JP6024341B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to an air conditioner, and more particularly to a refrigeration apparatus including a refrigerant circuit configured by connecting a compressor, a radiator, an expander, and an evaporator.

  Conventionally, there is a refrigeration apparatus including a refrigerant circuit configured by connecting a compressor, a radiator, an expander, and an evaporator as shown in Patent Document 1 (Japanese Patent Laid-Open No. 2011-214778). . Here, the expander is an expansion element that expands the refrigerant that has flowed in to generate power, and a regenerative drive that is driven as a generator by the power generated by the expansion element after being driven as a motor at the start of operation. And a generator to be driven.

  In the above-described refrigeration apparatus, it takes time until the discharge pressure of the compressor rises at the start of operation, that is, until the pressure difference in the refrigerant circuit is applied. For this reason, it takes time until a differential pressure is applied between the upstream side and the downstream side of the expander. If the differential pressure between the upstream side and the downstream side of the expander is small, the expander cannot be shifted from the power running drive to the regenerative drive, and therefore the power running drive of the expander is continued. In particular, under conditions where the outside air temperature is low (for example, the outside air temperature is about −20 ° C.), the discharge pressure of the compressor is unlikely to increase, so that the power running drive of the expander continues for a long time. If such a long-time power running drive of the expander is repeated many times each time the operation is started, the power consumption of the refrigeration apparatus, that is, the running cost increases, and the performance of the refrigeration apparatus decreases.

  An object of the present invention is to provide a refrigeration apparatus having a refrigerant circuit configured by connecting a compressor, a radiator, an expander, and an evaporator, and shortening the time required for powering the expander to reduce power consumption. Is to suppress the decrease in the performance of the refrigeration apparatus.

  A refrigeration apparatus according to a first aspect is a refrigeration apparatus including a refrigerant circuit configured by connecting a compressor, a radiator, an expander, and an evaporator. Here, the expander is an expansion element that expands the refrigerant that has flowed in to generate power, and a regenerative drive that is driven as a generator by the power generated by the expansion element after being driven as a motor at the start of operation. And a generator to be driven. In this refrigeration apparatus, the refrigerant circuit further includes a suction return pipe that bypasses the refrigerant from the downstream side of the expander to the suction side of the compressor, and the suction return pipe provided in the suction return pipe at the start of operation. The expander is activated by opening the valve.

  Here, since the refrigerant is bypassed from the downstream side of the expander to the suction side of the compressor through the suction return pipe during the power running drive of the expander at the start of operation, the pressure of the refrigerant on the downstream side of the expander decreases. For this reason, at the start of operation, the differential pressure between the upstream side and the downstream side of the expander can be increased, and the expander quickly shifts from power running drive to regenerative drive.

  Thereby, here, it becomes possible to shorten the power running time of the expander, and it is possible to suppress the increase in power consumption and the decrease in the performance of the refrigeration apparatus.

Further, here, the refrigerant circuit further includes a receiver that temporarily stores the refrigerant on the downstream side of the expander, and a receiver outlet pipe that draws out the liquid refrigerant from the lower part of the receiver, and the suction return pipe, It is connected to the receiver so as to derive the gas refrigerant from the upper part of the receiver.

  Here, since the suction return pipe is provided so as to lead out the refrigerant from the upper part of the receiver, at the time of powering driving of the expander at the start of operation, the refrigerant in the gas state is returned to the suction side of the compressor as much as possible. The pressure of the refrigerant on the downstream side of the expander can be reduced to near the low pressure of the refrigeration cycle.

  As a result, during the power running drive of the expander at the start of operation, the differential pressure between the upstream side and the downstream side of the expander is reduced while suppressing a large amount of liquid refrigerant from returning to the suction side of the compressor. Can be bigger.

Here, the refrigerant circuit further includes a heat recovery heat exchanger that performs heat exchange between the refrigerant flowing through the receiver outlet pipe and the refrigerant flowing through the suction return pipe.

  Here, the refrigerant flowing through the suction return pipe can be reduced to the low pressure of the refrigeration cycle and returned to the suction side of the compressor after heat exchange in the heat recovery heat exchanger.

  Thereby, here, during the power running of the expander at the start of operation, the liquid refrigerant is prevented from returning to the suction side of the compressor, and the differential pressure between the upstream side and the downstream side of the expander is increased. be able to.

Also, here, when the expander is driven by power, the opening of the suction return valve is set to 40 to 60% (the fully open state is set to 100%), and the expander shifts from power running to regenerative drive. The opening degree of the suction return valve is controlled so that the refrigerant at the outlet on the suction return pipe side of the heat recovery heat exchanger is overheated. Then, after confirming that the refrigerant at the outlet on the suction return pipe side of the heat recovery heat exchanger is overheated, between the refrigerant pressure on the downstream side of the expander and the refrigerant pressure on the suction side of the compressor The opening degree of the suction return valve is controlled based on the differential pressure.

  Here, since the opening of the suction return valve is set to 40 to 60% during powering driving of the expander at the start of operation, the circulation of the refrigerant to the evaporator side is maintained and the suction return pipe is passed through. The flow rate of the gas refrigerant bypassed from the downstream side of the expander to the suction side of the compressor can be ensured. In addition, during the regenerative drive of the expander after shifting the expander from power running drive to regenerative drive (during normal operation), the refrigerant at the outlet on the suction return pipe side of the heat recovery heat exchanger is overheated. Since the opening degree of the suction return valve is controlled, it is possible to reliably suppress the liquid refrigerant from returning to the suction side of the compressor through the suction return pipe.

  Thereby, at the time of powering driving of the expander at the start of operation, the pressure difference between the upstream side and the downstream side of the expander can be increased while circulating the refrigerant in the entire refrigerant circuit, In addition, during normal operation, the liquid refrigerant can be reliably prevented from returning to the suction side of the compressor through the suction return pipe.

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

In the refrigeration apparatus according to the first aspect, it is possible to shorten the time for powering driving of the expander, and it is possible to suppress an increase in power consumption and a decrease in performance of the refrigeration apparatus. In addition, during the power running drive of the expander at the start of operation, it is possible to increase the differential pressure between the upstream side and the downstream side of the expander while suppressing a large amount of liquid refrigerant from returning to the suction side of the compressor. it can. Further, at the time of powering driving of the expander at the start of operation, it is possible to increase the differential pressure between the upstream side and the downstream side of the expander while suppressing the liquid refrigerant from returning to the suction side of the compressor. In addition, during the power running drive of the expander at the start of operation, the differential pressure between the upstream side and the downstream side of the expander can be increased while circulating the refrigerant in the entire refrigerant circuit, and the normal operation In some cases, it is possible to reliably prevent the liquid refrigerant from returning to the suction side of the compressor through the suction return pipe.

It is a schematic block diagram of the air conditioning apparatus as one Embodiment of the freezing apparatus concerning this invention. It is a block diagram which shows the power supply circuit structure of a compressor and an expander. It is a block diagram which shows the control structure of an air conditioning apparatus. It is the pressure-enthalpy diagram in which the refrigerating cycle at the time of the power running drive of the expander at the time of the start of operation when not performing start control is illustrated. It is a flowchart of starting control at the time of the start of the operation | movement which uses an expander. It is the pressure-enthalpy diagram in which the refrigerating cycle at the time of the power running drive of the expander at the time of the start of operation in the case of performing start control is shown It is a schematic block diagram of the air conditioning apparatus as a modification of the freezing apparatus concerning this invention.

  Hereinafter, an embodiment of an air-conditioning apparatus as an embodiment of a refrigeration apparatus according to the present invention and a modification thereof will be described based on the drawings. In addition, the specific structure of the freezing apparatus concerning this invention is not restricted to the following embodiment and its modification, It can change in the range which does not deviate from the summary of invention.

(1) Configuration of air conditioner <Overall>
FIG. 1 is a schematic configuration diagram of an air-conditioning apparatus 1 as an embodiment of a refrigeration apparatus according to the present invention. The air conditioner 1 is a device capable of cooling and heating a room such as a building by performing a vapor compression refrigeration cycle. The air conditioner 1 is mainly configured by connecting an outdoor unit 2 and a plurality (here, two) of indoor units 6a and 6b. Here, the outdoor unit 2 and the indoor units 6 a and 6 b are connected via a liquid refrigerant communication tube 7 and a gas refrigerant communication tube 8. That is, the vapor compression refrigerant circuit 10 of the air conditioner 1 is configured by connecting the outdoor unit 2 and the indoor units 6 a and 6 b via the refrigerant communication pipes 7 and 8. The refrigerant circuit 10 is configured to be able to switch between cooling operation and heating operation by a single-stage compression refrigeration cycle using a refrigerant (here, carbon dioxide) that operates in a supercritical region. Yes.

<Indoor unit>
The indoor units 6a and 6b are installed in a room such as a building. The indoor units 6 a and 6 b are connected to each other in parallel and connected to the outdoor unit 2 via the refrigerant communication pipes 7 and 8, and constitute a refrigerant circuit 10 with the outdoor unit 2. Here, there are only two indoor units 6a and 6b, but only one indoor unit may be used, or three or more indoor units may be connected in parallel.

  Next, the configuration of the indoor units 6a and 6b will be described. Since the indoor unit 6a and the indoor unit 6b have the same configuration, only the configuration of the indoor unit 6a will be described here. For the configuration of the indoor unit 6b, the suffix “a” indicating each part of the indoor unit 6a. Is replaced with “b”, and the description is omitted.

  The indoor unit 6a mainly has an indoor expansion valve 61a and an indoor heat exchanger 62a.

-Indoor expansion valve-
The indoor expansion valve 61a depressurizes the refrigerant sent from the outdoor unit 2 through the liquid refrigerant communication pipe 7 during the cooling operation until the low pressure of the refrigeration cycle, and during the heating operation, the indoor expansion valve 61a passes through the indoor heat exchanger 62a. It is an expansion valve that adjusts the circulation amount of the high-pressure refrigerant. Here, an electric expansion valve is used as the indoor expansion valve 61a. The indoor expansion valve 61a is provided in the indoor unit liquid refrigerant pipe 63a connected to the liquid side end of the indoor heat exchanger 62a. In the indoor unit 6 a, the end of the indoor unit liquid refrigerant pipe 63 a near the liquid end of the indoor expansion valve 61 a is connected to the liquid refrigerant communication pipe 7.

-Indoor heat exchanger-
The indoor heat exchanger 62a evaporates the low-pressure refrigerant of the refrigeration cycle decompressed by the indoor expansion valve 61a during the cooling operation, and radiates the high-pressure refrigerant of the refrigeration cycle compressed by the compressor 21 during the heating operation. It is. The indoor heat exchanger 62a is connected to the end of the indoor expansion valve 61a on the gas side. Here, the indoor heat exchanger 62a is a cross-fin type fin-and-tube heat exchanger composed of heat transfer tubes and a large number of fins, and the indoor air is used as a heating source or a cooling source for the refrigeration cycle. Evaporation of the low-pressure refrigerant or heat dissipation of the high-pressure refrigerant in the refrigeration cycle is performed. The liquid-side end of the indoor heat exchanger 62a is connected to the indoor unit liquid refrigerant pipe 63a, and the gas-side end of the indoor heat exchanger 62b is connected to the indoor unit gas refrigerant pipe 64a. In the indoor unit 6 a, the end of the indoor unit gas refrigerant pipe 64 a far from the end of the indoor heat exchanger 62 a on the gas side is connected to the gas refrigerant communication pipe 8. Here, a cross fin type fin-and-tube heat exchanger is adopted as the indoor heat exchanger 62a, but other types of heat exchangers may be used.

  And the indoor air as a heating source or cooling source of the indoor heat exchanger 62a is supplied by the indoor fan 65a. Here, the indoor fan 65a is a centrifugal fan, a multiblade fan, or the like that is rotationally driven by the indoor fan electric motor 66a.

  In this way, the indoor heat exchangers 62a and 62b constitute a heat exchanger that functions as a refrigerant evaporator or a radiator.

-Indoor control unit-
Moreover, the indoor unit 6a has the indoor side control part 67a which controls operation | movement of each part which comprises the indoor unit 6a. And the indoor side control part 67a has the microcomputer, memory, etc. which were provided in order to control the indoor unit 6a. As a result, the indoor control unit 67a exchanges control signals and the like with a remote controller (not shown) for individually operating the indoor unit 6a, and communicates with the other indoor units 6b and the outdoor unit 2. Control signals and the like can be exchanged via the transmission line 91 between them.

<Outdoor unit>
The outdoor unit 2 is installed outside a building or the like. The outdoor unit 2 is connected to the indoor units 6a and 6b via the liquid refrigerant communication tube 7 and the gas refrigerant communication tube 8, and constitutes a refrigerant circuit 10 with the indoor units 6a and 6b. Here, only one outdoor unit 2 is provided, but two or more outdoor units may be connected in parallel.

  The outdoor unit 2 mainly includes a compressor 21, a first switching mechanism 22, an outdoor heat exchanger 23, a bridge circuit 24 including a second outdoor expansion valve 25, an expander 38, and a first outdoor expansion valve 28. And a receiver 29, a heat recovery heat exchanger 30, and a suction return pipe 31.

−Compressor−
Here, the compressor 21 is composed of a compressor that single-stage compresses the refrigerant with one compression element. The compressor 21 has a sealed structure in which a compression element 21a, a compressor motor 21c, and a drive shaft 21d are accommodated in a casing (not shown). The compressor motor 21c is connected to the drive shaft 21d. The drive shaft 21d is connected to the compression element 21a. Here, the compression element 21a is a volumetric compression element such as a rotary type or a scroll type. Then, the compressor 21 sucks the low-pressure refrigerant of the refrigeration cycle from the suction refrigerant pipe 41, compresses the sucked low-pressure refrigerant to the high pressure of the refrigeration cycle by the compression element 21a, and puts it into the discharge refrigerant pipe 43. It is comprised so that it may discharge. Here, the suction refrigerant pipe 41 is a refrigerant pipe for sucking the low-pressure refrigerant of the refrigeration cycle into the compression element 21a. The discharge refrigerant pipe 43 is a refrigerant pipe for sending the refrigerant discharged from the compressor 21 (here, the compression element 21a) to the first switching mechanism 22.

  The refrigerant circuit 10 is filled with refrigerating machine oil for lubricating a sliding portion such as the compression element 21a of the compressor 21 together with the refrigerant. Most of the refrigerating machine oil is collected in a casing (not shown) of the compressor 21, but a part of the refrigerating machine oil is accompanied by refrigerant from the compression element 21 a of the compressor 21 to the discharge refrigerant pipe 43. By being discharged, it may be taken out of the compressor 21. On the other hand, the discharge refrigerant pipe 43 is provided with a high-pressure side oil separation mechanism 45. The high-pressure side oil separation mechanism 45 is a mechanism that separates the refrigeration oil accompanying the high-pressure refrigerant discharged from the compression element 21a from the refrigerant and returns it to the compressor 21, and mainly includes the high-pressure side oil separator 45a and the high-pressure side oil separator 45a. And an oil return pipe 45b. The high-pressure side oil separator 45a is an oil separator that separates refrigeration oil accompanying the high-pressure refrigerant discharged from the compression element 21a from the refrigerant. The high-pressure side oil return pipe 45b is connected to the high-pressure side oil separator 45b and is a refrigerant pipe that sends the refrigeration oil separated from the high-pressure refrigerant to the suction side of the compression element 21a. The high pressure side oil return pipe 45b is provided with a high pressure side pressure reducing mechanism 45c made of a capillary tube or the like for reducing the pressure of the refrigerating machine oil flowing through the high pressure side oil return pipe 45b.

  Thus, the compressor 21 has the compression element 21a connected with the drive shaft 21d here. The compressor 21 constitutes a single-stage compression structure that compresses the low-pressure refrigerant by the single compression element 21a until the pressure becomes high.

-First switching mechanism-
The first switching mechanism 22 is a mechanism for switching the direction of refrigerant flow in the refrigerant circuit 10. During the cooling operation, the first switching mechanism 22 radiates heat from the outdoor heat exchanger 23 as a radiator for the high-pressure refrigerant compressed by the compressor 21 and the indoor heat exchangers 62a and 62b in the outdoor heat exchanger 23. It is possible to switch to a cooling operation state that functions as an evaporator for low-pressure refrigerant. That is, the first switching mechanism 22 connects the discharge side of the compressor 21 and the gas side end of the outdoor heat exchanger 23, and the suction side of the compressor 21 and the gas side of the indoor heat exchangers 62 a and 62 b. (See the solid line of the first switching mechanism 22 in FIG. 1). Further, during the heating operation, the first switching mechanism 22 uses the indoor heat exchangers 62a and 62b as a radiator for the high-pressure refrigerant compressed by the compressor 21, and the outdoor heat exchanger 23 as the indoor heat exchanger 62a, Switching to the heating operation state in which the low-pressure refrigerant radiated in 62b functions as an evaporator can be performed. That is, the first switching mechanism 22 connects the discharge side of the compressor 21 and the gas side ends of the indoor heat exchangers 62a and 62b, and also connects the suction side of the compressor 21 and the gas side of the outdoor heat exchanger 23. (See the broken line of the first switching mechanism 22 in FIG. 1). Here, the first switching mechanism 22 is composed of a four-way switching valve, and includes a suction side (here, a suction refrigerant pipe 41) of the compressor 21, a discharge side (here, a discharge refrigerant pipe 43) of the compressor 21, and an outdoor unit. The gas-side end of the heat exchanger 23 (here, the outdoor unit first gas refrigerant pipe 46) and the gas-side ends of the indoor heat exchangers 62a and 62b (here, the outdoor unit second gas refrigerant pipe). 47) is a four-way switching valve. Here, the outdoor unit first gas refrigerant pipe 46 is a refrigerant pipe that connects the first switching mechanism 22 and the gas-side end of the outdoor heat exchanger 23. The outdoor unit second gas refrigerant pipe 47 connects the first switching mechanism 22 and the gas side ends of the indoor heat exchangers 62a and 62b via the gas refrigerant communication pipe 8 and the indoor unit gas refrigerant pipes 64a and 64b. This is a refrigerant pipe. The first switching mechanism 22 is not limited to a four-way switching valve, and is configured to have the same function of switching the refrigerant flow direction as described above, for example, by combining a plurality of electromagnetic valves. It may be a thing.

  As described above, the first switching mechanism 22 includes the cooling operation state in which the refrigerant is circulated in the order of the compressor 21, the outdoor heat exchanger 23, and the indoor heat exchangers 62a and 62b, the compressor 21, and the indoor heat exchanger. The mechanism which switches between the heating operation state which circulates a refrigerant | coolant in order of 62a, 62b, and the outdoor heat exchanger 23 is comprised.

-Outdoor heat exchanger-
The outdoor heat exchanger 23 dissipates heat of the high-pressure refrigerant of the refrigeration cycle compressed by the compressor 21 during the cooling operation, and evaporates the low-pressure refrigerant of the refrigeration cycle decompressed by the second outdoor expansion valve 25 during the heating operation. It is an exchanger. The end of the outdoor heat exchanger 23 on the gas side is connected to the first switching mechanism 22 via the outdoor unit first gas refrigerant pipe 46, and the end of the outdoor heat exchanger 23 on the liquid side is connected to the outdoor The unit liquid refrigerant pipe 48 is connected. Here, the outdoor unit liquid refrigerant pipe 48 is connected to the liquid refrigerant communication pipe 7 and the indoor unit liquid refrigerant pipes 63a and 63b including the indoor expansion valves 61a and 62. And a refrigerant pipe connecting the liquid side ends of the indoor heat exchangers 62a and 62b. Here, the outdoor heat exchanger 23 is a cross-fin type fin-and-tube heat exchanger composed of heat transfer tubes and a large number of fins, and the outdoor air is used as a cooling source or a heating source for the refrigeration cycle. The heat release of the high-pressure refrigerant or the evaporation of the low-pressure refrigerant in the refrigeration cycle is performed. Here, as the outdoor heat exchanger 23, a cross-fin type fin-and-tube heat exchanger is adopted, but other types of heat exchangers may be used.

  The outdoor air as a cooling source or heating source for the outdoor heat exchanger 23 is supplied by an outdoor fan 55. Here, the outdoor fan 35 is a centrifugal fan, a multiblade fan, or the like that is rotationally driven by the outdoor fan electric motor 36.

  As described above, the outdoor heat exchanger 51 forms a heat exchanger that functions as a refrigerant radiator or an evaporator using outdoor air as a heat source.

-Bridge circuit-
The bridge circuit 24 is provided in the outdoor unit liquid refrigerant pipe 48 and is connected to a receiver inlet pipe 49 connected to the inlet of the receiver 29 and a receiver outlet pipe 50 connected to the outlet of the receiver 29. Here, the bridge circuit 24 includes three check valves 24 a, 24 b and 24 c and a second outdoor expansion valve 25. The inlet check valve 24 a is a check valve that allows only the refrigerant to flow from the outdoor heat exchanger 23 to the receiver inlet pipe 49. The inlet check valve 24 b is a check valve that allows only the refrigerant to flow from the indoor heat exchangers 62 a and 62 b to the receiver inlet pipe 49. That is, the inlet check valves 24a and 24b have a function of circulating the refrigerant from one of the outdoor heat exchanger 23 and the indoor heat exchangers 62a and 62b to the receiver inlet pipe 49. The outlet check valve 24c is a check valve that allows only refrigerant to flow from the receiver outlet pipe 50 to the indoor heat exchangers 62a and 62b. The second outdoor expansion valve 25 is an expansion valve that is fully closed during the cooling operation, and that reduces the refrigerant to the low pressure of the refrigeration cycle when the refrigerant flows from the receiver outlet pipe 50 to the outdoor heat exchanger 23 during the heating operation. . Here, an electric expansion valve is used as the second outdoor expansion valve 25. That is, the outlet check valve 24c and the second outdoor expansion valve 25 have a function of circulating the refrigerant from the receiver outlet pipe 50 to the other of the outdoor heat exchanger 23 and the indoor heat exchangers 62a and 62b through the receiver inlet pipe 49. ing. Here, the receiver inlet pipe 49 connects between the outlet end portions of the inlet check valves 24 a and 24 b of the bridge circuit 24 and the inlet of the receiver 29. The receiver outlet pipe 50 connects between the outlet check valve 24 c of the bridge circuit 24 and the inlet side end of the second outdoor expansion valve 25 and the outlet of the receiver 29.

-Expander-
Here, the expander 38 includes an expander that expands the refrigerant with one expansion element, and is provided in the receiver inlet pipe 49. One end of the expander 38 is connected to the outdoor heat exchanger 23 via the bridge circuit 24, and the other end is connected to the inlet of the receiver 29. The expander 38 has a sealed structure in which an expansion element 38a, an expander generator 38b, and an output shaft 38c are accommodated in a casing (not shown). The expander generator 38b is connected to the output shaft 38c. The output shaft 38c is connected to the expansion element 38a. Here, the expansion element 38a is a positive displacement type expansion element such as a rotary type or a scroll type. The expander 38 causes the high-pressure refrigerant of the refrigeration cycle to flow from the upstream portion of the receiver inlet pipe 49, expands the high-pressure refrigerant that has flowed in by the expansion element 38 a, and flows out to the downstream portion of the receiver inlet pipe 49. It is configured as follows. Here, since expansion of the refrigerant in the expansion element 38a is isentropic expansion, power is generated in the expansion element 38a. Then, the power generated in the expansion element 38a rotates the expander generator 38b to generate power. That is, the expander generator 38b is regeneratively driven as a generator. However, since the differential pressure between the upstream side and the downstream side of the expander 38 is small at the start of the cooling operation or heating operation, sufficient power cannot be obtained due to the expansion of the refrigerant in the expansion element 38a. . For this reason, the power generator 38b for the expander is driven by a power running that is driven as an electric motor at the start of the cooling operation or the heating operation. Although not shown here, an oil pipe for exchanging refrigerating machine oil is provided between the expander 38 and the compressor 21, and lubrication of sliding parts such as the expansion element 38a of the expander 38 is provided. Has been made.

  As described above, the expander 38 here expands the refrigerant in the expansion element 38a while performing powering driving to drive the expander generator 38b as an electric motor at the start of operation, and thereafter, the refrigerant in the expansion element 38a. It is configured to shift to regenerative driving in which the expander generator 38b is driven as a generator by the power generated by the expansion.

-First outdoor expansion valve-
The first outdoor expansion valve 28 is an expansion valve that depressurizes the refrigerant provided in the receiver inlet pipe 49 so as to bypass the expander 38. Here, an electric expansion valve is used as the first outdoor expansion valve 28. One end of the first outdoor expansion valve 28 is connected to the outdoor heat exchanger 23 via the bridge circuit 24, and the other end is connected to the inlet of the receiver 29. The first outdoor expansion valve 28 is used in an operation that does not use the expander 38. That is, the first outdoor expansion valve 28 decompresses the refrigerant radiated in the outdoor heat exchanger 23 before sending it to the receiver 29 during the cooling operation without using the expander 38. Moreover, the 1st outdoor expansion valve 28 decompresses the refrigerant | coolant thermally radiated in the indoor heat exchangers 62a and 62b before sending to the receiver 29 at the time of the heating operation which does not use the expander 38.

-Receiver-
The receiver 29 can store the excess refrigerant generated due to the difference in the refrigerant amount in the refrigerant circuit 10 between the cooling operation and the heating operation, so that the expander 38 and the first outdoor expansion valve 28 can be stored. It is a container provided in order to temporarily store the refrigerant on the downstream side, that is, after being decompressed by the expander 38 or the first outdoor expansion valve 28. The inlet of the receiver 29 is connected to a receiver inlet pipe 49, and the outlet of the receiver 29 is connected to a receiver outlet pipe 50 that extracts the refrigerant from the lower part of the receiver 29.

-Heat recovery heat exchanger, suction return pipe-
The heat recovery heat exchanger 30 is provided in the receiver outlet pipe 50 and is a heat exchanger that further dissipates heat from the liquid refrigerant separated in the receiver 29 during cooling operation or heating operation. Here, the heat recovery heat exchanger 30 is composed of a double-pipe heat exchanger or a plate heat exchanger, so that heat is exchanged between the refrigerant flowing in the heat radiation side flow path 30a and the refrigerant flowing in the evaporation side flow path 30b. It has become. The refrigerant flowing through the receiver outlet pipe 50 flows through the heat radiation side flow path 30a. Here, the refrigerant flowing through the suction return pipe 31 connected to the receiver 29 flows through the evaporation side flow path 30b so that the refrigerant is led out from the upper part of the receiver 29. That is, the heat recovery heat exchanger 30 is a heat exchanger that releases heat of the refrigerant flowing through the receiver outlet pipe 50 by the refrigerant flowing through the suction return pipe 31.

  Thus, the heat recovery heat exchanger 30 here constitutes a heat exchanger that performs heat exchange between the refrigerant flowing through the receiver outlet pipe 50 and the refrigerant flowing through the suction return pipe 31.

  Here, the suction return pipe 31 has a first suction return pipe 31a and a merging suction return pipe 31c. The first suction return pipe 31 a is a refrigerant pipe that extracts the refrigerant from the upper part of the receiver 29. Further, the merged suction return pipe 31 c merges with the suction refrigerant pipe 41. The first suction return pipe 31a is provided with a first suction return valve 31d near the inlet of the evaporation side flow path 30b of the heat recovery heat exchanger 30. The first suction return valve 31d is an expansion valve capable of opening control for reducing the pressure of the refrigerant flowing through the suction return pipe 31a until the refrigerant reaches a low pressure in the refrigeration cycle. Here, an electric expansion valve is used as the first suction return valve 31d.

  In this manner, the suction return pipe 31 constitutes a refrigerant pipe that bypasses the refrigerant from the downstream side of the expander 38 to the suction side of the compressor 21. The suction return pipe 31 is connected to the receiver 29 so as to lead the refrigerant from the upper part of the receiver 29. Further, the suction return pipe 31 is provided with a suction return valve 31d.

-Outdoor control unit, etc.-
The outdoor unit 2 is provided with various sensors. Specifically, the combined suction return pipe 31c of the suction return pipe 31 is decompressed by the first suction return valve 31d and before flowing into the evaporation side flow path 30b of the heat recovery heat exchanger 30. A saturation temperature sensor 54 that detects a suction return saturation temperature Tsh1 that is the temperature of the refrigerant flowing through the suction return pipe 31 is provided. Further, the combined suction return pipe 31c of the suction return pipe 31 detects a suction return outlet temperature Tsh2, which is the temperature of the refrigerant flowing through the suction return pipe 31 after exiting the evaporation side flow path 30b of the heat recovery heat exchanger 30. An outlet temperature sensor 55 is provided. Further, an outlet pressure sensor 57 that detects the refrigerant pressure Pex on the downstream side of the expander 38 is provided on the downstream side of the expander 38. Further, a suction pressure sensor 58 for detecting the refrigerant pressure Ps on the suction side of the compressor 21 is provided.

  The outdoor unit 2 also has an outdoor control unit 37 that controls the operation of each unit constituting the outdoor unit 2. And the outdoor side control part 37 has a microcomputer, memory, etc. which were provided in order to control the outdoor unit 2. FIG. Thereby, the outdoor side control part 37 can exchange a control signal etc. via the transmission line 91 between indoor side control parts 67a and 67b.

<Refrigerant communication pipe>
Refrigerant communication pipes 7 and 8 are refrigerant pipes constructed on site when the air conditioner 1 is installed at an installation location such as a building, and installation conditions such as the installation location and a combination of an outdoor unit and an indoor unit. Those having various lengths and tube diameters are used.

  As described above, the refrigerant circuit 10 of the air conditioner 1 is configured by connecting the outdoor unit 2, the indoor units 6 a and 6 b, and the refrigerant communication pipes 7 and 8. As described above, the air conditioner 1 mainly includes the compressor 21, the outdoor heat exchanger 23 as a radiator or an evaporator, the expander 38, and the indoor heat exchangers 62a and 62b as an evaporator or a radiator. It has the refrigerant circuit 10 comprised by connecting. Here, the refrigerant circuit 10 that can be switched between the cooling operation and the heating operation is described as an example, but the present invention is not limited to this, and only the cooling operation or the heating operation can be performed. A possible refrigerant circuit may be used.

<Power supply circuit, control unit>
The compressor 21 and the expander 38 (more specifically, the compressor motor 21c and the expander generator 38b) constituting the air conditioner 1 are connected to a commercial power supply via a power supply circuit as shown in FIG. It is connected. The power supply circuit mainly includes a first converter 92, an inverter 93, and a second converter 94. The first converter 92 is an electric circuit that converts AC power from a commercial power source into DC power and supplies it to the inverter 93. The second converter 94 is an electric circuit that converts AC power generated by the expander 38 (expander generator 38 b) into DC power and supplies it to the inverter 93. The inverter 93 is an electric circuit that converts DC power from the converters 93 and 94 into AC power and supplies the AC power to the compressor 21 (compressor motor 21c). Further, between the second converter 94 of the power supply circuit and the expander 38 (expander generator 38b), a current for detecting the current value Ig of the alternating current from the expander 38 (expander generator 38b). A sensor 95 is provided.

  The air conditioner 1 can control each device of the outdoor unit 2 and the indoor units 6a and 6b by the control unit 9 including the indoor side control units 67a and 67b and the outdoor side control unit 37. It has become. That is, the control part 9 which performs operation control of the whole air conditioning apparatus 1 including air_conditionaing | cooling operation and heating operation is comprised by the transmission line 91 which connects between indoor side control part 67a, 67b and the outdoor side control part 37. ing.

  As shown in FIG. 3, the control unit 9 is connected so that it can receive detection signals from various sensors 54, 55, 95, etc., and various devices and valves 21, 22 based on these detection signals. 25, 28, 31d, 35, 38, 61a, 61b, 65a, 65b, etc., are connected so as to be controlled.

(2) Operation and Control of Air Conditioner Next, the operation and control of the air conditioner 1 during operation using the expander 38 will be described with reference to FIGS. Here, FIG. 4 is a pressure-enthalpy diagram illustrating a refrigeration cycle during powering driving of the expander 38 at the start of operation when start control is not performed. FIG. 5 is a flowchart of activation control at the start of operation using the expander 38. FIG. 6 is a pressure-enthalpy diagram illustrating a refrigeration cycle during powering driving of the expander 38 at the start of operation when performing start-up control. In addition, operation | movement and control of the air conditioning apparatus 1 demonstrated below are performed by the control part 9. FIG.

<Cooling operation using an expander>
During the cooling operation using the expander 38, the first switching mechanism 22 is switched to the cooling operation state indicated by the solid line in FIG. Further, since the first switching mechanism 22 is switched to the cooling operation state, the second outdoor expansion valve 25 is fully closed. Further, here, in order to perform the operation using the expander 38, the first outdoor expansion valve 28 is fully closed.

  In the state of the refrigerant circuit 10, the low-pressure refrigerant of the refrigeration cycle is sucked into the compressor 21 from the suction refrigerant pipe 41, first compressed by the compression element 21 a, and discharged from the compressor 21 to the discharge refrigerant pipe 43. . Here, the high-pressure refrigerant discharged from the compressor 21 is compressed to a pressure exceeding the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIGS. 4 and 6) by the compression operation by the compression element 21a. ing. The high-pressure refrigerant discharged from the compression element 21a flows into the high-pressure side oil separator 45a, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the high-pressure side oil separator 45a flows into the high-pressure side oil return pipe 45b and is decompressed by the high-pressure side pressure reducing mechanism 45c provided in the high-pressure side oil return pipe 45b. Then, it is sent to the suction side of the compression element 21a (that is, the suction refrigerant pipe 41). Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the high-pressure side oil separator 45 a is sent to the outdoor heat exchanger 23 that functions as a refrigerant radiator through the first switching mechanism 22.

  The high-pressure refrigerant sent to the outdoor heat exchanger 23 radiates heat by exchanging heat with outdoor air supplied by the outdoor fan 35 in the outdoor heat exchanger 23.

  The high-pressure refrigerant that has radiated heat in the outdoor heat exchanger 23 flows into the receiver inlet pipe 49 through the inlet check valve 24 a of the bridge circuit 24 and then flows into the expander 38.

  The high-pressure refrigerant that has flowed into the expander 38 expands by the expansion element 38 a and then flows out from the expander 38. The expander generator 38b is rotationally driven by the power generated by the expansion of the refrigerant in the expansion element 38a to generate power. That is, the expander generator 38b is regeneratively driven to be driven as a generator. Then, the electric power generated by the expander generator 38b is supplied to the compressor motor 21c of the compressor 21 via the power supply circuit (see FIG. 2). Thereby, the driving power supplied from the commercial power source to the compressor motor 21c can be reduced.

  The refrigerant expanded in the expander 38 flows into the receiver 29 and is gas-liquid separated into a gas refrigerant and a liquid refrigerant. The gas refrigerant separated in the receiver 29 is sent to the first suction return pipe 31 a of the suction return pipe 31, and the liquid refrigerant separated in the receiver 29 is sent to the receiver outlet pipe 50.

  The gas refrigerant sent to the first suction return pipe 31a is depressurized to a low pressure by the first suction return valve 31d, and then sent to the combined suction return pipe 31c to be sent to the evaporation side channel 30b of the heat recovery heat exchanger 30. Sent to. Further, the liquid refrigerant flowing through the receiver outlet pipe 50 flows into the heat radiation side flow path 30a of the heat recovery heat exchanger 30 and radiates heat by exchanging heat with the low-pressure refrigerant flowing through the combined suction return pipe 31c. On the other hand, the low-pressure refrigerant flowing through the combined suction return pipe 31c evaporates by exchanging heat with the liquid refrigerant flowing through the heat radiation side flow path 30a of the heat recovery heat exchanger 30 to become low-pressure refrigerant flowing through the suction refrigerant pipe 41. Will join. Immediately after the expander 38 shifts from the power running drive to the recovery drive, the first suction return valve 31d is a refrigerant at the outlet on the suction return pipe 31 side of the heat recovery heat exchanger 30 (that is, the heat recovery heat exchanger 30). The opening degree is controlled so that the refrigerant at the outlet of the evaporation side flow path 30b is overheated (superheat degree control by the suction return valve). Here, the suction return superheat degree SH is obtained by subtracting the suction return saturation temperature Tsh1 from the suction return outlet temperature Tsh2. The suction return saturation temperature Tsh1 is not limited to the temperature value detected by the saturation temperature sensor 54. When a pressure sensor for detecting the refrigerant pressure on the suction side of the compressor 21 is provided, This pressure value may be read as the saturation temperature and used as the suction return saturation temperature Tsh1. Then, it was confirmed that the refrigerant at the outlet of the heat recovery heat exchanger 30 on the suction return pipe 31 side is in an overheated state (for example, the suction return superheat degree SH is a predetermined superheat degree value). Later, the first suction return valve 31d is based on the differential pressure ΔP between the refrigerant pressure Pex on the downstream side of the expander 38 and the refrigerant pressure Ps on the suction side of the compressor 21. Is controlled (differential pressure control by suction return valve). For example, the opening degree of the first suction return valve 31d can be controlled so that the differential pressure ΔP becomes a predetermined target differential pressure. Thereby, even when the length of the liquid refrigerant communication pipe 7 is long, a differential pressure for the liquid refrigerant that has exited the receiver 29 to be sent to the indoor units 6a and 6b is secured, and the upstream side of the expander 38 And the pressure difference between the downstream side can be increased.

  The liquid refrigerant dissipated in the heat recovery heat exchanger 30 is sent to the indoor expansion valves 61a and 61b through the outlet check valve 24c of the bridge circuit 24 and the liquid refrigerant communication pipe 7, and decompressed by the indoor expansion valves 61a and 61b. As a result, the refrigerant becomes a low-pressure refrigerant and is sent to the indoor heat exchangers 62a and 62b that function as an evaporator of the refrigerant.

  The low-pressure refrigerant sent to the indoor heat exchangers 62a and 62b evaporates by exchanging heat with the indoor air supplied by the indoor fans 65a and 65b in the indoor heat exchangers 62a and 62b.

  The low-pressure refrigerant evaporated in the indoor heat exchangers 62a and 62b is sent to the suction refrigerant pipe 41 through the gas refrigerant communication pipe 8 and the first switching mechanism 22, and merged with the low-pressure refrigerant sent from the suction return pipe 31. Later, it is sucked into the compressor 21 again.

<Heating operation using an expander>
During the heating operation using the expander 38, the first switching mechanism 22 is switched to the heating operation state indicated by the broken line in FIG. Further, since the first switching mechanism 22 is switched to the heating operation state, the opening degree of the second outdoor expansion valve 25 is adjusted. Further, here, in order to perform the operation using the expander 38, the first outdoor expansion valve 28 is fully closed.

  In the state of the refrigerant circuit 10, the low-pressure refrigerant of the refrigeration cycle is sucked into the compressor 21 from the suction refrigerant pipe 41, first compressed by the compression element 21 a, and discharged from the compressor 21 to the discharge refrigerant pipe 43. . Here, the high-pressure refrigerant discharged from the compressor 21 is compressed to a pressure exceeding the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIGS. 4 and 6) by the compression operation by the compression element 21a. ing. The high-pressure refrigerant discharged from the compression element 21a flows into the high-pressure side oil separator 45a, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the high-pressure side oil separator 45a flows into the high-pressure side oil return pipe 45b and is decompressed by the high-pressure side pressure reducing mechanism 45c provided in the high-pressure side oil return pipe 45b. Then, it is sent to the suction side of the compression element 21a (that is, the suction refrigerant pipe 41). Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the high-pressure side oil separator 45a passes through the first switching mechanism 22 and the gas refrigerant communication pipe 8, and the indoor heat exchangers 62a and 62b function as a refrigerant radiator. Sent to.

  The high-pressure refrigerant sent to the indoor heat exchangers 62a and 62b radiates heat by exchanging heat with indoor air supplied by the indoor fans 65a and 65b in the indoor heat exchangers 62a and 62b.

  The high-pressure refrigerant radiated in the indoor heat exchangers 62a and 62b flows into the receiver inlet pipe 49 through the liquid refrigerant communication pipe 7 and the inlet check valve 24b of the bridge circuit 24 after passing through the indoor expansion valves 61a and 61b. And flows into the expander 38.

  The high-pressure refrigerant that has flowed into the expander 38 flows out of the expander 38 after being expanded by the expansion element 38a, as in the cooling operation. The expander generator 38b is rotationally driven by the power generated by the expansion of the refrigerant in the expansion element 38a to generate power. That is, the expander generator 38b is regeneratively driven to be driven as a generator. Then, the electric power generated by the expander generator 38b is supplied to the compressor motor 21c of the compressor 21 via the power supply circuit (see FIG. 2). Thereby, the driving power supplied from the commercial power source to the compressor motor 21c can be reduced.

  The refrigerant expanded in the expander 38 flows into the receiver 29 and is gas-liquid separated into a gas refrigerant and a liquid refrigerant. The gas refrigerant separated in the receiver 29 is sent to the first suction return pipe 31 a of the suction return pipe 31, and the liquid refrigerant separated in the receiver 29 is sent to the receiver outlet pipe 50.

  The gas refrigerant sent to the first suction return pipe 31a is depressurized to a low pressure by the first suction return valve 31d, and then sent to the combined suction return pipe 31c to be sent to the evaporation side channel 30b of the heat recovery heat exchanger 30. Sent to. Further, the liquid refrigerant flowing through the receiver outlet pipe 50 flows into the heat radiation side flow path 30a of the heat recovery heat exchanger 30 and radiates heat by exchanging heat with the low-pressure refrigerant flowing through the combined suction return pipe 31c. On the other hand, the low-pressure refrigerant flowing through the combined suction return pipe 31c evaporates by exchanging heat with the liquid refrigerant flowing through the heat radiation side flow path 30a of the heat recovery heat exchanger 30 to become low-pressure refrigerant flowing through the suction refrigerant pipe 41. Will join. At this time (that is, at the time of regenerative driving in the heating operation), the superheat degree control and the differential pressure control by the suction return valve are performed as in the regenerative driving of the cooling operation.

  Then, the liquid refrigerant that has passed through the heat radiation side flow path 30a of the heat recovery heat exchanger 30 is sent to the second outdoor expansion valve 25 of the bridge circuit 24 and depressurized to a low pressure, and then the outdoor functioning as an evaporator of the refrigerant. It is sent to the heat exchanger 23.

  The low-pressure refrigerant sent to the outdoor heat exchanger 23 evaporates by exchanging heat with outdoor air supplied by the outdoor fan 35 in the outdoor heat exchanger 23. Then, the low-pressure refrigerant evaporated in the outdoor heat exchanger 23 is sent to the suction refrigerant pipe 41 through the first switching mechanism 22 and joined with the low-pressure refrigerant sent from the suction return pipe 31, and then again. It is sucked into the compressor 21.

<Startup control at the start of operation using the expander>
At the start of the cooling operation or heating operation using the expander 38 as described above, it takes time until the discharge pressure of the compressor 21 increases, that is, until the high and low differential pressure of the refrigerant circuit 10 is applied. For this reason, it takes time until the differential pressure between the upstream side and the downstream side of the expander 38 is applied. For example, when the cooling operation or the heating operation is started with the first suction return valve 31d of the suction return pipe 31 closed, as shown in FIG. 4, until the discharge pressure of the compressor 21 rises, The operating state is such that the differential pressure between the upstream side and the downstream side is small. When the differential pressure between the upstream side and the downstream side of the expander 38 is small, the current value Ig in the expander generator 38b of the expander 38 is directed from the second converter 94 to the expander generator 38b. Therefore, it is difficult to escape from the negative current state in which the current flows, and the positive current state in which the current flows from the expander generator 38b toward the second converter 94 is unlikely. For this reason, the expander 38 cannot be shifted from the power running drive to the regenerative drive, and the power running drive of the expander 38 is continued. In particular, under conditions where the outside air temperature is low (for example, the outside air temperature is about −20 ° C.), the discharge pressure of the compressor 21 is unlikely to increase, so that the power running drive of the expander 38 continues for a long time. If such a long-time power running drive of the expander 38 is repeated many times each time the operation is started, the power consumption of the air conditioner 1, that is, the running cost increases, and the performance of the air conditioner 1 decreases.

  Therefore, here, at the start of the cooling operation or the heating operation, the first suction return valve 31d provided in the suction return pipe 31 is opened to start the expander 38. Hereinafter, the startup control at the start of the operation using the expander 38 will be described in detail with reference to FIGS.

  When an instruction to start the cooling operation or the heating operation using the expander 38 is made, the control unit 9 first sets and fixes the opening degree of the first suction return valve 31d to the predetermined opening degree MVs in step ST1. . Here, the predetermined opening is an opening of 40% to 60% (the fully open state is set to 100% of the opening).

  Next, in step ST2, the control unit 9 drives the compressor 21 and power-drives the expander 38 with the first suction return valve 31d opened as described above. Then, at the time of powering driving of the expander 38 at the start of operation, the refrigerant is bypassed from the downstream side of the expander 38 to the suction side of the compressor 21 through the suction return pipe 31. Therefore, as shown in FIG. The pressure of the refrigerant on the downstream side will decrease. For this reason, even when the discharge pressure of the compressor 21 rises at the start of operation, the differential pressure between the upstream side and the downstream side of the expander 38 can be increased. As a result, the current value Ig in the expander generator 38b of the expander 38 deviates from the negative current state in which current flows from the second converter 94 toward the expander generator 38b, and the expander generator 38b. It becomes easy to be in a positive current state in which a current flows from the first to the second converter 94.

  When the control unit 9 determines in step ST3 that the current value Ig in the expander generator 38b of the expander 38 is equal to or greater than a predetermined threshold current value Igs indicating that the current value Ig is in a positive current state, In ST4, the expander 38 is shifted to regenerative drive, and the first suction return valve 31d is shifted to the superheat degree control and the differential pressure control.

  The start-up control at the start of the operation using the expander 38 makes it possible to shorten the time of powering drive of the expander 38, reduce the power consumption of the air conditioner 1, and improve the performance. Can be improved.

  Further, any refrigerant pipe that bypasses the refrigerant from the downstream side of the expander 38 to the suction side of the compressor 21 can be used as the suction return pipe, but here, the suction return pipe 31 (the first suction return pipe 31a). ) Is provided so as to lead out the refrigerant from the upper part of the receiver 29. For this reason, the refrigerant in the gaseous state can be returned to the suction side of the compressor 21 as much as possible during the power running of the expander 38 at the start of operation. Thereby, here, the differential pressure between the upstream side and the downstream side of the expander 38 is suppressed while the liquid refrigerant is prevented from returning to the suction side of the compressor 21 during the power running drive of the expander 38 at the start of operation. Can be increased.

  Further, here, the refrigerant flowing through the suction return pipe 31 (first suction return pipe 31a) can be returned to the suction side of the compressor 31 after being heated by heat exchange in the heat recovery heat exchanger 30. . Thereby, here, the differential pressure between the upstream side and the downstream side of the expander 38 is suppressed while the liquid refrigerant is prevented from returning to the suction side of the compressor 21 during the power running drive of the expander 38 at the start of operation. Can be increased.

  Further, here, since the opening of the first suction return valve 31d is set to 40 to 60% during the power running drive of the expander 38 at the start of operation, the evaporator (the indoor heat exchange during the cooling operation) is set. During the heating operation, the refrigerant is bypassed from the downstream side of the expander 38 to the suction side of the compressor 21 through the suction return pipe 31 while maintaining the circulation of the refrigerant to the outdoor heat exchanger 23) side. Can be ensured. In addition, during the regenerative drive of the expander 38 after the expander 38 has been switched from power running drive to regenerative drive (during normal cooling operation or heating operation), the superheated refrigerant is returned to the suction side of the compressor 21. Therefore, it is possible to reliably suppress the liquid refrigerant from returning to the suction side of the compressor 21 through the suction return pipe 31. Thereby, here, during the power running drive of the expander 38 at the start of operation, the refrigerant pressure in the entire refrigerant circuit 10 is circulated and the differential pressure between the upstream side and the downstream side of the expander 38 is increased. In addition, during normal operation, it is possible to reliably prevent the liquid refrigerant from returning to the suction side of the compressor 21 through the suction return pipe 31.

(3) Modification In the above embodiment, an example in which the present invention is applied to the air conditioner 1 having the refrigerant circuit 10 that performs a single-stage compression refrigeration cycle has been described. You may apply this invention with respect to the air conditioning apparatus 101 which has the refrigerant circuit 110 which performs a compression-type refrigeration cycle.

  Hereinafter, the air conditioning apparatus 101 of the present modification will be described focusing on a configuration different from the air conditioning apparatus 1 of the above embodiment.

  The air conditioner 101 is mainly configured by connecting an outdoor unit 102 and a plurality of (here, two) indoor units 6a and 6b. Here, the outdoor unit 102 and the indoor units 6 a and 6 b are connected via a liquid refrigerant communication tube 7 and a gas refrigerant communication tube 8. That is, the vapor compression refrigerant circuit 110 of the air conditioner 1 is configured by connecting the outdoor unit 102 and the indoor units 6 a and 6 b via the refrigerant communication pipes 7 and 8. The refrigerant circuit 110 is configured to be able to switch between cooling operation and heating operation by a two-stage compression refrigeration cycle using a refrigerant (here, carbon dioxide) that operates in a supercritical region. Yes.

<Indoor unit>
The indoor units 6a and 6b are installed in a room such as a building. The indoor units 6 a and 6 b are connected to each other in parallel and connected to the outdoor unit 102 via the refrigerant communication tubes 7 and 8, and constitute a refrigerant circuit 110 with the outdoor unit 102. In addition, since the structure of the indoor units 6a and 6b is the same as the indoor units 6a and 6b of the said embodiment, description is abbreviate | omitted here.

<Outdoor unit>
The outdoor unit 102 is installed outside a building or the like. The outdoor unit 102 is connected to the indoor units 6a and 6b via the liquid refrigerant communication tube 7 and the gas refrigerant communication tube 8, and constitutes a refrigerant circuit 110 with the indoor units 6a and 6b. Here, only one outdoor unit 102 is provided, but two or more outdoor units may be connected in parallel.

  The outdoor unit 102 mainly includes a compressor 121, a first switching mechanism 22, an outdoor heat exchanger 23, a bridge circuit 24 including a second outdoor expansion valve 25, an economizer heat exchanger 26, and an injection pipe 27. , An expander 38, a first outdoor expansion valve 28, a receiver 29, a heat recovery heat exchanger 30, a suction return pipe 31, an intermediate heat exchanger 32, and a second switching mechanism 33. . The first switching mechanism 22, the outdoor heat exchanger 23, the bridge circuit 24 including the second outdoor expansion valve 25, the expander 38, the first outdoor expansion valve 28, the receiver 29, the heat recovery heat exchanger 30, and the room Since the structure of the outer side control part 37 is the same as that of the outdoor unit 2 of the said embodiment, description is abbreviate | omitted here.

−Compressor−
Here, the compressor 121 is composed of a compressor that compresses the refrigerant in two stages with two compression elements. The compressor 121 has a sealed structure in which a low-stage compression element 21a, a high-stage compression element 21b, a compressor motor 21c, and a drive shaft 21d are accommodated in a casing (not shown). . The compressor motor 21c is connected to the drive shaft 21d. The drive shaft 21d is connected to the two compression elements 21a and 21b. That is, in the compressor 121, the low-stage compression element 21a and the high-stage compression element 21b are connected to a single drive shaft 21d, and the two compression elements 21a and 21b are both rotationally driven by the compressor motor 21c. It has a so-called uniaxial two-stage compression structure. Here, the compression elements 21a and 21b are volumetric compression elements such as a rotary type and a scroll type. The compressor 121 sucks the low-pressure refrigerant of the refrigeration cycle from the suction refrigerant pipe 41 and compresses the sucked low-pressure refrigerant to the intermediate pressure of the refrigeration cycle by the low-stage compression element 21a. It is configured to discharge to the tube 42. Then, the compressor 121 sucks again the intermediate-pressure refrigerant of the refrigeration cycle from the intermediate refrigerant pipe 42, compresses the sucked intermediate-pressure refrigerant to the high pressure of the refrigeration cycle by the high-stage compression element 21b, It is configured to discharge to the discharge refrigerant pipe 43. Here, the suction refrigerant pipe 41 is a refrigerant pipe for sucking the low-pressure refrigerant of the refrigeration cycle into the low-stage compression element 21a. The intermediate refrigerant pipe 42 is a refrigerant pipe for allowing the high-stage compression element 21b to suck the refrigerant having an intermediate pressure of the refrigeration cycle discharged from the low-stage compression element 21a. The discharge refrigerant pipe 43 is a refrigerant pipe for sending the refrigerant discharged from the compressor 121 (here, the high-stage compression element 21b) to the first switching mechanism 22.

  The refrigerant circuit 110 encloses refrigeration oil for lubricating sliding portions such as the compression elements 21a and 21b of the compressor 121 together with the refrigerant. Most of the refrigerating machine oil is collected in the casing (not shown) of the compressor 121, but a part of the refrigerating machine oil is accompanied by the refrigerant from the low-stage compression element 21a of the compressor 121 and the intermediate refrigerant pipe. In some cases, the refrigerant is discharged to 42 or is discharged from the high-stage compression element 21b to the discharge refrigerant pipe 43 along with the refrigerant. In contrast, the intermediate refrigerant pipe 42 is provided with an intermediate pressure side oil separation mechanism 44. The intermediate pressure side oil separation mechanism 44 is a mechanism that separates the refrigeration oil accompanying the intermediate pressure refrigerant discharged from the low-stage compression element 21a from the refrigerant and returns it to the compressor 121. And an intermediate pressure side oil return pipe 44b. The intermediate pressure side oil separator 44a is an oil separator that separates the refrigeration oil accompanying the intermediate pressure refrigerant discharged from the low-stage compression element 21a from the refrigerant. The intermediate pressure side oil return pipe 44b is connected to the intermediate pressure side oil separator 44b and is a refrigerant pipe that sends the refrigeration oil separated from the intermediate pressure refrigerant to the suction side of the high-stage compression element 21b. The intermediate pressure side oil return pipe 44b is provided with an intermediate pressure side pressure reducing mechanism 44c including a capillary tube for reducing the pressure of the refrigeration oil flowing through the intermediate pressure side oil return pipe 44b. The discharge refrigerant pipe 43 is provided with a high-pressure side oil separation mechanism 45. The high-pressure side oil separation mechanism 45 is a mechanism that separates the refrigeration oil accompanying the high-pressure refrigerant discharged from the high-stage compression element 21b from the refrigerant and returns it to the compressor 121, and mainly includes a high-pressure side oil separator 45a, And a high-pressure side oil return pipe 45b. The high-pressure side oil separator 45a is an oil separator that separates refrigeration oil accompanying the high-pressure refrigerant discharged from the high-stage compression element 21b from the refrigerant. The high-pressure side oil return pipe 45b is connected to the high-pressure side oil separator 45b and is a refrigerant pipe that sends refrigeration oil separated from the high-pressure refrigerant to the suction side of the high-stage compression element 21b. The high pressure side oil return pipe 45b is provided with a high pressure side pressure reducing mechanism 45c made of a capillary tube or the like for reducing the pressure of the refrigerating machine oil flowing through the high pressure side oil return pipe 45b.

  As described above, the compressor 121 includes the low-stage compression element 21a and the high-stage compression element 21b that are connected to the single drive shaft 21d. The compressor 121 compresses the low-pressure refrigerant by the low-stage compression element 21a until it reaches an intermediate pressure, and performs the two-stage compression that compresses the refrigerant compressed to the intermediate pressure until the high-pressure compression element 21b reaches a high pressure. A uniaxial two-stage compression structure is configured.

-Economizer heat exchanger, injection pipe-
The economizer heat exchanger 26 is a heat exchanger that is provided in the receiver inlet pipe 49 and further radiates the refrigerant that has radiated heat in the outdoor heat exchanger 23 or the indoor heat exchangers 62a and 62b. Here, the economizer heat exchanger 26 is composed of a double-pipe heat exchanger or a plate heat exchanger, so that heat is exchanged between the refrigerant flowing through the heat radiation side flow path 26a and the refrigerant flowing through the evaporation side flow path 26b. It has become. The refrigerant flowing through the receiver inlet pipe 49 flows through the heat radiation side flow path 26a. The refrigerant flowing through the injection pipe 27 branched from the receiver inlet pipe 49 flows through the evaporation side flow path 26b. That is, the economizer heat exchanger 26 is a heat exchanger that releases heat of the refrigerant flowing through the receiver inlet pipe 49 by the refrigerant flowing through the injection pipe 27.

  Here, the injection pipe 27 branches off from a portion between the end of the receiver inlet pipe 49 on the bridge circuit 24 side and the heat radiation side flow path 26 a of the economizer heat exchanger 26. The injection pipe 27 may be branched from a portion between the heat radiation side flow path 26a of the economizer heat exchanger 26 and the expander 38 (or the first outdoor expansion valve 28). Further, the injection pipe 27 joins a portion of the intermediate refrigerant pipe 42 between the intermediate heat exchanger 32 and the high stage compression element 21b. Thereby, the injection pipe 27 can branch a part of the refrigerant radiated in the outdoor heat exchanger 23 or the indoor heat exchangers 62a and 62b and send it to the high-stage compression element 21b. The injection pipe 27 is provided with an injection valve 27 a at a portion near the inlet of the evaporation side flow path 26 b of the economizer heat exchanger 26. The injection valve 27a is an expansion valve capable of opening control for reducing the refrigerant branched to the injection pipe 27 until the refrigerant reaches an intermediate pressure in the refrigeration cycle. Here, an electric expansion valve is used as the injection valve 27a.

  Thus, the injection pipe 27 has the injection valve 27a whose opening degree can be controlled, and a part of the refrigerant that has radiated heat in the outdoor heat exchanger 23 or the indoor heat exchangers 62a and 62b is branched. It is a refrigerant pipe sent to the stage compression element 21b.

−Suction return tube−
Here, the suction return pipe 31 includes a first suction return pipe 31a, a second suction return pipe 31b, and a combined suction return pipe 31c that joins the refrigerant flowing through the suction return pipes 31a and 31b. Here, the first suction return pipe 31a and the merging suction return pipe 31c are the same as the first suction return pipe 31a of the air conditioner 1 of the above embodiment, and thus the description thereof is omitted. The second suction return pipe 31b is a refrigerant pipe that branches the refrigerant flowing through the receiver outlet pipe 50 from a portion between the outlet of the receiver 29 of the outlet pipe 50 of the receiver 29 and the heat radiation side flow path 30a of the heat recovery heat exchanger 30. It is. The second suction return pipe 31b may be branched from a portion between the heat radiation side flow path 30a of the heat recovery heat exchanger 30 of the outlet pipe 50 of the receiver 29 and the end portion on the bridge circuit 24 side. The second suction return pipe 31b is provided with a second suction return valve 31e at a portion near the inlet of the evaporation side flow path 30b of the heat recovery heat exchanger 30. The second suction return valve 31e is an expansion valve capable of opening control for reducing the pressure of the refrigerant flowing through the first suction return pipe 31b until the refrigerant reaches a low pressure in the refrigeration cycle. Here, an electric expansion valve is used as the second suction return valve 31e.

-Intermediate heat exchanger, second switching mechanism-
The intermediate heat exchanger 32 is provided in the intermediate refrigerant pipe 42, and serves as a heat exchanger that functions as a radiator for the intermediate-pressure refrigerant in the refrigeration cycle that is discharged from the low-stage compression element 21a and sucked into the high-stage compression element 21b. It is a vessel. Here, the intermediate heat exchanger 32 is a cross-fin type fin-and-tube heat exchanger composed of heat transfer tubes and a large number of fins, and uses the outdoor air as a cooling source and the intermediate pressure of the refrigeration cycle. The refrigerant is dissipated. The intermediate heat exchanger 32 is integrated with the outdoor heat exchanger 23. More specifically, the intermediate heat exchanger 32 is integrated by sharing the heat transfer fin with the outdoor heat exchanger 23. Also, outdoor air as a cooling source is supplied by an outdoor fan 35 that supplies outdoor air to the outdoor heat exchanger 23. That is, the outdoor fan 35 supplies outdoor air to both the outdoor heat exchanger 23 and the intermediate heat exchanger 32.

  An intermediate heat exchanger bypass pipe 51 is connected to the intermediate refrigerant pipe 42 so as to bypass the intermediate heat exchanger 32. The intermediate heat exchanger bypass pipe 51 is a refrigerant pipe that limits the flow rate of the refrigerant flowing through the intermediate heat exchanger 32. The intermediate refrigerant pipe 42 and the intermediate heat exchanger bypass pipe 51 are provided with a second switching mechanism 33. The second switching mechanism 33 passes the intermediate-pressure refrigerant discharged from the low-stage compression element 21a to the high-stage compression element 21b after passing through the intermediate heat exchanger 32, or is discharged from the low-stage compression element 21a. This is a mechanism for switching whether intermediate-pressure refrigerant is sent to the high-stage compression element 21b without passing through the intermediate heat exchanger 32. Here, a four-way switching valve is used as the second switching mechanism 33. The intermediate heat exchanger bypass pipe 51 is provided with a bypass check valve 51a. The bypass check valve 51a is a check valve that allows only the refrigerant to flow from the second switching mechanism 33 to the high-stage compression element 21b. Further, the intermediate refrigerant pipe 42 is provided between a connection portion between the end of the intermediate heat exchanger 32 on the high-stage compression element 21b side and the end of the intermediate heat exchanger bypass pipe 51 on the high-stage compression element 21b side. An intermediate refrigerant pipe check valve 42a is provided. The intermediate refrigerant pipe check valve 42a is a check valve that allows only refrigerant to flow from the end of the intermediate heat exchanger 32 on the high-stage compression element 21b side to the high-stage compression element 21b. Further, the injection pipe 27 joins a portion of the intermediate refrigerant pipe 42 between the intermediate refrigerant pipe check valve 42a and the high stage compression element 21b.

  A first intermediate heat exchanger return pipe 52 is connected to a portion of the intermediate refrigerant pipe 42 on the low-stage compression element 21 a side of the intermediate heat exchanger 32 via a second switching mechanism 33. A second intermediate heat exchanger return pipe 53 is connected to a portion between the end of the intermediate refrigerant pipe 42 on the high-stage compression element 21b side of the intermediate heat exchanger 32 and the intermediate refrigerant pipe check valve 42a. ing. The first intermediate heat exchanger return pipe 52 is in an intermediate heat exchange heat dissipation state in which the intermediate-pressure refrigerant discharged from the low-stage compression element 21a through the intermediate heat exchanger 32 is sucked into the high-stage compression element 21b (second state in FIG. 7). When the second switching mechanism 33 is switched to the switching mechanism 33 (see the solid line), the suction side of the compressor 121 (here, the suction refrigerant pipe 41) and the low-stage compression element 21a side of the intermediate heat exchanger 32 are An intermediate heat exchange vaporization state in which the intermediate pressure refrigerant discharged from the low-stage compression element 21a through the intermediate heat exchanger bypass pipe 51 is sucked into the high-stage compression element 21b through the intermediate heat exchanger bypass pipe 51 (second state of FIG. When the second switching mechanism 33 is switched to the broken line of the switching mechanism 33), the suction side (here, the suction refrigerant pipe 41) of the compressor 21 and the low-stage compression element 21a side of the intermediate heat exchanger 32 are switched. It is a refrigerant pipe which connects an end. Further, the second intermediate heat exchanger return pipe 53 switches the indoor heat exchanger 62a when the second switching mechanism 33 is switched to the intermediate heat exchange evaporation state and the first switching mechanism 22 is switched to the heating operation state. , 62b and the outdoor heat exchanger 23 (here, the connection portion of the receiver outlet pipe 50 to the bridge circuit 24) and the end of the intermediate heat exchanger 32 on the high-stage compression element 21b side. It is. The second intermediate heat exchanger return pipe 53 is provided with an intermediate heat exchanger return valve 53a composed of an electric expansion valve, and is opened when the second switching mechanism 33 is switched to the intermediate heat exchange evaporation state. Thereby, a part of the refrigerant sent from the receiver 29 to the outdoor heat exchanger 23 is branched to the intermediate heat exchanger return pipe 53, and after being depressurized to the low pressure of the refrigeration cycle by the intermediate heat exchanger return valve 53a, The refrigerant evaporated in the heat exchanger 32 and merged with the refrigerant evaporated in the outdoor heat exchanger 22 through the suction refrigerant pipe 41. Thereby, the intermediate heat exchanger 32 switches the second switching mechanism 33 to the intermediate heat exchange heat dissipation state and fully closes the intermediate heat exchanger return valve 53a when the first switching mechanism 22 is switched to the cooling operation state. By doing so, it functions as a radiator for the intermediate-pressure refrigerant of the refrigeration cycle that is discharged from the low-stage compression element 21a and sucked into the high-stage compression element 21b. Further, the intermediate heat exchanger 32 switches the second switching mechanism 33 to the intermediate heat exchange evaporation state and opens the intermediate heat exchanger return valve 53a when the first switching mechanism 22 is switched to the heating operation state. The outdoor air functions as a refrigerant evaporator in parallel with the outdoor heat exchanger 23, using outdoor air as a heat source.

  Thus, the intermediate heat exchanger 32 is connected here between the discharge side of the low-stage compression element 21a and the suction side of the high-stage compression element 21b using outdoor air as a heat source. It is a heat exchanger that functions as a radiator for the refrigerant compressed to an intermediate pressure by 21a. In addition, the intermediate heat exchanger 32 includes the first switching mechanism 22 by providing the refrigerant circuit 110 with the intermediate heat exchanger bypass pipe 51, the second switching mechanism 33, and the intermediate heat exchanger return pipes 52 and 53. When switching to the cooling operation state, it functions as a radiator of the refrigerant compressed to the intermediate pressure by the low-stage compression element 21a, and when switching the first switching mechanism 22 to the heating operation state, the indoor heat exchanger It is a heat exchanger that functions as an evaporator for the refrigerant that has dissipated heat in 62a and 62b.

<Refrigerant communication pipe>
Refrigerant communication pipes 7 and 8 are refrigerant pipes constructed on site when air conditioning apparatus 101 is installed at an installation location such as a building, and installation conditions such as the installation location and a combination of outdoor units and indoor units. Those having various lengths and tube diameters are used.

  As described above, the refrigerant circuit 110 of the air-conditioning apparatus 101 is configured by connecting the outdoor unit 102, the indoor units 6a and 6b, and the refrigerant communication tubes 7 and 8. As described above, the air conditioner 101 mainly includes the compressor 121, the outdoor heat exchanger 23 as a radiator or an evaporator, the expander 38, and indoor heat exchangers 62a and 62b as an evaporator or a radiator. It has the refrigerant circuit 110 comprised by connecting.

<Power supply circuit, control unit>
The compressor 121 and the expander 38 (more specifically, the compressor motor 21c and the expander generator 38b) constituting the air conditioner 101 are similar to those of the air conditioner 1 of the above embodiment, as shown in FIG. It is connected to a commercial power supply through a power supply circuit as shown in FIG.

  As with the air conditioner 1 of the above embodiment, the air conditioner 101 includes the outdoor unit 102 and the indoor units 6a and 6b by the control unit 9 including the indoor side control units 67a and 67b and the outdoor side control unit 37. It is possible to control each device.

<Effect>
Also in the air conditioner 101 of the present modification having the above-described configuration, the power running drive of the expander 38 is long at the start of the operation using the expander 38, as in the air conditioner 1 of the above embodiment. By continuing over time, there are problems that the power consumption increases and the performance of the refrigeration apparatus decreases. On the other hand, this problem can be solved by performing start-up control similar to the air conditioning apparatus 1 of the said embodiment.

  The present invention can be widely applied to a refrigeration apparatus including a refrigerant circuit configured by connecting a compressor, a radiator, an expander, and an evaporator.

1 Air conditioning equipment (refrigeration equipment)
10, 110 Refrigerant circuit 21, 121 Compressor 23 Outdoor heat exchanger (heat radiator, evaporator)
29 Receiver 30 Heat recovery heat exchanger 31 Suction return pipe 31d First suction return valve (suction return valve)
38 expander 38a expansion element 38b expander generator (generator)
50 Receiver outlet pipe 62a, 62b Indoor heat exchanger (evaporator, radiator)

JP 2011-214778 A

Claims (1)

Refrigerant circuit (10, 110) configured by connecting compressor (21, 121), radiator (23, 62a, 62b), expander (38) and evaporator (62a, 62b, 23) In a refrigeration apparatus comprising:
The expander is driven as a generator by an expansion element (38a) that expands the refrigerant that has flowed in to generate power, and a power running drive that is driven as an electric motor at the start of operation, and then the power generated by the expansion element. And a regenerator (38b) that is regeneratively driven.
The refrigerant circuit further includes a suction return pipe (31) for bypassing the refrigerant from the downstream side of the expander to the suction side of the compressor,
At the start of operation, start the expander by opening the intake return valve provided in the intake return tube (31d),
The refrigerant circuit further includes a receiver (29) for temporarily storing the refrigerant on the downstream side of the expander, and a receiver outlet pipe (50) for deriving the refrigerant from the lower part of the receiver.
The suction return pipe is connected to the receiver so as to draw refrigerant from the top of the receiver;
The refrigerant circuit further includes a heat recovery heat exchanger (30) for performing heat exchange between the refrigerant flowing through the receiver outlet pipe and the refrigerant flowing through the suction return pipe.
At the time of the power running drive of the expander, the suction return valve is set to an opening of 40 to 60% (a fully opened state is set to an opening of 100%),
When the expander shifts from the power running drive to the regenerative drive, the opening degree of the suction return valve is controlled so that the refrigerant at the outlet on the suction return pipe side of the heat recovery heat exchanger is overheated. ,
After confirming that the refrigerant at the outlet on the suction return pipe side of the heat recovery heat exchanger is overheated, the refrigerant pressure on the downstream side of the expander and the refrigerant pressure on the suction side of the compressor Controlling the opening of the suction return valve based on the differential pressure between
Refrigeration equipment (1, 101).