JP2014211292A - Refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerator comprising a heat source-side first heat exchanger performing multiple-stage compression, functioning as an evaporator in a first operation state, and functioning as a chiller in a second operation state; and a heat source-side second heat exchanger functioning as an evaporator provided in parallel to the heat source-side heat exchanger in the first operation state, and functioning as a chiller of refrigerant at an intermediate pressure in the second operation state, and capable of adjusting the overheat degree of merger refrigerant between refrigerant flowing out from the heat source-side first heat exchanger and that flowing out from the heat source-side second heat exchanger while ensuring an evaporation capability of either the heat source-side first heat exchanger or the heat source-side second heat exchanger in the first operation state.SOLUTION: If a fourth outdoor heat exchanger 44 and first to third outdoor heat exchangers 41 to 43 are made to function as evaporators connected in parallel in a first operation state, first and second outdoor expansion valves 47 and 48 are used to exert a control such that refrigerant on an outlet of the fourth outdoor heat exchanger 44 tends to be humid and that refrigerant at outlets of the first to third heat exchangers 41 to 43 tend to be dry.

Description

  The present invention relates to a refrigeration apparatus, and more particularly to a refrigeration apparatus including a multistage compression mechanism having a plurality of compression units.

  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 to the case where only the outdoor heat exchanger is used as the evaporator, the ability to evaporate the refrigerant is increased, so that the operation efficiency of the refrigeration apparatus can be increased by increasing the refrigerant circulation amount. .

  Here, for example, when the gas-liquid two-phase refrigerant depressurized by the expansion mechanism during the heating operation is divided and supplied in parallel to both the outdoor heat exchanger and the outdoor intermediate cooler, the outdoor heat exchanger and The refrigerant flowing out of the outdoor heat exchanger and the refrigerant flowing out of the outdoor intermediate cooler may be different from each other due to the difference in the capacity of the outdoor intermediate cooler or the difference in installation conditions.

  In this case, during the heating operation, when the combined refrigerant of the refrigerant flowing out of the outdoor heat exchanger and the refrigerant flowing out of the outdoor intermediate cooler is in a very dry state, the outdoor heat exchanger In either the outdoor intermediate cooler or the outdoor intermediate cooler, the evaporation capacity may not be sufficiently secured.

  On the other hand, during heating operation, in order to ensure large evaporation capacity in both the outdoor heat exchanger and the outdoor intermediate cooler, the outlet refrigerant of the outdoor heat exchanger and the outlet refrigerant of the outdoor intermediate cooler If control is performed so that the degree of superheat does not become excessively large in both (control is performed so that the region through which the superheated refrigerant flows is reduced in both the outdoor heat exchanger and the outdoor intermediate cooler. In other words, the refrigerant flowing out of the outdoor heat exchanger and the refrigerant flowing out of the outdoor intermediate cooler become very wet, which may be undesirable.

  The present invention has been made in view of the above points, and an object of the present invention is to perform multi-stage compression, function as an evaporator in the first operation state, and function as a high-pressure refrigerant cooler in the second operation state. Functions as a heat source side first heat exchanger, and an evaporator provided in parallel with the heat source side first heat exchanger in the first operation state, and functions as a refrigerant cooler for intermediate pressure in the second operation state. In the refrigeration apparatus including the heat source side second heat exchanger, in the first operation state, the evaporation capacity is secured in at least one of the heat source side first heat exchanger and the heat source side second heat exchanger in the first operation state. An object of the present invention is to provide a refrigeration apparatus capable of adjusting the degree of superheat of the combined refrigerant of the refrigerant flowing out of the heat source side first heat exchanger and the refrigerant flowing out of the heat source side second heat exchanger.

  The refrigeration apparatus according to the first aspect includes a low-stage compression section, a high-stage compression section that further compresses the refrigerant compressed by the low-stage compression section, a heat source-side first heat exchanger, and a heat source side A second heat exchanger, a use side heat exchanger, a first expansion mechanism, a second expansion mechanism, an operation state switching unit, and a control unit are provided. The operation state switching unit switches between the first operation state and the second operation state. In the first operating state, the use-side heat exchanger functions as a refrigerant cooler, the heat source-side first heat exchanger functions as a refrigerant evaporator, and the heat source-side second heat exchanger is 1 function as an evaporator of refrigerant connected in parallel with the heat exchanger, reduce the refrigerant from the use side heat exchanger to the heat source side second heat exchanger by the first expansion mechanism, and use the heat source from the use side heat exchanger The refrigerant going to the first heat exchanger is depressurized by the second expansion mechanism. In the second operation state, the heat source side second heat exchanger is caused to function as a refrigerant cooler that is discharged from the low stage side compression unit and then goes to the high stage side compression unit, and the heat source side first heat exchanger is configured to be on the high stage side. The refrigerant functioning as a cooler for the refrigerant discharged from the compression unit, the refrigerant flowing from the heat source side first heat exchanger to the use side heat exchanger is decompressed by the second expansion mechanism, and the use side heat exchanger is used as a refrigerant evaporator. Make it work. In the state where the operation state switching unit is switched to the first operation state, the control unit is either the refrigerant flowing through the outlet of the heat source side first heat exchanger or the refrigerant flowing through the outlet of the heat source side second heat exchanger. The degree of decompression in the first expansion mechanism and the second expansion mechanism is such that the superheat degree is smaller or moist compared to the superheat degree state while the other is in a superheated state. Adjust.

  In this refrigeration apparatus, the refrigerant flowing through the outlet in at least one of the heat source side first heat exchanger and the heat source side second heat exchanger in a state where the operation state switching unit is switched to the first operation state. By controlling the degree of superheat to be small or moist, it is possible to ensure the evaporation capability. Further, the superheat degree of the refrigerant flowing through the outlet in at least one of the heat source side first heat exchanger and the heat source side second heat exchanger in a state where the operation state switching unit is switched to the first operation state. By controlling to be larger than the one side, it is possible to adjust the degree of superheat of the combined refrigerant of the refrigerant flowing out of the heat source side first heat exchanger and the refrigerant flowing out of the heat source side second heat exchanger. It becomes possible.

  As described above, it is possible to adjust the superheat degree of the refrigerant after merging while ensuring the evaporation capability in at least one of the heat source side first heat exchanger and the heat source side second heat exchanger.

  The refrigeration apparatus according to the second aspect is the refrigeration apparatus according to the first aspect, and the control unit is configured to provide an outlet of the heat source side second heat exchanger when the operation state switching unit is switched to the first operation state. So that the refrigerant flowing through the outlet of the first heat exchanger on the heat source side is in a state where the degree of superheat is smaller or moist compared to the state where the refrigerant flowing in the outlet of the heat source side first heat exchanger is in a state of being superheated. In addition, the degree of pressure reduction in the first expansion mechanism and the second expansion mechanism is adjusted.

  For example, in the first operation state, when the heat source side first heat exchanger and the heat source side second heat exchanger are connected in parallel and function as an evaporator of the refrigerant, the outlet of the heat source side first heat exchanger is temporarily assumed. If the refrigerant flowing through the refrigerant and the refrigerant flowing through the outlet of the heat source side second heat exchanger are controlled so as to generate the same degree of superheat, the evaporation capability of the heat source side first heat exchanger may be reduced. There is.

  On the other hand, in this refrigeration apparatus, in the first operating state, the refrigerant is controlled so that the degree of superheat of the refrigerant flowing through the outlet of the heat source side first heat exchanger is small or wet. For this reason, it becomes possible to suppress the reduction of the evaporation capability in the heat source side first heat exchanger.

  The refrigeration apparatus according to the third aspect is the refrigeration apparatus according to the second aspect, and further includes a heat source side first blower that supplies air to the heat source side first heat exchanger. The heat source side first heat exchanger has refrigerant flow paths on the upstream side and the downstream side in the flow direction of the air supplied by the heat source side first blower. The refrigerant outlet vicinity part of the heat source side first heat exchanger in the first operation state is located on the downstream side in the air flow direction. The portion near the refrigerant outlet of the heat source side first heat exchanger in the second operation state is located on the upstream side in the air flow direction.

  In this refrigeration apparatus, in the second operation state, the temperature vicinity of the heat exchange in the vicinity of the refrigerant outlet is easily secured by positioning the vicinity of the refrigerant outlet of the heat source side first heat exchanger on the upstream side of the air flow. The heat exchange efficiency can be improved.

  Here, in the first operating state, the portion near the refrigerant outlet of the heat source side first heat exchanger is located on the downstream side of the air flow, and it becomes difficult to secure a temperature difference in heat exchange. There is a risk that the evaporation capacity will be reduced.

  On the other hand, in this refrigeration apparatus, in the first operating state, the refrigerant is controlled so that the degree of superheat of the refrigerant flowing through the outlet of the heat source side first heat exchanger is small or wet. For this reason, even in a situation where it is difficult to ensure a temperature difference in the first operating state, it is possible to suppress a reduction in evaporation capacity in the heat source side first heat exchanger.

  The refrigeration apparatus according to the fourth aspect is the refrigeration apparatus according to the third aspect, wherein the heat source side first heat exchanger has fins and a flat multi-hole tube having a plurality of passages arranged in the horizontal direction. And made of aluminum or an aluminum alloy.

  In this arrangement of the refrigeration apparatus, in the first operating state, the refrigerant outlet vicinity portion of the heat source side first heat exchanger is located on the downstream side of the air flow, and it is difficult to ensure a temperature difference in heat exchange. Become. And when the heat source side 1st heat exchanger has a flat multi-hole tube and a fin and is comprised with aluminum or aluminum alloy, since the heat exchange efficiency of air and a refrigerant | coolant is high, 1st heat source side heat The heat exchange temperature difference in the vicinity of the refrigerant outlet of the exchanger becomes more difficult to secure, and the heat exchange efficiency may be reduced.

  On the other hand, in this refrigeration apparatus, in the first operating state, the refrigerant is controlled so that the degree of superheat of the refrigerant flowing through the outlet of the heat source side first heat exchanger is small or wet. For this reason, even if it is a situation where it is much more difficult to ensure the temperature difference, it is possible to suppress a reduction in evaporation capacity in the heat source side first heat exchanger.

  A refrigeration apparatus according to a fifth aspect is the refrigeration apparatus according to any one of the second to fourth aspects, and includes a heat source side second air blowing unit that supplies air to the heat source side second heat exchanger. Yes. The heat source side second heat exchanger has refrigerant flow paths on the upstream side and the downstream side in the flow direction of the air supplied by the heat source side second blower. Regardless of whether the operation state switching unit is switched to the first operation state or the second operation state, at least a part of the vicinity of the refrigerant outlet of the heat source side second heat exchanger is upstream in the air flow direction. It is comprised so that it may be located in.

  Note that the heat source side second air blowing unit may be the same air blowing unit as the heat source side first air blowing unit of the refrigeration apparatus according to the third aspect, or may be a different air blowing unit.

  In this arrangement of the refrigeration apparatus, in the first operating state, the heat source side second heat exchanger is functioned as a refrigerant evaporator, and control is performed so that the refrigerant flowing through the outlet has a superheat degree. ing. For this reason, in the first operation state, the heat source side second heat exchanger has a portion where the flowing refrigerant has a degree of superheat and is not evaporated, which may reduce the heat exchange efficiency.

  On the other hand, in this refrigeration apparatus, in the first operating state, at least a part of the refrigerant outlet vicinity portion of the heat source side second heat exchanger is located on the upstream side in the air flow direction, thereby reducing the heat exchange efficiency. It can be suppressed. Further, even in the second operating state, at least a part of the refrigerant outlet vicinity portion of the heat source side second heat exchanger is located on the upstream side in the air flow direction, so that reduction in heat exchange efficiency can be suppressed. .

  A refrigeration apparatus according to a sixth aspect is the refrigeration apparatus according to any of the second to fifth aspects, further comprising an intermediate compression unit and a heat source side third heat exchanger. The intermediate compression unit further compresses the refrigerant compressed by the low-stage compression unit and sends it to the high-stage compression unit. In the first operation state, the operation state switching unit causes the use side heat exchanger to function as a refrigerant cooler, causes the heat source side first heat exchanger to function as a refrigerant evaporator, and the heat source side second heat exchanger and While making the heat source side third heat exchanger a series heat exchange unit connected in series, the series heat exchange unit functions as a refrigerant evaporator connected in parallel with the heat source side first heat exchanger in the refrigerant flow, The refrigerant heading from the use side heat exchanger to the series heat exchanging section is depressurized by the first expansion mechanism, and the refrigerant heading from the use side heat exchanger to the heat source side first heat exchanger is depressurized by the second expansion mechanism. In the second operation state, the operation state switching unit causes the heat source side second heat exchanger to function as a refrigerant cooler that is discharged from the low-stage compression unit and then travels to the intermediate compression unit, and the heat source side third heat exchanger To function as a refrigerant cooler that is discharged from the intermediate compression section and then toward the high-stage compression section, and to function as a cooler for the refrigerant discharged from the high-stage compression section. The refrigerant from the side first heat exchanger toward the use side heat exchanger is decompressed by the second expansion mechanism, and the use side heat exchanger is caused to function as a refrigerant evaporator.

  In this refrigeration apparatus, in the first operating state, the heat source side second heat exchanger and the heat source side third heat exchanger are connected in series and function as an evaporator, so that the flow path for evaporating the refrigerant is lengthened. Therefore, the refrigerant that has passed through the heat source side second heat exchanger and the heat source side third heat exchanger is likely to be superheated. For this reason, even if it is a case where it is controlled so that the degree of superheat of the refrigerant flowing through the outlet of the heat source side first heat exchanger is small or wet in the first operating state, the heat source side second heat Passing through the heat source side first heat exchanger, the heat source side second heat exchanger, and the heat source side third heat exchanger by facilitating overheating in the refrigerant that has passed through the exchanger and the heat source side third heat exchanger It becomes easy to adjust the superheat degree of the combined refrigerant.

  A refrigeration apparatus according to a seventh aspect is the refrigeration apparatus according to any one of the first to sixth aspects, wherein the third expansion mechanism, the refrigerant container, the liquid gas heat exchanger, the bypass circuit, and the bypass expansion. And a mechanism. The third expansion mechanism is provided between the heat source side first heat exchanger and the use side heat exchanger, and depressurizes the refrigerant passing therethrough. The refrigerant container is a container for separating the refrigerant decompressed in the third expansion mechanism into a gas phase and a liquid phase. The liquid gas heat exchanger is a refrigerant that has flowed out of the heat exchanger functioning as a refrigerant cooler among the use side heat exchanger and the heat source side first heat exchanger, and is a refrigerant container through a third expansion mechanism. And a refrigerant that has flowed out of the heat exchanger functioning as an evaporator of the refrigerant among the use side heat exchanger and the heat source side first heat exchanger, and that is directed to the low-stage compression unit, Heat exchange between them. The bypass circuit is a circuit for joining the refrigerant including at least the refrigerant extracted from the gas phase portion of the refrigerant container to the refrigerant flowing out of the heat exchanger functioning as an evaporator and going toward the liquid gas heat exchanger. It is. The bypass expansion mechanism depressurizes the refrigerant from the refrigerant container toward the liquid gas heat exchanger.

  In this refrigeration apparatus, the refrigerant sucked into the low-stage compression section after passing through the heat exchanger functioning as a refrigerant evaporator can be increased in superheat degree by heat exchange in the liquid gas heat exchanger. . Further, the refrigerant flowing out of the heat exchanger functioning as a refrigerant cooler can be further cooled in the liquid gas heat exchanger.

  A refrigeration apparatus according to an eighth aspect is the refrigeration apparatus according to the seventh aspect, wherein the control unit is an evaporator of the liquid gas heat exchanger in a state where the operation state switching unit is switched to the first operation state. Is controlled by adjusting the degree of decompression in the first expansion mechanism, the second expansion mechanism, and the bypass expansion mechanism.

  In this refrigeration apparatus, since the superheat degree of the portion into which the refrigerant flowing out of the heat exchanger functioning as an evaporator of the liquid gas heat exchanger flows can be controlled, the refrigerant container is provided via the third expansion mechanism. It is possible to prevent the refrigerant sent to the refrigerant from being too cold. Thereby, it becomes possible to send the gas-liquid two-phase refrigerant to the refrigerant container, and it becomes possible to more reliably separate the gas-phase refrigerant and the liquid-phase refrigerant in the refrigerant container. Therefore, the amount of surplus refrigerant can be controlled, so that the operation of the refrigeration cycle can be stabilized.

  A refrigeration apparatus according to a ninth aspect is the refrigeration apparatus according to the eighth aspect, wherein the control unit is configured to provide an outlet of the heat source side first heat exchanger in a state where the operation state switching unit is switched to the first operation state. By reducing the amount of refrigerant passing through the first expansion mechanism so that the refrigerant satisfies a predetermined condition, the refrigerant flowing out of the heat exchanger functioning as an evaporator of the liquid gas heat exchanger flows in. Increase the degree of superheat of the refrigerant.

  In this refrigeration apparatus, the refrigerant flowing out of the heat exchanger functioning as an evaporator of the liquid gas heat exchanger while the state of the refrigerant flowing through the outlet of the first heat exchanger on the heat source side satisfies a predetermined condition. It is possible to increase the degree of superheat of the refrigerant in the portion where the refrigerant flows.

  In the refrigeration apparatus according to the first aspect, the superheat degree of the refrigerant after merging is adjusted while ensuring the evaporation capability in at least one of the heat source side first heat exchanger and the heat source side second heat exchanger. Is possible.

  In the refrigeration apparatus according to the second aspect, it is possible to suppress a reduction in evaporation capacity in the heat source side first heat exchanger.

  In the refrigeration apparatus according to the third aspect, even in a situation where it is difficult to ensure a temperature difference in the first operating state, it is possible to suppress a reduction in evaporation capacity in the heat source side first heat exchanger.

  In the refrigeration apparatus according to the fourth aspect, it is possible to suppress a reduction in evaporation capability in the heat source side first heat exchanger even in a situation where it is more difficult to ensure a temperature difference.

  In the refrigeration apparatus according to the fifth aspect, reduction in heat exchange efficiency of the heat source side second heat exchanger can be suppressed in both the first operation state and the second operation state.

  In the refrigeration apparatus according to the sixth aspect, even in the second operation state, even when the superheat degree of the refrigerant flowing through the outlet of the heat source side first heat exchanger is controlled to be small or wet. It becomes easy to adjust the superheat degree of the combined refrigerant of the refrigerant that has passed through the heat source side first heat exchanger, the heat source side second heat exchanger, and the heat source side third heat exchanger.

  In the refrigeration apparatus according to the seventh aspect, the heat exchanger functioning as a refrigerant cooler while increasing the degree of superheat of the refrigerant sucked into the low-stage compression section after passing through the heat exchanger functioning as the refrigerant evaporator. Further cooling of the refrigerant that has flowed out of the tank becomes possible.

  In the refrigeration apparatus according to the eighth aspect, it is possible to stabilize the operation of the refrigeration cycle by controlling the amount of excess refrigerant by more reliably separating the gas-phase refrigerant and the liquid-phase refrigerant in the refrigerant container. .

  In the refrigeration apparatus according to the ninth aspect, the heat exchanger functioning as an evaporator of the liquid gas heat exchanger while the state of the refrigerant flowing through the outlet of the heat source side first heat exchanger satisfies a predetermined condition. It is possible to increase the degree of superheat of the refrigerant in the portion into which the refrigerant that has flowed out flows.

It is a schematic block diagram of the air conditioning apparatus which concerns on one Embodiment of this invention. It is a schematic perspective view of an outdoor unit and its inside. It is the schematic which shows the internal structure of an outdoor heat exchanger. It is a top view schematic block diagram of a 4th outdoor heat exchanger. It is a top view schematic block diagram of a 1st-3rd outdoor heat exchanger. It is a partial expansion schematic structure perspective view of an outdoor heat exchanger. It is a schematic block diagram at the time of air_conditionaing | cooling operation of an air conditioning apparatus. FIG. 8 is a pressure-enthalpy diagram of the refrigeration cycle during the cooling operation of FIG. 7. It is a schematic block diagram at the time of the heating operation of an air conditioning apparatus. FIG. 10 is a pressure-enthalpy diagram of the refrigeration cycle during the heating operation of FIG. 9.

  An air conditioner 1 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 FIG. 1, FIG. 7 and FIG. 9 are schematic configuration diagrams of the air conditioner 1. Among these, FIG. 7 represents the flow of the refrigerant circulating through the refrigerant circuit during the cooling operation, and FIG. 9 represents the flow of the refrigerant circulating through the refrigerant circuit during the heating operation.

  The air conditioner 1 is a refrigeration apparatus that performs a four-stage compression refrigeration cycle using a carbon dioxide refrigerant in a supercritical state. The air conditioner 1 includes an outdoor unit 11 that is a heat source unit, and a plurality of indoor units 12 and 13 that are utilization units (including the first indoor unit 12 and the second indoor unit 13), a liquid refrigerant communication pipe 14 and The apparatus is connected by the gas refrigerant communication pipe 15 and has a refrigerant circuit that switches between a cooling operation cycle and a heating operation cycle.

  The refrigerant circuit of the air conditioner 1 mainly includes a four-stage compressor 20, a four-way switching valve group 25 (first to fourth four-way switching valves 26 to 29), an outdoor heat exchanger 40, and a first outdoor expansion valve 47. , Second outdoor expansion valve 48, bridge circuit 49, economizer circuit 50, liquid gas heat exchange circuit 60, expansion mechanism 70, separation gas pipe 80, receiver 81, supercooling circuit 90, first indoor heat exchanger 12a, second The indoor heat exchanger 13a, the first indoor expansion valve 12b, the second indoor expansion valve 13b, and the control unit 7 are provided. The outdoor heat exchanger 40 includes a first outdoor heat exchanger 41, a second outdoor heat exchanger 42, a third outdoor heat exchanger 43, and a fourth outdoor heat exchanger 44.

  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 first suction pipe 21a is provided with a suction pressure sensor 21p for detecting the suction pressure of the flowing refrigerant. The second compressor 22 sucks the refrigerant from the second suction pipe 22a and discharges the refrigerant to the second discharge pipe 22b. The second suction pipe 22a is provided with a check structure that allows only the refrigerant flow from the first four-way switching valve 26 toward the suction side of the second compression section 22. The third compressor 23 sucks the refrigerant from the third suction pipe 23a and discharges the refrigerant to the third discharge pipe 23b. The third suction pipe 23 a is provided with a check structure that allows only the refrigerant flow from the second four-way switching valve 27 toward the suction side of the third compression portion 23. The fourth compressor 24 sucks the refrigerant from the fourth suction pipe 24a and discharges the refrigerant to the fourth discharge pipe 24b. The fourth suction pipe 24 a is provided with a check structure that allows only the refrigerant flow from the third four-way switching valve 28 toward the suction side of the fourth compression section 24. The fourth discharge pipe 24b is provided with a discharge pressure sensor 24p that detects the discharge pressure of the flowing refrigerant.

  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 7.

(1-2) Four-way switching valve group The four-way switching valve group 25 includes a first four-way switching valve 26, a second four-way switching valve 27, a third four-way switching valve 28, and a fourth four-way switching valve 29. It is configured. The four-way switching valve group 25 is provided for switching between the cooling operation cycle and the heating operation cycle by switching the direction of the refrigerant flow in the refrigerant circuit.

  The four ports of the first four-way switching valve 26 are connected to the first discharge pipe 21b, the second suction pipe 22a, the first pipe 41a, and the four-way connection pipe 30. The first pipe 41 a is a pipe connecting the first four-way switching valve 26 and the first outdoor heat exchanger 41. The first pipe 41a is provided with a third temperature sensor 41t for detecting the temperature of the refrigerant passing therethrough.

  The four-way connection pipe 30 is a pipe that guides the low-pressure refrigerant to the low-pressure refrigerant pipe 19 during the heating operation. 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 liquid gas heat exchanger 61.

  The second four-way switching valve 27 is connected to the second discharge pipe 22b, the third suction pipe 23a, the second pipe 42a, and the first intercooler pipe 41c. The second pipe 42 a is a pipe connecting the second four-way switching valve 27 and the second outdoor heat exchanger 42. The first intercooler pipe 41c is a pipe connected so as to communicate with the second suction pipe 22a while communicating with the third suction pipe 23a in the connected state during the cooling operation, and is one end of a fifth pipe 41b described later. Is connected on the way.

  The third four-way switching valve 28 is connected to the third discharge pipe 23b, the fourth suction pipe 24a, the third pipe 43a, and the second intercooler pipe 42c. The third pipe 43 a is a pipe connecting the third four-way switching valve 28 and the third outdoor heat exchanger 43. The second intercooler pipe 42c is a pipe connected so as to communicate with the third suction pipe 23a while communicating with the fourth suction pipe 24a in the connected state during the cooling operation, and is one end of a sixth pipe 42b described later. Is connected on the way.

  The fourth four-way switching valve 29 is connected to the fourth discharge pipe 24 b, the gas refrigerant communication pipe 15, the fourth pipe 44 a, and the low pressure refrigerant pipe 19. The fourth pipe 44 a is a pipe connecting the fourth four-way switching valve 29 and the fourth outdoor heat exchanger 44. The fourth pipe 44a is provided with a second temperature sensor 44t2 for detecting the temperature of the refrigerant passing therethrough.

  The four-way switching valve group 25 is controlled by the control unit 7 so that, during cooling operation, as shown in FIG. 7, a heat radiator (refrigerant of refrigerant) that radiates heat of the refrigerant compressed by the four-stage compressor 20. The outdoor heat exchanger 40 (first to fourth outdoor heat exchangers 41 to 44) functions as a cooler and passes through the expansion mechanism 70, the first indoor expansion valve 12b, and the second indoor expansion valve 13b. The first indoor heat exchanger 12a and the second indoor heat exchanger 13a function as the expanded refrigerant evaporator (refrigerant heater). Here, at the time of air_conditionaing | cooling operation, the 1st-4th outdoor heat exchangers 41-44 will be in the state mutually connected in series with respect to the refrigerant | coolant flow direction.

  Further, the four-way switching valve group 25 is controlled by the control unit 7 so that, during heating operation, as shown in FIG. 9, a radiator (for releasing heat of the refrigerant compressed by the four-stage compressor 20). The first indoor heat exchanger 12a and the second indoor heat exchanger 13a function as a refrigerant cooler, and have expanded through the expansion mechanism 70, the first outdoor expansion valve 47, and the second outdoor expansion valve 48. It will be in the switching state which functions the outdoor heat exchanger 40 (1st-4th outdoor heat exchanger 41-44) as a refrigerant | coolant evaporator (refrigerant | coolant of a refrigerant | coolant). Here, at the time of heating operation, the 1st-3rd outdoor heat exchangers 41-43 and the 4th outdoor heat exchanger 44 will be in the state mutually connected in parallel with respect to the refrigerant | coolant flow direction. The 3rd outdoor heat exchangers 41-43 will be in the state mutually connected in series in the refrigerant | coolant flow direction.

  That is, the four-way switching valve group 25 focuses only on the four-stage compressor 20, the outdoor heat exchanger 40, the expansion mechanism 70, the first indoor heat exchanger 12a, and the second indoor heat exchanger 13a as components of the refrigerant circuit. Then, a cooling operation cycle in which the refrigerant is circulated in the order of the four-stage compressor 20, the outdoor heat exchanger 40, the expansion mechanism 70, the first indoor heat exchanger 12a, and the second indoor heat exchanger 13a, and the four-stage compressor 20, It plays the role which switches the heating operation cycle which circulates a refrigerant | coolant in order of the 1st indoor heat exchanger 12a, the 2nd indoor heat exchanger 13a, the expansion mechanism 70, and the outdoor heat exchanger 40.

(1-3) Oil Return Circuit Configuration First to third oil separators 31a, 32a, and 33a are provided in the middle of the first pipe 41a, the second pipe 42a, and the third pipe 43a, respectively. The first to third oil separators 31a, 32a and 33a are small containers for separating the lubricating oil contained in the refrigerant circulating in the refrigerant circuit. First to third oil return pipes 31b, 32b, and 33b including first to third capillary tubes 31c, 32c, and 33c extend from lower portions of the first to third oil separators 31a, 32a, and 33a, respectively. . Here, the first oil return pipe 31b is connected to return the refrigerating machine oil to the second suction pipe 22a. The first oil return pipe 31b allows the flow of refrigeration oil flowing between the first oil separator 31a and the first four-way switching valve 26 and the flow of refrigeration oil toward the second suction pipe 22a. Thus, a check structure is provided. The second oil return pipe 32b is connected to return the refrigeration oil in the middle of the third suction pipe 23a. The second oil return pipe 32b allows the flow of refrigeration oil flowing between the second oil separator 32a and the second four-way switching valve 27 and the flow of refrigeration oil toward the third suction pipe 23a. Thus, a check structure is provided. The third oil return pipe 33b is connected to return the refrigeration oil in the middle of the fourth suction pipe 24a. The third oil return pipe 33b allows the flow of refrigeration oil flowing between the third oil separator 33a and the third four-way switching valve 28 and the flow of refrigeration oil toward the fourth suction pipe 24a. Thus, a check structure is provided.

  A fourth oil separator 34a is provided in the middle of the fourth discharge pipe 24b. The fourth oil separator 34a is a small container that separates lubricating oil contained in the refrigerant circulating in the refrigerant circuit. A fourth oil return pipe 34b including a fourth capillary tube 34c extends from the lower part of the fourth oil separator 34a. The fourth oil return pipe 34b is connected in the middle of the first suction pipe 21a.

  Thereby, the lubricating oil separated from the refrigerant in each of the first to fourth oil separators 31a, 32a, 33a, 34a is returned to the four-stage compressor 20.

(1-4) Outdoor heat exchanger and intercooler tube As described above, the outdoor heat exchanger 40 includes the first outdoor heat exchanger 41, the second outdoor heat exchanger 42, the third outdoor heat exchanger 43, and the first outdoor heat exchanger 43. It is composed of four outdoor heat exchangers 44. During the cooling operation, the first to third outdoor heat exchangers 41 to 43 function as an intercooler that cools the refrigerant (intermediate pressure refrigerant) being compressed, and the fourth outdoor heat exchanger 44 cools the highest pressure refrigerant. It functions as a gas cooler (a radiator that dissipates the heat of the refrigerant). The fourth outdoor heat exchanger 44 has a larger capacity than the first to third outdoor heat exchangers 41 to 43. Further, during the heating operation, all of the first to fourth outdoor heat exchangers 41 to 44 function as low-pressure refrigerant evaporators (heaters).

  As shown in FIGS. 2, 4, and 5, the outdoor heat exchanger 40 is provided in the casing of the outdoor unit 11 such that a U-shape extends upward. The housing of the outdoor unit 11 has a substantially rectangular parallelepiped shape that is long in the vertical direction, and one of the four side surfaces is completely covered, and the other three side surfaces are provided with ventilation openings. The outdoor heat exchanger 40 is provided at a position facing the ventilation opening of the outdoor unit 11 and is configured along the three side surfaces of the casing. 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, air (outside air) is supplied to the outdoor heat exchanger 40 from the outdoor blower fan 45. The outdoor blower fan 45 takes in air in the lateral direction of the casing of the outdoor unit 11 and generates an air flow that discharges the air after heat exchange through an opening provided above the casing.

  As shown in FIG. 3, the first to fourth outdoor heat exchangers 41 to 44 are arranged so as to be stacked in the vertical direction, and are integrated as one outdoor heat exchanger 40. The first to fourth outdoor heat exchangers 41 to 44 are, in order from the bottom, the first outdoor heat exchanger 41, the second outdoor heat exchanger 42, the third outdoor heat exchanger 43, and the fourth outdoor heat exchanger 44. Are arranged in this order. Although not particularly limited, in the present embodiment, the capacity ratio is such that the fourth outdoor heat exchanger 44: the third outdoor heat exchanger 43: the second outdoor heat exchanger 42: the first outdoor heat exchanger. 41 is configured to be 4: 2: 1: 1.

  Among the first to fourth outdoor heat exchangers 41 to 44, the fourth outdoor heat exchanger 44 has a plurality of rows (two rows in this embodiment) in the air flow direction as shown in the top view of FIG. Heat transfer tubes 44g and 44h are provided, and a U-shaped tube 44i is provided on one end side so that the heat transfer tubes 44g and 44h in each row at the same height are connected in series. Here, the outer heat transfer tube 44 g is disposed outside the casing of the outdoor unit 11, and the inner heat transfer tube 44 h is disposed inside the casing of the outdoor unit 11. The fourth outdoor heat exchanger 44 includes a plurality of rows of heat transfer tubes 44g and 44h arranged in the vertical direction. Refrigerant that has been diverted through a header (not shown) is supplied to the heat transfer tubes 44g and 44h of each stage in the vertical direction. As shown in the schematic perspective view of FIG. 6, the heat transfer tubes 44g and 44h are both flat multi-hole tubes in which a plurality of micro flow channels 40x are arranged in the horizontal direction, and are made of aluminum or an aluminum alloy. Has been. Between the heat transfer tubes 44g and 44h of each stage, a radiation fin 40y made of aluminum or an aluminum alloy is provided.

  In the heating operation, the fourth outdoor heat exchanger 44 has a refrigerant inlet located upstream of the air flow (positioned on the outer heat transfer tube 44g) and a refrigerant outlet as shown by an arrow in FIG. It connects so that it may be located in the downstream of an air flow (it is located in the inner side heat exchanger tube 44h). Further, the fourth outdoor heat exchanger 44 is opposite to the heating operation in the cooling operation, and the refrigerant inlet is located downstream of the air flow (located in the inner heat transfer tube 44h). The outlet is located on the upstream side of the air flow (located on the outer heat transfer tube 44g).

  Among the first to fourth outdoor heat exchangers 41 to 44, the first to third outdoor heat exchangers 41 to 43 have a plurality of rows (two rows in this embodiment) in the air flow direction, as shown in FIG. Heat transfer tubes 41g, 41h, 42g, 42h, 43g, 43h are provided, and Y at both ends so that the heat transfer tubes 41g, 41h, 42g, 42h, 43g, 43h in each row are connected in parallel to each other. The character tubes 41k, 42k, 43k, 41j, 42j, and 43j are provided. Here, the outer heat transfer tubes 41 g, 42 g, 43 g are arranged outside the casing of the outdoor unit 11, and the inner heat transfer tubes 41 h, 42 h, 43 h are arranged inside the casing of the outdoor unit 11. The first to third outdoor heat exchangers 41 to 43 are configured by arranging a plurality of rows of heat transfer tubes 41g, 41h, 42g, 42h, 43g, and 43h in the vertical direction. The refrigerant divided through a header (not shown) is supplied to the heat transfer tubes 41g, 41h, 42g, 42h, 43g, and 43h of each stage in the vertical direction. The heat transfer tubes 41g, 41h, 42g, 42h, 43g, and 43h are flat multi-hole tubes each having a plurality of micro flow channels 40x arranged in the horizontal direction as shown in the schematic perspective view of FIG. Yes, it is made of aluminum or aluminum alloy. Between the heat transfer tubes 41g, 41h, 42g, 42h, 43g, and 43h of each stage, a heat radiation fin 40y made of aluminum or an aluminum alloy is provided.

  As shown in FIG. 5, the first to third outdoor heat exchangers 41 to 43 are Y-tubes 41k, 42k, 43k, 41j, 42j, and 43j at the refrigerant inlet as shown in FIG. Thus, the refrigerant is divided into the upstream side of the air flow (outside heat transfer tubes 41g, 42g, 43g side) and the downstream side of the air flow (inside heat transfer tubes 41h, 42h, 43h), and the refrigerant flows in parallel.

  Here, the 5th piping 41b is connected to the 1st outdoor heat exchanger 41 on the opposite side to the 1st piping 41a. The end of the fifth pipe 41b opposite to the first outdoor heat exchanger 41 side is connected to the middle of the first intercooler pipe 41c. In other words, in the connection state during the cooling operation, one end of the fifth pipe 41b is connected to the middle of the first intercooler pipe 41c which is connected to the third suction pipe 23a while being connected to the second suction pipe 22a. ing. The first intercooler pipe 41c is a check that allows only the refrigerant flow toward the second suction pipe 22a between the connection section with the fifth pipe 41b and the connection section with the second suction pipe 22a. A structure is provided.

  A sixth pipe 42b is connected to the second outdoor heat exchanger 42 on the side opposite to the second pipe 42a. The end of the sixth pipe 42b opposite to the second outdoor heat exchanger 42 side is connected to the middle of the second intercooler pipe 42c. That is, in the connection state during the cooling operation, one end of the sixth pipe 42b is connected to the middle of the second intercooler pipe 42c that is connected to the fourth suction pipe 24a while being connected to the third suction pipe 23a. ing. The second intercooler pipe 42c is a check that allows only the refrigerant flow toward the third suction pipe 23a between the connection portion with the sixth pipe 42b and the connection portion with the third suction pipe 23a. A structure is provided.

  A seventh pipe 43b is connected to the side of the third outdoor heat exchanger 43 opposite to the third pipe 43a. The end of the seventh pipe 43b opposite to the third outdoor heat exchanger 43 side is connected to the third intercooler pipe 43c and the common pipe 47a. The third intercooler pipe 43c is connected to the fourth suction pipe 24a at the end opposite to the connection portion with the seventh pipe 43b. The third intercooler pipe 43c is provided with a check structure that allows only the refrigerant flow toward the fourth suction pipe 24a. The common pipe 47a is connected in the middle of a later-described supercooled refrigerant pipe 84. A first outdoor expansion valve 47 is provided in the middle of the common pipe 47a.

  An eighth pipe 44b is connected to the opposite side of the fourth outdoor heat exchanger 44 from the fourth pipe 44a. The eighth pipe 44b is connected between the second outdoor expansion valve 48 and the third check valve 49c in the bridge circuit 49 described later. The eighth pipe 44b is provided with a first temperature sensor 44t1 for detecting the temperature of the refrigerant passing therethrough.

(1-5) First outdoor expansion valve and second outdoor expansion valve As described above, the first outdoor expansion valve 47 includes the end of the seventh pipe 43b extending from the third outdoor heat exchanger 43 and the supercooling refrigerant. It is provided in the middle of the common pipe 47 a connecting the middle of the pipe 84. The common pipe 47a is connected between the second outdoor expansion valve 48 and the first check valve 49a of the bridge circuit 49 via the supercooled refrigerant pipe 84.

  The second outdoor expansion valve 48 is provided so that the refrigerant that flows to the eighth pipe 44 b after flowing through the supercooled refrigerant pipe 84 during the heating operation can be decompressed in the bridge circuit 49.

  During the cooling operation, the first outdoor expansion valve 47 and the second outdoor expansion valve 48 are closed under the control of the control unit 7. During the heating operation, the control of the control unit 7 causes the first outdoor expansion valve 47 and the second outdoor expansion valve 48 to drift in the refrigerant flow from the bridge circuit 49 to the first to fourth outdoor heat exchangers 41 to 44. The degree of opening is adjusted so that it does not act as an expansion mechanism.

(1-6) Bridge Circuit The bridge circuit 49 includes a first check valve 49a, a second check valve 49b, a third check valve 49c, and a second outdoor expansion valve 48, which are connected in order. A circuit is formed in which the valve 49a and the second outdoor expansion valve 48 are connected. The first check valve 49a allows only the refrigerant flow toward the side opposite to the second outdoor expansion valve 48 side. The third check valve 49c allows only the refrigerant flow toward the side opposite to the second outdoor expansion valve 48 side. The second check valve 49b does not allow the refrigerant flow toward the first check valve 49a, but allows only the refrigerant flow toward the third check valve 49c.

  Between the first check valve 49a and the second outdoor expansion valve 48 of the bridge circuit 49, a pipe in which the common pipe 47a and the supercooling refrigerant pipe 84 are joined is connected. An eighth pipe 44 b extending from the fourth outdoor heat exchanger 44 is connected between the third check valve 49 c and the second outdoor expansion valve 48 of the bridge circuit 49. Between the first check valve 49 a and the second check valve 49 b of the bridge circuit 49, the liquid refrigerant communication pipe 14 extending from the first indoor unit 12 and the second indoor unit 13 is connected. A refrigerant pipe extending toward the economizer heat exchanger 51 side of the economizer circuit 50 is connected between the second check valve 49b and the third check valve 49c of the bridge circuit 49.

(1-7) Economizer Circuit The economizer circuit 50 is provided between the portion of the bridge circuit 49 between the second check valve 49b and the third check valve 49c, and the liquid gas heat exchanger 61 or the expansion mechanism 70. Is provided. The economizer circuit 50 includes an economizer heat exchanger 51, an economizer injection pipe 53, and an economizer expansion valve 52.

  The economizer injection pipe 53 branches and extends from a portion between the second check valve 49b and the third check valve 49c of the bridge circuit 49 and a portion in front of the economizer heat exchanger 51, The second intercooler pipe 42c is connected to the downstream side of the second intercooler check valve.

  The economizer expansion valve 52 is provided in the middle of the economizer injection pipe 53 and before flowing into the economizer heat exchanger 51 after branching.

  The economizer heat exchanger 51 is branched to the economizer injection valve 53 and expanded at the economizer expansion valve 52 by the high-pressure refrigerant exceeding the critical pressure from the bridge circuit 49 toward the liquid gas heat exchanger 61 or the expansion mechanism 70. Heat exchange is performed with the refrigerant having the pressure.

  The refrigerant expanded in the economizer expansion valve 52 and evaporated in the economizer heat exchanger 51 is merged with the refrigerant flowing through the second intercooler pipe 42c, whereby the refrigerant sucked into the third compressor 23 from the third suction pipe 23a. Cool down.

(1-8) Liquid-gas heat exchange circuit The liquid-gas heat exchange circuit 60 is provided between the economizer heat exchanger 51 and the expansion mechanism 70, and includes a liquid-gas heat exchanger 61.

  In the liquid gas heat exchanger 61, a high-pressure refrigerant that exceeds a critical pressure from the bridge circuit 49 toward the expansion mechanism 70, a low-pressure refrigerant that flows through the supercooling injection pipe 93, and a low-pressure refrigerant that flows through the low-pressure refrigerant pipe 19 are merged. Heat exchange is performed with the merged refrigerant that is the low-pressure refrigerant merged at 65. The liquid gas heat exchanger 61 may be referred to as an internal heat exchanger.

  In addition, the low-pressure refrigerant | coolant which flows through the supercooling injection piping 93, and the low-pressure refrigerant | coolant which flows through the low pressure refrigerant | coolant piping 19 join at the junction 65, and the confluence | merging which detects the refrigerant | coolant temperature of the merged refrigerant | coolant which is flowing toward the liquid gas heat exchanger 61 A refrigerant temperature sensor 64t is provided on the low-pressure refrigerant inlet side of the liquid gas heat exchanger 61.

(1-9) Expansion Mechanism The expansion mechanism 70 depressurizes and expands the high-pressure refrigerant flowing from the economizer heat exchanger 51 or the liquid gas heat exchanger 61, and receives the intermediate-pressure refrigerant in the gas-liquid two-phase state as a receiver 81. To flow. That is, during the cooling operation, the expansion mechanism 70 includes the first indoor heat exchanger 12a and the second indoor heat exchanger 12a that function as an evaporator for the low-pressure refrigerant from the outdoor fourth outdoor heat exchanger 44 that functions as a gas cooler (heat radiator) for the high-pressure refrigerant. The refrigerant sent toward the indoor heat exchanger 13a is decompressed. Further, during the heating operation, the expansion mechanism 70 is directed from the first indoor heat exchanger 12a functioning as a high-pressure refrigerant radiator and the outdoor heat exchanger 40 functioning as an evaporator of low-pressure refrigerant from the second indoor heat exchanger 13a. The refrigerant sent is depressurized.

  The expansion mechanism 70 is configured by connecting an expander 71 and a third outdoor expansion valve 72 in parallel. The expander 71 plays a role of recovering the throttle loss in the decompression process of the refrigerant as effective work (energy).

  An intermediate temperature sensor 70t is provided between the expansion mechanism 70 and the receiver 81 for the refrigerant temperature. Since the intermediate temperature sensor 70t detects the saturation temperature of the intermediate pressure, the control unit 7 can grasp the intermediate pressure that is the equivalent saturation pressure from the detected temperature of the intermediate temperature sensor 70t.

(1-10) Receiver The receiver 81 causes the gas-liquid two-phase intermediate pressure refrigerant that has exited the expansion mechanism 70 to flow into the internal space from the ceiling surface, and is separated into liquid refrigerant and gas refrigerant.

  The liquid refrigerant separated in the receiver 81 is sent to the supercooling circuit 90 via the liquid refrigerant outlet pipe 83 extending from below the receiver 81.

  The gas refrigerant separated by the receiver 81 and passing through the separation gas pipe 80 extending from the upper side of the receiver 81 merges with the refrigerant flowing through a supercooling injection pipe 93 of the supercooling circuit 90 described later. A separation gas expansion valve 82 is provided in the middle of the separation gas pipe 80. The refrigerant flowing through the separation gas pipe 80 is a gas refrigerant from which the liquid refrigerant has been separated in the receiver 81 and is reduced in pressure by the separation gas expansion valve 82 to become a low-pressure gas-rich refrigerant, and then the supercooling injection pipe 93. Sent to.

(1-11) Supercooling Circuit The supercooling circuit 90 is provided between the receiver 81 and a portion of the bridge circuit 49 between the first check valve 49a and the second outdoor expansion valve 48. The supercooling circuit 90 includes a supercooling heat exchanger 91, a supercooling injection pipe 93, and a supercooling expansion valve 92.

  The refrigerant that has flowed through the liquid refrigerant outlet pipe 83 extending from the receiver 81 is divided into a refrigerant that is directed to the supercooling heat exchanger 91 and a refrigerant that is divided and flows through the supercooling injection pipe 93. The supercooling injection pipe 93 branches off from the middle of the liquid refrigerant outlet pipe 83 and is connected to the low pressure refrigerant pipe 19 at the junction 65. A supercooling expansion valve 92 is provided in the middle of the supercooling injection pipe 93 and between the part branched from the liquid refrigerant outlet pipe 83 and the part to which the separation gas pipe 80 is connected.

  During the cooling operation, the control unit 7 controls the supercooling expansion valve 92 and the separation gas expansion valve 82, and the refrigerant is decompressed by the supercooling expansion valve 92 of the supercooling injection pipe 93 to be in a gas-liquid two-phase state. Then, the refrigerant decompressed in the separation gas expansion valve 82 of the separation gas pipe 80 is merged, flows through the supercooling injection pipe 93, and flows into the supercooling heat exchanger 91. In the supercooling heat exchanger 91, a low-pressure gas refrigerant that flows through the supercooling injection pipe 93 and an intermediate-pressure liquid refrigerant that is sent from the liquid refrigerant outlet pipe 83 and proceeds to the supercooling refrigerant pipe 84. Heat exchange. The refrigerant flowing from the supercooling heat exchanger 91 to the supercooling refrigerant pipe 84 is in a state where the degree of supercooling is increased. The supercooling refrigerant pipe 84 is provided with a supercooling temperature sensor 90t for detecting the temperature of the refrigerant passing therethrough. The refrigerant that flows through the supercooling injection pipe 93 and has passed through the supercooling heat exchanger 91 is in a superheated state and is sent toward the junction 65 of the low-pressure refrigerant pipe 19.

  During the heating operation, the control unit 7 closes the supercooling expansion valve 92 so that the part connected to the liquid refrigerant outlet pipe 83 and the part connected to the separation gas pipe 80 in the supercooling injection pipe 93. Although no refrigerant flows between them, the intermediate-pressure liquid refrigerant flowing through the liquid refrigerant outlet pipe 83 of the receiver 81 and the low-pressure refrigerant decompressed by the separation gas expansion valve 82 are heated in the supercooling heat exchanger 91. Will be exchanged.

(1-12) Indoor Heat Exchanger The first indoor heat exchanger 12a is provided in the first indoor unit 12. The second indoor heat exchanger 13 a is provided in the second indoor unit 13.

  The first indoor heat exchanger 12a and the second indoor heat exchanger 13a function as a refrigerant evaporator during the cooling operation (function as a refrigerant heater), and function as a refrigerant cooler during the heating operation (refrigerant refrigerant). Functions as a radiator). Water and air are flown through these first indoor heat exchanger 12a and second indoor heat exchanger 13a as a cooling object or a heating object that exchanges heat with the refrigerant flowing inside. Here, room air from each indoor blower fan (not shown) flows to the first indoor heat exchanger 12a and the second indoor heat exchanger 13a, and cooled or heated conditioned air is supplied to the room. The air volume of each indoor fan is individually controlled for load processing required in the air-conditioning target space.

  One end of the first indoor heat exchanger 12a is connected to the first indoor expansion valve 12b. One end of the second indoor heat exchanger 13a is connected to the second indoor expansion valve 13b. The other end of the first indoor heat exchanger 12a and the other end of the second indoor heat exchanger 13a are joined, and the joined portion is connected to the gas refrigerant communication pipe 15.

(1-13) Indoor Expansion Valve The first indoor expansion valve 12b is provided in the first indoor unit 12. The first indoor expansion valve 12b adjusts the amount of refrigerant flowing to the first indoor heat exchanger 12a, and performs decompression and expansion of the refrigerant. The first indoor expansion valve 12b is disposed between the liquid refrigerant communication pipe 14 and the first indoor heat exchanger 12a.

  The second indoor expansion valve 13 b is provided in the second indoor unit 13. The second indoor expansion valve 13b adjusts the amount of refrigerant flowing to the second indoor heat exchanger 13a, and performs decompression / expansion of the refrigerant. The second indoor expansion valve 13b is disposed between the liquid refrigerant communication pipe 14 and the second indoor heat exchanger 13a.

(1-14) Control Unit The control unit 7 is configured by connecting each control board on which electronic components of the outdoor unit 11, the first indoor unit 12, and the second indoor unit 13 are connected by a communication line. The compressor drive motor of the four-stage compressor 20, the four-way switching valve group 25, the expansion valves 12b, 13b, 47, 48, 52, 72, 82, 92 and the like are connected. The control unit 7 includes an indoor set temperature input from the outside, a first temperature sensor 44t1, a second temperature sensor 44t2, a third temperature sensor 41t, a first indoor temperature sensor 12t, a second indoor temperature sensor 13t, a supercooling temperature. Based on information such as sensor 90t, intermediate temperature sensor 70t, merged refrigerant temperature sensor 64t, suction pressure sensor 21p, discharge pressure sensor 24p, and measured values of a temperature sensor and a pressure sensor (not shown), the rotational speed of the compressor drive motor Control, adjustment of expansion valve opening, air volume adjustment of indoor fan and outdoor fan, etc. are performed.

  The control unit 7 has a cooling operation mode and a heating operation mode, and selectively performs one of the operations.

(2) Operation of Air Conditioner The operation of the air conditioner 1 will be described with reference to FIGS.

  FIG. 8 is a pressure-enthalpy diagram (ph diagram) of the refrigeration cycle in the cooling operation. FIG. 10 is a pressure-enthalpy diagram (ph diagram) of the refrigeration cycle in the heating operation. 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 represents the pressure and enthalpy of the refrigerant | coolant in the point represented by the same alphabetic character in FIG. 7 and FIG. 9, respectively. For example, the refrigerant at point B in FIG. 7 is in the state of pressure and enthalpy at point B in FIG. In addition, each operation control in the cooling operation and the heating operation of the air conditioner 1 is performed by the control unit 7.

(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. 7, the four-stage compressor 20, the outdoor heat exchanger 40, the expansion mechanism 70, The first indoor expansion valve 12b, the second indoor expansion valve 13b, the first indoor heat exchanger 12a, and the second indoor heat exchanger 13a are circulated in the refrigerant circuit in this order. Hereinafter, operation | movement of the air conditioning apparatus 1 at the time of air_conditionaing | cooling operation is demonstrated, referring FIG. 7 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 26 and is cooled by the first outdoor heat exchanger 41 functioning as an intercooler (intermediate cooler), and then is passed through the first intercooler pipe 41c. 2 Flows into the 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 27, is cooled by the second outdoor heat exchanger 42 functioning as an intercooler, and then flows into the second intercooler pipe 42c (point E). The refrigerant flowing through the second intercooler pipe 42c merges with the intermediate pressure refrigerant (point L) that is heat-exchanged in the economizer heat exchanger 51 and flows through the injection pipe 53, 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 28, is cooled by the third outdoor heat exchanger 43 that functions as an intercooler, and then enters the fourth suction pipe 24a via the third intercooler pipe 43c. Flow in (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 is in a supercritical state exceeding the critical pressure. This supercritical refrigerant passes through the fourth four-way switching valve 29, is cooled by the fourth outdoor heat exchanger 44 functioning as a gas cooler, passes through the third check valve 49c of the bridge circuit 49, and economizer heat exchange. It flows to the container 51 (point J).

  A part of the high-pressure refrigerant that has passed through the third check valve 49 c of the bridge circuit 49 branches into the economizer injection pipe 53 and is decompressed by the economizer expansion valve 52. The intermediate pressure refrigerant (point K) that has been reduced from the supercritical state to a pressure lower than the critical pressure in the economizer expansion valve 52 to be in a gas-liquid two-phase state is replaced with another refrigerant (bridge) in the economizer heat exchanger 51. Heat exchange with the high-pressure refrigerant (point J) exceeding the critical pressure from the circuit 49 toward the liquid gas heat exchanger 61 results in an intermediate-pressure gas refrigerant (point L). This intermediate-pressure gas refrigerant (point L) flows from the injection pipe 53 into the second intercooler pipe 42c as described above.

  The high-pressure refrigerant (point M) that exchanges heat with the intermediate-pressure refrigerant that has exited the economizer expansion valve 52, and that has exited the economizer heat exchanger 51 in a state where the temperature has further decreased, flows through the liquid gas heat exchanger 61, and the expansion mechanism. It flows to 70 (point N). The expansion mechanism 70 is controlled by the control unit 7 so that the power that can be recovered by the expander 71 can be secured as much as possible. In the liquid gas heat exchanger 61, the high-pressure refrigerant (point M) exceeding the critical pressure that has passed through the economizer heat exchanger 51 flows from the low-pressure refrigerant pipe 19 to the first suction pipe 21a and the supercooled injection pipe. The high-pressure refrigerant (point N) is cooled by heat exchange between the low-pressure refrigerant flowing through the refrigerant 93 and the merged refrigerant joined together.

  It should be noted that the temperature of the combined refrigerant in which the low-pressure refrigerant flowing from the low-pressure refrigerant pipe 19 to the first suction pipe 21a and the low-pressure refrigerant flowing through the supercooled injection pipe 93 are too low, and the expansion mechanism 70 is supplied from the liquid gas heat exchanger 61. In order to prevent the refrigerant heading to be overcooled, the control unit 7 satisfies the predetermined superheat degree condition that the superheat degree obtained from the combined refrigerant temperature sensor 64t and the suction pressure sensor 21p becomes a positive value. Performs the combined refrigerant superheat control. In this combined refrigerant superheat degree control, at least one of the opening degrees of the first indoor expansion valve 12b, the second indoor expansion valve 13b, the separation gas expansion valve 82, and the supercooling expansion valve 92 satisfies a predetermined superheat degree condition. Are finely adjusted as appropriate.

  The high-pressure refrigerant (point N) exiting the liquid gas heat exchanger 61 is branched into two, one flows toward the expander 71 of the expansion mechanism 70 and the other flows to the third outdoor expansion valve 72 of the expansion mechanism 70. It flows toward. In the third outdoor expansion valve 72, an intermediate pressure refrigerant (point O1) is obtained by reducing the pressure from the supercritical state to a pressure equal to or lower than the critical pressure. Also, in the expander 71, the pressure is reduced from the supercritical state to a pressure equal to or lower than the critical pressure, thereby becoming an intermediate pressure refrigerant (point O2). These intermediate pressure refrigerant (point O1) and intermediate pressure refrigerant (point O2) flow into the internal space of the receiver 81 after joining (point P). The gas-liquid two-phase intermediate pressure refrigerant flowing into the receiver 81 is separated into liquid refrigerant and gas refrigerant in the internal space of the receiver 81.

  The liquid refrigerant (point Q) separated by the receiver 81 flows through the liquid refrigerant outlet pipe 83. A part of the refrigerant flowing through the liquid refrigerant outlet pipe 83 passes through the supercooling heat exchanger 91 and enters a supercooled state (point W), and passes through the supercooled refrigerant pipe 84 and the first check valve 49a of the bridge circuit 49. Then, it is sent to the first indoor expansion valve 12b and the second indoor expansion valve 13b via the liquid refrigerant communication pipe 14. The other part of the refrigerant flowing through the liquid refrigerant outlet pipe 83 branches before flowing into the supercooling heat exchanger 91 and flows through the supercooling injection pipe 93. The refrigerant flowing through the supercooling injection pipe 93 is decompressed by the supercooling expansion valve 92 and becomes a low-pressure refrigerant in a gas-liquid two-phase state (point R).

  The gas refrigerant (point S) separated by the receiver 81 flows through the separation gas pipe 80. The refrigerant flowing through the separation gas pipe 80 is decompressed by the separation gas expansion valve 82 on the way, and becomes a low-pressure refrigerant (point T). The separation gas expansion valve 82 includes an intermediate pressure corresponding to the detected saturation temperature of the intermediate temperature sensor 70t provided on the downstream side of the expansion mechanism 70, and an intake pressure sensor 21p provided on the first intake pipe 21a. The valve opening (degree of expansion) is controlled by the control unit 7 (differential pressure) so that a differential pressure corresponding to the differential pressure obtained from the detected pressure can be generated before and after the separation gas expansion valve 82. Control is performed). The low-pressure refrigerant (point T) depressurized by the separation gas expansion valve 82 further flows through the separation gas pipe 80, and in the supercooling injection pipe 93 downstream of the supercooling expansion valve 92 and supercooling heat exchange. Join the upstream portion of the vessel 91 (point U).

  In the supercooling heat exchanger 91, the liquid refrigerant (point Q) separated by the receiver 81 and the gas-liquid two-phase low-pressure refrigerant (point U) joined to the supercooling injection pipe 93 via the separation gas pipe 80 and It is cooled by exchanging heat between the two, and it becomes a state with a degree of supercooling by being cooled (point W). On the other hand, the low-pressure refrigerant (point U) in the gas-liquid two-phase state joined to the supercooling injection pipe 93 via the separation gas pipe 80 is liquid refrigerant (point U) separated by the receiver 81 in the supercooling heat exchanger 91. Q) is heated (point V, where point V illustrates an overheated state, but may become wet depending on operating conditions and transient conditions). The supercooling expansion valve 92 is set so that the supercooling degree of the refrigerant flowing through the supercooling heat exchanger 91 and flowing through the supercooling refrigerant pipe 84 becomes the normal target supercooling degree (for example, the supercooling degree is 5). The degree of expansion (degree of expansion) of the supercooling expansion valve 92 is controlled by the control unit 7 so that the degree of expansion is ensured. Note that the degree of supercooling of the refrigerant flowing through the supercooling refrigerant pipe 84 is calculated by the control unit 7 from the detected temperature of the supercooling temperature sensor 90t and the intermediate pressure corresponding to the detected saturation temperature of the intermediate temperature sensor 70t.

  The refrigerant flowing into the first indoor unit 12 and the second indoor unit 13 from the liquid refrigerant communication pipe 14 expands when passing through the first indoor expansion valve 12b and the second indoor expansion valve 13b, and is a gas-liquid two-phase low pressure. It becomes a refrigerant (point X) and flows into the first indoor heat exchanger 12a and the second indoor heat exchanger 13a. This low-pressure refrigerant takes heat from the indoor air in the first indoor heat exchanger 12a and the second indoor heat exchanger 13a and becomes a superheated low-pressure gas refrigerant (point Y). The first indoor expansion valve 12b is configured so that the superheat degree of the refrigerant flowing through the outlet of the first indoor heat exchanger 12a becomes a predetermined set superheat degree (so as to satisfy the target evaporation outlet superheat degree condition). The valve opening degree (expansion degree) of the expansion valve 12 b is controlled by the control unit 7. Similarly, in the second indoor expansion valve 13b, the superheat degree of the refrigerant flowing through the outlet of the second indoor heat exchanger 13a may be a predetermined set superheat degree (the same value as that of the first indoor unit 12 or different). .) (The degree of expansion) of the second indoor expansion valve 13b is controlled so that the target evaporation outlet superheat degree condition is satisfied. The superheat degree of the refrigerant flowing through the outlet of the first indoor heat exchanger 12a is calculated by the control unit 7 from the detected temperature of the first indoor temperature sensor 12t and the detected pressure of the suction pressure sensor 21p, and the second indoor heat The control unit 7 calculates the degree of superheat of the refrigerant flowing through the outlet of the exchanger 13a from the detected temperature of the second indoor temperature sensor 13t and the detected pressure of the suction pressure sensor 21p. The low-pressure refrigerant that has exited the first indoor unit 12 and the second indoor unit 13 flows to the low-pressure refrigerant pipe 19 via the gas refrigerant communication pipe 15 and the fourth four-way switching valve 29. In addition, in the processing of the load in the room where the first indoor heat exchanger 12a is arranged, the controller 7 adjusts the air volume of the first indoor fan that supplies an air flow to the first indoor heat exchanger 12a (not shown). By processing. Similarly, for the processing of the load in the room where the second indoor heat exchanger 13a is arranged, the controller 7 controls the air volume of the second indoor fan that supplies an air flow to the second indoor heat exchanger 13a (not shown). Processing by adjusting.

  The low-pressure refrigerant (point Y) that returns from the first indoor unit 12 or the second indoor unit 13 and flows through the low-pressure refrigerant pipe 19 and the low-pressure refrigerant (point V) that flows from the supercooling injection pipe 93 are merged point 65. At the point (Z) and returns to the four-stage compressor 20 from the first suction pipe 21a through the low pressure side of the liquid gas heat exchanger 61. Here, in the liquid gas heat exchanger 61, a low-pressure refrigerant (point Z) that goes to the first suction pipe 21a of the four-stage compressor 20 and a high-pressure that goes to the expansion mechanism 70 after passing through the economizer heat exchanger 51. Heat exchange is performed with the refrigerant (point M).

  As described above, the refrigerant circulates in the refrigerant circuit, whereby the air conditioner 1 performs the cooling operation cycle.

(2-2) Operation in the heating operation mode During the heating operation, the refrigerant moves in the direction of the arrow along the refrigerant pipe shown in FIG. 9 in the four-stage compressor 20, the first indoor heat exchanger 12a, and the second indoor. The heat exchanger 13a, the first indoor expansion valve 12b, the second indoor expansion valve 13b, the expansion mechanism 70, and the outdoor heat exchanger 40 are circulated in the refrigerant circuit in this order. Hereinafter, operation | movement of the air conditioning apparatus 1 at the time of heating operation is demonstrated, referring FIG. 9 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 26 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 27 and flows through the third suction pipe 23a. In addition, since the refrigerant | coolant (point L) of the intermediate pressure which heat-exchanges in the economizer heat exchanger 51 and flows through the injection piping 53 also flows in into the 3rd suction pipe 23a, the temperature of a refrigerant | coolant falls (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 28 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 is in a supercritical state exceeding the critical pressure. This supercritical refrigerant passes through the fourth four-way switching valve 29 and flows into the first indoor unit 12 and the second indoor unit 13 via the gas refrigerant communication pipe 15 (point Y).

  The high-pressure refrigerant that has entered the first indoor unit 12 and the second indoor unit 13 from the gas refrigerant communication pipe 15 is converted into room air by the first indoor heat exchanger 12a and the second indoor heat exchanger 13a that function as a refrigerant radiator. Dissipates heat and warms indoor air. In addition, in the processing of the load in the room where the first indoor heat exchanger 12a is arranged, the controller 7 adjusts the air volume of the first indoor fan that supplies an air flow to the first indoor heat exchanger 12a (not shown). By processing. Similarly, for the processing of the load in the room where the second indoor heat exchanger 13a is arranged, the controller 7 controls the air volume of the second indoor fan that supplies an air flow to the second indoor heat exchanger 13a (not shown). Processing by adjusting. When the high-pressure refrigerant (point X) whose temperature has decreased due to heat exchange in the first indoor heat exchanger 12a or the second indoor heat exchanger 13a passes through the first indoor expansion valve 12b or the second indoor expansion valve 13b. The pressure is slightly reduced and flows through the liquid refrigerant communication pipe 14 to the bridge circuit 49 of the outdoor unit 11. In the bridge circuit 49, it passes through the second check valve 49b and goes to the economizer heat exchanger 51 (point J).

  Part of the high-pressure refrigerant (point J) that has passed through the second check valve 49 b of the bridge circuit 49 branches into the economizer injection pipe 53 and is decompressed by the economizer expansion valve 52. The intermediate pressure refrigerant (point K), which has been decompressed by the economizer expansion valve 52 and is in a gas-liquid two-phase state, is converted into another refrigerant (from the bridge circuit 49 to the liquid gas heat exchanger 61) in the economizer heat exchanger 51. It exchanges heat with the high-pressure refrigerant (point J) heading to become an intermediate-pressure gas refrigerant (point L). This intermediate-pressure gas refrigerant (point L) flows from the injection pipe 53 into the second intercooler pipe 42c as described above.

  The high-pressure refrigerant (point M) that has exchanged heat with the intermediate-pressure refrigerant that has exited the economizer expansion valve 52 and has exited the economizer heat exchanger 51 in a state where the temperature has further decreased has passed through the liquid gas heat exchanger 61, It flows to the expansion mechanism 70 (point N).

  The high-pressure refrigerant (point N) flowing into the expansion mechanism 70 is branched into two, one flows toward the expander 71 of the expansion mechanism 70 and the other flows toward the third outdoor expansion valve 72 of the expansion mechanism 70. . In the third outdoor expansion valve 72, an intermediate pressure refrigerant (point O1) is obtained by reducing the pressure from the supercritical state to a pressure equal to or lower than the critical pressure. Also, in the expander 71, the pressure is reduced from the supercritical state to a pressure equal to or lower than the critical pressure, thereby becoming an intermediate pressure refrigerant (point O2). The expansion mechanism 70 is controlled by the control unit 7 so that the power that can be recovered by the expander 71 can be secured as much as possible. These intermediate pressure refrigerant (point O1) and intermediate pressure refrigerant (point O2) flow into the internal space of the receiver 81 after joining (point P). The gas-liquid two-phase intermediate pressure refrigerant flowing into the receiver 81 is separated into liquid refrigerant and gas refrigerant in the internal space of the receiver 81.

  The liquid refrigerant (point Q) separated by the receiver 81 flows through the liquid refrigerant outlet pipe 83. All of the refrigerant flowing through the liquid refrigerant outlet pipe 83 passes through the supercooling heat exchanger 91 to be in a supercooled state (point W), passes through the supercooled refrigerant pipe 84 and the bridge circuit 49, and goes to the outdoor heat exchanger 40. Sent.

  During the heating operation, the control unit 7 controls the supercooling expansion valve 92 to be fully closed, so that the refrigerant flowing through the liquid refrigerant outlet pipe 83 is not diverted toward the supercooled injection pipe 93.

  The gas refrigerant (point S) separated by the receiver 81 flows through the separation gas pipe 80. The refrigerant flowing through the separation gas pipe 80 is decompressed by the separation gas expansion valve 82 on the way, and becomes a low-pressure refrigerant (point T). The separation gas expansion valve 82 includes an intermediate pressure corresponding to the detected saturation temperature of the intermediate temperature sensor 70t provided on the downstream side of the expansion mechanism 70, and an intake pressure sensor 21p provided on the first intake pipe 21a. The valve opening (degree of expansion) is controlled by the control unit 7 (differential pressure) so that a differential pressure corresponding to the differential pressure obtained from the detected pressure can be generated before and after the separation gas expansion valve 82. Control is performed). The low-pressure refrigerant (point T) depressurized by the separation gas expansion valve 82 further flows through the separation gas pipe 80, and in the supercooling injection pipe 93 downstream of the supercooling expansion valve 92 and supercooling heat exchange. It flows into the portion upstream of the vessel 91 (point U).

  In the supercooling heat exchanger 91, between the intermediate-pressure refrigerant (point Q) flowing from the liquid refrigerant outlet pipe 83 of the receiver 81 and the low-pressure refrigerant (points T and U) decompressed by the separation gas expansion valve 82. Heat exchange takes place. By this heat exchange, the low-pressure refrigerant (points T and U) flowing through the supercooling injection pipe 93 evaporates to become superheated low-pressure refrigerant (point V) and flows toward the junction 65. The intermediate pressure refrigerant (point Q) flowing from the liquid refrigerant outlet pipe 83 of the receiver 81 is deprived of heat and becomes an intermediate pressure refrigerant (point W) with supercooling, and is bridged via the supercooling refrigerant pipe 84. It flows toward 49.

  The refrigerant flowing in the supercooled refrigerant pipe 84 toward the bridge circuit 49 is separated so that a part flows through the common pipe 47 a before the bridge circuit 49, and the other part is the second outdoor expansion valve 48 of the bridge circuit 49. Pass through.

  The refrigerant flowing through the common pipe 47a is depressurized by the first outdoor expansion valve 47 to become a low-pressure refrigerant (point WX), and the third outdoor heat exchanger 43, the second outdoor heat exchanger 42, and the first outdoor heat exchanger 41 It flows in series. That is, the refrigerant decompressed by the first outdoor expansion valve 47 partially evaporates in the third outdoor heat exchanger 43 via the seventh pipe 43b. The refrigerant that has passed through the third outdoor heat exchanger 43 passes through the third pipe 43a, the third four-way switching valve 28, a part of the second intercooler pipe 42c, and the sixth pipe 42b in this order, Part of the two outdoor heat exchangers 42 further evaporates. The refrigerant that has passed through the second outdoor heat exchanger 42 passes through the second pipe 42a, the second four-way switching valve 27, a part of the first intercooler pipe 41c, and the fifth pipe 41b in this order, In the outdoor heat exchanger 41, a part further evaporates. The refrigerant that has passed through the first outdoor heat exchanger 41 flows toward the low-pressure refrigerant pipe 19 after passing through the first pipe 41a, the first four-way switching valve 26, and the four-way connection pipe 30 in this order. Here, the control unit 7 detects the temperature detected by the first temperature sensor 44t1 provided on the upstream side of the fourth outdoor heat exchanger 44 (substantially the temperature of the refrigerant flowing upstream of the third outdoor heat exchanger 43). Equal to the detected temperature) and the detected temperature of the third temperature sensor 41t provided on the downstream side of the first outdoor heat exchanger 41 (41t−44t1) so that the difference is greater than 3 degrees. The degree of pressure reduction (valve opening) of the expansion valve 47 is controlled. For example, when the temperature difference (41t−44t1) becomes 3 degrees or less, the control unit 7 performs control so that the valve opening degree of the first outdoor expansion valve 47 becomes small. By this control, the refrigerant that has passed through the first outdoor heat exchanger 41 has a degree of superheat.

  On the other hand, the refrigerant (point VW) decompressed through the second outdoor expansion valve 48 of the bridge circuit 49 evaporates in the fourth outdoor heat exchanger 44 after flowing through the eighth pipe 44b, and the fourth pipe 44a. It passes through the fourth four-way selector valve 29 and flows toward the low-pressure refrigerant pipe 19 (point XY). Here, the control unit 7 detects the temperature detected by the first temperature sensor 44t1 provided on the upstream side of the fourth outdoor heat exchanger 44 and the second temperature sensor 44t2 provided on the downstream side of the fourth outdoor heat exchanger 44. The degree of pressure reduction (valve opening degree) of the second outdoor expansion valve 48 is controlled so that the difference (44t2-44t1) with the detected temperature is less than 1 degree which is a value smaller than the difference (41t-44t1). To do. For example, when the temperature difference (44t2-44t1) becomes 1 degree or more, the control unit 7 performs control to increase the valve opening degree of the second outdoor expansion valve 48. By this control, it is possible to avoid the refrigerant having passed through the fourth outdoor heat exchanger 44 from being excessively heated. For this reason, in the 4th outdoor heat exchanger 44, the refrigerant | coolant is evaporated in the whole region inside, the part through which the evaporated refrigerant | coolant has flowed is lost, and the 4th outdoor heat exchanger 44 is. It is possible to fully demonstrate the ability of.

  Thereafter, the refrigerant that has passed through the first to fourth outdoor heat exchangers 41 to 44 flows through the low-pressure refrigerant pipe 19.

  The low-pressure gas refrigerant (point XY) flowing through the low-pressure refrigerant pipe 19 merges with the low-pressure gas refrigerant (point V) flowing through the supercooled injection pipe 93 at the junction 65 (point Z), and then the liquid gas heat exchanger. The liquid gas heat exchanger 61 exchanges heat with the high-pressure side refrigerant. Here, the control section 7 flows after the refrigerant flowing through the low-pressure refrigerant pipe 19 and the refrigerant flowing through the supercooled injection pipe 93 and before flowing into the liquid gas heat exchanger 61 (flowing through the junction 65). With respect to the refrigerant), a predetermined degree of superheat occurred using the detection temperature of the combined refrigerant temperature sensor 64t provided on the downstream side of the low pressure side of the liquid gas heat exchanger 61 and the detection pressure of the suction pressure sensor 21p. The valve opening degree of the separation gas expansion valve 82 is controlled so as to be in a state (not particularly limited, but in a state where the degree of superheat is 3 degrees or more in this embodiment). For example, when a predetermined degree of superheat has not occurred in the refrigerant at the junction 65, the control unit 7 increases the opening degree of the separation gas expansion valve 82 to increase the refrigerant having the degree of superheat to the junction 65. Control to guide. Thereby, the state where the temperature of the refrigerant flowing into the low pressure side of the liquid gas heat exchanger 61 is too low can be avoided, and the refrigerant going from the liquid gas heat exchanger 61 to the expansion mechanism 70 is prevented from being cooled too much. be able to. When the opening degree of the separation gas expansion valve 82 is increased, the intermediate pressure of the system decreases, the amount of liquid refrigerant flowing out from the receiver 81 decreases, and the outdoor heat is passed through the supercooling heat exchanger 91. Since the amount of refrigerant directed to the exchanger 40 is reduced, the superheat degree of the refrigerant on the low pressure side of the liquid gas heat exchanger 61 can be increased due to this.

  The low-pressure gas refrigerant that has passed through the low-pressure side of the liquid gas heat exchanger 61 is sucked into the four-stage compressor 20 through the first suction pipe 21a (point A).

  As described above, the refrigerant circulates in the refrigerant circuit, whereby the air conditioner 1 performs the heating operation cycle.

(3) Features of the air conditioner (3-1)
In the air conditioner 1 of the present embodiment, during the cooling operation, the intermediate pressure refrigerant discharged from the first to third compression units 21 to 23 is supplied to the first to third outdoor heat exchangers 41 to 43, respectively. Can be cooled. During the heating operation, while using the first to third outdoor heat exchangers 41 to 43 configured to be able to cool the refrigerant at each intermediate pressure in the cooling operation, these are serially connected to each other. By making the connection, it is possible to evaporate the refrigerant passing as a whole.

  Here, in the 4th outdoor heat exchanger 44 at the time of heating operation, the valve opening degree of the 2nd outdoor expansion valve 48 is controlled so that it can avoid that an excessive superheat degree arises in an exit refrigerant | coolant. Thereby, in the 2nd outdoor heat exchanger 44, it can suppress the area | region through which the evaporated refrigerant | coolant passes small, and can fully demonstrate the capability of the 2nd outdoor heat exchanger 44. FIG.

  Moreover, in the 1st-3rd outdoor heat exchangers 41-43 connected mutually in series at the time of heating operation, the 1st outdoor heat exchanger 41 which is the most downstream side has the degree of superheat so that the outlet refrigerant has the degree of superheat. The one outdoor expansion valve 47 is controlled.

  Thus, the combined refrigerant of the refrigerant that has passed through the fourth outdoor heat exchanger 44 and the refrigerant that has passed through the first to third outdoor heat exchangers 41 to 43 is superheated that has passed through the fourth outdoor heat exchanger 44. A refrigerant having a small degree and a refrigerant having a large degree of superheat having passed through the first to third outdoor heat exchangers 41 to 43 are mixed. For this reason, it is possible to adjust the superheat degree of the combined refrigerant by controlling the valve opening ratio of the first outdoor expansion valve 47 and the second outdoor expansion valve 48 to control the mixing ratio.

(3-2)
If it is unavoidable that the temperature of the refrigerant on the low pressure side of the liquid gas heat exchanger 61 becomes too low, the refrigerant (pressure) on the high pressure side and low enthalpy side in the pressure-enthalpy diagram. -The refrigerant in the upper left part of the enthalpy diagram) is overcooled in the liquid gas heat exchanger 61 and goes too far to the low enthalpy side (too much to the left side in the pressure-enthalpy diagram). In that state, if the refrigerant after being decompressed in the expansion mechanism 70 cannot be made into a gas-liquid two-phase state and all the refrigerants are in a liquid single-phase state, the refrigerant flowing into the receiver 81 Since it will be in a phase state, the gas-liquid separation function in the receiver 81 cannot be exhibited. If it does so, control of an excess refrigerant | coolant will become difficult and there exists a problem that the low pressure of a refrigerating cycle will reduce unintentionally.

  On the other hand, in this air conditioner 1, since the degree of superheat of the refrigerant flowing into the liquid gas heat exchanger 61 can be adjusted, the temperature of the refrigerant on the low pressure side of the liquid gas heat exchanger 61 becomes too low. It is possible to avoid that. Therefore, the above problem can be made difficult to occur.

(3-3)
In the air conditioning apparatus 1, the adjustment of the superheat degree of the refrigerant flowing into the liquid gas heat exchanger 61 is performed by adjusting the refrigerant that has passed through the fourth outdoor heat exchanger 44 and the first to third outdoor heat exchangers 41 to 43. Fine adjustment can be performed not only by adjusting the merging ratio with the refrigerant that has passed, but also by adjusting the mixing ratio of the refrigerant that has passed through the supercooling injection pipe 93.

  For this reason, only by adjusting the merging ratio between the refrigerant that has passed through the fourth outdoor heat exchanger 44 and the refrigerant that has passed through the first to third outdoor heat exchangers 41 to 43, the liquid gas heat exchanger 61. Even if a situation occurs in which the temperature of the refrigerant flowing into the tank cannot be sufficiently increased, the mixing ratio of the refrigerant that has passed through the supercooling injection pipe 93 is adjusted (the opening degree of the separation gas expansion valve 82 is adjusted). Therefore, it can be avoided that the temperature of the refrigerant on the low pressure side of the liquid gas heat exchanger 61 becomes too low.

(3-4)
In the air conditioner 1, the first to third outdoor heat exchangers 41 to 43 among the outdoor heat exchangers 40 have Y-tubes 41k, 42k, 43k, 41j at the inlet and outlet, as shown in FIG. Since 42j and 43j are provided, at least a part of the refrigerant can flow through the outer heat transfer tubes 41g, 42g, and 43g in both the cooling operation and the heating operation.

  For this reason, the refrigerant flowing through the outer heat transfer tubes 41g, 42g, and 43g can perform heat exchange between the air and the refrigerant on the upstream side of the air flow, so that the temperature difference is sufficiently secured. Heat exchange is possible.

  In particular, the first to third outdoor heat exchangers 41 to 43 are devices having high heat exchange efficiency in which a flat multi-hole tube made of aluminum or an aluminum alloy is employed. Therefore, the outer heat transfer tubes 41g, 42g, The efficiency of heat exchange at 43 g can be significantly increased.

(3-5)
In the air conditioning apparatus 1, the fourth outdoor heat exchanger 44 of the outdoor heat exchanger 40 is provided with a U-shaped tube 44 i at one end as shown in FIG. 4. For this reason, during the cooling operation, the outlet of the fourth outdoor heat exchanger 44 is positioned at the inner heat transfer tube 44h, and the outlet is positioned at the outer heat transfer tube 44g, so that the outlet refrigerant is heated with the air upstream in the air flow direction. The outlet refrigerant can be exchanged for heat exchange with air having a large temperature difference. For this reason, in the cooling operation, the ability of the fourth outdoor heat exchanger 44 can be exhibited more.

  As described above, even when the usage condition of the fourth outdoor heat exchanger 44 during the cooling operation is arranged to be more advantageous than during the heating operation, the air conditioner 1 performs the heating operation during the heating operation. Since the control is performed so that the degree of superheat of the outlet refrigerant of the fourth outdoor heat exchanger 44 does not become too large, the ability of the fourth outdoor heat exchanger 44 can be exhibited as much as possible.

  Specifically, during the heating operation, as shown in FIG. 4, the refrigerant inlet of the fourth outdoor heat exchanger 44 is located in the outer heat transfer pipe 44g, and the refrigerant outlet is located in the inner heat transfer pipe 44h. Yes. For this reason, the refrigerant flowing through the outlet of the refrigerant is subjected to heat exchange with the air whose temperature has already decreased due to the heat exchange already performed on the upstream side, and the temperature between the refrigerant and the air during the heat exchange. It becomes difficult to secure a sufficient difference. In particular, the fourth outdoor heat exchanger 44 is a device with high heat exchange efficiency that employs a flat multi-hole tube made of aluminum or an aluminum alloy, and therefore, the temperature of the air reaching the inner heat transfer tube 44h is conspicuous. As a result, the temperature difference between the refrigerant and air becomes more difficult to secure.

  Even in this case, in the air conditioner 1, the valve opening degree of the second outdoor expansion valve 48 is controlled so that the degree of superheat of the outlet refrigerant of the fourth outdoor heat exchanger 44 does not become too large. For this reason, in the 4th outdoor heat exchanger 44, the area | region where the evaporated refrigerant | coolant has flowed can be made small, and it becomes possible to utilize the whole 4th outdoor heat exchanger 44 effectively.

(3-6)
In the air conditioner 1, in the heating operation state, the refrigerant flows in parallel with the first to third outdoor heat exchangers 41 to 43 and the fourth outdoor heat exchanger 44 that are connected in series with each other. .

  Here, as shown in FIG. 5, the first to third outdoor heat exchangers 41 to 43 do not have a flow flowing back in the heat exchanger, and the refrigerant flowing from the inlet is the outdoor unit 11. After flowing along the three side surfaces of the housing, it flows out from the outlet. When this distance is L, when the first to third outdoor heat exchangers 41 to 43 are connected in series with each other, the refrigerant flows through a total distance of 3L.

  On the other hand, as shown in FIG. 4, the fourth outdoor heat exchanger 44 has a flow that flows back in the heat exchanger, and the refrigerant that flows in from the inlet flows into the casing of the outdoor unit 11. After flowing along the three side surfaces, it is folded back, flows again along the three side surfaces of the casing of the outdoor unit 11, and then flows out from the outlet. For this reason, in the 4th outdoor heat exchanger 44, a refrigerant | coolant flows through the distance of 2L.

  Thus, in the first to third outdoor heat exchangers 41 to 43, the refrigerant flows through a distance of 3L, and the distance at which heat exchange is performed is longer than the distance of 2L in the fourth outdoor heat exchanger 44. Therefore, the refrigerant that has passed through the first to third outdoor heat exchangers 41 to 43 tends to be in a dry state. For this reason, it can be easily performed to control the refrigerant having passed through the first to third outdoor heat exchangers 41 to 43 to have a superheat degree.

  And since the capacity | capacitance of the 4th outdoor heat exchanger 44 is larger than the other 1st-3rd outdoor heat exchangers 41-43, it is desired to use as effectively as possible, and the 2nd outdoor expansion valve 48 is controlled. Then, by controlling the refrigerant so as to be damper than the refrigerant that has passed through the first to third outdoor heat exchangers 41 to 43, the area where the evaporated refrigerant flows in the fourth outdoor heat exchanger 44 is reduced, and the capacity is increased. It can make it easy to demonstrate. In addition, the refrigerant that has passed through the fourth outdoor heat exchanger 44 can be made more moist than the refrigerant that has passed through the first to third outdoor heat exchangers 41 to 43.

  By doing in this way, the refrigerant that has passed through the first to third outdoor heat exchangers 41 to 43 is controlled to be drier, the refrigerant that has passed through the fourth outdoor heat exchanger 44 is controlled to be damper, The degree of superheat of the refrigerant sent to the liquid gas heat exchanger 61 can be adjusted by adjusting the mixing ratio of the two.

(3-7)
In addition, the air conditioner 1 includes the economizer heat exchanger 51 that cools the high-pressure refrigerant that exceeds the critical pressure, thereby enabling an economizer effect. However, by providing the economizer heat exchanger 51, the refrigerant on the high pressure side and low enthalpy side in the pressure-enthalpy diagram (refrigerant in the upper left portion of the pressure-enthalpy diagram) is a liquid gas heat exchanger. There is a case where a state where the air is overcooled at 61 and goes too far to the low enthalpy side (too much leftward in the pressure-enthalpy diagram) is likely to occur.

  On the other hand, in the air conditioner 1, even when the economizer heat exchanger 51 is provided and the economizer effect is achieved as described above, the low-pressure inlet refrigerant of the liquid gas heat exchanger 61 can be obtained. Since it is possible to avoid a state in which the temperature is too low, it is possible to prevent the control of the surplus refrigerant and the low pressure of the refrigeration cycle from being unintentionally reduced.

(3-8)
Further, the air conditioner 1 is used in a state where the high pressure side exceeds the critical pressure, but the refrigerant flowing into the receiver 81 is decompressed to a state below the critical pressure by the expansion mechanism 70. For this reason, the refrigerant flowing into the receiver 81 is not a supercritical state, but a refrigerant having a critical pressure or less that can be in a gas-liquid two-phase state. In addition, since it is possible to avoid a state in which the temperature of the low-pressure inlet refrigerant of the liquid gas heat exchanger 61 is too cold, the liquid single-phase refrigerant does not flow into the receiver 81, and the gas-liquid separation in the receiver 81 is avoided. It is possible to ensure that the function is exhibited.

(4) Modification (4-1) Modification A
In the above embodiment, during the heating operation, the valve opening degree of the second outdoor expansion valve 48 is controlled so that the refrigerant temperature difference at the inlet / outlet of the fourth outdoor heat exchanger 4 is less than 1 degree, and the first to third The case where the valve opening degree of the first outdoor expansion valve 47 is controlled so that the refrigerant temperature difference between the inlets and outlets of the outdoor heat exchangers 41 to 43 is greater than 3 degrees has been described as an example.

  However, during the heating operation, the refrigerant temperature difference at the inlet / outlet of the first to third outdoor heat exchangers 41 to 43 is 3 while the refrigerant temperature difference at the inlet / outlet of the fourth outdoor heat exchanger 4 is less than 1 degree. In addition, the combined refrigerant of the refrigerant that has passed through the fourth outdoor heat exchanger 44 and the refrigerant that has passed through the first to third outdoor heat exchangers 41 to 43 is as dry as possible. The second outdoor expansion valve 48 and the first outdoor expansion valve 47 may be controlled. Although it does not specifically limit as this control, For example, when the combined refrigerant | coolant with the refrigerant | coolant which passed the 4th outdoor heat exchanger 44 and the refrigerant | coolant which passed the 1st-3rd outdoor heat exchangers 41-43 is wet. The control may be performed such that the valve opening degree of the second outdoor expansion valve 48 is reduced as much as possible while maintaining the refrigerant temperature difference at the inlet / outlet of the fourth outdoor heat exchanger 4 to be less than 1 degree. In this way, the combined refrigerant of the refrigerant that has passed through the fourth outdoor heat exchanger 44 and the refrigerant that has passed through the first to third outdoor heat exchangers 41 to 43 can be made as dry as possible. The refrigerant at the low-pressure inlet of the liquid gas heat exchanger 61 can be made as dry as possible without depending on the amount of dry refrigerant that merges through the supercooling injection pipe 93.

(4-2) Modification B
In the above embodiment, during the heating operation, the valve opening degree of the second outdoor expansion valve 48 is controlled so that the refrigerant temperature difference at the inlet / outlet of the fourth outdoor heat exchanger 4 is less than 1 degree, and the first to third The case where the valve opening degree of the first outdoor expansion valve 47 is controlled so that the refrigerant temperature difference between the inlets and outlets of the outdoor heat exchangers 41 to 43 is greater than 3 degrees has been described as an example.

  However, the temperature difference of the control is not limited to the values exemplified in the above embodiment, and the target temperature difference (or outlet refrigerant) in the heat exchanger that secures as much as possible the area where heat exchange is performed. As long as the target dryness of the other heat exchanger is smaller than the target temperature difference (or the target dryness of the outlet refrigerant).

  For example, the valve opening degree of the second outdoor expansion valve 48 may be controlled so that the refrigerant at the outlet of the fourth outdoor heat exchanger 44 does not have a dryness and is slightly moist. For example, the superheat degree of the refrigerant at the outlets of the first to third outdoor heat exchangers 41 to 43 may be controlled to be 4 degrees or more.

(4-3) Modification C
In the above embodiment, the air conditioner 1 that employs the four-stage compressor 20 that performs four-stage compression has been described as an example.

  However, it is not limited to an air conditioner that performs four-stage compression, and may be, for example, an air conditioner that performs two-stage compression or three-stage compression.

  For example, in an air conditioner that performs two-stage compression, there is one heat exchanger that functions as an intercooler (intercooler) during cooling operation and functions as an evaporator connected in parallel during heating operation. In an air conditioner that performs three-stage compression, there are two heat exchangers that function as an intercooler (intercooler) during cooling operation and function as an evaporator connected in parallel during heating operation.

(4-4) Modification D
In the above-described embodiment, an example in which the outlet refrigerant of the fourth outdoor heat exchanger 44 is controlled to be wet in order to ensure as much as possible an area where the refrigerant is evaporated during heating operation will be described. did.

  However, the target heat exchanger that controls the outlet refrigerant in a damp manner may be a heat exchanger that functions as an intercooler (intermediate cooler) during cooling operation and functions as an evaporator connected in parallel during heating operation. .

  For example, in a two-stage compression air conditioner, there is one heat exchanger that functions as an intercooler (intercooler) during cooling operation and functions as an evaporator connected in parallel during heating operation. For this reason, the heat exchangers to be flown in parallel during the heating operation tend to have a short distance through which the refrigerant flows in the heat exchanger without being connected in series with each other. For this reason, in a heat exchanger that functions as an intercooler (intermediate cooler) during cooling operation and functions as an evaporator connected in parallel during heating operation, a refrigerant that cannot be completely evaporated may easily be generated. In this case, the heat exchanger functioning as an intercooler (intercooler) during cooling operation and functioning as an evaporator connected in parallel during heating operation is controlled so that the outlet refrigerant during heating operation becomes damp. The outlet refrigerant of the other evaporator connected in parallel during the heating operation may be controlled to be dry.

(4-5) Modification E
4 and 5, the fourth outdoor heat exchanger 44 and the first to third outdoor heat exchangers 41 to 43 have different configurations in which the refrigerant flows. The case where it exists is described as an example.

  However, the flow of these refrigerants is not particularly limited. For example, the fourth outdoor heat exchanger 44 and the first to third outdoor heat exchangers 41 to 43 may be configured to have the same refrigerant flow.

(4-6) Modification F
In the above embodiment, the case where various controls are performed so that the refrigerant at the low-pressure side inlet of the liquid gas heat exchanger 61 has a predetermined superheat degree (superheat degree of 3 degrees or more) has been described as an example.

  However, the inlet on the low pressure side of the liquid gas heat exchanger 61 is not limited to the case where a refrigerant controlled to have a superheat degree flows, and the refrigerant flowing on the high pressure side of the liquid gas heat exchanger 61 must be excessively cooled. For example, a slightly moist refrigerant may flow.

1 Air conditioning equipment (refrigeration equipment)
7 Control unit 12 Indoor unit 12a First indoor heat exchanger, indoor heat exchanger (use side heat exchanger)
12b 1st indoor expansion valve, indoor expansion valve 12t 1st indoor temperature sensor 13 2nd indoor unit, indoor unit 13a 1st indoor heat exchanger, indoor heat exchanger (use side heat exchanger)
13b 2nd indoor expansion valve, indoor expansion valve 13t 2nd indoor temperature sensor 20 Four stage compressor 21 1st compression part (low stage side compression part)
21p Suction pressure sensor 22 2nd compression part (intermediate compression part)
23 3rd compression part (intermediate compression part)
24 4th compression part (high stage side compression part)
24p Discharge pressure sensor 25 Four-way switching valve group (operating state switching part)
26 First four-way switching valve 27 Second four-way switching valve 28 Third four-way switching valve 29 Fourth four-way switching valve 30 Four-way connection pipe 40 Outdoor heat exchanger 41 First outdoor heat exchanger (heat source side second Heat exchanger)
42 2nd outdoor heat exchanger (heat source side 2nd heat exchanger, heat source side 3rd heat exchanger)
43 3rd outdoor heat exchanger (heat source side 2nd heat exchanger, heat source side 3rd heat exchanger)
44 4th outdoor heat exchanger (heat source side first heat exchanger)
41c 1st intercooler pipe 42c 2nd intercooler pipe 43c 3rd intercooler pipe 41a 1st piping 42a 2nd piping 43a 3rd piping 44a 4th piping 41g, 42g, 43g Outer heat transfer pipe (upstream refrigerant flow path)
41h, 42h, 43h Inner heat transfer tube (downstream refrigerant flow path)
44g Outer heat transfer tube (upstream refrigerant flow path)
44h Inner heat transfer tube (downstream refrigerant flow path)
45 Outdoor blower fan (heat source side first blower, heat source side second blower)
47 First outdoor expansion valve (first expansion mechanism)
48 Second outdoor expansion valve (second expansion mechanism)
49 bridge circuit 50 economizer circuit 51 economizer heat exchanger 52 economizer expansion valve 53 economizer injection piping 60 liquid gas heat exchange circuit 61 liquid gas heat exchanger 64t combined refrigerant temperature sensor 70 expansion mechanism (third expansion mechanism)
70p Intermediate temperature sensor 71 Expander 72 Expansion valve 80 Separation gas piping 81 Receiver (refrigerant container)
82 Separation gas expansion valve (bypass expansion mechanism)
83 Liquid refrigerant outlet pipe 90 Supercooling circuit 90t Supercooling temperature sensor 91 Supercooling heat exchanger 92 Supercooling expansion valve 93 Supercooling injection piping (bypass circuit)

JP 2010-112618 A

Claims (9)

A lower stage compression section (21);
A high-stage compression section (24) for further compressing the refrigerant after being compressed by the low-stage compression section;
A heat source side first heat exchanger (44);
A heat source side second heat exchanger (41, 42, 43);
Utilization side heat exchangers (12a, 13a);
A first expansion mechanism (47);
A second expansion mechanism (48);
The use side heat exchangers (12a, 13a) function as a refrigerant cooler, the heat source side first heat exchanger (44) functions as a refrigerant evaporator, and the heat source side second heat exchanger (41 , 42, 43) function as a refrigerant evaporator connected in parallel with the heat source side first heat exchanger (44) in the refrigerant flow, and from the use side heat exchangers (12a, 13a) to the heat source side first The refrigerant going to the two heat exchangers (41, 42, 43) is depressurized by the first expansion mechanism (47), and from the use side heat exchanger (12a, 13a) to the heat source side first heat exchanger (44). A first operating state in which the refrigerant directed to the first pressure is decompressed by the second expansion mechanism (48);
The heat source side second heat exchanger (41, 42, 43) is discharged from the low stage compression section (21) and then functions as a refrigerant cooler toward the high stage compression section (24), The heat source side first heat exchanger (44) is caused to function as a cooler for the refrigerant discharged from the high stage side compression unit (24), and the heat source side first heat exchanger (44) is used as the utilization side heat exchanger. A second operating state in which the refrigerant directed to (12a, 13a) is depressurized by the second expansion mechanism (48), and the use side heat exchanger (12a, 13a) functions as an evaporator of the refrigerant;
An operating state switching unit (25) for switching between
In the state where the operation state switching unit (25) is switched to the first operation state, the refrigerant flowing through the outlet of the heat source side first heat exchanger (44) and the heat source side second heat exchanger (41, 42, 43) so that one of the refrigerants flowing through the outlets has a degree of superheat, and the other has a smaller degree of superheat or a damp state than the state having the degree of superheat. And a controller (7) for adjusting the degree of pressure reduction in the first expansion mechanism (47) and the second expansion mechanism (48),
A refrigeration apparatus (1). The controller (7) is a refrigerant that flows through an outlet of the heat source side second heat exchanger (41, 42, 43) in a state where the operating state switching unit (25) is switched to the first operating state. Is in a state where the refrigerant flowing through the outlet of the first heat exchanger (44) at the heat source side is less superheated or moist than the state having the superheat degree. Adjusting the degree of pressure reduction in the first expansion mechanism (47) and the second expansion mechanism (48),
The refrigeration apparatus (1) according to claim 1. A heat source side first air blower (45) for supplying air to the heat source side first heat exchanger (44);
The heat source side first heat exchanger (44) has refrigerant flow paths on the upstream side and the downstream side in the flow direction of the air supplied by the heat source side first blower (45),
The refrigerant outlet vicinity portion of the heat source side first heat exchanger (44) in the first operation state is located on the downstream side in the air flow direction,
The refrigerant outlet vicinity part of the heat source side first heat exchanger (44) in the second operation state is located on the upstream side in the air flow direction,
The refrigeration apparatus according to claim 2. The heat source side first heat exchanger (44) has fins and a flat multi-hole tube having a plurality of passages arranged in the horizontal direction, and is made of aluminum or an aluminum alloy.
The refrigeration apparatus according to claim 3. A heat source side second air blowing section (45) for supplying air to the heat source side second heat exchanger (41, 42, 43);
The said heat source side 2nd heat exchanger (41, 42, 43) has a refrigerant | coolant flow path in the upstream and downstream in the flow direction of the air supplied by the said heat source side 2nd ventilation part (45). ,
The refrigerant of the heat source side second heat exchanger (41, 42, 43) regardless of whether the operation state switching unit (25) is switched to the first operation state or the second operation state. At least a part of the vicinity of the outlet is configured to be located on the upstream side in the air flow direction,
The refrigeration apparatus according to any one of claims 2 to 4. An intermediate compression section (22, 23) that further compresses the refrigerant compressed by the low-stage compression section (21) and sends it to the high-stage compression section (24);
A heat source side third heat exchanger (42, 43);
Further comprising
The operating state switching unit (25)
In the first operation state, the use side heat exchangers (12a, 13a) function as a refrigerant cooler, the heat source side first heat exchanger (44) functions as a refrigerant evaporator, and the heat source side While the second heat exchanger (41) and the third heat exchanger on the heat source side (42, 43) are connected in series, the series heat exchanger (41, 42, 43) , 42, 43) function as a refrigerant evaporator connected in parallel with the heat source side first heat exchanger (44) in the refrigerant flow, and the series heat exchange from the use side heat exchangers (12a, 13a). Refrigerant heading toward the heat source side first heat exchanger (44) from the use side heat exchanger (12a, 13a) is decompressed by the first expansion mechanism (47). Is reduced in pressure by the second expansion mechanism (48). ,
In the second operation state, the heat source side second heat exchanger (41) functions as a refrigerant cooler that is discharged from the low-stage compression unit (21) and then travels to the intermediate compression unit (22, 23). The third heat exchanger on the heat source side (42, 43) is discharged from the intermediate compression part (22, 23) and then functions as a refrigerant cooler toward the higher stage compression part (24), The heat source side first heat exchanger (44) is caused to function as a cooler for the refrigerant discharged from the high stage side compression unit (24), and the heat source side first heat exchanger (44) is used as the utilization side heat exchanger. (12a, 13a) is depressurized by the second expansion mechanism (48), and the use side heat exchanger (12a, 13a) functions as a refrigerant evaporator,
The refrigeration apparatus according to any one of claims 2 to 5. A third expansion mechanism (70) provided between the heat source side first heat exchanger (44) and the use side heat exchangers (12a, 13a) and depressurizing the refrigerant passing therethrough;
A refrigerant container (81) which is a container for separating the refrigerant decompressed in the third expansion mechanism (70) into a gas phase and a liquid phase;
The refrigerant that has flowed out of the heat exchanger functioning as a refrigerant cooler among the use side heat exchangers (12a, 13a) and the heat source side first heat exchanger (44), the third expansion mechanism ( 70) functioning as a refrigerant evaporator among the refrigerant going to the refrigerant container (81), the use side heat exchangers (12a, 13a), and the heat source side first heat exchanger (44). A liquid gas heat exchanger (61) that exchanges heat with the refrigerant that has flowed out of the heat exchanger and is directed to the low-stage compression section (21);
Refrigerant containing at least the refrigerant extracted from the gas phase portion of the refrigerant container (81) flows into the refrigerant flowing out of the heat exchanger functioning as the evaporator toward the liquid gas heat exchanger (61). A bypass circuit (93) for merging,
A bypass expansion mechanism (82) for depressurizing the refrigerant from the refrigerant container (81) to the liquid gas heat exchanger (61);
The refrigeration apparatus according to any one of claims 1 to 6, further comprising: The control unit (7) includes a heat exchanger functioning as the evaporator of the liquid gas heat exchanger in a state where the operation state switching unit (25) is switched to the first operation state. The degree of superheat of the refrigerant into which the refrigerant flowing out flows is controlled by adjusting the degree of pressure reduction in the first expansion mechanism (47), the second expansion mechanism (48), and the bypass expansion mechanism (82, 92). To
The refrigeration apparatus according to claim 7. The controller (7) is configured so that a refrigerant at an outlet of the heat source side first heat exchanger (44) satisfies a predetermined condition in a state where the operation state switching unit (25) is switched to the first operation state. By reducing the amount of refrigerant passing through the first expansion mechanism (47) so as to maintain the state, the refrigerant that has flowed out of the heat exchanger functioning as the evaporator of the liquid gas heat exchanger flows in. Increase the superheat of the refrigerant in the part,
The refrigeration apparatus according to claim 8.

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