JP6554903B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner.

  2. Description of the Related Art Conventionally, an air conditioner that includes a compressor, an outdoor heat exchanger, an expansion valve, an indoor heat exchanger, and an accumulator and performs air conditioning using a refrigerant condensing action and an evaporating action is known. During the cooling operation of such an air conditioner, the refrigerant discharged from the discharge port of the compressor flows through the outdoor heat exchanger, the expansion valve, the indoor heat exchanger, and the accumulator in this order, and then the suction of the compressor from the accumulator. The gas phase refrigerant is returned to the mouth. At this time, the refrigerant in the indoor heat exchanger exchanges heat with the indoor air, thereby cooling the room. On the other hand, during heating operation, the refrigerant discharged from the discharge port of the compressor flows through the indoor heat exchanger, the expansion valve, the outdoor heat exchanger, and the accumulator in this order, and then the gas phase is transferred from the accumulator to the suction port of the compressor. The refrigerant is returned. At this time, the interior of the room is heated by heat exchange between the refrigerant and the room air in the room heat exchanger.

In Patent Document 1, in addition to the above configuration, a gas-liquid separator provided between the outdoor heat exchanger and the expansion valve, and a gas-phase refrigerant separated by the gas-liquid separator at the suction port of the compressor are used. An air conditioner including a bypass passage for returning, a bypass opening / closing valve interposed in the bypass passage, and a control device for controlling the opening / closing operation of the bypass opening / closing valve is disclosed. According to the air conditioner described in Patent Document 1, the bypass is opened by the control device so that the bypass valve is opened when all of the following conditions are satisfied during cooling operation, and the bypass on-off valve is closed at other times. The opening / closing operation of the opening / closing valve is controlled.
・ Compressor speed (operating frequency) is higher than the specified high speed ・ Outside air temperature is higher than the set value ・ Indoor temperature is equal to or higher than the set temperature ・ Indoor fan motor speed is More than the set rotation speed

  In the air conditioner described in Patent Literature 1, when all of the above conditions are satisfied and the bypass on-off valve is opened, the gas-phase refrigerant separated by the gas-liquid separator is returned to the compressor through the bypass passage. For this reason, the gaseous-phase refrigerant | coolant which flowed out the outdoor heat exchanger bypasses an expansion valve, an indoor heat exchanger, and an accumulator. Therefore, no pressure loss occurs when the refrigerant passes through them. As a result, it is possible to increase the refrigeration efficiency during the cooling operation.

JP 2010-96479 A

(Problems to be solved by the invention)
By the way, with the progress of recent building technology, the heat insulation of buildings is also progressing. Accordingly, the difference between the temperature and the temperature inside the room is becoming smaller, and accordingly, the air conditioning load at the time of indoor air conditioning is also becoming smaller. When the air conditioning load is small, the rotational speed of the compressor provided in the air conditioner is lowered. That is, in the current indoor air conditioning of buildings, in most cases, the compressor operates at a low rotational speed.

  According to the control described in Patent Document 1, the condition for opening the bypass on-off valve includes a condition that the rotational speed (operation frequency) of the compressor is equal to or higher than a predetermined high rotational speed. This means that when the rotational speed of the compressor is less than a predetermined high rotational speed, that is, when the rotational speed of the compressor is low, the bypass on-off valve is closed. Here, as described above, in the indoor air conditioning of the current building, in most cases, the rotational speed of the compressor is low. Therefore, when the opening / closing of the bypass on / off valve is controlled by the control method described in Patent Document 1, in most cases, the bypass on / off valve is closed. Therefore, the refrigeration efficiency during the cooling operation cannot be sufficiently increased.

  An object of this invention is to provide the air conditioning apparatus comprised so that the refrigerating efficiency at the time of air_conditionaing | cooling operation could be improved further.

(Means for solving the problem)
The present invention includes a compressor (11) that includes a suction port (11a) and a discharge port (11b), sucks refrigerant from the suction port, compresses the sucked refrigerant, and discharges the compressed refrigerant from the discharge port, and refrigerant An outdoor heat exchanger (14) for exchanging heat with the outside air, an expansion valve (21) for expanding the refrigerant, and a plurality of indoor heat exchangers (22) for exchanging heat between the refrigerant and the indoor air An accumulator (18) for gas-liquid separation of the refrigerant, and a refrigerant discharged from the discharge port of the compressor during the cooling operation, in this order, an outdoor heat exchanger, an expansion valve, a plurality of indoor heat exchangers, and an accumulator The refrigerant passage (30) connecting the compressor, the outdoor heat exchanger, the expansion valve, the plurality of indoor heat exchangers, and the accumulator so as to return to the suction port of the compressor after flowing, and the discharge port of the compressor The first port (13a) connected to And a second port (13b) connected to the indoor heat exchanger, a third port (13c) connected to the outdoor heat exchanger, and a fourth port (13d) connected to the accumulator, A four-way valve (13) that is controlled so that the first port and the third port communicate with each other during the cooling operation and the second port and the fourth port communicate with each other, and a plurality of indoor heat exchangers in the refrigerant passage during the cooling operation. Are also downstream and upstream of the four-way valve , the bypass passage (38) for guiding the refrigerant to the compressor inlet and the bypass passage, and opening the refrigerant in the bypass passage A bypass on-off valve (61) configured to permit the circulation of the refrigerant and prohibit the circulation of the refrigerant in the bypass passage by closing, and a control device (40) for controlling the opening / closing operation of the bypass on-off valve, System The lower limit rotational speed (R1) of the compressor based on the total operating capacity is determined so that the apparatus becomes lower as the total operating capacity of the operating indoor heat exchanger among the plurality of indoor heat exchangers becomes smaller during the cooling operation. When the lower limit rotational speed setting process (S4) and the actual rotational speed (R) of the compressor during the cooling operation are equal to or higher than the lower limit rotational speed, the bypass on-off valve is opened, and the actual rotational speed of the compressor during the cooling operation is the lower limit. Provided is an air conditioner (1) that performs an on / off valve control process (S6, S8, S9) for controlling an on / off operation of the bypass on / off valve so that the bypass on / off valve is closed when the rotational speed is lower than the rotational speed. .

  In this case, the lower limit rotational speed setting process is performed so that when the compressor is operated at a rotational speed that is equal to or higher than the set lower limit rotational speed, liquid refrigerant is not included in the refrigerant sucked into the suction port of the compressor. It is preferable that the lower limit rotational speed be determined based on the operating capacity.

  According to the air conditioner of the present invention, when the bypass on-off valve is open during the cooling operation, the refrigerant that has flowed out of the indoor heat exchanger is returned to the compressor inlet via the bypass passage. The refrigerant flowing through the bypass passage bypasses at least the accumulator. For this reason, pressure loss due to the refrigerant passing through the accumulator does not occur. Thus, the pressure loss corresponding to the passage through the accumulator is reduced, so that the refrigeration efficiency during the cooling operation is increased.

  Here, since the refrigerant flowing through the bypass passage bypasses the accumulator, if the refrigerant in the bypass passage contains liquid refrigerant, the liquid refrigerant is sucked into the suction port of the compressor. When the liquid refrigerant is sucked into the compressor, it is not preferable because the compressor compresses the liquid refrigerant. In this regard, in the present invention, when the bypass on-off valve is open, the actual rotational speed of the compressor is always greater than or equal to the lower limit rotational speed determined based on the total operating capacity of the operating indoor heat exchanger. Yes, the lower limit rotational speed is the indoor heat exchange during operation so that the refrigerant sucked into the compressor inlet does not contain liquid refrigerant when the compressor is operated at a rotational speed higher than the lower limit rotational speed. Determined based on the total operating capacity of the vessel. Therefore, even when the bypass on-off valve is open, the liquid refrigerant is not sucked into the compressor, and therefore the compressor does not compress the liquid refrigerant.

  Furthermore, the lower limit rotational speed of the compressor that affects the opening / closing operation of the bypass opening / closing valve is determined based on the total operating capacity of the operating indoor heat exchanger so as to decrease as the total operating capacity decreases. According to this, at the time of low load operation with a small total operating capacity, the rotational speed of the compressor is relatively reduced. At this time, the lower limit rotational speed of the compressor is also reduced in the present invention. That is, the lower limit rotational speed of the compressor varies depending on the load. Therefore, during low load operation, the lower limit of the rotational speed region of the compressor that may open the bypass on-off valve is lowered. Therefore, even during low-load operation, the bypass on-off valve can be opened so that the gas refrigerant flowing out of the indoor heat exchanger bypasses the accumulator. Therefore, the refrigeration efficiency during the cooling operation can be improved by returning the gas refrigerant flowing out of the indoor heat exchanger directly to the compressor without passing through the accumulator even during the low load operation.

Moreover, bypass passage is configured during the cooling operation, the refrigerant flowing through the upstream portion than the four-way valve and a downstream side of the indoor heat exchanger of the refrigerant passage, so as to guide the suction port of the compressor Ru is. According to this, when the bypass opening / closing valve is open, the refrigerant flowing out of the indoor heat exchanger bypasses the four-way valve and the accumulator and flows into the suction port of the compressor. For this reason, pressure loss due to the refrigerant passing through the four-way valve and the accumulator does not occur. Thus, since the pressure loss due to passing through the four-way valve and the accumulator is reduced, the refrigeration efficiency during the cooling operation is further enhanced.

  In addition, the control device controls the bypass on / off valve so that the bypass on / off valve is closed when oil return control is performed to return the oil sleeping in the indoor heat exchanger to the compressor during cooling operation. Good. According to this, when the oil return control is executed, the liquid refrigerant together with the oil is prevented from flowing into the compressor suction port via the bypass passage.

  Further, the control device closes the bypass on / off valve before a predetermined time elapses from the start of the cooling operation by the air conditioner until the operation of the air conditioner becomes stable. The bypass on-off valve may be controlled. Immediately after starting the air conditioner, the operating state of the air conditioner is unstable. If the bypass on-off valve is opened during an unstable operation state, liquid refrigerant may flow in the bypass passage. In this regard, in the present invention, the bypass on-off valve is closed after the start of the cooling operation of the air conditioner and before a predetermined time has elapsed. Therefore, it is possible to effectively prevent the liquid refrigerant from being supplied to the compressor via the bypass passage at the beginning of the start.

It is a figure which shows schematic structure of the air conditioning apparatus which concerns on this embodiment. It is a figure which shows the internal structure of an outdoor unit and an indoor unit. It is a flowchart which shows the flow of the on-off valve control processing routine performed in order that a control apparatus may control opening and closing of a bypass on-off valve. It is a flowchart which shows an example of the flow of the minimum rotational speed calculating process which a control apparatus performs.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a schematic configuration of an air-conditioning apparatus according to the present embodiment. As shown in FIG. 1, the air conditioning apparatus 1 according to the present embodiment includes an outdoor unit 10, a plurality of indoor units 20a, 20b, 20c, and 20d, and a refrigerant pipe 30 (refrigerant passage). The outdoor unit 10 and the plurality of indoor units 20a, 20b, 20c, and 20d are connected in parallel by the refrigerant pipe 30.

  FIG. 2 is a diagram illustrating an internal configuration of the outdoor unit 10 provided in the air conditioning apparatus 1 and an internal configuration of the indoor units 20a, 20b, 20c, and 20d. FIG. 2 shows the internal configuration of only the indoor unit 20a among the plurality of indoor units, but the internal configuration of all the indoor units is the same.

  As shown in FIG. 2, the outdoor unit 10 includes a compressor 11, an oil separator 12, a four-way valve 13, an outdoor heat exchanger 14, an outdoor electronic expansion valve 15, a sub heat exchanger 16, A cooling coil 17 and an accumulator 18 are provided. Each of the indoor units 20a, 20b, 20c, and 20d includes an indoor electronic expansion valve 21 and an indoor heat exchanger 22. These components are connected by a first pipe 31, a second pipe 32, a third pipe 33, an intermediate pipe 34, an accumulator inlet pipe 35, and an accumulator outlet pipe 36. The first pipe 31, the second pipe 32, the third pipe 33, the intermediate pipe 34, the accumulator inlet pipe 35, and the accumulator outlet pipe 36 constitute a refrigerant pipe 30 (refrigerant passage).

  The compressor 11 is connected to a power source such as a gas engine, for example, and rotates by receiving a driving force from the power source. The compressor 11 has a suction port 11a and a discharge port 11b. The compressor 11 sucks the refrigerant gas from the suction port 11a, compresses the refrigerant gas therein, and discharges the compressed refrigerant gas from the discharge port 11b. FIG. 2 shows an example in which two compressors 11 and 11 are connected in parallel. However, the number of compressors may be one or three or more. A plurality of compressors may be connected in series.

  The discharge port 11 b of the compressor 11 is connected to one end of the first pipe 31. The oil separator 12 is interposed in the middle of the first pipe 31. The oil separator 12 collects the oil discharged from the discharge port 11 b of the compressor 11. The recovered oil is returned to the suction port 11 a side of the compressor 11.

  The four-way valve 13 is connected to the other end of the first pipe 31. The four-way valve 13 has a first port 13a, a second port 13b, a third port 13c, and a fourth port 13d. The first port 13 a of the four-way valve 13 is connected to the discharge port 11 b of the compressor 11 via the first pipe 31. The second port 13 b of the four-way valve 13 is connected to each indoor heat exchanger 22 provided in the plurality of indoor units via the second pipe 32. The third port 13 c of the four-way valve 13 is connected to the outdoor heat exchanger 14 via the third pipe 33. The fourth port 13 d of the four-way valve 13 is connected to the accumulator 18 via the accumulator inlet pipe 35.

  The four-way valve 13 has a switching state during heating in which the first port 13a communicates with the second port 13b and the third port 13c communicates with the fourth port 13d, and the first port 13a communicates with the third port 13c. The cooling switching state in which the two ports 13b communicate with the fourth port 13d can be selectively realized.

  The outdoor heat exchanger 14 connected to the third port 13c of the four-way valve 13 through the third pipe 33 exchanges heat between the refrigerant circulating in the interior and the outside air. One end of an intermediate pipe 34 is connected to the outdoor heat exchanger 14. The other end of the intermediate pipe 34 is connected to the indoor heat exchanger 22 provided in each of the plurality of indoor units. The indoor heat exchanger 22 exchanges heat between the refrigerant circulating in the interior and the room air.

  The supercooling coil 17 is interposed in a portion in the middle of the intermediate pipe 34 and disposed on the outdoor unit 10 side. The supercooling coil 17 supercools the refrigerant passing through the inside. Further, a portion between the position A and the position B of the intermediate pipe 34 is branched into two pipes (a pipe L1 and a pipe L2). A one-way valve 19 is interposed in the pipe L1, and an outdoor electronic expansion valve 15 is interposed in the pipe L2. During the cooling operation, the refrigerant flows through the pipe L1, and during the heating operation, the refrigerant flows through the pipe L2. The outdoor electronic expansion valve 15 interposed in the pipe L2 expands the refrigerant flowing therethrough. The outdoor electronic expansion valve 15 is also a flow rate adjusting valve whose opening degree can be adjusted, and can adjust the flow rate of the refrigerant flowing through the pipe L2.

  The indoor-side electronic expansion valve 21 is interposed in a portion in the middle of the intermediate pipe 34 and disposed in the indoor units 20a, 20b, 20c, and 20d. The indoor electronic expansion valve 21 expands the refrigerant flowing therethrough. The indoor electronic expansion valve 21 is a flow rate adjustment valve whose opening degree can be adjusted. The indoor side electronic expansion valves 21 provided in the respective indoor units can be individually operated. Therefore, when the operation of an indoor unit is stopped, the indoor electronic expansion valve 21 of the indoor unit is closed so that the refrigerant does not flow into the indoor heat exchanger 22 of the indoor unit.

  Further, as described above, each of the plurality of indoor heat exchangers 22 is connected to the second port 13 b of the four-way valve 13 through the second pipe 32. Therefore, the refrigerant that has flowed out from the indoor heat exchanger 22 to the second pipe 32 side flows into the second port of the four-way valve 13 through the second pipe 32.

  The accumulator 18 connected to the fourth port 13d of the four-way valve 13 via the accumulator inlet pipe 35 is further connected to the suction port 11a of the compressor 11 via the accumulator outlet pipe 36. The accumulator 18 introduces a refrigerant from the accumulator inlet pipe 35 side, and gas-liquid separates the introduced refrigerant. The gas refrigerant separated in the accumulator 18 is returned to the suction port 11a of the compressor 11 via the accumulator outlet pipe 36.

  The accumulator inlet pipe 35 and the intermediate pipe 34 are connected by a branch pipe 37. The sub heat exchanger 16 is interposed in the branch pipe 37. The refrigerant flowing through the branch pipe 37 enters the sub heat exchanger 16, and in the sub heat exchanger 16, for example, heat exchange is performed with cooling water that has cooled a gas engine that is a power source of the compressor 11.

  The second pipe 32 and the accumulator outlet pipe 36 are connected by a bypass pipe 38 (bypass passage). A bypass opening / closing valve 61 is interposed in the bypass pipe 38. Further, the first pipe 31 and the accumulator inlet pipe 35 are connected by a hot gas bypass pipe 39. A hot gas bypass opening / closing valve 62 is interposed in the hot gas bypass pipe 39.

  In addition, the air conditioning apparatus 1 according to the present embodiment includes a control device 40. The control device 40 is mainly composed of a microcomputer including a CPU, a ROM, a RAM, and the like. The control device 40 controls at least the driving of the compressor 11, the switching operation of the four-way valve 13, the opening / closing operation of the bypass opening / closing valve 61, and the opening / closing operation of the hot gas bypass opening / closing valve 62.

  In addition, temperature sensors and pressure sensors are attached to various parts of the refrigerant circuit. Among these various sensors, the discharge temperature sensor 51 is attached to the first pipe 31 and detects the temperature (discharge temperature) of the refrigerant discharged from the compressor 11. The suction temperature sensor 52 is attached to the accumulator outlet pipe 36 and detects the temperature (suction temperature) of the refrigerant sucked into the compressor 11. The suction pressure sensor 53 is attached to the accumulator outlet pipe 36, and the pressure in the accumulator outlet pipe 36 leading to the suction port 11 a of the compressor 11, that is, the refrigerant pressure (suction pressure) on the suction port 11 a side of the compressor 11. Detect PL. Moreover, the outside temperature sensor 54 is attached to the housing of the outdoor unit, and detects the outside temperature Tout. Although not shown, a rotation speed sensor is attached to the compressor 11. This rotational speed sensor detects the actual rotational speed (the number of revolutions per unit time) R of the compressor 11. The temperature information, pressure information, and rotation speed information detected by each sensor are input to the control device 40.

  Next, the air conditioning operation of the air conditioning apparatus 1 having the above configuration will be described. The air conditioning apparatus 1 according to the present embodiment is configured such that the user can set whether the air conditioning mode is the heating mode or the cooling mode by operating a remote controller or the like. Then, the outdoor unit 10 performs air conditioning operation according to the set air conditioning mode.

  When the air conditioning mode of the air conditioner 1 is the heating mode, that is, during the heating operation, the control device 40 controls the switching operation of the four-way valve 13 so that the switching state of the four-way valve 13 becomes the switching state during heating. When the air conditioning mode of the air conditioner 1 is the cooling mode, that is, during the cooling operation, the control device 40 controls the switching operation of the four-way valve 13 so that the switching state of the four-way valve 13 becomes the switching state during cooling. In FIG. 2, the refrigerant flow during the cooling operation is indicated by a solid line arrow, and the refrigerant flow during the heating operation is indicated by a broken line arrow.

  First, the heating operation will be described. When the compressor 11 is operated by driving a power source such as a gas engine, the compressor 11 sucks the low-pressure gas refrigerant in the accumulator outlet pipe 36 from the suction port 11a and compresses the sucked low-pressure gas refrigerant to generate a high-temperature high-pressure gas. Generate refrigerant. Then, the generated high-temperature and high-pressure gas refrigerant is discharged from the discharge port 11b. The high-temperature high-pressure gas refrigerant discharged from the discharge port 11b flows through the first pipe 31.

  The oil that has flowed from the compressor 11 to the first pipe 31 is collected by the oil separator 12 interposed in the middle of the first pipe 31. The recovered oil is returned to the compressor 11. Further, a hot gas bypass pipe 39 is connected in the middle of the first pipe 31. The hot gas bypass on / off valve 62 interposed in the hot gas bypass pipe 39 is opened by the control device 40 so that, for example, the refrigerant pressure in the refrigerant circuit is too high during the operation of the air conditioner 1. The opening / closing operation is controlled. When the hot gas bypass opening / closing valve 62 is open, a part of the gas refrigerant in the first pipe 31 flows through the hot gas bypass pipe 39 to the accumulator inlet pipe 35 and is further introduced into the accumulator 18 from the accumulator inlet pipe 35. The When the hot gas bypass on / off valve 62 is closed, the gas refrigerant in the first pipe 31 enters the first port 13 a of the four-way valve 13.

  Since the switching operation of the four-way valve 13 is controlled by the control device 40 so as to be in the heating switching state during the heating operation, the first port 13a of the four-way valve 13 communicates with the second port 13b during the heating operation. . Therefore, the high-temperature and high-pressure gas refrigerant that has entered the first port 13 a of the four-way valve 13 from the first pipe 31 flows out of the second port 13 b and flows into the second pipe 32.

  A bypass pipe 38 is connected in the middle of the second pipe 32. The opening / closing operation of the bypass opening / closing valve 61 interposed in the bypass pipe 38 is controlled by the control device 40 so as to be closed during the heating operation. Therefore, during the heating operation, the refrigerant in the second pipe 32 flows into the indoor heat exchanger 22 on the indoor unit side without flowing through the bypass pipe 38. The high-temperature and high-pressure gas refrigerant that has flowed into the indoor heat exchanger 22 exchanges heat with the indoor air while flowing through the indoor heat exchanger 22, and discharges heat into the room to condense. That is, the indoor heat exchanger 22 functions as a condenser during heating operation. At this time, the room air is warmed by the heat discharged from the high-temperature and high-pressure gas refrigerant, and the room is heated.

  The refrigerant that is condensed by discharging heat to the room air partially liquefies and flows out from the indoor heat exchanger 22 to the intermediate pipe 34. And it expands in the indoor electronic expansion valve 21 interposed in the middle of the intermediate piping 34, and is made into intermediate pressure. Then, it supercools by passing the supercooling coil 17 by the side of an outdoor unit. A part of the refrigerant that has flowed out of the supercooling coil 17 flows through the branch pipe 37 connected to the intermediate pipe 34. And it enters into the sub heat exchanger 16 provided in the branch piping 37, and heat exchange with engine cooling water is carried out by this sub heat exchanger 16, for example. The refrigerant that has exchanged heat with the sub heat exchanger 16 flows through the accumulator inlet pipe 35 from the branch pipe 37 and is introduced into the accumulator 18.

  On the other hand, the refrigerant that has not flowed from the intermediate pipe 34 to the branch pipe 37 flows through the pipe L2 and passes through the outdoor electronic expansion valve 15 interposed in the pipe L2. The refrigerant is reduced in pressure by passing through the outdoor electronic expansion valve 15. The refrigerant that has passed through the outdoor electronic expansion valve 15 flows into the outdoor heat exchanger 14. The refrigerant that has flowed into the outdoor heat exchanger 14 exchanges heat with the outside air while flowing through the outdoor heat exchanger 14 and evaporates by taking heat from the outside air. That is, the outdoor heat exchanger 14 functions as an evaporator during heating operation.

  The refrigerant evaporated by taking the heat of the outside air partially vaporizes and flows out from the outdoor heat exchanger 14 to the third pipe 33, and then enters the third port 13 c of the four-way valve 13. During the heating operation, since the third port 13c of the four-way valve 13 communicates with the fourth port 13d, the refrigerant that has entered the third port 13c of the four-way valve 13 from the third pipe 33 is transferred from the fourth port 13d to the four-way valve 13d. And flows through the accumulator inlet pipe 35. The refrigerant that has flowed through the accumulator inlet pipe 35 is introduced into the accumulator 18. In the accumulator 18, the introduced refrigerant is gas-liquid separated, and the gas-liquid separated low-temperature and low-pressure gas refrigerant flows out to the accumulator outlet pipe 36. Then, the gas refrigerant in the accumulator outlet pipe 36 is returned to the suction port 11 a of the compressor 11. By repeating such a refrigerant circulation cycle, room heating is continued.

  Next, the cooling operation will be described. When the compressor 11 is operated, the high-temperature and high-pressure gas refrigerant is discharged from the discharge port 11 b of the compressor 11 to the first pipe 31. The high-temperature and high-pressure gas refrigerant flows through the first pipe 31 and enters the first port 13 a of the four-way valve 13 via the oil separator 12.

  Since the switching operation of the four-way valve 13 is controlled by the control device 40 so as to be switched during cooling operation, the first port 13a of the four-way valve 13 communicates with the third port 13c during cooling operation. . Therefore, the high-temperature high-pressure gas refrigerant that has entered the first port 13a of the four-way valve 13 from the first pipe 31 flows out of the four-way valve 13 from the third port 13c and flows into the third pipe 33. The high-temperature high-pressure gas refrigerant that has flowed into the third pipe 33 flows into the outdoor heat exchanger 14. The refrigerant that has flowed into the outdoor heat exchanger 14 exchanges heat with the outside air while circulating in the outdoor heat exchanger 14, and heat is discharged to the outside air to condense. That is, the outdoor heat exchanger 14 functions as a condenser during the cooling operation.

  The refrigerant that is condensed by discharging heat to the outside air is partially liquefied and flows out from the outdoor heat exchanger 14 to the intermediate pipe 34. The liquid refrigerant (or gas-liquid two-phase refrigerant) that has flowed out to the intermediate pipe 34 passes through the pipe L1. Thereafter, a part of the refrigerant flows through the branch pipe 37 and exchanges heat with the sub heat exchanger 16 provided in the branch pipe 37. The refrigerant that has exchanged heat with the sub heat exchanger 16 flows through the accumulator inlet pipe 35 from the branch pipe 37 and is introduced into the accumulator 18.

  The refrigerant that did not flow through the branch pipe 37 passes through the supercooling coil 17 interposed in the intermediate pipe 34, and then passes through the indoor electronic expansion valve 21 on the indoor unit side. The pressure is reduced so that the refrigerant expands easily by the indoor electronic expansion valve 21 and is easily evaporated. Thereafter, the refrigerant flows into the indoor heat exchanger 22. The refrigerant that has flowed into the indoor heat exchanger 22 exchanges heat with the indoor air while flowing through the indoor heat exchanger 22, and takes the heat of the indoor air to evaporate. That is, the indoor heat exchanger 22 functions as an evaporator during the cooling operation. At this time, the refrigerant removes heat from the room air, thereby cooling the room air and cooling the room.

  The refrigerant that has evaporated the heat of the room air partially vaporizes and flows out from the indoor heat exchanger 22 to the second pipe 32. Here, as described above, the second pipe 32 is connected to the accumulator outlet pipe 36 by the bypass pipe 38. A bypass opening / closing valve 61 is interposed in the bypass pipe 38. The bypass opening / closing valve 61 is closed during heating operation, but is opened during cooling operation when a predetermined condition described later is satisfied. When the bypass opening / closing valve 61 is open, the refrigerant in the second pipe 32 flows into the accumulator outlet pipe 36 via the bypass pipe 38. On the other hand, when the bypass opening / closing valve 61 is closed, the refrigerant in the second pipe 32 goes to the four-way valve 13 without passing through the bypass pipe 38. Then, it enters the second port 13b of the four-way valve 13. Since the second port 13b of the four-way valve 13 communicates with the fourth port 13d during the cooling operation, the refrigerant that has entered the second port 13b of the four-way valve 13 from the second pipe 32 passes through the four-way valve 13 from the fourth port 13d. And flows into the accumulator inlet pipe 35. The refrigerant that has flowed through the accumulator inlet pipe 35 is introduced into the accumulator 18. In the accumulator 18, the introduced refrigerant is separated into gas and liquid, and the separated low-temperature and low-pressure gas refrigerant flows out to the accumulator outlet pipe 36. The gas refrigerant that has flowed from the accumulator 18 into the accumulator outlet pipe 36 and the gas refrigerant that has flowed into the accumulator outlet pipe 36 via the bypass pipe 38 are returned to the suction port 11 a of the compressor 11. By repeating such a refrigerant circulation cycle, room cooling is continued.

  As can be seen from the above description, during the cooling operation, the refrigerant discharged from the discharge port 11b of the compressor 11 is condensed by flowing through the outdoor heat exchanger 14, and then flows through the indoor electronic expansion valve 21. The liquid is expanded and then evaporated by flowing through the indoor heat exchangers 22 provided in the plurality of indoor units 20a, 20b, 20c, and 20d, and then introduced into the accumulator 18 for gas-liquid separation. The compressor 11, the outdoor heat exchanger 14, the indoor electronic expansion valve 21, the plurality of indoor heat exchangers 22, and the accumulator 18 are disposed so that the separated gas-phase refrigerant is returned to the suction port 11 a of the compressor 11. The refrigerant pipes 30 are connected in this order.

  Moreover, the indoor heat exchanger 22 provided in each of the plurality of indoor units 20a, 20b, 20c, and 20d operates independently. Therefore, for example, when the air conditioner 1 is in the cooling operation, if the difference between the set temperature of the space to be cooled and the actual temperature is small, the indoor heat exchanger 22 installed in the space is stopped. The refrigerant does not flow into the stopped indoor heat exchanger 22. On the other hand, when the difference between the set temperature of the space to be cooled and the actual temperature is large, the indoor heat exchanger 22 installed in the space is operating. The refrigerant flows into the operating indoor heat exchanger 22.

  The air conditioner 1 according to this embodiment includes a bypass pipe 38 and a bypass opening / closing valve 61. The bypass pipe 38 is a refrigerant that flows downstream of the plurality of indoor heat exchangers 22 and upstream of the four-way valve 13 and the accumulator 18 in the refrigerant pipe 30 during the cooling operation, that is, during the cooling operation. The refrigerant in the second pipe 32 through which the refrigerant flowing out from the indoor heat exchanger 22 flows is guided to the suction port 11a of the compressor 11. Further, the bypass on-off valve 61 is interposed in the bypass pipe 38, and is configured to permit the circulation of the refrigerant in the bypass pipe 38 by being opened, and prohibit the circulation of the refrigerant in the bypass pipe 38 by being closed. The

  In the present embodiment, the bypass on-off valve 61 is opened during the cooling operation and when a predetermined condition is satisfied. When the bypass on-off valve 61 is open, the refrigerant flowing out of the operating indoor heat exchanger 22 (evaporator) and flowing through the second pipe 32 flows through the bypass pipe 38, thereby bypassing the four-way valve 13 and the accumulator 18. To do. In this way, the refrigerant bypasses the four-way valve 13 and the accumulator 18, thereby preventing the occurrence of pressure loss when passing through these components. By reducing the pressure loss in this way, the refrigeration efficiency of the air conditioner 1 can be increased.

  When the bypass on-off valve 61 is open during the cooling operation, the refrigerant flows through the bypass pipe 38 as described above. However, if liquid refrigerant is contained in the refrigerant flowing through the bypass pipe 38, the refrigerant enters the inlet 11 a of the compressor 11. Liquid refrigerant flows in. When the liquid refrigerant flows into the compressor 11, the suction superheat degree of the refrigerant decreases, and the compressor 11 compresses the liquid refrigerant. When the compressor 11 compresses the liquid refrigerant, the operation of the compressor 11 may be hindered. In order to prevent the occurrence of such problems, in the air conditioning apparatus 1 according to the present embodiment, when the bypass on-off valve 61 is open, the refrigerant sucked into the compressor 11 does not contain liquid refrigerant. As described above, the opening / closing operation of the bypass opening / closing valve 61 is controlled by the control device 40.

  FIG. 3 is a flowchart showing the flow of a control processing routine executed by the control device 40 to control the opening / closing operation of the bypass opening / closing valve 61. This routine is started when the air conditioner 1 is started, and is repeatedly executed every predetermined short time.

  When this routine is started, the control device 40 first determines whether or not the air conditioner 1 is in a cooling operation in step 1 (hereinafter, step number is abbreviated as S) 1 in FIG. When the air conditioning apparatus 1 is not in the cooling operation (S1: No), the control device 40 advances the process to S9 and sends a closing operation signal to the bypass opening / closing valve 61. Thereby, the bypass on-off valve 61 is closed. Further, when the bypass opening / closing valve 61 is already closed, the state is maintained. Thereafter, the control device 40 ends this routine.

  On the other hand, if it is determined in S1 that the air conditioner 1 is in the cooling operation (S1: Yes), the control device 40 has passed 15 minutes since the start of the air conditioner 1 is completed in S2. Judge whether or not. When 15 minutes have not elapsed since the start of the air conditioner 1 has been completed (S2: No), the control device 40 proceeds to S9 and sends a closing operation signal to the bypass opening / closing valve 61. Thereby, the bypass on-off valve 61 is closed. Further, when the bypass opening / closing valve 61 is already closed, the state is maintained. Thereafter, the control device 40 ends this routine.

  On the other hand, if it is determined in S2 that 15 minutes have elapsed since the start of the air conditioner 1 is completed (S2: Yes), the controller 40 determines whether or not the oil return process is currently being performed in S3. Determine whether. When it is determined that the oil return process is being performed (S3: No), the control device 40 advances the process to S9 and sends a closing operation signal to the bypass on-off valve 61. Thereby, the bypass on-off valve 61 is closed. Further, when the bypass opening / closing valve 61 is already closed, the state is maintained. Here, the oil return process is a process of flowing the refrigerant in the refrigerant circuit so that the oil staying in each indoor heat exchanger 22 (sleeping) is returned to the compressor 11 during the cooling operation. is there. This oil return process is periodically performed at predetermined time intervals (for example, every 10 hours). When the oil return process is executed, the refrigerant is caused to flow through all the indoor heat exchangers 22. If the bypass opening / closing valve 61 is open during the oil return process, the liquid refrigerant flows into the suction port 11a of the compressor 11 together with the oil, which is not preferable. Therefore, during the oil return process, the opening / closing operation of the bypass opening / closing valve 61 is controlled by the control device 40 so that the bypass opening / closing valve 61 is closed. Thereafter, the control device 40 ends this routine.

  When it is determined that the oil return process is not being performed in S3 (S3: Yes), the control device 40 calculates the lower limit rotation speed R1 in S4. Here, the meaning of the lower limit rotation speed R1 will be described. When the rotation speed of the compressor 11 is low, the suction pressure PL, which is the pressure of the refrigerant sucked into the suction port 11a of the compressor 11, increases, and the refrigerant is liable to be liquefied. For this reason, when the rotational speed of the compressor 11 is low, liquid refrigerant may be contained in the refrigerant sucked into the compressor 11. That is, if the bypass on-off valve 61 is open while the rotational speed of the compressor 11 is low, the refrigerant in the bypass pipe 38 may contain liquid refrigerant. And when the compressor 11 compresses a liquid refrigerant, there exists a possibility that the compressor 11 may cause a malfunction. The lower limit rotation speed R1 is a lower limit value of the rotation speed of the compressor 11 so that such a situation (liquid compression of the compressor 11) does not occur.

  In order to avoid the liquid compression of the compressor 11, it is necessary to promote the evaporation of the refrigerant in the indoor heat exchanger 22. Therefore, the lower limit rotational speed R1 is such that the refrigerant that is sufficiently evaporated in the indoor heat exchanger 22 to the extent that the liquid compression of the compressor 11 is avoided and the refrigerant sucked into the compressor 11 is not included in the liquid refrigerant. It can also be said that the lower limit value of the rotational speed of the compressor 11. Such a lower limit rotational speed R1 depends on the operating capacity of the indoor heat exchanger 22. Specifically, the lower limit rotational speed R1 is increased as the operating capacity of the indoor heat exchanger 22 is increased, and is decreased as the operating capacity of the indoor heat exchanger 22 is decreased. In addition, the operating capacity of each indoor heat exchanger 22 is a fixed value (for example, 14 kW). In the present embodiment, the air conditioner 1 includes a plurality of indoor heat exchangers 22. In this case, the lower limit rotational speed R1 depends on the total operating capacity P that is the sum of the operating capacities of the indoor heat exchanger 22 during the cooling operation. The total operation capacity P varies depending on the number of indoor heat exchangers 22 in the cooling operation and the size of the operation capacity of the indoor heat exchanger 22 in the cooling operation. The lower limit rotational speed R1 is increased as the total operating capacity P is increased, and is decreased as the total operating capacity P is decreased.

  FIG. 4 is a flowchart illustrating an example of a flow of a lower limit rotation speed calculation process (lower limit rotation speed setting process) executed by the control device 40 in order to calculate the lower limit rotation speed R1 in S4. According to FIG. 4, when calculating the lower limit rotational speed R1, the control device 40 first detects the indoor heat exchanger 22 during the cooling operation in S41 of FIG. Next, the total operating capacity P of the indoor heat exchanger 22 during the cooling operation is calculated (S42). Then, the lower limit rotational speed R1 is calculated on the basis of the total operating capacity P so as to increase as the total operating capacity P increases and decrease as the total operating capacity P decreases (S43).

  According to the above-described lower limit rotation speed calculation process, for example, the operating capacity of each indoor heat exchanger 22 provided in each of the indoor units 20a, 20b, and 20c is 14 kW, and the indoor heat exchanger 22 provided in the indoor unit 20d It is assumed that the operating capacity is 28 kW. Further, it is assumed that the indoor heat exchanger 22 provided in the indoor units 20a, 20b, and 20d is in the cooling operation, and the indoor heat exchanger 22 provided in the indoor unit 20c is stopped. In this case, the total operating capacity P is 14 + 14 + 28 = 56 kW. The lower limit rotational speed R1 is obtained by multiplying the total operating capacity P thus obtained by, for example, a predetermined positive constant α. The constant α is obtained in advance by experiments or the like. In this way, the lower limit rotational speed R1 is determined based on the total operating capacity P so that it increases as the total operating capacity P increases and decreases as the total operating capacity P decreases.

  After calculating the lower limit rotational speed R1 in S4 of FIG. 3, the control device 40 acquires the current actual rotational speed R of the compressor 11 based on the rotational speed information input from the rotational speed sensor in S5. To do. Subsequently, the control device 40 determines whether or not the actual rotational speed R is equal to or higher than the lower limit rotational speed R1 (S6).

  When it is determined in S6 that the actual rotation speed R is less than the lower limit rotation speed R1 (S6: No), the control device 40 proceeds to S9 and sends a closing operation signal to the bypass opening / closing valve 61. Thereby, the bypass on-off valve 61 is closed. Further, when the bypass opening / closing valve 61 is already closed, the state is maintained. Thereafter, the control device 40 ends this routine.

  On the other hand, when it is determined in S6 that the actual rotational speed R is equal to or higher than the lower limit rotational speed R1 (S9: Yes), the control device 40 proceeds to S7 and closed the bypass on-off valve 61 last time. Later, it is determined whether 15 minutes have passed. If it is determined in S7 that 15 minutes have not elapsed (S7: No), the control device 40 proceeds to S9 and sends a closing operation signal to the bypass on-off valve 61. Thereby, the bypass on-off valve 61 is closed. Further, when the bypass opening / closing valve 61 is already closed, the state is maintained. Thereafter, the control device 40 ends this routine.

  On the other hand, when it is determined in S7 that 15 minutes have elapsed (S7: Yes), the control device 40 proceeds to S8 and sends an open operation signal to the bypass on-off valve 61. Thereby, the bypass on-off valve 61 opens. Further, when the bypass opening / closing valve 61 is already open, the state is maintained. Thereafter, the control device 40 ends this routine. In FIG. 3, the processes of S6, S8, and S9 correspond to the on-off valve control process in the present invention.

When the control device 40 executes the control process of the bypass opening / closing valve 61 described above, the bypass opening / closing valve 61 interposed in the bypass pipe 38 opens when all of the following conditions are satisfied during the cooling operation of the air conditioning apparatus 1. .
Condition 1): Condition where 15 minutes have passed after the start of the air conditioner 1 is completed 2): Condition where the oil return process is not being performed 3): Condition where the actual rotational speed R of the compressor 11 is equal to or higher than the lower limit rotational speed R1 4): More than 15 minutes have passed since the bypass on-off valve 61 was last closed.

  Of the above conditions 1) to 4), when the condition 1) is not satisfied, that is, when 15 minutes have not elapsed since the start of the air conditioner 1, the bypass on-off valve 61 is closed, It is possible to prevent the liquid refrigerant from being supplied into the compressor 11 from the suction port 11a of the compressor 11 via the bypass pipe 38 at an unstable initial stage.

  Further, when the condition 2) is not satisfied, that is, when the air conditioner 1 is in the oil return process, the bypass on-off valve 61 is closed, whereby the compressor 11 and the liquid refrigerant are supplied to the compressor 11 during the oil return process. Can be prevented from being sucked into the compressor 11.

  Further, when the condition 4) is not satisfied, that is, when the bypass on-off valve 61 has not passed 15 minutes since the previous “close” operation, the bypass on-off valve 61 is closed by closing the bypass on-off valve 61. The opening / closing operation interval of 61 is set to 15 minutes or more. Thus, the durability of the bypass opening / closing valve 61 can be improved by setting the opening / closing operation interval of the bypass opening / closing valve 61 to a predetermined time interval or more.

  In the present embodiment, the bypass on-off valve 61 is also closed when the condition 3) is not satisfied, that is, when the actual rotational speed R of the compressor 11 is less than the lower limit rotational speed R1. In other words, when the actual rotational speed R of the compressor 11 is equal to or higher than the lower limit rotational speed R1, the bypass on-off valve 61 opens.

  As described above, the lower limit rotational speed R1 is a rotational speed at which liquid refrigerant is not included in the refrigerant sucked into the suction port 11a of the compressor 11 when the compressor 11 is operating at the rotational speed or higher. It is defined as. Therefore, as long as the compressor 11 operates at a rotational speed equal to or higher than the lower limit rotational speed R1, the liquid refrigerant is transferred to the refrigerant returned from the indoor heat exchanger 22 to the inlet 11a of the compressor 11 via the bypass pipe 38. It will not be included. That is, when the bypass on-off valve 61 is open, the actual rotational speed of the compressor 11 is necessarily equal to or higher than the lower limit rotational speed R1, and therefore the liquid refrigerant is not included in the refrigerant flowing through the bypass pipe 38. Therefore, the compressor 11 is not liquid-compressed.

  Further, the lower limit rotational speed R1 that affects the opening / closing operation of the bypass opening / closing valve 61 is determined based on the total operating capacity P so as to decrease as the total operating capacity P decreases. Here, the total operating capacity P varies depending on the number of indoor heat exchangers 22 in operation and the operating capacity of the indoor heat exchanger 22 in operation. Therefore, in the present embodiment, during the low load operation where the total operating capacity P is small, the actual rotational speed R of the compressor 11 is relatively reduced. At this time, the lower limit rotational speed R1 of the compressor 11 is also reduced. . Therefore, during low load operation (when the actual rotational speed R of the compressor 11 is low), the lower limit of the rotational speed region of the compressor 11 that may open the bypass opening / closing valve 61 is set low. Therefore, even during the low load operation, the bypass opening / closing valve 61 can be opened so that the gas refrigerant flowing out of the indoor heat exchanger 22 bypasses the accumulator 18. Therefore, the refrigeration efficiency during the cooling operation can be improved by returning the gas refrigerant flowing out of the indoor heat exchanger 22 directly to the compressor 11 without passing through the accumulator 18 even during the low load operation.

  Moreover, in the said patent document 1, the condition that "outside temperature is more than predetermined temperature" is set to the conditions for opening a bypass on-off valve. In the present embodiment, such an outside air temperature condition is not included in the condition for opening the bypass opening / closing valve 61. Therefore, even during the cooling operation at a low outside air temperature, the bypass on-off valve 61 opens as long as the above conditions 1) to 4) are satisfied. For this reason, the refrigerating efficiency at the time of air_conditionaing | cooling operation can be improved further.

  Moreover, in the said patent document 1, the condition that "room setting temperature is more than predetermined temperature" is set to the conditions for opening a bypass on-off valve. In the present embodiment, such indoor set temperature conditions are not included in the conditions for opening the bypass opening / closing valve 61. Therefore, even when the indoor set temperature is low, as long as the above conditions 1) to 4) are satisfied, the bypass on-off valve 61 is opened. For this reason, the refrigerating efficiency at the time of air_conditionaing | cooling operation can be improved further.

  Moreover, in the said patent document 1, the condition that "the rotational speed of an indoor fan motor is more than predetermined rotational speed" is set to the conditions for opening a bypass on-off valve. In the present embodiment, such a fan motor rotation speed condition is not included in the condition for opening the bypass opening / closing valve 61. Therefore, even when the air volume of the indoor fan is low, the bypass opening / closing valve 61 is opened as long as the above conditions 1) to 4) are satisfied. For this reason, the refrigerating efficiency at the time of air_conditionaing | cooling operation can be improved further.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. For example, the lower limit rotation speed R1 described in the above embodiment is a rotation speed reflecting the size of the total operation capacity P so that the lower the total operation capacity P of the indoor heat exchanger 22 during the cooling operation, the lower the rotation speed R1. If it is under such a premise, the lower limit rotational speed R1 can also be determined in consideration of other factors. The lower limit rotational speed R1 is obtained by adding a rotational speed obtained by multiplying a rotational speed obtained based on the total operating capacity P of the indoor heat exchanger 22 during the cooling operation to a predetermined safety factor or a predetermined rotational speed. The rotation speed can also be determined. Thus, the present invention can be modified without departing from the gist thereof.

DESCRIPTION OF SYMBOLS 1 ... Air conditioning apparatus, 10 ... Outdoor unit, 11 ... Compressor, 11a ... Suction port, 11b ... Discharge port, 13 ... Four-way valve, 13a ... First port, 13b ... Second port, 13c ... Third port, 13d 4th port, 14 ... Outdoor heat exchanger, 15 ... Outdoor electronic expansion valve, 18 ... Accumulator, 20a, 20b, 20c, 20d ... Indoor unit, 21 ... Indoor electronic expansion valve (expansion valve), 22 ... Indoor Heat exchanger, 30 ... refrigerant pipe (refrigerant passage), 31 ... first pipe, 32 ... second pipe, 33 ... third pipe, 34 ... intermediate pipe, 35 ... accumulator inlet pipe, 36 ... accumulator outlet pipe, 37 ... Branch piping 38 ... Bypass piping (bypass passage) 39 ... Hot gas bypass piping 40 ... Control device 51 ... Discharge temperature sensor 52 ... Suction temperature sensor 53 ... Suction pressure sensor 54 ... Outside air temperature sensor , 61 ... bypass on-off valve, 62 ... hot gas bypass opening and closing valve, P ... total operating capacity, R ... actual rotational speed, R1 ... lower limit speed,

Claims (4)

A compressor that includes a suction port and a discharge port, sucks refrigerant from the suction port, compresses the sucked refrigerant, and discharges the compressed refrigerant from the discharge port;
An outdoor heat exchanger for exchanging heat between the refrigerant and the outside air;
An expansion valve for expanding the refrigerant;
A plurality of indoor heat exchangers for exchanging heat between the refrigerant and room air;
An accumulator for gas-liquid separation of the refrigerant;
During the cooling operation, the refrigerant discharged from the discharge port of the compressor flows through the outdoor heat exchanger, the expansion valve, the plurality of indoor heat exchangers, and the accumulator in this order, and then the compressor of the compressor A refrigerant passage connecting the compressor, the outdoor heat exchanger, the expansion valve, the plurality of indoor heat exchangers, and the accumulator so as to be returned to the suction port;
A first port connected to the discharge port of the compressor, a second port connected to the indoor heat exchanger, a third port connected to the outdoor heat exchanger, and the accumulator A four-way valve having a fourth port and controlled so that the first port communicates with the third port and the second port communicates with the fourth port during cooling operation;
A bypass passage that guides the refrigerant flowing through a portion of the refrigerant passage downstream of the indoor heat exchanger and upstream of the four-way valve during cooling operation to the suction port of the compressor;
A bypass on-off valve configured to be interposed in the bypass passage and open to allow the refrigerant to flow in the bypass passage, and to close to prohibit the refrigerant from flowing in the bypass passage;
A control device for controlling the opening and closing operation of the bypass on-off valve,
The control device is
During cooling operation, the lower limit rotational speed that determines the lower limit rotational speed of the compressor based on the total operating capacity so that the lower the total operating capacity of the operating indoor heat exchanger among the plurality of indoor heat exchangers, the lower the lower Configuration process,
The bypass on-off valve opens when the actual rotational speed of the compressor during cooling operation is equal to or higher than the lower limit rotational speed, and the actual rotational speed of the compressor during cooling operation is less than the lower limit rotational speed An on-off valve control process for controlling an on-off operation of the bypass on-off valve so that the bypass on-off valve is closed.
Run the air conditioner. In the air conditioning apparatus according to claim 1,
The lower limit rotational speed setting process is performed so that liquid refrigerant is not included in the refrigerant sucked into the suction port of the compressor when the compressor is operated at a rotational speed equal to or higher than a set lower limit rotational speed. An air conditioner that is a process for determining a lower limit rotation speed based on the total operating capacity. In the air conditioning apparatus according to claim 1 or 2 ,
The controller opens and closes the bypass opening / closing valve so that the bypass opening / closing valve is closed when oil return control is performed to return the oil sleeping in the indoor heat exchanger to the compressor during cooling operation. An air conditioner that controls valves. The air conditioning apparatus according to any one of claims 1 to 3 ,
The control device is configured to close the bypass opening / closing valve before a predetermined time elapses from the start of the cooling operation by the air conditioner until the operation of the air conditioner is stabilized. And an air conditioner for controlling the bypass on-off valve.

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