like.

[0014] The indoor unit 20 includes an indoor heat exchanger 201, an expansion valve 202, a fan 203, a temperature sensor 204, a shut-off valve 205, a temperature sensor 206, and the control device 40. The pipe 36 connects the joint 3A and the indoor heat exchanger 201, and the shut-off valve 205 is provided in the pipe 36. A pipe 37 connects the indoor heat exchanger 201 and the joint 3B, and the expansion valve 202 is provided in the pipe 37. The fan 203 is provided in the vicinity of a suction port of the indoor unit 20, suctions the indoor air, and sends the indoor air to the indoor heat exchanger 201. The temperature sensor 204 is provided in the vicinity of the suction port of the indoor unit 20 and measures an indoor temperature. The temperature sensor 206 is provided in the vicinity of the outlet of the indoor heat exchanger 201 and measures the temperature of the refrigerant on the outlet side of the indoor heat exchanger 201. Whether to set the thermostat OFF state or to set the thermostat ON state in a case where the indoor unit 20 is performing heating operation is determined by a temperature difference between the set temperature for heating of the indoor unit 20 and the temperature measured by the temperature sensor 204. For example, the control device 40 determines that the heating operation is in the thermostat OFF state in a case where the temperature measured by the temperature sensor 204 reaches the set temperature, and determines that the heating operation is in the thermostat ON state in a case where the temperature measured by the temperature sensor 204 is decreased by a predetermined value or more from the set temperature for the heating. The control device 40 controls the expansion valve 202, the fan 203, and the shut-off valve 205.

[0015] The configuration of the indoor unit 21 is the same as the configuration of the indoor unit 20. The indoor unit 21 includes an indoor heat exchanger 211, an expansion valve 212, a fan 213, a temperature sensor 214, a shut-off valve 215, a temperature sensor 216, and the control device 41. The pipe 38 connects the joint 3A and the indoor heat exchanger 211, and the shut-off valve 215 is provided in the pipe 38. A pipe 39 connects the indoor heat exchanger 211 and the joint 3B, and the expansion valve 212 is provided in the pipe 39. The control device 41 controls the expansion valve 212, the fan 213, and the shut-off valve 215.

[0016] In a case where the heating operation is performed by the multi-type air conditioner 100, the four-way valve 12 is set for the heating operation, and the hightemperature and high-pressure gas refrigerant discharged from the compressor 11 is supplied to the indoor heat exchanger 201 of the indoor unit 20 through the pipe 34, the four-way valve 12, and the pipes 35 and 36, and is supplied to the indoor heat exchanger 211 of the indoor unit 21 through the pipes 34, 35, and 38. The shut-off valve 205 and the shut-off valve 215 are usually controlled to be opened. In a case where the shut-off valve 205 is closed, the supply of the gas refrigerant to the indoor heat exchanger 201 is shut off, and in a case where the shut-off valve 215 is closed, the supply of the gas refrigerant to the indoor heat exchanger 211 is shut off. The refrigerant supplied to the indoor heat exchanger 201 is condensed by being heat-exchanged with the air sent by the fan 203, is depressurized by the expansion valve 202, and is supplied to the outdoor heat exchanger 13 through the pipes 37 and 31. Similarly, in the indoor unit 21, the refrigerant supplied to the indoor heat exchanger 211 is condensed by being heat-exchanged with the air sent by the fan 213, is depressurized by the expansion valve 212, and is supplied to the outdoor heat exchanger 13 through the pipes 39 and 31. The refrigerant supplied to the outdoor heat exchanger 13 is vaporized by heat exchange with the outside air, and the vaporized refrigerant is suctioned into the compressor 11 through the pipe 32, the four-way valve 12, and the pipe 33.

[0017] As described with reference to Fig. 2, in the multi-type air conditioner 100, since the refrigerant is shared by the indoor units 20 and 21, for example, in a case where the refrigerant is excessively accumulated in the indoor heat exchanger 201 in the indoor unit 20, the amount of the refrigerant supplied to the indoor unit 21 is reduced. Therefore, for example, in a case where the indoor unit 20 is in the thermostat OFF state or the heating operation of the indoor unit 20 is stopped during the heating operation in the indoor units 20 and 21, the control device 40 performs control of suppressing the refrigerant from being accumulated in the indoor heat exchanger 201. Specifically, the control device 40 stops the fan 203 to reduce the amount of refrigerant condensed in the indoor heat exchanger 201. The control device 40 increases the opening degree of the expansion valve 202 to increase the refrigerant temperature on the outlet side of the indoor heat exchanger 201, and further decreases the amount of refrigerant condensed in the indoor heat exchanger 201. Then, the indoor heat exchanger 201 is shut off at a point in time when the amount of refrigerant condensed in the indoor heat exchanger 201 is reduced, and the flow of refrigerant to the indoor heat exchanger 201 is shut off. Thereafter, in a case where the indoor temperature is decreased to be in the thermostat ON state, or in a case where the heating operation is newly started, the control device 40 releases the shut-off of the indoor heat exchanger 201, restores the opening degree of the expansion valve 202, and operates the fan 203 in a normal manner.(Control for Reducing Amount of Refrigerant Accummulated in Indoor Heat Exchanger)

[0018] Next, the control according to the present embodiment will be described with reference to Figs. 3 to 5. Hereinafter, the control in a case where the indoor unit 20 is in the thermostat OFF state or the heating operation is stopped will be described as an example, but the same applies to other indoor units 21 and the like.

[0019] Fig. 3 is a diagram showing an example of the indoor control device according to the embodiment.

[0020] The control device 40 is a computer device, such as a microcomputer. As shown in the drawing, the control device 40 includes a sensor information acquisition unit 401, a setting receiving unit 402, a storage unit 403, a control unit 404, and a communication unit 405. The control device 40 performs various controls related to the indoor unit 20, but in the present specification, a function related to the control for reducing the amount of refrigerant accumulated in the indoor heat exchanger 201 will be described.

[0021] The sensor information acquisition unit 401 acquires the indoor temperature measured by the temperature sensor 204 and the refrigerant temperature measured by the temperature sensor 206. The sensor information acquisition unit 401 records the acquired temperature in the storage unit 403.

[0022] The setting receiving unit 402 acquires various kinds of setting information input by a user with the remote controller or the like. For example, the setting receiving unit 402 acquires the setting (saturation temperature of the refrigerant) for the refrigerant temperature on the outlet side of the indoor heat exchanger 201. The setting receiving unit 402 records the acquired setting in the storage unit 403.

[0023] The storage unit 403 stores various kinds of information such as a measurement value of the temperature acquired by the sensor information acquisition unit 401 and various kinds of setting information acquired by the setting receiving unit 402. The storage unit 403 stores various programs that realize functions of the control device 40.

[0024] The control unit 404 performs control of the indoor unit 20 and control of the air conditioner 100 in cooperation with the outdoor unit 10. For example, the control unit 404 controls the opening and closing of the shut-off valve 205, the opening degree of the expansion valve 202, the rotation speed of the fan 203, and the like. In a case of the thermostat OFF state of the heating operation or in which the heating operation is stopped, the control unit 404 performs control to (1) stop the fan 203 and (2) increase the opening degree of the expansion valve 202 (opening the expansion valve 202 such that the refrigerant temperature on the outlet side of the indoor heat exchanger 201 reaches the saturation temperature). As a result, the amount of condensation of the refrigerant in the indoor heat exchanger 201 is reduced. (1) By stopping the fan 203, heat exchange is hindered, and thus the amount of condensation of the refrigerant is reduced. By stopping the fan 203, it is possible to prevent the overheating. (2) In a case where the opening degree of the expansion valve 202 is increased, the refrigerant temperature on the outlet side of the indoor heat exchanger 201 rises, and the amount of the liquid refrigerant present in the indoor heat exchanger 201 can be reduced, so that the amount of condensation of the refrigerant is reduced. Fig. 4 schematically shows a state of the indoor heat exchanger 201 during the heating operation. The boundary line 200 indicates a boundary at which the gas refrigerant is changed to the liquid refrigerant. The refrigerant temperature at the boundary is a saturation temperature. Fig. 5 schematically shows a state where the refrigerant temperature on the outlet side of the indoor heat exchanger 201 reaches a saturation temperature under the control of the expansion valve 202 of the present embodiment during the thermostat OFF state or the heating operation is stopped. By increasing the opening degree of the expansion valve 202 to raise the outlet side temperature of the indoor heat exchanger 201, as shown in Fig. 5, the boundary line 200 is moved to the downstream side in the refrigerant flow direction as compared with Fig. 4, and thus the range occupied by the liquid refrigerant present in the indoor heat exchanger 201 can be reduced and the amount of condensation can be reduced. However, in a case where the expansion valve 202 is fully opened, the abnormal sound generated in a case where the refrigerant passes through the expansion valve 202 increases, so that the expansion valve 202 is not fully opened. In a case where the amount of refrigerant to be condensed is reduced by (1) and (2), the control unit 404 shut off the indoor heat exchanger 201 by (3) closing the shut-off valve 205 provided in the gas pipe (pipe 36) and the expansion valve 202 provided in the liquid pipe (pipe 37), and prevents the gas refrigerant from further flowing in and being condensed. The control unit 404 simultaneously fully closes the shut-off valve 205 and the expansion valve 202, or fully closes the shut-off valve 205 and then fully closes the expansion valve 202. The control unit 404 maintains the shut-off valve 205 and the expansion valve 202 in a fully closed state while stopping the fan 203 while the thermostat OFF state of the heating operation or the stop of the heating operation is continued. In a case of the thermostat ON state or in which the heating operation is started, the control unit 404 fully opens the shut-off valve 205, controls the expansion valve 202 to the original opening degree (opening degree in the state of Fig. 4), and operates the fan 203.

[0025] The communication unit 405 communicates with the control device 14 of the outdoor unit 10. For example, the communication unit 405 transmits the temperature measured by the temperature sensor 204 to the control device 14 of the outdoor unit 10. The communication unit 405 receives information indicating the operation state of various sensors, a compressor, and the like provided in the outdoor unit 10 from the control device 14.(Operation)

[0026] Next, control at the time of the thermostat OFF state or the stop of the heating operation will be described with reference to Fig. 6.

[0027] Fig. 6 is a flowchart illustrating an example of control for reducing the amount of refrigerant accumulated in the indoor heat exchanger according to the embodiment.

[0028] As a premise, a saturation temperature of the indoor heat exchanger 201 is set in the storage unit 403. First, the heating operation is stopped or the heating operation is in the thermostat OFF state (step S1). For example, in a case where the user operates the remote controller to stop the heating operation, the heating operation is stopped, and in a case where the temperature measured by the temperature sensor 204 reaches the set temperature, the heating operation is in the thermostat OFF state. Then, the control device 40 starts control for reducing the amount of refrigerant accumulated in the indoor heat exchanger 201. The control unit 404 stops the fan 203 (step S2). Next, the control unit 404 increases the opening degree of the expansion valve 202 (step S3). In this case, the opening is not fully opened in order to prevent the occurrence of an abnormal sound. Steps S2 and S3 in Fig. 6 are executed substantially at the same time. The order of steps S2 and S3 may be reversed. By the control of steps S2 and S3 in Fig. 6, the amount of condensation of the refrigerant in the indoor heat exchanger 201 can be reduced.

[0029] Next, the control unit 404 determines whether or not the refrigerant temperature on the outlet side of the indoor heat exchanger 201 has reached the saturation temperature (step S4). The control unit 404 acquires the temperature measured by the temperature sensor 206 through the sensor information acquisition unit 401, and determines whether or not the temperature has reached the saturation temperature (for example, 45°C). In a case where the saturation temperature is not reached (step S4; No), the control unit 404 waits until the refrigerant temperature on the outlet side of the indoor heat exchanger 201 reaches the saturation temperature. In a case where the saturation temperature is reached (step S4; Yes), the control unit 404 performs control to shut off the indoor heat exchanger 201 (Step S5). Specifically, (a) the control unit 404 simultaneously fully closes the shut-off valve 205 and the expansion valve 202. Alternatively, in order to reduce the amount of refrigerant of the indoor heat exchanger 201, (b) the control unit 404 may first fully close the shut-off valve 205 and then fully close the expansion valve 202. In a case of (b), since the pressure in the indoor heat exchanger 201 decreases after the shut-off valve 205 is fully closed, there is a possibility that the refrigerant flows back from the outlet side. Therefore, the indoor heat exchanger 201 may be shut off by the method of (a). By fully closing the shut-off valve 205 and the expansion valve 202 immediately after the saturation temperature is reached, it is possible to prevent overheating or condensation of the refrigerant due to further inflow of the refrigerant, and it is possible to prevent the refrigerant from being accumulated. While the heating operation is in the thermostat OFF state or is stopped, the control unit 404 stops the fan 203 and maintains a state in which the indoor heat exchanger 201 is shut off.

[0030] Next, the control unit 404 determines whether or not the heating operation is started or is in the thermostat ON state (step S6). For example, in a case where the user operates the remote controller to start the heating operation, the heating operation is started, and in a case where the temperature measured by the temperature sensor 204 is decreased from the set temperature by a predetermined temperature, the heating operation is set to thermostat ON state. In a case where the heating operation is not started or is in the thermostat ON state (step S6: No), the control unit 404 stops the fan 203 and maintains a state in which the indoor heat exchanger 201 is shut off. In a case where the heating operation is started or is in the thermostat ON state (step S6: Yes), the control unit 404 operates the fan 203, restores the opening degree of the expansion valve 202 to the opening degree before the heating is stopped or the thermostat OFF state, and fully opens the shut-off valve 205 to release the shut-off of the indoor heat exchanger 201 (step S7). In the outdoor unit 10, the control device 14 restarts the operation of the compressor 11.

[0031] As described above, according to the present embodiment, in a case of the thermostat OFF state or in which the heating operation is stopped during the heating operation of the indoor unit 20 of the multi-type air conditioner 100, first, the amount of refrigerant to be condensed in the indoor heat exchanger 201 is reduced by stopping the fan and raising the outlet side temperature of the indoor heat exchanger, and then the flow of the refrigerant flowing into and out of the indoor heat exchanger 201 is shut off. As a result, it is possible to prevent the refrigerant from being excessively accumulated in the indoor heat exchanger 201. By preventing the refrigerant from being excessively accumulated in the indoor heat exchanger 201, it is possible to prevent a decrease in air conditioning capacity due to a shortage of refrigerant in the other indoor units 21 and the like. It is suitable even in a situation where the amount of refrigerant sealed has been reduced in recent years.

[0032] In the above-described embodiment, the shut-off valve is provided for each indoor unit, but one shut-off valve may be provided for a plurality of indoor units (for example, one shut-off valve is provided on the upstream side of the refrigerant flow of the joint 3A in Fig. 2). In the above-described embodiment, the opening degree of the expansion valve 202 is increased, waits until the temperature on the outlet side of the indoor heat exchanger 201 becomes the saturation temperature, and the shut-off valve 205 and the expansion valve 202 are fully closed. However, for example, an approximate time until the temperature becomes the saturation temperature may be derived by an experiment, a calculation, or the like, and this time may be set as the holding time. Then, in a case where the holding time has elapsed after the opening degree of the expansion valve 202 is increased, the control unit 404 may perform control such that the shut-off valve 205 and the expansion valve 202 are fully closed.

[0033] The processing in Fig. 6 is a function realized by the processor provided in the control device 40 reading out and executing the program from the storage unit 403.

[0034] In addition, the components of the above-mentioned embodiment can be appropriately replaced with well-known components without departing from the scope of the present invention. The scope of the present invention is not limited to the above-mentioned embodiment, and the present invention can include various changes without departing from the scope of the present invention.<Additional Notes>

[0035] The air conditioner and the control method described in the embodiment are understood, for example, as follows. (1) An air conditioner 100 according to a first aspect is a multi-type air conditioner including: an outdoor unit 10; a plurality of indoor units 20 to 23; and a control device 40, in which the outdoor unit 10 and the plurality of indoor units 20 to 23 are connected by refrigerant piping 30, and the control device 40 includes means (control unit 404, S2) for stopping a fan provided in the indoor unit in a case where an indoor temperature reaches a set temperature and the indoor unit 20 that is executing a heating operation enters a thermostat OFF state in which heat exchange in an indoor heat exchanger 201 provided in the indoor unit is unnecessary, or enters a heating stop state in which the heating operation is stopped, means (control unit 404, S3) for increasing an opening degree of an expansion valve provided in the indoor unit in a case where the heating stop state is reached, and means (control unit 404, S5) for shutting off refrigerant flowing into and out from the indoor heat exchanger provided in the indoor unit after the fan is stopped and the opening degree of the expansion valve is increased. With the above configuration, it is possible to reduce the amount of refrigerant accumulated in the indoor heat exchanger 201 in a case where the heating operation is in a thermostat OFF state or in a case where the heating operation is stopped. (2) An air conditioner 100 according to a second aspect is the air conditioner 100 of (1), in which the control device 40 increases the opening degree of the expansion valve 202 such that a temperature of the refrigerant on an outlet side of the indoor heat exchanger reaches a saturation temperature. With the above configuration, it is possible to reduce the amount of refrigerant to be condensed in the indoor heat exchanger 201. (3) An air conditioner 100 according to a third aspect is the air conditioner of (1) or (2), in which the control device 40 continues to stop the fan 203 (S2) and to shut off the refrigerant (S5) until the heating stop state ends. With the above configuration, it is possible to prevent the refrigerant from being accumulated in the indoor heat exchanger 201 during the heating is in a thermostat OFF state or stopped. (4) An air conditioner 100 according to a fourth aspect is the air conditioner of (1) to (3), in which the control device 40 fully closes a shut-off valve 205 provided in a gas pipe connected to the indoor heat exchanger 201 and the expansion valve 202 provided in a liquid pipe connected to the indoor heat exchanger 201 at the same time to shut off the refrigerant. With the above configuration, it is possible to shut off the refrigerant flowing into and flowing out of the indoor heat exchanger 201 without a risk of refrigerant backflow. (5) An air conditioner 100 according to a fifth aspect is the air conditioner of (1) to (4), in which the control device 40 first fully closes a shut-off valve provided in a gas pipe connected to the indoor heat exchanger 201 and then fully closes the expansion valve 202 provided in a liquid pipe connected to the indoor heat exchanger to shut off the refrigerant. With the above configuration, it is possible to shut off the refrigerant flowing into and flowing out of the indoor heat exchanger 201. (6) An air conditioner 100 according to a sixth aspect is the air conditioner of (1) to (5), in which the control device 40 does not fully open the expansion valve 202 in a case where the opening degree of the expansion valve 202 is increased. With the above configuration, it is possible to prevent the occurrence of an abnormal sound. (7) An control method according to a seventh aspect is a control method for a multi-type air conditioner including: an outdoor unit 10; and a plurality of indoor units 20 to 23, in which the outdoor unit 10 and the plurality of indoor units 20 to 23 are connected by refrigerant piping 30, the method including: a step (S2) of stopping a fan 203 provided in the indoor unit 20 in a case where an indoor temperature reaches a set temperature and the indoor unit 20 that is executing a heating operation enters a thermostat OFF state in which heat exchange in an indoor heat exchanger provided in the indoor unit is unnecessary, or enters a heating stop state in which the heating operation is stopped, a step (S3) of increasing an opening degree of an expansion valve 202 provided in the indoor unit 20 in a case where the heating stop state is reached, and a step (S5) of shutting off refrigerant flowing into and out from the indoor heat exchanger 201 provided in the indoor unit 20 after the fan 203 is stopped and the opening degree of the expansion valve 202 is increased. Industrial Applicability

[0036] According to the air conditioner and the control method, the amount of refrigerant accumulated in the indoor heat exchanger can be reduced in thermostat OFF state of the heating operation or in a case where the heating operation is stopped.Reference Signs List

[0037] 10: outdoor unit 11: compressor 12: four-way valve 13: outdoor heat exchanger 14: control device 20: indoor unit 201: indoor heat exchanger 202: expansion valve 203: fan 204: temperature sensor 205: shut-off valve 206: temperature sensor 21: indoor unit 211: indoor heat exchanger 212: expansion valve 213: fan 214: temperature sensor 215: shut-off valve 216: temperature sensor 22: indoor unit 23: indoor unit 30 to 39: pipe 3A, 3B: joint 40, 41: control device 401: sensor information acquisition unit 402: setting receiving unit 403: storage unit 404: control unit 405: communication unit 100: air conditioner

Claims

1. A multi-type air conditioner comprising: an outdoor unit; a plurality of indoor units; and a control device, wherein the outdoor unit and the plurality of indoor units are connected by refrigerant piping, and the control device includes means for stopping a fan provided in the indoor unit in a case where an indoor temperature reaches a set temperature and the indoor unit that is executing a heating operation enters a thermostat OFF state in which heat exchange in an indoor heat exchanger provided in the indoor unit is unnecessary, or enters a heating stop state in which the heating operation is stopped, means for increasing an opening degree of an expansion valve provided in the indoor unit in a case where the heating stop state is reached, and means for shutting off refrigerant flowing into and out from the indoor heat exchanger provided in the indoor unit after the fan is stopped and the opening degree of the expansion valve is increased.

2. The air conditioner according to Claim 1, wherein the control device increases the opening degree of the expansion valve such that a temperature of the refrigerant on an outlet side of the indoor heat exchanger reaches a saturation temperature.

3. The air conditioner according to Claim 1 or 2, wherein the control device continues to stop the fan and to shut off the refrigerant until the heating stop state ends.

4. The air conditioner according to Claim 1 or 2, wherein the control device fully closes a shut-off valve provided in a gas pipe connected to the indoor heat exchanger and the expansion valve provided in a liquid pipe connected to the indoor heat exchanger at the same time to shut off the refrigerant.

5. The air conditioner according to Claim 1 or 2, wherein the control device first fully closes a shut-off valve provided in a gas pipe connected to the indoor heat exchanger and then fully closes the expansion valve provided in a liquid pipe connected to the indoor heat exchanger to shut off the refrigerant.

6. The air conditioner according to Claim 1 or 2, wherein the control device does not fully open the expansion valve in a case where the opening degree of the expansion valve is increased.

7. A control method for a multi-type air conditioner including: an outdoor unit; a plurality of indoor units; and a control device, in which the outdoor unit and the plurality of indoor units are connected by refrigerant piping, the method comprising: a step of stopping a fan provided in the indoor unit in a case where an indoor temperature reaches a set temperature and the indoor unit that is executing a heating operation enters a thermostat OFF state in which heat exchange in an indoor heat exchanger provided in the indoor unit is unnecessary, or enters a heating stop state in which the heating operation is stopped, a step of increasing an opening degree of an expansion valve provided in the indoor unit in a case where the heating stop state is reached, and a step of shutting off refrigerant flowing into and out from the indoor heat exchanger provided in the indoor unit after the fan is stopped and the opening degree of the expansion valve is increased.

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