JP2009270777A - Refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the wet state of a refrigerant sucked to a rear stage side compression element of a compression part which has already started when starting other compression part in the state where the compression part has already started, in a refrigerating device having a refrigerant circuit in which a plurality of compressors having front stage side compression elements and rear stage side compression elements are interconnected in parallel and which enables intermediate pressure injection and performing a multi-stage compression type refrigeration cycle. <P>SOLUTION: An air conditioner 1 includes a two-stage compression type compression mechanism 102 in which a first compression part 103 capable of varying operation capacity and a second compression part 104 are interconnected in parallel and with a first rear stage side injection pipe 18c. In the air conditioner 1, in starting the second compression part 104 with the first compression part 103 started, when the operation capacity of the first compression part 103 is lowered prior to the start of the second compression part 104, an opening of a first rear stage side injection on-off valve 18d of the first rear stage side injection pipe 18c is reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a refrigeration apparatus, in particular, a refrigerant circuit in which a plurality of compressors having a front-stage compression element and a rear-stage compression element are connected in parallel and capable of intermediate pressure injection, and operates in a supercritical region. The present invention relates to a refrigeration apparatus that performs a multistage compression refrigeration cycle using a refrigerant.

Conventionally, as one of refrigeration apparatuses having a refrigerant circuit capable of intermediate pressure injection and performing a multistage compression refrigeration cycle using a refrigerant operating in a supercritical region, There is an air conditioner that has a refrigerant circuit capable of pressure injection 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, an outdoor heat exchanger, an indoor heat exchanger, and a refrigerant that has radiated heat in the outdoor heat exchanger or the indoor heat exchanger. And a rear-stage injection pipe for returning a part thereof to the rear-stage compression element. Here, the compressor sucks the low-pressure refrigerant in the refrigeration cycle and compresses it to the intermediate pressure in the refrigeration cycle, and the latter stage sucks the intermediate-pressure refrigerant in the refrigeration cycle and compresses it to the high pressure in the refrigeration cycle. Side compression elements.
JP 2007-232263 A

  In the air conditioner described above, a part of the refrigerant radiated in the outdoor heat exchanger or the indoor heat exchanger after being discharged from the rear stage compression element of the compressor is passed through the rear stage side injection pipe and the front stage side compression element and the rear stage. By returning to the intermediate refrigerant pipe connecting the side compression element, intermediate pressure injection is performed to merge with the intermediate pressure refrigerant in the refrigeration cycle discharged from the front stage compression element of the compressor and sucked into the rear stage compression element, While reducing the temperature of the refrigerant discharged from the rear side compression element, the power consumption of the compressor is reduced, and the operation efficiency is improved.

  In such an air conditioner, a plurality of compressors having a front-stage compression element and a rear-stage compression element are connected in parallel, and one of the plurality of compressors is a first compressor that can vary the operating capacity, By combining the change in the operating capacity of the compressor and the change in the number of operating other compressors, the operating capacity of the entire plurality of compressors can be varied. In such a configuration, when the other compressor is started in the state where the first compressor is started, an operation of decreasing the operating capacity of the first compressor is performed prior to starting the other compressor.

  At this time, since the flow rate of the refrigerant discharged from the front-stage compression element of the first compressor is reduced, the refrigerant returned from the rear-stage injection pipe to the intermediate refrigerant pipe is compared with the flow rate of the refrigerant flowing through the intermediate refrigerant pipe. There is a risk that the refrigerant flowed into the relatively high flow rate may cause the refrigerant sucked into the rear-stage compression element of the first compressor to be temporarily moistened, thereby reducing the reliability of the apparatus. is there.

  An object of the present invention is to provide a refrigerant that has a refrigerant circuit in which a plurality of compression parts each having a front-stage compression element and a rear-stage compression element are connected in parallel and that can perform intermediate pressure injection, and that operates in a supercritical region. In a refrigeration apparatus that uses a multistage compression refrigeration cycle, when the other compression unit is activated in a state where the compression unit that is already activated exists, the latter stage compression element of the compression unit that is already activated This is to prevent the refrigerant sucked in from getting wet.

  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 includes a compression mechanism, an intermediate refrigerant tube, a radiator that radiates the refrigerant compressed by the compression mechanism, and heat dissipation. The evaporator which evaporates the refrigerant | coolant thermally radiated by the container and the back | latter stage side injection pipe are provided. The compression mechanism includes a first compression unit and a second compression unit that can vary the operation capacity. The first compression unit sucks the low-pressure refrigerant in the refrigeration cycle and compresses it to the intermediate pressure in the refrigeration cycle, and sucks the intermediate-pressure refrigerant in the refrigeration cycle and compresses it to the high pressure in the refrigeration cycle. And a first rear-stage compression element. The second compression section sucks low-pressure refrigerant in the refrigeration cycle and compresses it to an intermediate pressure in the refrigeration cycle, and compresses the intermediate pressure refrigerant in the refrigeration cycle to high pressure in the refrigeration cycle. 2 rear-stage compression elements. Here, the “compression unit” 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. The “compression mechanism” means that these “compression units” are connected in parallel. The intermediate refrigerant pipe is a refrigerant pipe that causes the refrigerant discharged from the front-stage compression element to be sucked into the rear-stage compression element. The rear stage side injection pipe has a rear stage side injection valve, and is a refrigerant pipe that branches the refrigerant radiated by the radiator and returns it to the intermediate refrigerant pipe. The refrigeration apparatus is configured to lower the operating capacity of the first compression unit prior to the start of the second compression unit in the subsequent compression unit activation control in which the second compression unit is activated from the state where the first compression unit is activated. In addition, the opening degree of the rear injection valve is reduced.

  In this refrigeration apparatus, the operating capacity of the first compression unit prior to the start of the second compression unit in the subsequent compression unit activation control in which the second compression unit is activated from the state where the first compression unit capable of varying the operation capacity is activated. Since the opening degree of the rear-stage injection valve is reduced when lowering the flow rate, the intermediate refrigerant pipe is connected from the rear-stage injection pipe despite the decrease in the flow rate of the refrigerant discharged from the first front-stage compression element. Avoiding a state in which the flow rate of the refrigerant returned to the refrigerant flow rate is higher than the flow rate of the refrigerant flowing through the intermediate refrigerant pipe, the refrigerant sucked into the first second-stage compression element can be prevented from becoming wet, Thereby, the reliability of the apparatus can be improved.

  A refrigeration apparatus according to a second aspect of the invention is the refrigeration apparatus according to the first aspect of the invention, wherein the intermediate refrigerant pipe is connected to the discharge side of the first front-stage compression element, the first inlet-side intermediate branch pipe, and the second front-stage. A second inlet side intermediate branch pipe connected to the discharge side of the side compression element, an intermediate mother pipe where the inlet side intermediate branch pipe joins, and a branch from the intermediate mother pipe connected to the suction side of the first second-stage compression element A first outlet-side intermediate branch pipe, and a second outlet-side intermediate branch pipe that has a rear-stage suction valve and is branched from the intermediate mother pipe and connected to the suction side of the second rear-stage compression element. The rear-stage injection pipe is connected to the intermediate mother pipe, and further includes a start-up bypass pipe having a later-stage compression section start-up valve for communicating the second inlet-side intermediate branch pipe and the second outlet-side intermediate branch pipe. I have. And this refrigeration apparatus, after the latter compression part starting control, after closing the latter stage intake valve and starting the second compression part with the latter compression part starting valve opened, the second compression part is started The rear-stage intake valve is opened, and the later-compression compressor starting valve is closed.

  In this refrigeration apparatus, the refrigerant discharged from the first front-stage compression element and the refrigerant discharged from the second front-stage compression element once merge by the intermediate refrigerant pipe, and then the suction side of the first second-stage compression element In the state where only the first compression unit is activated, the discharge side and the second second compression unit of the second compression unit and the second compression unit are branched to the suction side of the second rear compression unit. The suction side of the rear-stage compression element is affected by the pressure on the discharge side of the first front-stage compression element and the pressure on the suction side of the first rear-stage compression element of the first compression section that has already been activated through the intermediate refrigerant pipe. It becomes a state. Therefore, when the second compression unit is activated in the state where the first compression unit is activated, the discharge side of the second pre-stage compression element and the suction side of the second post-stage compression element of the second compression unit are compressed by the first compression unit. If the state affected by the pressure on the discharge side of the first first-stage compression element and the pressure on the suction side of the first second-stage compression element is not relieved, it is difficult to stably start the second compression section There is a risk of becoming.

  Therefore, in this refrigeration apparatus, a second-stage suction valve is provided in the second outlet-side intermediate branch pipe, and an activation bypass pipe that connects the second inlet-side intermediate branch pipe and the second outlet-side intermediate branch pipe is provided, In the subsequent compression unit activation control, the second compression unit is activated with the latter-stage suction valve closed and the subsequent compression unit activation valve provided in the activation bypass pipe opened. As a result, the refrigerant discharged from the second front-stage compression element of the second compression section is joined to the refrigerant discharged from the first front-stage compression element of the first compression section through the startup bypass pipe, without being merged. Since the second rear-stage compression element of the compression section can be sucked, the discharge side of the second front-stage compression element and the suction side of the second rear-stage compression element of the second compression section are the first compression section. The state affected by the pressure on the discharge side of the first-stage compression element and the pressure on the suction side of the first-stage compression element can be alleviated, and the second compression section is activated in the state where the first compression section is activated. When starting, the 2nd compression part can be started stably. And after the 2nd compression part was started stably, by opening the back | latter stage side intake valve and closing the late compression part start valve, it discharged from the 2nd front | former stage side compression element of the 2nd compression part. It is possible to shift to a normal operation state in which the refrigerant is combined with the refrigerant discharged from the first pre-stage compression element of the first compression unit.

  The refrigeration apparatus according to a third aspect of the invention is the refrigeration apparatus according to the second aspect of the invention, wherein the rear side suction valve is opened and the rear side compression part activation valve is closed in the later compression part activation control. The opening of the injection valve is increased.

  In this refrigeration apparatus, after the second compression unit is activated, after the rear-stage intake valve is opened and the subsequent compression unit activation valve is closed (that is, in a normal operation state). In this case, if the opening of the rear-stage injection valve is kept small, both the refrigerant discharged from the first front-stage compression element and the refrigerant discharged from the second front-stage compression element merge to form an intermediate refrigerant. Despite flowing through the intermediate mother pipe of the pipe, the flow rate of the refrigerant returned from the rear-stage injection pipe to the intermediate mother pipe is relatively small compared to the flow rate of the refrigerant flowing through the intermediate mother pipe. Therefore, the effect of reducing the power consumption of the compression mechanism by the intermediate pressure injection and improving the operation efficiency cannot be obtained sufficiently. For this reason, in order to avoid such a state, immediately after the second compression unit is started, the opening degree of the rear-stage injection valve is quickly increased and the rear-stage injection pipe is changed to the intermediate refrigerant pipe. It is desirable to increase the flow rate of the returned refrigerant.

  However, even after the second compression unit is activated, the rear-stage suction valve is closed and the subsequent compression unit activation valve is opened (ie, immediately after activation of the second compression unit). In the state before the shift to normal operation), if the opening of the rear injection valve is increased, the refrigerant flowing through the intermediate mother pipe of the intermediate refrigerant pipe is only the refrigerant discharged from the first front compression element. In spite of this, the flow rate of the refrigerant returned from the rear-stage injection pipe to the intermediate mother pipe increases, so that the refrigerant flow from the rear-stage injection pipe returns to the intermediate mother pipe compared to the flow rate of the refrigerant flowing through the intermediate mother pipe. There is a risk that the refrigerant sucked into the first second-stage compression element of the first compression section will be in a wet state due to the relatively large flow rate of the refrigerant.

  Therefore, in this refrigeration apparatus, even after the second compression unit is activated, the latter-stage injection valve is closed in the closed state where the latter-stage intake valve is closed and the later-stage compression unit activation valve is opened. Without increasing the opening of the valve, when the rear suction valve is opened and the later compression section start valve is closed, by increasing the opening of the rear injection valve, The flow rate of the refrigerant returned to the mother pipe can be made appropriate in consideration of the open / closed states of the second-stage suction valve and the second-stage compression section start valve when starting the second compression section. Even at the time of starting the second compression unit accompanied by the opening and closing control of the valve and the subsequent compression unit starting valve, the refrigerant sucked into the first second-stage compression element is suppressed from becoming wet, and the normal operation state is shifted to. When Quickly, it is possible to increase the flow rate of the refrigerant returned from the second-stage injection tube to the intermediate header tube.

  The refrigeration apparatus according to a fourth aspect of the invention is the refrigeration apparatus according to the second or third aspect of the invention, wherein the intermediate mother pipe is a refrigerant cooler that is discharged from the front-stage compression element and sucked into the rear-stage compression element. A functioning intermediate heat exchanger is provided.

  In this refrigeration apparatus, an intermediate heat exchanger is provided in the intermediate mother pipe, and before the refrigerant flowing through the intermediate mother pipe joins with the refrigerant returned from the latter-stage injection pipe to the intermediate mother pipe, Since the refrigerant is cooled more than the discharged state, there is a high possibility that the refrigerant sucked into the rear-stage compression element after joining the refrigerant returned from the rear-stage injection pipe to the intermediate mother pipe becomes wet. .

  However, in this refrigeration apparatus, when the operating capacity of the first compression unit is reduced prior to the start of the second compression unit in the subsequent compression unit activation control in which the second compression unit is activated from the state in which the first compression unit is activated. In addition, since the opening degree of the second-stage injection valve is made smaller, and in the second-stage compression section activation control, the second compression section is closed with the second-stage suction valve closed and the second-stage compression section activation valve opened. After the second compression unit is activated, the rear side suction valve is opened and the subsequent compression unit activation valve is closed to stably start the second compression unit. When the intake valve is opened and the late compression section start valve is closed, the opening of the rear injection valve is increased, so that the refrigerant flowing through the intermediate mother pipe is transferred from the rear injection pipe to the intermediate mother pipe. Refrigerant returned to the tube Before joining, the refrigerant sucked into the first second-stage compression element is suppressed from becoming wet despite being cooled more than the state discharged from the first-stage compression element. As a result, the reliability of the apparatus can be improved.

  The refrigeration apparatus according to a fifth aspect of the present invention is the refrigeration apparatus according to any one of the first to fourth aspects of the invention, wherein an economizer heat exchanger performs heat exchange between the refrigerant that has radiated heat in the radiator and the refrigerant that flows through the rear-stage injection pipe. Is further provided.

  The refrigeration apparatus according to a sixth aspect of the present invention is the refrigeration apparatus according to any of the first to fifth aspects 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 the first, fifth, and sixth inventions, in the subsequent compression unit activation control for activating the second compression unit from the state in which the first compression unit is activated, the first compression unit is activated prior to activation of the second compression unit. When reducing the operating capacity, it is possible to suppress the refrigerant sucked into the first second-stage compression element from becoming wet, thereby improving the reliability of the apparatus.

  In the second invention, when the second compression unit is activated in the state where the first compression unit is activated, the second compression unit can be stably activated.

  In the third aspect of the invention, the refrigerant sucked into the first second-stage compression element is prevented from becoming wet even when starting the second compression section that is associated with the opening / closing control of the second-stage suction valve and the second-stage compression section starting valve. At the same time, when the operation state is shifted to the normal operation state, the flow rate of the refrigerant returned from the rear-stage injection pipe to the intermediate mother pipe can be quickly increased.

  In 4th invention, before the refrigerant | coolant which flows through an intermediate | middle mother pipe merges with the refrigerant | coolant returned to an intermediate | middle mother pipe from a back | latter stage side injection pipe, it will be in the state cooled rather than the state discharged from the front | former stage side compression element Nevertheless, it is possible to suppress the refrigerant sucked into the first second-stage compression element from becoming wet, thereby improving the reliability of the apparatus.

  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 includes a refrigerant circuit 10 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 10 of the air conditioner 1 mainly includes a compression mechanism 102, a switching mechanism 3, a heat source side heat exchanger 4, a bridge circuit 17, a receiver 18, a first expansion mechanism 5a, and a second expansion mechanism. 5b, a first second-stage injection pipe 18c, a use-side heat exchanger 6, and an intermediate heat exchanger 7.

  The compression mechanism 102 connects a plurality of compression units (here, two compression units 103 and 104) having a front-stage compression element and a rear-stage compression element in parallel, and one of the compression units 103 and 104 (here Then, it is assumed that the operating capacity of the first compression unit 103) can be varied, and the change in the operation capacity of the first compression unit 103 and the change in the number of operating units of other compression units (here, the second compression unit 104) are combined. Accordingly, the operation capacity of the entire compression mechanism 102 can be varied. In the present embodiment, as the first compressor 29 and the second compressor 104 as the first compression unit 103 that can vary the operation capacity. The second compressor 30 is provided.

  The first compressor 29 has a sealed structure in which a compressor drive motor 29b, a drive shaft 29c, and compression elements 103c and 103d are accommodated in a casing 29a. The compressor drive motor 29b is connected to the drive shaft 29c. The drive shaft 29c is connected to the two compression elements 103c and 103d. That is, in the first compressor 29, two compression elements 103c and 103d are connected to a single drive shaft 29c, and the two compression elements 103c and 103d are both rotationally driven by a compressor drive motor 29b. It has a uniaxial two-stage compression structure. Here, the compression elements 103c and 103d are positive displacement type compression elements such as a rotary type and a scroll type in the present embodiment. Further, in the present embodiment, the compressor drive motor 29b is capable of varying the operating capacity by controlling the operating frequency (motor rotational speed) by an inverter device (not shown). The operation is performed with priority over the two compressors 30 (that is, when the compression mechanism 102 is started, the first compressor 29 as the first compressor 103 becomes the second compressor as the second compressor 104. The second compressor 30 is started before the second compressor 30 and stopped when the compression mechanism 102 is stopped. The first compressor 29 is connected to the first suction branch pipe 103a branched from the suction mother pipe 102a of the compression mechanism 102 and the first discharge branch pipe 103b joined to the discharge mother pipe 102b of the compression mechanism 102. The first front-stage compression element 103c sucks low-pressure refrigerant in the refrigeration cycle from the first suction branch pipe 103a, compresses it to the intermediate pressure in the refrigeration cycle, and then discharges it to the intermediate refrigerant pipe 8, thereby The compression element 103d is configured to suck the intermediate-pressure refrigerant in the refrigeration cycle from the intermediate refrigerant pipe 8 and compress it to a high pressure in the refrigeration cycle, and then discharge it to the first discharge branch pipe 103b.

  The second compressor 30 has a sealed structure in which a compressor drive motor 30b, a drive shaft 30c, and compression elements 104c and 104d are accommodated in a casing 30a. The compressor drive motor 30b is connected to the drive shaft 30c. The drive shaft 30c is connected to the two compression elements 104c and 104d. That is, in the second compressor 30, like the first compressor 29, two compression elements 104c and 104d are connected to a single drive shaft 30c, and the two compression elements 104c and 104d are both compressor drive motors. It is a so-called uniaxial two-stage compression structure that is rotationally driven by 30b. Here, in the present embodiment, the compression elements 104c and 104d are positive displacement compression elements such as a rotary type and a scroll type. However, unlike the first compressor 29, the compressor drive motor 30b is operated at a constant motor speed in the present embodiment. The second compressor 30 is connected to the second suction branch pipe 104a branched from the suction mother pipe 102a of the compression mechanism 102 and the second discharge branch pipe 104b joined to the discharge mother pipe 102b of the compression mechanism 102. The low-pressure refrigerant in the refrigeration cycle is sucked from the second suction branch pipe 104a by the second front-stage compression element 104c, compressed to the intermediate pressure in the refrigeration cycle and discharged, and the second rear-stage compression element 104d A refrigerant having an intermediate pressure in the refrigeration cycle is sucked from the intermediate refrigerant pipe 8, compressed to a high pressure in the refrigeration cycle, and then discharged to the second discharge branch pipe 104b.

  Here, the discharge mother pipe 102 b is a refrigerant pipe for sending the refrigerant discharged from the compression mechanism 102 to the switching mechanism 3. The first discharge branch pipe 103b connected to the discharge mother pipe 102b is provided with a first oil separation mechanism 141 and a first check mechanism 142, and the second discharge connected to the discharge mother pipe 102b. The branch pipe 104b is provided with a second oil separation mechanism 143 and a second check mechanism 144. The first oil separation mechanism 141 is a mechanism that separates the refrigeration oil accompanying the refrigerant discharged from the first compression unit 103 from the refrigerant and returns it to the suction side of the compression mechanism 102, and is mainly discharged from the first compression unit 103. The first oil separator 141a 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 141a and returns the refrigeration oil separated from the refrigerant to the suction side of the compression mechanism 102 And an oil return pipe 141b. The second oil separation mechanism 143 is a mechanism that separates the refrigerating machine oil accompanying the refrigerant discharged from the second compression unit 104 from the refrigerant and returns it to the suction side of the compression mechanism 102, and is mainly discharged from the second compression unit 104. A second oil separator 143a that separates the refrigeration oil accompanying the refrigerant from the refrigerant, and a second oil separator that is connected to the second oil separator 143a and returns the refrigeration oil separated from the refrigerant to the suction side of the compression mechanism 102. And an oil return pipe 143b. In the present embodiment, the first oil return pipe 141b is connected to the second suction branch pipe 104a, and the second oil return pipe 143c is connected to the first suction branch pipe 103a. For this reason, the refrigerant discharged from the first compression unit 103 due to a deviation between the amount of the refrigeration oil accumulated in the first compression unit 103 and the amount of the refrigeration oil accumulated in the second compression unit 104 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 unit 104, the amount of refrigerating machine oil in the compression units 103 and 104 is A large amount of refrigeration oil will return to the smaller one, so that the bias between the amount of refrigeration oil accumulated in the first compression unit 103 and the amount of refrigeration oil accumulated in the second compression unit 104 is eliminated. It has become. In the present embodiment, the oil return pipes 141b and 143b are provided with pressure reducing mechanisms 141c and 143c for reducing the pressure of the refrigerating machine oil flowing through the oil return pipes 141b and 143b. The check mechanisms 142 and 144 allow the refrigerant to flow from the discharge side of the compression units 103 and 104 to the switching mechanism 3, and the refrigerant flows from the switching mechanism 3 to the discharge side of the compression units 103 and 104. It is a mechanism for shutting off.

  Further, in the present embodiment, the first suction branch pipe 103a has a portion between the junction with the second oil return pipe 143b and the junction with the suction mother pipe 102a at the junction with the suction mother pipe 102a. The second suction branch pipe 104a is configured such that the portion between the junction with the first oil return pipe 141b and the junction with the suction mother pipe 102a is the suction mother pipe. It is comprised so that it may become a downward slope toward the confluence | merging part with 102a. For this reason, even when only the second compression unit 104 is stopped, the first oil return pipe 141b corresponding to the operating first compression unit 103 is connected to the stopped second compression unit 104. The refrigerating machine oil returned to the two suction branch pipes 104a returns to the suction mother pipe 102a, and the first compressor 103 during operation is less likely to run out of oil.

  The intermediate refrigerant pipe 8 is a refrigerant pipe for sucking the refrigerant discharged from the front-stage compression elements 103c and 104c into the rear-stage compression elements 103d and 104d. A first inlet-side intermediate branch pipe 81 connected to the discharge side of 103c, a second inlet-side intermediate branch pipe 84 connected to the discharge side of the second pre-stage compression element 104c of the second compression section 104, and both inlets An intermediate mother pipe 82 where the side intermediate branch pipes 81 and 84 merge, and a first outlet-side intermediate branch branched from the intermediate mother pipe 82 and connected to the suction side of the first second-stage compression element 103d of the first compressor 103. The pipe 83 and the second outlet side intermediate branch pipe 85 branched from the intermediate mother pipe 82 and connected to the suction side of the second second-stage compression element 104d of the second compression section 104 are provided. 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 first front-stage compression element 103c of the first compression section 103 to the intermediate mother pipe 82 side. In addition, a non-return mechanism 81a for blocking the flow of the refrigerant from the intermediate mother pipe 82 side to the discharge side of the first pre-stage compression element 103c is provided, and the second inlet side constituting the intermediate refrigerant pipe 8 is provided. The intermediate branch pipe 84 allows the refrigerant to flow from the discharge side of the second pre-stage compression element 104c of the second compression section 103 to the intermediate mother pipe 82 side, and from the intermediate mother pipe 82 side to the second pre-stage side. A check mechanism 84a for blocking the flow of the refrigerant to the discharge side of the compression element 104c is provided. In the present embodiment, check valves are used as the check mechanisms 81a and 84a. For this reason, even when only the first compression unit 103 is in operation, the refrigerant discharged from the first pre-stage compression element 103c of the first compression unit 103 in operation is stopped through the intermediate refrigerant pipe 8 and the second Since it does not reach the discharge side of the second front-stage compression element 104c of the compression unit 104, the refrigerant discharged from the first front-stage compression element 103c of the operating first compression unit 103 is stopped. The refrigeration oil of the second compression unit 104 that has stopped stops flowing out of the second compression unit 104 through the second pre-stage compression element 104c of the second compression unit 104 to the suction side. As a result, the shortage of refrigerating machine oil is less likely to occur when starting the stopped second compression unit 104.

  Further, in the present embodiment, the intermediate refrigerant pipe 8 (more specifically, the intermediate mother pipe 82) is provided in common in the compression sections 103 and 104, and the first front-stage compression element is provided by the intermediate refrigerant pipe 8. The refrigerant discharged from 103c and the refrigerant discharged from the second front-stage compression element 104c once merge, and then branch to the suction side of the first second-stage compression element 103d and the suction side of the second second-stage compression element 104d In the state where only the first compression unit 103 is activated, the discharge side of the second pre-stage compression element 104c of the second compression unit 104 and the suction side of the second post-stage compression element 104d are Through the intermediate refrigerant pipe 8, it is in a state affected by the pressure on the discharge side of the first front-stage compression element 103c and the pressure on the suction side of the first rear-stage compression element 103d of the first compressor 103 that has already been activated. . Therefore, when the second compression unit 104 is activated in the state where the first compression unit 103 is activated, the discharge side of the second pre-stage compression element 104c and the second rear-stage compression element 104d of the second compression unit 104 are activated. If the suction side does not relieve the influence of the pressure on the discharge side of the first pre-stage compression element 103c of the first compression section 103 and the pressure on the suction side of the first post-stage compression element 103d, the second compression section 104 May be difficult to start stably. Therefore, in this embodiment, the second outlet side intermediate branch pipe 85 is provided with a rear-stage suction valve 85a, and the second inlet side intermediate branch pipe 84 and the second outlet side intermediate branch pipe 85 communicate with each other. 86, the second-stage compression unit activation control for activating the second compression unit 104 from the state in which the first compression unit 103 is activated. The latter-stage intake valve 85a is closed and provided in the activation bypass pipe 86. The second compression unit 104 is activated with the late compression unit activation valve 86a opened. Thus, the start-up bypass pipe can be obtained without merging the refrigerant discharged from the second front-stage compression element 104c of the second compression section 104 with the refrigerant discharged from the first front-stage compression element 103c of the first compression section 103. 86, the second rear-stage compression element 104d of the second compression section 104 can be sucked, so that the discharge side and the second rear-stage compression element of the second front-stage compression element 104c of the second compression section 104 104d can reduce the state where the suction side is affected by the pressure on the discharge side of the first pre-stage compression element 103c of the first compression unit 103 and the pressure on the suction side of the first post-stage compression element 103d. When the second compression unit 104 is activated in a state where the compression unit 103 is activated, the second compression unit 104 can be stably activated. After the second compression unit 104 is stably started, the second-stage compression element of the second compression unit 104 is opened by opening the second-stage suction valve 85a and closing the second-stage compression unit activation valve 86a. It is possible to shift to a normal operation state in which the refrigerant discharged from 104c is merged with the refrigerant discharged from the first pre-stage compression element 103c of the first compression unit 103. In the present embodiment, one end of the activation bypass pipe 86 is between the rear side suction valve 85a of the second outlet side intermediate branch pipe 85 and the suction side of the second rear stage side compression element 104d of the second compression unit 104. And the other end is connected between the discharge side of the second pre-stage compression element 104c of the second compression section 104 and the check mechanism 84a of the second inlet side intermediate branch pipe 84, and the second compression section When starting 104, the pressure on the discharge side of the first pre-stage compression element 103c of the first compression unit 103 and the pressure on the suction side of the first post-stage compression element 103d are further less affected. Further, in the present embodiment, electromagnetic valves are used as the rear-stage suction valve 85a and the subsequent compression section start valve 86a.

  Further, in the present embodiment, since the intermediate refrigerant pipe 8 (more specifically, the intermediate mother pipe 82) is provided in common for the compression sections 103 and 104, it corresponds to the first compression section 103 during operation. The refrigerant discharged from the first front-stage compression element 103c reaches the suction side of the second second-stage compression element 104d of the stopped second compression section 104 through the second outlet-side intermediate branch pipe 85 of the intermediate refrigerant pipe 8, As a result, the refrigerant discharged from the first front-stage compression element 103c of the operating first compression section 103 passes through the second second-stage compression element 104d of the second compression section 104 being stopped, and the discharge side of the compression mechanism 102 There is a risk that the refrigerating machine oil of the second compression unit 104 that is stopped flows out and flows out, and the shortage of refrigerating machine oil occurs when starting the second compression mechanism 104 that is stopped. However, in the present embodiment, as described above, the second outlet side intermediate branch pipe 85 is provided with the rear-stage suction valve 85a. Therefore, when the second compression unit 104 is stopped, the second-stage suction valve 85a is stopped. The flow of the refrigerant in the second outlet side intermediate branch pipe 85 can be blocked by the valve 85a. As a result, the refrigerant discharged from the first pre-stage compression element 103c of the operating first compression section 103 passes through the second outlet-side intermediate branch pipe 85 of the intermediate refrigerant pipe 8, and the second compression section 104 of the stopped second compression section 104 (2) Since it does not reach the suction side of the second-stage compression element 104d, the refrigerant discharged from the first first-stage compression element 103c of the operating first compression section 103 is second in the stopped second compression section 104. It will not occur that the refrigerating machine oil of the stopped second compression section 104 flows out into the discharge side of the compression mechanism 102 through the downstream side compression element 104d, thereby starting the stopped second compression section 104. The shortage of refrigerating machine oil is even less likely to occur.

  The switching mechanism 3 is a mechanism for switching the flow direction of the refrigerant in the refrigerant circuit 10, and is used as a radiator for the refrigerant compressed by the compression mechanism 102 and used in the cooling operation during the cooling operation. In order for the side heat exchanger 6 to function as an evaporator of the refrigerant cooled in the heat source side heat exchanger 4, the discharge side of the compression mechanism 102 and one end of the heat source side heat exchanger 4 are connected and the compression mechanism 102 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 radiator for the refrigerant compressed by the compression mechanism 102 and the heat source side heat exchanger 4 to function as an evaporator for the refrigerant cooled in the use side heat exchanger 6, Discharge side It is possible to connect the use side heat exchanger 6 and connect the suction side of the compression mechanism 102 and one end of the heat source side heat exchanger 4 (see the broken line of the switching mechanism 3 in FIG. The state of the switching mechanism 3 is referred to as a “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 102, the discharge side of the compression mechanism 102, 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, the switching mechanism 3 focuses on only the compression mechanism 102, the heat source side heat exchanger 4 and the use side heat exchanger 6 constituting the refrigerant circuit 10, and the heat source side that functions as the compression mechanism 102 and the refrigerant radiator. The cooling operation state in which the refrigerant is circulated in the order of the heat exchanger 4 and the use side heat exchanger 6 that functions as a refrigerant evaporator, the compression mechanism 102, the use side heat exchanger 6 that functions as a refrigerant radiator, and the evaporation of the refrigerant It is comprised so that the heating operation state which circulates a refrigerant | coolant in order of the heat source side heat exchanger 4 which functions as a heater can be switched.

  The heat source side heat exchanger 4 is a heat exchanger that functions as a refrigerant radiator or an evaporator. 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 first expansion mechanism 5 a via the bridge circuit 17. The heat source side heat exchanger 4 is a heat exchanger that uses water or air as a heat source (that is, a cooling source or a heating source).

  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 first expansion mechanism 5a is a mechanism that depressurizes the refrigerant provided in the receiver inlet pipe 18a, and an electric expansion valve is used in the present embodiment. In the present embodiment, the first expansion mechanism 5a is configured to send the high-pressure refrigerant in the refrigeration cycle cooled in the heat source side heat exchanger 4 to the use side heat exchanger 6 via the receiver 18 during the cooling operation. The pressure is reduced to near the saturation pressure of the refrigerant, and at the time of heating operation, before the high-pressure refrigerant in the refrigeration cycle cooled in the use side heat exchanger 6 is sent to the heat source side heat exchanger 4 via the receiver 18, the vicinity of the saturation pressure of the refrigerant Depressurize until.

  The receiver 18 is depressurized by the first expansion mechanism 5a so as to be able to store surplus refrigerant generated in accordance with an operation state such as a difference in refrigerant circulation amount in the refrigerant circuit 10 between the cooling operation and the heating operation. The inlet is connected to the receiver inlet pipe 18a, and the outlet thereof is connected to the receiver outlet pipe 18b. In addition, the first suction that can extract the refrigerant from the receiver 18 and return it to the suction mother pipe 102a of the compression mechanism 102 (that is, the suction side of the front-stage compression elements 103c and 104c of the compression mechanism 102). A return pipe 18f is connected.

  The first second-stage injection pipe 18c is a refrigerant pipe capable of performing intermediate pressure injection for returning the gas refrigerant separated by the receiver 18 as a gas-liquid separator to the second-stage compression elements 103d and 104d of the compression mechanism 102. In the present embodiment, the upper part of the receiver 18 and the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 (that is, the suction side of the rear-stage compression elements 103d and 104d of the compression mechanism 102) are connected. . The first second-stage injection pipe 18c is provided with a first second-stage injection on / off valve 18d and a first second-stage injection check mechanism 18e. The first second-stage injection on / off valve 18d is a valve capable of opening / closing control, and is an electromagnetic valve in the present embodiment. The first second-stage injection check mechanism 18e allows the flow of refrigerant from the receiver 18 to the second-stage compression elements 103d and 104d, and blocks the refrigerant flow from the second-stage compression elements 103d and 104d to the receiver 18. In this embodiment, a check valve is used.

  The first suction return pipe 18f is a refrigerant pipe that can extract the refrigerant from the receiver 18 and return it to the preceding compression elements 103c and 104c of the compression mechanism 102. In this embodiment, the upper part of the receiver 18 and the suction mother pipe 102a (that is, the suction side of the pre-stage compression elements 103c and 104c of the compression mechanism 102) is provided. The first suction return pipe 18f is provided with a first suction return on / off valve 18g. The first suction return on / off valve 18g is a valve capable of opening / closing control, and is an electromagnetic valve in the present embodiment.

  Thus, when the receiver 18 uses the first second-stage injection pipe 18c and the first suction-return pipe 18f by opening the first second-stage injection on-off valve 18d and the first suction return on-off valve 18g, The refrigerant flowing between the side heat exchanger 4 and the use side heat exchanger 6 functions as a gas-liquid separator that performs gas-liquid separation between the first expansion mechanism 5a and the second expansion mechanism 5b. The gas refrigerant separated in the receiver 18 can be returned from the upper part of the receiver 18 to the rear-stage compression elements 103d and 104d and the front-stage compression elements 103c and 104c of the compression mechanism 102.

  The second 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 second 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 second expansion mechanism 5b is at a low pressure in the refrigeration cycle before the refrigerant decompressed by the first expansion mechanism 5a is sent to the use-side heat exchanger 6 via the receiver 18 during the cooling operation. In the heating operation, the refrigerant decompressed by the first expansion mechanism 5a is further depressurized until it reaches a low pressure in the refrigeration cycle before being sent to the heat source side heat exchanger 4 via the receiver 18.

  The use side heat exchanger 6 is a heat exchanger that functions as a refrigerant evaporator or a radiator. One end of the use side heat exchanger 6 is connected to the first expansion mechanism 5 a via the bridge circuit 17, and the other end is connected to the switching mechanism 3. The use-side heat exchanger 6 is a heat exchanger that uses water or air as a heat source (that is, a cooling source or a heating source).

  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 The use side heat through the inlet check valve 17a of the bridge circuit 17, the first expansion mechanism 5a of the receiver inlet pipe 18a, the receiver 18, the second 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 is the first expansion mechanism of the inlet check valve 17b of the bridge circuit 17 and the receiver inlet pipe 18a. 5a, the receiver 18, the second expansion mechanism 5b of the receiver outlet pipe 18b, and the outlet check valve 17d of the bridge circuit 17 can be sent to the heat source side heat exchanger 4.

  The intermediate heat exchanger 7 is provided in the intermediate refrigerant pipe 8, and in this embodiment, the refrigerant discharged from the front-stage compression elements 103c, 104c and sucked into the rear-stage compression elements 103d, 104d during the cooling operation. It is a heat exchanger that can function as a cooler. More specifically, the intermediate heat exchanger 7 is provided in the intermediate mother pipe 82 constituting the intermediate refrigerant pipe 8, and is discharged from the first front-stage compression element 103c of the first compression section 103 during the cooling operation. This is a heat exchanger that cools the mixture of the refrigerant and the refrigerant discharged from the second pre-stage compression element 104c of the second compression unit 104. That is, the intermediate heat exchanger 7 functions as a common cooler for the two compression units 103 and 104 during the cooling operation, and the circuit configuration around the compression mechanism 102 is provided when the intermediate heat exchanger 7 is provided. Is simplified. The intermediate heat exchanger 7 is a heat exchanger that uses water or air as a heat source (here, a cooling source). Thus, the intermediate heat exchanger 7 can be said to be a cooler using an external heat source in the sense that it does not use the refrigerant circulating in the refrigerant circuit 10.

  An intermediate heat exchanger bypass pipe 9 is connected to the intermediate refrigerant pipe 8 so as to bypass the intermediate heat exchanger 7. The intermediate heat exchanger bypass pipe 9 is a refrigerant pipe that limits the flow rate of the refrigerant flowing through the intermediate heat exchanger 7. The intermediate heat exchanger bypass pipe 9 is provided with an intermediate heat exchanger bypass on / off valve 11. The intermediate heat exchanger bypass opening / closing valve 11 is a solenoid valve in the present embodiment. In the present embodiment, the intermediate heat exchanger bypass on-off valve 11 is basically closed when the switching mechanism 3 is in the cooling operation state, and is controlled to be opened when the switching mechanism 3 is in the heating operation state. Made. That is, the intermediate heat exchanger bypass on-off 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 portion from a connection portion of the intermediate heat exchanger bypass pipe 9 with the front-side compression elements 103c, 104c side end to the front-stage compression elements 103c, 104c side end of the intermediate heat exchanger 7. An intermediate heat exchanger on / off valve 12 is provided. The intermediate heat exchanger on / off valve 12 is a mechanism that limits the flow rate of the refrigerant flowing through the intermediate heat exchanger 7. The intermediate heat exchanger on / off valve 12 is an electromagnetic valve in the present embodiment. In the present embodiment, the intermediate heat exchanger on / off valve 12 is basically controlled to be opened when the switching mechanism 3 is in the cooling operation state and closed when the switching mechanism 3 is in the heating operation state. The That is, the intermediate heat exchanger on / off valve 12 is controlled to be opened when the cooling operation is performed and closed when the heating operation is performed.

  The intermediate refrigerant pipe 8 allows the refrigerant to flow from the discharge side of the front-stage compression elements 103c and 104c to the suction side of the rear-stage compression elements 103d and 104d, and sucks the rear-stage compression elements 103d and 104d. A check mechanism 15 is provided to block the flow of refrigerant from the side to the discharge side of the pre-stage compression elements 103c, 104c. The check mechanism 15 is a check valve in the present embodiment. In this embodiment, the check mechanism 15 includes the compression elements 103d and 104d on the downstream side of the intermediate heat exchanger bypass pipe 9 from the end on the downstream side of the intermediate heat exchanger 7 in the intermediate heat exchanger 7 on the side of the downstream stage compression elements 103d and 104d. It is provided in the part to the connection part with a side end.

  As described above, the air-conditioning apparatus 1 according to the present embodiment can switch between the cooling operation and the heating operation and has the refrigerant circuit 10 having the refrigerant circuit 10 capable of intermediate pressure injection by the receiver 18 as a gas-liquid separator. In the configuration in which the refrigeration cycle is performed, the intermediate heat exchanger 7 and the intermediate heat exchanger bypass pipe 9 are provided so that they are discharged from the front-stage compression elements 103c and 104c and sucked into the rear-stage compression elements 103d and 104d during the cooling operation. The refrigerant to be cooled is cooled by the intermediate heat exchanger 7, and the refrigerant discharged from the front-stage compression elements 103 c and 104 c and sucked into the rear-stage compression elements 103 d and 104 d is not cooled by the intermediate heat exchanger 7 during the heating operation. I have to. In addition, the compression mechanism 102 connects a plurality of compression units (here, the two compression units 103 and 104) having a front-stage compression element and a rear-stage compression element in parallel, and one of the compression units 103 and 104. (Here, the first compression unit 103) is variable in operating capacity, and is operated preferentially over other compression units (here, the second compression unit 104). Since the operation capacity of the entire compression mechanism 102 can be varied by combining the change of the operation capacity of 103 and the change of the number of operating units of other compression units (here, the second compression unit 104), Even when the second compression unit 104 is activated, the later-described compression unit activation control described below is performed so that the operation state of the entire compression mechanism 102 does not become unstable.

  Furthermore, the air conditioning apparatus 1 is provided with various sensors. Specifically, the suction mother pipe 102 a or the compression mechanism 102 is provided with a suction pressure sensor 60 that detects the pressure of the refrigerant flowing on the suction side of the compression mechanism 102. The intermediate refrigerant pipe 8 is provided with an intermediate pressure sensor 54 that detects an intermediate pressure in the refrigeration cycle that is the pressure of the refrigerant flowing through the intermediate refrigerant pipe 8. Although not shown here, the air conditioner 1 includes a compression mechanism 102, a switching mechanism 3, expansion mechanisms 5a and 5b, an intermediate heat exchanger bypass on-off valve 11, an intermediate heat exchanger on-off valve 12, and a first second-stage injection. It has a control part which controls operation of each part which constitutes air harmony device 1 such as on-off valve 18d, latter stage side intake valve 85a, late compression part starting valve 86a, and 1st suction return on-off valve 18g.

(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 diagram illustrating the flow of the refrigerant in the air conditioner 1 during the cooling operation, and FIG. 3 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the cooling operation. FIG. 5 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation, FIG. 5 is a diagram illustrating the flow of refrigerant in the air conditioner 1 during heating operation, and FIG. 6 is during heating operation. FIG. 7 is a pressure-enthalpy diagram illustrating the refrigeration cycle of FIG. 7, FIG. 7 is a temperature-entropy diagram illustrating the refrigeration cycle during heating operation, and FIG. 9 is a diagram showing the refrigerant flow in the air-conditioning apparatus 1 before the start of the subsequent compression unit activation control (that is, the state where only the first compression unit 103 is activated), and FIG. 2 Compression unit 104 is activated That is, after the start of the second compression section 104, before the opening operation of the rear-stage suction valve 85a, the closing operation of the subsequent-stage compression section starting valve 86a, and the opening operation of the first second-stage injection on / off valve 18d. It is a figure which shows the flow of the refrigerant | coolant in the air conditioning apparatus 1 in a state. The following cooling operation, heating operation, and operation control in starting the compression mechanism are 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, D ′, and E in FIGS. 3 and 4 and pressure at points D, D ′, and F in FIGS. 6 and 7). “Low pressure” means low pressure in the refrigeration cycle (that is, pressure at points A and F in FIGS. 3 and 4 and pressure at points A and E in FIGS. 6 and 7), and “intermediate pressure” Means the intermediate pressure in the refrigeration cycle (that is, the pressure at points B, C, C ′, G, G ′, I, L, M in FIGS. 3, 4, 6, 7).

<Cooling operation>
During the cooling operation, the switching mechanism 3 is in the cooling operation state indicated by the solid line in FIGS. The opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted. Since the switching mechanism 3 is in the cooling operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is opened, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is closed. Thus, the intermediate heat exchanger 7 is brought into a state of functioning as a cooler. Further, the first second-stage injection on / off valve 18d is opened. Here, in order to explain the cooling operation in the state where both the first compression unit 103 and the second compression unit 104 are activated as an example, the rear-stage suction valve 85a is opened, and the subsequent compression unit activation valve 86a is closed. It is made to the state that was made. However, in the cooling operation in a state where only the first compression unit 103 is activated, the rear-stage suction valve 85a and the subsequent compression unit activation valve 86a are closed (see FIG. 9).

  In the state of the refrigerant circuit 10, a low-pressure refrigerant (see point A in FIGS. 1 to 4) is sucked into the compression mechanism 102 from the suction mother pipe 102a, and is first compressed to an intermediate pressure by the front-stage compression elements 103c and 104c. Then, the refrigerant is discharged to the inlet side intermediate branch pipes 81 and 84 of the intermediate refrigerant pipe 8 and merges in the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 through the check mechanisms 81a and 84a (point B in FIGS. 1 to 4). reference). The intermediate-pressure refrigerant discharged from the preceding-stage compression elements 103c and 104c and joined in the intermediate refrigerant pipe 8 is cooled in the intermediate heat exchanger 7 by exchanging heat with water or air as a cooling source ( (See point C in FIGS. 1-4). The refrigerant cooled in the intermediate heat exchanger 7 joins with the refrigerant (see point M in FIGS. 1 to 4) returned from the receiver 18 to the rear-stage compression elements 103d and 104d through the first rear-stage injection pipe 18c. (Refer to point G in FIGS. 1 to 4). Next, the intermediate-pressure refrigerant that has joined with the refrigerant returning from the first rear-stage injection pipe 18c (that is, the intermediate-pressure injection by the receiver 18 as a gas-liquid separator) is the middle of the intermediate refrigerant pipe 8 at the outlet side. Branches into branch pipes 83 and 85. The intermediate-pressure refrigerant branched from the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 to the outlet-side intermediate branch pipes 83 and 85 is supplied to the rear-stage compression elements 103d and 104d connected to the rear-stage side of the front-stage compression elements 103c and 104c. The air is sucked and further compressed, and is discharged from the compression parts 103 and 104 to the discharge branch pipes 103b and 104b (see point D in FIGS. 1 to 4). Here, the high-pressure refrigerant discharged from the compression units 103 and 104 is subjected to the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 3) by the two-stage compression operation by the compression elements 103c, 104c, 103d, and 104d. ) Compressed to a pressure exceeding The high-pressure refrigerant discharged from the first compression unit 103 flows into the first oil separator 141a constituting the first oil separation mechanism 141, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the first oil separator 141a flows into the first oil return pipe 141b constituting the first oil separation mechanism 141, and the first oil return pipe 141b is provided with the first oil return pipe 141b. After being depressurized by the first depressurization mechanism 141 c, it is returned to the second suction branch pipe 104 a of the second compression unit 104 and again sucked into the compression mechanism 102. Further, the high-pressure refrigerant discharged from the second compression unit 104 flows into the second oil separator 143a constituting the second oil separation mechanism 143, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the second oil separator 143a flows into the second oil return pipe 143b that constitutes the second oil separation mechanism 143, and is supplied to the second oil return pipe 143b. After the pressure is reduced by the second pressure reducing mechanism 143 c, the pressure is returned to the first suction branch pipe 103 a of the first compression unit 103 and is again sucked into the compression mechanism 102. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanisms 141 and 143 passes through the check mechanisms 142 and 144 and then merges in the discharge mother pipe 102b. It is sent to the heat source side heat exchanger 4 functioning as The high-pressure refrigerant sent to the heat source side heat exchanger 4 is cooled by exchanging heat with water or air as a cooling source in the heat source side heat exchanger 4 (point E in FIGS. 1 to 4). reference). The high-pressure refrigerant cooled in the heat source side heat exchanger 4 flows into the receiver inlet pipe 18a through the inlet check valve 17a of the bridge circuit 17, and is reduced to the vicinity of the intermediate pressure by the first expansion mechanism 5a. Gas and liquid separation is performed while being temporarily stored inside (see points I, L and M in FIGS. 1 to 4). The gas refrigerant separated from the gas and liquid in the receiver 18 is extracted from the upper part of the receiver 18 by the first second-stage injection pipe 18c, and is discharged from the first-stage compression elements 103c and 104c as described above. Will join the refrigerant. Then, the liquid refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is decompressed by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve of the bridge circuit 17 It is sent to the use side heat exchanger 6 functioning as an evaporator of the refrigerant through 17c (see point F in FIGS. 1 to 4). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use-side heat exchanger 6 is heated by heat exchange with water or air as a heating source to evaporate (FIGS. 1 to 1). (See point A in 4). Then, the low-pressure refrigerant heated in the use side heat exchanger 6 is again sucked into the compression mechanism 102 via the switching mechanism 3. In this way, the cooling operation is performed.

  Thus, in the air conditioning apparatus 1 (refrigeration apparatus) of this embodiment, the 1st back | latter stage side injection pipe 18c is provided, the refrigerant | coolant thermally radiated in the heat source side heat exchanger 4 is branched, and back | latter stage side compression elements 103d and 104d In addition to the cooling effect of the refrigerant sucked into the rear-stage compression elements 103d and 104d by performing the intermediate pressure injection by the receiver 18 as the gas-liquid separator to be returned to the refrigerant, the refrigerant discharged from the front-stage compression elements 103c and 104c An intermediate heat exchanger 7 is provided in the intermediate refrigerant pipe 8 to be sucked into the downstream side compression elements 103d and 104d, the intermediate heat exchanger on / off valve 12 is opened during cooling operation, and the intermediate heat exchanger bypass on / off valve is opened. 11 is closed so that the intermediate heat exchanger 7 functions as a cooler. When the cooling effect of the refrigerant sucked into 3d and 104d is added and the intermediate heat exchanger 7 is not provided or the intermediate heat exchanger 7 is not used (in this case, in FIG. 3 and FIG. B → Point G ′ → Point D ′ → Point E → Point I → Point L → Point F in this order), the rear side compression elements 103c and 104c are changed to the rear stage side compression elements 103d and 104d. The temperature of the refrigerant sucked decreases (see points G and G ′ in FIG. 4), and the temperature of the refrigerant finally discharged from the compression mechanism 102 can be kept low (see points D and D ′ in FIG. 4). ). Thereby, in this air conditioner 1, since the heat radiation loss in the heat source side heat exchanger 4 functioning as a refrigerant radiator is reduced during the cooling operation, the operation efficiency is further improved as compared with the case of only intermediate pressure injection. Can be improved.

<Heating operation>
During the heating operation, the switching mechanism 3 is in the heating operation state indicated by the broken lines in FIGS. The opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted. Since the switching mechanism 3 is in a heating operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is closed, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is opened. As a result, the intermediate heat exchanger 7 is not allowed to function as a cooler. Further, the first second-stage injection on / off valve 18d is opened. Here, in order to explain the heating operation in the state where both the first compression unit 103 and the second compression unit 104 are activated as an example, the rear-stage intake valve 85a is opened and the late compression unit activation valve 86a is closed. It is made to the state that was made. However, in the heating operation in a state where only the first compression unit 103 is activated, the rear-stage suction valve 85a and the subsequent compression unit activation valve 86a are closed (see FIG. 9).

  In the state of the refrigerant circuit 10, low-pressure refrigerant (see point A in FIGS. 1 and 5 to 7) is sucked into the compression mechanism 102 from the suction mother pipe 102a, and is first intermediated by the front-stage compression elements 103c and 104c. After being compressed to a pressure, it is discharged to the inlet side intermediate branch pipes 81 and 84 of the intermediate refrigerant pipe 8 and merges in the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 through the check mechanisms 81a and 84a (FIGS. 1 and 5). -See point B in FIG. Unlike the cooling operation described above, the intermediate-pressure refrigerant discharged from the preceding-stage compression elements 103c and 104c and joined in the intermediate refrigerant pipe 8 does not pass through the intermediate heat exchanger 7 (that is, is cooled). Without passing through the intermediate heat exchanger bypass pipe 9 (see point C in FIGS. 1 and 5 to 7). The intermediate-pressure refrigerant that has passed through the intermediate heat exchanger bypass pipe 9 without being cooled by the intermediate heat exchanger 7 is returned to the rear-stage compression elements 103d and 104d from the receiver 18 through the first rear-stage injection pipe 18c. (Refer to the point M in FIG. 1 and FIGS. 5 to 7) to cool it (see the point G in FIGS. 1 and 5 to 7). Next, the intermediate-pressure refrigerant that has joined with the refrigerant returning from the first rear-stage injection pipe 18c (that is, the intermediate-pressure injection by the receiver 18 as a gas-liquid separator) is the middle of the intermediate refrigerant pipe 8 at the outlet side. Branches into branch pipes 83 and 85. The intermediate-pressure refrigerant branched from the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 to the outlet-side intermediate branch pipes 83 and 85 is supplied to the rear-stage compression elements 103d and 104d connected to the rear-stage side of the front-stage compression elements 103c and 104c. The air is sucked and further compressed, and is discharged from the compression portions 103 and 104 to the discharge branch pipes 103b and 104b (see point D in FIGS. 1 and 5 to 7). Here, the high-pressure refrigerant discharged from the compression units 103 and 104 is subjected to the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 6) by the two-stage compression operation by the compression elements 103c, 104c, 103d, and 104d. ) Compressed to a pressure exceeding The high-pressure refrigerant discharged from the first compression unit 103 flows into the first oil separator 141a constituting the first oil separation mechanism 141, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the first oil separator 141a flows into the first oil return pipe 141b constituting the first oil separation mechanism 141, and the first oil return pipe 141b is provided with the first oil return pipe 141b. After being depressurized by the first depressurization mechanism 141 c, it is returned to the second suction branch pipe 104 a of the second compression unit 104 and again sucked into the compression mechanism 102. Further, the high-pressure refrigerant discharged from the second compression unit 104 flows into the second oil separator 143a constituting the second oil separation mechanism 143, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the second oil separator 143a flows into the second oil return pipe 143b that constitutes the second oil separation mechanism 143, and is supplied to the second oil return pipe 143b. After the pressure is reduced by the second pressure reducing mechanism 143 c, the pressure is returned to the first suction branch pipe 103 a of the first compression unit 103 and is again sucked into the compression mechanism 102. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanisms 141 and 143 merges in the discharge mother pipe 102b after passing through the check mechanisms 142 and 144, and passes through the switching mechanism 3 to be a refrigerant radiator. It is sent to the use side heat exchanger 6 that functions as a cooling source, and is cooled by exchanging heat with water or air as a cooling source (see point F in FIG. 1 and FIGS. The high-pressure refrigerant cooled in the use-side heat exchanger 6 flows into the receiver inlet pipe 18a through the inlet check valve 17b of the bridge circuit 17, and is reduced to the vicinity of the intermediate pressure by the first expansion mechanism 5a. Gas and liquid separation is performed while being temporarily stored inside (see points I, L, and M in FIGS. 1 and 5 to 7). The gas refrigerant separated from the gas and liquid in the receiver 18 is extracted from the upper part of the receiver 18 by the first second-stage injection pipe 18c, and is discharged from the first-stage compression elements 103c and 104c as described above. Will join the refrigerant. Then, the liquid refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is decompressed by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve of the bridge circuit 17 It is sent to the heat source side heat exchanger 4 functioning as an evaporator of the refrigerant through 17d (see point E in FIGS. 1 and 5 to 7). The low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated and evaporated in the heat source side heat exchanger 4 by exchanging heat with water or air as a heating source. (Refer to point A in FIGS. 1 and 5 to 7). The low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 is again sucked into the compression mechanism 102 via the switching mechanism 3. In this way, the heating operation is performed.

  Thus, in the air conditioning apparatus 1 (refrigeration apparatus) of the present embodiment, the intermediate refrigerant pipe 8 is provided to allow the refrigerant discharged from the front-stage compression elements 103c and 104c to be sucked into the rear-stage compression elements 103d and 104d. When the intermediate heat exchanger 7 is in the heating operation, the intermediate heat exchanger on / off valve 12 is closed and the intermediate heat exchanger bypass on / off valve 11 is opened so that the intermediate heat exchanger 7 does not function as a cooler. Therefore, the downstream compression element 103d by performing intermediate pressure injection by the receiver 18 as a gas-liquid separator that branches the refrigerant radiated in the heat source side heat exchanger 4 and returns it to the downstream compression elements 103d and 104d. 104d is only the cooling effect of the refrigerant sucked in, and the intermediate heat exchanger on / off valve 12 and the intermediate heat exchanger bypass on / off valve 11 are not provided. When only the cooler 7 is provided or when the intermediate heat exchanger 7 is made to function as a cooler as in the above-described cooling operation (in this case, in FIGS. 6 and 7, point A → point B → point C ′ → Refrigeration cycle is performed in the order of point G ′ → point D ′ → point F → point I → point L → point E), heat radiation from the intermediate heat exchanger 7 to the outside is prevented, and rear side compression A decrease in the temperature of the refrigerant sucked into the elements 103d and 104d is suppressed (see points G and G ′ in FIG. 7), and a decrease in the temperature of the refrigerant finally discharged from the compression mechanism 102 can be suppressed (see FIG. 7). 7 points D and D ′). Thereby, in this air conditioning apparatus 1, during heating operation, heat radiation to the outside is suppressed, and it can be used in the use-side heat exchanger 6 that functions as a refrigerant radiator to prevent a decrease in operating efficiency. Can do.

<Starting the compression mechanism>
Next, the operation at the time of starting the compression mechanism 102 when performing the cooling operation or the heating operation as described above will be described by taking the cooling operation as an example. Here, the air conditioning apparatus 1 of the present embodiment has a configuration in which the first compression unit 103 that can vary the operation capacity is operated more preferentially than the second compression unit 104 as described above. Specifically, when the compression mechanism 102 is activated, as shown in FIG. 9, first, the first compression unit 103 is activated, and the second compression unit 104 is stopped. Here, in a state where only the first compression unit 103 is activated, the rear-stage suction valve 85a and the subsequent compression unit activation valve 86a are closed.

  First, in the case where only the first compression unit 103 is activated, if a request to increase the air conditioning capacity is made, if the operating frequency of the first compression unit 103 has a margin with respect to the maximum frequency, the first An operation for increasing the operating frequency of the compression unit 103 is performed. However, even if the operating frequency of the first compression unit 103 is set to the maximum frequency, the activation of the second compression unit 104 is requested when the air conditioning capacity is insufficient. If it is determined in step S1 that there has been a request for activation of the second compression unit 104, the process proceeds to subsequent compression unit activation control in steps S2 to S4.

  Next, in step S2, when the second compression unit 104 is activated, the flow rate of the refrigerant increases significantly compared to the flow rate of the refrigerant discharged from the compression mechanism 102 when only the first compression unit 103 is activated. In order to prevent this, the operation frequency of the first compression unit 103 is lowered before starting the second compression unit 104 by lowering the operation frequency of the first compression unit 103 to the lowest frequency. At this time, the opening degree of the first second-stage injection on / off valve 18c is reduced (here, the open state is changed to the fully-closed state) to return to the intermediate refrigerant pipe 8 through the first second-stage injection pipe 18c. (Refer to FIG. 9 in which the arrow indicating the flow of the refrigerant returning to the intermediate refrigerant pipe 8 through the first second-stage injection pipe 18c is eliminated.) Corresponding to).

  Here, if only the operation of lowering the operation capacity of the first compression unit 103 is performed prior to the activation of the second compression unit 104, the discharge is performed from the first pre-stage compression element 103c of the first compression unit 103. Since the flow rate of the refrigerant to be reduced decreases, the flow rate of the refrigerant returned from the first second-stage injection pipe 18c to the intermediate refrigerant pipe 8 is relatively higher than the flow rate of the refrigerant flowing through the intermediate refrigerant pipe 8. Thus, there is a possibility that the refrigerant sucked into the first second-stage compression element 103d of the first compression unit 103 may temporarily become wet, which causes a problem that the reliability of the apparatus is lowered.

  However, when the operating capacity of the first compression unit 103 is reduced prior to the activation of the second compression unit 104 as in step S2, the opening of the first second-stage injection on / off valve 18d is reduced (here, Although the flow rate of the refrigerant discharged from the first front-stage compression element 103c of the first compressor 103 is reduced by changing from the open state to the fully-closed state), the intermediate refrigerant is supplied from the first rear-stage injection pipe 18c. Avoiding a state where the flow rate of the refrigerant returned to the pipe 8 is higher than the flow rate of the refrigerant flowing through the intermediate refrigerant pipe 8, and suppressing the refrigerant sucked into the first second-stage compression element from becoming wet. As a result, the reliability of the apparatus can be improved.

  Next, in step S3, the second compression unit 104 is activated in a state in which the later compression unit activation valve 86a is opened (because it is before activation of the second compression unit 104, the rear-stage intake valve 85a is closed). By performing this operation, the refrigerant discharged from the second pre-stage compression element 104c of the second compression unit 104 is not merged with the refrigerant discharged from the first pre-stage compression element 103c of the first compression unit 103. Then, the refrigerant flows through the start bypass pipe 86 so as to be sucked into the second rear-stage compression element 104d of the second compression unit 104 (see FIG. 10).

  Here, as in the state where both of the two compression units 103 and 104 are activated, the second compression unit 104 is opened with the rear-stage suction valve 85a opened and the subsequent compression unit activation valve 86a closed. Is started, after the refrigerant discharged from the first front-stage compression element 103c and the refrigerant discharged from the second front-stage compression element 103c are once merged by the intermediate refrigerant pipe 8, the first second-stage compression element Due to the branching into the suction side of 103d and the suction side of the second second-stage compression element 104d, the discharge side and the second of the second front-stage compression element 104c of the second compression unit 104 are branched. The suction side of the second-stage compression element 104d is connected to the pressure on the discharge side of the first first-stage compression element 103c of the first compressor 103 and the suction-side of the first second-stage compression element 103d. Made from a state in which the influence of the force to start the second compression unit 104, it is difficult to start the second compression unit 104 stably.

  However, as in step S3, the second compression unit 104 is activated by starting the second compression unit 104 in a state in which the subsequent compression unit activation valve 86a is opened (and the rear-stage suction valve 85a is closed). The discharge side of the second front-stage compression element 104c of the section 104 and the suction side of the second rear-stage compression element 104d are the pressure on the discharge side of the first front-stage compression element 103c of the first compression section 103 and the first rear-stage compression element 103d. The state under the influence of the suction side pressure can be relaxed, and the second compression unit 104 is stably activated when the second compression unit 104 is activated in the state where the first compression unit 103 is activated. can do.

  Then, the second compression unit 104 is stably activated such that a predetermined time has elapsed since the activation of the second compression unit 104, or that the pressure sensors 54, 60, etc. around the compression mechanism 102 are stabilized within a predetermined pressure range. Then, in step S4, the rear-stage intake valve 85a is opened, the subsequent compression section start valve 86a is closed, and the opening degree of the first second-stage injection on / off valve 18d is increased (here, the fully closed state). The refrigerant discharged from the second pre-stage compression element 104c of the second compression unit 104 and the refrigerant discharged from the first pre-stage compression element 103c of the first compression unit 103. The flow rate of the refrigerant returned from the first second-stage injection pipe 18c to the intermediate mother pipe 82 is changed to the second-stage intake valve 85a and the rear Closed state of the compression unit boot valve 86a is in the appropriate that is considered (see FIG. 2).

  Here, even after the second compression unit 104 is activated, the first-stage suction valve 85a is opened, and the first compression unit activation valve 86a is closed. Refrigerant discharged from the first front-stage compression element 103c and refrigerant discharged from the second front-stage compression element 104c when the opening of the rear-stage injection on-off valve 18d is kept small (here, fully closed). Both of them join together and flow through the intermediate mother pipe 82 of the intermediate refrigerant pipe 8, compared with the flow rate of the refrigerant flowing through the intermediate mother pipe 82, from the first rear-stage injection pipe 18 c to the intermediate mother pipe. Since the flow rate of the refrigerant returned to 82 is relatively small, the effect of reducing the power consumption of the compression mechanism 102 due to the intermediate pressure injection and improving the operation efficiency cannot be obtained sufficiently. Therefore, in order to avoid such a state, the opening degree of the first second-stage injection on / off valve 18d is immediately increased after the second compression unit 104 is activated (here, all It is desirable that the flow rate of the refrigerant returned from the first second-stage injection pipe 18c to the intermediate refrigerant pipe 8 is increased.

  However, even after the second compression unit 104 is activated, the rear side suction valve 85a is closed and the subsequent compression unit activation valve 86a is opened (ie, the process of step S3 is performed). If the first second-stage injection on / off valve 18d is enlarged in the state before the shift to the normal operation immediately after the start of the second compression unit 104, such as after the operation, the intermediate mother of the intermediate refrigerant pipe 8 Although the refrigerant flowing through the pipe 82 is only the refrigerant discharged from the first front-stage compression element 103c, the flow rate of the refrigerant returned from the first rear-stage injection pipe 18c to the intermediate mother pipe 82 increases. Therefore, the flow rate of the refrigerant returned from the first second-stage injection pipe 18c to the intermediate mother pipe 82 is relatively higher than the flow rate of the refrigerant flowing through the intermediate mother pipe 82, and the first compression unit There is a possibility that the refrigerant is wet state sucked into 03 of the first-stage compression element 103d.

  Thus, as in step S4, even after the second compression unit 104 is activated, the second-stage suction valve 85a is closed and the subsequent compression unit activation valve 86a is opened. The opening degree of the first second-stage injection on / off valve 18d is not increased when the second-stage suction valve 85a is opened and the second-compressor starting valve 86a is closed without increasing the opening degree of the first second-stage injection on / off valve 18d. By enlarging the refrigerant, the refrigerant sucked into the first second-stage compression element 104d is in a wet state even when the second compression section 104 is activated with the opening / closing control of the second-stage suction valve 85a and the second-stage compression section activation valve 86a. And the refrigerant quickly returned from the first second-stage injection pipe 18c to the intermediate mother pipe 82 when the operation state is shifted to a normal operation state (here, cooling operation). Thereby increasing the flow rate.

  Further, in the air conditioner 1 of the present embodiment, the intermediate heat exchanger 7 is provided in the intermediate mother pipe 82 constituting the intermediate refrigerant pipe 8, and the refrigerant flowing through the intermediate mother pipe 82 is supplied to the first second-stage injection pipe. Before joining the refrigerant returned from 18c to the intermediate mother pipe 82, the refrigerant is cooled more than the state discharged from the front-stage compression elements 103c, 104c, so that the intermediate mother pipe 82 is discharged from the first rear-stage injection pipe 18c. There is a high possibility that the refrigerant sucked into the downstream compression elements 103d and 104d after joining the refrigerant returned to the wet state will be in a wet state, but prior to starting the second compression unit 104 as in step S2 described above. When the operating capacity of the first compression unit 103 is reduced, the opening degree of the first second-stage injection on / off valve 18d is made small. In this manner, the second-stage compression valve 104a is closed and the second compression section 104 is started with the second-stage compression section start valve 86a opened. After the second compression section 104 is started, the second-stage suction valve 85a is opened. In addition, after the second compression unit 104 is stably activated by closing the later compression unit activation valve 86a, the rear stage suction valve 85a is opened and the later compression unit activation valve 86a is closed. At this time, since the opening degree of the first second-stage injection on / off valve 18d is increased, the refrigerant flowing through the intermediate mother pipe 82 merges with the refrigerant returned from the first second-stage injection pipe 18c to the intermediate mother pipe 82. The refrigerant sucked into the first second-stage compression element 104c becomes damp even though the refrigerant is cooled more than the state discharged from the first-stage compression elements 103c, 104c. So that the can be suppressed to become state.

  In addition, since the intermediate heat exchanger 7 is not used as a cooler when the compression mechanism 102 is started during the heating operation, the first after the refrigerant is returned to the intermediate mother pipe 82 from the first second-stage injection pipe 18c. Although the possibility that the refrigerant sucked into the rear-stage compression element 103d becomes wet is lower than that at the time of starting the compression mechanism 102 during the cooling operation, basically, the cooling operation is performed. The same effect as when the compression mechanism 102 is started can be obtained.

(3) Modification 1
In the above-described embodiment, in the air conditioner 1 configured to be able to switch between the cooling operation and the heating operation by the switching mechanism 3, the first second-stage injection for performing intermediate pressure injection by the receiver 18 as a gas-liquid separator. A pipe 18c is provided to perform intermediate pressure injection by a receiver 18 as a gas-liquid separator. Instead of the intermediate pressure injection by the receiver 18, a second rear-stage injection pipe 19 and an economizer heat exchanger 20 are provided. It is conceivable that intermediate pressure injection by the economizer heat exchanger 20 is performed.

  For example, as shown in FIG. 11, in the above-described embodiment, instead of the first second-stage injection pipe 18c, the refrigerant circuit 110 provided with the second second-stage injection pipe 19 and the economizer heat exchanger 20 is provided. can do.

  Here, the second second-stage injection pipe 19 has a function of branching the refrigerant that has dissipated heat in the heat source-side heat exchanger 4 or the use-side heat exchanger 6 and returning it to the second-stage compression elements 103d and 104d of the compression mechanism 102. ing. In this modification, the second second-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 second-stage compression elements 103d and 104d. More specifically, the second rear-stage injection pipe 19 is positioned on the upstream side of the first 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 The refrigerant is branched from the exchanger 4 and the first expansion mechanism 5a and between the use side heat exchanger 6 and the first expansion mechanism 5a when the switching mechanism 3 is in the heating operation state. The intermediate mother pipe 82 is provided so as to return to a position downstream of the intermediate heat exchanger 7. The second second-stage injection pipe 19 is provided with a second second-stage injection valve 19a capable of opening degree control. In the present modification, the second second-stage injection valve 19a is an electric expansion valve.

  Further, the economizer heat exchanger 20 includes the refrigerant that has radiated heat in the heat source side heat exchanger 4 or the use side heat exchanger 6 and the refrigerant that flows through the second second-stage injection pipe 19 (more specifically, the second second-stage injection valve). 19a is a heat exchanger that performs heat exchange with the refrigerant after being reduced in pressure to near the intermediate pressure. In this modification, the economizer heat exchanger 20 is positioned upstream of the first 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 Between the first 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 first expansion mechanism 5a) and the second rear side It is provided so as to perform heat exchange with the refrigerant flowing through the injection pipe 19 and has a flow path through which both refrigerants face each other. In this modification, the economizer heat exchanger 20 is provided on the upstream side of the second rear-stage injection pipe 19 of the receiver inlet pipe 18a. For this reason, the refrigerant that has radiated heat in the heat source side heat exchanger 4 or the use side heat exchanger 6 is branched into the second rear-stage 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 second second-stage injection pipe 19.

  An economizer outlet temperature sensor 55 that detects the refrigerant temperature at the outlet of the economizer heat exchanger 20 on the second rear-stage injection pipe 19 side is provided at the outlet of the economizer heat exchanger 20 on the second rear-stage injection pipe 19 side. Is provided.

  Next, operation | movement of the air conditioning apparatus 1 of this modification is demonstrated using FIGS. 11-17. Here, FIG. 12 is a diagram showing the flow of the refrigerant in the air conditioning apparatus 1 during the cooling operation, and FIG. 13 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the cooling operation. FIG. 15 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation, FIG. 15 is a diagram illustrating the flow of refrigerant in the air conditioner 1 during heating operation, and FIG. 16 is during heating operation. FIG. 17 is a pressure-enthalpy diagram illustrating the refrigeration cycle, and FIG. 17 is a temperature-entropy diagram illustrating the refrigeration cycle during the heating operation. Note that the following cooling operation, heating operation, and operation control in starting the compression mechanism are 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, D ′, E, and H in FIGS. 12 and 13, and points D, D ′, F, and FIGS. 16 and 17). “Low pressure” means the low pressure in the refrigeration cycle (that is, the pressure at points A and F in FIGS. 13 and 14 and the pressure at points A and E in FIGS. 16 and 17). “Pressure” means an intermediate pressure in the refrigeration cycle (that is, pressure at points B, C, C ′, G, G ′, J, and K in FIGS. 13, 14, 16, and 16).

<Cooling operation>
During the cooling operation, the switching mechanism 3 is in a cooling operation state indicated by a solid line in FIGS. The opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted. Since the switching mechanism 3 is in the cooling operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is opened, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is closed. Thus, the intermediate heat exchanger 7 is brought into a state of functioning as a cooler. Further, the opening degree of the second second-stage injection valve 19a is adjusted. More specifically, in this modification, the second rear-stage injection valve 19a has an opening degree so that the degree of superheat of the refrigerant at the outlet of the economizer heat exchanger 20 on the second rear-stage injection pipe 19 side becomes a target value. So-called superheat control is performed. In this modification, the superheat degree of the refrigerant at the outlet of the economizer heat exchanger 20 on the second post-stage injection pipe 19 side is obtained by converting the intermediate pressure detected by the intermediate pressure sensor 54 into the saturation temperature, and the economizer outlet temperature sensor 55. This is obtained by subtracting the saturation temperature value of the refrigerant from the refrigerant temperature detected by the above. Although not adopted in this modification, a temperature sensor is provided at the inlet of the economizer heat exchanger 20 on the second rear-stage injection pipe 19 side, and the refrigerant temperature detected by this temperature sensor is used as the economizer outlet temperature sensor 55. The degree of superheat of the refrigerant at the outlet of the economizer heat exchanger 20 on the second rear-stage injection pipe 19 side may be obtained by subtracting from the refrigerant temperature detected by the above. Further, the opening degree adjustment of the second second-stage injection valve 19a is not limited to the superheat degree control, and for example, the opening degree is adjusted by a predetermined opening amount according to the refrigerant circulation amount in the refrigerant circuit 110. Also good. Here, in order to explain the cooling operation in the state where both the first compression unit 103 and the second compression unit 104 are activated as an example, the rear-stage suction valve 85a is opened, and the subsequent compression unit activation valve 86a is closed. It is made to the state that was made. However, in the cooling operation in a state where only the first compression unit 103 is activated, the rear-stage suction valve 85a and the subsequent compression unit activation valve 86a are closed.

  In the state of the refrigerant circuit 110, a low-pressure refrigerant (see point A in FIGS. 11 to 14) is sucked into the compression mechanism 102 from the suction mother pipe 102a, and is first compressed to an intermediate pressure by the pre-stage compression elements 103c and 104c. After that, the refrigerant is discharged to the inlet side intermediate branch pipes 81 and 84 of the intermediate refrigerant pipe 8 and merges in the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 through the check mechanisms 81a and 84a (point B in FIGS. 11 to 14). reference). The intermediate-pressure refrigerant discharged from the preceding-stage compression elements 103c and 104c and joined in the intermediate refrigerant pipe 8 is cooled in the intermediate heat exchanger 7 by exchanging heat with water or air as a cooling source ( (See point C in FIGS. 11-14). The refrigerant cooled in the intermediate heat exchanger 7 is further cooled by joining with the refrigerant (see point K in FIGS. 11 to 14) returned from the second second-stage injection pipe 19 to the second-stage compression elements 103d and 104d. (See point G in FIGS. 11 to 14). Next, the intermediate-pressure refrigerant that has joined with the refrigerant returning from the second rear-stage injection pipe 19 (that is, the intermediate-pressure injection by the economizer heat exchanger 20) is the outlet-side intermediate branch pipe 83 of the intermediate refrigerant pipe 8. , 85. The intermediate-pressure refrigerant branched from the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 to the outlet-side intermediate branch pipes 83 and 85 is supplied to the rear-stage compression elements 103d and 104d connected to the rear-stage side of the front-stage compression elements 103c and 104c. The air is sucked and further compressed, and is discharged from the compression parts 103 and 104 to the discharge branch pipes 103b and 104b (see point D in FIGS. 11 to 14). Here, the high-pressure refrigerant discharged from the compression units 103 and 104 is subjected to the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 13) by the two-stage compression operation by the compression elements 103c, 104c, 103d, and 104d. ) Compressed to a pressure exceeding The high-pressure refrigerant discharged from the first compression unit 103 flows into the first oil separator 141a constituting the first oil separation mechanism 141, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the first oil separator 141a flows into the first oil return pipe 141b constituting the first oil separation mechanism 141, and the first oil return pipe 141b is provided with the first oil return pipe 141b. After being depressurized by the first depressurization mechanism 141 c, it is returned to the second suction branch pipe 104 a of the second compression unit 104 and again sucked into the compression mechanism 102. Further, the high-pressure refrigerant discharged from the second compression unit 104 flows into the second oil separator 143a constituting the second oil separation mechanism 143, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the second oil separator 143a flows into the second oil return pipe 143b that constitutes the second oil separation mechanism 143, and is supplied to the second oil return pipe 143b. After the pressure is reduced by the second pressure reducing mechanism 143 c, the pressure is returned to the first suction branch pipe 103 a of the first compression unit 103 and is again sucked into the compression mechanism 102. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanisms 141 and 143 passes through the check mechanisms 142 and 144 and then merges in the discharge mother pipe 102b. It is sent to the heat source side heat exchanger 4 functioning as Then, the high-pressure refrigerant sent to the heat source side heat exchanger 4 is cooled by exchanging heat with water or air as a cooling source in the heat source side heat exchanger 4 (point E in FIGS. 11 to 14). reference). 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 second second-stage injection pipe 19. . And the refrigerant | coolant which flows through the 2nd back | latter stage side injection pipe 19 is sent to the economizer heat exchanger 20 after depressurizing to the intermediate pressure vicinity in the 2nd back | latter stage | side injection valve 19a (refer the point J of FIGS. 11-14). . In addition, the refrigerant after being branched to the second second-stage injection pipe 19 flows into the economizer heat exchanger 20, and is cooled by exchanging heat with the refrigerant flowing through the second second-stage injection pipe 19 (FIGS. 11 to 11). (See point H in FIG. 14). On the other hand, the refrigerant flowing through the second second-stage injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator (see point K in FIGS. 11 to 14). ), As described above, the refrigerant is joined to the intermediate-pressure refrigerant discharged from the preceding-stage compression elements 103c and 104c. Then, the high-pressure refrigerant cooled in the economizer heat exchanger 20 is decompressed to near the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 18 (see point I in FIGS. 11 and 12). Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is decompressed by the second 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 used. And is sent to the use side heat exchanger 6 functioning as a refrigerant evaporator (see point F in FIGS. 11 to 14). And the refrigerant | coolant of the low pressure gas-liquid two-phase state sent to the utilization side heat exchanger 6 will be heated by performing heat exchange with water and air as a heating source, and will evaporate (FIGS. 11-FIG. 11). 14 point A). Then, the low-pressure refrigerant heated in the use side heat exchanger 6 is again sucked into the compression mechanism 102 via the switching mechanism 3. In this way, the cooling operation is performed.

  As described above, in the air conditioner 1 of the present modification, the second rear-stage injection pipe 19 is provided instead of the first rear-stage injection pipe 18c, and the refrigerant that has radiated heat in the heat source side heat exchanger 4 is branched to be rear-stage. Although the point that the intermediate pressure injection is performed by the economizer heat exchanger 20 that returns to the side compression elements 103d and 104d is different, it is possible to obtain the same effects as the above-described embodiment during the cooling operation.

<Heating operation>
During the heating operation, the switching mechanism 3 is in the heating operation state indicated by the broken lines in FIGS. The opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted. Since the switching mechanism 3 is in a heating operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is closed, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is opened. As a result, the intermediate heat exchanger 7 is not allowed to function as a cooler. Further, the opening degree of the second second-stage injection valve 19a is adjusted in the same manner as in the cooling operation. Here, in order to explain the heating operation in the state where both the first compression unit 103 and the second compression unit 104 are activated as an example, the rear-stage intake valve 85a is opened and the late compression unit activation valve 86a is closed. It is made to the state that was made. However, in the heating operation in a state where only the first compression unit 103 is activated, the rear-stage suction valve 85a and the subsequent compression unit activation valve 86a are closed.

  In the state of the refrigerant circuit 110, a low-pressure refrigerant (see point A in FIGS. 11 and 15 to 17) is sucked into the compression mechanism 102 from the suction mother pipe 102a, and is first intermediated by the front-stage compression elements 103c and 104c. After being compressed to a pressure, the refrigerant is discharged to the inlet side intermediate branch pipes 81 and 84 of the intermediate refrigerant pipe 8 and merges in the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 through the check mechanisms 81a and 84a (FIGS. 11 and 15). -See point B in FIG. Unlike the cooling operation described above, the intermediate-pressure refrigerant discharged from the preceding-stage compression elements 103c and 104c and joined in the intermediate refrigerant pipe 8 does not pass through the intermediate heat exchanger 7 (that is, is cooled). Without passing through the intermediate heat exchanger bypass pipe 9 (see point C in FIGS. 11 and 15 to 17). The intermediate-pressure refrigerant that has passed through the intermediate heat exchanger bypass pipe 9 without being cooled by the intermediate heat exchanger 7 is returned from the second rear-stage injection pipe 19 to the rear-stage compression elements 103d and 104d (FIG. 11). 15 (see point K in FIGS. 15 to 17) and further cooling (see point G in FIGS. 11 and 15 to 17). Next, the intermediate-pressure refrigerant that has joined with the refrigerant returning from the second rear-stage injection pipe 19 (that is, the intermediate-pressure injection by the economizer heat exchanger 20) is the outlet-side intermediate branch pipe 83 of the intermediate refrigerant pipe 8. , 85. The intermediate-pressure refrigerant branched from the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 to the outlet-side intermediate branch pipes 83 and 85 is supplied to the rear-stage compression elements 103d and 104d connected to the rear-stage side of the front-stage compression elements 103c and 104c. The air is sucked and further compressed, and is discharged from the compression units 103 and 104 to the discharge branch pipes 103b and 104b (see point D in FIGS. 11 and 15 to 17). Here, the high-pressure refrigerant discharged from the compression units 103 and 104 is subjected to the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 16) by the two-stage compression operation by the compression elements 103c, 104c, 103d, and 104d. ) Compressed to a pressure exceeding The high-pressure refrigerant discharged from the first compression unit 103 flows into the first oil separator 141a constituting the first oil separation mechanism 141, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the first oil separator 141a flows into the first oil return pipe 141b constituting the first oil separation mechanism 141, and the first oil return pipe 141b is provided with the first oil return pipe 141b. After being depressurized by the first depressurization mechanism 141 c, it is returned to the second suction branch pipe 104 a of the second compression unit 104 and again sucked into the compression mechanism 102. Further, the high-pressure refrigerant discharged from the second compression unit 104 flows into the second oil separator 143a constituting the second oil separation mechanism 143, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the second oil separator 143a flows into the second oil return pipe 143b that constitutes the second oil separation mechanism 143, and is supplied to the second oil return pipe 143b. After the pressure is reduced by the second pressure reducing mechanism 143 c, the pressure is returned to the first suction branch pipe 103 a of the first compression unit 103 and is again sucked into the compression mechanism 102. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanisms 141 and 143 merges in the discharge mother pipe 102b after passing through the check mechanisms 142 and 144, and passes through the switching mechanism 3 to be a refrigerant radiator. It is sent to the use side heat exchanger 6 that functions as a cooling source, and is cooled by exchanging heat with water or air as a cooling source (see point F in FIGS. 11 and 15 to 17). The high-pressure refrigerant cooled in the use-side heat exchanger 6 flows into the receiver inlet pipe 18a through the inlet check valve 17b of the bridge circuit 17, and a part of the refrigerant is branched to the second second-stage injection pipe 19. . And the refrigerant | coolant which flows through the 2nd back | latter stage side injection pipe 19 is sent to the economizer heat exchanger 20, after being pressure-reduced to the intermediate pressure vicinity in the 2nd back | latter stage | side injection valve 19a (point of FIG. 11, FIG. 15-17). J). Further, the refrigerant after being branched into the second second-stage injection pipe 19 flows into the economizer heat exchanger 20, and is cooled by exchanging heat with the refrigerant flowing through the second second-stage injection pipe 19 (FIG. 11, (See point H in FIGS. 15 to 17). On the other hand, the refrigerant flowing through the second second-stage injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator (see FIGS. 11 and 15 to 17). As described above, the intermediate pressure refrigerant discharged from the pre-stage compression elements 103c and 104c is joined as described above. Then, the high-pressure refrigerant cooled in the economizer heat exchanger 20 is decompressed to near the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 18 (see point I in FIGS. 11 and 15). Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is reduced in pressure by the second 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. And is sent to the heat source side heat exchanger 4 functioning as a refrigerant evaporator (see point E in FIGS. 11 and 15 to 17). The low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated and evaporated in the heat source side heat exchanger 4 by exchanging heat with water or air as a heating source. (Refer to point A in FIGS. 11 and 15 to 17). The low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 is again sucked into the compression mechanism 102 via the switching mechanism 3. In this way, the heating operation is performed.

  As described above, in the air conditioner 1 of this modification, the second rear-stage injection pipe 19 is provided instead of the first rear-stage injection pipe 18c, and the refrigerant that has radiated heat in the heat source side heat exchanger 4 is branched to the rear stage. Although the point that the intermediate pressure injection is performed by the economizer heat exchanger 20 that returns to the side compression elements 103d and 104d is different, the same effect as the above-described embodiment can be obtained during the heating operation.

<Starting the compression mechanism>
The air conditioner 1 of this modification is different in that the second second-stage injection valve 19a is used instead of the first second-stage injection on / off valve 18d, but basically the same compression as that of the above-described embodiment. The operation at the time of starting the mechanism 102 can be performed.

  However, since the opening degree of the second second-stage injection valve 19a can be adjusted, when the opening degree of the second second-stage injection valve 19a is reduced in step S2 shown in FIG. It is possible to set the opening at which intermediate pressure injection is performed in an amount commensurate with the flow rate of the refrigerant flowing through the intermediate refrigerant pipe 8 in a state where the operation frequency of 103 is lowered. For example, the flow rate of the refrigerant flowing through the intermediate refrigerant pipe 8 is reduced when the opening of the second second-stage injection valve 19a is lowered from the operating frequency immediately before performing the operation of lowering the operating frequency of the first compression unit 103 to the lowest frequency. The opening degree corresponding to the minute can be made smaller than the opening degree immediately before the operation of lowering the operating frequency of the first compression unit 103 is performed. Further, in step S4 shown in FIG. 8, when the opening degree of the second second-stage injection valve 19a is increased, the increase in the flow rate of the refrigerant flowing through the intermediate refrigerant pipe 8 due to the starting operation of the second compression unit 104 is increased. It can be set to an opening at which a suitable amount of intermediate pressure injection is performed. For example, the opening amount of the second second-stage injection valve 19a is set to the second compression unit by an opening amount corresponding to the increase in the flow rate of the refrigerant flowing through the intermediate refrigerant pipe 8 when the second compression unit 104 is started. The opening degree immediately before the start operation 104 can be made larger. Thus, in this modification, intermediate pressure injection according to the flow rate of the refrigerant flowing through the intermediate refrigerant pipe 8 can be performed even in a transient control state such as steps S2 to S4 shown in FIG.

(4) Modification 2
The refrigerant circuits 10 and 110 (see FIGS. 1 and 11) in the above-described embodiment and its modifications have a configuration including one use side heat exchanger 6, but according to the air conditioning load of a plurality of air conditioning spaces. In order to perform cooling or heating, the configuration includes a plurality of usage-side heat exchangers 6 connected in parallel to each other, and the flow rate of the refrigerant flowing through each usage-side heat exchanger 6 is controlled. In order to obtain the refrigeration load required in the use side heat exchanger 6, each use side heat exchanger 6 is provided between the receiver 18 as a gas-liquid separator and the use side heat exchanger 6. It is conceivable that the use-side expansion mechanism 5c is provided so as to correspond to the above.

  For example, although not shown in detail, in the refrigerant circuit 10 (see FIG. 1) having the bridge circuit 17 in the above-described embodiment, a plurality (here, two) of use side heat exchangers 6 connected in parallel to each other. And a utilization side expansion mechanism so as to correspond to each utilization side heat exchanger 6 between the receiver 18 (more specifically, the bridge circuit 17) as a gas-liquid separator and the utilization side heat exchanger 6. 5c (see FIG. 18), the second expansion mechanism 5b provided in the receiver outlet pipe 18b is deleted, and instead of the outlet check valve 17d of the bridge circuit 17, it is reduced to a low pressure in the refrigeration cycle during heating operation. It is conceivable to provide a third expansion mechanism (not shown) that depressurizes the refrigerant.

  And while having the some utilization side heat exchanger 6 mutually connected in parallel with such, the receiver 18 as a gas-liquid separator and a utilization side heat exchanger so that it may respond | correspond to each utilization side heat exchanger 6 A utilization side expansion mechanism 5c as a utilization side expansion valve is provided between the utilization side expansion mechanism 5c and the utilization side expansion mechanism 5c so that a refrigeration load required in each utilization side heat exchanger 6 can be obtained. In the configuration in which the flow rate of the refrigerant flowing through each use side heat exchanger 6 is controlled, in the heating operation in which the switching mechanism 3 is in the heating operation state, the flow rate of the refrigerant passing through each use side heat exchanger 6 is Although it is generally determined by the opening degree of the use side expansion mechanism 5c provided on the downstream side of the use side heat exchanger 6 and on the upstream side of the receiver 18, the opening degree of each use side expansion mechanism 5c is determined at this time. Is the refrigerant flowing through each use side heat exchanger 6 It varies depending not only on the flow rate but also on the state of flow distribution among the plurality of use side heat exchangers 6, resulting in a state in which the opening degree differs greatly among the plurality of use side expansion mechanisms 5 c, or the use side expansion mechanism 5 c. May have a relatively small opening. For this reason, the pressure in the receiver 18 as a gas-liquid separator may be lowered by opening control of the use side expansion mechanism 5c during heating operation. Further, in such an air conditioner 1, a heat source unit mainly including the compression mechanism 102, the heat source side heat exchanger 4 and the receiver 18 and a utilization unit mainly including the utilization side heat exchanger 6 are connected by a communication pipe. When configured as a separate type air conditioner, depending on the arrangement of the utilization unit and the heat source unit, this connecting pipe may become very long, so that a drop due to the pressure loss is also added. The pressure at will drop. Thus, the intermediate pressure injection by the receiver 18 as a gas-liquid separator can be used even under a condition where the pressure difference between the pressure in the receiver 18 and the intermediate pressure in the refrigeration cycle is small. This is advantageous when the pressure at the receiver 18 is likely to be low, such as during operation.

  However, during the cooling operation, after cooling in the heat source side heat exchanger 4 and before flowing into the receiver 18 as the gas-liquid separator, there is a significant difference other than the first expansion mechanism 5a as the heat source side expansion mechanism. Under the condition that the pressure difference from the high pressure in the refrigeration cycle to the vicinity of the intermediate pressure in the refrigeration cycle can be used without depressurization operation, the refrigerant flowing between the heat source side heat exchanger 4 and the first expansion mechanism 5a is used. The second rear-stage injection pipe 19 that branches and returns to the rear-stage compression elements 103d and 104d, the refrigerant that flows between the heat source side heat exchanger 4 and the first expansion mechanism 5a, and the refrigerant that flows through the second rear-stage injection pipe 19 An economizer heat exchanger 20 that performs heat exchange with the second heat exchanger 20 after being heated by heat exchange in the economizer heat exchanger 20 9 is preferably returned to the rear-stage compression elements 103d and 104d (that is, intermediate pressure injection is performed by the economizer heat exchanger 20) (for example, the second rear-stage injection pipe 19 and the economizer heat in FIG. 18 described later). (See exchanger 20). This is because the intermediate pressure injection by the economizer heat exchanger 20 varies in the amount of heat exchanged in the economizer heat exchanger 20 because the flow rate of the refrigerant that can be returned to the subsequent compression elements 103d and 104d varies. In addition, when the pressure difference between the refrigerant pressure at the inlet of the economizer heat exchanger 20 and the intermediate pressure in the refrigeration cycle is small, the amount of heat exchange in the economizer heat exchanger 20 becomes small, and the downstream compression elements 103d and 104d Although the flow rate of the refrigerant that can be returned becomes small and its application is difficult, when the pressure difference between the refrigerant pressure at the inlet of the economizer heat exchanger 20 and the intermediate pressure in the refrigeration cycle is large, the economizer heat exchanger The amount of heat exchange at 20 becomes large, and the latter stage compression elements 103d and 104d Succoth flow rate of the refrigerant is increased, which can, its application is effective. In particular, when using a refrigerant that operates in a supercritical region, such as carbon dioxide, the high pressure in the refrigeration cycle exceeds the critical pressure, so the pressure difference between the high pressure and the intermediate pressure in the refrigeration cycle is even greater. Therefore, intermediate pressure injection by the economizer heat exchanger 20 is advantageous.

  In addition, as described above, for the purpose of performing cooling or heating according to the air conditioning load of a plurality of air-conditioned spaces, the configuration includes a plurality of usage-side heat exchangers 6 connected in parallel to each other, In order to control the flow rate of the refrigerant flowing through the use side heat exchanger 6 and obtain the refrigeration load required in each use side heat exchanger 6, the receiver 18 and the use side heat exchanger 6 When the configuration in which the use side expansion mechanism 5c is provided so as to correspond to each use side heat exchanger 6 is used during the cooling operation, the first expansion mechanism 5a reduces the pressure to near the saturation pressure and the receiver. The refrigerant temporarily stored in 18 (see point L in FIG. 18) is distributed to each use-side expansion mechanism 5c, but the refrigerant sent from the receiver 18 to each use-side expansion mechanism 5c is gas-liquid two-phase. When in use, each user side Because it may cause drift during distribution to Zhang mechanisms 5c, it is preferable that the refrigerant fed from the receiver 18 to the usage-side expansion mechanisms 5c as possible supercooled state.

  Therefore, in this modification, as shown in FIG. 18, by providing the first second-stage injection pipe 18c, the second second-stage injection pipe 19 and the economizer heat exchanger 20, as a gas-liquid separator during heating operation, The intermediate pressure injection by the receiver 18 is performed, and during the cooling operation, the intermediate pressure injection by the economizer heat exchanger 20 can be performed, and the supercooling heat exchanger is provided between the receiver 18 and the use side expansion mechanism 5c. 96 and a refrigerant circuit 210 provided with a second suction return pipe 95. Here, the first rear-stage injection pipe 18c and the second rear-stage injection pipe 19 are integrated with each other on the intermediate refrigerant pipe 8 side.

  In the present modification, the use side expansion mechanism 5c is an electric expansion valve. In the present modification, as described above, the second second-stage injection pipe 19 and the economizer heat exchanger 20 are used during the cooling operation, and the first second-stage injection pipe 18c is used during the heating operation. Therefore, it is not necessary to make the flow direction of the refrigerant to the economizer heat exchanger 20 constant regardless of the cooling operation and the heating operation, so the bridge circuit 17 is omitted and the configuration of the refrigerant circuit 210 is simplified.

  The second suction return pipe 95 branches the refrigerant sent from the heat source side heat exchanger 4 serving as a radiator to the use side heat exchanger 6 serving as an evaporator, and sucks the suction side of the compression mechanism 102 (that is, the suction mother). This is a refrigerant pipe returned to the pipe 102a). In the present modification, the second suction return pipe 95 is provided so as to branch the refrigerant sent from the receiver 18 to the use-side expansion mechanism 5c. More specifically, the second suction return pipe 95 branches the refrigerant from a position upstream of the supercooling heat exchanger 96 (that is, between the receiver 18 and the economizer heat exchanger 20) and sucks the suction mother pipe 102a. It is provided to return to. The second suction return pipe 95 is provided with a second suction return valve 95a capable of opening degree control. The second suction return valve 95a is an electric expansion valve in this modification.

  Further, the supercooling heat exchanger 96 includes a refrigerant sent from the heat source side heat exchanger 4 as a radiator to the use side heat exchanger 6 as an evaporator and a refrigerant flowing through the second suction return pipe 95 (more specifically, Is a heat exchanger that performs heat exchange with the refrigerant after being reduced to near low pressure in the second suction return valve 95a. In this modification, the supercooling heat exchanger 96 is a refrigerant that flows through a position upstream of the use-side expansion mechanism 5c (that is, between the position where the second suction return pipe 95 is branched and the use-side expansion mechanism 5c). And the refrigerant flowing through the second suction return pipe 95 are provided for heat exchange. In the present modification, the supercooling heat exchanger 96 is provided on the downstream side of the position where the second suction return pipe 95 is branched. For this reason, the refrigerant cooled in the heat source side heat exchanger 4 as a radiator passes through the economizer heat exchanger 20 and then branches to the second suction return pipe 95. In the supercooling heat exchanger 96, the second Heat exchange with the refrigerant flowing through the suction return pipe 95 is performed.

  Further, the outlet of the supercooling heat exchanger 96 on the second suction return pipe 95 side has a supercooling heat exchanger outlet temperature for detecting the temperature of the refrigerant at the outlet of the supercooling heat exchanger 96 on the second suction return pipe 95 side. A sensor 59 is provided.

  Next, operation | movement of the air conditioning apparatus 1 of this modification is demonstrated using FIGS. 18-24. Here, FIG. 19 is a diagram showing the flow of the refrigerant in the air conditioner 1 during the cooling operation, and FIG. 20 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the cooling operation in the present modification. FIG. 21 is a temperature-entropy diagram illustrating the refrigeration cycle during the cooling operation in the present modification, and FIG. 22 is a diagram illustrating the flow of the refrigerant in the air conditioner 1 during the heating operation. FIG. 23 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the heating operation in the present modification, and FIG. 24 is a temperature-entropy diagram illustrating the refrigeration cycle during the heating operation in the present modification. It is. Note that the following cooling operation, heating operation, and operation control in starting the compression mechanism are 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, H, I, and R in FIGS. 20 and 21 and pressure at points D and F in FIGS. 23 and 24). “Low pressure” means low pressure in the refrigeration cycle (that is, pressure at points A, F, S, and U in FIGS. 20 and 21 and pressure at points A and E in FIGS. 23 and 24). “Intermediate pressure” means the intermediate pressure in the refrigeration cycle (ie, the pressure at points B, C, G, J, and K in FIGS. 20 and 21 and the points B, C, G, I, L, and M in FIGS. Pressure).

<Cooling operation>
During the cooling operation, the switching mechanism 3 is in the cooling operation state indicated by the solid lines in FIGS. The opening degree of the first expansion mechanism 5a and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. Since the switching mechanism 3 is in the cooling operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is opened, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is closed. Thus, the intermediate heat exchanger 7 is brought into a state of functioning as a cooler. Further, when the switching mechanism 3 is in the cooling operation state, it is heated in the economizer heat exchanger 20 through the second second-stage injection pipe 19 without performing intermediate pressure injection by the receiver 18 as a gas-liquid separator. The intermediate pressure injection is performed by the economizer heat exchanger 20 for returning the refrigerant to the rear side compression elements 103d and 104d. More specifically, the first second-stage injection on / off valve 18d is closed, and the second second-stage injection valve 19a is adjusted in opening degree as in the cooling operation in the first modification. Further, when the switching mechanism 3 is in the cooling operation state, the degree of opening of the second suction return valve 95a is adjusted because the supercooling heat exchanger 96 is used. More specifically, in this modification, the second suction return valve 95a adjusts the opening so that the degree of superheat of the refrigerant at the outlet of the supercooling heat exchanger 96 on the second suction return pipe 95 side becomes the target value. In other words, so-called superheat control is performed. In this modification, the superheat degree of the refrigerant at the outlet on the second suction return pipe 95 side of the supercooling heat exchanger 96 is calculated by converting the low pressure detected by the suction pressure sensor 60 into the saturation temperature, and the supercooling heat exchange outlet temperature. This is obtained by subtracting the saturation temperature value of the refrigerant from the refrigerant temperature detected by the sensor 59. Although not adopted in this modification, a temperature sensor is provided at the inlet of the second cooling return pipe 95 side of the supercooling heat exchanger 96, and the refrigerant temperature detected by this temperature sensor is used as the supercooling heat exchange outlet. By subtracting from the refrigerant temperature detected by the temperature sensor 59, the degree of superheat of the refrigerant at the outlet of the supercooling heat exchanger 96 on the second suction return pipe 95 side may be obtained. Further, the adjustment of the opening degree of the second suction return valve 95a is not limited to the superheat degree control. For example, the opening degree of the second suction return valve 95a may be opened by a predetermined opening degree according to the refrigerant circulation amount in the refrigerant circuit 210. Good. Here, in order to explain the cooling operation in the state where both the first compression unit 103 and the second compression unit 104 are activated as an example, the rear-stage suction valve 85a is opened, and the subsequent compression unit activation valve 86a is closed. It is made to the state that was made. However, in the cooling operation in a state where only the first compression unit 103 is activated, the rear-stage suction valve 85a and the subsequent compression unit activation valve 86a are closed.

  In the state of the refrigerant circuit 210, a low-pressure refrigerant (see point A in FIGS. 18 to 21) is sucked into the compression mechanism 102 from the suction mother pipe 102a, and is first compressed to an intermediate pressure by the front-stage compression elements 103c and 104c. After that, the refrigerant is discharged to the inlet side intermediate branch pipes 81 and 84 of the intermediate refrigerant pipe 8 and merges in the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 through the check mechanisms 81a and 84a (point B in FIGS. 18 to 21). reference). The intermediate-pressure refrigerant discharged from the preceding-stage compression elements 103c and 104c and joined in the intermediate refrigerant pipe 8 is cooled in the intermediate heat exchanger 7 by exchanging heat with water or air as a cooling source ( (See point C in FIGS. 18-21). The refrigerant cooled in the intermediate heat exchanger 7 is further cooled by merging with the refrigerant (see point K in FIGS. 18 to 21) returned from the second second-stage injection pipe 19 to the second-stage compression elements 103d and 104d. (See point G in FIGS. 18 to 21). Next, the intermediate-pressure refrigerant that has joined with the refrigerant returning from the second rear-stage injection pipe 19 (that is, the intermediate-pressure injection by the economizer heat exchanger 20) is the outlet-side intermediate branch pipe 83 of the intermediate refrigerant pipe 8. , 85. The intermediate-pressure refrigerant branched from the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 to the outlet-side intermediate branch pipes 83 and 85 is supplied to the rear-stage compression elements 103d and 104d connected to the rear-stage side of the front-stage compression elements 103c and 104c. The air is sucked and further compressed, and is discharged from the compression parts 103 and 104 to the discharge branch pipes 103b and 104b (see point D in FIGS. 18 to 21). Here, the high-pressure refrigerant discharged from the compression units 103 and 104 is subjected to the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 20) by the two-stage compression operation by the compression elements 103c, 104c, 103d, and 104d. ) Compressed to a pressure exceeding The high-pressure refrigerant discharged from the first compression unit 103 flows into the first oil separator 141a constituting the first oil separation mechanism 141, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the first oil separator 141a flows into the first oil return pipe 141b constituting the first oil separation mechanism 141, and the first oil return pipe 141b is provided with the first oil return pipe 141b. After being depressurized by the first depressurization mechanism 141 c, it is returned to the second suction branch pipe 104 a of the second compression unit 104 and again sucked into the compression mechanism 102. Further, the high-pressure refrigerant discharged from the second compression unit 104 flows into the second oil separator 143a constituting the second oil separation mechanism 143, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the second oil separator 143a flows into the second oil return pipe 143b that constitutes the second oil separation mechanism 143, and is supplied to the second oil return pipe 143b. After the pressure is reduced by the second pressure reducing mechanism 143 c, the pressure is returned to the first suction branch pipe 103 a of the first compression unit 103 and is again sucked into the compression mechanism 102. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanisms 141 and 143 passes through the check mechanisms 142 and 144 and then merges in the discharge mother pipe 102b. It is sent to the heat source side heat exchanger 4 functioning as The high-pressure refrigerant sent to the heat source side heat exchanger 4 is cooled by exchanging heat with water or air as a cooling source in the heat source side heat exchanger 4 (point E in FIGS. 18 to 21). reference). A part of the high-pressure refrigerant cooled in the heat source side heat exchanger 4 is branched to the second second-stage injection pipe 19. And the refrigerant | coolant which flows through the 2nd back | latter stage side injection pipe 19 is sent to the economizer heat exchanger 20, after being pressure-reduced to intermediate pressure vicinity in the 2nd back | latter stage side injection valve 19a (refer the point J of FIGS. 18-21). . Moreover, the refrigerant | coolant after branching to the 2nd back | latter stage side injection pipe 19 flows into the economizer heat exchanger 20, and heat-exchanges with the refrigerant | coolant which flows through the 2nd back | latter stage side injection pipe | tube 19, and is cooled (FIG. 18 ~). (See point H in FIG. 21). On the other hand, the refrigerant flowing through the second second-stage injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator (see point K in FIGS. 18 to 21). ), As described above, the refrigerant is joined to the intermediate-pressure refrigerant discharged from the preceding-stage compression elements 103c and 104c. The high-pressure refrigerant cooled in the economizer heat exchanger 20 is decompressed to near the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 18 (see point I in FIGS. 18 to 21). A part of the refrigerant stored in the receiver 18 is branched to the second suction return pipe 95. And the refrigerant | coolant which flows through the 2nd suction return pipe 95 is pressure-reduced to the low pressure vicinity in the 2nd suction return valve 95a, Then, it sends to the supercooling heat exchanger 96 (refer point S of FIGS. 18-21). Further, the refrigerant branched into the second suction return pipe 95 flows into the supercooling heat exchanger 96, and is further cooled by exchanging heat with the refrigerant flowing through the second suction return pipe 95 (FIG. 18 to FIG. 18). (See point R in FIG. 21). On the other hand, the refrigerant flowing through the second suction return pipe 95 is heated by exchanging heat with the high-pressure refrigerant cooled in the economizer heat exchanger 20 (see the point U in FIGS. 18 to 21). The refrigerant flows through the suction side (here, the suction mother pipe 102a). The refrigerant cooled in the supercooling heat exchanger 96 is sent to the use-side expansion mechanism 5c and decompressed by the use-side expansion mechanism 5c to become a low-pressure gas-liquid two-phase refrigerant, and functions as a refrigerant evaporator. To the use side heat exchanger 6 (see point F in FIGS. 18 to 21). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use side heat exchanger 6 is heated by exchanging heat with water or air as a heating source to evaporate (FIG. 18 to FIG. 18). (See point A on 21). Then, the low-pressure refrigerant heated in the use side heat exchanger 6 is again sucked into the compression mechanism 102 via the switching mechanism 3. In this way, the cooling operation is performed.

  Thus, in the air conditioner 1 of the present modification, during the cooling operation, the refrigerant on the downstream side of the heat source side heat exchanger 4 as a radiator and the upstream side of the first expansion mechanism 5a as the heat source side expansion mechanism. The pressure of the economizer heat exchanger 20 is the same as in the above-described modified example 1, because the pressure is maintained at a high level and the pressure difference from the high pressure in the refrigeration cycle to the vicinity of the intermediate pressure in the refrigeration cycle can be used. Pressure injection is employed, so that the power consumption of the compression mechanism 102 can be reduced and the operation efficiency can be improved.

  Further, since the refrigerant (see point I in FIGS. 20 and 21) sent from the receiver 18 to the use-side expansion mechanism 5c can be cooled to the supercooled state by the supercooling heat exchanger 96 (see FIGS. 20 and 21). It is possible to reduce the risk of drift when distributing to each use side expansion mechanism 5c.

<Heating operation>
During the heating operation, the switching mechanism 3 is in the heating operation state indicated by the broken lines in FIGS. The opening degree of the first expansion mechanism 5a and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. Since the switching mechanism 3 is in a heating operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is closed, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is opened. As a result, the intermediate heat exchanger 7 is not allowed to function as a cooler. Further, when the switching mechanism 3 is in the heating operation state, the intermediate pressure injection by the economizer heat exchanger 20 is not performed, and the refrigerant is supplied from the receiver 18 as the gas-liquid separator through the first rear-stage injection pipe 18c. Intermediate pressure injection is performed by the receiver 18 that returns to the subsequent-stage compression elements 103d and 104d. More specifically, the first second-stage injection on / off valve 18d is opened, and the second second-stage injection valve 19a is fully closed. Further, when the switching mechanism 3 is in the heating operation state, since the supercooling heat exchanger 96 is not used, the second suction return valve 95a is also fully closed. Here, in order to explain the heating operation in the state where both the first compression unit 103 and the second compression unit 104 are activated as an example, the rear-stage intake valve 85a is opened and the late compression unit activation valve 86a is closed. It is made to the state that was made. However, in the heating operation in a state where only the first compression unit 103 is activated, the rear-stage suction valve 85a and the subsequent compression unit activation valve 86a are closed.

  In the state of the refrigerant circuit 210, low-pressure refrigerant (see point A in FIGS. 18 and 22 to 24) is sucked into the compression mechanism 102 from the suction mother pipe 102a, and is first intermediated by the front-stage compression elements 103c and 104c. After being compressed to a pressure, it is discharged to the inlet side intermediate branch pipes 81 and 84 of the intermediate refrigerant pipe 8 and merges in the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 through the check mechanisms 81a and 84a (FIGS. 18 and 22). -See point B in FIG. Unlike the cooling operation described above, the intermediate-pressure refrigerant discharged from the preceding-stage compression elements 103c and 104c and joined in the intermediate refrigerant pipe 8 does not pass through the intermediate heat exchanger 7 (that is, is cooled). Without passing through the intermediate heat exchanger bypass pipe 9 (see point C in FIGS. 18 and 22 to 24). The intermediate-pressure refrigerant that has passed through the intermediate heat exchanger bypass pipe 9 without being cooled by the intermediate heat exchanger 7 is returned to the rear-stage compression elements 103d and 104d from the receiver 18 through the first rear-stage injection pipe 18c. (Refer to the point M in FIGS. 18 and 22 to 24), and then cool (see the point G in FIGS. 18 and 22 to 24). Next, the intermediate-pressure refrigerant that has joined with the refrigerant returning from the first rear-stage injection pipe 18c (that is, the intermediate-pressure injection by the receiver 18 as a gas-liquid separator) is the middle of the intermediate refrigerant pipe 8 at the outlet side. Branches into branch pipes 83 and 85. The intermediate-pressure refrigerant branched from the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 to the outlet-side intermediate branch pipes 83 and 85 is supplied to the rear-stage compression elements 103d and 104d connected to the rear-stage side of the front-stage compression elements 103c and 104c. The air is sucked and further compressed, and is discharged from the compression units 103 and 104 to the discharge branch pipes 103b and 104b (see point D in FIGS. 18 and 22 to 24). Here, the high-pressure refrigerant discharged from the compression units 103 and 104 is subjected to the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 23) by the two-stage compression operation by the compression elements 103c, 104c, 103d, and 104d. ) Compressed to a pressure exceeding The high-pressure refrigerant discharged from the first compression unit 103 flows into the first oil separator 141a constituting the first oil separation mechanism 141, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the first oil separator 141a flows into the first oil return pipe 141b constituting the first oil separation mechanism 141, and the first oil return pipe 141b is provided with the first oil return pipe 141b. After being depressurized by the first depressurization mechanism 141 c, it is returned to the second suction branch pipe 104 a of the second compression unit 104 and again sucked into the compression mechanism 102. Further, the high-pressure refrigerant discharged from the second compression unit 104 flows into the second oil separator 143a constituting the second oil separation mechanism 143, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the second oil separator 143a flows into the second oil return pipe 143b that constitutes the second oil separation mechanism 143, and is supplied to the second oil return pipe 143b. After the pressure is reduced by the second pressure reducing mechanism 143 c, the pressure is returned to the first suction branch pipe 103 a of the first compression unit 103 and is again sucked into the compression mechanism 102. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanisms 141 and 143 merges in the discharge mother pipe 102b after passing through the check mechanisms 142 and 144, and passes through the switching mechanism 3 to be a refrigerant radiator. It is sent to the use side heat exchanger 6 that functions as a cooling source, and is cooled by exchanging heat with water or air as a cooling source (see point F in FIGS. 18 and 22 to 24). The high-pressure refrigerant cooled in the use-side heat exchanger 6 is sent to the use-side heat exchanger 6 that functions as a refrigerant radiator, and is cooled by exchanging heat with water or air as a cooling source. (See point F in FIGS. 18 and 22 to 24). The high-pressure refrigerant cooled in the use-side heat exchanger 6 is decompressed to the vicinity of the intermediate pressure by the use-side expansion mechanism 5c, and is then temporarily stored in the receiver 18 and gas-liquid separation is performed (see FIG. 18, see points I, L and M in FIGS. The gas refrigerant separated from the gas and liquid in the receiver 18 is extracted from the upper part of the receiver 18 by the first second-stage injection pipe 18c, and is discharged from the first-stage compression elements 103c and 104c as described above. Will join the refrigerant. Then, the liquid refrigerant stored in the receiver 18 is decompressed by the first expansion mechanism 5a to become a low-pressure gas-liquid two-phase refrigerant and sent to the heat source side heat exchanger 4 functioning as an evaporator of the refrigerant ( (Refer to point E in FIGS. 18 and 22-24). Then, the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated by heat exchange with water or air as a heating source to evaporate (FIG. 18, FIG. 22 to point 24 in FIG. 24). The low-pressure refrigerant heated in the heat source side heat exchanger 4 is again sucked into the compression mechanism 102 via the switching mechanism 3. In this way, the heating operation is performed.

  Thus, in the air conditioning apparatus 1 of the present modification, during the heating operation, the pressure in the receiver 18 as the gas-liquid separator may be lowered by the opening degree control of the use side expansion mechanism 5c during the heating operation. Since this is a possible condition, similar to the above-described embodiment, intermediate pressure injection by the receiver 18 as a gas-liquid separator is employed, so that the power consumption of the compression mechanism 102 can be reduced and the operation efficiency can be improved. it can.

<Starting the compression mechanism>
In the air conditioner 1 of this modification, the intermediate pressure injection by the economizer heat exchanger 20 is performed during the cooling operation, and the intermediate pressure injection by the receiver 18 is performed during the heating operation, which is either the cooling operation or the heating operation. Depending on how the rear stage injection pipe for returning to the intermediate refrigerant pipe 8 is properly used, the difference is from the above-described embodiment and the first modification, but during the cooling operation, as in the first modification, FIG. In steps S2 and S4, the opening degree of the second second-stage injection valve 19a of the second second-stage injection pipe 19 is operated, and during the heating operation, the first in steps S2 and S4 in FIG. By operating the opening of the first second-stage injection on / off valve 18d of the second-stage injection pipe 18c, Embodiments and modifications 1 and can perform the operation at the time of starting the same compression mechanism 102.

(5) Modification 3
In the refrigerant circuit 210 (see FIG. 18) in the above-described modified example 2, intermediate pressure injection by the receiver 18 as a gas-liquid separator and intermediate pressure injection by the economizer heat exchanger 20 are performed, whereby the rear-stage compression element 103d, In addition to lowering the temperature of the refrigerant discharged from 104d, reducing the power consumption of the compression mechanism 102 and improving the operation efficiency, or providing a second suction return pipe 95 and a supercooling heat exchanger 96, In order to cool the refrigerant sent to the use side expansion mechanism 5c by the cooling heat exchanger 96 to the supercooled state and reduce the heat radiation loss in the heat source side heat exchanger 4 during the cooling operation, the pre-stage side compression elements 103c, 104c The intermediate-stage refrigerant pipe 8 for sucking the refrigerant discharged from the second-stage compression elements 103d and 104d into the first-stage compression element In order to further provide an intermediate heat exchanger 7 that functions as a refrigerant cooler that is discharged from the compressors 103c and 104c and sucked into the downstream compression elements 103d and 104d, in order to suppress a decrease in heating capacity during heating operation, An intermediate heat exchanger bypass pipe 9 that bypasses the exchanger 7 is provided.

  For this reason, the intermediate heat exchanger 7 is a device that is not used during the heating operation.

  Therefore, in order to effectively use the intermediate heat exchanger 7 during the heating operation, in the present modification, as shown in FIG. 25, in the refrigerant circuit 210 of the above-described modification 2, one end of the intermediate heat exchanger 7 is used. And a third suction return pipe 92 for connecting the suction side of the compression mechanism 102 and the other end of the intermediate heat exchanger 7 between the use side heat exchanger 6 and the heat source side heat exchanger 4. The refrigerant circuit 310 is configured by providing an intermediate heat exchanger return pipe 94 for connection.

  Here, the third suction return pipe 92 is connected to one end of the intermediate heat exchanger 7 (here, the front end side compression element 103c, 104c side end), and the intermediate heat exchanger return pipe 94 is connected to the intermediate heat exchanger. It is connected to the other end of the container 7 (here, the downstream side compression elements 103d and 104d side ends). The third suction return pipe 92 performs intermediate heat exchange when the refrigerant discharged from the front-stage compression elements 103c and 104c through the intermediate heat exchanger bypass pipe 9 is sucked into the rear-stage compression elements 103d and 104d. This is a refrigerant pipe for connecting one end of the container 7 to the suction side (here, the suction mother pipe 102a) of the compression mechanism 102. The intermediate heat exchanger return pipe 94 allows the refrigerant discharged from the front-stage compression elements 103c and 104c through the intermediate heat exchanger bypass pipe 9 to be sucked into the rear-stage compression elements 103d and 104d, and the switching mechanism. 1 is used as a heat source side expansion mechanism for reducing the pressure of the refrigerant until the pressure becomes low in the refrigeration cycle. This is a refrigerant pipe for connecting the expansion mechanism 5a and the heat source side heat exchanger 4 as an evaporator) to the other end of the intermediate heat exchanger 7. In the present modification, one end of the third suction return pipe 92 is connected to the intermediate heat exchanger bypass pipe 9 at the end of the intermediate heat exchanger bypass pipe 9 from the front side compression elements 103c, 104c side end of the intermediate heat exchanger 7. The first stage compression elements 103c and 104c are connected to the end of the side, and the other end is connected to the suction side of the compression mechanism 102 (here, the suction mother pipe 102a). The intermediate heat exchanger return pipe 94 has one end connected to a portion from the first expansion mechanism 5 a to the heat source side heat exchanger 4, and the other end connected to the intermediate heat exchanger 7 of the intermediate refrigerant pipe 8. Are connected to the portion from the side end of the first-stage compression element 103c, 104c to the check mechanism 15. The third suction return pipe 92 is provided with a third suction return on / off valve 92a, and the intermediate heat exchanger return pipe 94 is provided with an intermediate heat exchanger return on / off valve 94a. The third suction return on / off valve 92a and the intermediate heat exchanger return on / off valve 94a are electromagnetic valves in this modification. In the present modification, the third suction return on-off valve 92a is basically closed when the switching mechanism 3 is in the cooling operation state and controlled to be opened when the switching mechanism 3 is in the heating operation state. The The intermediate heat exchanger return on-off valve 94a is basically controlled to be closed when the switching mechanism 3 is in the cooling operation state and to be opened when the switching mechanism 3 is in the heating operation state.

  As described above, in this modification, the intermediate-pressure refrigerant flowing through the intermediate refrigerant pipe 8 is mainly supplied by the intermediate heat exchanger bypass pipe 9, the third suction return pipe 92, and the intermediate heat exchanger return pipe 94 during the cooling operation. The refrigerant can be cooled by the intermediate heat exchanger 7, and during the heating operation, the intermediate pressure refrigerant flowing through the intermediate refrigerant pipe 8 is bypassed by the intermediate heat exchanger bypass pipe 9, and the third suction return is performed. By the pipe 92 and the intermediate heat exchanger return pipe 94, a part of the refrigerant cooled in the use side heat exchanger 6 can be led to the intermediate heat exchanger 7 to be evaporated and returned to the suction side of the compression mechanism 102. It has become.

  Next, operation | movement of the air conditioning apparatus 1 of this modification is demonstrated using FIG.25, FIG.26, FIG.20, FIG.21 and FIG. Here, FIG. 26 is a diagram illustrating a refrigerant flow in the air conditioner 1 during the cooling operation, and FIG. 27 is a diagram illustrating a refrigerant flow in the air conditioner 1 during the heating operation. 28 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the heating operation in the present modification, and FIG. 29 is a temperature-entropy diagram illustrating the refrigeration cycle during the heating operation in the present modification. . Note that the following cooling operation, heating operation, and operation control in starting the compression mechanism are 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, H, I, and R in FIGS. 20 and 21 and pressure at points D and F in FIGS. 28 and 29). “Low pressure” means low pressure in the refrigeration cycle (ie, pressure at points A, F, S, U in FIGS. 20 and 21 and pressure at points A, E, and V in FIGS. 28 and 29). , “Intermediate pressure” means the intermediate pressure in the refrigeration cycle (that is, the pressure at points B, C, G, J, K in FIGS. 20 and 21 and the points B, C, G, I, L, Pressure at M).

<Cooling operation>
During the cooling operation, the switching mechanism 3 is in the cooling operation state indicated by the solid lines in FIGS. The opening degree of the first expansion mechanism 5a and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. Since the switching mechanism 3 is in the cooling operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is opened, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is closed. As a result, the intermediate heat exchanger 7 is brought into a state of functioning as a cooler, and the third suction return on / off valve 92a of the third suction return pipe 92 is closed, whereby the intermediate heat exchanger 7 and the compression mechanism 102 are closed. When the suction side is not connected, and the intermediate heat exchanger return on / off valve 94a of the intermediate heat exchanger return pipe 94 is closed, the use side heat exchanger 6 and the heat source side heat exchanger 4 And the intermediate heat exchanger 7 are not connected. Further, when the switching mechanism 3 is in the cooling operation state, it is heated in the economizer heat exchanger 20 through the second second-stage injection pipe 19 without performing intermediate pressure injection by the receiver 18 as a gas-liquid separator. The intermediate pressure injection is performed by the economizer heat exchanger 20 for returning the refrigerant to the rear side compression elements 103d and 104d. More specifically, the first second-stage injection on / off valve 18d is closed, and the second second-stage injection valve 19a is adjusted in opening degree as in the cooling operation in the first and second modifications. . Further, when the switching mechanism 3 is in the cooling operation state, the degree of opening of the second suction return valve 95a is adjusted because the supercooling heat exchanger 96 is used. More specifically, the opening degree of the second suction return valve 95a is adjusted in the same manner as in the cooling operation in Modification 2 described above. Here, in order to explain the cooling operation in the state where both the first compression unit 103 and the second compression unit 104 are activated as an example, the rear-stage suction valve 85a is opened, and the subsequent compression unit activation valve 86a is closed. It is made to the state that was made. However, in the cooling operation in a state where only the first compression unit 103 is activated, the rear-stage suction valve 85a and the subsequent compression unit activation valve 86a are closed.

  In the state of the refrigerant circuit 310, low-pressure refrigerant (see point A in FIGS. 25, 26, 20, and 21) is sucked into the compression mechanism 102 from the suction mother pipe 102a, and first, the front-stage compression element 103c, After being compressed to the intermediate pressure by 104c, it is discharged to the inlet side intermediate branch pipes 81 and 84 of the intermediate refrigerant pipe 8, and merges in the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 through the check mechanisms 81a and 84a (FIG. 25). FIG. 26, FIG. 20 and FIG. 21 (see point B). The intermediate pressure refrigerant discharged from the preceding-stage compression elements 103c and 104c and joined in the intermediate refrigerant pipe 8 is cooled by heat exchange with water or air as a cooling source in the intermediate heat exchanger 7 ( (Refer to point C in FIGS. 25, 26, 20, and 21). The refrigerant cooled in the intermediate heat exchanger 7 is returned from the second second-stage injection pipe 19 to the second-stage compression elements 103d and 104d (see point K in FIGS. 25, 26, 20 and 21). It is further cooled by joining (see point G in FIGS. 25, 26, 20, and 21). Next, the intermediate-pressure refrigerant that has joined with the refrigerant returning from the second rear-stage injection pipe 19 (that is, the intermediate-pressure injection by the economizer heat exchanger 20) is the outlet-side intermediate branch pipe 83 of the intermediate refrigerant pipe 8. , 85. The intermediate-pressure refrigerant branched from the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 to the outlet-side intermediate branch pipes 83 and 85 is supplied to the rear-stage compression elements 103d and 104d connected to the rear-stage side of the front-stage compression elements 103c and 104c. Inhaled, further compressed, and discharged from the compression sections 103 and 104 to the discharge branch pipes 103b and 104b (see point D in FIGS. 25, 26, 20 and 21). Here, the high-pressure refrigerant discharged from the compression units 103 and 104 is subjected to the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 20) by the two-stage compression operation by the compression elements 103c, 104c, 103d, and 104d. ) Compressed to a pressure exceeding The high-pressure refrigerant discharged from the first compression unit 103 flows into the first oil separator 141a constituting the first oil separation mechanism 141, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the first oil separator 141a flows into the first oil return pipe 141b constituting the first oil separation mechanism 141, and the first oil return pipe 141b is provided with the first oil return pipe 141b. After being depressurized by the first depressurization mechanism 141 c, it is returned to the second suction branch pipe 104 a of the second compression unit 104 and again sucked into the compression mechanism 102. Further, the high-pressure refrigerant discharged from the second compression unit 104 flows into the second oil separator 143a constituting the second oil separation mechanism 143, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the second oil separator 143a flows into the second oil return pipe 143b that constitutes the second oil separation mechanism 143, and is supplied to the second oil return pipe 143b. After the pressure is reduced by the second pressure reducing mechanism 143 c, the pressure is returned to the first suction branch pipe 103 a of the first compression unit 103 and is again sucked into the compression mechanism 102. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanisms 141 and 143 passes through the check mechanisms 142 and 144 and then merges in the discharge mother pipe 102b. It is sent to the heat source side heat exchanger 4 functioning as The high-pressure refrigerant sent to the heat source side heat exchanger 4 is cooled by exchanging heat with water or air as a cooling source in the heat source side heat exchanger 4 (FIGS. 25, 26, and 20). , See point E in FIG. 21). A part of the high-pressure refrigerant cooled in the heat source side heat exchanger 4 is branched to the second second-stage injection pipe 19. And the refrigerant | coolant which flows through the 2nd back | latter stage side injection pipe 19 is sent to the economizer heat exchanger 20, after being depressurized to the intermediate pressure vicinity in the 2nd back | latter stage side injection valve 19a (FIG. 25, FIG. (See point J on 21). Further, the refrigerant branched to the second second-stage injection pipe 19 flows into the economizer heat exchanger 20, and is cooled by exchanging heat with the refrigerant flowing through the second second-stage injection pipe 19 (FIG. 25). (See point H in FIGS. 26, 20 and 21). On the other hand, the refrigerant flowing through the second rear-stage side injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator (FIGS. 25, 26, 20). As described above, the intermediate pressure refrigerant discharged from the pre-stage compression elements 103c and 104c is merged. The high-pressure refrigerant cooled in the economizer heat exchanger 20 is decompressed to near the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 18 (FIGS. 25, 26, 20, and 21). Point I). A part of the refrigerant stored in the receiver 18 is branched to the second suction return pipe 95. Then, the refrigerant flowing through the second suction return pipe 95 is reduced to near low pressure in the second suction return valve 95a, and then sent to the supercooling heat exchanger 96 (see FIGS. 25, 26, 20, and 21). (See point S). In addition, the refrigerant after being branched to the second suction return pipe 95 flows into the supercooling heat exchanger 96, and is further cooled by exchanging heat with the refrigerant flowing through the second suction return pipe 95 (FIG. 25). (See point R in FIGS. 26, 20 and 21). On the other hand, the refrigerant flowing through the second suction return pipe 95 is heated by exchanging heat with the high-pressure refrigerant cooled in the economizer heat exchanger 20 (see point U in FIGS. 25, 26, 20 and 21). ) And the refrigerant flowing through the suction side (here, the suction mother pipe 102a) of the compression mechanism 102. The refrigerant cooled in the supercooling heat exchanger 96 is sent to the use-side expansion mechanism 5c and decompressed by the use-side expansion mechanism 5c to become a low-pressure gas-liquid two-phase refrigerant, and functions as a refrigerant evaporator. To the use side heat exchanger 6 (see point F in FIGS. 25, 26, 20, and 21). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use-side heat exchanger 6 is heated by exchanging heat with water or air as a heating source to evaporate (FIG. 25, FIG. 25). 26, see point A in FIGS. Then, the low-pressure refrigerant heated in the use side heat exchanger 6 is again sucked into the compression mechanism 102 via the switching mechanism 3. In this way, the cooling operation is performed.

  Thus, in the air conditioning apparatus 1 of the present modification, the same effects as those of Modification 2 described above can be obtained during the cooling operation.

<Heating operation>
During the heating operation, the switching mechanism 3 is in the heating operation state indicated by the broken lines in FIGS. The opening degree of the first expansion mechanism 5a and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. Since the switching mechanism 3 is in a heating operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is closed, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is opened. As a result, the intermediate heat exchanger 7 is disabled from functioning as a cooler, and the third suction return on / off valve 92a of the third suction return pipe 92 is opened, whereby the intermediate heat exchanger 7 and the compression mechanism 102 are The use side heat exchanger 6, the heat source side heat exchanger 4, and the heat source side heat exchanger 4 are opened by opening the intermediate heat exchanger return on / off valve 94 a of the intermediate heat exchanger return pipe 94. And the intermediate heat exchanger 7 are connected to each other. Further, when the switching mechanism 3 is in the heating operation state, the intermediate pressure injection by the economizer heat exchanger 20 is not performed, and the refrigerant is supplied from the receiver 18 as the gas-liquid separator through the first rear-stage injection pipe 18c. Intermediate pressure injection is performed by the receiver 18 that returns to the subsequent-stage compression elements 103d and 104d. More specifically, the first second-stage injection on / off valve 18d is opened, and the second second-stage injection valve 19a is fully closed. Further, when the switching mechanism 3 is in the heating operation state, since the supercooling heat exchanger 96 is not used, the second suction return valve 95a is also fully closed. Here, in order to explain the heating operation in the state where both the first compression unit 103 and the second compression unit 104 are activated as an example, the rear-stage intake valve 85a is opened and the late compression unit activation valve 86a is closed. It is made to the state that was made. However, in the heating operation in a state where only the first compression unit 103 is activated, the rear-stage suction valve 85a and the subsequent compression unit activation valve 86a are closed.

  In the state of the refrigerant circuit 310, the low-pressure refrigerant (see point A in FIGS. 25 and 27 to 29) is sucked into the compression mechanism 102 from the suction mother pipe 102a, and is first intermediated by the front-stage compression elements 103c and 104c. After being compressed to the pressure, the refrigerant is discharged to the inlet side intermediate branch pipes 81 and 84 of the intermediate refrigerant pipe 8 and merged in the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 through the check mechanisms 81a and 84a (FIGS. 25 and 27). -See point B in FIG. 29). Unlike the cooling operation described above, the intermediate-pressure refrigerant discharged from the preceding-stage compression elements 103c and 104c and joined in the intermediate refrigerant pipe 8 does not pass through the intermediate heat exchanger 7 (that is, is cooled). Without passing through the intermediate heat exchanger bypass pipe 9 (see point C in FIGS. 25 and 27 to 29). The intermediate-pressure refrigerant that has passed through the intermediate heat exchanger bypass pipe 9 without being cooled by the intermediate heat exchanger 7 is returned to the rear-stage compression elements 103d and 104d from the receiver 18 through the first rear-stage injection pipe 18c. (Refer to the point M in FIGS. 25 and 27 to 29) and cool (see the point G in FIGS. 25 and 27 to 29). Next, the intermediate-pressure refrigerant that has joined with the refrigerant returning from the first rear-stage injection pipe 18c (that is, the intermediate-pressure injection by the receiver 18 as a gas-liquid separator) is the middle of the intermediate refrigerant pipe 8 at the outlet side. Branches into branch pipes 83 and 85. The intermediate-pressure refrigerant branched from the intermediate mother pipe 82 of the intermediate refrigerant pipe 8 to the outlet-side intermediate branch pipes 83 and 85 is supplied to the rear-stage compression elements 103d and 104d connected to the rear-stage side of the front-stage compression elements 103c and 104c. Inhaled, further compressed, and discharged from the compression sections 103 and 104 to the discharge branch pipes 103b and 104b (see point D in FIGS. 25 and 27 to 29). Here, the high-pressure refrigerant discharged from the compression units 103 and 104 is subjected to the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 28) by the two-stage compression operation by the compression elements 103c, 104c, 103d, and 104d. ) Compressed to a pressure exceeding The high-pressure refrigerant discharged from the first compression unit 103 flows into the first oil separator 141a constituting the first oil separation mechanism 141, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the first oil separator 141a flows into the first oil return pipe 141b constituting the first oil separation mechanism 141, and the first oil return pipe 141b is provided with the first oil return pipe 141b. After being depressurized by the first depressurization mechanism 141 c, it is returned to the second suction branch pipe 104 a of the second compression unit 104 and again sucked into the compression mechanism 102. Further, the high-pressure refrigerant discharged from the second compression unit 104 flows into the second oil separator 143a constituting the second oil separation mechanism 143, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the second oil separator 143a flows into the second oil return pipe 143b that constitutes the second oil separation mechanism 143, and is supplied to the second oil return pipe 143b. After the pressure is reduced by the second pressure reducing mechanism 143 c, the pressure is returned to the first suction branch pipe 103 a of the first compression unit 103 and is again sucked into the compression mechanism 102. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanisms 141 and 143 merges in the discharge mother pipe 102b after passing through the check mechanisms 142 and 144, and passes through the switching mechanism 3 to be a refrigerant radiator. Is sent to the use-side heat exchanger 6 that functions as a cooling source, and is cooled by exchanging heat with water or air as a cooling source (see point F in FIGS. 25 and 27 to 29). The high-pressure refrigerant cooled in the use-side heat exchanger 6 is sent to the use-side heat exchanger 6 that functions as a refrigerant radiator, and is cooled by exchanging heat with water or air as a cooling source. (See point F in FIGS. 25 and 27-29). Then, the high-pressure refrigerant cooled in the use side heat exchanger 6 is depressurized to the vicinity of the intermediate pressure by the use side expansion mechanism 5c, and is then temporarily stored in the receiver 18 and gas-liquid separation is performed (FIG. 25, see points I, L, and M in FIGS. The gas refrigerant separated from the gas and liquid in the receiver 18 is extracted from the upper part of the receiver 18 by the first second-stage injection pipe 18c, and is discharged from the first-stage compression elements 103c and 104c as described above. Will join the refrigerant. The liquid refrigerant stored in the receiver 18 is reduced in pressure by the first expansion mechanism 5a to become a low-pressure gas-liquid two-phase refrigerant, and is sent to the heat source side heat exchanger 4 functioning as an evaporator of the refrigerant. Then, the refrigerant is also sent to the intermediate heat exchanger 7 functioning as a refrigerant evaporator through the intermediate heat exchanger return pipe 94 (see point E in FIGS. 25 and 27 to 29). Then, the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated by heat exchange with water or air as a heating source and evaporated (FIG. 25, FIG. 25). 27 to point 29 in FIG. 29). Further, the low-pressure gas-liquid two-phase refrigerant sent to the intermediate heat exchanger 7 is also heated by exchanging heat with water or air as a heating source (FIGS. 25 and 27). -See point V in FIG. 29). The low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 is again sucked into the compression mechanism 102 via the switching mechanism 3. Further, the low-pressure refrigerant heated and evaporated in the intermediate heat exchanger 7 is again sucked into the compression mechanism 102 through the third suction return pipe 92. In this way, the heating operation is performed.

  As described above, in the air conditioner 1 of the present modification, during the heating operation, the same operational effects as those of the above-described modification 2 are obtained, and the intermediate heat exchanger 7 is radiated in the use-side heat exchanger 7. It is made to function as a refrigerant evaporator so that it can be effectively used during heating operation, thereby increasing the refrigerant evaporation capability during heating operation and suppressing the heating capability of the use side heat exchanger 6 from being lowered. It is possible to prevent the operating efficiency during heating operation from being lowered.

<Starting the compression mechanism>
The air conditioner 1 of the present modification differs from the second modification described above in that the intermediate heat exchanger 7 is used as a refrigerant evaporator during heating operation, but is basically the same as the second modification described above. The operation at the time of starting the compression mechanism 102 can be performed.

(6) Other Embodiments While 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, and Changes can be made without departing from the scope of the invention.

  For example, in the above-described embodiment and its modification, each of the two compression elements is integrally incorporated as a compression mechanism in which a plurality of compression units having a front-stage compression element and a rear-stage compression element are connected in parallel. Although the compression mechanism 102 in which the two-stage compression compressors 103 and 104 are connected in parallel is employed, the present invention is not limited to this, and there are a plurality of compressors in which three or more compression elements are integrated. A plurality of compressors connected in parallel to each other and a compressor incorporating a single compression element and / or a compressor incorporating two or more compression elements connected in series. A connected compression mechanism may be employed.

  Moreover, in the above-mentioned embodiment and its modification, while using the refrigerant | coolant which flows through the utilization side heat exchanger 6, the water or brine as a heating source or a cooling source which performs heat exchange, and heat exchange in the utilization 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, the refrigerant operating in the supercritical region is not limited to carbon dioxide, and ethylene, ethane, nitrogen oxide, or the like may be used.

  By using the present invention, a refrigerant operating in the supercritical region having a refrigerant circuit in which a plurality of compressors having a front-stage compression element and a rear-stage compression element are connected in parallel and capable of intermediate pressure injection is used. In a refrigeration system that performs a multistage compression refrigeration cycle using a compressor, when the other compression unit is activated in a state where the compression unit already activated exists, the latter stage side compression of the compression unit already activated It is possible to suppress the refrigerant sucked into the element from becoming wet.

It is a schematic block diagram of the air conditioning apparatus as one Embodiment of the freezing apparatus concerning this invention. It is a figure which shows the flow of the refrigerant | coolant in the air conditioning apparatus at the time of air_conditionaing | cooling operation. 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 a figure which shows the flow of the refrigerant | coolant in the air conditioning apparatus at the time of heating 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 late compression part starting control. It is a figure which shows the flow of the refrigerant | coolant in an air conditioning apparatus before the start of late compression part starting control (namely, the state where only the 1st compression part is started). The state in which the second compression unit is activated (that is, after the second compression unit is activated, the opening operation of the rear side suction valve, the closing operation of the subsequent compression unit activation valve, and the opening of the first rear side injection opening / closing valve) It is a figure which shows the flow of the refrigerant | coolant in the air conditioning apparatus in the state before performing operation. It is a schematic block diagram of the air conditioning apparatus concerning the modification 1. It is a figure which shows the flow of the refrigerant | coolant in the air conditioning apparatus at the time of air_conditionaing | cooling operation. 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 a figure which shows the flow of the refrigerant | coolant in the air conditioning apparatus at the time of heating 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 schematic block diagram of the air conditioning apparatus concerning the modification 2. It is a figure which shows the flow of the refrigerant | coolant in the air conditioning apparatus at the time of air_conditionaing | cooling operation. 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 a figure which shows the flow of the refrigerant | coolant in the air conditioning apparatus at the time of heating 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 schematic block diagram of the air conditioning apparatus concerning the modification 3. It is a figure which shows the flow of the refrigerant | coolant in the air conditioning apparatus at the time of air_conditionaing | cooling operation. It is a figure which shows the flow of the refrigerant | coolant in the air conditioning apparatus at the time of heating 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.

Explanation of symbols

1 Air conditioning equipment (refrigeration equipment)
4 Heat source side heat exchanger (heat radiator, evaporator)
6 Use side heat exchanger (evaporator, radiator)
7 Intermediate Heat Exchanger 8 Intermediate Refrigerant Pipe 18c First Second Stage Injection Pipe 18d First Second Stage Injection Open / Close Valve 19 Second Second Stage Injection Pipe 19a Second Second Stage Injection Valve 20 Economizer Heat Exchanger (Cooler)
81 First inlet side intermediate branch pipe 82 Intermediate mother pipe 83 First outlet side intermediate branch pipe 84 Second inlet side intermediate branch pipe 85 Second outlet side intermediate branch pipe 85a Rear stage suction valve 86 Start bypass pipe 86a Subsequent compression section start Valve 102 Compression mechanism 103 First compression unit 104 Second compression unit

Claims (6)

A refrigeration system using a refrigerant operating in a supercritical region,
A first front-stage compression element that sucks low-pressure refrigerant in the refrigeration cycle and compresses it to an intermediate pressure in the refrigeration cycle; and a first rear-stage compression element that sucks intermediate-pressure refrigerant in the refrigeration cycle and compresses it to a high pressure in the refrigeration cycle; A first compression section (103) having a variable operating capacity, a second pre-stage compression element that sucks low-pressure refrigerant in the refrigeration cycle and compresses it to an intermediate pressure in the refrigeration cycle, and an intermediate pressure in the refrigeration cycle A compression mechanism (102) including a second compression section (104) having a second rear-stage compression element that sucks the refrigerant and compresses the refrigerant to a high pressure in the refrigeration cycle;
An intermediate refrigerant pipe (8) for sucking the refrigerant discharged from the front-stage compression element into the rear-stage compression element;
A radiator (4, 6) for radiating the refrigerant compressed by the compression mechanism;
An evaporator (6, 4) for evaporating the refrigerant radiated by the radiator;
A rear-stage injection valve, and a rear-stage injection pipe (18c, 19) for branching the refrigerant radiated in the radiator and returning it to the intermediate refrigerant pipe;
In the subsequent compression unit activation control for activating the second compression unit from the state in which the first compression unit is activated, when lowering the operating capacity of the first compression unit prior to activation of the second compression unit, Reduce the opening of the rear injection valve,
Refrigeration equipment (1). The intermediate refrigerant pipe (8) is connected to a discharge side of the first front-stage compression element and a first inlet-side intermediate branch pipe (81) connected to the discharge side of the first front-stage compression element. 2 inlet side intermediate branch pipes (84), an intermediate mother pipe (82) where the inlet side intermediate branch pipes merge, and a branch from the intermediate mother pipe to be connected to the suction side of the first second-stage compression element A second outlet side having a first outlet-side intermediate branch pipe (83) and a rear-stage side suction valve (85a) branched from the intermediate mother pipe and connected to the suction side of the second rear-stage-side compression element An intermediate branch pipe (85),
The latter-stage injection pipe (18c, 19) is connected to the intermediate mother pipe,
A start-up bypass pipe (86) having a late compression section start valve and communicating the second inlet side intermediate branch pipe and the second outlet side intermediate branch pipe;
In the subsequent compression unit activation control, the second-stage compression unit is activated with the latter-stage suction valve closed and the subsequent-compression unit activation valve opened, and after the second compression unit is activated, Open the rear-stage suction valve and close the later-compression compressor start valve,
The refrigeration apparatus (1) according to claim 1.   In the subsequent compression unit activation control, when the latter stage suction valve (85a) is opened and the latter compression unit activation valve (86a) is closed, the opening degree of the latter stage injection valve (18c, 19). The refrigeration apparatus (1) according to claim 2, wherein   The intermediate mother pipe (82) is provided with an intermediate heat exchanger (7) that functions as a refrigerant cooler that is discharged from the front-stage compression element and sucked into the rear-stage compression element. The refrigeration apparatus (1) according to 2 or 3.   The economizer heat exchanger (20) that further performs heat exchange between the refrigerant that has radiated heat in the radiator (4, 6) and the refrigerant that flows through the rear-stage injection pipe (19). The refrigeration apparatus (1) described in 1. The refrigerating apparatus (1) according to any one of claims 1 to 5, wherein the refrigerant operating in the supercritical region is carbon dioxide.

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