JP2017116136A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner that can maintain an oil level in a compressor at a predetermined position, can appropriately set circulation amount of lubricating oil circulating in a refrigeration cycle and can secure the amount of the lubricating oil in the compressor even when an increase in the discharge amount of the lubricating oil from the compressor is assumed, without causing a decline of separation efficiency of an oil separator and an increase in the size.SOLUTION: An air conditioner includes: first oil return piping 15 connected to an oil separator 5; second oil return piping 16 opened at an oil level higher than the first oil return piping of the oil separator 5; a first solenoid valve 17 provided in the first oil return piping 15; a second solenoid valve 19 provided in the second oil return piping 16; and a control device 23 for performing opening/closing control of the first solenoid valve 17 and the second solenoid valve 19. At start of an operation of and during load fluctuation of the air conditioner 1, the control device 23 opens the first solenoid valve 17 and closes the second solenoid valve 19 for a predetermined time.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an air conditioner including a compressor and an oil separator in an outdoor unit, and more particularly to an air conditioner having a compressor driven by an external drive source.

  Generally, in an air conditioner using a heat pump, lubricating oil is used to smoothly drive a compressor that compresses a refrigerant. This lubricating oil is discharged into the refrigeration cycle together with the refrigerant compressed by the compressor, circulates in the refrigeration cycle, and returns to the compressor again.

  In order to keep the amount of lubricating oil circulating in the refrigeration cycle appropriately in this way, conventionally, in such an air conditioner, an oil return pipe is connected with an interval above and below the oil separator, and each oil return If the pipe length is long, close the shutoff valve on the upper oil return pipe, open the shutoff valve on the lower oil return pipe, and set the pipe length to If it is short, open the upper oil return pipe shut-off valve and open the lower oil return pipe shut-off valve to store the lubricating oil in the oil separator and reduce the amount of lubricating oil circulating in the refrigeration cycle. Proposals for keeping it appropriate have been made (see, for example, Patent Document 1).

JP 2012-145251 A

  In the technique of Patent Document 1 described above, when the refrigerant pipe length constituting the refrigeration cycle is long, the lubricating oil is not stored in the oil separator, and the refrigerant pipe is short. For example, surplus lubricating oil circulates in the refrigeration cycle. When this occurs, the amount of lubricating oil circulating in the refrigeration cycle is adjusted by storing excess lubricating oil in the oil separator. Therefore, in the technique of Patent Document 1, when the refrigerant pipe length constituting the refrigeration cycle is short, the oil separator also serves as the lubricating oil storage container.

  The oil separator is usually composed of a separation space for separating the refrigerant and the lubricating oil and a storage space for storing the separated lubricating oil. However, when the amount of lubricating oil stored in the oil separator increases, the oil separator is separated. There is a problem that the space is reduced, the refrigerant and the lubricating oil cannot be sufficiently separated, and the circulation amount of the lubricating oil circulating in the refrigeration cycle is increased. When the amount of lubricating oil circulating in the refrigeration cycle increases in this way, the lubricating oil stays in the connecting piping and heat exchanger, and narrowing the flow path causes an increase in refrigerant pressure loss and heat exchange. This hinders heat exchange between the refrigerant and air, causing a drop in performance.

  In order to solve such a problem, a method of enlarging an oil separator and securing a separation space and a storage space can be considered. However, in this case, new problems such as an increase in size and cost of the apparatus arise. In addition, in a compressor having an external drive source as a drive source of a compressor, for example, a gas engine heat pump, the rotation speed of the compressor depends on the rotation speed of the gas engine, so that the rotation speed at startup is electrically driven compression. Compared to the machine, the amount of lubricating oil discharged at startup is large. For this reason, in a gas engine heat pump, a large amount of lubricating oil is sealed in advance in the refrigeration cycle in order to ensure reliability when the compressor is started. Therefore, the above-mentioned problem becomes more remarkable in the case of a gas engine type heat pump.

  The present invention has been made in view of the above points, and even when surplus occurs in the amount of lubricating oil in the refrigeration cycle, such as during short piping, without causing a reduction in separation efficiency or an increase in size of the oil separator, When the oil level in the compressor is held at a predetermined position, the amount of lubricating oil circulating in the refrigeration cycle can be set appropriately, and the amount of lubricating oil discharged from the compressor is assumed to increase. Another object of the present invention is to provide an air conditioner that can secure the amount of lubricating oil in the compressor.

In order to achieve the above object, an air conditioner according to the present invention includes a compressor driven by an external drive source, an oil separator, a four-way valve, an outdoor heat exchanger, an expansion mechanism, an indoor unit including an indoor heat exchanger, and an accumulator. In an air conditioner equipped with a connected refrigeration cycle,
A first oil return pipe connected to a bottom surface of the oil separator and connected to a suction side pipe between the suction port of the compressor and the accumulator; and higher than the first oil return pipe of the oil separator A second oil return pipe that opens to the oil surface and is connected to a low pressure side pipe between the accumulator and the four-way valve; a first solenoid valve provided in the first oil return pipe; Based on the flow path resistance, the second solenoid valve and the second flow path resistance provided in the second oil return pipe, and the operating state of the refrigeration cycle, the first solenoid valve and the second solenoid valve And a control device for controlling opening and closing of
The control device opens the first electromagnetic valve and closes the second electromagnetic valve for a predetermined time when the refrigeration cycle is started up and when the load fluctuates, and after the predetermined time has elapsed, the first electromagnetic valve is closed. Is closed and the second electromagnetic valve is opened.

  By configuring in this way, the first solenoid valve is open and the second solenoid valve is closed at the time of start-up, load fluctuation, etc., so that the lubricating oil separated by the oil separator is positive. Returned to the compressor. Also, when there is a surplus in the lubricating oil in the refrigeration cycle, such as during refrigeration cycle stable operation, the first solenoid valve is closed and the second solenoid valve is open. Since the position of one end of the return pipe opens to a higher oil level than the first oil return pipe of the oil separator, the separated lubricating oil is stored in the oil separator up to the opening position of the second oil return pipe. At the same time, since the connection position of the other end is a low-pressure pipe upstream of the accumulator, the lubricating oil that has passed through the second oil return pipe is also stored in the accumulator.

  In the above configuration, the first flow path resistance is smaller than the second flow path resistance. With this configuration, the return flow rate of the lubricating oil to the compressor is larger when the first oil return pipe is used than when the second oil return pipe is used. With the configuration, the oil return flow rate to the compressor can be adjusted.

  In the above configuration, the second oil return pipe is connected to a side surface of the oil separator. By comprising in this way, the position of the end of the 2nd oil return piping can be opened to the oil level higher than the 1st oil return piping of an oil separator.

  According to the present invention, when the opening and closing of the first solenoid valve and the second solenoid valve are switched based on the operating state of the refrigeration cycle, a large amount of compressor oil is required, such as when starting up or when the load fluctuates. It is possible to positively return the lubricating oil separated by the oil separator to the compressor and store the lubricating oil separated by the oil separator in both the oil separator and the accumulator when the refrigeration cycle is stable. Therefore, storing the lubricating oil in both the oil separator and the accumulator is expected to reduce the separation rate and increase the size of the oil separator and increase the amount of lubricating oil discharged from the compressor. In this case, the amount of lubricating oil in the compressor can be secured.

It is a whole lineblock diagram showing an embodiment of an air harmony device concerning the present invention. It is detail drawing of the compressor and oil separator in embodiment of the air conditioning apparatus which concerns on this invention. It is a schematic block diagram of the compressor in embodiment of the air conditioning apparatus which concerns on this invention. It is a flowchart which shows the operation | movement in embodiment of the air conditioning apparatus which concerns on this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited by this embodiment.
In the present embodiment, an air conditioner in which one outdoor unit and two indoor units are connected to each other through a refrigerant pipe will be described, but there may be a plurality of outdoor units. Further, the number of indoor units is not limited to two, and may be three or more.

  As shown in FIG. 1, the air conditioner 1 according to the present embodiment includes one outdoor unit 2 and two indoor units 3. The outdoor unit 2 includes a compressor 4 driven by an external drive source (not shown), an oil separator 5, a four-way valve 6, an outdoor heat exchanger 7, an outdoor expansion mechanism 8, an accumulator 9, and refrigerant pipes connecting these components ( The refrigerant gas pipe 10 and the refrigerant liquid pipe 11) are configured. Moreover, the indoor unit 3 is comprised by the indoor heat exchanger 12, the indoor expansion mechanism 13, and the refrigerant | coolant piping (refrigerant gas piping 10, the refrigerant | coolant liquid piping 11) which connects these.

  As shown in FIG. 3, the compressor 4 is configured to compress the gas refrigerant sucked from the suction side pipe 21 in the cylinder 24 by being driven to rotate by an external drive source (not shown). The refrigerant discharged from the cylinder discharge port 25 is further separated from the oil discharged together with the refrigerant compressed by the cyclone block 26 and discharged from the case discharge port 27. The oil separator 5 separates the oil contained in the refrigerant discharged from the compressor 4 from the refrigerant and causes the compressor 4 to recirculate. The four-way valve 6 is provided in the refrigerant gas pipe 10 and switches the circulation direction of the refrigerant discharged from the compressor 4 according to the operation mode (cooling mode, heating mode). In FIG. 1, the refrigerant flow in the cooling mode is indicated by solid arrows, and the refrigerant flow in the heating mode is indicated by broken arrows.

  The outdoor heat exchanger 7 performs heat exchange between the outside air and the refrigerant by blowing air from an outdoor fan (not shown), and is configured to function as a condenser in the cooling mode and as an evaporator in the heating mode. Yes. The outdoor expansion mechanism 8 is provided in the refrigerant liquid pipe 11 and decompresses and expands the refrigerant flowing into the outdoor heat exchanger 7 in the heating mode. For example, a capillary tube or an electronic expansion valve is used. The accumulator 9 is provided in the refrigerant gas pipe 10 on the suction side of the compressor 4, gas-liquid separates the refrigerant flowing into the compressor 4, stores the liquid refrigerant, and sends only the gas refrigerant to the compressor 4. .

  The indoor heat exchanger 12 exchanges heat with air by blowing air from a refrigerant flowing inside and an indoor fan (not shown), and functions as an evaporator in the cooling mode and as a condenser in the heating mode. It is configured as follows. The indoor expansion mechanism 13 is provided in the refrigerant liquid pipe 11, and decompresses and expands the refrigerant flowing into the indoor heat exchanger 12 during the cooling operation. For example, a capillary tube or an electronic expansion valve is used.

  In addition, as shown in FIG. 2, the oil separator 5 is provided with a first oil return pipe 15 and a second oil return pipe 16. One end of a first oil return pipe 15 is connected to the bottom surface of the oil separator 5, and the other end of the first oil return pipe 15 is a suction side pipe between the suction port of the compressor 4 and the accumulator 9. 21 is connected. Furthermore, the first oil return pipe 15 is provided with a first flow path resistance 18 such as a first electromagnetic valve 17 and a capillary tube capable of opening and closing the flow path.

  One end of the second oil return pipe 16 is connected to the side surface of the oil separator 15, and the other end of the second oil return pipe 16 is connected to the low-pressure side pipe 22 upstream of the accumulator 9. ing. Further, the second oil return pipe 16 is provided with a second electromagnetic valve 19 capable of opening and closing the flow path and a second flow path resistance 20 such as a capillary tube. The suction side pipe 21 communicates with the inside of the accumulator 9, and a small hole (not shown) is provided in the lower part of the accumulator 9, and the lubricating oil stored in the lower part of the accumulator 9 is supplied to the suction side pipe 21. It is structured to return to the compressor 4 together with the flowing refrigerant.

  The control device 23 controls the four-way valve 6, the outdoor fan, the indoor fan, the outdoor expansion mechanism 8, and the indoor expansion mechanism 13 so as to obtain a desired air conditioning state set by an operation panel (not shown) and the compressor 4. It is comprised so that the rotation speed of may be controlled. Further, in the present embodiment, the control device 23 is configured to control the opening and closing of the first electromagnetic valve 17 and the second electromagnetic valve 18 based on the operating state of the refrigeration cycle.

Next, the operation in the cooling mode of this embodiment will be described.
In the cooling mode, the refrigerant discharged from the compressor 4 is sequentially guided to the oil separator 5, the four-way valve 6, and the outdoor heat exchanger 7, and is condensed and liquefied by receiving air from the outdoor fan in the outdoor heat exchanger 7. The Thereafter, the refrigerant is sent to the outdoor heat exchanger 7, the indoor expansion mechanism 13, and the indoor heat exchanger 12. In this indoor heat exchanger 12, the low-temperature and low-pressure refrigerant decompressed and expanded by the indoor expansion mechanism 13 evaporates by heat exchange with the air blown by the indoor fan, and cools the air passing through the indoor heat exchanger 12. Thereafter, the refrigerant sequentially flows through the indoor heat exchanger 12, the four-way valve 6, and the accumulator 9 and is again sucked into the compressor 4.

  In such an operation, the lubricating oil contained in the refrigerant gas discharged from the compressor 4 is separated from the refrigerant gas by the oil separator 5, but is not completely separated, and a small amount of lubricating oil is used as the gas refrigerant. At the same time, it circulates through the refrigeration cycle and returns to the compressor 4 again. For this reason, the amount of lubricating oil circulating in the refrigeration cycle increases depending on the installation status of the air conditioner 1, such as the installation distance between the outdoor unit 2 and the indoor unit 3 being separated or there is a difference in height, and the compressor 4 May cause a lack of lubricating oil.

  Assuming such a situation, in general, in an air conditioner, it is usual to increase the amount of lubricating oil filled in advance for safety. Therefore, when the installation condition of the air conditioner 1 is such that the installation distance between the outdoor unit 2 and the indoor unit 3 is close and there is no difference in height, the amount of lubricating oil enclosed in the refrigeration cycle becomes excessive, and the cylinder 24 compresses it. The refrigerant gas thus discharged is discharged from the cylinder discharge port 25 into the lubricating oil. In this case, the compressed refrigerant gas is diffused into the lubricating oil, resulting in a so-called forming state in which a large number of bubbles are generated. When oil forming occurs in the compressor 4, the amount of lubricating oil discharged from the compressor 4 increases, and more than expected lubricating oil flows into the oil separator 5, and the oil separator 5 exceeds a predetermined separation capacity and is separated. The ability will be reduced.

Next, operations of the first electromagnetic valve 17 and the second electromagnetic valve 19 in the present embodiment will be described with reference to FIG.
The refrigerant gas compressed by the compressor 4 flows into the oil separator 5 from the case discharge port 27 of the compressor 4 through the discharge pipe 14. Lubricating oil contained in the refrigerant gas is separated from the refrigerant gas by the oil separator 5 and stays in the lower part of the oil separator 5.

  When the first solenoid valve 17 is open and the second solenoid valve 19 is closed, the lubricating oil separated inside the oil separator 5 passes through the first oil return pipe 15 opened at the bottom of the oil separator 5. As a result, the refrigerant is refluxed to the suction side of the compressor 4. Here, the resistance value of the first flow path resistance 18 provided in the first oil return pipe 15 depends on the load conditions that the air conditioner 1 can use, the size of the air conditioner 1, and the capacity of the compressor 4. It is determined appropriately in advance. Since the first oil return pipe 15 is connected to the bottom surface of the oil separator 5, the lubricating oil separated by the oil separator 5 is returned to the compressor 4 without remaining in the oil separator 5. .

  When the first electromagnetic valve 17 is closed and the second electromagnetic valve 19 is opened, the lubricating oil separated by the oil separator 5 is a second oil return pipe whose liquid level is open on the side surface of the oil separator 5. The oil is stored in the lower part of the oil separator 5 until reaching the inlet 16. Then, after the stored lubricating oil reaches the inlet of the second oil return pipe 16, it passes through the second return pipe 16 and is returned to the upstream low-pressure pipe 22 of the accumulator 9. The resistance value of the second flow path resistance 20 provided in the second oil return pipe 16 is also determined in advance depending on the load conditions that the air conditioner 1 can use, the size of the air conditioner 1, the capacity of the compressor 4, and the like. Determined appropriately. Since one end of the second oil return pipe 16 is connected to the side surface of the oil separator 5, the lubricating oil separated by the oil separator 5 reaches the connection position of the second oil return pipe 16. Since the other end of the second oil return pipe 16 is connected to the upstream low-pressure pipe 22 of the accumulator 9, it is also stored inside the accumulator 9. The lubricating oil stored in the accumulator 9 is returned to the compressor 4 together with the refrigerant flowing through the suction side pipe 21 through a small hole (not shown) provided in the suction side pipe 21 communicating with the inside of the accumulator 9.

  The connection opening in the oil separator 5 of the second oil return pipe 16 only needs to be higher than the connection opening in the first oil separator 5. For example, the connection opening extends through the bottom surface of the oil separator 5 and the opening is The structure arrange | positioned inside the oil separator 5 may be sufficient. In addition, the position of the opening is appropriately set in advance depending on the ability of the air conditioner, the amount of lubricating oil enclosed, and the like.

  Next, the operation of the control device 23 that controls the opening and closing of the first solenoid valve 17 and the second solenoid valve 19 will be described with reference to the flowchart shown in FIG.

  When the operation of the air conditioner 1 is set by an operation panel (not shown), the control device 23 opens the first electromagnetic valve 17 and closes the second electromagnetic valve 19 (ST1), and drives the compressor 4. (ST2). Then, the control device 23 confirms whether or not the first electromagnetic valve 17 is opened and the second electromagnetic valve 19 is closed (ST3), the first electromagnetic valve 17 is opened, and the second electromagnetic valve 17 is opened. When the valve 19 is not closed (ST3: NO), the first electromagnetic valve 17 is opened and the second electromagnetic valve 19 is closed (ST4).

  Further, the control device 23 grasps the number of operating units n of the indoor units 3 set for operation, confirms the operating number n and a desired air-conditioning state (for example, the set temperature T) (ST5), and this operating number n And the operation rotation speed of the compressor 4 according to the desired set temperature T is set (ST6). In this case, since the compressor 4 is normally in a transient state in which a large cooling capacity is required for the air conditioner 1, a high rotational speed is required for the compressor 4. Further, when the compressor 4 is started, the refrigerant dissolved in the lubricating oil stored in the compressor 4 before starting is evaporated at a stroke, so that the lubricating oil is foamed to form a so-called forming state. A large amount of lubricating oil is discharged together with the refrigerant from inside 4. Therefore, the amount of lubricating oil required for the compressor 4 increases. In this case, in the present embodiment, the first solenoid valve 17 is opened and the second solenoid valve is closed, so that the lubricating oil separated in the oil separator 5 is opened at the bottom surface of the oil separator 5. The first oil return pipe 15 is passed through to the suction side of the compressor 4 so that the amount of lubricating oil is insufficient even when a large amount of lubricating oil is required when the compressor 4 is started. It becomes possible to prevent.

  Thereafter, the control device 23 stands by for a predetermined time (1), and again confirms the number of operating indoor units 3 and the set temperature T (ST8). When there is no change in the number n of operating indoor units 3 and the set temperature T (ST8: YES), the control device 23 determines that the state of the refrigeration cycle is stable, closes the first solenoid valve 17, The electromagnetic valve 19 is opened (ST9). On the other hand, when there is a change in the number n of the indoor units 3 or the set temperature T (ST8: NO), the initial state at the time of activation is restored. The predetermined time (1) referred to here is a time necessary for the refrigeration cycle to be stabilized, and is determined in advance through experiments or the like, and is, for example, 5 minutes.

  Further, after the first electromagnetic valve 17 is closed and the second electromagnetic valve 19 is opened, the control device 23 waits for a predetermined time (2) (ST10), during which the operation panels in all the rooms are turned off. If not (ST11: NO), it is checked again whether the number n of the indoor units 3 in operation and the set temperature T are changed (ST8). This predetermined time (2) is also determined in advance by experiments or the like, for example, 5 minutes. When the number of operating units n of the indoor units 3 and the set temperature T are changed (ST8: NO), the operation returns to the initial state again, and the number of operating units n of the indoor units 3 and the set temperature T are not changed. In this case (ST8: YES), the control of closing the first electromagnetic valve 17 and opening the second electromagnetic valve 19 is continued (ST9). In this embodiment, when surplus occurs in the lubricating oil in the refrigeration cycle, such as during refrigeration cycle stable operation, the first solenoid valve 17 is closed and the second solenoid valve 19 is opened. The lubricating oil separated by the oil separator 5 is returned to the low-pressure pipe 22 on the upstream side of the accumulator 9 through the second oil return pipe 16 having a liquid level opened to the side surface of the oil separator 5. Excess lubricating oil can be stored in the oil separator 5 and the accumulator 9, and the amount of lubricating oil circulating in the refrigeration cycle can be reduced without reducing the separation efficiency and increasing the size due to the reduction in the separation space of the oil separator 5. It is possible to keep it appropriate.

  Such control is continued until the operation of all the indoor units 3 is stopped, and when the operation panels in all the rooms are turned off (ST11: YES), the control device 23 stops the compressor 4. At the same time, the first electromagnetic valve 17 is opened and the second electromagnetic valve 19 is closed (ST12).

  As described above, the air conditioner 1 according to this embodiment includes the first oil return pipe connected to the suction side pipe between the suction port of the compressor 4 connected to the bottom surface of the oil separator 5 and the accumulator 9. 16, a second oil return pipe 17 connected to the side surface of the oil separator 5, connected to the low pressure side pipe 22 between the accumulator 9 and the four-way valve 6, and a first oil return pipe 15 provided on the first oil return pipe 15. 1 electromagnetic valve 17 and the first flow path resistance 18, the second electromagnetic valve 19 and the second flow path resistance 20 provided in the second oil return pipe 16, and the operating state of the refrigeration cycle. Since the control device 23 for controlling the opening and closing of the first electromagnetic valve 17 and the second electromagnetic valve 19 is provided, a large amount of lubricating oil is supplied to the compressor 4 when the air conditioner 1 is started or when the load fluctuates. If necessary, turn the first solenoid valve 17 , The second electromagnetic valve by the closing, it is possible to eliminate the shortage of lubricating oil of the compressor 4.

  In addition, when surplus lubricating oil is generated in the refrigeration cycle, such as during refrigeration cycle stable operation of the air conditioner 1, it is possible to store surplus lubricating oil in the oil separator 5 and the accumulator 9. It is possible to appropriately maintain the circulation amount of the lubricating oil circulating in the refrigeration cycle without causing a decrease in separation efficiency or an increase in size due to a reduction in the separation space of the oil separator 5.

  Moreover, in the air conditioning apparatus 1 in this embodiment, the amount of oil returned to the compressor 4 is adjusted with a simpler configuration by making the first flow path resistance 18 smaller than the second flow path resistance 20. It becomes possible to do.

  In the present embodiment, the number of operating units n of the indoor units 3 and the desired air conditioning state (for example, the set temperature T) have been described as an example of the index representing the operating state of the refrigeration cycle. Instead of T, the refrigerant pressure and temperature in the discharge pipe of the compressor 4, the refrigerant pressure in the suction pipe, the temperature, the outlet refrigerant temperature of the outdoor heat exchanger 7, the outlet refrigerant temperature of the indoor heat exchanger 12, etc. Sensors for determining the state of the above may be provided, and these may be used alone or in combination.

  In the present embodiment, the solenoid valves 17 and 19 and the channel resistances 18 and 20 are installed in the oil return pipes 15 and 16, but the opening degree can be adjusted instead of the solenoid valve and the channel resistance. A simple electronic expansion valve may be used.

  INDUSTRIAL APPLICABILITY The present invention can be used for an air conditioner having a compressor driven by an external drive source, and in particular, a multi-chamber air in which indoor / outdoor piping is long, there are height differences, and the oil level management of the compressor becomes difficult. It is suitably used as a harmony device.

DESCRIPTION OF SYMBOLS 1 Air conditioning apparatus 2 Outdoor unit 3 Indoor unit 4 Compressor 5 Oil separator 6 Four-way valve 7 Outdoor heat exchanger 8 Outdoor expansion mechanism 9 Accumulator 10 Refrigerant gas pipe 11 Refrigerant liquid pipe 12 Indoor heat exchanger 13 Indoor expansion mechanism 14 Compressor Discharge piping 15 1st oil return piping 16 2nd oil return piping 17 1st solenoid valve 18 1st flow path resistance 19 2nd solenoid valve 20 2nd flow path resistance 21 Compressor suction piping 22 Low pressure side Piping 23 Control device 24 Compressor cylinder 25 Compressor cylinder discharge port 26 Cyclone block

Claims (3)

In an air conditioner including a compressor driven by an external drive source, an oil separator, a four-way valve, an outdoor heat exchanger, an expansion mechanism, an indoor unit including an indoor heat exchanger, and a refrigeration cycle connected to an accumulator.
A first oil return pipe connected to a bottom surface of the oil separator and connected to a suction side pipe between the suction port of the compressor and the accumulator;
A second oil return pipe that opens to a higher oil level than the first oil return pipe of the oil separator and is connected to a low pressure side pipe between the accumulator and the four-way valve;
A first solenoid valve and a first flow path resistance provided in the first oil return pipe;
A second solenoid valve and a second flow path resistance provided in the second oil return pipe;
A controller that controls opening and closing of the first solenoid valve and the second solenoid valve based on an operating state of a refrigeration cycle,
The control device opens the first electromagnetic valve and closes the second electromagnetic valve for a predetermined time when the refrigeration cycle is started up and when the load fluctuates, and after the predetermined time has elapsed, the first electromagnetic valve is closed. Is closed, and the second electromagnetic valve is opened.   The air conditioner according to claim 1, wherein the first flow path resistance is smaller than the second flow path resistance.   The air conditioner according to claim 1 or 2, wherein the second oil return pipe is connected to a side surface of the oil separator.

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