JP2013210161A - Refrigerating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To defrost an outdoor heat exchanger in a refrigerating apparatus performing multiple-stage compression while allowing an indoor heat exchanger to function as a radiator.SOLUTION: An air conditioning apparatus 10 includes a four-stage compressor 20, a fourth heat exchanger 44 that functions as a radiator during a cooling operation and functions as an evaporator during a heating operation, and first to third heat exchangers 41-43 that function as a radiator which cools an intermediate pressure refrigerant inhaled into high-stage compression parts 22-24 during the cooling operation and functions as an evaporator during the heating operation. One of first to fourth heat exchangers 41-44 functions as a radiator during a defrosting operation, the other heat exchangers function as evaporators, and an indoor heat exchanger 12a functions as a radiator.

Description

  The present invention relates to a refrigeration apparatus, and more particularly to a refrigeration apparatus provided with a multistage compression mechanism.

  2. Description of the Related Art Conventionally, there are refrigeration apparatuses that perform a multistage compression refrigeration cycle, and include a unit that cools an intermediate-pressure refrigerant during compression. For example, in the refrigeration apparatus described in Patent Document 1 (Japanese Patent Laid-Open No. 2010-112618), the heat source unit includes an outdoor heat exchanger and an outdoor intermediate cooler, and the outdoor heat exchanger is used during cooling operation. Functions as a gas cooler, and the outdoor intermediate cooler functions as an intercooler that cools the intermediate-pressure refrigerant that is discharged from the front-stage compression element and sucked into the rear-stage compression element. By thus cooling the intermediate pressure refrigerant in the middle of compression, the operating efficiency of the refrigeration apparatus is increased.

  In the refrigeration apparatus described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2010-112618) described above, during the heating operation, the gas-liquid two-phase refrigerant decompressed by the expansion mechanism is divided and the outdoor heat exchanger and the outdoor intermediate are separated. It flows in parallel with both of the coolers, and the outdoor heat exchanger and the outdoor intermediate cooler function as an evaporator. In this way, compared with the case where only the outdoor heat exchanger is used as the evaporator, the refrigerant circulation amount can be increased and the operating efficiency of the refrigeration apparatus can be increased.

  By the way, in each heat exchanger of the heat source unit that functions as an evaporator during heating operation, moisture contained in air (outside air) as a heat source is condensed, and frost formation increases especially when the outside air temperature is low. In order to melt the frost adhering to the heat exchanger of such a heat source unit, a defrosting operation is generally performed in the refrigeration apparatus. In the defrosting operation, the heating operation is usually stopped, the refrigerant is allowed to flow in the cooling operation cycle, and the high-temperature refrigerant discharged from the compressor is allowed to flow to the heat exchanger of the heat source unit. However, when performing a normal defrosting operation in which the refrigerant flows in the cooling operation cycle, it is necessary to stop the heating operation, which imposes patience on the user.

  The subject of this invention is providing the refrigeration apparatus which performs multistage compression which can defrost the heat-source side heat exchanger, making a utilization side heat exchanger function as a heat radiator.

  A refrigeration apparatus according to a first aspect of the present invention includes a multistage compression mechanism, a heat source side main heat exchanger, a heat source side sub heat exchanger, a use side heat exchanger, a first switching mechanism, and an expansion mechanism. And a control unit. The multistage compression mechanism is a compression mechanism in which a low-stage compression unit and a high-stage compression unit are connected in series. The heat source side main heat exchanger functions as a radiator during cooling operation and functions as an evaporator during heating operation. The heat source side sub heat exchanger functions as a radiator that cools the intermediate pressure refrigerant in the middle of compression sucked into the high-stage compression unit during the cooling operation, and functions as an evaporator during the heating operation. The use side heat exchanger functions as an evaporator during cooling operation and functions as a radiator during heating operation. In the cooling operation, the first switching mechanism sends the refrigerant from the heat source side main heat exchanger to the use side heat exchanger, and during the heating operation, the heat source side main heat exchanger and the heat source side sub heat exchange from the use side heat exchanger. The state changes so that the refrigerant is sent to the vessel. The expansion mechanism decompresses the refrigerant sent from the heat source side main heat exchanger to the user side heat exchanger during the cooling operation, and during the heating operation, the heat source side main heat exchanger and the heat source side sub heat exchange from the user side heat exchanger. The refrigerant sent to the vessel is depressurized. The control unit selectively performs a cooling operation, a heating operation, and a defrosting operation for melting frost attached to the heat source side main heat exchanger and the heat source side sub heat exchanger. In the defrosting operation, the control unit causes at least one of the heat source side main heat exchanger and the heat source side sub heat exchanger to function as an evaporator and allows the other heat exchanger to function as a radiator. The use side heat exchanger functions as a radiator.

  In this refrigeration apparatus, during cooling operation, the refrigerant flowing from the heat source side main heat exchanger functioning as a radiator to the use side heat exchanger functioning as an evaporator is decompressed by the expansion mechanism, and in the multistage compression mechanism, The intermediate-pressure refrigerant in the middle of compression sucked into the high-stage compression section is cooled by the heat source side sub heat exchanger. During heating operation, the refrigerant flowing from the use side heat exchanger functioning as a radiator to the heat source side main heat exchanger functioning as an evaporator and the heat source side sub heat exchanger is decompressed by the expansion mechanism, The refrigerant flows to the heat source side main heat exchanger and also flows to the heat source side sub heat exchanger, and evaporates in the heat source side main heat exchanger and the heat source side sub heat exchanger. Then, during the defrosting operation, the use side heat exchanger functions as a radiator as in the heating operation, and at least one of the heat source side main heat exchanger and the heat source side sub heat exchanger functions as an evaporator. And other heat exchangers function as radiators. In this defrosting operation, the user-side heat exchanger becomes a radiator, so that the user is not forced to endure. Further, frost melts in the heat source side main heat exchanger or the heat source side sub heat exchanger that functions as a radiator in the defrosting operation.

  The refrigeration apparatus according to the second aspect of the present invention is the refrigeration apparatus according to the first aspect, wherein the control unit is a radiator among the heat source side main heat exchanger and the heat source side sub heat exchanger in the defrosting operation. Switch the heat exchanger to function in order.

  In the refrigeration apparatus according to the first aspect, part of the heat source side main heat exchanger and the heat source side sub heat exchanger functions as an evaporator in the defrosting operation. If the heat exchanger functioning as a radiator is not changed among the exchanger and the heat source side sub heat exchanger, all the heat source side main heat exchanger and the heat source side sub heat exchanger will be defrosted by one defrosting operation. I can't. Therefore, in the refrigeration apparatus according to the second aspect, in the defrosting operation, the heat exchanger functioning as a radiator is sequentially switched among the heat source side main heat exchanger and the heat source side sub heat exchanger, and many heat exchanges on the heat source side are performed. Control is performed to remove the frost on the vessel.

  The refrigeration apparatus according to the third aspect of the present invention is the refrigeration apparatus according to the second aspect, wherein the heat source side main heat exchanger and the heat source side sub heat exchanger are arranged one above the other so as to overlap each other in a plane. Has been. And in a defrost operation, a control part gives priority to the heat exchanger arrange | positioned above the heat exchanger arrange | positioned below among the heat source side main heat exchanger and the heat source side sub heat exchanger. It functions as a radiator, and the heat exchangers arranged below are functioned as radiators.

  Here, since the frost of the heat exchanger located at the top melts first, the melted and heated water flows to the lower heat exchanger. Thereby, the frost of the heat exchanger located below will melt a little, and the time required to melt the frost using the heat exchanger located below as a radiator will be shortened.

  A refrigeration apparatus according to a fourth aspect of the present invention is the refrigeration apparatus according to any one of the first to third aspects, further comprising a first refrigerant pipe, a defrosting pipe, and a second switching mechanism. Yes. In the first refrigerant pipe, the low-pressure refrigerant evaporated in the use-side heat exchanger flows during the cooling operation, and during the heating operation, the high-pressure refrigerant discharged from the highest high-stage compression portion of the multistage compression mechanism is used on the use-side heat. It is a pipe that flows toward the exchanger. The defrosting pipe branches from the first refrigerant pipe and goes to the second refrigerant pipe that becomes an inlet pipe when the heat source side main heat exchanger functions as a radiator. The second switching mechanism switches between a communication state in which the first refrigerant pipe, the defrosting pipe and the second refrigerant pipe communicate with each other and a non-communication state in which the first refrigerant pipe, the defrosting pipe and the second refrigerant pipe do not communicate with each other. .

  Here, by switching the second switching mechanism to the communication state, the high-temperature high-pressure refrigerant discharged from the multiple-stage compression mechanism can flow to the use side heat exchanger and to the heat source side main heat exchanger. Thereby, it becomes possible to melt the frost attached to the heat source side main heat exchanger while causing the use side heat exchanger to function as a radiator during the defrosting operation.

  A refrigeration apparatus according to a fifth aspect of the present invention is the refrigeration apparatus according to any one of the first to fourth aspects, wherein the high-stage compression section is a second stage that sucks the refrigerant discharged from the low-stage compression section. A compression unit, and a third-stage compression unit that sucks the refrigerant discharged from the second-stage compression unit. The heat source side sub heat exchanger includes a heat source side first sub heat exchanger that cools the refrigerant discharged from the low stage compression unit during cooling operation and sucked into the second stage compression unit, and the second stage compression unit during cooling operation. And a heat source side second sub heat exchanger that cools the refrigerant discharged from the refrigerant and sucked into the third stage compression section. And in the defrosting operation, the controller causes one heat exchanger of the heat source side main heat exchanger and the heat source side sub heat exchanger to function as a radiator and the remaining heat exchanger to function as an evaporator, Make the user-side heat exchanger function as a radiator.

  Here, a multi-stage compression mechanism that has at least two high-stage compression sections and performs compression of three or more stages, two or more heat source side sub heat exchangers are also provided, and one of the heat source side is provided in the defrosting operation. Only the heat exchanger functions as a radiator, and the other two or more heat source side heat exchangers function as an evaporator. Thus, since two or more heat exchangers on the heat source side function as an evaporator in the defrosting operation, the heating capacity of the use side heat exchanger functioning as a radiator is not greatly reduced, and the user can perform heating. Even if the user is dissatisfied with the decrease in ability, the user's degree of discomfort can be kept small.

  In the refrigeration apparatus according to the first aspect of the present invention, in the defrosting operation, at least one of the heat source side main heat exchanger and the heat source side sub heat exchanger functions as an evaporator. The heat exchanger on the heat source side can be defrosted while functioning as a radiator.

  In the refrigeration apparatus according to the second aspect of the present invention, the frost of each heat exchanger on the heat source side can be melted in order in the defrosting operation.

  In the refrigeration apparatus according to the third aspect of the present invention, in the defrosting operation, the heat exchanger disposed above is preferentially caused to function as a radiator, so that the heat exchanger located below serves as a radiator. The time required to melt the frost is shortened.

  In the refrigeration apparatus according to the fourth aspect of the present invention, the high-temperature high-pressure refrigerant discharged from the multistage compression mechanism is caused to flow to the use side heat exchanger and the heat source side main heat exchange by switching the second switching mechanism to the communication state. Can be poured into a vessel.

  In the refrigeration apparatus according to the fifth aspect of the present invention, the ability of the use side heat exchanger functioning as a radiator is not greatly reduced, and the user's discomfort can be kept small.

It is a schematic block diagram at the time of air_conditionaing | cooling operation of the air conditioning apparatus which concerns on one Embodiment of this invention. FIG. 2 is a pressure-enthalpy diagram of a refrigeration cycle during the cooling operation of FIG. 1. It is a schematic block diagram at the time of the heating operation of an air conditioning apparatus. It is a pressure-enthalpy diagram of the refrigerating cycle at the time of heating operation of FIG. The schematic external appearance perspective view which abbreviate | omitted a part of side plate of the outdoor unit of an air conditioning apparatus. It is a control block diagram which shows the control object of the control part of an air conditioning apparatus. It is a control schematic diagram which shows each stage of a defrost operation. It is a schematic block diagram of the 1st stage of the defrost operation of an air conditioning apparatus. It is a pressure-enthalpy diagram at the time of the 1st stage of the defrost operation of FIG. It is a schematic block diagram of the 2nd stage of the defrost operation of an air conditioning apparatus. It is a pressure-enthalpy diagram at the time of the 2nd stage of the defrost operation of FIG. It is a schematic block diagram of the 3rd stage of the defrost operation of an air conditioning apparatus. It is a pressure-enthalpy diagram at the time of the 3rd stage of the defrost operation of FIG. It is a schematic block diagram of the 4th stage of the defrost operation of an air conditioning apparatus. It is a pressure-enthalpy diagram at the time of the 4th stage of the defrost operation of FIG. It is a schematic block diagram at the time of the heating operation of the air conditioning apparatus which concerns on the modification B. It is a schematic block diagram of the 1st stage of the defrost operation of the air conditioning apparatus which concerns on the modification B. It is a schematic block diagram of the 2nd defrosting operation | movement stage of the air conditioning apparatus which concerns on the modification B.

  An air conditioner 10 that is a refrigeration apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

(1) Configuration of Air Conditioner FIGS. 1, 3, 6, 8, 8, 10, and 14 are schematic configuration diagrams of the air conditioner 10. FIG. The air conditioning apparatus 10 is a refrigeration apparatus that performs a four-stage compression refrigeration cycle using a supercritical carbon dioxide refrigerant. The air conditioner 10 is an apparatus in which an outdoor unit 11 that is a heat source unit and a plurality of indoor units 12 that are utilization units are connected by communication refrigerant pipes 13 and 14. It has a refrigerant circuit in which the cycle and the cycle of the four stages of the defrosting operation are switched. FIG. 1 shows the flow of the refrigerant circulating in the refrigerant circuit during the cooling operation. FIG. 3 shows the flow of the refrigerant circulating in the refrigerant circuit during the heating operation. FIG. 6 is a control configuration diagram illustrating a control target device of the control unit 10a. 8, 10, 12 and 14 show the flow of the refrigerant circulating in the refrigerant circuit in each stage during the defrosting operation. In FIG. 1, FIG. 3, FIG. 8, FIG. 10, FIG. 12 and FIG. 14, the arrows shown along the piping of the refrigerant circuit represent the flow of the refrigerant.

  The refrigerant circuit of the air conditioner 10 mainly includes a four-stage compressor 20, first to fourth four-way switching valves 31 to 34 as a first switching mechanism, a defrosting three-way valve 37 as a second switching mechanism, and an outdoor unit. Heat exchanger 40, outdoor electric valve 50, check valve circuit 55, economizer heat exchanger 61, internal heat exchanger 62, expansion mechanism 70, receiver 80, supercooling heat exchanger 90, indoor heat exchanger 12a, indoor electric It consists of the valve 12b and the control part 10a (refer FIG. 6). The outdoor heat exchanger 40 includes a first heat exchanger 41, a second heat exchanger 42, a third heat exchanger 43, and a fourth heat exchanger 44 that are arranged in parallel.

  Hereinafter, each component of the refrigerant circuit will be described in detail.

(1-1) Four-stage compressor The four-stage compressor 20 includes a first compression section 21, a second compression section 22, a third compression section 23, a fourth compression section 24, and a compressor drive motor ( (Not shown) is a hermetic compressor. A compressor drive motor drives the four compression parts 21-24 via a drive shaft. That is, the four-stage compressor 20 has a uniaxial four-stage compression structure in which four compression units 21 to 24 are connected to a single drive shaft. In the four-stage compressor 20, the 1st compression part 21, the 2nd compression part 22, the 3rd compression part 23, and the 4th compression part 24 are pipe-connected in series in this order. The first compressor 21 sucks the refrigerant from the first suction pipe 21a and discharges the refrigerant to the first discharge pipe 21b. The second compressor 22 sucks the refrigerant from the second suction pipe 22a and discharges the refrigerant to the second discharge pipe 22b. The third compressor 23 sucks the refrigerant from the third suction pipe 23a and discharges the refrigerant to the third discharge pipe 23b. The fourth compressor 24 sucks the refrigerant from the fourth suction pipe 24a and discharges the refrigerant to the fourth discharge pipe 24b.

  The 1st compression part 21 is a compression mechanism of the lowest stage, and compresses the lowest pressure refrigerant which flows through a refrigerant circuit. The second compression unit 22 sucks and compresses the refrigerant compressed by the first compression unit 21. The third compression unit 23 sucks and compresses the refrigerant compressed by the second compression unit 22. The fourth compression unit 24 is the uppermost compression mechanism, and sucks and compresses the refrigerant compressed by the third compression unit 23. The refrigerant compressed by the fourth compressor 24 and discharged to the fourth discharge pipe 24b becomes the highest pressure refrigerant that flows through the refrigerant circuit.

  In addition, in this embodiment, each compression parts 21-24 are positive displacement type compression mechanisms, such as a rotary type and a scroll type. The compressor drive motor is inverter-controlled by the control unit.

  Each of the first discharge pipe 21b, the second discharge pipe 22b, the third discharge pipe 23b, and the fourth discharge pipe 24b is provided with an oil separator. The oil separator is a small container that separates lubricating oil contained in the refrigerant circulating in the refrigerant circuit. Although not shown in FIG. 1, an oil return pipe including a capillary tube extends from the lower part of each oil separator toward each of the suction pipes 21a to 24a, and the oil separated from the refrigerant is supplied to the four-stage compressor. Return to 20.

(1-2) First to fourth four-way selector valve and defrosting three-way valve First four-way selector valve 31, second four-way selector valve 32, third four-way selector valve 33, and fourth four-way selector valve Reference numeral 34 denotes a switching mechanism that is provided to switch between the cooling operation cycle and the heating operation cycle by switching the direction of the refrigerant flow in the refrigerant circuit.

  The first four-way switching valve 31 is connected to the first discharge pipe 21 b, the second suction pipe 22 a, the first cooling inlet pipe 41 f extending to the first heat exchanger 41, and the low-pressure refrigerant pipe 19. The low-pressure refrigerant pipe 19 is a refrigerant pipe through which the low-pressure gas refrigerant in the outdoor unit 11 flows, and sends the refrigerant to the first suction pipe 21 a via the internal heat exchanger 62.

  The second four-way switching valve 32 is connected to the second discharge pipe 22 b, the third suction pipe 23 a, the second cooling inlet pipe 42 f extending to the second heat exchanger 42, and the low-pressure refrigerant pipe 19.

  The third four-way switching valve 33 is connected to the third discharge pipe 23 b, the fourth suction pipe 24 a, the third cooling inlet pipe 43 f extending to the third heat exchanger 43, and the low-pressure refrigerant pipe 19.

  The fourth four-way switching valve 34 is connected to the fourth discharge pipe 24 b, the first refrigerant pipe 18 extending to the communication refrigerant pipe 14, the second refrigerant pipe 44 g extending to the fourth heat exchanger 44, and the low-pressure refrigerant pipe 19. Yes.

  Between the second refrigerant pipe 44g connected to the fourth four-way switching valve 34 and the fourth cooling inlet pipe 44f connected to the inlet side end of the fourth heat exchanger 44 during the cooling operation, there is no removal. A frost three-way valve 37 is provided. The defrosting three-way valve 37 is further connected with a defrosting pipe 36 branched from the first refrigerant pipe 18 connecting the fourth four-way switching valve 34 and the communication refrigerant pipe 14. The defrosting three-way valve 37 includes a first state in which the second refrigerant pipe 44g and the fourth cooling inlet pipe 44f are connected to connect the fourth four-way switching valve 34 and the fourth heat exchanger 44, and the defrosting The second state in which the pipe 36 and the fourth cooling inlet pipe 44f are communicated is switched. The defrosting three-way valve 37 is in the second state only during the first stage of the defrosting operation to be described later, and is in the first state otherwise.

(1-3) Outdoor Heat Exchanger The outdoor heat exchanger 40 includes the first heat exchanger 41, the second heat exchanger 42, the third heat exchanger 43, and the fourth heat exchanger 44 as described above. . During the cooling operation, the first to third heat exchangers 41 to 43 function as an intercooler that cools the refrigerant being compressed (intermediate pressure refrigerant), and the fourth heat exchanger 44 serves as a gas cooler that cools the highest pressure refrigerant. Function. The fourth heat exchanger 44 has a larger capacity than the first to third heat exchangers 41 to 43. Further, during the heating operation, all of the first to fourth heat exchangers 41 to 44 function as low-pressure refrigerant evaporators (heaters).

  As shown in FIG. 5, the outdoor heat exchanger 40 is stacked from bottom to top in the order of a first heat exchanger 41, a second heat exchanger 42, a third heat exchanger 43, and a fourth heat exchanger 44. Is integrated. That is, the 1st-4th heat exchangers 41-44 are arranged up and down so that it may overlap in a plane, and the 2nd heat exchanger 42 is just above the 1st heat exchanger 41, and the 3rd heat exchange. The unit 43 is located directly above the second heat exchanger 42, and the fourth heat exchanger 44 is located directly above the third heat exchanger 43.

  Water or air is supplied to the outdoor heat exchanger 40 as a cooling source or a heating source for exchanging heat with the refrigerant flowing inside. Here, the blower fan 40a shown in FIG. 5 blows air upward to the outdoor heat exchanger 40, so that outside air passes from the side and the rear of the outdoor unit 11 through the outdoor heat exchanger 40 into the outdoor unit 11. Inhaled.

  Further, the second suction pipe 22a, the third suction pipe 23a, and the fourth suction pipe are connected to the pipes on the outdoor electric valve 50 side of the first heat exchanger 41, the second heat exchanger 42, and the third heat exchanger 43, respectively. A first intercooler pipe 41a, a second intercooler pipe 42a, and a third intercooler pipe 43a, which are branch pipes, extend toward 24a. As shown in FIG. 1, each of the first intercooler pipe 41a, the second intercooler pipe 42a, and the third intercooler pipe 43a is provided with a check valve.

(1-4) Outdoor Electric Valve and First to Fourth Check Valves The outdoor electric valve 50 is disposed between the outdoor heat exchanger 40 and the check valve circuit 55. Further, a first check valve 51 for stopping the intermediate-pressure refrigerant from flowing toward the outdoor electric valve 50 is provided between the outdoor electric valve 50 and the first heat exchanger 41 of the outdoor heat exchanger 40. Between the motor-operated valve 50 and the second heat exchanger 42 of the outdoor heat exchanger 40, a second check valve 52 that stops the intermediate-pressure refrigerant from flowing toward the outdoor motor-operated valve 50 is provided. And a third heat exchanger 43 of the outdoor heat exchanger 40, a third check valve 53 for stopping the intermediate-pressure refrigerant from flowing toward the outdoor electric valve 50 is provided between the outdoor electric valve 50 and the outdoor heat. Between the 4th heat exchanger 44 of the exchanger 40, the 4th check valve 54 which stops that a high voltage | pressure refrigerant | coolant flows toward the outdoor motor operated valve 50 is provided, respectively.

  The first intercooler pipe 41a, the second intercooler pipe 42a, and the third intercooler pipe 43a described above are respectively disposed between the first heat exchanger 41 and the first check valve 51, and the second heat exchanger 42. It branches from between the second check valve 52 and between the third heat exchanger 43 and the third check valve 53. During the cooling operation, the outdoor motor operated valve 50 is fully closed. On the other hand, during the heating operation, the outdoor motor operated valve 50 functions as an expansion mechanism. During the heating operation, the low-pressure refrigerant depressurized by the outdoor electric valve 50 is divided into four flows by the flow divider, each passing through the first check valve 51 to the first heat exchanger 41 and the second check valve 52. Through the second heat exchanger 42, through the third check valve 53 to the third heat exchanger 43, and through the fourth check valve 54 to the fourth heat exchanger 44. Capillary tubes are provided between the first to fourth check valves 51 to 54 and the first to fourth heat exchangers 41 to 44, and each capillary tube is connected to the first electric motor valve 50 from the first electric valve 50. The length is adjusted so that the refrigerant flowing to the fourth heat exchangers 41 to 44 does not drift.

(1-5) Check valve circuit The check valve circuit 55 is provided between the outdoor heat exchanger 40 and the indoor heat exchanger 12a, and includes an economizer heat exchanger 61, an internal heat exchanger 62, and an expansion mechanism. It is connected to the inlet pipe 81 of the receiver 80 via 70, and is connected to the outlet pipe 82 of the receiver 80 via the supercooling heat exchanger 90.

  The check valve circuit 55 includes three check valves 55a, 55b, and 55d. The inlet check valve 55 a is a check valve that allows only the flow of refrigerant from the fourth heat exchanger 44 of the outdoor heat exchanger 40 toward the inlet pipe 81 of the receiver 80. The inlet check valve 55b is a check valve that allows only a refrigerant flow from the indoor heat exchanger 12a to the inlet pipe 81 of the receiver 80. The outlet check valve 55d is a check valve that allows only the flow of refrigerant from the outlet pipe 82 of the receiver 80 toward the indoor heat exchanger 12a.

  Due to the presence of the check valve circuit 55 and the outdoor motor-operated valve 50, in any operation, the refrigerant flows into the economizer heat exchanger 61, the internal heat exchanger 62, the expansion mechanism 70, the receiver 80, and the supercooling heat exchanger 90 in order. Flowing.

(1-6) Economizer Heat Exchanger The economizer heat exchanger 61 is an intermediate in which a high-pressure refrigerant heading from the check valve circuit 55 to the expansion mechanism 70 and the receiver 80 and a part of the high-pressure refrigerant are branched and expanded. Heat exchange with the pressure refrigerant. A fifth outdoor motor-operated valve 61b is disposed in a pipe (injection pipe 61a) branched from the main refrigerant pipe that flows the refrigerant from the check valve circuit 55 to the expansion mechanism 70. The refrigerant that has expanded through the fifth outdoor motor-operated valve 61b and evaporated in the economizer heat exchanger 61 passes through the injection pipe 61a extending toward the second intercooler pipe 42a, and the check of the second intercooler pipe 42a. The refrigerant that flows into the portion closer to the third suction pipe 23a than the valve and cools the refrigerant sucked into the third compression section 23 from the third suction pipe 23a is cooled.

(1-7) Internal Heat Exchanger The internal heat exchanger 62 passes through the high-pressure refrigerant from the check valve circuit 55 to the expansion mechanism 70 and the receiver 80, the expansion mechanism 70, etc. and passes through the indoor heat exchanger 12a or the outdoor Heat exchange is performed with the low-pressure gas refrigerant that evaporates in the heat exchanger 40 and flows through the low-pressure refrigerant pipe 19. The internal heat exchanger 62 is sometimes called a liquid gas heat exchanger. The high-pressure refrigerant that has exited the check valve circuit 55 first passes through the economizer heat exchanger 61, then passes through the internal heat exchanger 62, and travels toward the expansion mechanism 70 and the receiver 80.

(1-8) Expansion Mechanism The expansion mechanism 70 depressurizes and expands the high-pressure refrigerant that has flowed from the check valve circuit 55 and causes the intermediate-pressure refrigerant in a gas-liquid two-phase state to flow to the receiver 80. That is, during the cooling operation, the expansion mechanism 70 receives the refrigerant sent from the outdoor fourth heat exchanger 44 functioning as a high-pressure refrigerant gas cooler (heat radiator) to the indoor heat exchanger 12a functioning as an evaporator of low-pressure refrigerant. During the heating operation, the refrigerant sent from the indoor heat exchanger 12a functioning as a high-pressure refrigerant gas cooler (radiator) to the outdoor heat exchanger 40 functioning as a low-pressure refrigerant evaporator is decompressed. The expansion mechanism 70 includes an expander 71 and a sixth outdoor electric valve 72. The expander 71 plays a role of recovering the throttle loss in the decompression process of the refrigerant as effective work (energy).

(1-9) Receiver The receiver 80 separates the intermediate-pressure refrigerant in the gas-liquid two-phase state that has exited the expansion mechanism 70 and entered the internal space from the inlet pipe 81 into liquid refrigerant and gas refrigerant. The separated gas refrigerant passes through a seventh outdoor motor-operated valve 91 provided in the low-pressure return pipe 91 a to become a low-pressure gas-rich refrigerant and is sent to the supercooling heat exchanger 90. The separated liquid refrigerant is sent to the supercooling heat exchanger 90 through the outlet pipe 82.

(1-10) Supercooling Heat Exchanger The supercooling heat exchanger 90 performs heat exchange between the low-pressure gas refrigerant and the intermediate-pressure liquid refrigerant output from the outlet pipe 82 of the receiver 80. Part of the intermediate-pressure liquid refrigerant that has exited from the outlet pipe 82 of the receiver 80 flows through the branch pipe 92a that branches from between the receiver 80 and the supercooling heat exchanger 90 during the cooling operation, and the eighth outdoor motor-operated valve 92. And becomes a low-pressure refrigerant in a gas-liquid two-phase state. The low-pressure refrigerant depressurized by the eighth outdoor motor-operated valve 92 during the cooling operation merges with the low-pressure refrigerant depressurized by the seventh outdoor motor-operated valve 91, and in the supercooling heat exchanger 90, a check is made from the outlet pipe 82 of the receiver 80. Heat exchange is performed with the intermediate-pressure liquid refrigerant toward the valve circuit 55, and the supercooled heat exchanger 90 flows from the supercooling heat exchanger 90 to the low-pressure refrigerant pipe 19 through the low-pressure return pipe 91a. On the other hand, the intermediate-pressure liquid refrigerant from the outlet pipe 82 of the receiver 80 toward the check valve circuit 55 is deprived of heat in the supercooling heat exchanger 90 and flows to the check valve circuit 55 in a state of being supercooled. Go.

  During the heating operation, the eighth outdoor motor-operated valve 92 is closed, and the refrigerant does not flow into the branch pipe 92a. However, the intermediate-pressure liquid refrigerant from the outlet pipe 82 of the receiver 80 and the seventh outdoor motor-operated valve 91 reduce the pressure. The low-pressure refrigerant that has been subjected to heat exchange in the supercooling heat exchanger 90.

(1-11) Indoor Heat Exchanger The indoor heat exchanger 12a is provided in each of the plurality of indoor units 12, and functions as a refrigerant evaporator during a cooling operation and as a refrigerant cooler during a heating operation. Water and air are flown through these indoor heat exchangers 12a as cooling targets or heating targets that exchange heat with the refrigerant flowing in the interior. Here, indoor air from an indoor fan (not shown) flows into the indoor heat exchanger 12a, and cooled or heated conditioned air is supplied into the room.

  One end of the indoor heat exchanger 12a is connected to the indoor motor-operated valve 12b, and the other end of the indoor heat exchanger 12a is connected to the communication refrigerant pipe 14.

(1-12) Indoor Motorized Valve The indoor motorized valve 12b is provided in each of the plurality of indoor units 12, and adjusts the amount of refrigerant flowing through the indoor heat exchanger 12a, or performs decompression / expansion of the refrigerant. The indoor motor operated valve 12b is disposed between the communication refrigerant pipe 13 and the indoor heat exchanger 12a.

(1-13) Control Unit The control unit 10a is configured by connecting each control board on which the electronic components of the outdoor unit 11 and the indoor unit 12 are mounted with communication lines. As shown in FIG. The compressor drive motor of the four-stage compressor 20, the first to fourth four-way switching valves 31 to 34, the defrosting three-way valve 37, and the motor-operated valves 12 b, 50, 61 b, 72, 91, 92 are connected. The control unit 10a controls the rotational speed of the compressor drive motor, adjusts the opening of the motor-operated valve, and the like based on information such as the indoor set temperature input from the outside, measured values of a temperature sensor and a pressure sensor (not shown), and the like. .

  The control unit 10a has a cooling operation mode, a heating operation mode, and a defrosting operation mode for melting frost attached to the first to fourth heat exchangers 41 to 44 of the outdoor unit 11, and selects any one of the operations. Do it. In the defrosting operation, the control unit 10a causes one of the first to fourth heat exchangers 41 to 44 to function as a radiator and the other three heat exchangers to function as an evaporator, The heat exchanger 12a always functions as a heat radiator. Specifically, in the defrosting operation mode, the control unit 10a sequentially executes the four stages shown in FIGS. In the first stage of the defrosting operation, the fourth heat exchanger 44 functions as a radiator, the first to third heat exchangers 41-43 function as an evaporator, and the indoor heat exchanger 12a functions as a radiator. Let In the second stage of the defrosting operation, the third heat exchanger 43 functions as a radiator and the first, second, and fourth heat exchangers 41, 42, and 44 function as evaporators, and the indoor heat exchanger 12a To function as a radiator. In the third stage of the defrosting operation, the second heat exchanger 42 functions as a radiator and the first, third and fourth heat exchangers 41, 43, 44 function as evaporators, and the indoor heat exchanger 12a To function as a radiator. In the fourth stage of the defrosting operation, the first heat exchanger 41 functions as a radiator, the second to fourth heat exchangers 42-44 function as an evaporator, and the indoor heat exchanger 12a functions as a radiator. Let 7B to 7E, the hatched heat exchanger functions as a radiator, and the hatched heat exchanger functions as an evaporator. As is clear from FIGS. 7B to 7E, the three heat exchangers of the outdoor unit 11 function as evaporators in any stage of the defrosting operation.

(2) Operation of Air Conditioner The operation of the air conditioner 10 executed by the control unit 10a will be described with reference to the drawings. 2, 4, 9, 11, 13, and 15 show the refrigeration cycle in the first stage, the second stage, the third stage, and the fourth stage of the cooling operation, the heating operation, and the defrosting operation, respectively. It is a pressure-enthalpy diagram (ph diagram). In each of these drawings, the curves indicated by the one-dot chain line that protrudes upward are the saturated liquid line and the dry saturated vapor line of the refrigerant. Moreover, in each figure, the point which the English letter on the refrigerating cycle was attached | subjected is respectively the point of the refrigerant | coolant in the point represented by the same alphabetic letter in FIG.1, FIG.3, FIG.8, FIG. Represents pressure and enthalpy. For example, the refrigerant at point B in FIG. 1 is in the state of pressure and enthalpy at point B in FIG. In addition, each operation control in the air_conditionaing | cooling operation of the air conditioning apparatus 10, heating operation, and a defrost operation is performed by the control part 10a.

(2-1) Operation in the cooling operation mode During the cooling operation, the refrigerant moves in the direction of the arrow along the refrigerant pipe shown in FIG. 1 into the four-stage compressor 20, the outdoor heat exchanger 40, the expansion mechanism 70, It circulates in the refrigerant circuit in the order of the indoor heat exchanger 12a. The four-way switching valves 31 to 34 function the heat exchangers 41 to 44 as coolers for the refrigerant compressed by the four-stage compressor 20 during the cooling operation, and pass through the expansion mechanism 70 and the indoor electric valve 12b. Then, the state shown in FIG. 1 is obtained so that the indoor heat exchanger 12a functions as an evaporator (heater) of the expanded refrigerant. Further, as described above, the defrosting three-way valve 37 connects the fourth four-way switching valve 34 and the fourth heat exchanger 44 by communicating the second refrigerant pipe 44g and the fourth cooling inlet pipe 44f. 1 state. Hereinafter, operation | movement of the air conditioning apparatus 10 at the time of air_conditionaing | cooling operation is demonstrated, referring FIG. 1 and FIG.

  The low-pressure gas refrigerant (point A) sucked into the four-stage compressor 20 from the first suction pipe 21a is compressed by the first compression section 21 and discharged to the first discharge pipe 21b (point B). The discharged refrigerant passes through the first four-way switching valve 31, is cooled by the first heat exchanger 41 functioning as an intercooler, and then flows into the second suction pipe 22a via the first intercooler pipe 41a. (Point C).

  The refrigerant sucked into the second compression part 22 from the second suction pipe 22a is compressed and discharged to the second discharge pipe 22b (point D). The discharged refrigerant passes through the second four-way switching valve 32, is cooled by the second heat exchanger 42 functioning as an intercooler, and then flows to the second intercooler pipe 42a (point E). The refrigerant flowing through the second intercooler pipe 42a is heat-exchanged in the economizer heat exchanger 61 and merged with the intermediate pressure refrigerant (point L) flowing through the injection pipe 61a, and then flows into the third suction pipe 23a (point). F).

  The refrigerant sucked into the third compression section 23 from the third suction pipe 23a is compressed and discharged to the third discharge pipe 23b (point G). The discharged refrigerant passes through the third four-way switching valve 33, is cooled by the third heat exchanger 43 functioning as an intercooler, and then flows into the fourth suction pipe 24a via the third intercooler pipe 43a. (Point H).

  The refrigerant sucked into the fourth compression section 24 from the fourth suction pipe 24a is compressed and discharged to the fourth discharge pipe 24b (point I). The discharged high-pressure refrigerant passes through the fourth four-way switching valve 34 and the defrosting three-way valve 37, is cooled by the fourth heat exchanger 44 that functions as a gas cooler, and enters the check valve of the check valve circuit 55. It flows to the economizer heat exchanger 61 through 55a (point J).

  The high-pressure refrigerant that has passed through the inlet check valve 55a of the check valve circuit 55 flows into the economizer heat exchanger 61, and a part thereof branches to flow to the fifth outdoor motor-operated valve 61b. The intermediate-pressure refrigerant (point K) that has been reduced in pressure and expanded by the fifth outdoor motor operated valve 61b into a gas-liquid two-phase state is subjected to high pressure from the check valve circuit 55 to the internal heat exchanger 62 in the economizer heat exchanger 61. The refrigerant exchanges heat with the refrigerant (point J), becomes an intermediate-pressure gas refrigerant (point L), and flows into the second intercooler pipe 42a from the injection pipe 61a as described above.

  The high-pressure refrigerant (point M) that has exchanged heat with the intermediate-pressure refrigerant that has exited the fifth outdoor motor-operated valve 61b and has exited the economizer heat exchanger 61 in a state where the temperature has further decreased, then flows through the internal heat exchanger 62. And flows to the expansion mechanism 70 (point N). In the internal heat exchanger 62, heat exchange is performed with the low-pressure refrigerant flowing from the low-pressure refrigerant pipe 19 described later to the first suction pipe 21 a of the four-stage compressor 20, and the high-pressure refrigerant in the state of point M drops in temperature. It becomes a high-pressure refrigerant in the N state.

  The high-pressure refrigerant (point N) exiting the internal heat exchanger 62 is branched into two and flows to the expander 71 of the expansion mechanism 70 and the sixth outdoor motor-operated valve 72 of the expansion mechanism 70, respectively. The intermediate pressure refrigerant (point P) decompressed / expanded by the expander 71 and the intermediate pressure refrigerant (point O) decompressed / expanded by the sixth outdoor motor-operated valve 72 are joined to the internal space of the receiver 80 from the inlet pipe 81. (Point Q). The gas-liquid two-phase intermediate pressure refrigerant flowing into the receiver 80 is separated into liquid refrigerant and gas refrigerant in the internal space of the receiver 80.

  The liquid refrigerant (point R) separated by the receiver 80 flows as it is to the supercooling heat exchanger 90 through the outlet pipe 82, and the gas refrigerant (point U) separated by the receiver 80 is the seventh outdoor motor valve. The pressure is reduced at 91 to form a low-pressure refrigerant (point W) and flow to the supercooling heat exchanger 90. The intermediate pressure refrigerant from the outlet pipe 82 of the receiver 80 toward the supercooling heat exchanger 90 branches before the supercooling heat exchanger 90, and one of the refrigerant passes through the supercooling heat exchanger 90 and goes to the check valve circuit 55. The other flows to the eighth outdoor motor-operated valve 92 of the branch pipe 92a. The low-pressure refrigerant (point S) in the gas-liquid two-phase state that has been decompressed after passing through the eighth outdoor motor-operated valve 92 merges with the low-pressure refrigerant (point W) that has passed through the seventh outdoor motor-operated valve 91 (point X), It flows to the low-pressure refrigerant pipe 19 through the supercooling heat exchanger 90. Due to the heat exchange in the supercooling heat exchanger 90, the low pressure refrigerant (point X) flowing toward the low pressure refrigerant pipe 19 evaporates to become a superheated low pressure refrigerant (point Y) and moves toward the check valve circuit 55. The intermediate-pressure refrigerant (point R) flowing in the direction becomes an intermediate-pressure refrigerant (point T) that is supercooled due to heat being deprived.

  The intermediate pressure refrigerant (point T) that has been supercooled by the supercooling heat exchanger 90 flows to the communication refrigerant pipe 13 through the outlet check valve 55 d of the check valve circuit 55. The refrigerant that has entered the indoor unit 12 from the communication refrigerant pipe 13 expands when passing through the indoor motor-operated valve 12b, and flows into the indoor heat exchanger 12a as a gas-liquid two-phase low-pressure refrigerant (point V). This low-pressure refrigerant takes heat from the indoor air in the indoor heat exchanger 12a and becomes a superheated low-pressure gas refrigerant (point Z). The low-pressure refrigerant exiting the indoor unit 12 flows to the low-pressure refrigerant pipe 19 via the communication refrigerant pipe 14, the first refrigerant pipe 18 and the fourth four-way switching valve 34.

  The low-pressure refrigerant (point Z) returned from the indoor unit 12 and the low-pressure refrigerant (point Y) flowing from the supercooling heat exchanger 90 merge at the low-pressure refrigerant pipe 19 (point AB), and the internal heat exchanger. The first suction pipe 21 a returns to the four-stage compressor 20 through 62. As described above, in the internal heat exchanger 62, the low-pressure refrigerant (point AB) that goes to the four-stage compressor 20 and the high-pressure refrigerant (point M) that goes from the check valve circuit 55 to the receiver 80 exchange heat. .

  As described above, the refrigerant circulates in the refrigerant circuit, so that the air conditioner 10 performs the cooling operation cycle.

(2-2) Operation in the heating operation mode During the heating operation, the refrigerant flows in the direction of the arrow along the refrigerant pipe shown in FIG. 3, the four-stage compressor 20, the indoor heat exchanger 12 a, the expansion mechanism 70, It circulates in the refrigerant circuit in the order of the outdoor heat exchanger 40. The four-way switching valves 31 to 34 function the indoor heat exchanger 12a as a refrigerant cooler (radiator) compressed by the four-stage compressor 20 during the heating operation, and the expansion mechanism 70 and the outdoor electric valve The state shown in FIG. 3 is set so that the outdoor heat exchanger 40 functions as an evaporator of the refrigerant that has passed through 50 and expanded. Further, as described above, the defrosting three-way valve 37 connects the fourth four-way switching valve 34 and the fourth heat exchanger 44 by communicating the second refrigerant pipe 44g and the fourth cooling inlet pipe 44f. 1 state. Hereinafter, operation | movement of the air conditioning apparatus 10 at the time of heating operation is demonstrated, referring FIG. 3 and FIG.

  The low-pressure gas refrigerant (point A) sucked into the four-stage compressor 20 from the first suction pipe 21a is compressed by the first compression section 21 and discharged to the first discharge pipe 21b (point B). The discharged refrigerant passes through the first four-way switching valve 31 and flows through the second suction pipe 22a (point C).

  The refrigerant sucked into the second compression part 22 from the second suction pipe 22a is compressed and discharged to the second discharge pipe 22b (point D). The discharged refrigerant passes through the second four-way switching valve 32 and flows through the third suction pipe 23a. In addition, since the intermediate pressure refrigerant (point L) that is heat-exchanged in the economizer heat exchanger 61 and flows through the injection pipe 61a also flows into the third suction pipe 23a, the temperature of the refrigerant decreases (point F). .

  The refrigerant sucked into the third compression section 23 from the third suction pipe 23a is compressed and discharged to the third discharge pipe 23b (point G). The discharged refrigerant passes through the third four-way switching valve 33 and flows through the fourth suction pipe 24a (point H).

  The refrigerant sucked into the fourth compression section 24 from the fourth suction pipe 24a is compressed and discharged to the fourth discharge pipe 24b (point I). The discharged high-pressure refrigerant passes through the fourth four-way switching valve 34 and flows into the indoor unit 12 through the communication refrigerant pipe 14 (point Z).

  The high-pressure refrigerant that has entered the indoor unit 12 from the communication refrigerant pipe 14 radiates heat to the indoor air in the indoor heat exchanger 12a that functions as a refrigerant cooler, and warms the indoor air. The high-pressure refrigerant (point V) whose temperature has decreased due to heat exchange in the indoor heat exchanger 12a is slightly decompressed when passing through the indoor motor-operated valve 12b, passes through the communication refrigerant pipe 13, and the check valve of the outdoor unit 11 It flows to the circuit 55, and goes to the economizer heat exchanger 61 from the inlet check valve 55b (point J).

  The high-pressure refrigerant (point J) that has exited the check valve circuit 55 flows into the economizer heat exchanger 61, and a part of the high-pressure refrigerant branches to the fifth outdoor motor-operated valve 61b. The intermediate-pressure refrigerant (point K), which has been reduced in pressure and expanded by the fifth outdoor electric valve 61b and brought into a gas-liquid two-phase state, is increased in pressure in the economizer heat exchanger 6 from the check valve circuit 55 to the internal heat exchanger 62. The refrigerant exchanges heat with the refrigerant (point J), becomes an intermediate-pressure gas refrigerant (point L), and flows from the injection pipe 61a into the second intercooler pipe 42a.

  The high-pressure refrigerant (point M) that has exchanged heat with the intermediate-pressure refrigerant that has exited the fifth outdoor motor-operated valve 61b and has exited the economizer heat exchanger 61 in a state where the temperature has further decreased, then flows through the internal heat exchanger 62. And flows to the expansion mechanism 70 (point N). In the internal heat exchanger 62, heat exchange is performed with the low-pressure refrigerant flowing from the low-pressure refrigerant pipe 19 described later to the first suction pipe 21 a of the four-stage compressor 20, and the high-pressure refrigerant in the state of point M drops in temperature. It becomes a high-pressure refrigerant in the N state.

  The high-pressure refrigerant (point N) exiting the internal heat exchanger 62 is branched into two and flows to the expander 71 of the expansion mechanism 70 and the sixth outdoor motor-operated valve 72 of the expansion mechanism 70, respectively. The intermediate pressure refrigerant (point P) decompressed / expanded by the expander 71 and the intermediate pressure refrigerant (point O) decompressed / expanded by the sixth outdoor motor-operated valve 72 are joined to the internal space of the receiver 80 from the inlet pipe 81. (Point Q). The gas-liquid two-phase intermediate pressure refrigerant flowing into the receiver 80 is separated into liquid refrigerant and gas refrigerant in the internal space of the receiver 80.

  The liquid refrigerant (point R) separated by the receiver 80 flows as it is to the supercooling heat exchanger 90 through the outlet pipe 82, and the gas refrigerant (point U) separated by the receiver 80 is the seventh outdoor motor valve. The pressure is reduced at 91 to form a low-pressure refrigerant (point W) and flow to the supercooling heat exchanger 90. The intermediate pressure refrigerant from the outlet pipe 82 of the receiver 80 toward the supercooling heat exchanger 90 does not flow into the branch pipe 92a because the eighth outdoor motor-operated valve 92 is closed, and the entire amount flows into the supercooling heat exchanger 90. . In the supercooling heat exchanger 90, heat is generated between the intermediate-pressure refrigerant (point R) flowing from the outlet pipe 82 of the receiver 80 and the low-pressure refrigerant (points W and X) decompressed by the seventh outdoor motor-operated valve 91. Exchange is performed. By this heat exchange, the low-pressure refrigerant (point X) flowing toward the low-pressure refrigerant pipe 19 evaporates to become superheated low-pressure refrigerant (point Y), and the intermediate-pressure refrigerant (point Y) from the receiver 80 toward the check valve circuit 55 Point R) is an intermediate pressure refrigerant (point T) that has been deprived of heat and is supercooled.

  The intermediate pressure refrigerant that has exited the supercooling heat exchanger 90 passes through the outdoor motor-operated valve 50 and then is divided into four paths. The gas-liquid two-phase low-pressure refrigerant (point AC) depressurized and expanded in the outdoor motor-operated valve 50 and the capillary tube after the branching flow includes a first heat exchanger 41, a second heat exchanger 42, a third heat exchanger 43, and It flows into the fourth heat exchanger 44. And the low-pressure refrigerant | coolant of each path takes heat from outside air in each heat exchanger 41-44, evaporates, becomes a low-pressure gas refrigerant with overheating, and the 1st-4th four-way switching valves 31-34. After passing through, merge (point AD).

  The low-pressure refrigerant (point AD) after the merge is merged with the low-pressure refrigerant (point Y) flowing from the supercooling heat exchanger 90 (point AB) through the low-pressure refrigerant pipe 19, and passes through the internal heat exchanger 62. The suction pipe 21a returns to the four-stage compressor 20. As described above, in the internal heat exchanger 62, the low-pressure refrigerant (point AB) that goes to the four-stage compressor 20 and the high-pressure refrigerant (point M) that goes from the check valve circuit 55 to the receiver 80 exchange heat. .

  As described above, the refrigerant circulates in the refrigerant circuit, whereby the air conditioner 10 performs the heating operation cycle.

(2-3) Operation in the defrosting operation mode The controller 10a automatically performs the defrosting operation when the outdoor heat exchanger 40 is easily frosted (conditions such as the outside air temperature) during the heating operation. Enter the mode and execute the defrosting operation. This defrosting operation is not an operation in which the indoor heat exchanger 12a is used as an evaporator, and the first to fourth heat exchangers 41 to 41 in the outdoor heat exchanger 40 are kept functioning while the indoor heat exchanger 12a continues to function as a radiator. In this operation, the intermediate pressure or high-pressure refrigerant from the four-stage compressor 20 is flowed to 44 in order, and the frost of each of the heat exchangers 41 to 44 is melted. In addition, after a defrost operation, it returns to heating operation mode automatically and performs heating operation.

  In the defrosting operation, the control unit 10a allows the intermediate pressure or high-pressure refrigerant from the four-stage compressor 20 to flow in order from the first to fourth heat exchangers 41 to 44 arranged above. Specifically, as shown in FIG. 7, when the defrosting condition is established during the heating operation (A), the defrosting operation is started, and first, the first stage (B) is arranged at the top. The high-pressure refrigerant flows through the fourth heat exchanger 44, then the intermediate-pressure refrigerant from the four-stage compressor 20 flows through the third heat exchanger 43 in the second stage (C), and then in the third stage (D). The intermediate pressure refrigerant from the four-stage compressor 20 is supplied to the second heat exchanger 42, and the intermediate pressure refrigerant from the four-stage compressor 20 is supplied to the first heat exchanger 41 in the final fourth stage (E).

  Hereinafter, each stage of the defrosting operation will be described with reference to the drawings.

(2-3-1) First Stage of Defrosting Operation In the first stage of the defrosting operation, the refrigerant flows in the direction of the arrow along the refrigerant pipe shown in FIG. The four-way switching valves 31 to 34 are in the same state as in the heating operation, but the defrosting three-way valve 37 is connected to the defrosting pipe 36 and the fourth cooling inlet pipe 44f as described above. Switch to state. Hereinafter, operation | movement of the air conditioning apparatus 10 in the 1st stage of a defrost operation is demonstrated, abbreviate | omitting the same part as operation | movement of heating operation.

  The operation is the same as in the heating operation until the low-pressure gas refrigerant (point A) sucked into the four-stage compressor 20 from the first suction pipe 21a is discharged to the fourth discharge pipe 24b (point I).

  The high-pressure refrigerant discharged from the four-stage compressor 20 passes through the fourth four-way switching valve 34 and flows into the indoor unit 12 via the first refrigerant pipe 18 and the communication refrigerant pipe 14 (point Z). The refrigerant flows from the fourth cooling inlet pipe 44f to the fourth heat exchanger 44 through the defrosting pipe 36 and the defrosting three-way valve 37 branched from the first refrigerant pipe 18 (point Z1). The high-pressure refrigerant that has flowed from the first refrigerant pipe 18 to the fourth heat exchanger 44 dissipates heat in the fourth heat exchanger 44 to melt frost, and exits the fourth heat exchanger 44 (point E1). The high-pressure refrigerant that has flowed into one indoor unit 12 radiates heat to the indoor air by the indoor heat exchanger 12a, and the check of the outdoor unit 11 passes through the indoor motor-operated valve 12b and the communication refrigerant pipe 13, as in the heating operation. It flows to the valve circuit 55.

  The refrigerant exiting the fourth heat exchanger 44 and passing through the inlet check valve 55a of the check valve circuit 55 and the refrigerant exiting the indoor heat exchanger 12a and slightly depressurized by the indoor electric valve 12b are introduced into the check valve circuit 55. The refrigerant that has passed through the check valve 55b joins and flows into the economizer heat exchanger 61 (point J).

  The operation from the economizer heat exchanger 61 to the outdoor electric valve 50 is the same as that during the heating operation. Since the low-pressure refrigerant that has passed through the outdoor electric valve 50 does not flow into the fourth heat exchanger 44 through which the high-pressure refrigerant flows, the low-pressure refrigerant is divided into three paths and passes through the first to third check valves 51, 52, 53 ( Point AC), and flows into the first to third heat exchangers 41 to 43. The low-pressure refrigerant in each path takes heat from the outside air in each heat exchanger 41-43 and evaporates, and passes through the first to third four-way switching valves 31-33 as a superheated low-pressure gas refrigerant. To join (point AD). The low-pressure refrigerant (point AD) after joining returns to the four-stage compressor 20 from the first suction pipe 21a through the internal heat exchanger 62 as in the heating operation.

  As described above, the refrigerant circulates in the refrigerant circuit, so that the air conditioner 10 radiates the indoor air in the indoor heat exchanger 12a to continue the heating function, and at the first stage of the defrosting operation, first, the outdoor The frost of the fourth heat exchanger 44 is melted and removed.

(2-3-2) Second Stage of Defrosting Operation In the second stage of the defrosting operation, the frost of the third heat exchanger 43 located immediately below the fourth heat exchanger 44 is removed. Here, the refrigerant flows in the direction of the arrow along the refrigerant pipe shown in FIG. The four-way switching valves 31, 32, and 34 are in the same state as in the heating operation, but the third four-way switching valve 33 is switched to the same state as in the cooling operation. Moreover, the three-way valve 37 for defrosting switches to the same 1st state as the time of heating operation. Hereinafter, operation | movement of the air conditioning apparatus 10 in the 2nd stage of a defrost operation is demonstrated, abbreviate | omitting the part same as the operation | movement of heating operation.

  Until the low-pressure gas refrigerant (point A) sucked into the four-stage compressor 20 from the first suction pipe 21a is discharged to the third discharge pipe 23b of the third compressor 23 (point G), it is the same as the heating operation. It is.

  The intermediate pressure refrigerant (point G) discharged from the third discharge pipe 23b passes through the third four-way switching valve 33 and goes to the third heat exchanger 43 that functions as a radiator (point G1). In the third heat exchanger 43, the intermediate pressure refrigerant dissipates heat and melts frost. The intermediate pressure refrigerant that has exited the third heat exchanger 43 in a state where the temperature has decreased due to heat dissipation (point E2) flows into the fourth suction pipe 24a via the third intercooler pipe 43a (point H).

  The refrigerant sucked into the fourth compression section 24 from the fourth suction pipe 24a is compressed and discharged to the fourth discharge pipe 24b as in the heating operation, passes through the fourth four-way switching valve 34, and communicates with the refrigerant pipe. 14 flows into the indoor unit 12 via the point 14 (point Z).

  The operation from the flow into the indoor unit 12 to the passage through the outdoor motor operated valve 50 is the same as in the heating operation. Since the low-pressure refrigerant that has passed through the outdoor electric valve 50 does not flow into the third heat exchanger 43 through which the intermediate-pressure refrigerant flows, the low-pressure refrigerant is divided into three passages, and the first, second, and fourth check valves 51, 52, and 54. (Point AC) and flows into the first, second, and fourth heat exchangers 41, 42, and 44. The low-pressure refrigerant in each passage takes heat from the outside air in each heat exchanger 41, 42, 44 and evaporates to become a superheated low-pressure gas refrigerant, and the first, second and fourth four-way switching valves. It passes through 31, 32, 34 and merges (point AD). The low-pressure refrigerant (point AD) after joining returns to the four-stage compressor 20 from the first suction pipe 21a through the internal heat exchanger 62 as in the heating operation.

  As described above, the refrigerant circulates in the refrigerant circuit, so that the air conditioner 10 radiates the indoor air in the indoor heat exchanger 12a and continues the heating function, while the outdoor function is maintained in the second stage of the defrosting operation. The frost in the third heat exchanger 43 is melted and removed.

(2-3-3) Third Stage of Defrosting Operation In the third stage of the defrosting operation, the frost of the second heat exchanger 42 located immediately below the third heat exchanger 43 is removed. Here, the refrigerant flows in the direction of the arrow along the refrigerant pipe shown in FIG. The four-way switching valves 31, 33, 34 and the three-way defrosting valve 37 are in the same state as in the heating operation, but the second four-way switching valve 32 is switched to the same state as in the cooling operation. Hereinafter, the operation of the air conditioner 10 in the third stage of the defrosting operation will be described while omitting the same parts as the operation of the heating operation.

  Until the low-pressure gas refrigerant (point A) sucked into the four-stage compressor 20 from the first suction pipe 21a is discharged to the second discharge pipe 22b of the second compression section 22 (point D), it is the same as the heating operation. It is.

  The intermediate pressure refrigerant (point D) discharged from the second discharge pipe 22b passes through the second four-way switching valve 32 and travels to the second heat exchanger 42 that functions as a radiator (point D1). In the second heat exchanger 42, the intermediate-pressure refrigerant dissipates heat and melts frost. The intermediate pressure refrigerant that has exited the second heat exchanger 42 in a state where the temperature has decreased due to heat dissipation (point E3) flows into the second intercooler pipe 42a. The refrigerant flowing through the second intercooler pipe 42a is heat-exchanged in the economizer heat exchanger 61 and merged with the intermediate pressure refrigerant (point L) flowing through the injection pipe 61a, and then flows into the third suction pipe 23a (point). F).

  Regarding the flow of refrigerant, etc., from the third suction pipe 23a to the third compression section 23 until it leaves the four-stage compressor 20 and passes through the indoor heat exchanger 12b and the expansion mechanism 70 and the outdoor electric valve 50, etc. The same as during heating operation. Since the low-pressure refrigerant that has passed through the outdoor motor-operated valve 50 does not flow into the second heat exchanger 42 through which the intermediate-pressure refrigerant flows, the low-pressure refrigerant is divided into three passages, and the first, third, and fourth check valves 51, 53, and 54. (Point AC) and flows into the first, third, and fourth heat exchangers 41, 43, and 44. The low-pressure refrigerant in each passage takes heat from the outside air in each heat exchanger 41, 43, 44 and evaporates to become a superheated low-pressure gas refrigerant, and the first, third and fourth four-way switching valves. Passes 31, 33, 34 and merges (point AD). The low-pressure refrigerant (point AD) after joining returns to the four-stage compressor 20 from the first suction pipe 21a through the internal heat exchanger 62 as in the heating operation.

  As described above, the refrigerant circulates in the refrigerant circuit, so that the air conditioner 10 radiates the indoor air in the indoor heat exchanger 12a and continues the heating function, while the outdoor function is maintained in the third stage of the defrosting operation. The frost of the second heat exchanger 42 is melted and removed.

(2-3-4) Fourth Stage of Defrosting Operation In the fourth stage of the defrosting operation, the frost of the first heat exchanger 41 located immediately below the second heat exchanger 42 is removed. Here, the refrigerant flows in the direction of the arrow along the refrigerant pipe shown in FIG. The four-way switching valves 32 to 34 and the defrosting three-way valve 37 are in the same state as in the heating operation, but the first four-way switching valve 31 is switched to the same state as in the cooling operation. Hereinafter, operation | movement of the air conditioning apparatus 10 in the 4th stage of a defrost operation is demonstrated, abbreviate | omitting the part same as the operation | movement of heating operation.

  The low-pressure gas refrigerant (point A) sucked into the four-stage compressor 20 from the first suction pipe 21a is compressed by the first compression section 21 and discharged to the first discharge pipe 21b (point B). The discharged intermediate pressure refrigerant passes through the first four-way switching valve 31 and travels toward the first heat exchanger 41 that functions as a radiator (point B1). In the first heat exchanger 41, the intermediate-pressure refrigerant dissipates heat and melts frost. The intermediate pressure refrigerant that has exited the first heat exchanger 41 in a state where the temperature has decreased due to heat dissipation (point E4) flows into the second suction pipe 22a via the first intercooler pipe 41a (point C).

  Regarding the flow of refrigerant, etc., from the second suction pipe 22a to the second compression section 22 until it exits the four-stage compressor 20 and passes through the indoor heat exchanger 12b and the expansion mechanism 70 and the outdoor electric valve 50, etc. The same as during heating operation. Since the low-pressure refrigerant that has passed through the outdoor electric valve 50 does not flow into the first heat exchanger 41 through which the intermediate-pressure refrigerant flows, the low-pressure refrigerant is divided into three paths and passes through the second to fourth check valves 52 to 54 (points). AC), flows into the second to fourth heat exchangers 42 to 44. The low-pressure refrigerant in each path takes heat from the outside air in each heat exchanger 42 to 44 and evaporates, and becomes a low-pressure gas refrigerant with overheating and passes through the second to fourth four-way switching valves 32 to 34. To join (point AD). The low-pressure refrigerant (point AD) after joining returns to the four-stage compressor 20 from the first suction pipe 21a through the internal heat exchanger 62 as in the heating operation.

  As described above, the refrigerant circulates in the refrigerant circuit, so that the air conditioner 10 radiates the indoor air in the indoor heat exchanger 12a and continues the heating function, while maintaining the heating function in the fourth stage of the defrosting operation. The frost in the first heat exchanger 41 is melted and removed.

  The controller 10a automatically returns to the heating operation when the first to fourth stages of the defrosting operation that are executed for a predetermined time are finished.

(3) Features of the air conditioner (3-1)
In the air conditioning apparatus 10 according to the present embodiment, in the defrosting operation, the indoor heat exchanger 12a, which is the use-side heat exchanger as in the heating operation, functions as a radiator to warm the indoor air, The outdoor heat exchanger 40 is defrosted by causing a part of the first to fourth heat exchangers 41 to 44 to function as an evaporator and the rest to function as a radiator. In this defrosting operation, since the indoor heat exchanger 12a continues to radiate heat to the room air, there is almost no problem that the user of the air conditioner 10 in the room endures cold during the defrosting operation.

(3-2)
In this air conditioning apparatus 10, in the defrosting operation, the first stage to the fourth stage as shown in FIGS. 7B to 7E are executed, and the first to fourth heat exchangers 41 to 44 are sequentially operated. Defrosting is performed by making each work as a radiator. For this reason, although it takes a little time, at each stage of the defrosting operation, the three heat exchangers of the outdoor unit 11 can be secured as evaporators, and the indoor heat exchanger 12a can continue to function as a radiator. . For this reason, the fall of the heating capability at the time of a defrost operation mode is suppressed small, and even if it is a case where a user is dissatisfied with the fall of a heating capability, a user's discomfort degree can be suppressed small.

(3-3)
In the air conditioner 10, as described above, among the first to fourth heat exchangers 41 to 44 of the outdoor unit 11, the high pressure or intermediate voltage from the four-stage compressor 20 in order from the one arranged above. The refrigerant of pressure is flowing. That is, among the first to fourth heat exchangers 41 to 44, the heat exchanger disposed above the heat exchanger disposed below is given priority to function as a radiator, and disposed below in order. The heat exchanger that is being used is functioning as a radiator.

  For this reason, in the first stage of the defrosting operation, the frost of the fourth heat exchanger 44 located at the top is first melted, and the frost is melted to become water whose temperature has risen, and the third heat exchanger below it It flows to 43. Thereby, the frost of the 3rd heat exchanger 43 will melt a little, and the time which the 2nd stage of the defrost operation which melt | dissolves frost by using the 3rd heat exchanger 43 as a heat radiator shortens. Similarly, the time required for the third stage and the fourth stage of the defrosting operation is also shortened.

(3-4)
In the air conditioner 10, the low-pressure refrigerant evaporated in the indoor heat exchanger 12a flows during the cooling operation, and the high-pressure refrigerant discharged from the highest-stage fourth compression unit 24 of the four-stage compressor 20 is heated in the indoor operation. A defrosting pipe 36 directed to the fourth heat exchanger 44 is branched from the first refrigerant pipe 18 flowing toward the exchanger 12a. Further, in the air conditioner 10, only for the first stage of the defrosting operation, the defrosting is switched to the second state in which the defrosting pipe 36 and the fourth cooling inlet pipe 44f of the fourth heat exchanger 44 are communicated. A three-way valve 37 is provided. As a result, the high-temperature high-pressure refrigerant discharged from the four-stage compressor 20 is allowed to flow to the indoor heat exchanger 12a and to the outdoor fourth heat exchanger 44 (a heat source side heat exchanger that functions as a gas cooler during cooling operation). The frost attached to the fourth heat exchanger 44 can be melted while the indoor heat exchanger 12a functions as a radiator during the defrosting operation.

(4) Modification (4-1) Modification A
In the above embodiment, the defrosting operation is divided into the first to fourth stages, but two of the first to fourth heat exchangers 41 to 44 function as evaporators and the remaining two serve as radiators. It is also possible to perform a defrosting operation to function. For example, the second and third heat exchangers 42 and 43 function as heat radiators in the first stage, the first and fourth heat exchangers 41 and 44 function as heat radiators in the second stage, and indoors in both stages. It is also possible to keep the heat exchanger 12a functioning as a radiator.

  In addition, the fourth heat exchanger 44 functions as a radiator in the first stage and the first to third heat exchangers 41 to 43 function as evaporators. It is also possible to cause the chamber 44 to function as an evaporator and the first to third heat exchangers 41 to 43 to function as radiators and to keep the indoor heat exchanger 12a functioning as a radiator in both stages.

(4-2) Modification B
In the above embodiment, the present invention is applied to the air-conditioning apparatus 10 that includes the four-stage compressor 20 and the outdoor heat exchanger 40 includes the four heat exchangers 41 to 44. However, the two-stage compressor The present invention can also be applied to a refrigeration apparatus including

  16 to 18 show the refrigerant circuit of the air-conditioning apparatus 110 according to Modification B and the refrigerant flow. Here, the defrosting operation includes a first stage and a second stage. FIG. 16 shows the flow of the refrigerant circulating in the refrigerant circuit during the heating operation. FIG. 17 shows the flow of the refrigerant circulating in the refrigerant circuit in the first stage of the defrosting operation. FIG. 18 shows the flow of the refrigerant circulating in the refrigerant circuit in the second stage of the defrosting operation.

  Hereinafter, the air conditioner 110 will be described focusing on differences from the air conditioner 10 described above.

  The refrigerant circuit of the air conditioner 110 mainly includes a two-stage compressor 120, first and second four-way switching valves 131 and 134 as a first switching mechanism, a defrosting three-way valve 137 as a second switching mechanism, and an outdoor unit. Heat exchanger 140, outdoor electric valve 50, check valve circuit 55, economizer heat exchanger 61, internal heat exchanger 62, expansion mechanism 70, receiver 80, supercooling heat exchanger 90, indoor heat exchanger 12a, and indoor electric motor It consists of a valve 12b. The outdoor heat exchanger 140 includes a first heat exchanger 141 and a second heat exchanger 144 arranged in parallel.

  The two-stage compressor 120 is a hermetic compressor in which a low-stage compressor 121, a high-stage compressor 124, and a compressor drive motor (not shown) are accommodated. The compressor drive motor drives the two compression units 121 and 124 via the drive shaft. The low stage compression unit 121 sucks the refrigerant from the low stage suction pipe 121a and discharges the refrigerant to the low stage discharge pipe 121b. The high stage compression unit 124 sucks the refrigerant from the high stage suction pipe 124a and discharges the refrigerant to the high stage discharge pipe 124b.

  The first four-way switching valve 131 and the second four-way switching valve 134 are switching mechanisms that are provided to switch between the cooling operation cycle and the heating operation cycle by switching the direction of the refrigerant flow in the refrigerant circuit. . The first four-way switching valve 131 is connected to the low-stage discharge pipe 121b, the high-stage suction pipe 124a, the first cooling inlet pipe 141f extending to the first heat exchanger 141, and the low-pressure refrigerant pipe 19. The second four-way switching valve 134 is connected to the high-stage discharge pipe 124 b, the first refrigerant pipe 118 extending to the communication refrigerant pipe 14, the second refrigerant pipe 144 g extending to the second heat exchanger 144, and the low-pressure refrigerant pipe 19. Yes.

  Between the second refrigerant pipe 144g connected to the second four-way selector valve 134 and the second cooling inlet pipe 144f connected to the inlet side end of the second heat exchanger 144 during the cooling operation, there is no removal. A three-way valve 137 for frost is provided. The defrosting three-way valve 137 is further connected with a defrosting pipe 136 branched from the first refrigerant pipe 118 connecting the second four-way switching valve 134 and the communication refrigerant pipe 14. The defrosting three-way valve 137 communicates the second refrigerant piping 144g and the second cooling inlet piping 144f to connect the second four-way switching valve 134 and the second heat exchanger 144, and the defrosting The second state is switched between the pipe 136 and the second cooling inlet pipe 144f. The defrosting three-way valve 137 is in the second state only during the first stage of the defrosting operation, and is in the first state during the other stages of cooling operation, heating operation, and defrosting operation.

  In the outdoor heat exchanger 140, during the cooling operation, the first heat exchanger 141 functions as an intercooler that cools the refrigerant being compressed (intermediate pressure refrigerant), and the second heat exchanger 144 is a gas cooler that cools the high-pressure refrigerant. Function as. During the heating operation, both the first heat exchanger 141 and the second heat exchanger 144 function as a low-pressure refrigerant evaporator. The first heat exchanger 141 is arranged to be stacked on the second heat exchanger 144. Further, an intercooler pipe 141a that is a branch pipe extends from the pipe on the outdoor electric valve 50 side of the first heat exchanger 141 toward the high stage suction pipe 124a. As shown in FIG. 16, the intercooler pipe 141a is provided with a check valve.

  During the heating operation, the refrigerant circulates in the refrigerant circuit in the order of the two-stage compressor 120, the indoor heat exchanger 12a, the expansion mechanism 70, and the outdoor heat exchanger 140 in the direction of the arrow along the refrigerant pipe shown in FIG. To do. The four-way switching valves 131 and 134 cause the indoor heat exchanger 12a to function as a refrigerant cooler (radiator) compressed by the two-stage compressor 120 during heating operation, and the expansion mechanism 70 and the outdoor electric valve It will be in the state shown in FIG. 16 so that the outdoor heat exchanger 140 may function as an evaporator of the refrigerant | coolant expanded through 50. FIG. Further, the defrosting three-way valve 137 is in a first state in which the second four-way switching valve 134 and the second heat exchanger 144 are connected by communicating the second refrigerant pipe 144g and the second cooling inlet pipe 144f. Yes. The low-pressure gas refrigerant sucked into the two-stage compressor 120 from the low-stage suction pipe 121a is compressed by the low-stage compression section 121 and discharged to the low-stage discharge pipe 121b. The discharged intermediate pressure refrigerant passes through the first four-way switching valve 131 and flows through the high stage suction pipe 124a. The refrigerant sucked into the high stage compression unit 124 is compressed and discharged to the high stage discharge pipe 124b. The discharged high-pressure refrigerant passes through the second four-way switching valve 134 and flows into the indoor unit 12 through the communication refrigerant pipe 14. The operation from the flow into the indoor unit 12 to the passage through the outdoor motor operated valve 50 is the same as that during the heating operation of the air conditioner 10 described above. The gas-liquid two-phase low-pressure refrigerant decompressed and expanded in the outdoor electric valve 50 and the capillary tube after the two-way split flows into the first heat exchanger 141 and the second heat exchanger 144. And the low-pressure refrigerant | coolant of each path takes heat from outside air in each heat exchanger 141,144, evaporates, turns into a low-pressure gas refrigerant with overheating, and merges in the low-pressure refrigerant piping 19. The merged low-pressure refrigerant merges with the low-pressure refrigerant flowing from the supercooling heat exchanger 90, and returns to the two-stage compressor 120 from the low-stage intake pipe 121a through the internal heat exchanger 62.

  In the first stage of the defrosting operation, the refrigerant flows in the direction of the arrow along the refrigerant pipe shown in FIG. The four-way switching valves 131 and 134 are in the same state as in the heating operation, but the defrosting three-way valve 137 switches to the second state in which the defrosting pipe 136 and the second cooling inlet pipe 144f are communicated. As a result, the high-pressure refrigerant discharged from the two-stage compressor 120 passes through the second four-way switching valve 134 and flows into the indoor unit 12 via the first refrigerant pipe 118 and the communication refrigerant pipe 14, and It flows from the second cooling inlet pipe 144f to the second heat exchanger 144 through the defrosting pipe 136 and the defrosting three-way valve 137 branched from the first refrigerant pipe 118. The high-pressure refrigerant flowing from the first refrigerant pipe 118 to the second heat exchanger 144 dissipates heat in the second heat exchanger 144 and melts frost. The high-pressure refrigerant that has flowed into one indoor unit 12 radiates heat to the indoor air by the indoor heat exchanger 12a, and the check of the outdoor unit 11 passes through the indoor motor-operated valve 12b and the communication refrigerant pipe 13, as in the heating operation. It flows to the valve circuit 55. The refrigerant that has exited the second heat exchanger 144 and passed through the inlet check valve 55a of the check valve circuit 55 and the refrigerant that has exited the indoor heat exchanger 12a and is slightly depressurized by the indoor motor operated valve 12b are introduced into the check valve circuit 55. The refrigerant that has passed through the check valve 55 b joins and flows into the economizer heat exchanger 61. The operation from the economizer heat exchanger 61 through the outdoor electric valve 50 is the same as that during the heating operation of the air conditioner 10 described above. Since the low-pressure refrigerant that has passed through the outdoor electric valve 50 does not flow into the second heat exchanger 144 through which the high-pressure refrigerant flows, the low-pressure refrigerant passes through the first check valve 151 and flows into the first heat exchanger 141. In the first heat exchanger 141, heat is removed from the outside air to evaporate, and the superheated low-pressure gas refrigerant passes through the first four-way switching valve 131 and passes through the internal heat exchanger 62 from the low-pressure refrigerant pipe 19. Then, the low-stage suction pipe 121a returns to the two-stage compressor 120. As the refrigerant circulates in the refrigerant circuit in this way, the air conditioner 110 radiates heat to the indoor air by the indoor heat exchanger 12a and continues the heating function, while at the first stage of the defrosting operation, The frost in the second heat exchanger 144 is melted and removed.

  In the second stage of the defrosting operation, the frost of the first heat exchanger 141 located under the second heat exchanger 144 is removed. Here, the refrigerant flows in the direction of the arrow along the refrigerant pipe shown in FIG. The second four-way switching valve 134 is in the same state as in the heating operation, and the first four-way switching valve 131 is switched to the same state as in the cooling operation. In addition, the defrosting three-way valve 137 switches to the same first state as in the heating operation. The low-pressure gas refrigerant sucked into the two-stage compressor 120 from the low-stage intake pipe 121a is compressed by the low-stage compressor 121 and discharged to the low-stage discharge pipe 121b. The discharged refrigerant passes through the first four-way switching valve 131 and travels to the first heat exchanger 141 that functions as a radiator. In the first heat exchanger 141, the intermediate-pressure refrigerant dissipates heat and melts frost. The intermediate pressure refrigerant that has exited the first heat exchanger 141 in a state where the temperature has decreased due to heat dissipation flows into the high-stage suction pipe 124a via the intercooler pipe 141a. As for the flow of the refrigerant discharged from the high-stage compressor 124 of the two-stage compressor 120 and passing through the indoor heat exchanger 12b and the expansion mechanism 70 and the outdoor electric valve 50, the heating operation of the air conditioner 10 described above is performed. Same as time. Since the low-pressure refrigerant that has passed through the outdoor electric valve 50 does not flow into the first heat exchanger 141 through which the intermediate-pressure refrigerant flows, the low-pressure refrigerant passes through the second check valve 152 and flows into the second heat exchanger 144. This low-pressure refrigerant takes heat from the outside air in the second heat exchanger 144 and evaporates to become a superheated low-pressure gas refrigerant that passes through the defrosting three-way valve 137 and the second four-way switching valve 134. The low-pressure refrigerant pipe 19 flows. Thereafter, the low-pressure refrigerant joined with the refrigerant flowing from the supercooling heat exchanger 90 returns to the two-stage compressor 120 from the low-stage suction pipe 121a through the internal heat exchanger 62.

  As described above, the refrigerant circulates in the refrigerant circuit in the first and second stages of the defrosting operation, whereby the air conditioner 110 radiates heat to the indoor air in the indoor heat exchanger 12a and continues the heating function. The frost of the outdoor second heat exchanger 144 is melted in the first stage of the defrosting operation, and the frost of the outdoor first heat exchanger 141 is melted in the second stage of the defrosting operation. When the first and second stages of the defrosting operation are finished, the air conditioner 110 automatically returns to the heating operation.

10 Air conditioning equipment (refrigeration equipment)
10a Control unit 12a Indoor heat exchanger (use side heat exchanger)
18 First refrigerant piping 20 Four-stage compressor (multi-stage compression mechanism)
21 1st compression part (low stage compression part)
22 2nd compression part (high stage compression part; 2nd stage compression part)
23 3rd compression part (high stage compression part; 3rd stage compression part)
24 4th compression part (high stage compression part)
31 First four-way switching valve (first switching mechanism)
32 Second four-way switching valve (first switching mechanism)
33 Third four-way switching valve (first switching mechanism)
34 Fourth four-way switching valve (first switching mechanism)
36 Piping for defrosting 37 Three-way valve for defrosting (second switching mechanism)
40 Outdoor heat exchanger 41 1st heat exchanger (heat source side sub heat exchanger; heat source side 1st sub heat exchanger)
42 2nd heat exchanger (heat source side sub heat exchanger; heat source side second sub heat exchanger)
43 3rd heat exchanger (heat source side sub heat exchanger)
44 4th heat exchanger (heat source side main heat exchanger)
44f Second refrigerant pipe 70 Expansion mechanism 120 Two-stage compressor (multiple-stage compression mechanism)
121 Low stage compression section 124 High stage compression section 136 Defrosting pipe 137 Defrosting three-way valve (second switching mechanism)
140 Outdoor heat exchanger 141 1st heat exchanger (heat source side sub heat exchanger)
144 2nd heat exchanger (heat source side main heat exchanger)
144f Second refrigerant pipe

JP 2010-112618 A

Claims (5)

A multi-stage compression mechanism (20) in which a low-stage compression section (21) and a high-stage compression section (22, 23, 24) are connected in series;
A heat source side main heat exchanger (44) that functions as a radiator during cooling operation and functions as an evaporator during heating operation;
A heat source side sub heat exchanger (41-43) that functions as a radiator that cools the intermediate pressure refrigerant in the middle of compression sucked into the high-stage compression section during cooling operation, and functions as an evaporator during heating operation;
A use side heat exchanger (12a) that functions as an evaporator during cooling operation and functions as a radiator during heating operation;
During the cooling operation, the refrigerant is sent from the heat source side main heat exchanger to the use side heat exchanger, and during the heating operation, the heat source side main heat exchanger and the heat source side sub heat exchanger are transferred from the use side heat exchanger. A first switching mechanism (31-34), the state of which is switched so that the refrigerant is sent to
During the cooling operation, the refrigerant sent from the heat source side main heat exchanger to the use side heat exchanger is decompressed, and during the heating operation, the heat source side main heat exchanger and the heat source side sub heat are transferred from the use side heat exchanger. An expansion mechanism (70) for depressurizing the refrigerant sent to the exchanger;
A controller (10a) that selectively performs a cooling operation, a heating operation, and a defrosting operation for melting frost attached to the heat source side main heat exchanger and the heat source side sub heat exchanger;
With
In the defrosting operation, the control unit causes at least one of the heat source side main heat exchanger (44) and the heat source side sub heat exchanger (41 to 43) to function as an evaporator and the other. And the heat exchanger (12a) is made to function as a radiator.
Refrigeration equipment (10). In the defrosting operation, the control unit sequentially switches a heat exchanger that functions as a radiator among the heat source side main heat exchanger (44) and the heat source side sub heat exchanger (41 to 43).
The refrigeration apparatus according to claim 1. The heat source side main heat exchanger (44) and the heat source side sub heat exchangers (41 to 43) are arranged vertically so as to overlap each other in a plane,
In the defrosting operation, the control unit is disposed above a heat exchanger disposed below the heat source side main heat exchanger (44) and the heat source side sub heat exchanger (41 to 43). The heat exchanger that is being used is given priority to function as a radiator, and the heat exchangers that are arranged below are functioned as radiators in order.
The refrigeration apparatus according to claim 2. During the cooling operation, the low-pressure refrigerant evaporated in the use-side heat exchanger flows, and during the heating operation, the high-pressure refrigerant discharged from the highest-stage high-stage compression unit (24) of the multistage compression mechanism is the use-side heat. A first refrigerant pipe (18) flowing toward the exchanger;
A defrosting pipe (36) branched from the first refrigerant pipe (18) and directed to a second refrigerant pipe (44f) serving as an inlet pipe when the heat source side main heat exchanger functions as a radiator;
A second switching mechanism (37) for switching between a communication state in which the first refrigerant pipe (18), the defrosting pipe (36) and the second refrigerant pipe (44f) communicate with each other and a non-communication state in which the first refrigerant pipe (18), the defrosting pipe (44f) does not communicate with each other; ,
The refrigeration apparatus according to any one of claims 1 to 3, further comprising: The high-stage compression section includes a second-stage compression section (22) that sucks the refrigerant discharged from the low-stage compression section, and a third-stage compression section (suction) that sucks the refrigerant discharged from the second-stage compression section. 23),
The heat source side sub heat exchanger includes a heat source side first sub heat exchanger (41) that cools the refrigerant discharged from the low stage compression unit and sucked into the second stage compression unit during cooling operation, and the heat source side sub heat exchanger during the cooling operation. A heat source side second sub heat exchanger (42) for cooling the refrigerant discharged from the second stage compression section and sucked into the third stage compression section,
In the defrosting operation, the controller causes one heat exchanger of the heat source side main heat exchanger and the heat source side sub heat exchanger to function as a radiator and the remaining heat exchanger to function as an evaporator. , Causing the use side heat exchanger (12a) to function as a radiator,
The refrigeration apparatus according to any one of claims 1 to 4.

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