JP2014119124A - Refrigeration device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to appropriately determine whether refrigerating machine oil is supplied from a compressor oil reservoir to an expansion mechanism via an expander oil supply pipe in a refrigeration device including a refrigerant circuit configured by connecting together a compressor, a heat sink, an expander, and an evaporator.SOLUTION: Between a compressor and an expander, an expander oil supply pipe for supplying refrigerating machine oil from a compressor oil reservoir of the compressor to an expansion mechanism of the expander and an expander oil return pipe for returning the refrigerating machine oil from an expander oil reservoir of the expander to an inlet side of the compressor are connected. It is determined whether the refrigerating machine oil is supplied from the compressor oil reservoir to the expansion mechanism on the basis of an expander oil return temperature that is a temperature of the refrigerating machine oil returning from the expander oil reservoir to the inlet side of the compressor and an evaporation temperature of refrigerant in a refrigerant circuit.

Description

  The present invention relates to a refrigeration apparatus, 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 compressor includes a compressor casing in which a compressor oil reservoir for storing refrigeration oil is formed, a compression mechanism that is accommodated in the compressor casing and that compresses the sucked refrigerant and discharges the refrigerant into the compressor casing. have. Further, the expander has an expander casing in which an expander oil reservoir for storing refrigeration oil is formed, and an expansion mechanism that is accommodated in the expander casing and expands the refrigerant that has flowed in to generate power. Yes. And between the compressor and the expander, the expander oil supply pipe for supplying the refrigerating machine oil from the compressor oil reservoir to the expansion mechanism, and the refrigerating machine oil from the expander oil reservoir to the suction side of the compressor For this purpose, an oil return pipe for an expander is connected.

  In the above refrigeration apparatus, when a large amount of refrigeration oil is discharged from the compressor into the refrigerant circuit due to transient operation or overload operation, the amount of refrigeration oil stored in the compressor oil reservoir is very small. . If it does so, since it becomes impossible to supply refrigeration oil to an expansion mechanism through the oil supply pipe for an expander from a compressor oil reservoir part, the operation of an expander will be performed in an oil-free state, and an abnormal state of a sliding part of an expansion mechanism There is a risk of problems such as wear. In addition, when such a problem occurs, dust generated due to abnormal wear of the expansion mechanism may enter the compressor through the oil return pipe for the expander, possibly damaging the compressor.

  For this reason, in order to suppress the occurrence of such a problem, it is necessary to be able to appropriately determine whether or not the refrigerating machine oil is supplied from the compressor oil reservoir to the expansion mechanism through the expansion machine oil supply pipe.

  An object of the present invention is to provide a refrigeration apparatus including a refrigerant circuit configured by connecting a compressor, a radiator, an expander, and an evaporator, and from the compressor oil reservoir to the expansion mechanism through an oil supply pipe for the expander. It is to be able to appropriately determine whether or not refrigeration oil is being supplied.

  The refrigeration apparatus according to the first aspect has a refrigerant circuit configured by connecting a compressor, a radiator, an expander, and an evaporator. The compressor has a compressor casing in which a compressor oil reservoir for storing refrigeration oil is formed, and a compression mechanism that is accommodated in the compressor casing and compresses the sucked refrigerant and discharges the refrigerant into the compressor casing. ing. The expander has an expander casing in which an expander oil reservoir for storing refrigerating machine oil is formed, and an expansion mechanism that is accommodated in the expander casing and expands the refrigerant that has flowed in to generate power. Between the compressor and the expander, an oil supply pipe for an expander for supplying refrigerating machine oil from the compressor oil reservoir to the expansion mechanism, and for returning the refrigerating machine oil from the expander oil reservoir to the suction side of the compressor An expander oil return pipe is connected. In this refrigeration apparatus, an expansion mechanism is connected from the compressor oil reservoir portion based on the expander oil return temperature, which is the temperature of the refrigeration oil returning from the expander oil reservoir portion to the suction side of the compressor, and the refrigerant evaporation temperature in the refrigerant circuit. It is determined whether or not refrigerating machine oil is being supplied.

  In the configuration for lubricating the expander as described above (that is, the configuration having the expander oil supply pipe and the expander oil return pipe), when the refrigerating machine oil supply to the expander is normally performed, The high-temperature and high-pressure refrigerating machine oil supplied to the expander from the compressor oil reservoir is decompressed to near the pressure on the suction side of the compressor through the sliding portion of the expansion mechanism and collected in the expander oil reservoir, and then the expander oil reservoir To the suction side of the compressor. However, when the refrigerating machine oil supply to the expander is not normally performed, the refrigerating machine oil is not supplied from the compressor oil reservoir to the expander. The refrigerant leaking to the expander oil reservoir through the sliding portion is reduced to near the pressure on the suction side of the compressor, and returns from the expander oil reservoir to the suction side of the compressor.

  Here, the inventors of the present application return the fluid from the expander oil reservoir to the suction side of the compressor when the refrigerating machine oil supply to the expander is normally performed and when it is not normally performed. We paid attention to the temperature difference (refrigerator oil and refrigerant here). That is, when the refrigerating machine oil supply to the expander is normally performed, the temperature of the fluid (here, refrigerating machine oil) returning from the expander oil reservoir to the intake side of the compressor is the same as the intake side of the compressor. The temperature becomes higher than the saturation temperature of the flowing refrigerant (that is, the evaporation temperature of the refrigerant in the refrigerant circuit). On the other hand, when the refrigerating machine oil supply to the expander is not normally performed, the fluid (here, refrigerant) returning from the expander oil reservoir to the suction side of the compressor is almost the same as the refrigerant flowing through the evaporator. Since the pressure is reduced to a pressure, the temperature is lower than the temperature of the refrigerating machine oil when the refrigerating machine oil supply to the expander is normally performed, and a temperature close to the evaporation temperature of the refrigerant in the refrigerant circuit.

  Using such knowledge, the inventors of the present application based on the expander oil return temperature, which is the temperature of the refrigerating machine oil returning from the expander oil reservoir to the suction side of the compressor, and the refrigerant evaporation temperature in the refrigerant circuit. The inventors have invented determining whether or not refrigeration oil is supplied from the compressor oil reservoir to the expansion mechanism.

  Thereby, it can be determined appropriately here whether refrigeration oil is supplied to the expansion mechanism from the compressor oil reservoir through the expander oil supply pipe. Further, this determination can also detect that the amount of refrigerating machine oil stored in the compressor is decreasing.

  The refrigeration apparatus according to the second aspect is the refrigeration apparatus according to the first aspect, wherein when the temperature difference between the expander oil return temperature and the evaporation temperature is equal to or less than a predetermined threshold temperature difference, the compressor oil sump is used as the expansion mechanism. It is determined that the refrigerating machine oil is not supplied.

  Here, the temperature difference between the expander oil return temperature and the evaporation temperature is when the refrigerating machine oil supply to the expander is not normally performed compared to the case where the refrigerating machine oil supply to the expander is normally performed. By using the fact that this is smaller, it is possible to determine whether or not refrigeration oil is being supplied from the compressor oil reservoir to the expansion mechanism by comparing the temperature difference between the return temperature of the expander oil and the evaporation temperature and the threshold temperature difference. Can be determined.

  In the refrigeration apparatus according to the third aspect, in the refrigeration apparatus according to the first or second aspect, the expander oil return temperature is measured by the expander oil return temperature sensor provided in the oil return pipe for the expander or the expander oil reservoir. To detect.

  Here, the expander oil return temperature can be accurately detected by providing the expander oil return temperature sensor in the expander oil return pipe or the expander oil reservoir.

  In the refrigeration apparatus according to the fourth aspect, in the refrigeration apparatus according to any of the first to third aspects, when it is determined that the refrigeration oil is not supplied from the compressor oil reservoir to the expansion mechanism, An expander stop control is performed to stop the expander.

  Here, when it is determined that the refrigerating machine oil is not supplied from the compressor oil reservoir to the expansion mechanism, the time for which the operation of the expander is performed without oiling is shortened as much as possible by stopping the expander. Thus, it is possible to prevent problems such as abnormal wear of the sliding portion of the expansion mechanism. In addition, it is possible to prevent dust generated due to abnormal wear of the expansion mechanism from entering the compressor through the oil return pipe for the expander and damaging the compressor.

  A refrigeration apparatus according to a fifth aspect is the refrigeration apparatus according to the fourth aspect, wherein the refrigerant circuit has an expansion valve that bypasses the expander, performs expansion machine stop control, and opens the expansion valve. Oil return control is performed to return the refrigeration oil dispersed in the refrigerant circuit to the compressor.

  Here, not only the expansion machine stop control is performed, but also the expansion valve that bypasses the expansion machine is opened and the oil return control is performed, so that a large amount of the refrigerant is discharged together with the refrigerant into the refrigerant circuit and dispersed in the refrigerant circuit. The refrigerating machine oil thus returned can be returned to the compressor, and the state in which the refrigerating machine oil can be supplied to the expansion mechanism can be recovered.

  In the refrigeration apparatus according to the fifth aspect, the refrigeration apparatus according to the sixth aspect performs expander restart control for restarting the expander after oil return control.

  Here, by performing the expander restart control after the oil return control, the operation of the expander can be resumed while the refrigerating machine oil is normally supplied to the expansion mechanism.

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

  In the refrigeration apparatus according to the first aspect, based on the expansion machine oil return temperature and the evaporation temperature of the refrigerant in the refrigerant circuit, whether or not the refrigeration oil is supplied to the expansion mechanism from the compressor oil reservoir through the expansion machine oil supply pipe. It can be judged appropriately.

  In the refrigeration apparatus according to the second aspect, by comparing the temperature difference between the expansion machine oil return temperature and the evaporation temperature and the threshold temperature difference, it is determined whether or not the refrigeration oil is supplied from the compressor oil reservoir to the expansion mechanism. Can be determined.

  In the refrigeration apparatus according to the third aspect, the expander oil return temperature sensor can be accurately detected by providing the expander oil return temperature sensor in the expander oil return pipe or the expander oil reservoir.

  In the refrigeration apparatus according to the fourth aspect, when it is determined that the refrigeration oil is not supplied from the compressor oil reservoir to the expansion mechanism, the expansion machine is stopped and the expansion machine is operated in an oil-free state by stopping the expansion machine. By shortening the time to be performed as much as possible, it is possible to prevent the occurrence of problems such as abnormal wear of the sliding portion of the expansion mechanism.

  In the refrigeration apparatus according to the fifth aspect, not only the expander stop control is performed, but also the expansion valve that bypasses the expander is opened and the oil return control is performed to discharge a large amount from the compressor into the refrigerant circuit together with the refrigerant. Thus, the refrigeration oil dispersed in the refrigerant circuit is returned to the compressor, and the state in which the refrigeration oil can be supplied to the expansion mechanism can be recovered.

  In the refrigeration apparatus according to the sixth aspect, by performing the expander restart control after the oil return control, it is possible to resume the operation of the expander while normally supplying the refrigeration oil to the expansion mechanism.

It is a schematic block diagram of the air conditioning apparatus as one Embodiment of the freezing apparatus concerning this invention. It is a schematic longitudinal cross-sectional view of a compressor. It is an enlarged view of the principal part of a compression mechanism. It is a schematic longitudinal cross-sectional view of an expander. It is an enlarged view of the principal part of an expansion mechanism. It is a block diagram which shows the control structure of an air conditioning apparatus. It is a flowchart of supply determination of the refrigerating machine oil to an expander, expander stop control, oil return control, and restart of an expander. 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 can be switched between a cooling operation and a heating operation by a multistage (here, two-stage) compression refrigeration cycle using a refrigerant (here, carbon dioxide) that operates in a supercritical region. It is configured to be able to.

<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 pressure of the refrigeration cycle becomes low, and during the heating operation, the indoor expansion valve 61a 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, various sensors are provided in the indoor unit 6a. Specifically, the indoor heat exchanger 62a is provided with an indoor heat exchanger temperature sensor 54a that detects an indoor heat exchanger temperature Trhx that is the temperature of the refrigerant flowing through the indoor heat exchanger 62a. Here, the indoor heat exchange temperature Trhx corresponds to the refrigerant evaporation temperature Te in the refrigerant circuit 10 during the cooling operation. The indoor unit 6a is provided with an indoor temperature sensor 55a that detects an indoor temperature Tra that is the temperature of indoor air.

  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 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. .

-Compressor-
Here, the compressor 21 is composed of a compressor that compresses the refrigerant in two stages by two compression mechanisms. As shown in FIG. 2, the compressor 21 is a hermetically sealed type in which a low-stage compression mechanism 21a, a high-stage compression mechanism 21b, a compressor motor 21c, and a drive shaft 21d are accommodated in a compressor casing 70. It has a structure. The compressor motor 21c is connected to the drive shaft 21d. The drive shaft 21d is connected to the two compression mechanisms 21a and 21b. That is, in the compressor 21, a low-stage compression mechanism 21a and a high-stage compression mechanism 21b are connected to a single drive shaft 21d, and the two compression mechanisms 21a and 21b are both rotationally driven by a compressor motor 21c. It has a so-called uniaxial two-stage compression structure. Here, as shown in FIG. 3, a rotary positive displacement compression mechanism is adopted as the compression mechanisms 21a and 21b. The compression mechanisms 21a and 21b are not limited to the rotary type compression mechanism, and various types of compression mechanisms such as a scroll type compression mechanism can be employed.

  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 intermediate pressure of the refrigeration cycle by the low-stage compression mechanism 21a, It is configured to discharge to the tube 42. Then, the compressor 21 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 mechanism 21b, The refrigerant is discharged into the compressor casing 70, and the high-pressure refrigerant discharged into the compressor casing 70 is sent to the discharge refrigerant pipe 43. That is, here, the compressor 21 is configured in a so-called high-pressure dome type in which the compressor casing 70 is filled with a high-pressure refrigerant. Here, the suction refrigerant pipe 41 is a refrigerant pipe for causing the low-stage compression mechanism 21a to suck low-pressure refrigerant in the refrigeration cycle. The intermediate refrigerant pipe 42 is a refrigerant pipe for allowing the high-stage compression mechanism 21b to suck the intermediate-pressure refrigerant discharged from the low-stage compression mechanism 21a. The discharge refrigerant pipe 43 is a refrigerant pipe for sending the refrigerant discharged from the compressor 21 (here, the high stage compression mechanism 21b) to the first switching mechanism 22.

  The refrigerant circuit 10 contains refrigeration oil for lubricating sliding portions such as the compression mechanisms 21 a and 21 b of the compressor 21 together with the refrigerant. Most of the refrigerating machine oil is stored in a compressor oil reservoir 70 a formed in the compressor casing 70. Here, the compressor oil reservoir 70 a is formed at the bottom of the vertically long cylindrical compressor casing 70. The refrigerating machine oil stored in the compressor oil reservoir 70a is sucked up by an oil pump 79 provided at the lower end of the drive shaft 21c and compressed through an oil supply passage (not shown) formed inside the drive shaft 21c. It is sent to the mechanisms 21a, 21b, etc. and used for lubricating the compression mechanisms 21a, 21b, etc. Further, a part of the refrigeration oil is discharged from the low-stage compression mechanism 21a of the compressor 21 to the intermediate refrigerant pipe 42 along with the refrigerant, or discharged from the high-stage compression mechanism 21b to the discharge refrigerant pipe 43 along with the refrigerant. As a result, the compressor 21 may be taken out. 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 for separating the refrigeration oil accompanying the intermediate pressure refrigerant discharged from the low-stage compression mechanism 21a from the refrigerant and returning it to the compressor 21, and mainly includes the intermediate pressure side oil separator 44a and the intermediate pressure side oil separator 44a. And an intermediate pressure side oil return pipe 44b. The intermediate pressure side oil separator 44a is an oil separator that separates refrigeration oil accompanying the intermediate pressure refrigerant discharged from the low-stage compression mechanism 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 mechanism 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 mechanism 21b from the refrigerant and returns it to the compressor 21, 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 mechanism 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 the refrigeration oil separated from the high-pressure refrigerant to the suction side of the high-stage compression mechanism 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 21 includes a compressor casing 70 in which a compressor oil reservoir 70a for storing refrigeration oil is formed, and compression mechanisms 21a and 21b that are accommodated in the compressor casing 70 and compress the sucked refrigerant. have. Here, the high stage compression mechanism 21 b compresses the sucked refrigerant and discharges it into the compressor casing 70. Here, the low-stage compression mechanism 21a and the high-stage compression mechanism 21b are connected to a single drive shaft 21d, whereby the compressor 21 causes the low-pressure refrigerant to pass through an intermediate pressure by the low-stage compression mechanism 21a. The uniaxial two-stage compression structure is configured to perform two-stage compression in which the refrigerant compressed to the intermediate pressure is compressed to a high pressure by the high-stage compression mechanism 21b.

-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 35. 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 23 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 by an expansion mechanism, 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. As shown in FIG. 4, the expander 38 has a sealed structure in which an expansion mechanism 38 a, an expander generator 38 b, and an output shaft 38 c are accommodated in an expander casing 80. The expander generator 38b is connected to the output shaft 38c. The output shaft 38c is connected to the expansion mechanism 38a. Here, as shown in FIG. 5, a rotary positive displacement compression mechanism is employed as the expansion mechanism 38a. The expansion mechanism 38a is not limited to a rotary expansion mechanism, and various types of expansion mechanisms such as a scroll expansion mechanism can be employed. The expander 38 allows 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 mechanism 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 mechanism 38a is isentropic expansion, power is generated in the expansion mechanism 38a. The expander generator 38b is rotationally driven by the power generated in the expansion mechanism 38a to generate power.

  Thus, the expander 38 has the expander casing 80, and the expansion mechanism 38a which expands the refrigerant | coolant which flowed in while being accommodated in the expander casing 80, and generates motive power. Further, an expander oil supply pipe 87 and an expander oil return pipe 88 for exchanging refrigeration oil are connected between the expander 38 and the compressor 21, whereby the expansion of the expander 38 is expanded. Although the mechanism 38a and the like are lubricated, the configuration for the lubrication of the expander 38 will be described later together with the detailed structure of the expander 38.

-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.

-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 mechanism 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 mechanism 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.

-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.

  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. 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. 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 functions as a heat radiator for the intermediate-pressure refrigerant of the refrigeration cycle that is discharged from the low-stage compression mechanism 21a and sucked into the high-stage compression mechanism 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 mechanism 21a to the high-stage compression mechanism 21b after passing through the intermediate heat exchanger 32, or is discharged from the low-stage compression mechanism 21a. This is a mechanism for switching whether intermediate-pressure refrigerant is sent to the high-stage compression mechanism 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 mechanism 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 mechanism 21b side and the end of the intermediate heat exchanger bypass pipe 51 on the high-stage compression mechanism 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 the refrigerant to flow from the end of the intermediate heat exchanger 32 on the high stage compression mechanism 21b side to the high stage compression mechanism 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 mechanism 21b.

  Further, a first intermediate heat exchanger return pipe 52 is connected to a portion of the intermediate refrigerant pipe 42 on the low-stage compression mechanism 21 a side of the intermediate heat exchanger 32 via a second switching mechanism 33. In addition, a second intermediate heat exchanger return pipe 53 is connected to a portion between the end portion of the intermediate heat exchanger 32 on the high-stage compression mechanism 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 mechanism 21a through the intermediate heat exchanger 32 is sucked into the high-stage compression mechanism 21b (second state in FIG. 1). When the second switching mechanism 33 is switched to the switching mechanism 33 (see the solid line), the suction side (here, the suction refrigerant pipe 41) of the compressor 121 and the low-stage compression mechanism 21a side of the intermediate heat exchanger 32 are arranged. An intermediate heat exchange evaporation state (second state in FIG. 1) in which the intermediate pressure refrigerant is sucked into the high-stage compression mechanism 21b by cutting off the connection with the end and sucking the intermediate-pressure refrigerant discharged from the low-stage compression mechanism 21a through the intermediate heat exchanger bypass pipe 51. 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 mechanism 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 mechanism 21b side. It is. The second intermediate heat exchanger return pipe 53 is provided with an intermediate heat exchange 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 reduced to the low pressure of the refrigeration cycle by the intermediate heat exchanger return valve 53a, the intermediate heat The refrigerant evaporated in the exchanger 32 and merged with the refrigerant evaporated in the outdoor heat exchanger 22 through the suction refrigerant pipe 41. Thus, 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 exchange return valve 53a when the first switching mechanism 22 is switched to the cooling operation state. As a result, it functions as a radiator for the intermediate-pressure refrigerant in the refrigeration cycle that is discharged from the low-stage compression mechanism 21a and sucked into the high-stage compression mechanism 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 exchange return valve 53a when the first switching mechanism 22 is switched to the heating operation state. It functions as a refrigerant evaporator in parallel with the outdoor heat exchanger 23 using outdoor air as a heating source.

  As described above, the intermediate heat exchanger 32 is connected between the discharge side of the low-stage compression mechanism 21a and the suction side of the high-stage compression mechanism 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 intermediate heat exchanger bypass pipe 51, the second switching mechanism 33, and the intermediate heat exchanger return pipes 52 and 53 in the refrigerant circuit 10. 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 mechanism 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 radiated heat in 62a and 62b.

-Configuration for lubricating the expander including the detailed structure of the expander-
Next, a configuration for lubricating the expander 38 including the detailed structure of the expander 38 will be described.

  Here, first, as shown in FIGS. 4 and 5, two eccentric portions 81a and 81b are formed in the upper portion of the output shaft 38c. The two eccentric portions 81a and 81b are formed to have a larger diameter than the main shaft portion 81c of the output shaft 38c. Of the two eccentric parts 81a and 81b, the lower eccentric part is the first eccentric part 81a, and the upper eccentric part is the second eccentric part 81b. The two eccentric portions 81a and 81b are both eccentric in the same direction. The outer diameter of the second eccentric part 81b is larger than the outer diameter of the first eccentric part 81a. The amount of eccentricity of the main shaft portion 81c with respect to the shaft center is larger in the second eccentric portion 81b than in the first eccentric portion 81a.

  An oil supply path 81d is formed on the output shaft 38c. The oil supply passage 81d extends along the axis of the output shaft 38c. One end of the oil supply path 81d is open to the upper end surface of the output shaft 38c. The other end of the oil supply passage 81d is bent toward the outer peripheral side and extends in the radial direction of the output shaft 38c, and opens to the outer peripheral surface of the output shaft 38c below the first eccentric portion 81a. Yes. Two oil passages 81e and 81f extending in the radial direction of the output shaft 38c are formed in the oil supply passage 81d. The first branch oil passage 81e opens on the outer peripheral surface of the first eccentric portion 81a. The second branch oil passage 81f opens on the outer peripheral surface of the second eccentric portion 81b.

  As the expansion mechanism 38a, here, a swing piston type rotary expansion mechanism, which is a kind of rotary expansion mechanism, is employed. Here, the expansion mechanism 38a is provided with two pairs of cylinders 82a and 83a and pistons 82b and 83b which are paired. The first cylinder 82a and the first piston 82b constitute a first expansion mechanism 82, and the second cylinder 83a and the second piston 83b constitute a second expansion mechanism 83. The expansion mechanism 82 and the second expansion mechanism 83 are expanded in two stages in this order. The expansion mechanism 38a is provided with a front head 84a, an intermediate plate 84b, a rear head 84c, and an upper plate 84d.

  In the expansion mechanism 38a, the front head 84a, the first cylinder 82a, the intermediate plate 84b, the second cylinder 83a, the rear head 84c, and the upper plate 84d are stacked in order from the bottom to the top. In this state, the first cylinder 82a has its lower end face closed by the front head 84a and its upper end face closed by the intermediate plate 84b. On the other hand, the second cylinder 83a has its lower end face closed by the intermediate plate 84b and its upper end face closed by the rear head 84c. Here, the inner diameter of the second cylinder 83a is larger than the inner diameter of the first cylinder 82a.

  The output shaft 38c passes through the stacked front head 84a, first cylinder 82a, intermediate plate 84b, and second cylinder 83a. The output shaft 38c has a first eccentric portion 81a located in the first cylinder 82a, and a second eccentric portion 81b located in the second cylinder 83a.

  A first piston 82b is provided in the first cylinder 82a, and a second piston 83b is provided in the second cylinder 83a. The first and second pistons 82b and 83b are both formed in an annular shape or a cylindrical shape. The outer diameter of the first piston 82b and the outer diameter of the second piston 83b are equal to each other. The inner diameter of the first piston 82b is approximately equal to the outer diameter of the first eccentric portion 81a, and the inner diameter of the second piston 83b is approximately equal to the outer diameter of the second eccentric portion 81b. The first eccentric portion 81a penetrates the first piston 82b, and the second eccentric portion 81b penetrates the second piston 83b.

  The first piston 82b has an outer peripheral surface in sliding contact with the inner peripheral surface of the first cylinder 82a, one end surface in sliding contact with the front head 84a, and the other end surface in contact with the intermediate plate 84b. A first fluid chamber 82c is formed in the first cylinder 82a between the inner peripheral surface thereof and the outer peripheral surface of the first piston 82b. On the other hand, the outer peripheral surface of the second piston 83b is in sliding contact with the inner peripheral surface of the second cylinder 83a, one end surface is in sliding contact with the rear head 84c, and the other end surface is in contact with the intermediate plate 84b. A second fluid chamber 83c is formed in the second cylinder 83a between its inner peripheral surface and the outer peripheral surface of the second piston 83b.

  Each of the first and second pistons 82b and 83b is integrally provided with one blade 82d and 83d. The blades 82d and 83d are formed in a plate shape extending in the radial direction of the pistons 82b and 83b, and project outward from the outer peripheral surfaces of the pistons 82b and 83b. The blade 82d of the first piston 82b is inserted into the bush hole 82e of the first cylinder 82a, and the blade 83d of the second piston 83b is inserted into the bush hole 83e of the second cylinder 83a. The bush holes 82e and 83e of the cylinders 82a and 83a penetrate the cylinders 82a and 83a in the thickness direction, and open to the inner peripheral surfaces of the cylinders 82a and 83a.

  Each cylinder 82a, 83a is provided with a pair of bushes 82f, 83f. Each of the bushes 82f and 83f is a small piece formed so that the inner surface is a flat surface and the outer surface is a circular arc surface. In each cylinder 82a, 83a, the pair of bushes 82f, 83f are inserted into the bush holes 82e, 83e and sandwich the blades 82d, 83d. Each bush 82f, 83f has its inner side in sliding contact with the blades 82d, 83d, and its outer side slides with the cylinders 82a, 83a. The blades 82d and 83d integral with the pistons 82b and 83b are supported by the cylinders 82a and 83a via the bushes 82f and 83f, and are rotatable and advanceable and retractable with respect to the cylinders 82a and 83a.

  The first fluid chamber 82c in the first cylinder 82a is partitioned by a first blade 82d integral with the first piston 82b, and the left side of the first blade 82d in FIG. 5 is the first high pressure chamber 82g on the high pressure side, The right side is the first low pressure chamber 82h on the low pressure side. The second fluid chamber 83c in the second cylinder 83a is partitioned by a second blade 83d integral with the second piston 83b, and the left side of the second blade 83d in FIG. 5 is a second high pressure chamber 83g on the high pressure side, The right side is the second low pressure chamber 83h on the low pressure side.

  An inflow port 82i is formed in the first cylinder 82a. The inflow port 82i opens at a position slightly on the left side of the bush 82f in FIG. 5 on the inner peripheral surface of the first cylinder 82a. The inflow port 82i can communicate with the first high pressure chamber 82g. An upstream portion of the receiver inlet pipe 49 (portion near the economizer heat exchanger 26) is connected to the inflow port 82i. For convenience of explanation, as shown in FIG. 4, the upstream portion of the receiver inlet pipe 49 is shown in a cross section where the inflow port 82 i is not shown, but the actual upstream portion of the receiver inlet pipe 49 is the inflow port. It is arranged at a position communicating with 82i.

  The second cylinder 83a has an outflow port 83i. Outflow port 83i is opened at a position slightly on the right side of bush 83f in FIG. 5 on the inner peripheral surface of second cylinder 83a. The outflow port 83i can communicate with the second low pressure chamber 83h. The outflow port 83i is connected to the downstream part of the receiver inlet pipe 49 (the part near the receiver 29). For convenience of explanation, as shown in FIG. 4, the downstream portion of the receiver inlet pipe 49 is shown in a cross section in which the outlet port 83i is not shown, but the actual downstream portion of the receiver inlet pipe 49 is the outlet port. It is arranged at a position communicating with 83i.

  A communication oil passage 84e is formed in the intermediate plate 84b. The communication oil passage 84e penetrates the intermediate plate 84b in the thickness direction. On the surface of the intermediate plate 84b on the first cylinder 82a side, one end of the communication oil passage 84e opens at a location on the right side of the first blade 82d. On the surface of the intermediate plate 84b on the second cylinder 83a side, the other end of the communication oil passage 84e is opened at a location on the left side of the second blade 83d. The communication oil passage 84e extends obliquely with respect to the thickness direction of the intermediate plate 84b, and allows the first low pressure chamber 82h and the second high pressure chamber 83g to communicate with each other.

  The front head 84a has a shape with a central portion protruding downward. A through hole is formed at the center of the front head 84a, and the output shaft 38c is inserted through the through hole. The front head 84a constitutes a sliding bearing that supports the lower portion of the first eccentric portion 81a in the output shaft 38c. In the front head 84a, a circumferential groove is formed in a lower portion of the through hole through which the main shaft portion 81c of the output shaft 38c is inserted. The circumferential groove is formed at a position facing the end portion of the oil supply passage 81d opened on the outer peripheral surface of the output shaft 38c, and constitutes a lower oil sump chamber 84f.

  A through hole is formed in the center of the rear head 84c, and the main shaft portion 81c of the output shaft 38c is inserted into the through hole. The rear head 84c constitutes a sliding bearing that supports the upper part of the second eccentric portion 81b in the output shaft 38c.

  The upper plate 84d is formed in a slightly thick disk shape, and is placed on the rear head 84c. In the upper plate 84d, a circular recess is formed at the center of the lower surface. The upper plate 84d is provided at a position where the recessed portion faces the upper end surface of the output shaft 38c. The upper plate 84d is connected to the end of the expander oil supply pipe 87. Here, the expander oil supply pipe 87 is an oil supply pipe for supplying refrigerating machine oil from the compressor oil reservoir 70a of the compressor 21 to the expansion mechanism 38a. As shown in FIG. 2, the starting end of the expander oil supply pipe 87 is connected to the compressor oil reservoir 70a. The starting end of the expander oil supply pipe 87 is connected so that the refrigerating machine oil stored in the compressor oil reservoir 70 a flows out from a position above the suction position of the oil pump 79. The end of the expander oil supply pipe 87 passes through the upper plate 84d from the upper side to the lower side and opens into the recess. The recessed portion of the upper plate 84d constitutes an upper oil reservoir chamber 84g for accumulating refrigeration oil supplied from the expander oil supply pipe 87. Further, the upper plate 84d has a concave groove 84h formed on the lower surface thereof. The recessed groove 84h extends in the outer peripheral direction of the upper plate 84d from the peripheral edge of the upper oil reservoir chamber 84g. The lower end of the upper oil sump chamber 84g communicates with the oil supply passage 81d.

  In the expansion mechanism 38a, a first oil passage 84i is formed in the rear head 84c, a second oil passage 84j is formed in the intermediate plate 84b, and a third oil passage 84k is formed in the front head 84a. The first oil passage 84i penetrates the rear head 84c in the thickness direction, and the end of the concave groove 84h communicates with the bush hole 83e of the second cylinder 83a. The second oil passage 84j penetrates the intermediate plate 84b in the thickness direction, and communicates the bush hole 83e of the second cylinder 83a with the bush hole 82e of the first cylinder 82a. In the front head 84a, one end of the third oil passage 84k opens to a portion of the upper surface of the front head 84a that faces the bush hole 82e of the first cylinder 82a. Further, in the front head 84a, the other end of the third oil passage 84k opens to the inner peripheral surface of the through hole through which the output shaft 38c is inserted. As a result, the refrigerating machine oil supplied from the compressor oil reservoir 70a (see FIG. 2) through the expander oil supply pipe 87 passes from the upper oil reservoir chamber 84g to the concave groove 84h, the first oil passage 84i, and the bush of the second cylinder 83a. Hole 83e, second oil passage 84j, bush hole 82e of first cylinder 82a, third oil passage 84k, or from upper oil sump chamber 84g to oil supply passage 81d, branch oil passages 81e, 81f, cylinders 82a, 82b In turn, the oil is supplied to each sliding portion of the expansion mechanism 38a, and then leaks out below the expansion mechanism 38a through the lower oil sump chamber 84f and is stored in the expander oil reservoir 80a formed in the expander casing 80. Here, the expander oil reservoir 80a is formed at the bottom of the expander casing 80 having a vertically long cylindrical shape. The starter of the expander oil return pipe 88 is connected to the expander oil reservoir 80a. Here, the expander oil return pipe 88 is an oil return pipe for returning the refrigeration oil from the expander oil reservoir 80 a to the suction side of the compressor 21. The starting end of the expander oil return pipe 88 is connected so that the refrigerating machine oil stored in the expander oil reservoir 80a flows out from the position near the bottom of the expander oil reservoir 80a. The end of the expander oil return pipe 88 is connected to the suction refrigerant pipe 41 as shown in FIG.

  An expander generator 38b is disposed below the expansion mechanism 38a. The expander generator 38 b includes a rotor 85 and a stator 86. The rotor 85 is connected to the lower part of the output shaft 38c. The stator 86 is fixed to the expander casing 80 and is disposed so as to face the outer peripheral surface of the rotor 85.

  As described above, the expander 38 includes the expander casing 80 in which the expander oil reservoir 80a for storing the refrigerating machine oil is formed, and the expansion that is accommodated in the expander casing 80 and expands the inflowing refrigerant to generate power. And a mechanism 38a. Between the compressor 21 and the expander 38, as a configuration for lubricating the expander 38, an expander oil supply pipe 87 for supplying refrigerating machine oil from the compressor oil reservoir 70a to the expansion mechanism 38a, and expansion An expander oil return pipe 88 for returning the refrigeration oil from the machine oil reservoir 80a to the suction side of the compressor 21 is connected. That is, the refrigerating machine oil stored in the compressor oil reservoir 70a is supplied from the compressor oil reservoir 70a to the expansion mechanism 38a of the expander 38 through the expander oil supply pipe 87, and is expanded through the sliding portion of the expansion mechanism 38a. It is stored in the reservoir 80a. Thereafter, the refrigerating machine oil stored in the expander oil reservoir 80 a returns from the expander oil reservoir 80 a to the suction side of the compressor 21 through the expander oil return pipe 88.

-Outdoor control unit, etc.-
The outdoor unit 2 is provided with various sensors. Specifically, the outdoor heat exchanger 23 is provided with an outdoor heat exchange temperature sensor 56 that detects an outdoor heat exchange temperature Tohx that is the temperature of the refrigerant flowing through the outdoor heat exchanger 23. Here, the outdoor heat exchange temperature Tohx corresponds to the refrigerant evaporation temperature Te in the refrigerant circuit 10 during the heating operation. The outdoor unit 2 is provided with an outdoor temperature sensor 57 that detects an outdoor temperature Toa that is the temperature of the outdoor air. The suction refrigerant pipe 41 is provided with a suction pressure sensor 58 that detects the pressure Ps of the low-pressure refrigerant on the suction side of the compressor 21 (here, the low-stage compression mechanism 21a). Here, the temperature value obtained by converting the pressure Ps of the low-pressure refrigerant into the saturation temperature of the refrigerant corresponds to the evaporation temperature Te of the refrigerant in the refrigerant circuit 10. Further, the intermediate refrigerant pipe 42 has an intermediate pressure sensor for detecting the pressure Pm of the intermediate pressure refrigerant of the compressor 21 (here, before being discharged from the low stage compression mechanism 21a and sucked into the high stage compression mechanism 21b). 59 is provided. The discharge refrigerant pipe 43 is provided with a discharge pressure sensor 60 that detects the pressure Pd of the high-pressure refrigerant on the discharge side of the compressor 21 (here, the high-stage compression mechanism 21b). Further, the expander oil return pipe 88 is provided with an expander oil return temperature sensor 89 that detects the expander oil return temperature Tepr, which is the temperature of the refrigerating machine oil returning from the expander oil reservoir 80a to the suction side of the compressor 21. Yes.

  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.

<Control unit>
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. 6, the control unit 9 is connected so as to receive detection signals from various sensors 54 a, 54 b, 55 a, 55 b, 56 to 60, 89, and the like, and based on these detection signals and the like. The various devices and valves 21, 22, 25, 27a, 28, 31d, 31e, 33, 35, 38, 53a, 61a, 61b, 65a, 65b and the like are connected so as to be controlled.

(2) Operation and Control of Air Conditioner Next, the operation and control of the air conditioner 1 will be described with reference to FIGS. Here, FIG. 7 is a flowchart of refrigerating machine oil supply determination to the expander 38, expander stop control, oil return control, and restart of the expander 38. In addition, operation | movement and control of the air conditioning apparatus 1 demonstrated below are performed by the control part 9. FIG.

<Cooling operation>
During the cooling operation, the first switching mechanism 22 is switched to the cooling operation state indicated by the solid line in FIG. 1, and the second switching mechanism 33 is switched to the intermediate heat exchange heat radiation state indicated by the solid line in FIG. Further, the opening degree of the injection valve 27a, the first and second suction return valves 31d and 31e, and the indoor expansion valves 61a and 61b are adjusted. Further, since the first switching mechanism 22 is switched to the cooling operation state, the second outdoor expansion valve 25 and the intermediate heat exchanger return valve 53a are fully closed. Further, since the expander 38 is used, 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, and is first compressed to the intermediate pressure of the refrigeration cycle by the low-stage compression mechanism 21a. 42 is discharged. The intermediate-pressure refrigerant discharged from the low-stage compression mechanism 21a flows into the intermediate-pressure side oil separator 44a, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the intermediate pressure refrigerant in the intermediate pressure side oil separator 44a flows into the intermediate pressure side oil return pipe 44b and is reduced in pressure by the intermediate pressure side pressure reducing mechanism 44c provided in the intermediate pressure side oil return pipe 44b. Later, it is sent to the suction side of the high-stage compression mechanism 21b. Next, the intermediate pressure refrigerant after the refrigerating machine oil is separated in the intermediate pressure side oil separator 44a is sent to the intermediate heat exchanger 32 functioning as a refrigerant radiator through the second switching mechanism 33.

  The intermediate-pressure refrigerant sent to the intermediate heat exchanger 32 radiates heat by exchanging heat with the outdoor air supplied by the outdoor fan 35 in the intermediate heat exchanger 32.

  The intermediate-pressure refrigerant that has radiated heat in the intermediate heat exchanger 32 passes through the intermediate refrigerant pipe check valve 42a, and is further cooled by joining with the intermediate-pressure refrigerant sent from the injection pipe 27 to the high-stage compression mechanism 21b. Is done. The intermediate pressure refrigerant that has been injected from the injection pipe 27 is sent to the high-stage compression mechanism 21b.

  The intermediate-pressure refrigerant sent to the high-stage compression mechanism 21b is sucked into the high-stage compression mechanism 21b, further compressed, 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 of the refrigerant by the two-stage compression operation by the compression mechanisms 21a and 21b. The high-pressure refrigerant discharged from the high-stage compression mechanism 21b 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. The high-stage compression element 21b is sent to the suction side (that is, the intermediate refrigerant pipe 42). 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 a part thereof is branched to the injection pipe 27. Then, the high-pressure refrigerant flowing through the injection pipe 27 is reduced to an intermediate pressure by the injection valve 27 a and then sent to the evaporation side flow path 26 b of the economizer heat exchanger 26. Further, the high-pressure refrigerant flowing through the receiver inlet pipe 49 after branching to the injection pipe 27 flows into the heat radiation side flow path 26a of the economizer heat exchanger 26 and exchanges heat with the intermediate-pressure refrigerant flowing through the injection pipe 27. Go and dissipate heat. On the other hand, the intermediate-pressure refrigerant flowing through the injection pipe 27 evaporates by exchanging heat with the high-pressure refrigerant flowing through the heat radiation side flow path 26a of the economizer heat exchanger 26, and flows through the intermediate refrigerant pipe 42 as described above. It will merge with the intermediate pressure refrigerant.

  The high-pressure refrigerant that has radiated heat in the economizer heat exchanger 26 flows into the expander 38. The high-pressure refrigerant that has flowed into the expander 38 is expanded by the expansion mechanism 38 a and then flows out of the expander 38. The expander generator 38b is rotationally driven by the power generated by the expansion of the refrigerant in the expansion mechanism 38a to generate power. That is, the expander generator 38b is regeneratively driven to be driven as a generator. The electric power generated by the expander generator 38b is supplied to the compressor motor 21c of the compressor 21 via a power supply circuit (not shown). 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.

  A part of the liquid refrigerant sent to the receiver outlet pipe 50 is branched to the second suction return pipe 31b. The gas refrigerant and the liquid refrigerant sent to the first and second suction return pipes 31a and 31b are decompressed to a low pressure by the first and second suction return valves 31d and 31e, and then merged in the merge suction return pipe 31c. Then, it is sent to the evaporation side flow path 30b of the heat recovery heat exchanger 30. Further, the liquid refrigerant flowing through the receiver outlet pipe 50 after being branched to the second suction return pipe 31b flows into the heat radiation side flow path 30a of the heat recovery heat exchanger 30, and the liquid refrigerant flowing through the receiver outlet pipe 50 flows into the heat recovery heat exchanger 30. Heat is exchanged with the low-pressure refrigerant flowing through the combined suction return pipe 31c to dissipate heat. On the other hand, the low-pressure refrigerant flowing through the merged suction return pipe 31c evaporates by exchanging heat with the liquid refrigerant flowing through the heat radiation side flow path 30a of the supercooling heat exchanger 30 to become low-pressure refrigerant flowing through the intake refrigerant pipe 41. Will join.

  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>
During the heating operation, the first switching mechanism 22 is switched to the heating operation state indicated by the broken line in FIG. 1, and the second switching mechanism 33 is switched to the intermediate heat exchange evaporation state indicated by the broken line in FIG. Moreover, the opening degree of the injection valve 27a, the first suction return valve 31d, and the indoor expansion valves 61a and 61b is adjusted. Further, since the first switching mechanism 22 is switched to the heating operation state, the second suction return valve 31e is fully closed, and the opening degree of the second outdoor expansion valve 25 and the intermediate heat exchanger return valve 53a is adjusted. Further, since the expander 38 is used, 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, and is first compressed to the intermediate pressure of the refrigeration cycle by the low-stage compression mechanism 21a. 42 is discharged. The intermediate-pressure refrigerant discharged from the low-stage compression mechanism 21a flows into the intermediate-pressure side oil separator 44a, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the intermediate pressure refrigerant in the intermediate pressure side oil separator 44a flows into the intermediate pressure side oil return pipe 44b and is reduced in pressure by the intermediate pressure side pressure reducing mechanism 44c provided in the intermediate pressure side oil return pipe 44b. Later, it is sent to the suction side of the high-stage compression mechanism 21b. Next, the intermediate pressure refrigerant after the refrigerating machine oil is separated in the intermediate pressure side oil separator 44 a is different from that during cooling operation, through the second switching mechanism 33 and the intermediate heat exchanger bypass pipe 51. Without being dissipated at 32, the refrigerant is sent to a portion of the intermediate refrigerant pipe 42 between the intermediate refrigerant pipe check valve 42a and the high-stage compression element 21b.

  The intermediate-pressure refrigerant that bypasses the intermediate heat exchanger 32 is cooled by joining the intermediate-pressure refrigerant sent from the injection pipe 27 to the high-stage compression mechanism 21b. The intermediate pressure refrigerant that has been injected from the injection pipe 27 is sent to the high-stage compression mechanism 21b.

  The intermediate-pressure refrigerant sent to the high-stage compression mechanism 21b is sucked into the high-stage compression mechanism 21b, further compressed, 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 of the refrigerant by the two-stage compression operation by the compression mechanisms 21a and 21b. The high-pressure refrigerant discharged from the high-stage compression mechanism 21b 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. The high-stage compression element 21b is sent to the suction side (that is, the intermediate refrigerant pipe 42). 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. , A part thereof is branched to the injection tube 27. Then, the high-pressure refrigerant flowing through the injection pipe 27 is reduced to an intermediate pressure by the injection valve 27 a and then sent to the evaporation side flow path 26 b of the economizer heat exchanger 26. Further, the high-pressure refrigerant flowing through the receiver inlet pipe 49 after branching to the injection pipe 27 flows into the heat radiation side flow path 26a of the economizer heat exchanger 26 and exchanges heat with the intermediate-pressure refrigerant flowing through the injection pipe 27. Go and dissipate heat. On the other hand, the intermediate-pressure refrigerant flowing through the injection pipe 27 evaporates by exchanging heat with the high-pressure refrigerant flowing through the heat radiation side flow path 26a of the economizer heat exchanger 26, and flows through the intermediate refrigerant pipe 42 as described above. It will merge with the intermediate pressure refrigerant.

  The high-pressure refrigerant that has radiated heat in the economizer heat exchanger 26 flows into the expander 38. The high-pressure refrigerant that has flowed into the expander 38 is expanded by the expansion mechanism 38 a and then flows out of the expander 38. The expander generator 38b is rotationally driven by the power generated by the expansion of the refrigerant in the expansion mechanism 38a to generate power. That is, the expander generator 38b is regeneratively driven to be driven as a generator. The electric power generated by the expander generator 38b is supplied to the compressor motor 21c of the compressor 21 via a power supply circuit (not shown). 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 and the liquid refrigerant sent to the first suction return pipe 31a are depressurized to a low pressure by the first suction return valve 31d, and then the evaporation side flow path 30b of the heat recovery heat exchanger 30 through the combined suction return pipe 31c. 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 the low-pressure refrigerant and heat flowing through the merged suction return pipe 31c. Replace and dissipate heat. On the other hand, the low-pressure refrigerant flowing through the merged suction return pipe 31c evaporates by exchanging heat with the liquid refrigerant flowing through the heat radiation side flow path 30a of the supercooling heat exchanger 30 to become low-pressure refrigerant flowing through the intake refrigerant pipe 41. Will join.

  The liquid refrigerant radiated in the heat recovery heat exchanger 30 is sent to the second outdoor expansion valve 25 of the bridge circuit 24 and a part thereof is sent to the second intermediate heat exchanger return pipe 53. And the refrigerant | coolant which flows through the 2nd intermediate | middle heat exchanger return pipe | tube 53 is sent to the intermediate | middle heat exchanger 32 which functions as an evaporator of a refrigerant | coolant, after being pressure-reduced to low pressure by the intermediate | middle heat exchanger return valve 53a. The refrigerant sent to the second outdoor expansion valve 25 is reduced to a low pressure by the second outdoor expansion valve 25 and then sent to the outdoor heat exchanger 23 that functions as an evaporator for the refrigerant.

  The low-pressure refrigerant sent to the intermediate heat exchanger 32 evaporates by exchanging heat with the outdoor air supplied by the outdoor fan 35 in the intermediate heat exchanger 32. The low-pressure refrigerant sent to the outdoor heat exchanger 23 also evaporates by exchanging heat with the outdoor air supplied by the outdoor fan 35 in the outdoor heat exchanger 23. 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 merged with the low-pressure refrigerant evaporated in the intermediate heat exchanger 32. It is sucked into the compressor 21 again.

<Supply of refrigeration oil to the expander>
During the cooling operation and the heating operation, the refrigerating machine oil is supplied to the expander 38 by the expander oil supply pipe 87 and the expander oil return pipe 88 connected between the expander 38 and the compressor 21. Thus, the expansion mechanism 38a and the like are lubricated. That is, the refrigerating machine oil stored in the compressor oil reservoir 70a is supplied from the compressor oil reservoir 70a to the expansion mechanism 38a of the expander 38 through the expander oil supply pipe 87, and is expanded through the sliding portion of the expansion mechanism 38a. It is stored in the reservoir 80a. Thereafter, the refrigerating machine oil stored in the expander oil reservoir 80 a returns from the expander oil reservoir 80 a to the suction side of the compressor 21 through the expander oil return pipe 88.

  However, if a large amount of refrigerating machine oil is discharged from the compressor 21 into the refrigerant circuit 10 by the transient operation or the overload operation, the amount of refrigerating machine oil stored in the compressor oil reservoir 70a is very small. If it does so, since it becomes impossible to supply refrigerating machine oil to the expansion mechanism 38a through the oil supply pipe | tube 87 for an expander from the compressor oil reservoir part 70a, the driving | running of the expander 38 will be performed in an oil-free state, and the expansion mechanism 38a There is a risk of problems such as abnormal wear of sliding parts. In addition, when such a problem occurs, dust generated due to abnormal wear of the expansion mechanism 38a may enter the compressor 21 through the expander oil return pipe 88, possibly damaging the compressor 21.

  For this reason, in order to suppress the occurrence of such a problem, it is necessary to appropriately determine whether or not refrigeration oil is being supplied from the compressor oil reservoir 70a to the expansion mechanism 38a through the expander oil supply pipe 87. .

  Therefore, here, based on the expander oil return temperature Tepr, which is the temperature of the refrigerating machine oil returning from the expander oil reservoir 80a to the suction side of the compressor 21, and the refrigerant evaporation temperature Te in the refrigerant circuit 10, the compressor oil sump section. It is determined whether or not refrigeration oil is supplied from 70a to the expansion mechanism 38a. Hereinafter, the supply determination of the refrigerating machine oil to the expander 38 will be described in detail with reference to FIG. 7 including the expander stop control, the oil return control, and the restart of the expander 38 that are subsequently performed.

-Temperature detection-
During the cooling operation or the heating operation, the control unit 9 first detects the expander oil return temperature Tepr and the evaporation temperature Te in step ST1. Here, the expander oil return temperature Tepr is detected by an expander oil return temperature sensor 89 provided in the expander oil return pipe 88. The evaporation temperature Te is detected by the indoor heat exchange temperature sensors 54a and 54b that detect the indoor heat exchange temperature Trhx during the cooling operation, and by the outdoor heat exchange temperature sensor 56 that detects the outdoor heat exchange temperature Tohx during the heating operation. Detected. Further, as the evaporation temperature Te, a temperature value obtained by converting the pressure Ps of the low-pressure refrigerant detected by the suction pressure sensor 58 into the saturation temperature of the refrigerant is used (in this case, both during the cooling operation and the heating operation). Can be used).

  If the expander oil return temperature Tepr and the evaporation temperature Te are detected in step ST1, the process proceeds to the following step ST2.

-Judgment of insufficient supply of refrigerating machine oil to expander-
Next, in step ST2, the control unit 9 determines whether or not refrigeration oil is supplied from the compressor oil reservoir 70a to the expansion mechanism 38a based on the expander oil return temperature Tepr and the evaporation temperature Te.

  Here, in the configuration for lubricating the expander 38 (that is, the configuration having the expander oil supply pipe 87 and the expander oil return pipe 88), the refrigerating machine oil is normally supplied to the expander 38. In this case, the refrigerating machine oil supplied from the compressor oil reservoir 70a to the expander 38 is accumulated in the expander oil reservoir 80a through the sliding portion of the expansion mechanism 38a, and then the suction side of the compressor 21 from the expander oil reservoir 80a. Return to. However, when the refrigerating machine oil supply to the expander 38 is not normally performed, the refrigerating machine oil is not supplied from the compressor oil reservoir 70a to the expander 38, so that the refrigerating machine oil does not accumulate in the expander oil reservoir 80a. The refrigerant leaking to the expander oil reservoir 80a through the sliding portion of the expansion mechanism 38a returns from the expander oil reservoir 80a to the suction side of the compressor 21.

  Then, the inventors of the present application return fluid from the expander oil reservoir 80a to the suction side of the compressor 21 when the refrigerating machine oil supply to the expander 38 is normally performed and when it is not normally performed (here) Then, we focused on the difference in the temperature of the refrigerating machine oil or refrigerant (here, the expander oil return temperature Tepr). That is, when the refrigerating machine oil supply to the expander 38 is normally performed, the temperature (expanding machine oil return temperature) of the fluid (here, refrigerating machine oil) returning from the expander oil reservoir 80a to the suction side of the compressor 21. Tepr) is higher than the saturation temperature of the refrigerant flowing on the suction side of the compressor 21 (that is, the evaporation temperature of the refrigerant in the refrigerant circuit 10). On the other hand, when the refrigerating machine oil supply to the expander 38 is not normally performed, the fluid (here, refrigerant) returning from the expander oil reservoir 80a to the suction side of the compressor 21 is sucked into the compressor 21. Since the pressure is reduced to substantially the same pressure as that of the refrigerant flowing on the side, the refrigerant evaporating temperature Te in the refrigerant circuit 10 is lower than the temperature of the refrigerating machine oil when the refrigerating machine oil supply to the expander 38 is normally performed. The temperature is close to.

  As described above, the determination as to whether or not the refrigerating machine oil is supplied from the compressor oil reservoir 70a to the expansion mechanism 38a in step ST2 utilizes the above knowledge.

  Here, when the temperature difference ΔT between the expander oil return temperature Tepr and the evaporation temperature Te is equal to or less than a predetermined threshold temperature difference ΔTs, the refrigerating machine oil is not supplied from the compressor oil reservoir 70a to the expansion mechanism 38a. Judgment is made. That is, here, the temperature difference ΔT between the expander oil return temperature Tepr and the evaporation temperature Te indicates that the refrigerating machine oil supply to the expander 38 is greater than that when the refrigerating machine oil supply to the expander 38 is normally performed. By making use of the fact that it is smaller when it is not normally performed, a comparison is made between the temperature difference ΔT between the expander oil return temperature Tepr and the evaporation temperature Te and the threshold temperature difference ΔTs. It is determined whether or not the refrigerating machine oil is supplied to the expansion mechanism 38a.

  Thereby, here, it can be appropriately determined whether or not the refrigeration oil is supplied from the compressor oil reservoir 70a to the expansion mechanism 38a through the expander oil supply pipe 87. Moreover, it can also be detected by this determination that the storage amount of the refrigerating machine oil in the compressor 21 is reduced. Further, as described above, since the expander oil return temperature sensor 89 is provided in the expander oil return pipe 88, the expander oil return temperature Tepr can be accurately detected.

  In step ST2, when it is determined that the refrigerating machine oil is not supplied from the compressor oil reservoir 70a to the expansion mechanism 38a, the process proceeds to the following step ST3.

-Expander stop control-
Next, the control part 9 performs expander stop control which stops the expander 38 in step ST3. That is, here, in step ST2, when it is determined that the refrigerating machine oil is not supplied from the compressor oil reservoir 70a to the expansion mechanism 38a, the expander 38 is stopped.

  As a result, the time during which the expander 38 is operated in an oil-free state can be shortened as much as possible to prevent problems such as abnormal wear of the sliding portion of the expansion mechanism 38a. In addition, it is possible to prevent dust generated due to abnormal wear of the expansion mechanism 38a from entering the compressor 21 through the expander oil return pipe 88 and damaging the compressor 21.

  And in step ST3, when stopping the expander 38, the process of the following step ST4 is also performed.

-Oil return control-
Next, in step ST4, the controller 9 performs oil return control for opening the first outdoor expansion valve 28, which is an expansion valve that bypasses the expander 38, and returning the refrigeration oil dispersed in the refrigerant circuit 10 to the compressor 21. . That is, here, not only the expander stop control in step ST3 is performed, but also the refrigerant circuit 10 is supplied together with the refrigerant from the compressor 21 by opening the first outdoor expansion valve 28 that bypasses the expander 38 and performing oil return control. The refrigerating machine oil discharged in a large amount and dispersed in the refrigerant circuit 10 is returned to the compressor 21. Specifically, in order to temporarily increase the circulation flow rate of the refrigerant in the refrigerant circuit 10, the first outdoor expansion valve 28 is set to an opening degree close to full open while the expander 38 is stopped, and the compressor The operation of increasing the number of rotations 21 to a number close to the maximum number of rotations is performed for a predetermined time.

  Thereby, the amount of refrigerating machine oil stored in the compressor 21 (that is, the amount of refrigerating machine oil stored in the compressor oil reservoir 70a) increases, and the refrigerating machine oil can be supplied to the expansion mechanism 38a. Can be recovered.

  And after performing oil return control in step ST4, it transfers to the process of the following step ST5.

-Restart of the expander-
Next, the control part 9 performs expander restart control which restarts the expander 38 in step ST5. That is, here, the expander restart control is performed after the oil return control in step ST4. Specifically, the expander 38 is started and the first outdoor expansion valve 28 that bypasses the expander 38 is fully closed.

  Thereby, the operation of the expander 38 can be resumed while the refrigerating machine oil is normally supplied to the expansion mechanism 38a.

(3) Modification 1
In the above embodiment (see FIG. 1), the expander oil return temperature sensor 89 for detecting the expander oil return temperature Tepr is provided in the expander oil return pipe 88, but the present invention is not limited to this.

  For example, the expander oil return temperature sensor 89 may be provided at the bottom of the expander casing 80 as shown by a two-dot chain line in FIG.

  Even in this case, it is possible to obtain the same effect as the above embodiment.

(4) Modification 2
In the above embodiment and Modification 1 (see FIG. 1), the present invention is applied to the air conditioner 1 having the refrigerant circuit 10 that performs the two-stage compression refrigeration cycle by the two-stage compression type compressor 21. However, the present invention is not limited to this.

  For example, as shown in FIG. 8, the present invention may be applied to an air conditioner 101 having a refrigerant circuit 110 that performs a single-stage compression refrigeration cycle by a single-stage compression compressor 121. Here, a configuration in which a compressor 121 having a compression mechanism 121a that compresses a low-pressure refrigerant to a high pressure is housed in a compressor casing 70 in which a compressor oil reservoir 70a is formed is employed, as in the above embodiment. Has been. Here, since the single-stage compression type compressor 121 is employed as the compressor, equipment and piping unique to the two-stage compression refrigeration cycle such as an intermediate heat exchanger are omitted in the outdoor unit 102. .

  Even in this case, it is possible to obtain the same effects as those of the above embodiment and the first modification.

(5) Modification 3
In the said embodiment and the modifications 1 and 2 (refer FIG. 4, 5), although the structure which has the two-stage expansion type expansion mechanism 38a is employ | adopted as the expander 38, it is not limited to this. .

  For example, although not shown here, a configuration having a single-stage expansion type expansion mechanism may be adopted as the expander 38.

  Even in this case, the same effects as those of the above-described embodiment and the first and second modifications can be obtained.

  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, 101 Air conditioner (refrigeration equipment)
10, 110 Refrigerant circuit 21, 121 Compressor 23 Outdoor heat exchanger (heat radiator, evaporator)
28 First outdoor expansion valve (expansion valve)
38 expander 38a expansion mechanism 62a, 62b indoor heat exchanger (evaporator, radiator)
DESCRIPTION OF SYMBOLS 70 Compressor casing 70a Compressor oil reservoir 80 Expander casing 80a Expander oil reservoir 87 Expander oil supply pipe 88 Expander oil return pipe 89 Expander oil return temperature sensor

JP 2011-214778 A

Claims (6)

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 compressor includes a compressor casing (70) formed with a compressor oil reservoir (70a) for storing refrigerating machine oil, and compresses the refrigerant accommodated and sucked in the compressor casing. And a compression mechanism (21b, 121a) for discharging
The expander includes an expander casing (80) formed with an expander oil reservoir (80a) for storing refrigerating machine oil, and expansion that generates power by expanding the refrigerant that is accommodated in the expander casing and flows in. A mechanism (38a),
Between the compressor and the expander, an expander oil supply pipe (87) for supplying refrigerating machine oil from the compressor oil reservoir to the expansion mechanism, and refrigerating machine oil from the expander oil reservoir An expander oil return pipe (88) for returning to the suction side of the compressor is connected,
Based on the expander oil return temperature, which is the temperature of the refrigerating machine oil returning from the expander oil reservoir to the suction side of the compressor, and the evaporation temperature of the refrigerant in the refrigerant circuit, the compressor oil reservoir is refrigerated to the expansion mechanism. Determine if machine oil is being supplied,
Refrigeration equipment (1, 101). When the temperature difference between the expander oil return temperature and the evaporation temperature is equal to or less than a predetermined threshold temperature difference, it is determined that no refrigerating machine oil is supplied from the compressor oil reservoir (70a) to the expansion mechanism (38a). To
The refrigeration apparatus (1, 101) according to claim 1. The expander oil return temperature is detected by an expander oil return temperature sensor (89) provided in the expander oil return pipe (87) or the expander oil reservoir (80a).
The refrigeration apparatus (1, 101) according to claim 1 or 2. When it is determined that no refrigeration oil is supplied from the compressor oil reservoir (70a) to the expansion mechanism (38a), an expander stop control is performed to stop the expander (38).
The refrigeration apparatus (1, 101) according to any one of claims 1 to 3. The refrigerant circuit (10, 110) has an expansion valve (28) that bypasses the expander (38),
Performing the expander stop control and performing the oil return control for opening the expansion valve and returning the refrigeration oil dispersed in the refrigerant circuit to the compressor (21, 121).
The refrigeration apparatus (1, 101) according to claim 4. After the oil return control, an expander restart control for restarting the expander (38) is performed.
The refrigeration apparatus (1, 101) according to claim 5.

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