JP2009133580A - Refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the humidity wetness of a refrigerant sucked to a latter stage-side compressing element in an inverse cycle defrosting operation, in a refrigerating device having a refrigerant circuit constituted to switch a cooling operation and a heating operation, and performing a multistage compression type refrigerating cycle by using a refrigerant activated in a supercritical region. <P>SOLUTION: An air conditioner 1 uses a carbon dioxide as the refrigerant, and comprises a two-stage compression type compressing mechanism 2, a heat source-side heat exchanger 4, an expanding mechanism 5, an utilization-side heat exchanger 6, a switching mechanism 3, an intermediate cooler 7 and a latter stage-side injection pipe 19. In the air conditioner 1, the refrigerant flows in the heat source-side heat exchanger 4, the intermediate cooler 7 and the latter stage-side injection pipe 19 in the inverse cycle defrosting operation for defrosting the heat source-side heat exchanger 4 by switching the switching mechanism 3 to a cooling operation state, and a flow rate of the refrigerant returned to the latter stage-side compressing element through the latter stage-side injection pipe 19 is reduced when it is detected that the refrigerant is condensed in the intermediate cooler 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a refrigeration apparatus, and more particularly to a refrigeration apparatus having a refrigerant circuit configured to be able to switch between a cooling operation and a heating operation and performing a multistage compression refrigeration cycle using a refrigerant operating in a supercritical region.

Conventionally, as one of refrigeration apparatuses having a refrigerant circuit configured to be able to switch between a cooling operation and a heating operation and performing a multistage compression refrigeration cycle using a refrigerant operating in a supercritical region, Patent Document 1 There is an air conditioner that has a refrigerant circuit configured to be capable of switching between a cooling operation and a heating operation, and performs a two-stage compression refrigeration cycle using carbon dioxide as a refrigerant. This air conditioner mainly includes a compressor having two compression elements connected in series, a four-way switching valve for switching between cooling operation and heating operation, an outdoor heat exchanger, an expansion valve, And a heat exchanger.
JP 2007-232263 A

  In the above-described air conditioner, the critical temperature (about 31 ° C.) of carbon dioxide used as a refrigerant is the temperature of water or air that serves as a cooling source for an outdoor heat exchanger or an indoor heat exchanger that functions as a refrigerant cooler. Since it is the same level and lower than refrigerants such as R22 and R410A, the high pressure of the refrigeration cycle is higher than the critical pressure of the refrigerant so that the refrigerant can be cooled by water or air in these heat exchangers. Driving will be done in the state. Due to this, the temperature of the refrigerant discharged from the compression element on the rear stage side of the compressor increases, so in the outdoor heat exchanger that functions as a refrigerant cooler, water and air as a cooling source, and the refrigerant The temperature difference between the two becomes large, and the heat dissipation loss in the outdoor heat exchanger becomes large. Therefore, there is a problem that it is difficult to obtain high operating efficiency.

  In order to solve this problem, the inventor of the present application discharged an intermediate cooler functioning as a refrigerant cooler discharged from the preceding compression element and sucked into the latter compression element from the preceding compression element. Provided in the intermediate refrigerant pipe for sucking the refrigerant into the compression element on the downstream side, and provided with an intermediate cooler bypass pipe connected to the intermediate refrigerant pipe so as to bypass the intermediate cooler. When the switching mechanism corresponding to the above-described four-way switching valve is in the cooling operation state corresponding to the cooling operation, the intermediate cooler functions as a cooler, and the switching mechanism is set in the heating operation state corresponding to the heating operation. During the cooling operation, the temperature of the refrigerant discharged from the compression mechanism corresponding to the above-described compressor is kept low so that the intermediate cooler does not function as a cooler. Information, suppressing the heat radiation to the outside, invented to prevent a decrease in operating efficiency (Japanese Patent Application No. 2007-255107).

  By the way, in this refrigeration apparatus, when a heat exchanger using air as the heat source is adopted as the heat source side heat exchanger, when the heating operation is performed under a condition where the temperature of the air as the heat source is low, the refrigerant heater Therefore, it is necessary to perform a defrosting operation for defrosting the heat source side heat exchanger by causing the heat source side heat exchanger to function as a refrigerant cooler. As this defrosting operation, it is conceivable to employ a reverse cycle defrosting operation in which the heat source side heat exchanger functions as a refrigerant cooler by switching the switching mechanism from the heating operation state to the cooling operation state. In addition, when a heat exchanger using air as a heat source is adopted as the intermediate cooler and the intermediate cooler is integrated with the heat source side heat exchanger, frost formation may also occur in the intermediate cooler. For this reason, during the reverse cycle defrosting operation, it is conceivable that the refrigerant flows not only through the heat source side heat exchanger but also through the intercooler.

  However, when such a defrosting operation is performed, the refrigerant flowing through the intercooler condenses, and the refrigerant sucked into the compression element at the rear stage becomes wet, so that the wet compression is performed by the compression element at the rear stage. This may cause the compression mechanism to become overloaded.

  An object of the present invention is to provide a refrigerating apparatus having a refrigerant circuit configured to be capable of switching between a cooling operation and a heating operation and performing a multistage compression refrigeration cycle using a refrigerant operating in a supercritical region. The purpose is to suppress the wetness of the refrigerant sucked into the compression element on the rear stage side during the frost operation.

  A refrigeration apparatus according to a first aspect of the present invention is a refrigeration apparatus that uses a refrigerant that operates in a supercritical region, and that compresses the refrigerant, a heat source side heat exchanger that functions as a refrigerant cooler or a heater, and decompresses the refrigerant. An expansion mechanism, a use side heat exchanger that functions as a refrigerant heater or cooler, a switching mechanism, an intermediate cooler, and a rear-stage injection pipe. The compression mechanism has a plurality of compression elements, and is configured to sequentially compress the refrigerant discharged from the compression element on the front stage side among the plurality of compression elements by the compression element on the rear stage side. Here, the “compression mechanism” refers to a compressor in which a plurality of compression elements are integrally incorporated, a compressor in which a single compression element is incorporated, and / or a compressor in which a plurality of compression elements are incorporated. This means a configuration that includes a unit connected. In addition, “sequentially compresses the refrigerant discharged from the compression element on the front stage among the plurality of compression elements with the compression element on the rear stage” is referred to as “compression element on the front stage” and “compression element on the rear stage” It is not only meant to include two compression elements connected in series, but a plurality of compression elements are connected in series, and the relationship between the compression elements is the above-mentioned “previous-side compression element” ”And“ compression element on the rear stage side ”. The switching mechanism includes a cooling operation state in which the refrigerant is circulated in the order of the compression mechanism, the heat source side heat exchanger, the expansion mechanism, and the usage side heat exchanger, and the compression mechanism, the usage side heat exchanger, the expansion mechanism, and the heat source side heat exchanger. This is a mechanism for switching between a heating operation state in which the refrigerant is circulated in order. The heat source side heat exchanger is a heat exchanger using air as a heat source. The intermediate cooler is a heat exchanger using air integrated with the heat source side heat exchanger as a heat source, and an intermediate refrigerant pipe for sucking the refrigerant discharged from the compression element on the front stage side into the compression element on the rear stage side And functions as a refrigerant cooler that is discharged from the compression element on the front stage side and sucked into the compression element on the rear stage side. The rear stage side injection pipe is a refrigerant pipe for branching the refrigerant cooled in the heat source side heat exchanger or the use side heat exchanger and returning it to the rear stage compression element. And this refrigeration apparatus, when performing the reverse cycle defrosting operation for defrosting the heat source side heat exchanger by switching the switching mechanism to the cooling operation state, the heat source side heat exchanger, the intermediate cooler, and the rear stage side injection When the refrigerant flows through the pipe and it is detected that the refrigerant has condensed in the intermediate cooler, the flow rate of the refrigerant returned to the compression element on the rear stage side through the rear stage injection pipe is reduced.

  In this refrigeration system, a heat exchanger using air as a heat source is used as an intermediate cooler, and the intermediate cooler is integrated with a heat source side heat exchanger using air as a heat source. There is a risk of frost formation. For this reason, in this refrigeration apparatus, when performing the reverse cycle defrosting operation in which the heat source side heat exchanger functions as a refrigerant cooler by switching the switching mechanism from the heating operation state to the cooling operation state, the heat source side heat exchanger It is conceivable that the refrigerant flows not only through the intercooler.

  However, when such a defrosting operation is performed, the refrigerant flowing through the intercooler condenses, and the refrigerant sucked into the compression element at the rear stage becomes wet, so that the wet compression is performed by the compression element at the rear stage. This may cause the compression mechanism to become overloaded.

  In view of this, in this refrigeration apparatus, a reverse-stage defrosting operation is performed by providing a rear-stage injection pipe for branching the refrigerant cooled in the heat-source-side heat exchanger or the use-side heat exchanger and returning it to the rear-stage compression element. When the refrigerant flows through the heat source side heat exchanger, the intermediate cooler, and the rear stage side injection pipe when it is detected that the refrigerant has condensed in the intermediate cooler, the refrigerant is returned to the rear stage compression element through the rear stage side injection pipe. By reducing the flow rate of the refrigerant, the degree of wetness of the refrigerant sucked into the compression element on the rear stage side can be suppressed.

  Thereby, in this refrigeration apparatus, when performing the reverse cycle defrosting operation, it is possible to suppress the compression mechanism from being overloaded due to wet compression by the compression element on the rear stage side.

  A refrigeration apparatus according to a second aspect of the present invention is the refrigeration apparatus according to the first aspect of the present invention, wherein the rear stage side injection pipe has a rear stage side injection valve capable of opening control, and the rear stage side injection valve has a reverse cycle. During the defrosting operation, the opening degree is controlled to be small when it is detected that the refrigerant has condensed in the intercooler.

  In this refrigeration apparatus, for example, during reverse cycle defrosting operation, by performing opening control so as to be smaller than the opening of the rear-stage injection valve before detecting that the refrigerant has condensed in the intermediate cooler, It is possible to reliably reduce the flow rate of the refrigerant returning to the downstream compression element through the downstream injection pipe.

  A refrigeration apparatus according to a third aspect of the invention is the refrigeration apparatus according to the first or second aspect of the invention, wherein the refrigerant operating in the supercritical region is carbon dioxide.

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

  In 1st or 3rd invention, when performing a reverse cycle defrost operation, it can suppress that wet compression arises with the compression element of a back | latter stage, and a compression mechanism will be in an overload state.

  In the second aspect of the invention, the flow rate of the refrigerant returning to the compression element on the rear stage side through the rear stage side injection pipe can be reliably reduced.

  Hereinafter, an embodiment of a refrigeration apparatus according to the present invention will be described based on the drawings.

(1) Configuration of Air Conditioner FIG. 1 is a schematic configuration diagram of an air conditioner 1 as an embodiment of a refrigeration apparatus according to the present invention. The air conditioner 1 has a refrigerant circuit 310 configured to be capable of switching between a cooling operation and a heating operation, and uses a refrigerant (here, carbon dioxide) that operates in a supercritical region to perform a two-stage compression refrigeration cycle. It is a device to perform.

  The refrigerant circuit 310 of the air conditioner 1 mainly includes a compression mechanism 2, a switching mechanism 3, a heat source side heat exchanger 4, a bridge circuit 17, a receiver 18, a receiver inlet expansion mechanism 5a, and a receiver outlet expansion mechanism. 5b, a rear-stage injection pipe 19, an economizer heat exchanger 20, a use-side heat exchanger 6, and an intercooler 7.

  In this embodiment, the compression mechanism 2 includes a compressor 21 that compresses the refrigerant in two stages with two compression elements. The compressor 21 has a sealed structure in which a compressor drive motor 21b, a drive shaft 21c, and compression elements 2c and 2d are accommodated in a casing 21a. The compressor drive motor 21b is connected to the drive shaft 21c. The drive shaft 21c is connected to the two compression elements 2c and 2d. That is, in the compressor 21, two compression elements 2c and 2d are connected to a single drive shaft 21c, and the two compression elements 2c and 2d are both rotationally driven by the compressor drive motor 21b. It has a stage compression structure. The compression elements 2c and 2d are positive displacement compression elements such as a rotary type and a scroll type in the present embodiment. The compressor 21 sucks the refrigerant from the suction pipe 2a, compresses the sucked refrigerant by the compression element 2c, discharges the refrigerant to the intermediate refrigerant pipe 8, and discharges the refrigerant discharged to the intermediate refrigerant pipe 8 to the compression element 2d. And the refrigerant is further compressed and then discharged to the discharge pipe 2b. Here, the intermediate refrigerant pipe 8 is a refrigerant pipe for sucking the refrigerant discharged from the compression element 2c connected to the front stage side of the compression element 2c into the compression element 2d connected to the rear stage side of the compression element 2c. is there. The discharge pipe 2b is a refrigerant pipe for sending the refrigerant discharged from the compression mechanism 2 to the switching mechanism 3. The discharge pipe 2b is provided with an oil separation mechanism 41 and a check mechanism 42. The oil separation mechanism 41 is a mechanism that separates the refrigeration oil accompanying the refrigerant discharged from the compression mechanism 2 from the refrigerant and returns it to the suction side of the compression mechanism 2, and is mainly accompanied by the refrigerant discharged from the compression mechanism 2. An oil separator 41 a that separates the refrigeration oil from the refrigerant, and an oil return pipe 41 b that is connected to the oil separator 41 a and returns the refrigeration oil separated from the refrigerant to the suction pipe 2 a of the compression mechanism 2. The oil return pipe 41b is provided with a pressure reducing mechanism 41c for reducing the pressure of the refrigerating machine oil flowing through the oil return pipe 41b. In the present embodiment, a capillary tube is used as the decompression mechanism 41c. The check mechanism 42 is a mechanism for allowing the refrigerant flow from the discharge side of the compression mechanism 2 to the switching mechanism 3 and blocking the refrigerant flow from the switching mechanism 3 to the discharge side of the compression mechanism 2. In this embodiment, a check valve is used.

  Thus, in this embodiment, the compression mechanism 2 has the two compression elements 2c and 2d, and the refrigerant discharged from the compression element on the front stage of these compression elements 2c and 2d is returned to the rear stage side. The compression elements are sequentially compressed by the compression elements.

  The switching mechanism 3 is a mechanism for switching the flow direction of the refrigerant in the refrigerant circuit 310. During the cooling operation, the heat source side heat exchanger 4 is used as a refrigerant cooler compressed by the compression mechanism 2 and used. In order for the side heat exchanger 6 to function as a heater for the refrigerant cooled in the heat source side heat exchanger 4, the discharge side of the compression mechanism 2 and one end of the heat source side heat exchanger 4 are connected and the compressor 21 The suction side and the use side heat exchanger 6 are connected (refer to the solid line of the switching mechanism 3 in FIG. 1, hereinafter, the state of the switching mechanism 3 is referred to as “cooling operation state”). In order for the exchanger 6 to function as a refrigerant cooler to be compressed by the compression mechanism 2 and the heat source side heat exchanger 4 to function as a refrigerant heater cooled in the utilization side heat exchanger 6, Discharge side and use side heat exchanger 6 Can be connected to the suction side of the compression mechanism 2 and one end of the heat source side heat exchanger 4 (see the broken line of the switching mechanism 3 in FIG. "Heating operation state"). In the present embodiment, the switching mechanism 3 is a four-way switching valve connected to the suction side of the compression mechanism 2, the discharge side of the compression mechanism 2, the heat source side heat exchanger 4, and the use side heat exchanger 6. The switching mechanism 3 is not limited to a four-way switching valve, and is configured to have a function of switching the refrigerant flow direction as described above, for example, by combining a plurality of electromagnetic valves. There may be.

  As described above, when the switching mechanism 3 focuses only on the compression mechanism 2, the heat source side heat exchanger 4, the expansion mechanisms 5 a and 5 b, and the use side heat exchanger 6 constituting the refrigerant circuit 310, the compression mechanism 2, the heat source side The cooling operation state in which the refrigerant is circulated in the order of the heat exchanger 4, the expansion mechanisms 5a and 5b, and the use side heat exchanger 6, the compression mechanism 2, the use side heat exchanger 6, the expansion mechanisms 5a and 5b, and the heat source side heat exchanger The heating operation state in which the refrigerant is circulated in the order of 4 can be switched.

  The heat source side heat exchanger 4 is a heat exchanger that functions as a refrigerant cooler or a heater. One end of the heat source side heat exchanger 4 is connected to the switching mechanism 3, and the other end is connected to the receiver inlet expansion mechanism 5 a via the bridge circuit 17 and the economizer heat exchanger 20. The heat source side heat exchanger 4 is a heat exchanger that uses air as a heat source (that is, a cooling source or a heating source), and a fin-and-tube heat exchanger is used in this embodiment. The air as the heat source is supplied to the heat source side heat exchanger 4 by the heat source side fan 40. The heat source side fan 40 is driven by a fan drive motor 40a.

  The bridge circuit 17 is provided between the heat source side heat exchanger 4 and the use side heat exchanger 6, and is connected to a receiver inlet pipe 18 a connected to the inlet of the receiver 18 and an outlet of the receiver 18. It is connected to the receiver outlet pipe 18b. In the present embodiment, the bridge circuit 17 has four check valves 17a, 17b, 17c, and 17d. The inlet check valve 17a is a check valve that only allows the refrigerant to flow from the heat source side heat exchanger 4 to the receiver inlet pipe 18a. The inlet check valve 17b is a check valve that allows only the refrigerant to flow from the use side heat exchanger 6 to the receiver inlet pipe 18a. That is, the inlet check valves 17a and 17b have a function of circulating the refrigerant from one of the heat source side heat exchanger 4 and the use side heat exchanger 6 to the receiver inlet pipe 18a. The outlet check valve 17 c is a check valve that allows only the refrigerant to flow from the receiver outlet pipe 18 b to the use side heat exchanger 6. The outlet check valve 17d is a check valve that allows only the refrigerant to flow from the receiver outlet pipe 18b to the heat source side heat exchanger 4. That is, the outlet check valves 17c and 17d have a function of circulating the refrigerant from the receiver outlet pipe 18b to the other of the heat source side heat exchanger 4 and the use side heat exchanger 6.

  The receiver inlet expansion mechanism 5a is a mechanism that depressurizes the refrigerant provided in the receiver inlet pipe 18a. In this embodiment, an electric expansion valve is used. One end of the receiver inlet expansion mechanism 5 a is connected to the heat source side heat exchanger 4 via the economizer heat exchanger 20 and the bridge circuit 17, and the other end is connected to the receiver 18. In the present embodiment, the receiver inlet expansion mechanism 5a reduces the pressure of the high-pressure refrigerant cooled in the heat source side heat exchanger 4 before sending it to the use side heat exchanger 6 during the cooling operation, and uses it during the heating operation. The high-pressure refrigerant cooled in the side heat exchanger 6 is decompressed before being sent to the heat source side heat exchanger 4.

  The receiver 18 is a container provided to temporarily store the refrigerant that has been depressurized by the receiver inlet expansion mechanism 5a, and its inlet is connected to the receiver inlet pipe 18a, and its outlet is the receiver outlet pipe 18b. It is connected to the. The receiver 18 has a suction return pipe 18c that can extract the refrigerant from the receiver 18 and return it to the suction pipe 2a of the compression mechanism 2 (that is, the suction side of the compression element 2c on the front stage side of the compression mechanism 2). It is connected. The suction return pipe 18c is provided with a suction return on-off valve 18d. The suction return on-off valve 18d is an electromagnetic valve in the present embodiment.

  The receiver outlet expansion mechanism 5b is a mechanism that depressurizes the refrigerant provided in the receiver outlet pipe 18b, and an electric expansion valve is used in the present embodiment. One end of the receiver outlet expansion mechanism 5 b is connected to the receiver 18, and the other end is connected to the use side heat exchanger 6 via the bridge circuit 17. In the present embodiment, the receiver outlet expansion mechanism 5b further reduces the pressure of the refrigerant decompressed by the receiver inlet expansion mechanism 5a to the low pressure before sending it to the use side heat exchanger 6 during the cooling operation, and during the heating operation. The refrigerant depressurized by the receiver inlet expansion mechanism 5a is further depressurized until it reaches a low pressure before being sent to the heat source side heat exchanger 4.

  The use side heat exchanger 6 is a heat exchanger that functions as a refrigerant heater or cooler. One end of the use side heat exchanger 6 is connected to the receiver inlet expansion mechanism 5 a via the bridge circuit 17, and the other end is connected to the switching mechanism 3. Although not shown here, the use side heat exchanger 6 is supplied with water or air as a heating source or a cooling source for exchanging heat with the refrigerant flowing through the use side heat exchanger 6. .

  Thus, when the switching mechanism 3 is in the cooling operation state by the bridge circuit 17, the receiver 18, the receiver inlet pipe 18a, and the receiver outlet pipe 18b, the high-pressure refrigerant cooled in the heat source side heat exchanger 4 is , Use side heat through the inlet check valve 17a of the bridge circuit 17, the receiver inlet expansion mechanism 5a of the receiver inlet pipe 18a, the receiver 18, the receiver outlet expansion mechanism 5b of the receiver outlet pipe 18b, and the outlet check valve 17c of the bridge circuit 17. It can be sent to the exchanger 6. Further, when the switching mechanism 3 is in the heating operation state, the high-pressure refrigerant cooled in the use side heat exchanger 6 causes the inlet check valve 17b of the bridge circuit 17 and the receiver inlet expansion mechanism of the receiver inlet pipe 18a. 5 a, the receiver 18, the receiver outlet expansion mechanism 5 b of the receiver outlet pipe 18 b, and the outlet check valve 17 d of the bridge circuit 17 can be sent to the heat source side heat exchanger 6.

  The rear stage side injection pipe 19 has a function of branching the refrigerant cooled in the heat source side heat exchanger 4 or the use side heat exchanger 6 and returning it to the compression element 2 d on the rear stage side of the compression mechanism 2. In the present embodiment, the rear-stage injection pipe 19 is provided to branch the refrigerant flowing through the receiver inlet pipe 18a and return it to the suction side of the rear-stage compression element 2d. More specifically, the rear-stage injection pipe 19 is positioned on the upstream side of the receiver inlet expansion mechanism 5a of the receiver inlet pipe 18a (that is, when the switching mechanism 3 is in the cooling operation state, the heat source side heat exchanger 4 and the receiver inlet expansion mechanism 5a, and when the switching mechanism 3 is in the heating operation state, the refrigerant is branched from the use side heat exchanger 6 and the receiver inlet expansion mechanism 5a) The refrigerant pipe 8 is provided so as to return to a position downstream of the intermediate cooler 7. The rear stage side injection pipe 19 is provided with a rear stage side injection valve 19a capable of opening degree control. The rear-stage injection valve 19a is an electric expansion valve in the present embodiment.

  The economizer heat exchanger 20 includes a refrigerant cooled in the heat source side heat exchanger 4 or the use side heat exchanger 6 and a refrigerant flowing through the rear side injection pipe 19 (more specifically, in the vicinity of the intermediate pressure in the rear side injection valve 19a. It is a heat exchanger which performs heat exchange with the refrigerant after being depressurized up to. In the present embodiment, the economizer heat exchanger 20 is positioned on the upstream side of the receiver inlet expansion mechanism 5a of the receiver inlet pipe 18a (that is, when the switching mechanism 3 is in the cooling operation state, the heat source side heat exchanger 4 And the receiver inlet expansion mechanism 5a, and when the switching mechanism 3 is in the heating operation state, the refrigerant flowing between the use side heat exchanger 6 and the receiver inlet expansion mechanism 5a) and the rear side injection pipe 19 is provided so as to perform heat exchange with the refrigerant flowing through 19, and has a flow path through which both refrigerants face each other. In the present embodiment, the economizer heat exchanger 20 is provided on the upstream side of the rear-stage injection pipe 19 of the receiver inlet pipe 18a. For this reason, the refrigerant cooled in the heat source side heat exchanger 4 or the use side heat exchanger 6 is branched to the rear-stage side injection pipe 19 before heat exchange is performed in the economizer heat exchanger 20 in the receiver inlet pipe 18a. Thereafter, in the economizer heat exchanger 20, heat exchange is performed with the refrigerant flowing through the rear-stage injection pipe 19.

  The intermediate cooler 7 is a heat exchanger that is provided in the intermediate refrigerant pipe 8 and functions as a refrigerant cooler that is discharged from the preceding compression element 2c and sucked into the compression element 2d. The intercooler 7 is a heat exchanger that uses air as a heat source (that is, a cooling source), and in this embodiment, a fin-and-tube heat exchanger is used. The intermediate cooler 7 is integrated with the heat source side heat exchanger 4. More specifically, the intercooler 7 is integrated by sharing heat transfer fins with the heat source side heat exchanger 4. In the present embodiment, air as a heat source is supplied by a heat source side fan 40 that supplies air to the heat source side heat exchanger 4. That is, the heat source side fan 40 supplies air as a heat source to both the heat source side heat exchanger 4 and the intercooler 7.

  An intermediate cooler bypass pipe 9 is connected to the intermediate refrigerant pipe 8 so as to bypass the intermediate cooler 7. The intermediate cooler bypass pipe 9 is a refrigerant pipe that limits the flow rate of the refrigerant flowing through the intermediate cooler 7. The intermediate cooler bypass pipe 9 is provided with an intermediate cooler bypass opening / closing valve 11. The intermediate cooler bypass on-off valve 11 is an electromagnetic valve in the present embodiment. The intermediate cooler bypass on-off valve 11 is basically closed when the switching mechanism 3 is in the cooling operation state, except for a case where a temporary operation such as a defrosting operation described later is performed. Control is performed when 3 is in a heating operation state. In other words, the intercooler bypass opening / closing valve 11 is controlled to be closed when the cooling operation is performed and to be opened when the heating operation is performed.

  Further, the intermediate refrigerant pipe 8 has a position on the intermediate cooler 7 side from the connection with the intermediate cooler bypass pipe 9 (that is, an intermediate from the connection with the intermediate cooler bypass pipe 9 on the inlet side of the intermediate cooler 7). A cooler on / off valve 12 is provided on a portion of the cooler 7 up to the connection portion on the outlet side. The cooler on / off valve 12 is a mechanism that limits the flow rate of the refrigerant flowing through the intermediate cooler 7. The cooler on / off valve 12 is an electromagnetic valve in the present embodiment. The cooler opening / closing valve 12 is basically opened when the switching mechanism 3 is in the cooling operation state, except for a case where a temporary operation such as a defrosting operation described later is performed, and the switching mechanism 3 is opened. Control is performed to close during the heating operation state. That is, the cooler on / off valve 12 is controlled to be opened when the cooling operation is performed and closed when the heating operation is performed. In the present embodiment, the cooler on / off valve 12 is provided at a position on the inlet side of the intermediate cooler 7, but may be provided at a position on the outlet side of the intermediate cooler 7.

  The intermediate refrigerant pipe 8 allows the refrigerant to flow from the discharge side of the front-stage compression element 2c to the suction side of the rear-stage compression element 2d, and from the discharge side of the rear-stage compression element 2d to the front stage. A check mechanism 15 for blocking the flow of the refrigerant to the compression element 2c on the side is provided. The check mechanism 15 is a check valve in the present embodiment. In the present embodiment, the check mechanism 15 is provided in a portion from the outlet side of the intermediate cooler 7 of the intermediate refrigerant pipe 8 to the connection portion with the intermediate cooler bypass pipe 9.

  Furthermore, the air conditioning apparatus 1 is provided with various sensors. Specifically, the heat source side heat exchanger 4 is provided with a heat source side heat exchange temperature sensor 51 that detects the temperature of the refrigerant flowing through the heat source side heat exchanger 4. At the outlet of the intermediate cooler 7, an intermediate cooler outlet temperature sensor 52 that detects the temperature of the refrigerant at the outlet of the intermediate cooler 7 is provided. The air conditioner 1 is provided with an air temperature sensor 53 that detects the temperature of air as a heat source of the heat source side heat exchanger 4 and the intermediate cooler 7. The intermediate refrigerant pipe 8 or the compression mechanism 2 is provided with an intermediate pressure sensor 54 that detects the pressure of the refrigerant flowing through the intermediate refrigerant pipe 8. An economizer outlet temperature sensor 55 that detects the refrigerant temperature at the outlet of the economizer heat exchanger 20 on the rear injection pipe 19 side is provided at the outlet on the rear injection pipe 19 side of the economizer heat exchanger 20. Although not shown here, the air conditioner 1 includes a compression mechanism 2, a switching mechanism 3, expansion mechanisms 5 a and 5 b, a rear stage side injection valve 19 a, a heat source side fan 40, an intercooler bypass on-off valve 11, and a cooler on / off state. It has a control part which controls operation of each part which constitutes air harmony device 1 such as valve 12.

(2) Operation | movement of an air conditioning apparatus Next, operation | movement of the air conditioning apparatus 1 of this embodiment is demonstrated using FIGS. Here, FIG. 2 is a pressure-enthalpy diagram illustrating a refrigeration cycle during cooling operation, FIG. 3 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation, and FIG. FIG. 5 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the heating operation, FIG. 5 is a temperature-entropy diagram illustrating the refrigeration cycle during the heating operation, and FIG. 6 is a flowchart of the defrosting operation. FIG. 7 is a diagram showing the refrigerant flow in the air conditioner 1 at the start of the defrosting operation. FIG. 8 is a diagram illustrating the flow of the refrigerant in the air conditioner 1 when the refrigerant is condensed in the intercooler. FIG. 9 is a diagram showing the flow of the refrigerant in the air conditioner after the defrosting of the intercooler is completed. Note that operation control in the following cooling operation, heating operation, and defrosting operation is performed by the above-described control unit (not shown). In the following description, “high pressure” means high pressure in the refrigeration cycle (that is, pressure at points D, E, and H in FIGS. 2 and 3 and pressure at points D, F, and H in FIGS. 4 and 5). “Low pressure” means low pressure in the refrigeration cycle (that is, pressure at points A, F, and F ′ in FIGS. 2 and 3 and pressure at points A, E, and E ′ in FIGS. 4 and 5). “Intermediate pressure” means the intermediate pressure in the refrigeration cycle (that is, the pressure at points B1, C1, G, J, and K in FIGS. 2 to 5).

<Cooling operation>
During the cooling operation, the switching mechanism 3 is in a cooling operation state indicated by a solid line in FIG. The opening degree of the receiver inlet expansion mechanism 5a and the receiver outlet expansion mechanism 5b is adjusted. Since the switching mechanism 3 is in the cooling operation state, the cooler on / off valve 12 is opened, and the intermediate cooler bypass on / off valve 11 of the intermediate cooler bypass pipe 9 is closed, so that the intermediate cooler 7 is cooled. It is assumed that it functions as a container. Further, the opening degree of the rear injection valve 19a is also adjusted. More specifically, in this embodiment, the opening degree of the rear-stage injection valve 19a is adjusted so that the superheat degree of the refrigerant at the outlet on the rear-stage injection pipe 19 side of the economizer heat exchanger 20 becomes a target value. So-called superheat control is performed. In the present embodiment, the degree of superheat of the refrigerant at the outlet of the economizer heat exchanger 20 on the rear stage injection pipe 19 side is detected by the economizer outlet temperature sensor 55 by converting the intermediate pressure detected by the intermediate pressure sensor 54 into a saturation temperature. It is obtained by subtracting the saturation temperature value of this refrigerant from the refrigerant temperature to be obtained. Although not adopted in the present embodiment, a temperature sensor is provided at the inlet of the rear-stage injection pipe 19 side of the economizer heat exchanger 20, and the refrigerant temperature detected by this temperature sensor is detected by the economizer outlet temperature sensor 55. The degree of superheat of the refrigerant at the outlet of the economizer heat exchanger 20 on the rear injection pipe 19 side may be obtained by subtracting from the refrigerant temperature.

  When the compression mechanism 2 is driven in the state of the refrigerant circuit 310, low-pressure refrigerant (see point A in FIGS. 1 to 3) is sucked into the compression mechanism 2 from the suction pipe 2a, and first, the intermediate pressure is compressed by the compression element 2c. And then discharged to the intermediate refrigerant pipe 8 (see point B1 in FIGS. 1 to 3). The intermediate-pressure refrigerant discharged from the preceding compression element 2c is cooled by exchanging heat with air as a cooling source in the intermediate cooler 7 (see point C1 in FIGS. 1 to 3). The refrigerant cooled in the intermediate cooler 7 is further cooled by joining with the refrigerant (see point K in FIGS. 1 to 3) returned from the rear-stage injection pipe 19 to the rear-stage compression mechanism 2d (see FIG. 1 to FIG. 3). 1 to point G in FIG. 3). Next, the intermediate pressure refrigerant combined with the refrigerant returning from the rear-stage-side injection pipe 19 is sucked into the compression element 2d connected to the rear-stage side of the compression element 2c and further compressed, and then is compressed from the compression mechanism 2 to the discharge pipe 2b. The ink is discharged (see point D in FIGS. 1 to 3). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is compressed to a pressure exceeding the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 2) by the two-stage compression operation by the compression elements 2c and 2d. Has been. The high-pressure refrigerant discharged from the compression mechanism 2 is sent to the heat source side heat exchanger 4 functioning as a refrigerant cooler via the switching mechanism 3 to exchange heat with air as the cooling source. To cool (see point E in FIGS. 1-3). The high-pressure refrigerant cooled in the heat source side heat exchanger 4 flows into the receiver inlet pipe 18 a through the inlet check valve 17 a of the bridge circuit 17, and a part thereof is branched to the rear-stage injection pipe 19. And the refrigerant | coolant which flows through the back | latter stage side injection pipe | tube 19 is sent to the economizer heat exchanger 20 after depressurizing to the intermediate pressure vicinity in the back | latter stage side injection valve 19a (refer the point J of FIGS. 1-3). Further, the refrigerant flowing through the receiver inlet pipe 18a after being branched to the rear-stage injection pipe 19 flows into the economizer heat exchanger 20, and is cooled by exchanging heat with the refrigerant flowing through the rear-stage injection pipe 19 (FIG. 1 to point H in FIG. 3). On the other hand, the refrigerant flowing through the rear-stage injection pipe 19 is heated by exchanging heat with the refrigerant flowing through the receiver inlet pipe 18a (see point K in FIGS. 1 to 3), and in the intermediate cooler 7 as described above. It will join the cooled refrigerant. And the high pressure refrigerant | coolant cooled in the economizer heat exchanger 20 is pressure-reduced by the receiver inlet expansion mechanism 5a to saturation pressure vicinity, and is temporarily stored in the receiver 18 (refer the point I of FIGS. 1-3). Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is reduced in pressure by the receiver outlet expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 17c of the bridge circuit 17 is supplied. To the utilization side heat exchanger 6 that functions as a refrigerant heater (see point F in FIGS. 1 to 3). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use-side heat exchanger 6 is heated by performing heat exchange with water or air as a heating source and evaporates (FIGS. 1 to 1). (See point A in 3). Then, the low-pressure refrigerant heated in the use side heat exchanger 6 is again sucked into the compression mechanism 2 via the switching mechanism 3. In this way, the cooling operation is performed.

  As described above, in the air conditioner 1, the intermediate cooler 7 is provided in the intermediate refrigerant pipe 8 for allowing the refrigerant discharged from the compression element 2c to be sucked into the compression element 2d, and the switching mechanism 3 is in the cooling operation state. In operation, the cooler on / off valve 12 is opened, and the intercooler bypass on / off valve 11 of the intercooler bypass pipe 9 is closed, so that the intercooler 7 functions as a cooler. Compared with the case where the container 7 is not provided, the temperature of the refrigerant sucked into the compression element 2d on the rear stage side of the compression element 2c is lowered (see points B1 and C1 in FIG. 3), and the refrigerant discharged from the compression element 2d The temperature will also decrease. For this reason, in this air conditioning apparatus 1, compared with the case where the intermediate cooler 7 is not provided in the heat source side heat exchanger 4 that functions as a high-pressure refrigerant cooler, water and air as the cooling source, and the refrigerant The temperature difference can be reduced and the heat dissipation loss can be reduced, so that the operation efficiency can be improved.

  Moreover, in the configuration of the present embodiment, the rear stage side injection pipe 19 is provided so that the refrigerant sent from the heat source side heat exchanger 4 to the expansion mechanisms 5a and 5b is branched and returned to the rear stage side compression element 2d. Further, the temperature of the refrigerant sucked into the compression element 2d on the rear stage side can be further reduced without performing heat radiation to the outside like the intermediate cooler 7 (see points C1 and G in FIG. 3). As a result, the temperature of the refrigerant discharged from the compression mechanism 2 can be further reduced, and the heat dissipation loss can be further reduced as compared with the case where the rear-stage injection pipe 19 is not provided, so that the operating efficiency can be further improved. .

  In the configuration of the present embodiment, an economizer heat exchanger 20 is further provided that performs heat exchange between the refrigerant sent from the heat source side heat exchanger 4 to the expansion mechanisms 5 a and 5 b and the refrigerant flowing through the rear-stage injection pipe 19. Therefore, the refrigerant sent from the heat source side heat exchanger 4 to the expansion mechanisms 5a and 5b can be cooled by the refrigerant flowing through the rear side injection pipe 19 (see points E and H in FIGS. 2 and 3), and intermediate cooling. The cooling capacity per unit flow rate of the refrigerant in the use-side heat exchanger 6 can be increased as compared with the case where the condenser 7, the rear-stage injection pipe 19, and the economizer heat exchanger 20 are not provided.

<Heating operation>
During the heating operation, the switching mechanism 3 is in a heating operation state indicated by a broken line in FIG. The opening degree of the receiver inlet expansion mechanism 5a and the receiver outlet expansion mechanism 5b is adjusted. Since the switching mechanism 3 is in a heating operation state, the cooler on / off valve 12 is closed, and the intermediate cooler bypass on / off valve 11 of the intermediate cooler bypass pipe 9 is opened, so that the intermediate cooler 7 is cooled. It is assumed that it does not function as a vessel. Furthermore, the opening degree of the rear-stage injection valve 19a is also adjusted by superheat degree control similar to that during cooling operation.

  When the compression mechanism 2 is driven in the state of the refrigerant circuit 310, low-pressure refrigerant (see point A in FIGS. 1, 4, and 5) is sucked into the compression mechanism 2 from the suction pipe 2a, and first, the compression element 2c After being compressed to an intermediate pressure, the refrigerant is discharged into the intermediate refrigerant pipe 8 (see point B1 in FIGS. 1, 4 and 5). Unlike the cooling operation, the intermediate-pressure refrigerant discharged from the preceding-stage compression element 2c passes through the intermediate cooler bypass pipe 9 without passing through the intermediate cooler 7 (that is, without being cooled). Passes (see point C1 in FIGS. 1, 4 and 5) and merges with the refrigerant (see point K in FIGS. 1, 4 and 5) returned from the rear-stage injection pipe 19 to the rear-stage compression mechanism 2d. (Refer to point G in FIGS. 1, 4 and 5). Next, the intermediate pressure refrigerant combined with the refrigerant returning from the rear-stage-side injection pipe 19 is sucked into the compression element 2d connected to the rear-stage side of the compression element 2c and further compressed, and then is compressed from the compression mechanism 2 to the discharge pipe 2b. The ink is discharged (see point D in FIGS. 1, 4 and 5). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is subjected to the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 4) by the two-stage compression operation by the compression elements 2c and 2d as in the cooling operation. ) Compressed to a pressure exceeding The high-pressure refrigerant discharged from the compression mechanism 2 is sent to the use-side heat exchanger 6 that functions as a refrigerant cooler via the switching mechanism 3, and water or air as a cooling source and heat It is exchanged and cooled (see point F in FIGS. 1, 4 and 5). The high-pressure refrigerant cooled in the use side heat exchanger 6 flows into the receiver inlet pipe 18 a through the inlet check valve 17 b of the bridge circuit 17, and a part thereof is branched to the rear-stage injection pipe 19. And the refrigerant | coolant which flows through the back | latter stage side injection pipe 19 is pressure-reduced to intermediate pressure vicinity in the back | latter stage side injection valve 19a, Then, it sends to the economizer heat exchanger 20 (refer FIG.1, FIG.4, FIG.5 point J). Further, the refrigerant flowing through the receiver inlet pipe 18a after being branched to the rear-stage injection pipe 19 flows into the economizer heat exchanger 20, and is cooled by exchanging heat with the refrigerant flowing through the rear-stage injection pipe 19 (FIG. 1, point H in FIG. 4 and FIG. 5). On the other hand, the refrigerant flowing through the rear side injection pipe 19 is heated by exchanging heat with the refrigerant flowing through the receiver inlet pipe 18a (see point K in FIGS. 1, 4 and 5), and as described above, The intermediate pressure refrigerant discharged from the compression element 2c is joined. Then, the high-pressure refrigerant cooled in the economizer heat exchanger 20 is depressurized to near the saturation pressure by the receiver inlet expansion mechanism 5a and temporarily stored in the receiver 18 (point I in FIGS. 1, 4, and 5). reference). Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is reduced in pressure by the receiver outlet expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 17d of the bridge circuit 17 is used. To the heat source side heat exchanger 4 functioning as a refrigerant heater (see point E in FIGS. 1, 4 and 5). Then, the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated and exchanged with air as a heating source to evaporate (FIGS. 1, 4 and 4). (See point A in FIG. 5). The low-pressure refrigerant heated in the heat source side heat exchanger 4 is again sucked into the compression mechanism 2 via the switching mechanism 3. In this way, the heating operation is performed.

  As described above, in the air conditioner 1, the intermediate cooler 7 is provided in the intermediate refrigerant pipe 8 for allowing the refrigerant discharged from the compression element 2c to be sucked into the compression element 2d, and the heating with the switching mechanism 3 in the heating operation state. In operation, the cooler on / off valve 12 is closed, and the intermediate cooler bypass on / off valve 11 of the intermediate cooler bypass pipe 9 is opened so that the intermediate cooler 7 does not function as a cooler. Compared to the case where only the cooler 7 is provided or the case where the intermediate cooler 7 is made to function as a cooler as in the above-described cooling operation, a decrease in the temperature of the refrigerant discharged from the compression mechanism 2 is suppressed. For this reason, in this air conditioning apparatus 1, compared with the case where only the intermediate cooler 7 is provided or the case where the intermediate cooler 7 functions as a cooler as in the above-described cooling operation, heat radiation to the outside is suppressed, It is possible to suppress a decrease in the temperature of the refrigerant supplied to the use-side heat exchanger 6 that functions as a refrigerant cooler, to suppress a decrease in heating capacity, and to prevent a decrease in operating efficiency.

  Moreover, in the configuration of this embodiment, the rear-stage injection pipe 19 is provided so that the refrigerant sent from the use-side heat exchanger 6 to the expansion mechanisms 5a and 5b is branched and returned to the rear-stage compression element 2d. Thus, the temperature of the refrigerant discharged from the compression mechanism 2 is lowered, and thereby the heating capacity per unit flow rate of the refrigerant in the use side heat exchanger 6 is reduced, but the refrigerant discharged from the compression element 2d on the rear stage side is reduced. Since the flow rate increases, the heating capacity in the use-side heat exchanger 6 is ensured, and the operation efficiency can be improved.

  In the configuration of the present embodiment, an economizer heat exchanger 20 that further performs heat exchange between the refrigerant sent from the use side heat exchanger 6 to the expansion mechanisms 5 a and 5 b and the refrigerant flowing through the rear-stage injection pipe 19 is further provided. Therefore, the refrigerant flowing through the rear-stage injection pipe 19 can be heated by the refrigerant sent from the use-side heat exchanger 6 to the expansion mechanisms 5a and 5b (see points J and K in FIGS. 4 and 5). Compared with the case where the injection pipe 19 and the economizer heat exchanger 20 are not provided, the flow rate of the refrigerant discharged from the compression element 2d on the rear stage side can be increased.

  Further, as an advantage common to the cooling operation and the heating operation, in the configuration of the present embodiment, as the economizer heat exchanger 20, the refrigerant sent from the heat source side heat exchanger 4 or the use side heat exchanger 6 to the expansion mechanisms 5a and 5b. Since the heat exchanger having a flow path that flows so that the refrigerant flowing through the rear-stage-side injection pipe 19 is opposed to the heat-source-side heat exchanger 4 or the utilization-side heat exchanger 6 in the economizer heat exchanger 20 is adopted. The temperature difference between the refrigerant sent to the expansion mechanisms 5a and 5b and the refrigerant flowing through the rear-stage injection pipe 19 can be reduced, and high heat exchange efficiency can be obtained. In the configuration of the present embodiment, the refrigerant sent from the heat source side heat exchanger 4 or the use side heat exchanger 6 to the expansion mechanisms 5a and 5b is heat exchanged in the economizer heat exchanger 20 before the heat source side heat exchanger 20 is heated. 4 or the downstream side injection pipe 19 is provided so as to branch the refrigerant sent from the use side heat exchanger 6 to the expansion mechanisms 5a and 5b. Therefore, in the economizer heat exchanger 20, the refrigerant and heat flowing through the downstream side injection pipe 19 are provided. The flow rate of the refrigerant sent to the expansion mechanisms 5a and 5b from the heat source side heat exchanger 4 or the use side heat exchanger 6 that performs exchange can be reduced, and the amount of exchange heat in the economizer heat exchanger 20 can be reduced. The size of the economizer heat exchanger 20 can be reduced.

<Defrosting operation>
In this air conditioner 1, when heating operation is performed under a condition where the temperature of the air as the heat source of the heat source side heat exchanger 4 is low, frost forms on the heat source side heat exchanger 4 that functions as a refrigerant heater, Thereby, there exists a possibility that the heat-transfer performance of the heat-source side heat exchanger 4 may fall. For this reason, it is necessary to defrost the heat source side heat exchanger 4.

  Hereinafter, the defrosting operation of the present embodiment will be described in detail with reference to FIGS.

  First, in step S1, it is determined whether or not frost formation has occurred in the heat source side heat exchanger 4 during the heating operation. This determination is performed based on the temperature of the refrigerant flowing through the heat source side heat exchanger 4 detected by the heat source side heat exchange temperature sensor 51 and the accumulated time of the heating operation. For example, when it is detected that the temperature of the refrigerant in the heat source side heat exchanger 4 detected by the heat source side heat exchange temperature sensor 51 is equal to or lower than a predetermined temperature corresponding to a condition for causing frost formation, or integration of heating operation When the time elapses over a predetermined time, it is determined that frost formation has occurred in the heat source side heat exchanger 4, and when the temperature condition or time condition is not satisfied, the heat source side heat exchanger 4 is determined. It is determined that no frost formation has occurred. Here, since the predetermined temperature and the predetermined time depend on the temperature of air as a heat source, it is preferable to set the predetermined temperature and the predetermined time as a function of the air temperature detected by the air temperature sensor 53. Further, when temperature sensors are provided at the inlet and outlet of the heat source side heat exchanger 4, the temperature is detected by these temperature sensors instead of the refrigerant temperature detected by the heat source side heat exchange temperature sensor 51. You may use the temperature of a refrigerant | coolant for determination of temperature conditions. And when it determines with the frost formation having arisen in the heat source side heat exchanger 4 in step S1, it transfers to the process of step S2.

  Next, in step S2, the defrosting operation is started. This defrosting operation is a reverse cycle defrosting operation in which the heat source side heat exchanger 4 functions as a refrigerant cooler by switching the switching mechanism 3 from the heating operation state (that is, the heating operation) to the cooling operation state. In addition, in the present embodiment, a heat exchanger using air as a heat source is adopted as the intermediate cooler 7 and the intermediate cooler 7 is integrated with the heat source side heat exchanger 4. Therefore, it is necessary to defrost the intermediate cooler 7 by flowing the refrigerant not only to the heat source side heat exchanger 4 but also to the intermediate cooler 7. Therefore, at the start of the defrosting operation, the heat source side heat exchanger is switched by switching the switching mechanism 3 from the heating operation state (that is, the heating operation) to the cooling operation state (that is, the cooling operation) as in the above-described cooling operation. 4 is operated as a refrigerant cooler, the cooler on / off valve 12 is opened, and the intermediate cooler bypass on / off valve 11 is closed to operate the intermediate cooler 7 as a cooler (in FIG. 7). (See arrows for refrigerant flow).

  On the other hand, when the reverse cycle defrosting operation is employed, the use side heat exchanger 6 is allowed to function as a refrigerant heater although the use side heat exchanger 6 is desired to function as a refrigerant cooler. There is a problem that a temperature drop occurs on the use side. Further, since the reverse cycle defrosting operation is a cooling operation under a condition where the temperature of air as a heat source is low, the low pressure of the refrigeration cycle is reduced, and the flow rate of the refrigerant sucked from the compression element 2c on the front stage is reduced. End up. If it does so, since the flow volume of the refrigerant | coolant which circulates through the refrigerant circuit 310 will reduce and it will become impossible to ensure the flow volume of the refrigerant | coolant which flows through the heat source side heat exchanger 4, the problem that defrost of the heat source side heat exchanger 4 takes time also arises.

  Therefore, in this embodiment, the cooler on / off valve 12 is opened, and the intermediate cooler bypass on / off valve 11 is closed to operate the intermediate cooler 7 as a cooler. The reverse cycle defrosting operation is performed while returning the refrigerant sent from the heat source side heat exchanger 4 to the utilization side heat exchanger 6 to the compression element 2d on the rear stage side (the flow of the refrigerant in FIG. 7). (See the arrows shown.) Moreover, in the present embodiment, the opening degree control is performed so that the opening degree of the rear-stage injection valve 19a is larger than the opening degree of the rear-stage injection valve 19a during the heating operation immediately before the reverse cycle defrosting operation is performed. ing. For example, the opening degree of the rear injection valve 19a in the fully closed state is set to 0% and the opening degree in the fully opened state is set to 100%, and the rear injection valve 19a is controlled in an opening range of 50% or less during the heating operation. If so, the rear injection valve 19a in step S2 is controlled to increase the opening degree to about 70%, and in step S3, until it is determined that the defrosting of the intercooler 7 has been completed, The opening is fixed.

  Thereby, defrosting of the intercooler 7 is performed, and the flow rate of the refrigerant flowing through the use-side heat exchanger 6 is reduced by increasing the flow rate of the refrigerant flowing through the post-stage side injection pipe 19, and the compression element 2d on the post-stage side Thus, the reverse cycle defrosting operation capable of securing the flow rate of the refrigerant flowing through the heat source side heat exchanger 4 by increasing the flow rate of the refrigerant to be processed in the above is realized. Moreover, in the present embodiment, since the opening degree control is performed so as to be larger than the opening degree of the rear-stage injection valve 19a in the heating operation immediately before the reverse cycle defrosting operation is performed, the flow flows through the use-side heat exchanger 6. The flow rate of the refrigerant flowing through the heat source side heat exchanger 4 can be further increased while further reducing the flow rate of the refrigerant.

  Until the defrosting of the intermediate cooler 7 is completed, although temporarily, the refrigerant flowing through the intermediate cooler 7 is condensed, and the refrigerant sucked into the compression element 2d on the rear stage side is moistened. As a result, wet compression occurs in the subsequent compression element 2d, and the compression mechanism 2 may be overloaded.

  Therefore, in this embodiment, when it is detected in step S7 that the refrigerant has condensed in the intermediate cooler 7, the flow rate of the refrigerant returned to the compression element 2d on the rear stage side through the rear injection pipe 19 in step S8 is determined. Inhalation wetness prevention control to reduce is performed.

  Here, whether or not the refrigerant has condensed in the intermediate cooler 7 in step S7 is determined based on the degree of superheat of the refrigerant at the outlet of the intermediate cooler 7. For example, when it is detected that the degree of superheat of the refrigerant at the outlet of the intermediate cooler 7 is zero or less (that is, a saturated state), it is determined that the refrigerant is condensed in the intermediate cooler 7, and this When the superheat condition is not satisfied, it is determined that the refrigerant is not condensed in the intercooler 7. In this embodiment, the degree of superheat of the refrigerant at the outlet of the intermediate cooler 7 is detected by the intermediate pressure sensor 54 from the temperature of the refrigerant at the outlet of the intermediate cooler 7 detected by the intermediate cooler outlet temperature sensor 52. It is obtained by subtracting the saturation temperature obtained by converting the pressure of the refrigerant flowing through the intermediate refrigerant pipe 8. In Step S8, the flow rate of the refrigerant returned to the compression element 2d on the rear stage side through the rear stage injection pipe 19 is reduced by controlling the opening of the rear stage injection valve 19a to be small. In the present embodiment, the opening degree control is performed so that the opening degree (for example, close to full close) is smaller than the opening degree (in this case, about 70%) before detecting that the refrigerant has condensed in the intercooler 7. (Refer to the arrow indicating the flow of the refrigerant in FIG. 8).

  Thus, even when the refrigerant flowing through the intermediate cooler 7 is condensed before the defrosting of the intermediate cooler 7 is completed, the refrigerant returned to the compression element 2d on the rear stage side through the rear stage injection pipe 19 While the flow rate is temporarily reduced and defrosting of the intercooler 7 is continued, the degree of wetness of the refrigerant sucked into the downstream compression element 2d is suppressed, and wet compression occurs in the downstream compression element 2d. It is possible to suppress the compression mechanism 2 from being overloaded.

  Next, in step S3, it is determined whether or not the defrosting of the intercooler 7 is completed. Here, as described above, whether or not the defrosting of the intercooler 7 has been completed is determined so that the intercooler 7 does not function as a cooler by the intercooler bypass pipe 9 during the heating operation. Therefore, the amount of frost formation in the intermediate cooler 7 is small, and the defrosting of the intermediate cooler 7 is completed earlier than the heat source side heat exchanger 4. This determination is made based on the outlet refrigerant temperature of the intermediate cooler 7. For example, when it is detected that the outlet refrigerant temperature of the intermediate cooler 7 detected by the intermediate cooler outlet temperature sensor 52 is equal to or higher than a predetermined temperature, it is determined that the defrosting of the intermediate cooler 7 has been completed. When the temperature condition is not satisfied, it is determined that the defrosting of the intercooler 7 is not completed. Such a determination based on the outlet refrigerant temperature of the intermediate cooler 7 can reliably detect that the defrosting of the intermediate cooler 7 has been completed. If it is determined in step S3 that the defrosting of the intercooler 7 has been completed, the process proceeds to step S4.

  Next, in step S <b> 4, the operation for defrosting the intercooler 7 and the heat source side heat exchanger 4 is shifted to the operation for defrosting only the heat source side heat exchanger 4. The operation transition after the defrosting of the intermediate cooler 7 is performed is that if the refrigerant continues to flow through the intermediate cooler 7 even after the defrosting of the intermediate cooler 7 is completed, the intermediate cooler 7 Heat is radiated to the outside, and the temperature of the refrigerant sucked into the compression element 2d on the rear stage side is lowered. As a result, the temperature of the refrigerant discharged from the compression mechanism 2 is lowered, and the heat source side heat exchanger This is to prevent such a problem from occurring because the problem that the defrosting capacity of No. 4 is reduced occurs. And by the operation transition in this step S4, the cooler on / off valve 12 is closed and the intermediate cooler bypass on / off valve 11 is opened while continuing the defrosting of the heat source side heat exchanger 4 by the reverse cycle defrosting operation. Thus, an operation is performed so that the intercooler 7 does not function as a cooler (see the arrows indicating the refrigerant flow in FIG. 9). As a result, heat is not radiated from the intermediate cooler 7 to the outside, so that the temperature of the refrigerant sucked into the compression element 2d on the rear stage side is suppressed from being lowered. As a result, the refrigerant is discharged from the compression mechanism 2. It becomes possible to suppress a decrease in the defrosting capability of the heat source side heat exchanger 4 by suppressing the temperature of the refrigerant to be lowered.

  However, after detecting that the defrosting of the intercooler 7 is completed, the intercooler bypass pipe 9 is used (that is, the cooler on / off valve 12 is closed and the intercooler bypass on / off valve 11 is opened). ) If the refrigerant is prevented from flowing into the intermediate cooler 7, the temperature of the refrigerant sucked into the rear-stage compression element 2d increases rapidly, so that the refrigerant sucked into the rear-stage compression element 2d The density decreases, and the flow rate of the refrigerant sucked into the compression element 2d on the rear stage side tends to decrease. For this reason, the balance of the effect | action which raises the defrosting capability by preventing the thermal radiation to the exterior from the intermediate cooler 7, and the effect | action which reduces the defrosting capability by reducing the flow volume of the refrigerant | coolant which flows through the heat-source side heat exchanger 4. Therefore, there is a possibility that the effect of suppressing the defrosting ability of the heat source side heat exchanger 4 from being lowered cannot be obtained sufficiently.

  Therefore, in step S4, the intermediate cooler bypass pipe 9 is used to prevent the refrigerant from flowing into the intermediate cooler 7 and to control the opening of the rear-stage injection valve 19a to increase the intermediate cooling. In addition to preventing heat radiation from the heat exchanger 7 to the outside, the refrigerant sent from the heat source side heat exchanger 4 to the use side heat exchanger 6 is returned to the compression element 2d on the rear stage side, and the flow rate of the refrigerant flowing through the heat source side heat exchanger 4 is increased. I try to let them. Here, the opening degree of the rear injection valve 19a is larger than the opening degree of the rear injection valve 19a in the heating operation immediately before performing the reverse cycle defrosting operation in step S2 (here, about 70%). However, in step S4, control is performed to open to a larger opening (for example, close to full opening).

  Next, in step S5, it is determined whether or not the defrosting of the heat source side heat exchanger 4 is completed. This determination is made based on the temperature of the refrigerant flowing through the heat source side heat exchanger 4 detected by the heat source side heat exchange temperature sensor 51 and the operating time of the defrosting operation. For example, when it is detected that the temperature of the refrigerant in the heat source side heat exchanger 4 detected by the heat source side heat exchanger temperature sensor 51 is equal to or higher than a temperature corresponding to a condition that no frost formation is present, or a defrosting operation When the predetermined time has elapsed, it is determined that the defrosting of the heat source side heat exchanger 4 has been completed, and when the temperature condition or time condition is not met, the heat source side heat exchanger 4 is removed. It is determined that frost has not been completed. Here, in the case where temperature sensors are provided at the inlet and outlet of the heat source side heat exchanger 4, the temperature is detected by these temperature sensors instead of the refrigerant temperature detected by the heat source side heat exchange temperature sensor 51. The temperature of the refrigerant may be used for determining the temperature condition. And in step S5, when it determines with the defrosting of the heat source side heat exchanger 4 having been completed, it transfers to the process of step S6, complete | finishes a defrost operation, and restarts a heating operation again. Processing is performed. More specifically, the process etc. which switch the switching mechanism 3 from a cooling operation state to a heating operation state (namely, heating operation) are performed.

  As described above, in the air conditioner 1, the heat source side heat exchanger 4 functions as a refrigerant cooler to perform the defrosting operation for defrosting the heat source side heat exchanger 4, thereby performing heat source side heat exchange. The refrigerant is caused to flow through the cooler 4 and the intercooler 7 and after the defrosting of the intercooler 7 is detected, the intercooler bypass pipe 9 is used to prevent the refrigerant from flowing into the intercooler 7. Is. Thereby, in the air conditioning apparatus 1, when performing the defrosting operation, the defrosting of the intermediate cooler 7 is also performed, and a decrease in the defrosting capability caused by heat radiation from the intermediate cooler 7 to the outside is performed. It can suppress, and it can contribute to shortening defrosting time.

  Moreover, in the present embodiment, when the reverse cycle defrosting operation is performed to defrost the heat source side heat exchanger 4 by switching the switching mechanism 3 to the cooling operation state, the rear side injection pipe 19 is used to perform the heat source side. The refrigerant sent from the heat exchanger 4 to the use side heat exchanger 6 is returned to the subsequent compression element 2d, and after detecting that the defrosting of the intermediate cooler 7 is completed, the intermediate cooler bypass pipe 9 to prevent the refrigerant from flowing into the intercooler 7, and to control the opening of the rear-stage injection valve 19a to be large, thereby preventing heat radiation from the intercooler 7 to the outside, and The refrigerant sent from the heat source side heat exchanger 4 to the use side heat exchanger 6 is returned to the compression element 2d on the rear stage side, the flow rate of the refrigerant flowing through the heat source side heat exchanger 4 is increased, and the heat source side heat exchanger 4 I will suppress the decrease in defrosting capacity It has to. Moreover, the flow rate of the refrigerant flowing through the use side heat exchanger 6 can be reduced.

  Thereby, in this embodiment, the fall of the defrost capability at the time of performing reverse cycle defrost operation can be suppressed. Moreover, the temperature fall by the side of utilization at the time of performing a reverse cycle defrost operation can be suppressed.

  Further, in the present embodiment, when the rear stage side injection pipe 19 is in the cooling operation state of the switching mechanism 3, the heat source side heat exchanger 4 and the expansion mechanism (here, the high pressure cooled in the heat source side heat exchanger 4). Since the refrigerant is provided so as to be branched from the receiver inlet expansion mechanism 5a) that depressurizes the refrigerant before it is sent to the use-side heat exchanger 6, it is compressed from the pressure before being decompressed by the expansion mechanism. Since the differential pressure up to the pressure on the suction side of the element 2d can be used, the flow rate of the refrigerant returned to the compression element 2d on the rear stage side can be easily increased, and the flow rate of the refrigerant flowing through the use side heat exchanger 6 is further reduced. The flow rate of the refrigerant flowing through the heat source side heat exchanger 4 can be further increased.

  Further, in the present embodiment, when the switching mechanism 3 is in the cooling operation state, the heat source side heat exchanger 4 expands the expansion mechanism (here, the high pressure refrigerant cooled in the heat source side heat exchanger 4 is used side heat exchange). Since it further includes an economizer heat exchanger 20 that performs heat exchange between the refrigerant sent to the receiver inlet expansion mechanism 5a) that is depressurized before being sent to the vessel 6 and the refrigerant flowing through the latter-stage injection pipe 19, the latter-stage injection pipe The refrigerant flowing through 19 is heated by exchanging heat with the refrigerant sent from the heat source side heat exchanger 4 to the expansion mechanism, and the risk that the refrigerant sucked into the compression element 2d on the rear stage side becomes wet can be reduced. Thereby, it becomes easy to increase the flow rate of the refrigerant returned to the compression element 2d on the rear stage side, and further increase the flow rate of the refrigerant flowing through the heat source side heat exchanger 4 while further reducing the flow rate of the refrigerant flowing through the use side heat exchanger 6. Can do.

(3) Modification 1
In the above-described embodiment, the refrigerant discharged from the front-stage compression element of the two compression elements 2c and 2d is sequentially compressed by the rear-stage compression element by the single compressor 21 having the single-shaft two-stage compression structure. The two-stage compression type compression mechanism 2 is configured. For example, as shown in FIG. 10, two compressors having a single-stage compression structure in which one compression element is rotationally driven by one compressor drive motor. The compression mechanism 2 having a two-stage compression structure may be configured by connecting the units in series.

  Here, the compression mechanism 2 includes a compressor 22 and a compressor 23. The compressor 22 has a sealed structure in which a compressor drive motor 22b, a drive shaft 22c, and a compression element 2c are accommodated in a casing 22a. The compressor drive motor 22b is connected to the drive shaft 22c, and the drive shaft 22c is connected to the compression element 2c. The compressor 23 has a sealed structure in which a compressor drive motor 23b, a drive shaft 23c, and a compression element 2d are accommodated in a casing 23a. The compressor drive motor 23b is connected to the drive shaft 23c, and the drive shaft 23c is connected to the compression element 2d. The compression mechanism 2 sucks the refrigerant from the suction pipe 2a, and compresses the sucked refrigerant by the compression element 2c, and then discharges it to the intermediate refrigerant pipe 8, similarly to the above-described embodiment and its modifications. The refrigerant discharged to the refrigerant pipe 8 is sucked into the compression element 2d to further compress the refrigerant, and then discharged to the discharge pipe 2b.

  Further, instead of the two-stage compression type compression mechanism 2, for example, as shown in FIG. 11, a refrigerant circuit 410 that employs a compression mechanism 202 having two-stage compression type compression mechanisms 203 and 204 may be used.

  In the present modification, the first compression mechanism 203 includes the compressor 29 that compresses the refrigerant in two stages with the two compression elements 203c and 203d, and the first suction mechanism branched from the suction mother pipe 202a of the compression mechanism 202. The branch pipe 203 a is connected to the first discharge branch pipe 203 b that joins the discharge mother pipe 202 b of the compression mechanism 202. In the present modification, the second compression mechanism 204 includes the compressor 30 that compresses the refrigerant in two stages by the two compression elements 204c and 204d, and the second suction mechanism branched from the suction mother pipe 202a of the compression mechanism 202. The branch pipe 204 a is connected to the second discharge branch pipe 204 b that joins the discharge mother pipe 202 b of the compression mechanism 202. Since the compressors 29 and 30 have the same configuration as the compressor 21 in the above-described embodiment, the reference numerals indicating the respective parts except the compression elements 203c, 203d, 204c, and 204d are replaced with the 29th and 30th units, respectively. The description is omitted here. Then, the compressor 29 sucks the refrigerant from the first suction branch pipe 203a, and after discharging the sucked refrigerant by the compression element 203c, discharges it to the first inlet side intermediate branch pipe 81 constituting the intermediate refrigerant pipe 8. The refrigerant discharged to the first inlet-side intermediate branch pipe 81 is sucked into the compression element 203d through the intermediate mother pipe 82 and the first outlet-side intermediate branch pipe 83 constituting the intermediate refrigerant pipe 8, and the refrigerant is further compressed. It is configured to discharge to one discharge branch pipe 203b. The compressor 30 sucks the refrigerant from the first suction branch pipe 204a, compresses the sucked refrigerant by the compression element 204c, and then discharges the refrigerant to the second inlet side intermediate branch pipe 84 constituting the intermediate refrigerant pipe 8. The refrigerant discharged to the two inlet-side intermediate branch pipes 84 is sucked into the compression element 204d through the intermediate mother pipe 82 and the second outlet-side intermediate branch pipe 85 constituting the intermediate refrigerant pipe 8 to further compress the refrigerant, and then the second discharge. It is comprised so that it may discharge to the branch pipe 204b. In the present modification, the intermediate refrigerant pipe 8 is configured so that the refrigerant discharged from the compression elements 203c and 204c connected to the upstream side of the compression elements 203d and 204d is compressed by the compression element 203d connected to the downstream side of the compression elements 203c and 204c. , 204 d is a refrigerant pipe to be sucked, and mainly a first inlet side intermediate branch pipe 81 connected to the discharge side of the compression element 203 c on the front stage side of the first compression mechanism 203, and a front stage of the second compression mechanism 204. A second inlet side intermediate branch pipe 84 connected to the discharge side of the compression element 204c on the side, an intermediate mother pipe 82 where both the inlet side intermediate branch pipes 81 and 84 merge, and a first branch branched from the intermediate mother pipe 82. A first outlet-side intermediate branch pipe 83 connected to the suction side of the compression element 203d on the rear stage side of the compression mechanism 203, and a suction part of the compression element 204d on the rear stage side of the second compression mechanism 204 branched from the intermediate mother pipe 82 And a second outlet-side intermediate branch tube 85 connected to the. The discharge mother pipe 202b is a refrigerant pipe for sending the refrigerant discharged from the compression mechanism 202 to the switching mechanism 3. The first discharge branch pipe 203b connected to the discharge mother pipe 202b has a first oil separation. A mechanism 241 and a first check mechanism 242 are provided, and a second oil separation mechanism 243 and a second check mechanism 244 are provided in the second discharge branch pipe 204b connected to the discharge mother pipe 202b. ing. The first oil separation mechanism 241 is a mechanism that separates refrigeration oil accompanying the refrigerant discharged from the first compression mechanism 203 from the refrigerant and returns it to the suction side of the compression mechanism 202, and mainly discharges from the first compression mechanism 203. The first oil separator 241a that separates the refrigeration oil accompanying the refrigerant to be cooled from the refrigerant, and the first oil separator that is connected to the first oil separator 241a and returns the refrigeration oil separated from the refrigerant to the suction side of the compression mechanism 202 And an oil return pipe 241b. The second oil separation mechanism 243 is a mechanism that separates the refrigeration oil accompanying the refrigerant discharged from the second compression mechanism 204 from the refrigerant and returns it to the suction side of the compression mechanism 202, and is mainly discharged from the second compression mechanism 204. A second oil separator 243a that separates the refrigeration oil accompanying the refrigerant to be cooled from the refrigerant, and a second oil separator that is connected to the second oil separator 243a and returns the refrigeration oil separated from the refrigerant to the suction side of the compression mechanism 202. And an oil return pipe 243b. In this modification, the first oil return pipe 241b is connected to the second suction branch pipe 204a, and the second oil return pipe 243c is connected to the first suction branch pipe 203a. For this reason, the refrigerant discharged from the first compression mechanism 203 is caused by a deviation between the amount of refrigeration oil accumulated in the first compression mechanism 203 and the amount of refrigeration oil accumulated in the second compression mechanism 204. Even if there is a bias between the amount of refrigerating machine oil accompanying and the amount of refrigerating machine oil accompanying the refrigerant discharged from the second compression mechanism 204, the amount of refrigerating machine oil in the compression mechanisms 203 and 204 is A large amount of refrigeration oil returns to the smaller one, so that the bias between the amount of refrigeration oil accumulated in the first compression mechanism 203 and the amount of refrigeration oil accumulated in the second compression mechanism 204 is eliminated. It has become. Further, in this modification, the first suction branch pipe 203a has a portion between the junction with the second oil return pipe 243b and the junction with the suction mother pipe 202a at the junction with the suction mother pipe 202a. The second suction branch pipe 204a is configured such that the portion between the junction with the first oil return pipe 241b and the junction with the suction mother pipe 202a is the suction mother pipe. It is comprised so that it may become a downward slope toward the confluence | merging part with 202a. For this reason, even if one of the compression mechanisms 203 and 204 is stopped, the refrigerating machine oil returned from the oil return pipe corresponding to the operating compression mechanism to the suction branch pipe corresponding to the stopped compression mechanism is It will return to the suction | inhalation mother pipe 202a, and it becomes difficult to produce the oil shortage of the compression mechanism in driving | operation. The oil return pipes 241b and 243b are provided with pressure reducing mechanisms 241c and 243c for reducing the pressure of the refrigerating machine oil flowing through the oil return pipes 241b and 243b. The check mechanisms 242 and 244 allow the refrigerant flow from the discharge side of the compression mechanisms 203 and 204 to the switching mechanism 3, and block the refrigerant flow from the switching mechanism 3 to the discharge side of the compression mechanisms 203 and 204. It is a mechanism to do.

  As described above, the compression mechanism 202 includes the two compression elements 203c and 203d in the present modification, and the refrigerant discharged from the compression element on the front stage of the compression elements 203c and 203d is used as the compression element on the rear stage side. And the first compression mechanism 203 configured to sequentially compress the first and second compression elements 204c and 204d, and the refrigerant discharged from the compression element on the front side of the compression elements 204c and 204d is supplied to the rear side. A second compression mechanism 204 configured to sequentially compress with a compression element is connected in parallel.

  Further, the first inlet side intermediate branch pipe 81 constituting the intermediate refrigerant pipe 8 allows the refrigerant to flow from the discharge side of the compression element 203c on the front stage side of the first compression mechanism 203 to the intermediate mother pipe 82 side, In addition, a non-return mechanism 81 a for blocking the flow of the refrigerant from the intermediate mother pipe 82 side to the discharge side of the upstream compression element 203 c is provided, and the second inlet side intermediate branch constituting the intermediate refrigerant pipe 8 is provided. The pipe 84 allows the refrigerant to flow from the discharge side of the compression element 204c on the front stage side of the second compression mechanism 203 to the intermediate mother pipe 82 side, and the compression element 204c on the front stage side from the intermediate mother pipe 82 side. A check mechanism 84a is provided for blocking the flow of the refrigerant to the discharge side. In this modification, check valves are used as the check mechanisms 81a and 84a. For this reason, even if one of the compression mechanisms 203 and 204 is stopped, the refrigerant discharged from the compression element on the front stage side of the operating compression mechanism passes through the intermediate refrigerant pipe 8 to the front stage of the stopped compression mechanism. Therefore, the refrigerant discharged from the compression element on the upstream side of the operating compression mechanism passes through the compression element on the upstream side of the compression mechanism that is stopped, so that the compression mechanism 202 is discharged. Thus, the refrigerant oil of the stopped compression mechanism does not flow out to the suction side, so that the shortage of the refrigerating machine oil when starting the stopped compression mechanism is less likely to occur. In addition, when the priority of operation is provided between the compression mechanisms 203 and 204 (for example, when the first compression mechanism 203 is a compression mechanism that operates preferentially), it corresponds to the above-described stopped compression mechanism. Since this is limited to the second compression mechanism 204, only the check mechanism 84a corresponding to the second compression mechanism 204 may be provided in this case.

  Further, as described above, when the first compression mechanism 203 is a compression mechanism that operates preferentially, the intermediate refrigerant pipe 8 is provided in common to the compression mechanisms 203 and 204, and therefore the first operating mechanism is in operation. The refrigerant discharged from the upstream compression element 203c corresponding to the compression mechanism 203 passes through the second outlet side intermediate branch pipe 85 of the intermediate refrigerant pipe 8 and is sucked into the downstream compression element 204d of the stopped second compression mechanism 204. As a result, the refrigerant discharged from the compression element 203c on the front stage side of the first compression mechanism 203 during operation passes through the compression element 204d on the rear stage side of the second compression mechanism 204 that is stopped. There is a possibility that the refrigerating machine oil of the second compression mechanism 204 that has stopped after coming out to the discharge side will flow out, resulting in a shortage of refrigerating machine oil when starting the second compression mechanism 204 that has been stopped. Therefore, in the present modification, an opening / closing valve 85a is provided in the second outlet-side intermediate branch pipe 85, and when the second compression mechanism 204 is stopped, the opening / closing valve 85a causes the second outlet-side intermediate branch pipe 85 to The refrigerant flow is cut off. Thereby, the refrigerant discharged from the compression element 203c on the front stage side of the first compression mechanism 203 in operation passes through the second outlet side intermediate branch pipe 85 of the intermediate refrigerant pipe 8, and the rear stage side of the stopped second compression mechanism 204. Therefore, the refrigerant discharged from the compression element 203c on the front stage side of the operating first compression mechanism 203 becomes the compression element on the rear stage side of the stopped second compression mechanism 204. It is no longer that the refrigerating machine oil of the stopped second compression mechanism 204 flows out into the discharge side of the compression mechanism 202 through the inside of 204d, and thereby the refrigerating machine oil when starting the stopped second compression mechanism 204 is stopped. The shortage of is even less likely to occur. In this modification, an electromagnetic valve is used as the on-off valve 85a.

  When the first compression mechanism 203 is a compression mechanism that operates preferentially, the second compression mechanism 204 is started following the start of the first compression mechanism 203. At this time, the intermediate refrigerant pipe 8 is provided in common to the compression mechanisms 203 and 204, the pressure on the discharge side of the compression element 203c on the front stage side of the second compression mechanism 204 and the pressure on the suction side of the compression element 203d on the rear stage side are Starting from a state in which the pressure on the suction side of the compression element 203c and the pressure on the discharge side of the compression element 203d on the rear stage side are higher, it is difficult to start the second compression mechanism 204 stably. Therefore, in this modification, an activation bypass pipe 86 is provided to connect the discharge side of the compression element 204c on the front stage side of the second compression mechanism 204 and the suction side of the compression element 204d on the rear stage side. When the on-off valve 86a is provided and the second compression mechanism 204 is stopped, the on-off valve 86a blocks the flow of the refrigerant in the startup bypass pipe 86, and the on-off valve 85a provides the second outlet-side intermediate branch pipe. The refrigerant flow in 85 is interrupted, and when the second compression mechanism 204 is activated, the on-off valve 86a allows the refrigerant to flow into the activation bypass pipe 86, thereby allowing the second compression mechanism 204 to flow. The starting bypass pipe 8 does not join the refrigerant discharged from the first-stage compression element 204c with the refrigerant discharged from the first-stage compression element 204c of the first compression mechanism 203. When the operation state of the compression mechanism 202 is stabilized (for example, when the suction pressure, the discharge pressure, and the intermediate pressure of the compression mechanism 202 are stabilized), the on-off valve 85a The refrigerant can flow into the second outlet-side intermediate branch pipe 85, and the flow of the refrigerant in the startup bypass pipe 86 is blocked by the on-off valve 86a so that the normal cooling operation can be performed. It has become. In this modification, one end of the activation bypass pipe 86 is connected between the on-off valve 85a of the second outlet side intermediate branch pipe 85 and the suction side of the compression element 204d on the rear stage side of the second compression mechanism 204. The other end is connected between the discharge side of the compression element 204c on the front stage side of the second compression mechanism 204 and the check mechanism 84a of the second inlet side intermediate branch pipe 84, and activates the second compression mechanism 204. At this time, the first compression mechanism 203 can be hardly affected by the intermediate pressure portion. In this modification, an electromagnetic valve is used as the on-off valve 86a.

  Further, the operation of the air conditioner 1 of the present modified example during the cooling operation, the heating operation, and the defrosting operation is slightly different in circuit configuration around the compression mechanism 202 by the compression mechanism 202 provided in place of the compression mechanism 2. Except for the change due to the complexity, the operation is basically the same as the operation in the above-described embodiment (FIGS. 1 to 9 and related descriptions), and thus the description thereof is omitted here.

  And also in the structure of this modification 1, the effect similar to the above-mentioned embodiment can be acquired.

  In addition, although detailed explanation is omitted here, the two-stage compression type compression mechanism 2 and the two-stage compression type compression mechanisms 203 and 204 are replaced with a multistage compression type such as a three-stage compression type. Or a parallel multi-stage compression type compression mechanism in which three or more multi-stage compression type compression mechanisms are connected in parallel may be adopted. Similar effects can be obtained. Further, in the air conditioner 1 of the present modification, the flow direction of the refrigerant with respect to the receiver inlet expansion mechanism 5a, the receiver outlet expansion mechanism 5b, the receiver 18, the rear-stage injection pipe 19, or the economizer heat exchanger 20 is set to the cooling operation and The bridge circuit 17 is also used from the viewpoint of keeping it constant regardless of the heating operation. For example, the post-stage injection pipe 19 or the economizer heat exchanger 20 is used only for either the cooling operation or the heating operation. The refrigerant flow direction with respect to the receiver inlet expansion mechanism 5a, the receiver outlet expansion mechanism 5b, the receiver 18, the rear-stage injection pipe 19 or the economizer heat exchanger 20 is made constant regardless of the cooling operation and the heating operation. If not necessary, the bridge circuit 17 may be omitted.

(4) Modification 2
In the refrigerant circuit 310 (see FIG. 1) and the refrigerant circuit 410 (see FIG. 11) in the above-described embodiment and its modifications, a single use-side heat exchanger 6 is connected. While connecting the side heat exchanger 6, you may comprise so that these utilization side heat exchangers 6 can be started / stopped separately.

  For example, as shown in FIG. 12, in the refrigerant circuit 310 (see FIG. 1) in which the two-stage compression type compression mechanism 2 is adopted, two usage-side heat exchangers 6 are connected to each usage-side heat. The use side expansion mechanism 5c is provided corresponding to the bridge circuit 17 side end of the exchanger 6, the receiver outlet expansion mechanism 5b provided in the receiver outlet pipe 18b is deleted, and the outlet check valve of the bridge circuit 17 is further removed. Instead of 17d, a refrigerant circuit 510 provided with a bridge outlet expansion mechanism 5d is used, or as shown in FIG. 13, a refrigerant circuit 410 employing a parallel two-stage compression type compression mechanism 202 (see FIG. 11). ), Two use side heat exchangers 6 are connected, and a use side expansion mechanism 5c is provided corresponding to the end of each use side heat exchanger 6 on the bridge circuit 17 side. The receiver outlet expansion mechanism 5b that has been kicked is removed, further, in place of the return valve 17d of the bridge circuit 17 may be a refrigerant circuit 610 in which the bridge outlet expansion mechanism 5d is provided.

  In the configuration of this modification, the bridge outlet expansion mechanism 5d is fully closed during the cooling operation, and the use side instead of the receiver outlet expansion mechanism 5b in the above-described embodiment and the modification thereof. The point that the expansion mechanism 5c further depressurizes the refrigerant depressurized by the receiver inlet expansion mechanism 5a until it reaches a low pressure before sending it to the use-side heat exchanger 6 is that the cooling operation in the above-described embodiment and its modification example is performed. Although different from the operation at the time and the defrosting operation, the other operations are the operations at the time of the cooling operation and the defrosting operation in the above-described embodiment and the modified example (FIGS. 1 to 3, 6 to 9 and FIG. The related description) is basically the same. Further, during heating operation, the degree of opening of the use-side expansion mechanism 5c is adjusted to control the flow rate of the refrigerant flowing through each use-side heat exchanger 6, and the receiver in the above-described embodiment and its modifications. Instead of the outlet expansion mechanism 5b, the bridge outlet expansion mechanism 5d performs an operation of further reducing the pressure of the refrigerant decompressed by the receiver inlet expansion mechanism 5a until it reaches a low pressure before being sent to the heat source side heat exchanger 4. Although the operation is different from the operation during the heating operation in the embodiment and the modification thereof, the other operations are the operations during the heating operation in the embodiment and the modification described above (FIGS. 1, 4, 5, and related descriptions). ) Is basically the same.

  And also in the structure of this modification, the effect similar to the above-mentioned embodiment and its modification can be obtained.

  In addition, although detailed explanation is omitted here, a multistage compression mechanism such as a three-stage compression type is adopted instead of the two-stage compression type compression mechanism 2, 203, 204. Also good.

(5) Other Embodiments Although the embodiments of the present invention and the modifications thereof have been described with reference to the drawings, the specific configuration is not limited to these embodiments and the modifications thereof. Changes can be made without departing from the scope of the invention.

  For example, in the above-described embodiment and its modification, water or brine is used as a heating source or a cooling source for performing heat exchange with the refrigerant flowing in the use-side heat exchanger 6, and heat exchange is performed in the use-side heat exchanger 6. The present invention may be applied to a so-called chiller type air conditioner provided with a secondary heat exchanger for exchanging heat between the water or brine and indoor air.

  Further, even in another type of refrigeration apparatus of the above-described chiller type air conditioner, the refrigerant circuit configured to be able to switch between the cooling operation and the heating operation has a refrigerant circuit that operates in the supercritical region. The present invention is applicable if it is used as a multistage compression refrigeration cycle.

  Further, the refrigerant operating in the supercritical region is not limited to carbon dioxide, and ethylene, ethane, nitrogen oxide, or the like may be used.

  If the present invention is used, a refrigerating apparatus having a refrigerant circuit configured to be able to switch between a cooling operation and a heating operation and performing a multistage compression refrigeration cycle using a refrigerant operating in a supercritical region, the reverse cycle It becomes possible to suppress the degree of wetting of the refrigerant sucked into the subsequent compression element during the defrosting operation.

It is a schematic block diagram of the air conditioning apparatus as one Embodiment of the freezing apparatus concerning this invention. It is the pressure-enthalpy diagram in which the refrigerating cycle at the time of air_conditionaing | cooling operation was illustrated. FIG. 3 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation. It is the pressure-enthalpy diagram in which the refrigerating cycle at the time of heating operation was illustrated. It is the temperature-entropy diagram in which the refrigerating cycle at the time of heating operation was illustrated. It is a flowchart of a defrost operation. It is a figure which shows the flow of the refrigerant | coolant in an air conditioning apparatus at the time of a defrost operation start. It is a figure which shows the flow of the refrigerant | coolant in an air conditioning apparatus when a refrigerant | coolant condenses in an intercooler. It is a figure which shows the flow of the refrigerant | coolant in an air conditioning apparatus after defrosting of an intercooler is completed. It is a schematic block diagram of the air conditioning apparatus concerning the modification 1. It is a schematic block diagram of the air conditioning apparatus concerning the modification 1. It is a schematic block diagram of the air conditioning apparatus concerning the modification 2. It is a schematic block diagram of the air conditioning apparatus concerning the modification 2.

Explanation of symbols

1 Air conditioning equipment (refrigeration equipment)
2,202 Compression mechanism 3 Switching mechanism 4 Heat source side heat exchanger 5a, 5b, 5c, 5d Expansion mechanism 6 Use side heat exchanger 7 Intermediate cooler 19 Rear stage side injection pipe 19a Rear stage side injection valve

Claims (3)

A refrigeration system using a refrigerant operating in a supercritical region,
A compression mechanism (2, 202) having a plurality of compression elements and configured to sequentially compress the refrigerant discharged from the front-stage compression elements of the plurality of compression elements by the rear-stage compression elements. When,
A heat exchanger using air as a heat source, the heat source side heat exchanger functioning as a refrigerant cooler or heater (4);
An expansion mechanism (5a, 5b, 5c, 5d) for depressurizing the refrigerant;
A use side heat exchanger (6) that functions as a refrigerant heater or cooler;
A cooling operation state in which refrigerant is circulated in the order of the compression mechanism, the heat source side heat exchanger, the expansion mechanism, and the use side heat exchanger, the compression mechanism, the use side heat exchanger, the expansion mechanism, and the heat source side A switching mechanism (3) for switching between a heating operation state in which the refrigerant is circulated in the order of the heat exchanger;
An intermediate refrigerant pipe (8) that uses air integrated with the heat source side heat exchanger as a heat source, and sucks the refrigerant discharged from the front-stage compression element into the rear-stage compression element. An intermediate cooler (7) that functions as a refrigerant cooler that is discharged from the former-stage compression element and sucked into the latter-stage compression element;
A rear-stage injection pipe (19) for branching the refrigerant cooled in the heat source-side heat exchanger or the use-side heat exchanger and returning it to the rear-stage compression element;
When performing a reverse cycle defrosting operation in which the heat source side heat exchanger is defrosted by switching the switching mechanism to the cooling operation state, the heat source side heat exchanger, the intermediate cooler, and the rear stage side injection pipe And when the refrigerant is detected to be condensed in the intermediate cooler, the flow rate of the refrigerant returned to the rear-stage compression element through the rear-stage injection pipe is reduced.
Refrigeration equipment (1). The latter-stage injection pipe (19) has a latter-stage injection valve (19a) capable of opening degree control,
The latter-stage injection valve is controlled to reduce the opening when detecting that the refrigerant has condensed in the intermediate cooler during the reverse cycle defrosting operation.
The refrigeration apparatus (1) according to claim 1.   The refrigerating apparatus (1) according to claim 1 or 2, wherein the refrigerant operating in the supercritical region is carbon dioxide.

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