JP6036357B2 - Air conditioner - Google Patents

Description

  The present invention has an air conditioner, in particular, a refrigerant circuit configured by connecting a compressor, an outdoor heat exchanger, a receiver, a first expansion valve, and an indoor heat exchanger. The present invention relates to an air conditioner capable of circulating a refrigerant in the order of a heat exchanger, a receiver, a first expansion valve, and an indoor heat exchanger.

  Conventionally, as shown in Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-80649), a refrigerant circuit configured by connecting a compressor, an outdoor heat exchanger, a receiver, a first expansion valve, and an indoor heat exchanger. And an air conditioner that can circulate refrigerant in the order of a compressor, an outdoor heat exchanger, a receiver, a first expansion valve, and an indoor heat exchanger.

  In the above conventional air conditioner, when the operation is stopped, the receiver provided in the refrigerant circuit is capable of suppressing the inflow of the liquid refrigerant to the suction side of the compressor and protecting the compressor or quickly restarting the operation. It is conceivable to perform control for forcibly storing the liquid refrigerant in the receiver by using the above.

  Here, when the volume of the heat exchanger or the refrigerant pipe is large, even if the forced liquid reservoir control to the receiver cannot be sufficiently performed, the liquid refrigerant that is accumulated in the heat exchanger or the refrigerant pipe is formed. Including this amount, the inflow of the liquid refrigerant to the suction side of the compressor can be sufficiently suppressed. For this reason, there is little possibility that the protection of the compressor and the rapid resumption of operation are hindered.

  However, for example, when the volume of the outdoor heat exchanger is reduced by adopting a heat exchanger that uses a flat multi-hole tube as the heat transfer tube as the outdoor heat exchanger, the heat exchanger or the refrigerant tube The amount of liquid refrigerant that accumulates as a result is small. For this reason, when the forced liquid reservoir control to the receiver cannot be sufficiently performed, there is a possibility that the inflow of the liquid refrigerant to the suction side of the compressor cannot be sufficiently suppressed. Therefore, there is a possibility that the protection of the compressor and the quick resumption of operation may be hindered.

  In addition, an accumulator (larger capacity than the small-capacity accumulator attached to the compressor) is provided on the suction side of the compressor to store the liquid refrigerant, so that when the operation resumes, the liquid refrigerant to the suction side of the compressor It is possible to suppress the inflow. However, when a refrigerant having a very low solubility of refrigerating machine oil under a low temperature condition such as R32 is used as the refrigerant enclosed in the refrigerant circuit, it is not preferable to provide an accumulator on the suction side of the compressor. That is, when using a refrigerant having low solubility of refrigerating machine oil under low temperature conditions, the refrigerant accumulated in the accumulator and the refrigerating machine oil may be separated into two layers, and the refrigerating machine oil may not return to the compressor. As a result, insufficient lubrication may occur and the reliability of the compressor may be impaired. That is, when it is not preferable to provide an accumulator on the suction side of the compressor as in the case of using a refrigerant having low solubility of refrigerating machine oil under low temperature conditions, an accumulator cannot be provided on the suction side of the compressor. When the operation is resumed, the liquid refrigerant is liable to flow into the suction side of the compressor, which may impede the protection of the compressor and the rapid resumption of operation.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an air conditioner having a receiver that can sufficiently perform forcible reservoir control of refrigerant including the receiver when the operation is stopped, thereby protecting the compressor and restarting the operation quickly. Is to make it possible.

  An air conditioner according to a first aspect has a refrigerant circuit configured by connecting a compressor, an outdoor heat exchanger, a receiver, a first expansion valve, and an indoor heat exchanger, It is an air conditioner capable of circulating a refrigerant in the order of an outdoor heat exchanger, a receiver, a first expansion valve, and an indoor heat exchanger. The refrigerant circuit has a receiver gas vent valve that can be controlled to open and close, and is provided with a receiver gas vent pipe for guiding the gas refrigerant accumulated in the receiver to the suction side of the compressor. Here, when the operation is stopped, the receiver degassing valve is closed and the first expansion valve is opened so that the refrigerant present on the outdoor heat exchanger side of the first expansion valve is forced to flow into the room. Receiver liquid which performs indoor side liquid reservoir control to be moved to the heat exchanger side, and after the indoor side liquid reservoir control, opens the receiver gas vent valve and closes the first expansion valve to forcibly accumulate the refrigerant in the receiver. Reservoir control is performed, and then the receiver degassing valve is closed and the compressor is stopped.

  Here, when the operation is stopped, the two-stage liquid reservoir control, that is, the indoor side liquid reservoir control and the receiver liquid reservoir control is performed. First, in the indoor side liquid reservoir control, the receiver degassing valve is closed to suppress the liquid reservoir in the receiver, and the first expansion valve is opened to be present on the outdoor heat exchanger side. The refrigerant to be forcibly accumulated on the indoor heat exchanger side from the receiver and the first expansion valve. For this reason, prior to storing the liquid in the receiver, the liquid can be stored in the refrigerant circuit by using the portion where the liquid refrigerant flows on the indoor heat exchanger side of the receiver of the refrigerant circuit. And after that, the refrigerant which exists in the outdoor heat exchanger side is made into the receiver by making the state which closed the 1st expansion valve, encouraging the liquid reservoir in the receiver by making the receiver degassing valve into the opened state. It is forcibly stored inside. For this reason, the liquid reservoir of the refrigerant | coolant can be performed in the part and the receiver in which the liquid refrigerant by the side of an indoor heat exchanger flows rather than the receiver of a refrigerant circuit. Then, the operation can be stopped by stopping the compressor while closing the receiver gas vent valve so as to suppress the refrigerant from flowing out of the receiver as much as possible. That is, here, the forced liquid reservoir control including the receiver can be sufficiently performed when the operation is stopped, and the liquid refrigerant can be prevented from flowing into the suction side of the compressor. Further, even when the accumulator cannot be provided on the suction side of the compressor, it is possible to prevent the liquid refrigerant from flowing into the suction side of the compressor when the operation is resumed.

  As a result, when the operation is stopped, forcible liquid reservoir control including the receiver is sufficiently performed by performing two-stage liquid reservoir control including indoor-side liquid reservoir control and receiver liquid reservoir control. As a result, the compressor can be protected and the operation can be restarted quickly.

  An air conditioner according to a second aspect is the air conditioner according to the first aspect, wherein the refrigerant circuit further includes a second expansion valve between the outdoor heat exchanger and the receiver. The valve is opened during the indoor liquid reservoir control and the receiver liquid reservoir control, and is closed after the receiver liquid reservoir control is completed.

  Here, a configuration of a refrigerant circuit is adopted in which the receiver is disposed so as to be sandwiched between the second expansion valve and the first expansion valve. The second expansion valve is opened in the indoor side liquid reservoir control and the receiver liquid reservoir control, so that the liquid refrigerant on the indoor heat exchanger side from the receiver of the refrigerant circuit flows in the receiver and the receiver. By storing the refrigerant in the reservoir and closing it after the receiver liquid reservoir control is completed, it is possible to reliably prevent the refrigerant from flowing out of the receiver.

  Thereby, the refrigerant | coolant collected in the receiver by receiver liquid reservoir control can be reliably hold | maintained in a receiver here by closing a 2nd expansion valve after completion | finish of receiver liquid reservoir control.

  An air conditioner according to a third aspect is the air conditioner according to the first or second aspect, further comprising an outdoor fan that supplies outdoor air to the outdoor heat exchanger, and the outdoor fan The maximum air volume is set at the time of liquid reservoir control and at the time of receiver liquid reservoir control.

  Here, by setting the outdoor fan to the maximum air volume at the time of indoor side liquid reservoir control and at the time of receiver liquid reservoir control, the condensation capacity of the refrigerant in the outdoor heat exchanger is increased, and in the outdoor heat exchanger, from the receiver of the refrigerant circuit In addition, it is possible to increase the amount of the liquid refrigerant sent to the portion where the liquid refrigerant flows on the indoor heat exchanger side and the receiver.

  Thereby, here, by setting the outdoor fan to the maximum air volume, it is possible to increase the portion where the liquid refrigerant flows on the indoor heat exchanger side than the receiver of the refrigerant circuit and the amount of liquid refrigerant stored in the receiver.

  An air conditioner according to a fourth aspect is the air conditioner according to any of the first to third aspects, wherein the outdoor heat exchanger is a heat exchanger that uses a flat multi-hole tube as a heat transfer tube.

  Here, since the heat exchanger which uses a flat multi-hole tube as a heat transfer tube is employ | adopted as an outdoor heat exchanger, the volume of an outdoor heat exchanger is small. However, here, as described above, when the operation is stopped, the two-stage liquid reservoir control of the indoor side liquid reservoir control and the receiver liquid reservoir control is performed, thereby forcibly storing the refrigerant including the receiver. The control can be performed sufficiently.

  As a result, here, although a heat exchanger that uses a flat multi-hole tube as the heat transfer tube is adopted as the outdoor heat exchanger, a two-stage liquid reservoir, that is, an indoor side liquid reservoir control and a receiver liquid reservoir control. By performing the control, it is possible to sufficiently perform the forced liquid reservoir control including the receiver, and it is possible to protect the compressor and to quickly restart the operation.

  As described above, according to the present invention, the following effects can be obtained.

  In the air conditioner according to the first aspect, when the operation is stopped, the two-stage liquid reservoir control of the indoor side liquid reservoir control and the receiver liquid reservoir control is performed, thereby forcing the liquid including the receiver to be forced. Reservoir control can be sufficiently performed, so that the compressor can be protected and the operation can be quickly restarted.

  In the air conditioning apparatus according to the second aspect, the refrigerant stored in the receiver by the receiver liquid reservoir control can be reliably held in the receiver by closing the second expansion valve after the receiver liquid reservoir control is completed. it can.

  In the air conditioner according to the third aspect, by setting the outdoor fan to the maximum air volume, the amount of liquid refrigerant stored in the receiver and the portion where the liquid refrigerant flows on the indoor heat exchanger side than the receiver of the refrigerant circuit are increased. Can be made.

  In the air conditioner according to the fourth aspect, although the heat exchanger using a flat multi-hole tube as the heat transfer tube is adopted as the outdoor heat exchanger, it is called indoor side liquid reservoir control and receiver liquid reservoir control. By performing the two-stage liquid reservoir control, it is possible to sufficiently perform the forced liquid reservoir control of the refrigerant including the receiver, thereby enabling the protection of the compressor and the quick operation restart. .

It is a schematic block diagram of the air conditioning apparatus concerning one Embodiment of this invention. It is a schematic perspective view of an outdoor heat exchanger. It is a schematic longitudinal cross-sectional view of an outdoor heat exchanger. It is a schematic perspective view of another outdoor heat exchanger. It is a control block diagram of an air conditioning apparatus. It is a flowchart of the cooling stop control. It is a time chart which shows operation | movement of the compressor at the time of cooling stop control, an outdoor fan, an indoor fan, a 1st expansion valve, and a receiver degassing valve. It is a flowchart of heating stop control. It is a time chart which shows operation | movement of the compressor at the time of heating stop control, an outdoor fan, an indoor fan, a four-way selector valve, a 1st expansion valve, and a receiver degassing valve. It is a schematic block diagram of the air conditioning apparatus concerning a modification. It is a control block diagram of the air conditioning apparatus concerning a modification. It is a time chart which shows operation | movement of the compressor at the time of the cooling stop control concerning a modification, an outdoor fan, an indoor fan, a 2nd expansion valve, a 1st expansion valve, and a receiver degassing valve. It is a time chart which shows operation | movement of the compressor at the time of the heating stop control concerning a modification, an outdoor fan, an indoor fan, a four-way switching valve, a 2nd expansion valve, a 1st expansion valve, and a receiver degassing valve.

  Hereinafter, an embodiment of an air harmony device concerning the present invention and its modification are described based on a drawing. In addition, the specific structure of the air conditioning apparatus concerning this invention is not restricted to the following embodiment and its modification, It can change in the range which does not deviate from the summary of invention.

(1) Configuration of Air Conditioner FIG. 1 is a schematic configuration diagram of an air conditioner 1 according to an embodiment of the present invention.

  The air conditioner 1 is a device capable of cooling and heating a room such as a building by performing a vapor compression refrigeration cycle. The air conditioner 1 is mainly configured by connecting an outdoor unit 2 and an indoor unit 4. Here, the outdoor unit 2 and the indoor unit 4 are connected via a liquid refrigerant communication tube 5 and a gas refrigerant communication tube 6. That is, the vapor compression refrigerant circuit 10 of the air conditioner 1 is configured by connecting the outdoor unit 2 and the indoor unit 4 via the refrigerant communication pipes 5 and 6. The refrigerant circuit 10 contains R32, which is a kind of HFC refrigerant, as a refrigerant. The refrigerant circuit 10 is filled with refrigeration oil for lubricating the compressor 21 (described later) together with the refrigerant. Here, as the refrigerating machine oil, an ether-based synthetic oil whose solubility in R32 is extremely low under low temperature conditions, a mineral oil or an alkylbenzene-based synthetic oil that is incompatible with R32, and the like are used.

<Indoor unit>
The indoor unit 4 is installed indoors and constitutes a part of the refrigerant circuit 10. The indoor unit 4 mainly has an indoor heat exchanger 41.

  The indoor heat exchanger 41 is a heat exchanger that functions as a refrigerant evaporator during cooling operation to cool indoor air, and functions as a refrigerant radiator during heating operation to heat indoor air. The liquid side of the indoor heat exchanger 41 is connected to the liquid refrigerant communication tube 5, and the gas side of the indoor heat exchanger 41 is connected to the gas refrigerant communication tube 6. Here, the indoor heat exchanger 41 is a heat exchanger that uses a circular tube as a heat transfer tube. More specifically, the indoor heat exchanger 41 is a cross fin type fin-and-tube heat exchanger composed of a heat transfer tube formed of a circular tube and a large number of fins. As the heat transfer tube, a circular tube having a flow hole having an inner diameter of about 3 to 20 mm is used.

  The indoor unit 4 has an indoor fan 42 for supplying indoor air as supply air after sucking indoor air into the indoor unit 4 and exchanging heat with the refrigerant in the indoor heat exchanger 41. That is, the indoor unit 4 has an indoor fan 42 as a fan that supplies indoor air as a heating source or cooling source of the refrigerant flowing through the indoor heat exchanger 41 to the indoor heat exchanger 41. Here, as the indoor fan 42, a centrifugal fan or a multiblade fan driven by an indoor fan motor 43 is used. The indoor fan motor 43 can change the rotation speed by an inverter or the like.

  Various sensors are provided in the indoor unit 4. Specifically, the indoor heat exchanger 41 includes an indoor heat exchange liquid side temperature sensor 57 that detects the temperature Trrl of the refrigerant on the liquid side of the indoor heat exchanger 41, and the refrigerant in the intermediate portion of the indoor heat exchanger 41. An indoor heat exchanger intermediate temperature sensor 58 for detecting the temperature Trrm is provided. The indoor unit 4 is provided with an indoor temperature sensor 59 that detects the temperature Tra of the indoor air sucked into the indoor unit 4.

  The indoor unit 4 includes an indoor side control unit 44 that controls the operation of each unit constituting the indoor unit 4. And the indoor side control part 44 has the microcomputer, memory, etc. which were provided in order to control the indoor unit 4, and is with the remote control (not shown) for operating the indoor unit 4 separately. Control signals and the like can be exchanged between them, and control signals and the like can be exchanged with the outdoor unit 2 via the transmission line 8a.

<Outdoor unit>
The outdoor unit 2 is installed outside and constitutes a part of the refrigerant circuit 10. The outdoor unit 2 mainly includes a compressor 21, a four-way switching valve 22, an outdoor heat exchanger 23, a receiver 25, a first expansion valve 26, a liquid side closing valve 27, and a gas side closing valve 28. And a receiver degassing pipe 30.

  The compressor 21 is a device that compresses the low-pressure refrigerant in the refrigeration cycle until the pressure becomes high. The compressor 21 has a hermetic structure in which a rotary type or scroll type positive displacement compression element (not shown) is rotationally driven by a compressor motor 21a controlled by an inverter. The compressor 21 has a suction pipe 31 connected to the suction side and a discharge pipe 32 connected to the discharge side. The suction pipe 31 is a refrigerant pipe that connects the suction side of the compressor 21 and the first port 22 a of the four-way switching valve 22. The suction pipe 31 is provided with a small volume accumulator 29 attached to the compressor 21. The discharge pipe 32 is a refrigerant pipe that connects the discharge side of the compressor 21 and the second port 22 b of the four-way switching valve 22. The discharge pipe 32 is provided with a check valve 32 a that allows only a refrigerant flow from the discharge side of the compressor 21 to the second port 22 b side of the four-way switching valve 22.

  The four-way switching valve 22 is a switching valve for switching the direction of refrigerant flow in the refrigerant circuit 10. During the cooling operation, the four-way switching valve 22 causes the outdoor heat exchanger 23 to function as a radiator for the refrigerant compressed in the compressor 21 and the indoor heat exchanger 41 for the refrigerant that has radiated heat in the outdoor heat exchanger 23. Switch to the cooling cycle state to function as an evaporator. That is, during the cooling operation, the four-way switching valve 22 switches between the second port 22b and the third port 22c and the first port 22a and the fourth port 22d. Thereby, the discharge side of the compressor 21 (here, the discharge pipe 32) and the gas side of the outdoor heat exchanger 23 (here, the first gas refrigerant pipe 33) are connected (four-way switching valve in FIG. 1). (See 22 solid line). Moreover, the suction side (here, the suction pipe 31) of the compressor 21 and the gas refrigerant communication pipe 6 side (here, the second gas refrigerant pipe 34) are connected (solid line of the four-way switching valve 22 in FIG. 1). See). Further, the four-way switching valve 22 causes the outdoor heat exchanger 23 to function as an evaporator of the refrigerant that has radiated heat in the indoor heat exchanger 41 during the heating operation, and the indoor heat exchanger 41 is compressed in the compressor 21. Switching to a heating cycle state that functions as a refrigerant radiator. In other words, the four-way switching valve 22 switches between the second port 22b and the fourth port 22d and the first port 22a and the third port 22c during the heating operation. Thereby, the discharge side (here, the discharge pipe 32) of the compressor 21 and the gas refrigerant communication pipe 6 side (here, the second gas refrigerant pipe 34) are connected (of the four-way switching valve 22 in FIG. 1). (See dashed line). In addition, the suction side of the compressor 21 (here, the suction pipe 31) and the gas side of the outdoor heat exchanger 23 (here, the first gas refrigerant pipe 33) are connected (four-way switching valve 22 in FIG. 1). See the dashed line). The first gas refrigerant pipe 33 is a refrigerant pipe that connects the third port 22 c of the four-way switching valve 22 and the gas side of the outdoor heat exchanger 23. The second gas refrigerant pipe 34 is a refrigerant pipe that connects the fourth port 22d of the four-way switching valve 22 and the gas refrigerant communication pipe 6 side.

  The outdoor heat exchanger 23 is a heat exchanger that functions as a refrigerant radiator that uses outdoor air as a cooling source during cooling operation, and functions as a refrigerant evaporator that uses outdoor air as a heating source during heating operation. The outdoor heat exchanger 23 has a liquid side connected to the liquid refrigerant pipe 35 and a gas side connected to the first gas refrigerant pipe 33. The liquid refrigerant pipe 35 is a refrigerant pipe that connects the liquid side of the outdoor heat exchanger 23 and the liquid refrigerant communication pipe 5 side. The outdoor heat exchanger 23 is a heat exchanger that uses a flat multi-hole tube as a heat transfer tube. More specifically, as shown in FIGS. 2 and 3, the outdoor heat exchanger 23 is mainly composed of a heat transfer tube 231 formed of a flat multi-hole tube and a large number of insertion fins 232. This is a stacked heat exchanger of the type. The heat transfer tube 231 formed of a flat multi-hole tube is formed of aluminum or an aluminum alloy, and has upper and lower flat portions serving as heat transfer surfaces and a large number of small refrigerant channels 231a through which a refrigerant flows. As the refrigerant channel 231a, a circular channel having an inner diameter of 1 mm or less or a polygonal channel hole having an equivalent cross-sectional area is used. The heat transfer tubes 231 are arranged in a plurality of stages at intervals with the plane portion facing up and down, and both ends thereof are connected to the headers 233 and 234. The insertion fins 232 are aluminum or aluminum alloy fins and are in contact with the heat transfer tubes 231. The insertion fins 232 are formed with a plurality of notches 232a extending horizontally so that the insertion fins 232 can be inserted into the plurality of stages of heat transfer tubes 231 arranged between the headers 233 and 234. Yes. The shape of the notch 232 a of these insertion fins 232 substantially matches the outer shape of the cross section of the heat transfer tube 231. The headers 233 and 234 have a function of supporting the heat transfer tube 231, a function of guiding the refrigerant to the refrigerant flow path 231 a of the heat transfer pipe 231, and a function of collecting the refrigerant that has come out of the refrigerant flow path 231 a. In addition to the heat transfer tube 231, a second gas refrigerant tube 33 and a liquid refrigerant tube 35 (not shown in FIG. 2) are connected to these headers 233 and 234. The outdoor heat exchanger 23 is not limited to the insertion fin type stacked heat exchanger as described above. For example, as shown in FIG. 4, a plurality of heat transfer tubes each formed of a flat multi-hole tube. It may be a corrugated fin type stacked heat exchanger composed of 231 and a large number of corrugated fins 237. Here, the corrugated fins 237 are fins made of aluminum or aluminum alloy bent into a corrugated shape. The corrugated fins 237 are disposed in the ventilation space sandwiched between the heat transfer tubes 231 adjacent in the vertical direction, and the valley portion and the mountain portion thereof are in contact with the flat portion of the heat transfer tube 231. And the outdoor heat exchanger 23 which uses the flat multi-hole pipe | tube as such a heat exchanger tube 231 has a small capacity | capacitance which can hold | maintain a refrigerant | coolant here, The volume which can hold | maintain the refrigerant | coolant of the indoor heat exchanger 41 is here. Is also getting smaller.

  The receiver 25 is provided between the outdoor heat exchanger 23 and the first expansion valve 26. The receiver 25 is a container that is capable of storing high-pressure refrigerant in the refrigeration cycle that has become high pressure in the refrigeration cycle during cooling operation and radiates heat in the outdoor heat exchanger 23. The receiver 25 is a container capable of storing a low-pressure refrigerant in the refrigeration cycle after being reduced in pressure in the refrigeration cycle during the heating operation and decompressed in the first expansion valve 26.

  The first expansion valve 26 is a valve that decompresses the high-pressure refrigerant in the refrigeration cycle radiated in the outdoor heat exchanger 23 to the low pressure in the refrigeration cycle during the cooling operation. The first expansion valve 26 is a valve that decompresses the high-pressure refrigerant in the refrigeration cycle stored in the receiver 25 to a low pressure in the refrigeration cycle during heating operation. The first expansion valve 26 is provided in a portion of the liquid refrigerant pipe 35 near the liquid side closing valve 27. Here, an electric expansion valve is used as the first expansion valve 26.

  The liquid side shut-off valve 27 and the gas side shut-off valve 28 are valves provided at connection ports with external devices and pipes (specifically, the liquid refrigerant communication pipe 5 and the gas refrigerant communication pipe 6). The liquid side closing valve 27 is provided at the end of the liquid refrigerant pipe 35. The gas side closing valve 28 is provided at the end of the second gas refrigerant pipe 34.

  The receiver degassing pipe 30 is a refrigerant pipe that guides high-pressure or low-pressure gas refrigerant in the refrigeration cycle accumulated in the receiver 25 to the suction pipe 31 of the compressor 21. The receiver degassing pipe 30 is provided so as to connect between the upper part of the receiver 25 and the middle part of the suction pipe 31. The receiver gas vent pipe 30 is provided with a receiver gas vent valve 30a, a capillary tube 30b, and a check valve 30c. The receiver degassing valve 30a is a valve that can be opened and closed to turn on / off the refrigerant flow in the receiver degassing pipe 30, and here, an electromagnetic valve is used. The capillary tube 30b is a mechanism that depressurizes the gas refrigerant accumulated in the receiver 25 to a low pressure in the refrigeration cycle, and here, a capillary tube having a diameter smaller than that of the receiver degassing tube is used. The check valve 30c is a valve mechanism that allows only the flow of refrigerant from the receiver 25 side to the suction pipe 31 side, and a check valve is used here.

  The outdoor unit 2 has an outdoor fan 36 for sucking outdoor air into the outdoor unit 2 and exchanging heat with the refrigerant in the outdoor heat exchanger 23 and then discharging the air to the outside. That is, the outdoor unit 2 includes an outdoor fan 36 as a fan that supplies outdoor air as a cooling source or a heating source of the refrigerant flowing through the outdoor heat exchanger 23 to the outdoor heat exchanger 23. Here, a propeller fan or the like driven by an outdoor fan motor 37 is used as the outdoor fan 36. Moreover, the motor 37 for outdoor fans can change the rotation speed by an inverter or the like.

  Various types of sensors are provided in the outdoor unit 2. Specifically, the suction pipe 31 is provided with a suction temperature sensor 51 that detects the temperature Ts of the low-pressure refrigerant in the refrigeration cycle sucked into the compressor 21. Here, the suction temperature sensor 51 is provided at a position downstream of the joining portion of the suction pipe 31 and the receiver degassing pipe 30. The discharge pipe 32 is provided with a discharge temperature sensor 52 that detects the temperature Td of the high-pressure refrigerant in the refrigeration cycle discharged from the compressor 21. The outdoor heat exchanger 23 includes an outdoor heat exchange intermediate temperature sensor 53 that detects a refrigerant temperature Torm in an intermediate portion of the outdoor heat exchanger 23, and an outdoor that detects a refrigerant temperature Torl on the liquid side of the outdoor heat exchanger 23. A heat exchanger side temperature sensor 54 is provided. The outdoor unit 2 is provided with an outdoor temperature sensor 55 that detects the temperature Toa of the outdoor air sucked into the outdoor unit 2. The liquid refrigerant pipe 35 is provided with a liquid pipe temperature sensor 56 that detects a liquid pipe temperature Tlp of the refrigerant in a portion of the first expansion valve 26 closer to the room.

  The outdoor unit 2 includes an outdoor side control unit 38 that controls the operation of each unit constituting the outdoor unit 2. The outdoor control unit 38 includes a microcomputer, a memory, and the like provided for controlling the outdoor unit 2, and a transmission line between the indoor unit 4 (that is, the indoor control unit 44). Control signals and the like can be exchanged via 8a.

<Refrigerant communication pipe>
Refrigerant communication pipes 5 and 6 are refrigerant pipes constructed on site when the air conditioner 1 is installed at an installation location such as a building, and installation conditions such as the installation location and a combination of an outdoor unit and an indoor unit. Those having various lengths and tube diameters are used.

  As described above, the refrigerant circuit 10 of the air conditioner 1 is configured by connecting the outdoor unit 2, the indoor unit 4, and the refrigerant communication pipes 5 and 6. In the air conditioner 1, the refrigerant is circulated in the order of the compressor 21, the outdoor heat exchanger 23, the receiver 25, the first expansion valve 26, and the indoor heat exchanger 41, and the outdoor fan 36 is driven to perform the cooling operation. It has become. In addition, the air conditioner 1 switches the four-way switching valve 22 to the heating cycle state, whereby refrigerant is supplied in the order of the compressor 21, the indoor heat exchanger 41, the first expansion valve 26, the receiver 25, and the outdoor heat exchanger 23. The outdoor fan 36 is driven and the heating operation is performed while circulating. The refrigerant circuit 10 has a receiver degassing valve 30 a that can be controlled to open and close, and is provided with a receiver degassing pipe 30 that guides the gas refrigerant accumulated in the receiver 25 to the suction side of the compressor 21. . The outdoor heat exchanger 23 is a heat exchanger that uses a flat multi-hole tube as the heat transfer tube 231.

<Control unit>
The air conditioner 1 can control each device of the outdoor unit 2 and the indoor unit 4 by the control unit 8 including the indoor side control unit 44 and the outdoor side control unit 38. That is, the control unit 8 that performs operation control of the entire air conditioner 1 including the cooling operation and the heating operation described above is configured by the transmission line 8a that connects between the indoor side control unit 44 and the outdoor side control unit 38. Has been.

  As shown in FIG. 5, the control unit 8 is connected so as to receive detection signals from various sensors 51 to 59 and the like, and based on these detection signals and the like, various devices and valves 21 a, 22, and 26. , 30a, 37, 43, etc. are connected so that they can be controlled.

(2) Basic Operation of Air Conditioner Next, the basic operation of the air conditioner 1 (the operation excluding stop control described later) will be described with reference to FIG. The air conditioner 1 can perform a cooling operation and a heating operation as basic operations.

<Cooling operation>
During the cooling operation, the four-way switching valve 22 is switched to the cooling cycle state (state indicated by the solid line in FIG. 1).

  In the refrigerant circuit 10, the low-pressure gas refrigerant in the refrigeration cycle is sucked into the compressor 21 and is discharged after being compressed to a high pressure in the refrigeration cycle.

  The high-pressure gas refrigerant discharged from the compressor 21 is sent to the outdoor heat exchanger 23 through the four-way switching valve 22.

  The high-pressure gas refrigerant sent to the outdoor heat exchanger 23 performs heat exchange with the outdoor air supplied as a cooling source by the outdoor fan 36 in the outdoor heat exchanger 23 to dissipate heat to become a high-pressure liquid refrigerant. .

  The high-pressure liquid refrigerant that has radiated heat in the outdoor heat exchanger 23 is sent to the receiver 25 for gas-liquid separation. The gas refrigerant separated in the receiver 25 is sent to the suction pipe 31 through the receiver gas vent pipe 30 by opening the receiver gas vent valve 30a. Further, the liquid refrigerant that has been gas-liquid separated in the receiver 25 is sent to the first expansion valve 26.

  The high-pressure liquid refrigerant sent to the first expansion valve 26 is depressurized by the first expansion valve 26 to a low pressure in the refrigeration cycle. The refrigerant decompressed by the first expansion valve 26 is sent to the indoor heat exchanger 41 through the liquid side closing valve 27 and the liquid refrigerant communication pipe 5.

  The low-pressure refrigerant sent to the indoor heat exchanger 41 evaporates by exchanging heat with indoor air supplied as a heating source by the indoor fan 42 in the indoor heat exchanger 41. As a result, the room air is cooled and then supplied to the room to cool the room.

  The low-pressure gas refrigerant evaporated in the indoor heat exchanger 41 is sent to the suction pipe 31 through the gas refrigerant communication pipe 6, the gas side closing valve 28 and the four-way switching valve 22, and flows into the receiver gas vent pipe 30. The refrigerant merges with the refrigerant and is sucked into the compressor 21 again.

<Heating operation>
During the heating operation, the four-way switching valve 22 is switched to the heating cycle state (the state indicated by the broken line in FIG. 1).

  In the refrigerant circuit 10, the low-pressure gas refrigerant in the refrigeration cycle is sucked into the compressor 21 and is discharged after being compressed to a high pressure in the refrigeration cycle.

  The high-pressure gas refrigerant discharged from the compressor 21 is sent to the indoor heat exchanger 41 through the four-way switching valve 22, the gas side closing valve 28 and the gas refrigerant communication pipe 6.

  The high-pressure gas refrigerant sent to the indoor heat exchanger 41 radiates heat by exchanging heat with indoor air supplied as a cooling source by the indoor fan 42 in the indoor heat exchanger 41 to become a high-pressure liquid refrigerant. . Thereby, indoor air is heated, and indoor heating is performed by being supplied indoors after that.

  The high-pressure liquid refrigerant radiated by the indoor heat exchanger 41 is sent to the first expansion valve 26 through the liquid refrigerant communication pipe 5 and the liquid side closing valve 27.

  The high-pressure liquid refrigerant sent to the first expansion valve 26 is depressurized by the first expansion valve 26 to a low pressure in the refrigeration cycle. The low-pressure refrigerant decompressed by the first expansion valve 26 is sent to the receiver 25 for gas-liquid separation. The gas refrigerant separated in the receiver 25 is sent to the suction pipe 31 through the receiver gas vent pipe 30 by opening the receiver gas vent valve 30a. Further, the liquid refrigerant separated from the gas and liquid in the receiver 25 is sent to the outdoor heat exchanger 23.

  The low-pressure liquid refrigerant sent to the outdoor heat exchanger 23 evaporates by exchanging heat with outdoor air supplied as a heating source by the outdoor fan 36 in the outdoor heat exchanger 23 to become a low-pressure gas refrigerant. .

  The low-pressure refrigerant evaporated in the outdoor heat exchanger 23 is sent to the suction pipe 31 through the four-way switching valve 22, merges with the gas refrigerant flowing in from the receiver degassing pipe 30, and sucked into the compressor 21 again. Is done.

(3) Stop control When stopping the cooling operation or the heating operation, it is possible to suppress the inflow of the liquid refrigerant to the suction side of the compressor 21 and to protect the compressor 21 or to restart the operation quickly. In addition, it is preferable to perform control for forcibly storing the liquid refrigerant in the receiver 25.

  Here, when the volume of the outdoor heat exchanger 23 and the liquid refrigerant pipe 35 is large, even if the forced liquid reservoir control to the receiver 25 cannot be sufficiently performed, the outdoor heat exchanger 23 and the liquid Including the amount of liquid refrigerant that accumulates in the refrigerant pipe 35 by chance, the inflow of liquid refrigerant to the suction side of the compressor 21 can be sufficiently suppressed. For this reason, there is little possibility that the protection of the compressor 21 and the rapid resumption of operation will be hindered.

  However, here, the volume of the outdoor heat exchanger 23 may be reduced by adopting a heat exchanger that uses a flat multi-hole tube as the heat transfer tube 231 as the outdoor heat exchanger 23. 23 and the amount of liquid refrigerant that accumulates in the liquid refrigerant pipe 35 is small. For this reason, when the forced liquid reservoir control to the receiver 25 cannot be performed sufficiently, there is a possibility that the inflow of the liquid refrigerant to the suction side of the compressor 21 cannot be sufficiently suppressed. Thereby, there exists a possibility of inhibiting the protection of the compressor 21 and a quick restart of operation.

  Here, R32, which has a very low solubility of refrigerating machine oil under low temperature conditions, is enclosed in the refrigerant circuit 10 as a refrigerant, so that two-layer separation between the refrigerant and the refrigerating machine oil and the resulting insufficient lubrication of the compressor 21 are avoided. Therefore, the refrigerant circuit 10 is not provided with an accumulator (having a larger volume than the small volume accumulator attached to the compressor 21). For this reason, when the operation is resumed, the liquid refrigerant is liable to flow into the suction side of the compressor 21, which may impede the protection of the compressor 21 and the rapid resumption of operation.

  Therefore, here, when the cooling operation or the heating operation is stopped, the two-stage liquid reservoir control of the indoor side liquid reservoir control and the receiver liquid reservoir control is performed as follows. Here, in the indoor side liquid reservoir control, the receiver degassing valve 30a is closed and the first expansion valve 26 is opened to force the refrigerant present on the outdoor heat exchanger 23 side from the first expansion valve 26. It is the control which moves to the indoor heat exchanger 41 side. The receiver liquid reservoir control is a control for forcibly storing the refrigerant in the receiver 25 by opening the receiver gas vent valve 30a and closing the first expansion valve 26 after the indoor liquid reservoir control. Then, after the receiver liquid reservoir control, the receiver gas vent valve 30a is closed and the compressor 21 is stopped.

  Next, cooling stop control and heating stop control will be described with reference to FIGS. Here, FIG. 6 is a flowchart of the cooling stop control. FIG. 7 is a time chart showing operations of the compressor 21, the outdoor fan 36, the indoor fan 42, the first expansion valve 26, and the receiver degassing valve 30a during the cooling stop control. FIG. 8 is a flowchart of the heating stop control. FIG. 9 is a time chart showing the operations of the compressor 21, the outdoor fan 36, the indoor fan 42, the four-way switching valve 22, the first expansion valve 26, and the receiver gas vent valve 30a during the heating stop control. The cooling stop control and the heating stop control described below are performed by the control unit 8 as in the above basic operation.

<Cooling stop control>
First, cooling stop control performed when cooling operation is stopped will be described.

-Step ST1-
When a cooling operation stop command is issued by a thermo-off, a remote controller (not shown), or the like, the control unit 8 first performs preparation control in step ST1 (see the processing during time t1 in FIGS. 6 and 7). . In step ST1, for example, the rotational speed of the compressor 21 is gradually decreased. At this time, the operation of the outdoor fan 36 and the indoor fan 42 is continued. However, the indoor fan 42 is set to the minimum air volume during the cooling stop control in steps ST1 to ST4 in order to avoid a cold draft into the room. The operation of the outdoor fan 36 and the indoor fan 42 in the cooling stop control is not limited to those described in steps ST1 to ST4.

  And after performing preparation control of step ST1, it transfers to the process of step ST2.

-Step ST2-
Next, the control unit 8 performs indoor-side liquid reservoir control in step ST2 (see the process during the time t2 in FIGS. 6 and 7). The indoor-side liquid reservoir control is started by closing the receiver degassing valve 30a and opening the first expansion valve 26. That is, in the indoor side liquid reservoir control, the outdoor gas exchanger 30a is opened while the first expansion valve 26 is opened while suppressing the liquid reservoir in the receiver 25 by closing the receiver degassing valve 30a. The refrigerant present on the 23 side is forcibly accumulated on the indoor heat exchanger 41 side (mainly the liquid refrigerant communication pipe 5) from the receiver 25 and the first expansion valve 26. Then, the liquid refrigerant can be further stored in the portion closer to the outdoor heat exchanger 23 than the first expansion valve 26 such as the receiver 25 of the refrigerant circuit 10 as much as the indoor liquid storage control is performed. As described above, prior to the liquid storage in the receiver 25 described later (that is, the receiver liquid storage control in step ST3), a portion where the liquid refrigerant on the indoor heat exchanger 41 side flows from the receiver 25 of the refrigerant circuit 10 is used. Thus, the refrigerant can be stored. In step ST2, the opening degree of the first expansion valve 26 is set to the indoor side liquid reservoir opening degree Xls which is smaller than the full opening. Moreover, in step ST2, the refrigerant | coolant condensing capability in the outdoor heat exchanger 23 is improved, and it sends to the part through which the liquid refrigerant by the side of the indoor heat exchanger 41 flows rather than the receiver 25 of the refrigerant circuit 10 in the outdoor heat exchanger 23. In order to increase the amount of liquid refrigerant, the outdoor fan 36 is set to the maximum air volume. Here, the indoor fan 42 is set to the minimum air volume, but the indoor fan 42 may be stopped. Then, when the liquid storage to the indoor side is completed, the receiver degassing valve 30a is opened, and the first expansion valve 26 is fully closed.

  And after performing indoor side liquid reservoir control of step ST2, it transfers to the process of step ST3.

-Step ST3-
Next, the control part 8 performs receiver liquid reservoir control of step ST3 (refer the process between time t3 of FIG.6 and FIG.7). The receiver liquid reservoir control is substantially started when the receiver gas vent valve 30a is opened and the first expansion valve 26 is fully closed at the end of the indoor side liquid reservoir control in step ST2. The That is, in the receiver liquid reservoir control, the outdoor heat exchanger 23 is set by closing the first expansion valve 26 while encouraging liquid storage in the receiver 25 by opening the receiver gas vent valve 30a. The refrigerant present on the side is forcibly stored in the receiver 25. Accordingly, the refrigerant can be stored in the portion (mainly, the liquid refrigerant pipe 35) through which the liquid refrigerant flows closer to the indoor heat exchanger 23 than the receiver 25 of the refrigerant circuit 10 and in the receiver 25. Further, in step ST3, similarly to the indoor side liquid reservoir control in step ST2, the refrigerant condensation capacity in the outdoor heat exchanger 23 is increased, and the amount of liquid refrigerant sent into the receiver 25 in the outdoor heat exchanger 23 is increased. In order to increase, the outdoor fan 36 is set to the maximum air volume. When the liquid storage in the receiver 25 is completed, the cooling operation is performed by stopping the compressor 21 while closing the receiver degassing valve 30a so that the refrigerant is prevented from flowing out from the receiver 25 as much as possible. Can be stopped. That is, here, the forced liquid reservoir control including the receiver 25 can be sufficiently performed when the cooling operation is stopped, and the liquid refrigerant can be prevented from flowing into the suction side of the compressor 21.

  And after performing receiver liquid reservoir control of step ST3, it transfers to the process of step ST4.

-Step ST4-
Next, the control unit 8 performs pressure equalization control in step ST4, that is, control for reducing the pressure in the high-pressure portion of the refrigerant circuit 10 (see the process during time t4 in FIGS. 6 and 7). In step ST4, the operation of the outdoor fan 36 is continued even after the liquid storage in the receiver 25 is completed and the compressor 21 is stopped. Thereby, the pressure of the refrigerant | coolant in the outdoor heat exchanger 23 falls, and the pressure in the high voltage | pressure part (here the part from the discharge side of the compressor 21 to the 1st expansion valve 26) falls. When this pressure equalization control ends, the outdoor fan 36 and the indoor fan 42 are stopped.

  In the cooling stop control described above, when the cooling operation is stopped, the refrigerant including the receiver 25 is compulsorily performed by performing the two-stage liquid reservoir control of the indoor side liquid reservoir control and the receiver liquid reservoir control. The liquid reservoir can be sufficiently controlled. Thereby, it is possible to protect the compressor 21 and to restart the operation quickly. In particular, here, although a heat exchanger that uses a flat multi-hole tube as the heat transfer tube 231 is adopted as the outdoor heat exchanger 23, two-stage liquids of indoor liquid reservoir control and receiver liquid reservoir control are used. By performing the reservoir control, the forced liquid reservoir control including the receiver 25 can be sufficiently performed. Here, no accumulator is provided on the suction side of the compressor 21, but even in such a case, the liquid refrigerant is prevented from flowing into the suction side of the compressor 21 when the cooling operation is resumed. Can do.

<Heating stop control>
Next, heating stop control performed when stopping the heating operation will be described.

  Here, as the outdoor heat exchanger 23, heat exchange using a flat multi-hole tube as the heat transfer tube 231 is employed. For this reason, when the heating operation is stopped by a thermo-off, a command from a remote controller, or the like, if the compressor 21 is stopped while the four-way switching valve 22 remains in the heating cycle state, the refrigerant circuit for stopping the heating operation 10, the liquid refrigerant accumulated in the heat transfer tube 231 (flat multi-hole tube) of the outdoor heat exchanger 23 is easily pushed to the suction side of the compressor 21 by the flow of the refrigerant in the outdoor heat exchanger 23, and then the heating operation is resumed. The compressor 21 may inhale the liquid refrigerant.

  Therefore, here, in the heating stop control, the four-way switching valve 22 is set to the heating cycle when the heating operation is stopped in consideration of the refrigerant behavior after the stop of the heating operation due to the type of the heat transfer tube 231 as described below. After switching from the state to the cooling cycle state, the indoor side liquid reservoir control and the receiver liquid reservoir control similar to the cooling stop control are performed, and then the compressor 21 is stopped.

-Step ST1-
When a heating operation stop command is given by a thermo-off, a remote controller (not shown), or the like, the control unit 8 first performs a preparation control in step ST1 (see the process during time t1 in FIGS. 8 and 9). . In addition, since the processing content of step ST1 is the same as that of step ST1 of cooling stop control, description is abbreviate | omitted here.

  And after performing preparation control of step ST1, it transfers to the process of step ST5.

-Step ST5-
Next, the control unit 8 performs the four-way switching valve switching control in step ST2, that is, the control for switching the four-way switching valve 22 from the heating cycle state to the cooling cycle state (between time t2 in FIGS. 8 and 9). Processing). In step ST2, first, the first expansion valve 26 is fully closed. Here, for example, when the four-way switching valve 22 is switched from the heating cycle state to the cooling cycle state with the first expansion valve 26 open, the outdoor heat exchanger 23 side to the indoor heat exchanger 41 side through the first expansion valve 26. As a result, the flow of the refrigerant toward the abruptly occurs. Thereby, the liquid refrigerant accumulated in the indoor heat exchanger 41 functioning as a refrigerant radiator during the heating operation may be sent to the suction side of the compressor 21. However, here, as described above, the first expansion valve 26 is fully closed before the four-way switching valve 22 is switched from the heating cycle state to the cooling cycle state. Even when switching to the cooling cycle state, the flow of refrigerant from the outdoor heat exchanger 23 side to the indoor heat exchanger 41 side does not occur through the first expansion valve 26, and the room functioned as a refrigerant radiator during heating operation. The liquid refrigerant accumulated in the heat exchanger 41 is not sent to the suction side of the compressor 21.

  Then, after the first expansion valve 26 is fully closed, the four-way switching valve 22 is switched from the heating cycle state to the cooling cycle state. As a result, in the state where the first expansion valve 26 is fully closed, the same refrigerant flow as in the cooling operation is generated, and the liquid refrigerant can be stored in the receiver 25. Here, the receiver degassing valve 30a is also opened.

  Then, after performing the four-way switching valve switching control in step ST2, that is, after the four-way switching valve 22 is switched from the heating cycle state to the cooling cycle state, the process proceeds to step ST3.

-Step ST2-
Next, the control unit 8 performs indoor-side liquid reservoir control in step ST2 (see the processing during the time t2 in FIGS. 8 and 9). The indoor-side liquid reservoir control is started by closing the receiver degassing valve 30a opened in step ST2 and opening the fully expanded first expansion valve 26 in step ST2. In addition, since the processing content of step ST2 is the same as that of step ST2 of cooling stop control, description is abbreviate | omitted here.

  And after performing indoor side liquid reservoir control of step ST2, it transfers to the process of step ST3.

-Step ST3-
Next, the control part 8 performs receiver liquid reservoir control of step ST3 (refer the process between time t3 of FIG.8 and FIG.9). In addition, since the processing content of step ST3 is the same as that of step ST3 of cooling stop control, description is abbreviate | omitted here.

  And after performing receiver liquid reservoir control of step ST3, it transfers to the process of step ST4.

-Step ST4-
Next, the control unit 8 performs pressure equalization control in step ST4, that is, control for reducing the pressure in the high pressure portion of the refrigerant circuit 10 (see the process during the time t4 in FIGS. 8 and 9). In addition, since the processing content of step ST4 is the same as that of step ST3 of cooling stop control, description is abbreviate | omitted here.

  In the heating stop control described above, similarly to the cooling stop control, when the heating operation is stopped, the receiver 25 is controlled by performing the two-stage liquid reservoir control of the indoor side liquid reservoir control and the receiver liquid reservoir control. The compulsory liquid reservoir control of the included refrigerant can be sufficiently performed. Thereby, it is possible to protect the compressor 21 and to restart the operation quickly.

(4) Modified Example In the above embodiment (see FIG. 1), in the refrigerant circuit 10, the first expansion valve 26 is provided only between the receiver 25 and the liquid side closing valve 27 (that is, on the indoor heat exchanger 41 side). Is provided. Thus, the receiver 25 has a function of storing high-pressure refrigerant in the refrigeration cycle after it becomes high pressure in the refrigeration cycle during cooling operation and radiates heat in the outdoor heat exchanger 23. In addition, the receiver 25 has a function of storing a low-pressure refrigerant in the refrigeration cycle after being reduced in pressure in the refrigeration cycle during the heating operation and reduced in pressure in the first expansion valve 26.

  On the other hand, here, as shown in FIG. 10, in the refrigerant circuit 10, not only the first expansion valve 26 but also the outdoor heat exchanger 23 and the receiver 25 (that is, the outdoor heat exchanger 23 side). In addition, a second expansion valve 24 is further provided. As a result, the receiver 25 has a function of accumulating refrigerant having an intermediate pressure between the high pressure and the low pressure in the refrigeration cycle (intermediate pressure in the refrigeration cycle) during both the cooling operation and the heating operation.

  Hereinafter, the configuration, basic operation, and stop control of the air conditioner 1 having the refrigerant circuit 10 provided with the second expansion valve 24 and the first expansion valve 26 so as to sandwich the receiver 25 will be described.

<Configuration of air conditioner>
The air conditioning apparatus 1 is an apparatus that can cool and heat a room such as a building by performing a vapor compression refrigeration cycle, as in the above embodiment. The air conditioner 1 is mainly configured by connecting an outdoor unit 2 and an indoor unit 4. Here, the outdoor unit 2 and the indoor unit 4 are connected via a liquid refrigerant communication tube 5 and a gas refrigerant communication tube 6. That is, the vapor compression refrigerant circuit 10 of the air conditioner 1 is configured by connecting the outdoor unit 2 and the indoor unit 4 via the refrigerant communication pipes 5 and 6. In this refrigerant circuit 10 as well, in the same manner as in the above-described embodiment, R32, which is a kind of HFC refrigerant, is enclosed as a refrigerant, and as a refrigerating machine oil, an ether-based synthesis with extremely low solubility in R32 at low temperature conditions. Oil, mineral oil that is incompatible with R32, alkylbenzene-based synthetic oil, or the like is enclosed.

-Indoor unit-
The indoor unit 4 is installed indoors and constitutes a part of the refrigerant circuit 10. The indoor unit 4 mainly has an indoor heat exchanger 41. In addition, since the structure of the apparatus and sensors which comprise the indoor unit 4 is the same as that of said embodiment, description is abbreviate | omitted here.

-Outdoor unit-
The outdoor unit 2 is installed outside and constitutes a part of the refrigerant circuit 10. The outdoor unit 2 mainly includes a compressor 21, a four-way switching valve 22, an outdoor heat exchanger 23, a second expansion valve 24, a receiver 25, a first expansion valve 26, and a liquid side closing valve 27. The gas-side closing valve 28 and the receiver gas vent pipe 30 are provided. In addition, the structure of the compressor 21, the four-way switching valve 22, the outdoor heat exchanger 23, the liquid side closing valve 27, the gas side closing valve 28, sensors, and the outdoor side control part 38 is the same as that of said embodiment. Therefore, the description is omitted here.

  And here, the 2nd expansion valve 24 which is not provided in said embodiment is provided. The second expansion valve 24 is a valve that reduces the high-pressure refrigerant in the refrigeration cycle radiated in the outdoor heat exchanger 23 to the intermediate pressure in the refrigeration cycle during the cooling operation. The second expansion valve 24 is a valve for reducing the intermediate pressure refrigerant in the refrigeration cycle stored in the receiver 25 to a low pressure in the refrigeration cycle during heating operation. The second expansion valve 24 is provided in a portion of the liquid refrigerant pipe 35 near the outdoor heat exchanger 23. Here, an electric expansion valve is used as the second expansion valve 24.

  By providing the second expansion valve 24 as described above, the receiver 25 functions as a container capable of storing an intermediate-pressure refrigerant in the refrigeration cycle. The first expansion valve 26 functions as a valve for reducing the intermediate-pressure refrigerant in the refrigeration cycle stored in the receiver 25 to a low pressure in the refrigeration cycle during the cooling operation, and radiates heat in the outdoor heat exchanger 23 during the heating operation. It functions as a valve for reducing the high-pressure refrigerant in the refrigeration cycle to the intermediate pressure in the refrigeration cycle. Further, the receiver degassing pipe 30 functions as a refrigerant pipe that guides the intermediate-pressure gas refrigerant in the refrigeration cycle accumulated in the receiver 25 to the suction pipe 31 of the compressor 21.

-Refrigerant communication pipe-
Since the refrigerant communication tubes 5 and 6 are the same as those in the above embodiment, the description thereof is omitted here.

  As described above, the refrigerant circuit 10 of the air conditioner 1 is configured by connecting the outdoor unit 2, the indoor unit 4, and the refrigerant communication pipes 5 and 6. The air conditioner 1 circulates refrigerant in the order of the compressor 21, the outdoor heat exchanger 23, the second expansion valve 24, the receiver 25, the first expansion valve 26, and the indoor heat exchanger 41, and drives the outdoor fan 36. Cooling operation is performed. In addition, the air conditioner 1 switches the four-way switching valve 22 to the heating cycle state, whereby the compressor 21, the indoor heat exchanger 41, the first expansion valve 26, the receiver 25, the second expansion valve 24, and the outdoor heat exchange. The refrigerant is circulated in the order of the unit 23 and the outdoor fan 36 is driven to perform the heating operation. The refrigerant circuit 10 has a receiver degassing valve 30 a that can be controlled to open and close, and is provided with a receiver degassing pipe 30 that guides the gas refrigerant accumulated in the receiver 25 to the suction side of the compressor 21. . The outdoor heat exchanger 23 is a heat exchanger that uses a flat multi-hole tube as the heat transfer tube 231.

-Control unit-
The air conditioner 1 controls each device of the outdoor unit 2 and the indoor unit 4 by the control unit 8 including the indoor side control unit 44 and the outdoor side control unit 38 as in the above embodiment. Can be done. As shown in FIG. 11, the control unit 8 is connected so as to receive detection signals from the various sensors 51 to 59 and the like, and various devices and valves 21 a and 22 based on the detection signals and the like. , 24, 26, 30a, 37, 43, etc. are connected so that they can be controlled.

<Basic operation of air conditioner>
Next, the basic operation (operation excluding stop control described later) of the air conditioner 1 will be described with reference to FIG. The air conditioner 1 can perform a cooling operation and a heating operation as a basic operation, as in the above embodiment.

-Cooling operation-
During the cooling operation, the four-way switching valve 22 is switched to a cooling cycle state (a state indicated by a solid line in FIG. 11).

  In the refrigerant circuit 10, the low-pressure gas refrigerant in the refrigeration cycle is sucked into the compressor 21 and is discharged after being compressed to a high pressure in the refrigeration cycle.

  The high-pressure gas refrigerant discharged from the compressor 21 is sent to the outdoor heat exchanger 23 through the four-way switching valve 22.

  The high-pressure gas refrigerant sent to the outdoor heat exchanger 23 performs heat exchange with the outdoor air supplied as a cooling source by the outdoor fan 36 in the outdoor heat exchanger 23 to dissipate heat to become a high-pressure liquid refrigerant. .

  The high-pressure liquid refrigerant that has radiated heat in the outdoor heat exchanger 23 is sent to the second expansion valve 24. The high-pressure liquid refrigerant sent to the second expansion valve 24 is reduced to an intermediate pressure in the refrigeration cycle by the second expansion valve 24. The intermediate pressure refrigerant decompressed by the second expansion valve 24 is sent to the receiver 25 for gas-liquid separation. The gas refrigerant separated in the receiver 25 is sent to the suction pipe 31 through the receiver gas vent pipe 30 by opening the receiver gas vent valve 30a. Further, the liquid refrigerant that has been gas-liquid separated in the receiver 25 is sent to the first expansion valve 26.

  The intermediate pressure liquid refrigerant sent to the first expansion valve 26 is depressurized by the first expansion valve 26 to a low pressure in the refrigeration cycle. The refrigerant decompressed by the first expansion valve 26 is sent to the indoor heat exchanger 41 through the liquid side closing valve 27 and the liquid refrigerant communication pipe 5.

  The low-pressure refrigerant sent to the indoor heat exchanger 41 evaporates by exchanging heat with indoor air supplied as a heating source by the indoor fan 42 in the indoor heat exchanger 41. As a result, the room air is cooled and then supplied to the room to cool the room.

  The low-pressure gas refrigerant evaporated in the indoor heat exchanger 41 is sent to the suction pipe 31 through the gas refrigerant communication pipe 6, the gas side closing valve 28 and the four-way switching valve 22, and flows into the receiver gas vent pipe 30. The refrigerant merges with the refrigerant and is sucked into the compressor 21 again.

-Heating operation-
During the heating operation, the four-way switching valve 22 is switched to the heating cycle state (state indicated by the broken line in FIG. 10).

  In the refrigerant circuit 10, the low-pressure gas refrigerant in the refrigeration cycle is sucked into the compressor 21 and is discharged after being compressed to a high pressure in the refrigeration cycle.

  The high-pressure gas refrigerant discharged from the compressor 21 is sent to the indoor heat exchanger 41 through the four-way switching valve 22, the gas side closing valve 28 and the gas refrigerant communication pipe 6.

  The high-pressure gas refrigerant sent to the indoor heat exchanger 41 radiates heat by exchanging heat with indoor air supplied as a cooling source by the indoor fan 42 in the indoor heat exchanger 41 to become a high-pressure liquid refrigerant. . Thereby, indoor air is heated, and indoor heating is performed by being supplied indoors after that.

  The high-pressure liquid refrigerant radiated by the indoor heat exchanger 41 is sent to the first expansion valve 26 through the liquid refrigerant communication pipe 5 and the liquid side closing valve 27.

  The high-pressure liquid refrigerant sent to the first expansion valve 26 is depressurized by the first expansion valve 26 to an intermediate pressure in the refrigeration cycle. The intermediate pressure refrigerant decompressed by the first expansion valve 26 is sent to the receiver 25 for gas-liquid separation. The gas refrigerant separated in the receiver 25 is sent to the suction pipe 31 through the receiver gas vent pipe 30 by opening the receiver gas vent valve 30a. Further, the liquid refrigerant that has been gas-liquid separated in the receiver 25 is sent to the second expansion valve 24. The intermediate-pressure liquid refrigerant sent to the second expansion valve 24 is depressurized by the second expansion valve 24 to a low pressure in the refrigeration cycle. The low-pressure refrigerant decompressed by the second expansion valve 24 is sent to the outdoor heat exchanger 23.

  The low-pressure liquid refrigerant sent to the outdoor heat exchanger 23 evaporates by exchanging heat with outdoor air supplied as a heating source by the outdoor fan 36 in the outdoor heat exchanger 23 to become a low-pressure gas refrigerant. .

  The low-pressure refrigerant evaporated in the outdoor heat exchanger 23 is sent to the suction pipe 31 through the four-way switching valve 22, merges with the gas refrigerant flowing in from the receiver degassing pipe 30, and sucked into the compressor 21 again. Is done.

<Stop control>
In the air conditioner 1 in which the configuration of the refrigerant circuit 10 is arranged so that the receiver 25 is sandwiched between the second expansion valve 24 and the first expansion valve 26, the above-described embodiment is similar to the above embodiment. When the cooling operation or the heating operation is stopped by a thermo-off or a command from a remote controller, the two-stage liquid reservoir control such as the indoor side liquid reservoir control and the receiver liquid reservoir control is performed.

-Cooling stop control (see Figs. 6 and 12)-
When a cooling operation stop command is issued by a thermo-off, a remote controller (not shown), or the like, the control unit 8 first performs preparation control in step ST1 (refer to processing during time t1 in FIGS. 6 and 12). . In addition, since the processing content of step ST1 is the same as that of step ST1 of said embodiment, description is abbreviate | omitted here. And after performing preparation control of step ST1, it transfers to the process of step ST2.

  Next, the control unit 8 performs indoor-side liquid reservoir control in step ST2 (see the processing during the time t2 in FIGS. 6 and 12). The indoor-side liquid reservoir control is started by closing the receiver gas vent valve 30a and opening the first expansion valve 26, as in step ST2 of the above embodiment. Further, here, the second expansion valve 24 is fully opened. This creates a situation where the refrigerant is easily introduced into the receiver 25 from the outdoor heat exchanger 23 side through the second expansion valve 24. And after performing indoor side liquid reservoir control of step ST2, it transfers to the process of step ST3.

  Next, the control part 8 performs receiver liquid reservoir control of step ST3 (refer the process between time t3 of FIG.6 and FIG.12). In the receiver liquid reservoir control, similarly to step ST3 of the above embodiment, the receiver degassing valve 30a is opened at the end of the indoor side liquid reservoir control in step ST2, and the first expansion valve 26 is It starts substantially by being fully closed. When the liquid storage in the receiver 25 is completed, the cooling operation can be stopped by closing the receiver gas vent valve 30a and stopping the compressor 21 as in step ST3 of the above embodiment. In addition, here, the second expansion valve 24 is fully closed. Thereby, it can suppress reliably that a refrigerant | coolant flows out from the receiver 25 inside. And after performing receiver liquid reservoir control of step ST3, it transfers to the process of step ST4.

  Next, the control unit 8 performs pressure equalization control in step ST4, that is, control for reducing the pressure in the high-pressure portion of the refrigerant circuit 10 (see the process during time t4 in FIGS. 6 and 12). Note that the processing content of step ST4 is the same as that of step ST4 of the above-described embodiment, and thus description thereof is omitted here.

  In the cooling stop control described above, similarly to the above-described embodiment, when the cooling operation is stopped, the receiver 25 is controlled by performing two-stage liquid reservoir control, that is, indoor-side liquid reservoir control and receiver liquid reservoir control. This makes it possible to sufficiently perform forcible liquid reservoir control including refrigerant. Thereby, it is possible to protect the compressor 21 and to restart the operation quickly. In addition, here, the second expansion valve 24 is opened during the indoor side liquid reservoir control and the receiver liquid reservoir control, so that the liquid refrigerant closer to the indoor heat exchanger 41 than the receiver 25 of the refrigerant circuit 10 is. It is possible to reliably prevent the refrigerant from flowing out of the receiver 25 by storing the refrigerant in the portion where the refrigerant flows and in the receiver 25 and closing the receiver after the receiver liquid reservoir control. Thereby, the refrigerant | coolant collected in the receiver 25 by receiver liquid reservoir control can be reliably hold | maintained in the receiver 25. FIG.

-Heating stop control (see Figs. 8 and 13)-
When a heating operation stop command is given by a thermo-off, a remote controller (not shown), or the like, the control unit 8 first performs preparation control in step ST1 (see processing during time t1 in FIGS. 8 and 13). . In addition, since the processing content of step ST1 is the same as that of step ST1 of said embodiment, description is abbreviate | omitted here. And after performing preparation control of step ST1, it transfers to the process of step ST5.

  Next, the control unit 8 performs the four-way switching valve switching control in step ST5, that is, the control for switching the four-way switching valve 22 from the heating cycle state to the cooling cycle state (between time t5 in FIGS. 8 and 13). Processing). In step ST5, first, as in step ST2 of the above embodiment, the first expansion valve 26 is fully closed. Further, here, the second expansion valve 24 is fully opened. This creates a situation where the refrigerant is easily introduced into the receiver 25 from the outdoor heat exchanger 23 side through the second expansion valve 24. Since the other processing contents of step ST5 are the same as step ST5 of the above embodiment, the description thereof is omitted here. Then, after performing the four-way switching valve switching control in step ST5, that is, after the four-way switching valve 22 is switched from the heating cycle state to the cooling cycle state, the process proceeds to step ST2.

  Next, the control part 8 performs indoor side liquid reservoir control of step ST2 (refer the process between time t2 of FIG.8 and FIG.13). The indoor-side liquid reservoir control is started by closing the receiver gas vent valve 30a and opening the first expansion valve 26, as in step ST2 of the above embodiment. Further, here, the second expansion valve 24 is fully opened. This creates a situation where the refrigerant is easily introduced into the receiver 25 from the outdoor heat exchanger 23 side through the second expansion valve 24. And after performing indoor side liquid reservoir control of step ST2, it transfers to the process of step ST3.

  Next, the control part 8 performs receiver liquid reservoir control of step ST3 (refer the process between time t3 of FIG.8 and FIG.13). In the receiver liquid reservoir control, similarly to step ST3 of the above embodiment, the receiver degassing valve 30a is opened at the end of the indoor side liquid reservoir control in step ST2, and the first expansion valve 26 is It starts substantially by being fully closed. When the liquid storage in the receiver 25 is completed, the cooling operation can be stopped by closing the receiver gas vent valve 30a and stopping the compressor 21 as in step ST3 of the above embodiment. In addition, here, the second expansion valve 24 is fully closed. Thereby, it can suppress reliably that a refrigerant | coolant flows out from the receiver 25 inside. And after performing receiver liquid reservoir control of step ST3, it transfers to the process of step ST4.

  Next, the control unit 8 performs pressure equalization control in step ST4, that is, control for reducing the pressure in the high-pressure portion of the refrigerant circuit 10 (see the process during time t4 in FIGS. 8 and 13). Note that the processing content of step ST4 is the same as that of step ST4 of the above-described embodiment, and thus description thereof is omitted here.

  Also in the heating stop control described above, similarly to the above-described embodiment, when the heating operation is stopped, the two-stage liquid reservoir control of the indoor side liquid reservoir control and the receiver liquid reservoir control is performed. This makes it possible to sufficiently perform forcible liquid reservoir control including refrigerant. Thereby, it is possible to protect the compressor 21 and to restart the operation quickly. In addition, here, the second expansion valve 24 is opened during the indoor side liquid reservoir control and the receiver liquid reservoir control, so that the liquid refrigerant closer to the indoor heat exchanger 41 than the receiver 25 of the refrigerant circuit 10 is. It is possible to reliably prevent the refrigerant from flowing out of the receiver 25 by storing the refrigerant in the portion where the refrigerant flows and in the receiver 25 and closing the receiver after the receiver liquid reservoir control. Thereby, the refrigerant | coolant collected in the receiver 25 by receiver liquid reservoir control can be reliably hold | maintained in the receiver 25. FIG.

  The present invention has a refrigerant circuit configured by connecting a compressor, an outdoor heat exchanger, a receiver, a first expansion valve, and an indoor heat exchanger, the compressor, the outdoor heat exchanger, the receiver, The present invention can be widely applied to an air conditioner that can circulate refrigerant in the order of the first expansion valve and the indoor heat exchanger.

DESCRIPTION OF SYMBOLS 1 Air conditioning apparatus 10 Refrigerant circuit 21 Compressor 23 Outdoor heat exchanger 24 2nd expansion valve 25 Receiver 26 1st expansion valve 30 Receiver degassing pipe 30a Receiver degassing valve 36 Outdoor fan 41 Indoor heat exchanger 231 Heat exchanger tube

JP 2011-80649 A

Claims (4)

It has a refrigerant circuit (10) configured by connecting a compressor (21), an outdoor heat exchanger (23), a receiver (25), a first expansion valve (26), and an indoor heat exchanger (41). In the air conditioner capable of circulating the refrigerant in the order of the compressor, the outdoor heat exchanger, the receiver, the first expansion valve, and the indoor heat exchanger,
The refrigerant circuit has a receiver degassing valve (30a) that can be controlled to open and close, and a receiver degassing pipe (30) for guiding the gas refrigerant accumulated in the receiver to the suction side of the compressor. Provided,
When the operation is stopped, the receiver degassing valve is closed and the first expansion valve is opened so that the refrigerant present on the outdoor heat exchanger side with respect to the first expansion valve is forcibly forced into the indoor space. The indoor side liquid reservoir control to be moved to the heat exchanger side is performed, and after the indoor side liquid reservoir control, the receiver degassing valve is opened and the first expansion valve is closed to forcibly supply the refrigerant to the receiver. To perform receiver liquid reservoir control, and then close the receiver gas vent valve and stop the compressor,
Air conditioner (1). The refrigerant circuit (10) further includes a second expansion valve (24) between the outdoor heat exchanger (23) and the receiver (25),
The second expansion valve is opened during the indoor liquid reservoir control and the receiver liquid reservoir control, and is closed after the receiver liquid reservoir control is completed.
The air conditioner (1) according to claim 1. An outdoor fan (36) for supplying outdoor air to the outdoor heat exchanger (23) is further provided;
The outdoor fan is set to a maximum air volume at the time of the indoor side liquid reservoir control and the receiver liquid reservoir control.
The air conditioner (1) according to claim 1 or 2. The outdoor heat exchanger (23) is a heat exchanger that uses a flat multi-hole tube as the heat transfer tube (231).
The air conditioning apparatus (1) according to any one of claims 1 to 3.

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