JP2016133257A - Air-conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air-conditioner for switchably performing a heating operation and a reverse-cycle defrosting operation, capable of suppressing the occurrence of frost remaining unmelted and adhering to a liquid-side end section of an outdoor heat exchanger and a periphery thereof after the reverse-cycle defrosting operation, and efficiently defrosting the outdoor heat exchanger.SOLUTION: A refrigerant circuit (10) of an air-conditioner (1) further has a receiver (25) connected between an indoor heat exchanger (41) and an expansion valve (24). A control unit (8) that controls a compressor (21) and the expansion valve (41) performs a defrosting operation using the receiver for defrosting a liquid-side end section (23b) of an outdoor heat exchanger (23), before the start of a reverse-cycle defrosting operation, such that refrigerant is delivered from the receiver (25) toward the outdoor heat exchanger (23) by means of a differential pressure between the refrigerant within the receiver (25) and the refrigerant within the outdoor heat exchanger (23) by stopping the compressor (21) and opening the expansion valve (24).SELECTED DRAWING: Figure 5

Description

  The present invention relates to an air conditioner, and more particularly to an air conditioner that performs switching between heating operation and reverse cycle defrosting operation.

  Conventionally, as shown in Patent Document 1 (Japanese Patent Laid-Open No. 7-174440), there is an air conditioner that performs switching between heating operation and reverse cycle defrosting operation. The air conditioner includes a refrigerant circuit configured by connecting a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger, and a control unit that controls the compressor and the expansion valve. . Then, the control unit heats the room by circulating the refrigerant in the order of the compressor, the indoor heat exchanger, the expansion valve, and the outdoor heat exchanger, and the compressor, the outdoor heat exchanger, the expansion valve, and the indoor heat exchange. The reverse cycle defrosting operation for defrosting the outdoor heat exchanger by circulating the refrigerant in the order of the units is performed. Specifically, when the defrost start condition indicating that the defrosting of the outdoor heat exchanger is necessary during the heating operation is reached, the defrosting of the outdoor heat exchanger is switched from the heating operation to the reverse cycle defrosting operation. Is supposed to do.

  The reverse cycle defrosting operation is performed by using the gas side end of the outdoor heat exchanger as the refrigerant inlet and the liquid side end of the outdoor heat exchanger as the refrigerant outlet. Is an operation of flowing the refrigerant discharged from the compressor toward the liquid side end. For this reason, in the reverse cycle defrosting operation, the frost attached to the gas side end of the outdoor heat exchanger and the vicinity thereof starts to melt first, and then the frost attached to the intermediate part of the outdoor heat exchanger is melted, The frost adhering to the liquid side end of the outdoor heat exchanger and the vicinity thereof is finally melted. Due to the refrigerant flow in such a reverse cycle defrosting operation, the frost adhering to the liquid side end of the outdoor heat exchanger and its vicinity is likely to occur after the reverse cycle defrosting operation, and the defrosting time Tend to be longer.

  An object of the present invention is to provide an air conditioner that performs switching between heating operation and reverse cycle defrosting operation, in which the frost adhering to the liquid side end of the outdoor heat exchanger and its vicinity after the reverse cycle defrosting operation is removed. The purpose of this is to prevent the outdoor heat exchanger from being defrosted efficiently.

  An air conditioner according to a first aspect includes a refrigerant circuit configured by connecting a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger, and a control unit that controls the compressor and the expansion valve. ,have. The control unit includes a heating operation in which the refrigerant is circulated in the order of the compressor, the indoor heat exchanger, the expansion valve, and the outdoor heat exchanger to heat the room, and the compressor, the outdoor heat exchanger, the expansion valve, and the indoor heat exchanger. A reverse cycle defrosting operation in which refrigerant is circulated in order to defrost the outdoor heat exchanger is switched. Here, the refrigerant circuit further includes a receiver connected between the indoor heat exchanger and the expansion valve. Then, the control unit stops the compressor before starting the reverse cycle defrosting operation when the defrosting start condition indicating that the outdoor heat exchanger needs to be defrosted is reached during the heating operation. In addition, by opening the expansion valve, the refrigerant flows from the receiver toward the outdoor heat exchanger due to the differential pressure between the refrigerant in the receiver and the refrigerant in the outdoor heat exchanger, thereby defrosting the liquid side end of the outdoor heat exchanger. The receiver defrosting operation is performed.

  Here, as described above, a receiver is provided between the indoor heat exchanger and the expansion valve, and before starting the reverse cycle defrosting operation, the operation of stopping the compressor and opening the expansion valve is performed. Including the receiver defrosting operation. That is, here, the refrigerant pressure (refrigeration cycle) in the receiver is started before the reverse cycle defrosting operation is started by performing the operation of stopping the compressor and opening the expansion valve in the refrigerant circuit that has been performing the heating operation. The pressure of the refrigerant in the outdoor heat exchanger (pressure close to the low pressure of the refrigeration cycle) is used to flow high-temperature refrigerant from the receiver to the outdoor heat exchanger. . In particular, here, since the refrigerant in the receiver in which a large amount of refrigerant is accumulated is used, the differential pressure is easily maintained even when the compressor is stopped. Can flow. For this reason, here, before starting the reverse cycle defrosting operation, the frost adhering to the liquid side end portion of the outdoor heat exchanger that becomes the outlet of the refrigerant during the reverse cycle defrosting operation and its vicinity is previously melted. And then the reverse cycle defrosting operation can be started.

  Thereby, here, the occurrence of unmelted frost adhering to the liquid side end of the outdoor heat exchanger and the vicinity thereof after the reverse cycle defrosting operation is suppressed, and the outdoor heat exchanger is efficiently defrosted. be able to. Moreover, compared with the case where an outdoor heat exchanger is defrosted only by reverse cycle defrosting operation, an outdoor heat exchanger can be defrosted in a short time.

  Here, even when switching between the heating operation and the reverse cycle defrosting operation of Patent Document 1 described above, an operation of temporarily stopping the compressor is performed. The purpose is to reduce sound, and the compressor is merely stopped for a very short time. For this reason, the operation of temporarily stopping the compressor in Patent Document 1 is different from the above-described receiver-based defrosting operation in that the frost adhering to the liquid side end of the outdoor heat exchanger and its vicinity is melted. It is difficult to get substantially.

  The air-conditioning apparatus according to the second aspect is the air-conditioning apparatus according to the first aspect, wherein the controller uses the receiver defrost until the control unit eliminates the differential pressure between the refrigerant in the receiver and the refrigerant in the outdoor heat exchanger. Do the driving. Note that “until the pressure difference disappears” means that the pressure difference between the refrigerant in the receiver and the refrigerant in the outdoor heat exchanger falls within the range of 0 to 0.1 MPa.

  Here, since the compressor is stopped for a long time as compared with the temporary stop of the compressor in Patent Document 1, the liquid side end portion of the outdoor heat exchanger and the vicinity thereof are sufficiently defrosted. It can be carried out.

  An air conditioner according to a third aspect is the air conditioner according to the first or second aspect, wherein the receiver is connected to a receiver pressure adjustment pipe for extracting the refrigerant in the gas state to the suction side of the compressor. The receiver pressure adjustment pipe is provided with a receiver pressure adjustment valve. And a control part closes a receiver pressure regulation valve, when performing receiver utilization defrost operation.

  If a receiver pressure adjustment pipe is provided together with the receiver so that the refrigerant is extracted to the suction side of the compressor, the refrigerant pressure in the receiver is likely to decrease during the receiver defrosting operation. It may be difficult to maintain the differential pressure with the refrigerant in the heat exchanger, and it may be difficult to ensure the flow of refrigerant from the receiver toward the outdoor heat exchanger.

  Therefore, here, as described above, the receiver pressure adjusting valve is further provided with a receiver pressure adjusting valve, and the receiver pressure adjusting valve is closed when the receiver defrosting operation is performed. For this reason, it is easy to maintain the differential pressure despite the configuration in which the receiver pressure adjusting pipe is provided in the receiver.

  Thereby, although it is the structure which provided the receiver pressure adjustment pipe | tube in the receiver here, it is easy to ensure the flow of the refrigerant | coolant which goes to the outdoor heat exchanger from a receiver, and the defrosting effect by a receiver utilization defrost operation Can be easily obtained.

  The air conditioner according to a fourth aspect is the air conditioner according to any one of the first to third aspects, wherein the controller defrosts the refrigerant in the receiver before starting the receiver defrost operation. Prepare for operation.

  The defrosting effect by the receiver defrosting operation tends to depend on the amount of refrigerant accumulated in the receiver during the receiver defrosting operation.

  Therefore, here, as described above, the amount of refrigerant accumulated in the receiver is increased in advance by performing the defrost preparation operation in which the refrigerant is accumulated in the receiver before the receiver defrosting operation is started. Yes. Here, as the defrost preparation operation, it is conceivable to perform an operation of closing the expansion valve while continuing the operation of the compressor in the refrigerant circuit performing the heating operation. Then, in the receiver defrosting operation that is subsequently performed by such a defrost preparation operation, the differential pressure between the refrigerant in the receiver and the refrigerant in the outdoor heat exchanger is maintained, and the receiver to the outdoor heat exchanger. It is possible to easily secure the flow of the refrigerant to go.

  Thereby, before starting a receiver utilization defrost operation, many refrigerant | coolants can be stored in a receiver here, and the defrost effect by a receiver utilization defrost operation can be heightened.

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

  In the air conditioner according to the first aspect, the defrosting of the outdoor heat exchanger is suppressed by suppressing the occurrence of unmelted frost adhering to and near the liquid side end of the outdoor heat exchanger after the reverse cycle defrosting operation. Can be performed efficiently.

  In the air conditioner according to the second aspect, it is possible to sufficiently defrost the liquid side end portion of the outdoor heat exchanger and the vicinity thereof.

  In the air conditioner according to the third aspect, despite the configuration in which the receiver pressure adjustment pipe is provided in the receiver, it is easy to ensure the flow of refrigerant from the receiver to the outdoor heat exchanger, and the receiver defrosting is performed. It is possible to easily obtain a defrosting effect by driving.

  In the air conditioning apparatus according to the fourth aspect, a large amount of refrigerant is stored in the receiver before starting the receiver defrosting operation, and the defrosting effect by the receiver defrosting operation can be enhanced.

It is a schematic structure figure of the air harmony device concerning a 1st embodiment of the present invention. It is a schematic perspective view of an outdoor heat exchanger. It is a partial expansion perspective view of an outdoor heat exchanger. It is a control block diagram of the air conditioning apparatus of 1st Embodiment. It is a flowchart which shows the switching operation | movement (a receiver utilization defrost operation is included) between heating operation and reverse cycle defrost operation. It is a figure which shows the compressor and valve state in the heating operation of 1st Embodiment, the flow of a refrigerant | coolant, and the refrigerant | coolant amount in a receiver. It is a figure which shows the compressor and valve state in the receiver utilization defrost operation of 1st Embodiment, the flow of a refrigerant | coolant, and the refrigerant | coolant amount in a receiver. It is a figure which shows the compressor and valve state in the reverse cycle defrost operation of 1st Embodiment, the flow of a refrigerant | coolant, and the refrigerant | coolant amount in a receiver. It is a flowchart which shows the switching operation | movement (a defrost preparation operation and a receiver utilization defrost operation are included) between the heating operation and reverse cycle defrost operation in a modification. It is a figure which shows the compressor and valve state in the defrost preparation operation of 1st Embodiment, the flow of a refrigerant | coolant, and the refrigerant | coolant amount in a receiver. It is a schematic block diagram of the air conditioning apparatus concerning 2nd Embodiment. It is a control block diagram of the air conditioning apparatus of 2nd Embodiment. It is a figure which shows the compressor and valve state, the flow of a refrigerant | coolant, and the refrigerant | coolant amount in a receiver in the receiver utilization defrost operation of the air conditioning apparatus of 2nd Embodiment. It is a figure which shows the compressor and valve state in the defrost preparation operation of the air conditioning apparatus of 2nd Embodiment, the flow of a refrigerant | coolant, and the refrigerant | coolant amount in a receiver. It is a schematic block diagram of the air conditioning apparatus concerning 3rd Embodiment. It is a control block diagram of the air conditioning apparatus of 3rd Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an air conditioner according to the present invention will be described with reference to the drawings. In addition, the specific structure of the air conditioning apparatus concerning this invention is not restricted to the following embodiment, It can change in the range which does not deviate from the summary of invention.

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

<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.

  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 first expansion valve 24, a receiver 25, a liquid side closing valve 27, and a gas side closing valve 28. have.

  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. Here, as the outdoor heat exchanger 23, as shown in FIG.2 and FIG.3, the insertion fin comprised by many heat-transfer tubes 61 which consist of flat tubes, and many heat-transfer fins 64 which consist of insertion fins. A heat exchanger of the type is adopted. The heat transfer tube 61 is a flat multi-hole tube having a flat surface 62 serving as a heat transfer surface and a large number of small internal flow paths 63 through which refrigerant flows. A large number of heat transfer tubes 61 are arranged in a plurality of stages at intervals along the vertical direction with the flat surfaces 62 facing each other. Here, a large number of heat transfer tubes 61 are arranged in two rows along the outdoor air flow direction, and one end in the longitudinal direction (here, the right end in FIG. 2) is the refrigerant flow distributor 66 and the inlet / outlet header 67. Alternatively, it is connected to the intermediate header 68, and the other end in the longitudinal direction (here, the left front end in FIG. 2) is connected to the connection header 69. Here, the refrigerant flow distributor 66, the inlet / outlet header 67, the intermediate header 68, and the connection header 69 are vertically long members having a refrigerant flow path formed therein. The refrigerant distributor 66 is connected to the liquid refrigerant pipe 35, and the inlet / outlet header 67 is connected to the first gas refrigerant pipe 33. Thus, the portion of the outdoor heat exchanger 23 near the inlet / outlet header 67 with respect to the refrigerant flow constitutes the gas side end 23a of the outdoor heat exchanger 23, and the portion of the outdoor heat exchanger 23 near the refrigerant flow divider 66 with respect to the refrigerant flow. Constitutes the liquid side end 23b of the outdoor heat exchanger 23, and the portion between the gas side end 23a and the liquid side end 23b with respect to the flow of the refrigerant is an intermediate portion of the outdoor heat exchanger 23. It is composed. A plurality of heat transfer fins 64 are arranged at intervals along the longitudinal direction of the heat transfer tube 63. Here, in correspondence with the heat transfer tubes 61 being arranged in two rows along the direction of outdoor air flow, the heat transfer fins 64 are also arranged in two rows along the direction of outdoor air flow. The heat transfer fin 64 has a large number of notches 65 into which the heat transfer tubes 61 are inserted. The notch 65 extends from the horizontal edge of the heat transfer fin 64 in the horizontal direction (here, the edge on the windward side with respect to the passage direction of the outdoor air) in the horizontal direction. Here, the overall shape of the outdoor heat exchanger 23 is substantially L-shaped in plan view, but the shape is not limited to this, and there are various shapes depending on the type of the outdoor unit 2 and the device arrangement. May be. In addition, here, the heat transfer tubes 61 and the heat transfer fins 64 are arranged in two rows along the outdoor air flow direction, but the present invention is not limited to this, and the heat transfer tubes 61 and the heat transfer fins are not limited thereto. 64 may be a configuration in which only one row is arranged, or may be a configuration in which three or more rows are arranged. At this time, the refrigerant flow distributor and header may be appropriately connected to the end portion in the longitudinal direction of the heat transfer tube 61 according to the arrangement of the heat transfer tubes 61 and the passage.

  The first expansion valve 24 is a valve that reduces the high-pressure refrigerant in the refrigeration cycle that has radiated heat in the outdoor heat exchanger 23 to the low pressure in the refrigeration cycle during the cooling operation. Moreover, the 1st expansion valve 24 is a valve which decompresses the high-pressure refrigerant | coolant in the refrigerating cycle which thermally radiated in the indoor heat exchanger 41 to the low pressure in a refrigerating cycle at the time of heating operation. The first 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 first expansion valve 24.

  The receiver 25 is provided in a portion of the liquid refrigerant pipe 35 between the indoor heat exchanger 41 and the first expansion valve 24. The receiver 25 is a container capable of storing the refrigerant that has become a low pressure in the refrigeration cycle during the cooling operation and has radiated heat in the outdoor heat exchanger 23. The receiver 25 is a container capable of storing the refrigerant that has become a high pressure in the refrigeration cycle during the heating operation and has radiated heat in the indoor heat exchanger 41.

  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 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 portion where the suction pipe 31 and the receiver pressure adjustment pipe 30 merge. 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 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.

<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 which performs operation control of the whole air conditioning apparatus 1 including heating operation, reverse cycle defrost operation, cooling operation, etc. by the transmission line 8a which connects between the indoor side control part 44 and the outdoor side control part 38. Part 8 is configured.

  As shown in FIG. 4, the control unit 8 is connected so as to be able to receive detection signals from various sensors 51 to 55, 57 to 59, and various devices and valves 21a based on these detection signals and the like. , 22, 24, 37, 43, etc. are connected so that they can be controlled.

  As described above, the air conditioner 1 includes the refrigerant circuit 10 configured by connecting the compressor 21, the outdoor heat exchanger 23, the first expansion valve 24, and the indoor heat exchanger 41, the compressor 21, And a control unit 8 that controls the first expansion valve 24 and the like. The control unit 8 includes a heating operation in which the refrigerant is circulated in the order of the compressor 21, the indoor heat exchanger 41, the first expansion valve 24, and the outdoor heat exchanger 23 to heat the room, and the compressor 21 and the outdoor heat exchanger 23. The reverse cycle defrosting operation in which the refrigerant is circulated in the order of the first expansion valve 24 and the indoor heat exchanger 41 to defrost the outdoor heat exchanger 23 is performed. The controller 8 also performs a cooling operation in which the refrigerant is circulated in the order of the compressor 21, the outdoor heat exchanger 23, the first expansion valve 24, and the indoor heat exchanger 41 to cool the room. The refrigerant circuit 10 further includes a receiver 25 connected between the indoor heat exchanger 41 and the first expansion valve 24.

(2) Basic operation | movement of an air conditioning apparatus Next, the basic operation | movement of the air conditioning apparatus 1 is demonstrated using FIG. The air conditioner 1 can be switched between a cooling operation and a heating operation. Moreover, at the time of heating operation, it is also possible to switch to the reverse cycle defrosting operation for melting the frost adhering to the outdoor heat exchanger 23. Note that the cooling operation, the heating operation, and the reverse cycle defrosting operation as these basic operations are performed by the control unit 8.

<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 compressed until it reaches the high pressure in the refrigeration cycle, and then discharged.

  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 first expansion valve 24.

  The high-pressure liquid refrigerant sent to the first expansion valve 24 is decompressed to the low pressure of the refrigeration cycle by the first expansion valve 24, and becomes a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant decompressed by the first expansion valve 24 is sent to the receiver 25.

  The low-pressure refrigerant sent to the receiver 25 is temporarily stored in the receiver 25, and then 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 again sucked into the compressor 21 through the gas refrigerant communication pipe 6, the gas-side closing valve 28 and the four-way switching valve 22.

<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 compressed until it reaches the high pressure in the refrigeration cycle, and then discharged.

  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 receiver 25 through the liquid refrigerant communication pipe 5 and the liquid side shut-off valve 27.

  The high-pressure refrigerant placed in the receiver 25 is temporarily stored in the receiver 25 and then sent to the first expansion valve 24.

  The high-pressure refrigerant sent to the first expansion valve 24 is depressurized to the low pressure of the refrigeration cycle by the first expansion valve 24 to become a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant decompressed by the first expansion valve 24 is sent to the outdoor heat exchanger 23.

  The low-pressure refrigerant sent to the outdoor heat exchanger 23 evaporates by exchanging heat with the 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 again sucked into the compressor 21 through the four-way switching valve 22.

<Reverse cycle defrosting operation>
During the heating operation described above, when frost formation in the outdoor heat exchanger 23 is detected, for example, when the refrigerant temperature Torm in the outdoor heat exchanger 23 falls below a predetermined defrosting start temperature, that is, the outdoor heat exchanger When the defrosting start condition indicating that the defrosting of 23 is necessary is reached, a reverse cycle defrosting operation for defrosting the outdoor heat exchanger 23 by melting the frost attached to the outdoor heat exchanger 23 is performed. Do.

  In the reverse cycle defrosting operation, similarly to the cooling operation described above, the four-way switching valve 22 is switched to the cooling cycle state (the state shown by the solid line in FIG. 1), whereby the compressor 21, the outdoor heat exchanger 23, In this operation, the refrigerant is circulated in the order of the first expansion valve 24 and the indoor heat exchanger 41 so that the outdoor heat exchanger 23 functions as a refrigerant radiator. Thereby, the frost adhering to the outdoor heat exchanger 23 can be thawed. In the reverse cycle defrosting operation, the temperature Torm of the refrigerant in the outdoor heat exchanger 23 rises above a predetermined defrosting end temperature at which the defrosting of the outdoor heat exchanger 23 can be regarded as completed, or the like. The process is performed until the defrosting termination condition indicating that the defrosting is completed, and then the heating operation is resumed. In addition, since the flow of the refrigerant | coolant in the refrigerant circuit 10 in a reverse cycle defrost operation is the same as that of the said cooling operation, description is abbreviate | omitted here.

(3) Switching operation between heating operation and reverse cycle defrosting operation (including receiver defrosting operation)
In the reverse cycle defrosting operation, as described above, the outdoor heat exchanger 23 has the gas side end 23a as the refrigerant inlet and the outdoor heat exchanger 23 has the liquid side end 23b as the refrigerant outlet. In this operation, the refrigerant discharged from the compressor 21 flows from the gas side end 23a of the exchanger 23 toward the liquid side end 23b. For this reason, in the reverse cycle defrosting operation, the frost adhering to the gas side end portion 23a of the outdoor heat exchanger 23 and the vicinity thereof first begins to melt, and then the frost adhering to the intermediate portion 23c of the outdoor heat exchanger 23. Is melted, and the frost adhering to the liquid side end 23b of the outdoor heat exchanger 23 and the vicinity thereof is finally melted. Due to the refrigerant flow in the reverse cycle defrosting operation, frost remaining on the liquid side end 23b of the outdoor heat exchanger 23 and its vicinity is likely to be generated after the reverse cycle defrosting operation. The frost time tends to be longer.

  Therefore, here, when the defrosting start condition indicating that the defrosting of the outdoor heat exchanger 23 is necessary during the heating operation is reached, the compressor 21 is stopped before starting the reverse cycle defrosting operation. In addition, by opening the first expansion valve 24, the refrigerant flows from the receiver 25 toward the outdoor heat exchanger 23 due to the differential pressure between the refrigerant in the receiver 25 and the refrigerant in the outdoor heat exchanger 23. The receiver defrosting operation for defrosting the liquid-side end portion 23b of 23 is performed.

  Next, switching operation (including receiver-based defrosting operation) between the heating operation and the reverse cycle defrosting operation will be described with reference to FIGS. Here, FIG. 5 is a flowchart showing the switching operation (including the receiver defrosting operation) between the heating operation and the reverse cycle defrosting operation. FIG. 6 is a diagram showing the state of the compressor 21 and valves 22 and 24 in the heating operation, the refrigerant flow, and the refrigerant amount in the receiver 25. FIG. 7 is a diagram illustrating the state of the compressor 21 and the valves 22 and 24, the flow of the refrigerant, and the amount of refrigerant in the receiver 25 in the receiver defrosting operation. FIG. 8 is a diagram illustrating the state of the compressor 21 and the valves 22 and 24, the refrigerant flow, and the refrigerant amount in the receiver 25 in the reverse cycle defrosting operation. Note that the control unit 8 also performs a switching operation (including receiver-based defrosting operation) between the heating operation and the reverse cycle defrosting operation described below.

<Step ST1>
During the heating operation, the control unit 8 first determines whether or not the defrost start condition indicating that the defrosting of the outdoor heat exchanger 23 is necessary is reached in step ST1. Here, as described above, it is determined whether or not frost formation in the outdoor heat exchanger 23 has been detected, for example, when the refrigerant temperature Torm in the outdoor heat exchanger 23 falls below a predetermined defrosting start temperature. Yes.

  And in step ST1, when it determines with having reached defrost start conditions (here, when it is judged that the frost formation in the outdoor heat exchanger 23 was detected), the control part 8 is the following. The process proceeds to a receiver defrosting operation process in steps ST2 and ST3.

<Steps ST2 and ST3>
Next, the control part 8 performs receiver utilization defrost operation in step ST2, ST3. That is, here, the receiver defrosting operation is performed before starting the reverse cycle defrosting operation of step ST4.

  Here, the control part 8 performs operation which stops the compressor 21 and opens the 1st expansion valve 24 in step ST2. Specifically, the control unit 8 stops the compressor 21 while keeping the four-way switching valve 22 in the heating cycle state (see FIGS. 6 and 7). And the control part 8 opens the opening degree of the 1st expansion valve 24 which was in the normal control state at the time of heating operation to a large opening degree state (here, fully open state) (refer FIG.6 and FIG.7).

  Then, the refrigerant flows from the receiver 25 toward the outdoor heat exchanger 23 due to the differential pressure between the refrigerant in the receiver 25 and the refrigerant in the outdoor heat exchanger 23 (see FIG. 7). And the defrosting of the liquid side edge part 23b of the outdoor heat exchanger 23 and its vicinity comes to be performed with the flow of this refrigerant | coolant. At this time, the refrigerant (see FIG. 6) in the receiver 25 that has accumulated a normal amount during the heating operation is reduced by performing the receiver defrosting operation (see FIG. 7).

  This receiver defrosting operation is performed until the receiver defrost termination condition is reached in step ST3. Here, whether or not the receiver use defrost termination condition has been reached is determined by whether or not the control unit 8 has passed a predetermined receiver use defrost time from the start of the receiver use defrost operation. And in step ST3, when it determines with having reached the receiver utilization defrost termination conditions (here receiver utilization defrost time has passed), the control part 8 is a reverse cycle of step ST4, ST5. The process proceeds to the defrosting operation.

  Thus, here, the receiver 25 is provided between the indoor heat exchanger 23 and the first expansion valve 24, and the compressor 21 is stopped before the reverse cycle defrosting operation of step ST4 is started. In addition, a receiver defrosting operation including an operation of opening the first expansion valve 24 is performed. That is, here, before starting the reverse cycle defrosting operation, the operation of stopping the compressor 21 and opening the first expansion valve 24 in the refrigerant circuit 10 that has been performing the heating operation is performed. Using the differential pressure between the pressure of the refrigerant (pressure close to the high pressure of the refrigeration cycle) and the pressure of the refrigerant in the outdoor heat exchanger 23 (pressure close to the low pressure of the refrigeration cycle), the receiver 25 sends the pressure to the outdoor heat exchanger 23. A high-temperature refrigerant is allowed to flow. In particular, since the refrigerant in the receiver 25 in which a large amount of refrigerant is accumulated is used here, the differential pressure is easily maintained even when the compressor 21 is stopped, and the outdoor heat exchanger 23 is Many refrigerants can flow. For this reason, before starting the reverse cycle defrosting operation of step ST4, the frost adhering to the liquid side end 23b of the outdoor heat exchanger 23 serving as the refrigerant outlet during the reverse cycle defrosting operation and the vicinity thereof is removed. It can be melted in advance, and then the reverse cycle defrosting operation of step ST4 can be started.

  Here, it is preferable that the receiver defrosting operation is performed until there is no differential pressure between the refrigerant in the receiver 25 and the refrigerant in the outdoor heat exchanger 23 so that the defrosting effect can be sufficiently exhibited. Therefore, here, the time until the differential pressure between the refrigerant in the receiver 25 and the refrigerant in the outdoor heat exchanger 23 is lost is predicted, and based on this time, the receiver as the receiver defrosting end condition in step ST3 The usage defrosting time is set. Specifically, based on the fact that the time until the differential pressure between the refrigerant in the receiver 25 and the refrigerant in the outdoor heat exchanger 23 disappears is predicted to be several tens of seconds to several minutes, the receiver defrosting is performed. The time is set to a time value of about several tens of seconds to several minutes. That is, here, the control unit 8 performs the receiver defrosting operation until the differential pressure between the refrigerant in the receiver 25 and the refrigerant in the outdoor heat exchanger 23 disappears. Here, “until the pressure difference disappears” means that the pressure difference between the refrigerant in the receiver 25 and the refrigerant in the outdoor heat exchanger 23 falls within the range of 0 to 0.1 MPa.

<Steps ST4 and ST5>
Next, the control part 8 performs reverse cycle defrost operation in step ST4, ST5. That is, here, after performing the receiver defrosting operation in steps ST2 and ST3, the reverse cycle defrosting operation is performed. Here, the reverse cycle defrosting operation is the same as the reverse cycle defrosting operation in the above basic operation. Here, in step ST4, the control unit 8 switches the four-way switching valve 22 to the cooling cycle state, and This is started by starting the compressor 21 (see FIG. 8). Then, the reverse cycle defrosting operation is performed until the control unit 8 determines in step ST5 that the defrosting end condition indicating that the defrosting of the outdoor heat exchanger 23 has been completed is reached. Here, the defrosting termination condition is the same as the defrosting termination condition in the basic operation.

  Then, here, as described above, the frost adhering to the liquid side end 23b of the outdoor heat exchanger 23 serving as the refrigerant outlet and the vicinity thereof is melted by the receiver defrosting operation of steps ST2 and ST3. Therefore, generation | occurrence | production of the unmelted frost adhering to the liquid side edge part 23b of the outdoor heat exchanger 23 and its vicinity after complete | finishing a reverse cycle defrost operation can be suppressed. For this reason, the defrosting of the outdoor heat exchanger 23 can be performed efficiently. Moreover, compared with the case where the defrost of the outdoor heat exchanger 23 is performed only by the reverse cycle defrost operation, in a short time (that is, by shortening the total time of the receiver use defrost time and the reverse cycle defrost time), The defrosting of the outdoor heat exchanger 23 can be performed.

  Here, even when switching between the heating operation and the reverse cycle defrosting operation of Patent Document 1 described above, an operation of temporarily stopping the compressor is performed. The purpose is to reduce sound, and the compressor is merely stopped for a very short time. For this reason, the operation of temporarily stopping the compressor in Patent Document 1 is different from the above-described receiver-based defrosting operation in that the frost adhering to the liquid side end of the outdoor heat exchanger and its vicinity is melted. It is difficult to get substantially.

  Here, the control unit 8 performs the receiver defrosting operation with the stop of the compressor 21 until the differential pressure between the refrigerant in the receiver 25 and the refrigerant in the outdoor heat exchanger 23 disappears. . That is, here, since the compressor 21 is stopped for a long time compared to the temporary stop of the compressor in Patent Document 1, the liquid-side end portion 23b of the outdoor heat exchanger 23 and the vicinity thereof are stopped. Defrosting can be sufficiently performed.

(4) Modified example The defrosting effect by the receiver defrosting operation described above tends to depend on the amount of refrigerant accumulated in the receiver 25 during the receiver defrosting operation. Specifically, the greater the amount of refrigerant accumulated in the receiver 25, the easier it is to maintain the differential pressure between the refrigerant in the receiver 25 and the refrigerant in the outdoor heat exchanger 23 during the receiver defrosting operation. Thereby, it is possible to easily secure the flow of the refrigerant from the receiver 25 toward the outdoor heat exchanger 23.

  Therefore, here, the controller 8 is configured to perform a defrost preparation operation in which refrigerant is accumulated in the receiver 25 before starting the receiver-use defrost operation.

  Next, switching operation (including defrost preparation operation and receiver-based defrosting operation) between the heating operation and the reverse cycle defrosting operation will be described with reference to FIGS. Here, FIG. 9 is a flowchart showing the switching operation (including the defrost preparation operation and the receiver defrosting operation) between the heating operation and the reverse cycle defrosting operation. FIG. 10 is a diagram illustrating the state of the compressor 21 and the valves 22 and 24, the refrigerant flow, and the refrigerant amount in the receiver 25 in the defrost preparation operation. In addition, the switching operation (including the defrost preparation operation and the receiver defrost operation) between the heating operation and the reverse cycle defrost operation described below is also performed by the control unit 8. Moreover, in the following, about the process of step ST1-ST3, ST4, ST5 similar to the process of said step ST1-ST3, ST4, ST5, about description of the process of step ST6 which simplifies description and performs defrost preparation operation. Mainly explained.

<Step ST1>
During the heating operation, the control unit 8 first determines whether or not the defrost start condition indicating that the defrosting of the outdoor heat exchanger 23 is necessary is reached in step ST1.

  And in step ST1, when it determines with having reached defrost start conditions (here, when it is judged that the frost formation in the outdoor heat exchanger 23 was detected), the control part 8 is the following. Before starting the receiver defrosting operation in step ST2, the process proceeds to the defrosting preparation operation in step ST6.

<Step ST6>
Next, the control part 8 performs the defrost preparation operation which accumulates a refrigerant | coolant in the receiver 25 in step ST6. That is, here, the control unit 8 performs the defrost preparation operation for storing the refrigerant in the receiver 25 before starting the receiver defrosting operation in step ST2, so that the amount of the refrigerant accumulated in the receiver 25 is reduced. The number is increased in advance. Here, the control unit 8 continues the operation of the compressor 21 in the refrigerant circuit 10 performing the heating operation (that is, with the four-way switching valve 22 in the heating cycle state) as the defrost preparation operation. The opening of the first expansion valve 24 that was in the normal control state during the heating operation is closed to a small opening state (here, a fully closed state) (see FIG. 10).

  If it does so, the refrigerant | coolant (refer FIG. 6) in the receiver 25 which accumulated the normal quantity at the time of heating operation will accumulate in the receiver 25 located in the upstream of the 1st expansion valve 24, and the refrigerant | coolant amount in the receiver 25 will increase. (See FIG. 10). With such a defrost preparation operation, the refrigerant amount accumulated in the receiver 25 can be made larger than the normal amount during the heating operation before starting the receiver defrost operation. During the defrost preparation operation, as in the heating operation, since the state in which the indoor heat exchanger 41 functions as a refrigerant radiator is maintained, the heating operation is continued indoors. become.

  And after performing defrost preparation operation in step ST6, the control part 8 transfers to the process of receiver utilization defrost operation of step ST2, ST3.

<Steps ST2 and ST3>
Next, the control part 8 performs receiver utilization defrost operation in step ST2, ST3. That is, here, the receiver defrosting operation is performed before starting the reverse cycle defrosting operation of step ST4. That is, the control unit 8 performs an operation of stopping the compressor 21 and opening the first expansion valve 24 in step ST2. Specifically, the control unit 8 stops the compressor 21 while keeping the four-way switching valve 22 in the heating cycle state (see FIGS. 8 and 7). And the control part 8 opens the opening degree of the 1st expansion valve 24 which was in the small opening state at the time of defrost preparation operation to a large opening state (here, fully open state) (refer FIG.8 and FIG.7). This receiver defrosting operation is performed until the receiver defrost termination condition is reached in step ST3.

  Then, the refrigerant flows from the receiver 25 toward the outdoor heat exchanger 23 due to the differential pressure between the refrigerant in the receiver 25 and the refrigerant in the outdoor heat exchanger 23 (see FIG. 7). And the defrosting of the liquid side edge part 23b of the outdoor heat exchanger 23 and its vicinity comes to be performed with the flow of this refrigerant | coolant. At this time, the refrigerant in the receiver 25 (see FIG. 8) that has accumulated from the normal amount during the heating operation by the defrost preparation operation in step ST6 is reduced by performing the defrosting operation using the receiver (see FIG. 8). 7).

<Steps ST4 and ST5>
Next, the control part 8 performs reverse cycle defrost operation in step ST4, ST5. That is, here, after performing the receiver defrosting operation in steps ST2 and ST3, the reverse cycle defrosting operation is performed. Here, the reverse cycle defrosting operation is the same as the reverse cycle defrosting operation in the above basic operation. Here, in step ST4, the control unit 8 switches the four-way switching valve 22 to the cooling cycle state, and This is started by starting the compressor 21 (see FIG. 8). Then, the reverse cycle defrosting operation is performed until the control unit 8 determines in step ST5 that the defrosting end condition indicating that the defrosting of the outdoor heat exchanger 23 has been completed is reached. Here, the defrosting termination condition is the same as the defrosting termination condition in the basic operation.

  As described above, since a large amount of refrigerant is accumulated in the receiver 25 by the defrost preparation operation in step ST6, the receiver 25 in the receiver defrost operation in steps ST2 and ST3 to be performed subsequently. The pressure difference between the refrigerant in the outdoor heat exchanger 23 and the refrigerant in the outdoor heat exchanger 23 is maintained, and the flow of the refrigerant from the receiver 25 toward the outdoor heat exchanger 23 can be easily ensured.

  Thereby, before starting a receiver utilization defrost operation, many refrigerant | coolants can be stored in the receiver 25, and the defrost effect by a receiver utilization defrost operation can be heightened here now.

-Second Embodiment-
In the configuration of the first embodiment and the modification thereof (see FIG. 1), as shown in FIG. 11, the receiver pressure adjustment pipe 30 for extracting the refrigerant in the gas state to the suction side of the compressor 21 in the receiver 25. May be connected. Here, the receiver pressure adjustment pipe 30 is provided so as to extract the refrigerant from the gas phase portion above the receiver 25.

  However, when the receiver pressure adjusting pipe 30 is provided together with the receiver 25 to extract the refrigerant on the suction side of the compressor 21 as described above, the receiver defrosting operation in steps ST2 and ST3 described above (see FIGS. 5 and 9). ), The pressure of the refrigerant in the receiver 25 tends to decrease. For this reason, it becomes difficult to maintain the differential pressure between the refrigerant in the receiver 25 and the refrigerant in the outdoor heat exchanger 23, and it may be difficult to secure the flow of refrigerant from the receiver 25 toward the outdoor heat exchanger 23.

  Therefore, here, as shown in FIG. 11, a receiver pressure adjustment valve 30 a is further provided in the receiver pressure adjustment pipe 30. The receiver pressure adjustment valve 30a is a valve that can be controlled to be opened and closed by the control unit 8, as shown in FIG. Here, an electromagnetic valve is employed as the receiver pressure adjustment valve 30a. The receiver pressure adjustment tube 30 is provided with a capillary tube 30 b in order to limit the flow rate of the refrigerant flowing out from the receiver 25 to the suction side of the compressor 21 through the receiver pressure adjustment tube 30. And the control part 8 is made to close the receiver pressure regulation valve 30a, when performing receiver defrost operation, as shown in FIG.

  For this reason, although it is the structure which provided the receiver pressure adjustment pipe | tube 30 in the receiver 25 here, the flow of the refrigerant | coolant similar to the case where the receiver pressure adjustment pipe | tube 30 is not provided in the receiver 25 can be obtained. The pressure is easy to maintain. Thereby, although it is the structure which provided the receiver pressure adjustment pipe | tube 30 in the receiver 25 here, it is easy to ensure the flow of the refrigerant | coolant which goes to the outdoor heat exchanger 23 from the receiver 25, and uses receiver defrost operation. It can make it easy to obtain the defrosting effect.

  Moreover, when performing the defrost preparation operation (refer FIG. 9) of said step ST6, it is preferable to increase the refrigerant | coolant amount which accumulates in the receiver 25 by a receiver utilization defrost operation as much as possible.

  Therefore, here, as shown in FIG. 14, the control unit 8 opens the receiver pressure adjustment valve 30a when performing the defrost preparation operation.

  For this reason, here, using the configuration in which the receiver pressure adjustment pipe 30 having the receiver pressure adjustment valve 30a is provided in the receiver 25, the amount of refrigerant accumulated in the receiver 25 by the defrost preparation operation is increased. be able to. Thereby, the defrosting effect by a receiver utilization defrosting operation can be heightened here.

-Third embodiment-
In the configuration of the first embodiment and the modified example (see FIG. 1), as shown in FIG. 15, the portion (here, the liquid side) of the liquid refrigerant pipe 35 between the indoor heat exchanger 41 and the receiver 25. You may make it provide the 2nd expansion valve 26 in the part between the closing valve 27 and the receiver 25). As shown in FIG. 16, the second expansion valve 26 is a valve whose opening degree can be controlled by the control unit 8. Here, an electric expansion valve is employed as the second expansion valve 26. Moreover, you may make it further provide the receiver pressure adjustment pipe | tube 30 which has the receiver pressure adjustment valve 30a in the receiver 25 similarly to said 2nd Embodiment and its modification (refer FIG. 11).

  In this case, the controller 8 performs the second defrosting operation (see FIGS. 5 and 9) in steps ST2 and ST3 and the defrosting preparation operation (see FIG. 9) in step ST6. The expansion valve 26 may be in a large opening state (for example, a fully open state).

  Thereby, although it is the structure which has the 2nd expansion valve 26 here, the refrigerant | coolant similar to the structure of 1st and 2nd embodiment (refer FIG.1 and FIG.11) which does not have the 2nd expansion valve 26 is used. As for the defrost preparation operation and the receiver-use defrost operation, the same effects as those of the first and second embodiments and the modifications thereof can be obtained.

-Other embodiments-
<A>
In said embodiment and its modification, although whether the receiver utilization defrost time passed is employ | adopted as receiver utilization defrost completion | finish conditions, it is not limited to this.

  For example, the refrigerant temperature Torm in the outdoor heat exchanger 23 or the refrigerant temperature Torl on the liquid side of the outdoor heat exchanger 23 is equal to or higher than a predetermined receiver-use defrost end temperature at which defrosting of the outdoor heat exchanger 23 can be regarded as completed. It may be adopted whether or not it has risen. Even in this case, the receiver defrosting end temperature is set based on the temperature value predicted to be reached when the differential pressure between the refrigerant in the receiver 25 and the refrigerant in the outdoor heat exchanger 23 disappears. Is preferred.

  Further, for example, a pressure sensor or a temperature sensor for detecting the pressure or saturation temperature of the refrigerant in the receiver 25 and the pressure or saturation temperature of the refrigerant in the outdoor heat exchanger 23 is provided, and the refrigerant in the receiver 25 and the outdoor The receiver defrosting termination condition is that the differential pressure (or the corresponding difference in saturation temperature) with the refrigerant in the heat exchanger 23 decreases to a predetermined threshold differential pressure (or the corresponding threshold saturation temperature difference). May be.

<B>
In said embodiment and its modification, as the outdoor heat exchanger 23, the heat exchange of the insertion fin type comprised by many heat-transfer tubes 61 which consist of flat tubes, and many heat-transfer fins 64 which consist of insertion fins. Although the vessel is adopted, it is not limited to this. For example, the heat exchanger which employ | adopted the corrugated fin as the heat exchanger fin 64 may be sufficient, and the heat exchanger which employ | adopted the circular tube as the heat exchanger tube 61 may be sufficient.

  The present invention is widely applicable to an air conditioner that switches between heating operation and reverse cycle defrosting operation.

DESCRIPTION OF SYMBOLS 1 Air conditioning apparatus 8 Control part 10 Refrigerant circuit 21 Compressor 23 Outdoor heat exchanger 23b Liquid side edge part 24 First expansion valve 25 Receiver 30 Receiver pressure adjustment pipe 30a Receiver pressure adjustment valve 41 Indoor heat exchanger

Japanese Unexamined Patent Publication No. 7-174440

Claims (4)

A refrigerant circuit (10) configured by connecting a compressor (21), an outdoor heat exchanger (23), an expansion valve (24), and an indoor heat exchanger (41), the compressor and the expansion valve And a controller (8) for controlling the room, and the controller heats the room by circulating a refrigerant in the order of the compressor, the indoor heat exchanger, the expansion valve, and the outdoor heat exchanger. The heating operation is switched to the reverse cycle defrosting operation in which the refrigerant is circulated in the order of the compressor, the outdoor heat exchanger, the expansion valve, and the indoor heat exchanger to defrost the outdoor heat exchanger. In the air conditioner,
The refrigerant circuit further includes a receiver (25) connected between the indoor heat exchanger and the expansion valve,
When the controller reaches a defrosting start condition indicating that defrosting of the outdoor heat exchanger is necessary during the heating operation, the control unit starts the reverse cycle defrosting operation before starting the reverse cycle defrosting operation. And by opening the expansion valve, the refrigerant flows from the receiver toward the outdoor heat exchanger by the pressure difference between the refrigerant in the receiver and the refrigerant in the outdoor heat exchanger. A defrosting operation using a receiver that defrosts the liquid side end (23b) of the vessel,
Air conditioner (1). The controller (8) performs the receiver defrosting operation until there is no differential pressure between the refrigerant in the receiver (25) and the refrigerant in the outdoor heat exchanger (23).
The air conditioner (1) according to claim 1. The receiver (25) is connected to a receiver pressure adjustment pipe (30) for extracting the refrigerant in the gas state to the suction side of the compressor (21),
The receiver pressure adjustment pipe is provided with a receiver pressure adjustment valve (30a),
The control unit (8) closes the receiver pressure adjusting valve when performing the receiver defrosting operation.
The air conditioner (1) according to claim 1 or 2. The said control part (8) performs the defrost preparation operation which accumulates a refrigerant | coolant in the said receiver (25), before starting the said receiver utilization defrost operation.
The air conditioning apparatus (1) according to any one of claims 1 to 3.

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