JP6653464B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to a refrigerating apparatus in which a refrigerant circuit includes a compression unit, a gas cooler, a main throttle unit, and an evaporator.

  Conventionally, in a refrigerating apparatus, a refrigerating cycle is constituted by a compression unit, a gas cooler, a throttle unit, an evaporator, and the like. Evaporate. The surrounding air is cooled by the evaporation of the refrigerant at this time.

  In recent years, in this type of refrigeration apparatus, CFC-based refrigerants cannot be used due to natural environmental problems and the like. For this reason, refrigeration systems that use carbon dioxide, which is a natural refrigerant, as a substitute for a CFC refrigerant have been developed. It is known that a carbon dioxide refrigerant is a refrigerant having a large difference between high and low pressures and has a low critical pressure, and the high pressure side of a refrigerant cycle is brought into a supercritical state by compression (for example, see Patent Document 1).

  Also, in a heat pump device constituting a water heater, a carbon dioxide refrigerant that can obtain an excellent heating effect in a gas cooler has come to be used. In that case, the refrigerant discharged from the gas cooler is expanded in two stages, and There has also been developed one in which a gas-liquid separator is interposed between expansion devices to enable gas injection into a compressor (for example, see Patent Document 2).

Japanese Patent Publication No. 7-18602 JP 2007-178042 A

  However, in the refrigerating apparatus using the above-described carbon dioxide refrigerant, the inside of the refrigerator is cooled by using an endothermic effect in an evaporator installed in a showcase or the like, but the outside air temperature (heat source temperature on the gas cooler side) is high. , The temperature of the refrigerant at the outlet of the gas cooler may increase. In this case, the specific enthalpy at the evaporator inlet becomes large, so that the refrigerating capacity is significantly reduced.

  An object of the present invention is to provide a refrigeration apparatus that can secure refrigeration capacity when using a carbon dioxide refrigerant.

  In the refrigeration apparatus according to the present invention, a refrigerant circuit includes a compression unit having a first rotary compression element and a second rotary compression element driven by the same rotary shaft, a gas cooler, a main throttle unit, and an evaporator. In a refrigeration system using a carbon dioxide refrigerant, the auxiliary compression unit provided in parallel with the compression unit, and the refrigerant circuit downstream of the gas cooler and upstream of the main throttle unit is connected to the refrigerant circuit. A pressure adjustment throttle unit for adjusting the pressure of the refrigerant flowing out of the gas cooler, a tank connected to the refrigerant circuit downstream of the pressure adjustment throttle unit and upstream of the main throttle unit, A split heat exchanger provided in the refrigerant circuit downstream of the tank and upstream of the main throttle means and having a first flow path and a second flow path; Be provided First auxiliary throttle means for adjusting the pressure of the refrigerant flowing out of the pipe, and flow out of a pipe provided at a position lower than the first height and pass through the second flow path of the split heat exchanger After that, the second auxiliary throttle means for adjusting the pressure of one of the refrigerants divided on the downstream side of the second flow path, the refrigerant whose pressure is adjusted by the first auxiliary throttle means, and After the refrigerant mixed with the refrigerant whose pressure has been adjusted by the second auxiliary throttle means flows through the first flow path of the split heat exchanger, it is sucked into the intermediate pressure part of the compression means and the auxiliary compression means. The auxiliary circuit and the refrigerant that has flowed out of the tank flows into the second flow path of the split heat exchanger, and after exchanging heat with the refrigerant flowing through the first flow path, downstream of the second flow path. The other of the refrigerant diverted on the side Controlling the operation of the compression circuit, the auxiliary compression means, the main throttle means, the pressure adjustment throttle means, the first auxiliary throttle means, and the second auxiliary throttle means. Control means for performing the operation.

  In the refrigeration apparatus according to the present invention, a refrigerant circuit includes a compression unit having a first rotary compression element and a second rotary compression element driven by the same rotary shaft, a gas cooler, a main throttle unit, and an evaporator. In a refrigeration system using a carbon dioxide refrigerant, the auxiliary compression unit provided in parallel with the compression unit, and the refrigerant circuit downstream of the gas cooler and upstream of the main throttle unit is connected to the refrigerant circuit. A pressure adjusting throttle means for adjusting the pressure of the refrigerant flowing out of the gas cooler, and connected to the refrigerant circuit downstream of the gas cooler and upstream of the main throttle means, An expansion unit that is provided in parallel, expands the refrigerant that has diverted after flowing out of the gas cooler, and recovers expansion energy; and a pressure adjustment throttle unit and the expansion unit. A tank connected to the refrigerant circuit on the upstream side of the main throttle unit on the upstream side and a refrigerant circuit on the downstream side of the tank and upstream of the main throttle unit, A split heat exchanger having a first flow path and a second flow path; first auxiliary throttle means for adjusting the pressure of refrigerant flowing out of a pipe provided at a first height of the tank; Flows out of a pipe provided at a position lower than the height of the split heat exchanger, and after passing through the second flow path of the split heat exchanger, one of the refrigerants diverted downstream of the second flow path. Second auxiliary throttle means for adjusting pressure, and a refrigerant in which a refrigerant whose pressure is adjusted by the first auxiliary throttle means and a refrigerant whose pressure is adjusted by the second auxiliary throttle means are mixed with the split heat. After flowing through the first flow path of the exchanger, the compression means The refrigerant flowing out of the tank and the auxiliary circuit sucked into the intermediate pressure portion and the auxiliary compression means flowed to the second flow path of the split heat exchanger, and exchanged heat with the refrigerant flowing in the first flow path. And a main circuit for causing the other of the refrigerant diverted on the downstream side of the second flow path to flow into the main throttle unit, the compression unit, the auxiliary compression unit, the main throttle unit, and the pressure adjustment throttle. Means, the first auxiliary throttle means, the second auxiliary throttle means, and control means for controlling the operation of the expansion means, wherein the expansion energy recovered by the expansion means is supplied to the auxiliary compression means. Used for compression operation.

  ADVANTAGE OF THE INVENTION According to this invention, when using a carbon dioxide refrigerant, refrigeration capacity can be ensured.

1 is a refrigerant circuit diagram of a refrigeration apparatus according to an embodiment of the present invention. PH diagram showing the operating state of the refrigeration system without an auxiliary compressor in a high-temperature environment PH diagram showing the operating state of the refrigeration system in a high-temperature environment FIG. 1 is a refrigerant circuit diagram of a refrigeration apparatus having a different configuration from FIG. PH diagram showing the operation state of the refrigeration system in the environment of the low temperature period FIG. 1 is a refrigerant circuit diagram of a refrigeration apparatus having a different configuration from FIG. 1 is a refrigerant circuit diagram of a refrigeration apparatus according to an embodiment of the present invention. PH diagram showing the operating state of the refrigeration system in a high-temperature environment PH diagram showing the operating state of the refrigeration system without an auxiliary compressor in a high-temperature environment FIG. 7 is a refrigerant circuit diagram of a refrigeration apparatus having a configuration different from that of FIG. 7.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<First embodiment>
First, a first embodiment of the present invention will be described.

(1) Configuration of Refrigeration System R FIG. 1 is a refrigerant circuit diagram of a refrigeration system R according to an embodiment to which the present invention is applied. The refrigeration apparatus R according to the present embodiment includes a refrigerator unit 3 installed in a machine room of a store such as a supermarket and a show of one or a plurality of units (only one is shown in the drawing) installed in a store of the store. The refrigerator unit 3 and the showcase 4 are connected by a refrigerant pipe (liquid pipe) 8 and a refrigerant pipe 9 via a unit outlet 6 and a unit inlet 7 to form a predetermined refrigerant circuit 1. Make up.

  The refrigerant circuit 1 uses carbon dioxide (R744), whose refrigerant pressure on the high pressure side can be equal to or higher than the critical pressure (supercritical), as the refrigerant. This carbon dioxide refrigerant is a natural refrigerant that is friendly to the global environment and takes flammability and toxicity into consideration. As the oil as the lubricating oil, for example, existing oils such as mineral oil (mineral oil), alkylbenzene oil, ether oil, ester oil, and PAG (polyalkyl glycol) are used. Each arrow shown in FIG. 1 indicates the flow of the carbon dioxide refrigerant.

  The refrigerator unit 3 includes a compressor 11 (an example of a compression unit). The compressor 11 is, for example, an internal intermediate pressure type two-stage compression type rotary compressor. The compressor 11 includes a closed container 12 and a rotary compression mechanism. The rotary compression mechanism section includes an electric element 13 as a drive element housed in an upper part of the internal space of the sealed container 12, and a first (low-stage side) rotary compression element ( A first compression element) 14 and a second (high-stage side) rotary compression element (second compression element) 16 are provided. The compressor 11 is a two-stage compressor having a first rotary compression element 14 and a second rotary compression element 16 driven by the same rotary shaft (the rotary shaft of the electric element 13). In such a two-stage compressor, the excluded volume ratio between the low stage and the high stage is determined, and the intermediate pressure (MP) is determined according to the excluded volume ratio.

  The first rotary compression element 14 of the compressor 11 compresses the low-pressure refrigerant sucked into the compressor 11 from the low-pressure side of the refrigerant circuit 1 through the refrigerant pipe 9, and increases the pressure to an intermediate pressure and discharges it. The second rotary compression element 16 sucks in the intermediate-pressure refrigerant discharged by the first rotary compression element 14, compresses the intermediate-pressure refrigerant to a high pressure, and discharges the refrigerant to the high-pressure side of the refrigerant circuit 1. The compressor 11 is a variable frequency compressor. The control device 57, which will be described later, controls the rotation speed of the first rotary compression element 14 and the second rotary compression element 16 by changing the operation frequency of the electric element 13.

  A low-stage suction port 17 communicating with the first rotary compression element 14, a low-stage discharge port 18 communicating with the interior of the closed vessel 12, and a second rotary compression element 16 are provided on a side surface of the closed container 12 of the compressor 11. A high-stage suction port 19 and a high-stage discharge port 21 are formed. One end of a refrigerant introduction pipe 22 is connected to the low-stage suction port 17 of the compressor 11, and the other end is connected to the refrigerant pipe 9 at the unit inlet 7.

  The low-pressure refrigerant gas sucked into the low-pressure portion of the first rotary compression element 14 from the low-stage suction port 17 is subjected to the first-stage compression by the first rotary compression element 14 and is increased to an intermediate pressure. Is discharged into the closed container 12. Thereby, the inside of the sealed container 12 has an intermediate pressure (MP).

  One end of an intermediate-pressure discharge pipe 23 is connected to the low-stage discharge port 18 of the compressor 11 from which the intermediate-pressure refrigerant gas is discharged in the sealed container 12, and the other end is connected to an inlet of the intercooler 24. Have been. The intercooler 24 air-cools the intermediate-pressure refrigerant discharged from the first rotary compression element 14. One end of an intermediate pressure suction pipe 26 is connected to an outlet of the intercooler 24. The other end of the intermediate pressure suction pipe 26 is branched and connected to the high-stage suction port 19 of the compressor 11 and the suction port 64 of the auxiliary compressor 60.

  The refrigerator unit 3 includes an auxiliary compressor 60 (an example of an auxiliary compression unit) provided in parallel with the compressor 11. The auxiliary compressor 60 includes an airtight container 61, an electric element 62 as a driving element housed in the internal space of the airtight container 61, and a rotary compression element 63 driven by a rotating shaft of the electric element 62. I have.

  The rotary compression element 63 compresses the intermediate-pressure refrigerant sucked from the intermediate-pressure suction pipe 26, raises the pressure to a high pressure, and discharges the refrigerant to the high-pressure side of the refrigerant circuit 1. The auxiliary compressor 60 is a variable frequency compressor. The control device 57, which will be described later, controls the rotation speed of the rotary compression element 63 by changing the operation frequency of the electric element 62.

  A suction port 64 and a discharge port 65 communicating with the rotary compression element 63 are formed on the side surface of the closed container 61. One end of the intermediate pressure suction pipe 26 is connected to the suction port 64. The discharge port 65 of the auxiliary compressor 60 is connected to the high-pressure discharge pipe 27 via a pipe.

  The intermediate-pressure (MP) refrigerant gas sucked into the second rotary compression element 16 from the high-stage suction port 19 of the compressor 11 is compressed by the second rotary compression element 16 in the second stage. It becomes high temperature and high pressure refrigerant gas.

  The intermediate-pressure (MP) refrigerant gas sucked into the rotary compression element 63 from the suction port 64 of the auxiliary compressor 60 is compressed by the rotary compression element 63 to become a high-temperature and high-pressure refrigerant gas.

  In addition, one end of a high-pressure discharge pipe 27 is connected to a high-stage discharge port 21 provided on the high-pressure chamber side of the second rotary compression element 16 of the compressor 11, and the other end of a gas cooler (radiator) 28 is connected. Connected to the entrance. Although not shown, an oil separator 20 may be provided in the middle of the high-pressure discharge pipe 27. The oil separated from the refrigerant by the oil separator is returned into the closed container 12 of the compressor 11 and the closed container 61 of the auxiliary compressor 60.

  The gas cooler 28 cools the high-pressure discharge refrigerant discharged from the compressor 11. In the vicinity of the gas cooler 28, a gas cooler blower 31 for air-cooling the gas cooler 28 is provided. In the present embodiment, the gas cooler 28 is arranged in parallel with the above-described intercooler 24, and these are arranged in the same air passage.

  One end of a gas cooler outlet pipe 32 is connected to an outlet of the gas cooler 28, and the other end of the gas cooler outlet pipe 32 is connected to an inlet of an electric expansion valve 33 (an example of a pressure adjusting throttle unit). The electric expansion valve 33 throttles and expands the refrigerant discharged from the gas cooler 28 and adjusts the high pressure side pressure of the refrigerant circuit 1 on the upstream side from the electric expansion valve 33. The outlet of the electric expansion valve 33 is connected to the upper part of the tank 36 via the tank inlet pipe 34.

  The tank 36 is a volume body having a space of a predetermined volume inside, and one end of a tank outlet pipe 37 is connected to a lower portion thereof, and the other end of the tank outlet pipe 37 is connected to the refrigerant pipe 8 at the unit outlet 6. It is connected. In the middle of the tank outlet pipe 37, a second flow path 29B of the split heat exchanger 29 is provided. This tank outlet pipe 37 constitutes a main circuit 38 in the present embodiment.

  On the other hand, the showcase 4 installed in the store is connected to refrigerant pipes 8 and 9. The showcase 4 is provided with an electric expansion valve 39 (an example of a main throttle unit) and an evaporator 41, which are sequentially connected between the refrigerant pipe 8 and the refrigerant pipe 9 (the electric expansion valve 39 is connected to the refrigerant pipe 9). The refrigerant pipe 8 side and the evaporator 41 are the refrigerant pipe 9 side). Next to the evaporator 41, a cool air circulation blower (not shown) for blowing air to the evaporator 41 is provided. The refrigerant pipe 9 is connected to the low-stage suction port 17 that communicates with the first rotary compression element 14 of the compressor 11 via the refrigerant introduction pipe 22 as described above.

  On the other hand, one end of a gas pipe 42 is connected to an upper part of the tank 36, and the other end of the gas pipe 42 is connected to an inlet of an electric expansion valve 43 (an example of a first auxiliary circuit throttle unit). . The gas pipe 42 allows the gas refrigerant to flow out of the upper portion of the tank 36 and flow into the electric expansion valve 43.

  One end of an intermediate pressure return pipe 44 is connected to the outlet of the electric expansion valve 43, and the other end of the intermediate pressure return pipe 44 is communicated with the intermediate pressure suction pipe 26 connected to the intermediate pressure section of the compressor 11. ing. In the middle of the intermediate pressure return pipe 44, a first flow path 29A of the split heat exchanger 29 is provided.

  Further, one end of the liquid pipe 46 is connected to the tank outlet pipe 37 on the downstream side of the second flow path 29B of the split heat exchanger 29. The other end of the liquid pipe 46 is connected to an intermediate pressure return pipe 44 downstream of the electric expansion valve 43. An electric expansion valve 47 (an example of a second auxiliary circuit throttle unit) is provided in the middle of the liquid pipe 46.

  The above-described electric expansion valve 43 (first auxiliary circuit throttle unit) and the electric expansion valve 47 (second auxiliary circuit throttle unit) constitute auxiliary throttle units in the present embodiment. Further, the intermediate pressure return pipe 44, the electric expansion valve 43, the electric expansion valve 47, the gas pipe 42, and the liquid pipe 46 constitute an auxiliary circuit 48 in the present embodiment.

  Thus, the electric expansion valve 33 is located downstream of the gas cooler 28 and upstream of the electric expansion valve 39. The tank 36 is located downstream of the electric expansion valve 33 and upstream of the electric expansion valve 39. Further, the split heat exchanger 29 is located downstream of the tank 36 and upstream of the electric expansion valve 39. Thereby, the refrigerant circuit 1 of the refrigeration apparatus R in the present embodiment is configured.

  Various sensors are attached to various parts of the refrigerant circuit 1.

  For example, a high-pressure sensor 49 is attached to the high-pressure discharge pipe 27. The high-pressure sensor 49 detects the high-pressure side pressure HP of the refrigerant circuit 1 (the pressure between the high-stage discharge port 21 of the compressor 11 and the inlet of the electric expansion valve 33).

  Further, for example, a low pressure sensor 51 is attached to the refrigerant introduction pipe 22. The low-pressure sensor 51 detects the low-pressure side pressure LP of the refrigerant circuit 1 (the pressure between the outlet of the electric expansion valve 39 and the low-stage suction port 17).

  Further, for example, an intermediate pressure sensor 52 is attached to the intermediate pressure return pipe 44. The intermediate pressure sensor 52 detects the intermediate pressure MP (the pressure in the intermediate pressure return pipe 44 downstream of the outlets of the electric expansion valves 43 and 47, which is the pressure in the intermediate pressure region of the refrigerant circuit 1, and the low pressure of the compressor 11). (Pressure equal to the pressure between the stage side discharge port 18 and the high stage side suction port 19).

  Further, for example, a unit outlet sensor 53 is attached to the tank outlet pipe 37 downstream of the split heat exchanger 29. The unit outlet sensor 53 detects the pressure OP in the tank 36. The pressure in the tank 36 is the pressure of the refrigerant flowing out of the refrigerator unit 3 and flowing into the electric expansion valve 39 from the refrigerant pipe 8.

  Each of the above-described sensors is connected to an input of a control device 57 (an example of a control unit) of the refrigerator unit 3 including a microcomputer. On the other hand, the output of the control device 57 includes the electric element 13 of the compressor 11, the electric element 62 of the auxiliary compressor 60, the gas cooler blower 31, the electric expansion valve 33, the electric expansion valve 43, the electric expansion valve 47, and the electric expansion valve. 39 is connected. The control device 57 controls each component on the output side based on a detection result from each sensor, setting data, and the like.

  In the following, the electric expansion valve 39 on the showcase 4 side and the above-described blower for circulating cold air will be described as being controlled by the control device 57. These are controlled by a main control device (not shown) of the store. It may be controlled by a control device (not shown) on the side of the showcase 4 that operates in cooperation with 57. Therefore, the control means in the present embodiment may be a concept including the control device 57, the control device on the showcase 4 side, the main control device described above, and the like.

(2) Operation of Refrigeration Device R Next, the operation of the refrigeration device R will be described. When the electric element 13 of the compressor 11 is driven by the control device 57, the first rotary compression element 14 and the second rotary compression element 16 rotate, and the first rotary compression element 14 A low-pressure refrigerant gas (carbon dioxide) is sucked into the low-pressure section of the air conditioner. Then, the pressure is increased to an intermediate pressure by the first rotary compression element 14 and discharged into the closed container 12. Thereby, the inside of the sealed container 12 has an intermediate pressure (MP).

  When the electric element 62 of the auxiliary compressor 60 is driven by the control device 57, the rotary compression element 63 rotates.

  Then, the intermediate-pressure gas refrigerant in the sealed container 12 enters the intercooler 24 from the low-stage discharge port 18 via the intermediate-pressure discharge pipe 23, and is air-cooled in the intercooler 24.

  The air-cooled gas refrigerant flows out of the intercooler 24 to the intermediate pressure suction pipe 26, where the gas refrigerant flows into the intermediate pressure suction pipe 26 from the intermediate pressure return pipe 44 (to be described in detail later). Mix. The mixed gas refrigerant splits in the intermediate pressure suction pipe 26 and flows into the high-stage suction port 19 (intermediate pressure section) of the compressor 11 and the suction port 64 of the auxiliary compressor 60, respectively.

  The intermediate-pressure gas refrigerant that has flowed into the high-stage suction port 19 is sucked into the second rotary compression element 16, and the second rotary compression element 16 performs second-stage compression to generate a high-temperature and high-pressure gas refrigerant. Becomes This gas refrigerant is discharged from the high-stage discharge port 21 to the high-pressure discharge pipe 27.

  Further, the intermediate-pressure gas refrigerant flowing into the suction port 64 is compressed by the rotary compression element 63 to become a high-temperature and high-pressure gas refrigerant. The gas refrigerant is discharged from the discharge port 65 to the high-pressure discharge pipe 27, and mixes with the gas refrigerant from the high-stage discharge port 21 in the high-pressure discharge pipe 27.

(2-1) Control of Electric Expansion Valve 33 The gas refrigerant flowing into the gas cooler 28 from the high-pressure discharge pipe 27 is air-cooled by the gas cooler 28, and then reaches the electric expansion valve 33 via the gas cooler outlet pipe 32. The electric expansion valve 33 is provided for controlling the high pressure HP of the refrigerant circuit 1 upstream of the electric expansion valve 33 to a predetermined target value THP. Controls the valve opening.

(2-1-1) Setting of the degree of opening of the electric expansion valve 33 at the time of operation start At the time of operation start, first, the control device 57 sets the degree of opening of the electric expansion valve 33 at the time of starting the refrigeration apparatus R (starting) based on the outside air temperature. The valve opening at the time). Specifically, in the present embodiment, the control device 57 stores in advance a data table indicating a relationship between the outside air temperature at the time of starting and the valve opening degree of the electric expansion valve 33 at the time of starting, and stores the outside air temperature at the time of starting. Based on the temperature, the opening degree of the electric expansion valve 33 at the time of starting is set with reference to the data table.

  The outside air temperature is detected by, for example, an outside air temperature sensor (not shown). The outside air temperature sensor is arranged inside or near the outdoor unit in which the intercooler 24, the gas cooler 28, the gas cooler 31 and the like are stored. Instead, the controller 57 may detect the outside air temperature from the high-pressure side pressure HP detected by the high-pressure sensor 49 (the same applies hereinafter). Since there is a correlation between the high pressure side pressure HP detected by the high pressure sensor 49 and the outside air temperature, the control device 57 can determine the outside air temperature from the high pressure side pressure HP. Specifically, the control device 57 stores in advance a data table indicating a relationship between the high pressure side pressure HP (outside air temperature) at the time of starting and the valve opening degree of the electric expansion valve 33 at the time of starting. The outside air temperature is estimated, and the opening degree of the electric expansion valve 33 at the time of starting is set with reference to the data table.

(2-1-2) Setting of the degree of opening of the electric expansion valve 33 during operation During operation, the control device 57 uses the detection pressure of the high pressure sensor 49 (high pressure side pressure HP) as an index indicating the outside air temperature. The opening of the electric expansion valve 33 is set. In this case, the control device 57 sets the opening degree of the electric expansion valve 33 so as to increase when the high-pressure side pressure HP (outside air temperature) is low. As a result, the pressure drop in the electric expansion valve 33 can be minimized, and a pressure difference from the intermediate pressure (MP) of the intermediate pressure suction pipe 26 entering the compressor 11 is ensured, and the refrigeration operation and the refrigeration operation are performed. It can be done efficiently.

  Here, the control device 57 stores in advance a data table indicating the relationship between the high pressure side pressure HP (outside air temperature) and the opening degree of the electric expansion valve 33, and refers to the data table to open the electric expansion valve 33. The degree may be set, or the opening may be calculated from a calculation formula.

(2-1-3) Control of the High Pressure Side Pressure HP at the Upper Limit MHP During the control as described above, the high pressure side pressure upstream of the electric expansion valve 33 due to the installation environment and load. When the HP has increased to the predetermined upper limit MHP, the control device 57 further increases the valve opening of the electric expansion valve 33. Since the high-pressure side pressure HP tends to decrease due to the increase in the valve opening, the high-pressure side pressure HP can always be maintained at the upper limit value MHP or less. This makes it possible to reliably suppress the abnormal rise of the high-pressure side pressure HP upstream of the electric expansion valve 33 and reliably protect the compressor 11, and to forcibly stop (protect) the compressor 11 due to abnormal high pressure. Operation) can be avoided beforehand.

  Here, when the supercritical refrigerant gas flows out of the gas cooler 28, the refrigerant gas is squeezed and expanded by the electric expansion valve 33 and liquefied, flows into the tank 36 from above through the tank inlet pipe 34, and Some evaporate. The tank 36 serves to temporarily store and separate the liquid / gas refrigerant that has exited the electric expansion valve 33, and serves as a high-pressure side pressure of the refrigeration apparatus R (in this case, the compressor 11 which is upstream from the tank 36 and upstream of the tank 36). (The region up to the high-pressure discharge pipe 27) and serves to absorb fluctuations in the refrigerant circulation amount.

  The liquid refrigerant accumulated in the lower portion of the tank 36 flows out of the tank 36 to a tank outlet pipe 37 (main circuit 38). Hereinafter, the flow of the refrigerant in the main circuit 38 will be described.

  The liquid refrigerant flowing out of the tank 36 flows into the second flow path 29B of the split heat exchanger 29, and is cooled (supercooled) in the second flow path 29B by the refrigerant flowing through the first flow path 29A.

  Thereafter, the liquid refrigerant splits at the outlet of the second flow path 29B. One of the divided refrigerant flows out of the refrigerator unit 3 and flows into the electric expansion valve 39 from the refrigerant pipe 8, and the other flows into the liquid pipe 46. The liquid refrigerant that has flowed into the liquid pipe 46 is throttled by the electric expansion valve 47, then flows into the intermediate pressure return pipe 44, merges with the gas refrigerant that has passed through the electric expansion valve 43, and flows into the first flow path 29A. . In the first flow path 29A, the liquid refrigerant evaporates. The heat absorption at this time increases the supercooling of the liquid refrigerant flowing through the second flow path 29B.

  As described above, in the split heat exchanger 29, heat exchange between the liquid refrigerant flowing out of the tank 36 and the refrigerant in which the liquid refrigerant throttled by the electric expansion valve 47 and the gas refrigerant throttled by the electric expansion valve 43 are mixed. Is performed. When the electric expansion valve 47 is connected to the downstream side of the second flow path 29B of the split heat exchanger 29 via the liquid pipe 46, the electric expansion valve 47 is connected to the downstream side of the tank 36 more than when the electric expansion valve 47 is connected to the downstream side of the tank 36. The specific enthalpy at the outlet of the refrigerator unit 3 is reduced. When the specific enthalpy decreases, the flow rate of the refrigerant decreases, so that the intermediate pressure can be reduced.

  The refrigerant that has flowed into the electric expansion valve 39 is throttled and expanded by the electric expansion valve 39 to further increase the liquid component, flow into the evaporator 41, and evaporate. The cooling effect is exhibited by the endothermic effect by this. The control device 57 controls the opening degree of the electric expansion valve 39 based on the output of a temperature sensor (not shown) for detecting the temperatures of the inlet side and the outlet side of the evaporator 41 to control the degree of superheat of the refrigerant in the evaporator 41. Is adjusted to an appropriate value.

  The low-temperature gas refrigerant flowing out of the evaporator 41 returns from the refrigerant pipe 9 to the refrigerator unit 3, passes through the refrigerant introduction pipe 22, and communicates with the first rotary compression element 14 of the compressor 11. Sucked into. The above is the flow of the refrigerant in the main circuit 38.

(2-2) Control of Electric Expansion Valve 43 The flow of the refrigerant in the auxiliary circuit 48 will be described. The temperature of the gas refrigerant accumulated in the upper portion of the tank 36 is reduced by evaporation in the tank 36. This gas refrigerant flows out of the tank 36 to the gas pipe 42. As described above, the electric expansion valve 43 is connected to the gas pipe 42. After being throttled by the electric expansion valve 43, the gas refrigerant merges with the liquid refrigerant that has passed through the electric expansion valve 47, and flows into the first flow passage 29 A of the split heat exchanger 29. Then, the gas refrigerant cools the refrigerant flowing through the second flow path 29B in the first flow path 29A, and then flows into the intermediate pressure suction pipe 26 via the intermediate pressure return pipe 44. Then, the gas refrigerant flowing from the intermediate pressure return pipe 44 into the intermediate pressure suction pipe 26 is mixed with the refrigerant discharged from the intercooler 24 as described above, so that the suction port 64 of the auxiliary compressor 60 and the high-stage Each of the side suction ports 19 is sucked.

  The electric expansion valve 43 plays a role of adjusting the pressure in the tank 36 (the pressure of the refrigerant flowing into the electric expansion valve 39) to a predetermined target value SP, in addition to the function of restricting the refrigerant flowing out of the upper part of the tank 36. . The control device 57 controls the valve opening of the electric expansion valve 43 based on the output of the unit outlet sensor 53. This is because if the valve opening of the electric expansion valve 43 increases, the amount of gas refrigerant flowing out of the tank 36 increases, and the pressure in the tank 36 decreases.

  In the present embodiment, the target value SP is set to a value lower than the high pressure side pressure HP and higher than the intermediate pressure MP. Then, the control device 57 calculates the valve opening adjustment value of the electric expansion valve 39 from the difference between the pressure OP (pressure of the refrigerant flowing into the electric expansion valve 39) in the tank 36 detected by the unit outlet sensor 53 and the target value SP. (Step number) is calculated and added to the valve opening at the time of starting described later to control the pressure OP in the tank 36 to the target value SP. That is, when the pressure OP in the tank 36 rises above the target value SP, the valve opening of the electric expansion valve 43 is increased to allow the gas refrigerant to flow out of the tank 36 into the gas pipe 42, and conversely, the target value SP When it falls further, the valve opening degree is reduced to control in the closing direction.

(2-2-1) Setting of the degree of opening of the electric expansion valve 43 when the operation is started The controller 57 sets the outside air temperature or the detection pressure (high pressure side pressure HP) of the high pressure sensor 49 which is an index indicating the outside air temperature. Based on this, the valve opening of the electric expansion valve 43 at the time of starting the refrigeration apparatus R (valve opening at the time of starting) is set. In the case of the present embodiment, the control device 57 previously stores a data table indicating the relationship between the outside air temperature at the time of starting or the high pressure side pressure HP (outside air temperature) and the valve opening degree of the electric expansion valve 43 at the time of starting. I have.

  Then, the control device 57 increases from the outside air temperature at start-up or the detected pressure (high pressure side pressure HP) as the high pressure side pressure HP (outside air temperature) increases based on the data table, and conversely, increases the high pressure side pressure. The opening degree of the electric expansion valve 43 at the time of starting is set so as to decrease as the HP decreases. As a result, it is possible to suppress an increase in the pressure in the tank 36 at the time of starting in an environment where the outside air temperature is high, and to prevent an increase in pressure of the refrigerant flowing into the electric expansion valve 39.

  In this embodiment, the control is performed with the target value SP of the pressure OP in the tank 36 fixed. However, similarly to the case of the electric expansion valve 33, the outside air temperature or the high pressure sensor 49 which is an index indicating the outside air temperature is used. The target value SP may be set based on the detected pressure (high pressure HP). In this case, the control device 57 increases as the outside air temperature or the high-pressure side pressure HP increases. Therefore, in an environment where the outside air temperature is high, the target value SP during the operation of the pressure of the refrigerant flowing into the electric expansion valve 39 increases.

  That is, in a situation where the pressure becomes high under the influence of the high outside air temperature, the intermediate pressure MP becomes high. Therefore, even if the valve opening of the electric expansion valve 43 becomes large, it is possible to prevent the disadvantage that the refrigerant does not easily flow through the auxiliary circuit 48. Will be able to Conversely, by reducing the valve opening of the electric expansion valve 43, the amount of refrigerant flowing into the auxiliary circuit 48 can be reduced, and the disadvantage that the pressure of the refrigerant at the unit outlet 6 decreases can be prevented. Accordingly, regardless of the change in the outside air temperature due to the change of the season, the valve opening of the electric expansion valve 43 can be appropriately controlled, and the change in the pressure of the refrigerant at the unit outlet 6 can be suppressed. Can be adjusted.

(2-2-2) Control at the specified value MOP of the tank pressure OP When the control is performed as described above, the tank pressure OP (the electric expansion valve 39 is When the pressure of the flowing refrigerant has increased to the predetermined specified value MOP, the control device 57 increases the valve opening of the electric expansion valve 43 by a predetermined step. Due to the increase in the valve opening, the pressure OP in the tank 36 tends to decrease, so that the pressure OP can always be maintained at the specified value MOP or less, and the influence of the high-pressure side pressure fluctuation is suppressed, and the electric expansion is prevented. The effect of suppressing the pressure of the refrigerant conveyed to the valve 39 can be reliably achieved.

(2-3) Control of Electric Expansion Valve 47 The flow of the refrigerant in the auxiliary circuit 48 will be described. The liquid refrigerant accumulated in the lower part in the tank 36 flows from the tank 36 to the tank outlet pipe 37, and after passing through the second flow path 29B, is branched. One of the divided liquid refrigerant flows into the liquid pipe 46 and is throttled by the electric expansion valve 47. Thereafter, the liquid refrigerant flows into the intermediate pressure return pipe 44, merges with the gas refrigerant from the electric expansion valve 43, flows into the first flow path 29A of the split heat exchanger 29, and evaporates there. The heat absorption at this time increases the supercooling of the liquid refrigerant flowing through the second flow path 29B.

  Thereafter, the gas refrigerant flowing out of the first flow path 29A flows into the intermediate pressure suction pipe 26 and mixes with the refrigerant flowing out of the intercooler 24, and is mixed with the suction port 64 of the auxiliary compressor 60 and the high stage of the compressor 11 Each of the side suction ports 19 is sucked.

  The control device 57 controls the valve opening of the electric expansion valve 47 to adjust the amount of liquid refrigerant flowing through the first flow path 29A of the split heat exchanger 29. For example, the control device 57 controls the valve opening of the electric expansion valve 47 based on the temperature (discharge temperature) of the refrigerant discharged from the compressor 11 to the gas cooler 29 detected by the discharge temperature sensor 50. Thereby, the amount of the liquid refrigerant flowing through the first flow path 29A of the split heat exchanger 29 is adjusted, and the discharge temperature of the refrigerant discharged from the compressor 11 to the gas cooler 28 is controlled to a predetermined target value TDT. That is, when the actual discharge temperature is higher than the target value TDT, the valve opening degree of the electric expansion valve 47 is increased, and when it is lower, it is decreased. Thus, the discharge temperature of the refrigerant of the compressor 11 is maintained at the target value TDT, and the compressor 11 is protected.

(2-4) Effect of Refrigeration Unit R Next, effects obtained by the refrigeration unit R will be described with reference to FIGS.

  FIG. 2 is a PH diagram showing an operation state of a refrigerating apparatus without an auxiliary compressor (for example, a refrigerating apparatus in which the auxiliary compressor 60 is removed from the configuration of FIG. 1) in a high-temperature environment. On the other hand, FIG. 3 is a PH diagram showing an operation state of the refrigeration apparatus R in an environment in a high temperature period. The environment in the high-temperature period is, for example, an environment in which the outside air temperature is about 32 degrees Celsius (for example, summer).

  2 and 3, a line from X1 to X2, a line from X3 to X4, a line from X5 to X6, and a line from X7 to X8 are respectively an electric expansion valve 33, an electric expansion valve 39, The pressure reduction by the electric expansion valve 43 and the electric expansion valve 47 is shown.

  2 and 3, X9 indicates the specific enthalpy / pressure at the time when the refrigerant having passed through the electric expansion valve 43 and the refrigerant having passed through the electric expansion valve 47 are mixed. X10 indicates the specific enthalpy / pressure when the mixed refrigerant passes through the first flow path 29A of the split heat exchanger 29. X11 indicates the specific enthalpy / pressure when the refrigerant flowing through the intermediate pressure suction pipe 26 flows into each of the high-stage suction port 19 of the compressor 11 and the suction port 64 of the auxiliary compressor 60.

  As is clear from the comparison between FIG. 2 and FIG. 3, in the refrigeration apparatus R, the intermediate pressure (MP) can be lower than in the refrigeration apparatus without the auxiliary compressor 60.

  As described above, in the two-stage compressor in which the first rotary compression element and the second rotary compression element are driven by the same rotary shaft, the excluded volume ratio between the low-stage side and the high-stage side is determined. The intermediate pressure is determined according to the excluded volume ratio. Therefore, it has not been possible to reduce the intermediate pressure by increasing the suction amount (exclusion volume) of the refrigerant only on the high stage side.

  In contrast, the refrigeration apparatus R of the present embodiment includes the auxiliary compressor 60 provided in parallel with the compressor 11 which is a two-stage compressor, thereby reducing the refrigerant suction amount (excluded volume) in the intermediate pressure section. We are increasing. Thereby, even if the excluded volume ratio in the compressor 11 is determined, the intermediate pressure can be reduced.

  Then, as is clear from the comparison between FIG. 2 and FIG. 3, the pressure OP in the tank 36 (the pressure at the time of X3) can be reduced by reducing the intermediate pressure. As a result, the specific enthalpy at the outlet of the tank 36 can be reduced, and the refrigerating capacity can be secured. Further, it is possible to prevent the pressure OP in the tank 36 from exceeding the critical pressure CP in an environment in a high temperature period, and to perform gas-liquid separation. In addition, protection control (for example, medium pressure cut, step-out, etc.) for forcibly stopping the compressor 11 at a predetermined high pressure value (abnormal high pressure) can be avoided, and stable operation of the refrigeration apparatus R can be realized.

  In the refrigerating apparatus R of the present embodiment, since the pressure of the refrigerant sent to the showcase 4 is reduced, the design pressure of the piping can be reduced, and a thin-walled pipe can be used.

  Further, in the refrigeration apparatus R of the present embodiment, the liquid refrigerant is held in the tank 36 and the amount thereof can be continuously changed, so that the amount of the refrigerant circulating in the refrigeration circuit 1 can be stably maintained at an appropriate amount.

  In the present embodiment, the configuration of the refrigeration apparatus R illustrated in FIG. 1 has been described, but the configuration of the refrigeration apparatus R is not limited to the configuration illustrated in FIG. Hereinafter, another configuration example of the refrigeration apparatus R will be described.

(3) Another configuration example 1 of the refrigeration apparatus R
FIG. 4 is a refrigerant circuit diagram of a refrigeration apparatus R having a configuration different from that of FIG. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted below.

  The refrigeration apparatus R shown in FIG. 4 includes a bypass circuit 70 and a solenoid valve 71 in addition to the configuration shown in FIG. One end of the bypass circuit 70 is connected to the refrigerant introduction pipe 22, and the other end of the bypass circuit 70 is connected to the suction port 64 of the auxiliary compressor 60.

  In the middle of the bypass circuit 70, an electromagnetic valve 71 is provided. The opening and closing of the solenoid valve 71 is controlled by the control device 57. For example, the control device 57 stores in advance a data table indicating the relationship between the outside air temperature (high-pressure side pressure HP) and the opening and closing of the solenoid valve 71, estimates the outside air temperature, and refers to the data table to determine the electromagnetic field. The opening and closing of the valve 71 is set. Note that a check valve may be provided instead of the electromagnetic valve 71.

  For example, when the outside air temperature is about 32 degrees Celsius (high-temperature environment, for example, in summer), the control device 57 closes the solenoid valve 71 and drives the compressor 11 and the auxiliary compressor 60. As a result, the refrigerant circulates as described in “(2) Operation of refrigeration apparatus R”.

  On the other hand, for example, when the outside air temperature is equal to or less than 20 degrees Celsius (low-temperature environment; for example, winter), the control device 57 opens the solenoid valve 71, does not drive the compressor 11, and operates the auxiliary compressor. 60 is driven. Further, the control device 57 maximizes the valve opening degree of the electric expansion valve 33 and closes the electric expansion valve 43 and the electric expansion valve 47.

  Thus, the refrigerant that has exited the evaporator 41 flows into the bypass circuit 70 and is sucked into the suction port 64 of the auxiliary compressor 60. The refrigerant compressed by the auxiliary compressor 60 is discharged from the discharge port 65 to the high-pressure discharge pipe 27. Thereafter, the refrigerant flows in the order of the gas cooler 28, the electric expansion valve 33, the tank 36, the tank outlet pipe 37, the second flow path 29B of the split heat exchanger 29, the electric expansion valve 39, and the evaporator 41, and again the bypass circuit 70 Flows into.

  FIG. 5 shows a PH diagram when the refrigerant flows through the bypass circuit 70. 5 are the same as those in FIGS. 2 and 3. As shown in FIG. 5, the compression of the refrigerant is performed in only one stage by the auxiliary compressor 60.

  As described above, according to this configuration example, in an environment in which the cooling load is reduced (low temperature period), only the auxiliary compressor 60 is used without using the compressor 11 which is a two-stage compressor. Energy consumption can be reduced.

(4) Another configuration example 2 of the refrigeration apparatus R
FIG. 6 is a refrigerant circuit diagram of a refrigeration apparatus R having a configuration different from that of FIG. FIG. 6 is a simplified version of FIG. 1, and the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted below.

  The refrigeration apparatus R illustrated in FIG. 6 includes a compressor 11a in addition to the configuration illustrated in FIG. The compressor 11a is a two-stage compressor provided in parallel with the compressor 11, and has the same configuration as the compressor 11.

  In the refrigerating apparatus R shown in FIG. 6, the refrigerant from the evaporator 41 is sucked into each of the compressor 11 and the compressor 11a. The refrigerant in which the refrigerant from the intercooler 24 and the refrigerant from the intermediate pressure return pipe 44 are mixed is sucked into each of the compressor 11, the compressor 11a, and the auxiliary compressor 60.

  In FIG. 6, the electric expansion valve 39, the showcase 4, and the evaporator 41 are provided one by one. However, the electric expansion valve 39, the showcase 4, and the evaporator 41 are each provided in plural. It may be. For example, one electric expansion valve 39, one showcase 4, and one evaporator 41 are set as one set, and the set is provided in parallel.

(5) Another configuration example 3 of the refrigeration apparatus R
Although the configuration shown in FIGS. 1, 4, and 6 is such that only one auxiliary compressor 60 is provided, a plurality of auxiliary compressors 60 may be provided. The plurality of auxiliary compressors 60 are provided in parallel with each other, and are provided in parallel with one or more compressors 11 (compressors 11a). The refrigerant in which the refrigerant from the intercooler 24 and the refrigerant from the intermediate pressure return pipe 44 are mixed is sucked into each of the plurality of auxiliary compressors 60.

  As described above, in the present embodiment, the compressor 11 includes the compressor (compression means) 11 having the first rotary compression element 14 and the second rotary compression element 16 driven by the same rotation shaft. The refrigerant circuit 1 is constituted by the gas cooler 28, the electric expansion valve (main throttle means) 39, and the evaporator 41, and an auxiliary compressor provided in parallel with the compressor 11 in the refrigeration apparatus R using carbon dioxide refrigerant. (Auxiliary compression means) 60 and an electric expansion valve (pressure adjustment) connected to the refrigerant circuit 1 downstream of the gas cooler 28 and upstream of the electric expansion valve 39 for adjusting the pressure of the refrigerant flowing out of the gas cooler 28. Throttling means) 33, a tank 36 connected to the refrigerant circuit 1 downstream of the electric expansion valve 33 and upstream of the electric expansion valve 39, and a tank downstream of the tank 36 and connected to the electric expansion valve 39. Upstream refrigerant The split heat exchanger 29 provided in the path 1 and having the first flow path 29A and the second flow path 29B, and the pressure of the refrigerant flowing out of the gas pipe 42 provided at the first height of the tank 36 It flows out of the electric expansion valve (first auxiliary throttle means) 43 to be adjusted and the liquid pipe 46 provided at a position lower than the first height, and has passed through the second flow path 29B of the split heat exchanger 29. Thereafter, an electric expansion valve (second auxiliary throttle means) 47 for adjusting the pressure of one of the refrigerants diverted on the downstream side of the second flow path 29B, and a refrigerant whose pressure is adjusted by the electric expansion valve 43 Auxiliary circuit for allowing the refrigerant mixed with the refrigerant whose pressure has been adjusted by the electric expansion valve 47 to flow through the split heat exchanger 29 to the first flow path 29A, and then to be drawn into the intermediate pressure section of the compressor 11 and the auxiliary compressor 60. 48 and the cold flowing out of the tank 36 Flows through the split heat exchanger 29, the second flow path 29B, and exchanges heat with the refrigerant flowing through the first flow path 29A. Then, the other of the refrigerant divided at the downstream side of the second flow path 29B is electrically driven. A control device (control) that controls the operation of the main circuit 38 flowing into the expansion valve 39, the compressor 11, the auxiliary compressor 60, the electric expansion valve 39, the electric expansion valve 33, the electric expansion valve 43, and the electric expansion valve 47. (Means) 57.

  Thereby, when using the carbon dioxide refrigerant, it is possible to increase the suction amount (excluded volume) of the refrigerant in the intermediate pressure section, and to reduce the intermediate pressure even if the excluded volume ratio in the compressor 11 is determined. Can be. As a result, the specific enthalpy at the outlet of the tank 36 can be reduced, and the refrigerating capacity can be secured.

  The refrigerating apparatus R further includes a bypass circuit 70 that connects the auxiliary compressor 60 and the refrigerant introduction pipe 22 provided on the downstream side of the evaporator 41 and on the upstream side of the compressor 11. , A check valve, or an electromagnetic valve 71 whose opening and closing are controlled by the control device 57.

  Thereby, in an environment where the cooling load is reduced (low temperature period), energy consumption can be reduced.

  In the refrigerating apparatus R, the rotation speed of the auxiliary compressor 60 is variable.

  The refrigerating apparatus R includes a plurality of auxiliary compressors 60 provided in parallel with each other. The plurality of auxiliary compressors 60 have split heat generated after the pressures are adjusted by the electric expansion valves 43 and 47. The refrigerant flowing through the first flow path 29A of the exchanger 29 is sucked.

  Further, the refrigeration apparatus R includes a plurality of compressors 11 and 11a provided in parallel with each other. After that, the refrigerant flowing through the first flow path 29A of the split heat exchanger 29 is sucked.

  The first embodiment of the present invention has been described above.

<Embodiment 2>
Next, a second embodiment of the present invention will be described.

(1) Configuration of Refrigeration Device R FIG. 7 is a refrigerant circuit diagram of the refrigeration device R according to one embodiment to which the present invention is applied. The refrigeration apparatus R according to the present embodiment includes a refrigerator unit 3 installed in a machine room of a store such as a supermarket and a show of one or a plurality of units (only one is shown in the drawing) installed in a store of the store. The refrigerator unit 3 and the showcase 4 are connected by a refrigerant pipe (liquid pipe) 8 and a refrigerant pipe 9 via a unit outlet 6 and a unit inlet 7 to form a predetermined refrigerant circuit 1. Make up.

  The refrigerant circuit 1 uses carbon dioxide (R744), whose refrigerant pressure on the high pressure side can be equal to or higher than the critical pressure (supercritical), as the refrigerant. This carbon dioxide refrigerant is a natural refrigerant that is friendly to the global environment and takes flammability and toxicity into consideration. As the oil as the lubricating oil, for example, existing oils such as mineral oil (mineral oil), alkylbenzene oil, ether oil, ester oil, and PAG (polyalkyl glycol) are used. Each arrow shown in FIG. 7 indicates the flow of the carbon dioxide refrigerant.

  The refrigerator unit 3 includes a compressor 11 (an example of a compression unit). The compressor 11 is, for example, an internal intermediate pressure type two-stage compression type rotary compressor. The compressor 11 includes a closed container 12 and a rotary compression mechanism. The rotary compression mechanism section includes an electric element 13 as a drive element housed in an upper part of the internal space of the sealed container 12, and a first (low-stage side) rotary compression element ( A first compression element) 14 and a second (high-stage side) rotary compression element (second compression element) 16 are provided. The compressor 11 is a two-stage compressor having a first rotary compression element 14 and a second rotary compression element 16 driven by the same rotary shaft (the rotary shaft of the electric element 13). In such a two-stage compressor, the excluded volume ratio between the low stage and the high stage is determined, and the intermediate pressure (MP) is determined according to the excluded volume ratio.

  The first rotary compression element 14 of the compressor 11 compresses the low-pressure refrigerant sucked into the compressor 11 from the low-pressure side of the refrigerant circuit 1 through the refrigerant pipe 9, and increases the pressure to an intermediate pressure and discharges it. The second rotary compression element 16 sucks in the intermediate-pressure refrigerant discharged by the first rotary compression element 14, compresses the intermediate-pressure refrigerant to a high pressure, and discharges the refrigerant to the high-pressure side of the refrigerant circuit 1. The compressor 11 is a variable frequency compressor. The control device 57, which will be described later, controls the rotation speed of the first rotary compression element 14 and the second rotary compression element 16 by changing the operation frequency of the electric element 13.

  A low-stage suction port 17 communicating with the first rotary compression element 14, a low-stage discharge port 18 communicating with the interior of the closed vessel 12, and a second rotary compression element 16 are provided on a side surface of the closed container 12 of the compressor 11. A high-stage suction port 19 and a high-stage discharge port 21 are formed. One end of a refrigerant introduction pipe 22 is connected to the low-stage suction port 17 of the compressor 11, and the other end is connected to the refrigerant pipe 9 at the unit inlet 7.

  The low-pressure refrigerant gas sucked into the low-pressure portion of the first rotary compression element 14 from the low-stage suction port 17 is subjected to the first-stage compression by the first rotary compression element 14 and is increased to an intermediate pressure. Is discharged into the closed container 12. Thereby, the inside of the sealed container 12 has an intermediate pressure (MP).

  One end of an intermediate-pressure discharge pipe 23 is connected to the low-stage discharge port 18 of the compressor 11 from which the intermediate-pressure refrigerant gas is discharged in the sealed container 12, and the other end is connected to an inlet of the intercooler 24. Have been. The intercooler 24 air-cools the intermediate-pressure refrigerant discharged from the first rotary compression element 14. One end of an intermediate pressure suction pipe 26 is connected to an outlet of the intercooler 24. The other end of the intermediate pressure suction pipe 26 is branched and connected to the high-stage suction port 19 of the compressor 11 and the suction port 64 of the auxiliary compressor 60.

  The refrigerator unit 3 includes an auxiliary compressor 60 (an example of an auxiliary compression unit) provided in parallel with the compressor 11. The auxiliary compressor 60 compresses the intermediate-pressure refrigerant flowing from the intermediate-pressure suction pipe 26.

  The auxiliary compressor 60 includes an airtight container 61, an electric element 62 as a driving element housed in the internal space of the airtight container 61, and a rotary compression element 63 driven by a rotating shaft of the electric element 62. I have.

  The rotary compression element 63 compresses the intermediate-pressure refrigerant sucked from the intermediate-pressure suction pipe 26, raises the pressure to a high pressure, and discharges the refrigerant to the high-pressure side of the refrigerant circuit 1. The auxiliary compressor 60 is a variable frequency compressor. The control device 57, which will be described later, controls the rotation speed of the rotary compression element 62 by changing the operation frequency of the electric element 62.

  Further, in driving the rotary compression element 63, in addition to the power of the electric element 62, expansion energy recovered by an expander 72 described later is used.

  A suction port 64 and a discharge port 65 communicating with the rotary compression element 63 are formed on the side surface of the closed container 61. One end of the intermediate pressure suction pipe 26 is connected to the suction port 64. The discharge port 65 of the auxiliary compressor 60 is connected to the high-pressure discharge pipe 27 via a pipe.

  The intermediate-pressure (MP) refrigerant gas sucked into the second rotary compression element 16 from the high-stage suction port 19 of the compressor 11 is compressed by the second rotary compression element 16 in the second stage. It becomes high temperature and high pressure refrigerant gas.

  The intermediate-pressure (MP) refrigerant gas sucked into the rotary compression element 63 from the suction port 64 of the auxiliary compressor 60 is compressed by the rotary compression element 63 to become a high-temperature and high-pressure refrigerant gas.

  In addition, one end of a high-pressure discharge pipe 27 is connected to a high-stage discharge port 21 provided on the high-pressure chamber side of the second rotary compression element 16 of the compressor 11, and the other end of a gas cooler (radiator) 28 is connected. Connected to the entrance. Although not shown, an oil separator 20 may be provided in the middle of the high-pressure discharge pipe 27. The oil separated from the refrigerant by the oil separator is returned into the closed container 12 of the compressor 11 and the closed container 61 of the auxiliary compressor 60.

  The gas cooler 28 cools the high-pressure discharge refrigerant discharged from the compressor 11. In the vicinity of the gas cooler 28, a gas cooler blower 31 for air-cooling the gas cooler 28 is provided. In the present embodiment, the gas cooler 28 is arranged in parallel with the above-described intercooler 24, and these are arranged in the same air passage.

  One end of a gas cooler outlet pipe 32 is connected to an outlet of the gas cooler 28, and the other end of the gas cooler outlet pipe 32 is connected to an inlet of an electric expansion valve 33 (an example of a pressure adjusting throttle unit). The electric expansion valve 33 throttles and expands the refrigerant discharged from the gas cooler 28 and adjusts the high pressure side pressure of the refrigerant circuit 1 on the upstream side from the electric expansion valve 33. The outlet of the electric expansion valve 33 is connected to the upper part of the tank 36 via the tank inlet pipe 34.

  The refrigerator unit 3 includes an expander 72 (an example of an expansion unit) provided in parallel with the electric expansion valve 33.

  The expander 72 expands the refrigerant flowing out of the gas cooler 28. One end of a pipe 68 is connected to the inlet (suction port) of the expander 72, and the other end of the pipe 68 is connected to the gas cooler outlet pipe 32. Thereby, the refrigerant flowing out of the gas cooler 28 is divided and flows into each of the electric expansion valve 33 and the expander 72. One end of a pipe 69 is connected to an outlet (discharge port) of the expander 72, and the other end of the pipe 69 is connected to the tank inlet pipe 34. Thereby, the refrigerant flowing out of the expander 72 flows into the gas pipe 42 and mixes with the refrigerant discharged from the electric expansion valve 33.

  Further, the expander 72 recovers expansion energy when the refrigerant changes from high pressure to low pressure. As described above, the recovered expansion energy is used to drive the rotary compression element 63 of the auxiliary compressor 60.

  Although the compressor 11 and the expander 72 are illustrated as being separated from each other as an example in FIG. 7, the compressor 11 and the expander 72 may be arranged side by side and their rotating shafts may be connected. In this case, the expansion energy recovered by the expander 72 is transmitted to the auxiliary compressor 60 via the connected rotary shaft, and is used for driving the rotary compression element 63.

  The tank 36 is a volume body having a space of a predetermined volume inside thereof, and one end of a tank outlet pipe 37 is connected to a lower portion thereof. It is connected. In the middle of the tank outlet pipe 37, a second flow path 29B of the split heat exchanger 29 is provided. This tank outlet pipe 37 constitutes a main circuit 38 in the present embodiment.

  On the other hand, the showcase 4 installed in the store is connected to refrigerant pipes 8 and 9. The showcase 4 is provided with an electric expansion valve 39 (an example of a main throttle unit) and an evaporator 41, which are sequentially connected between the refrigerant pipe 8 and the refrigerant pipe 9 (the electric expansion valve 39 is connected to the refrigerant pipe 9). The refrigerant pipe 8 side and the evaporator 41 are the refrigerant pipe 9 side). Next to the evaporator 41, a cool air circulation blower (not shown) for blowing air to the evaporator 41 is provided. The refrigerant pipe 9 is connected to the low-stage suction port 17 that communicates with the first rotary compression element 14 of the compressor 11 via the refrigerant introduction pipe 22 as described above.

  On the other hand, one end of a gas pipe 42 is connected to an upper part of the tank 36, and the other end of the gas pipe 42 is connected to an inlet of an electric expansion valve 43 (an example of a first auxiliary circuit throttle unit). . The gas pipe 42 allows the gas refrigerant to flow out of the upper portion of the tank 36 and flow into the electric expansion valve 43.

  One end of an intermediate pressure return pipe 44 is connected to the outlet of the electric expansion valve 43, and the other end of the intermediate pressure return pipe 44 communicates with the middle pressure suction pipe 26 connected to the intermediate pressure section of the compressor 11. Have been. In the middle of the intermediate pressure return pipe 44, a first flow path 29A of the split heat exchanger 29 is provided.

  Further, on the downstream side of the second flow path 29B of the split heat exchanger 29, one end of the liquid pipe 46 is connected to the tank outlet pipe 37 downstream of the split heat exchanger 29. The other end of the liquid pipe 46 is connected to the intermediate pressure return pipe 44 on the upstream side of the split heat exchanger 29 and on the downstream side of the electric expansion valve 43. An electric expansion valve 47 (an example of a second auxiliary circuit throttle unit) is provided in the middle of the liquid pipe 46.

  The above-described electric expansion valve 43 (first auxiliary circuit throttle unit) and the electric expansion valve 47 (second auxiliary circuit throttle unit) constitute auxiliary throttle units in the present embodiment. Further, the intermediate pressure return pipe 44, the electric expansion valve 43, the electric expansion valve 47, the gas pipe 42, and the liquid pipe 46 constitute an auxiliary circuit 48 in the present embodiment.

  Thus, the electric expansion valve 33 is located downstream of the gas cooler 28 and upstream of the electric expansion valve 39. The tank 36 is located downstream of the electric expansion valve 33 and upstream of the electric expansion valve 39. Further, the split heat exchanger 29 is located downstream of the tank 36 and upstream of the electric expansion valve 39. Thereby, the refrigerant circuit 1 of the refrigeration apparatus R in the present embodiment is configured.

  Various sensors are attached to various parts of the refrigerant circuit 1.

  For example, a high-pressure sensor 49 is attached to the high-pressure discharge pipe 27. The high-pressure sensor 49 detects the high-pressure side pressure HP of the refrigerant circuit 1 (the pressure between the high-stage discharge port 21 of the compressor 11 and the inlet of the electric expansion valve 33).

  Further, for example, a low pressure sensor 51 is attached to the refrigerant introduction pipe 22. The low-pressure sensor 51 detects the low-pressure side pressure LP of the refrigerant circuit 1 (the pressure between the outlet of the electric expansion valve 39 and the low-stage suction port 17).

  Further, for example, an intermediate pressure sensor 52 is attached to the intermediate pressure return pipe 44. The intermediate pressure sensor 52 detects the intermediate pressure MP (the pressure in the intermediate pressure return pipe 44 downstream of the outlets of the electric expansion valves 43 and 47, which is the pressure in the intermediate pressure region of the refrigerant circuit 1, and the low pressure of the compressor 11). (Pressure equal to the pressure between the stage side discharge port 18 and the high stage side suction port 19).

  Further, for example, a unit outlet sensor 53 is attached to the tank outlet pipe 37 downstream of the split heat exchanger 29. The unit outlet sensor 53 detects the pressure OP in the tank 36. The pressure in the tank 36 is the pressure of the refrigerant flowing out of the refrigerator unit 3 and flowing into the electric expansion valve 39 from the refrigerant pipe 8.

  Each of the above-described sensors is connected to an input of a control device 57 (an example of a control unit) of the refrigerator unit 3 including a microcomputer. On the other hand, the output of the control device 57 includes the electric element 13 of the compressor 11, the electric element 62 of the auxiliary compressor 60, the gas cooler blower 31, the electric expansion valve 33, the electric expansion valve 43, the electric expansion valve 47, and the electric expansion valve. 39 is connected. The control device 57 controls each component on the output side based on a detection result from each sensor, setting data, and the like.

  In the following, the electric expansion valve 39 on the showcase 4 side and the above-described blower for circulating cold air will be described as being controlled by the control device 57. These are controlled by a main control device (not shown) of the store. It may be controlled by a control device (not shown) on the side of the showcase 4 that operates in cooperation with 57. Therefore, the control means in the present embodiment may be a concept including the control device 57, the control device on the showcase 4 side, the main control device described above, and the like.

(2) Operation of Refrigeration Device R Next, the operation of the refrigeration device R will be described. When the electric element 13 of the compressor 11 is driven by the control device 57, the first rotary compression element 14 and the second rotary compression element 16 rotate, and the first rotary compression element 14 A low-pressure refrigerant gas (carbon dioxide) is sucked into the low-pressure section of the air conditioner. Then, the pressure is increased to an intermediate pressure by the first rotary compression element 14 and discharged into the closed container 12. Thereby, the inside of the sealed container 12 has an intermediate pressure (MP).

  When the electric element 62 of the auxiliary compressor 60 is driven by the control device 57, the rotary compression element 63 rotates.

  Then, the intermediate-pressure gas refrigerant in the sealed container 12 enters the intercooler 24 from the low-stage discharge port 18 via the intermediate-pressure discharge pipe 23, and is air-cooled in the intercooler 24.

  The air-cooled gas refrigerant flows out of the intercooler 24 to the intermediate pressure suction pipe 26, where the gas refrigerant flows into the intermediate pressure suction pipe 26 from the intermediate pressure return pipe 44 (to be described in detail later). Mix. The mixed gas refrigerant splits in the intermediate pressure suction pipe 26 and flows into the high-stage suction port 19 (intermediate pressure section) of the compressor 11 and the suction port 64 of the auxiliary compressor 60, respectively.

  The intermediate-pressure gas refrigerant that has flowed into the high-stage suction port 19 is sucked into the second rotary compression element 16, and the second rotary compression element 16 performs second-stage compression to generate a high-temperature and high-pressure gas refrigerant. Becomes This gas refrigerant is discharged from the high-stage discharge port 21 to the high-pressure discharge pipe 27.

  Further, the intermediate-pressure gas refrigerant flowing into the suction port 64 is compressed by the rotary compression element 63 to become a high-temperature and high-pressure gas refrigerant. The gas refrigerant is discharged from the discharge port 65 to the high-pressure discharge pipe 27, and mixes with the gas refrigerant from the high-stage discharge port 21 in the high-pressure discharge pipe 27.

(2-1) Control of Electric Expansion Valve 33 The gas refrigerant that has flowed into the gas cooler 28 from the high-pressure discharge pipe 27 is air-cooled by the gas cooler 28, then diverted in the gas cooler outlet pipe 32, and is divided into the electric expansion valve 33 and the expander 72. Flows into. The electric expansion valve 33 is provided to control the high-pressure side pressure HP of the refrigerant circuit 1 on the upstream side of the electric expansion valve 33 to a predetermined target value THP. The valve opening is controlled.

(2-1-1) Setting of the degree of opening of the electric expansion valve 33 at the time of operation start At the time of operation start, first, the control device 57 sets the degree of opening of the electric expansion valve 33 at the time of starting the refrigeration apparatus R (starting) based on the outside air temperature. The valve opening at the time). Specifically, in the present embodiment, the control device 57 stores in advance a data table indicating a relationship between the outside air temperature at the time of starting and the valve opening degree of the electric expansion valve 33 at the time of starting, and stores the outside air temperature at the time of starting. Based on the temperature, the opening degree of the electric expansion valve 33 at the time of starting is set with reference to the data table.

  The outside air temperature is detected by, for example, an outside air temperature sensor (not shown). The outside air temperature sensor is arranged inside or near the outdoor unit in which the intercooler 24, the gas cooler 28, the gas cooler 31 and the like are stored. Instead, the controller 57 may detect the outside air temperature from the high-pressure side pressure HP detected by the high-pressure sensor 49 (the same applies hereinafter). Since there is a correlation between the high pressure side pressure HP detected by the high pressure sensor 49 and the outside air temperature, the control device 57 can determine the outside air temperature from the high pressure side pressure HP. Specifically, the control device 57 stores in advance a data table indicating a relationship between the high pressure side pressure HP (outside air temperature) at the time of starting and the valve opening degree of the electric expansion valve 33 at the time of starting. The outside air temperature is estimated, and the opening degree of the electric expansion valve 33 at the time of starting is set with reference to the data table.

(2-1-2) Setting of the degree of opening of the electric expansion valve 33 during operation During operation, the control device 57 uses the detection pressure of the high pressure sensor 49 (high pressure side pressure HP) as an index indicating the outside air temperature. The opening of the electric expansion valve 33 is set. In this case, the control device 57 sets the opening degree of the electric expansion valve 33 so as to increase when the high-pressure side pressure HP (outside air temperature) is low. As a result, the pressure drop in the electric expansion valve 33 can be minimized, and a pressure difference from the intermediate pressure (MP) of the intermediate pressure suction pipe 26 entering the compressor 11 is ensured, and the refrigeration operation and the refrigeration operation are performed. It can be done efficiently.

  Here, the control device 57 stores in advance a data table indicating the relationship between the high pressure side pressure HP (outside air temperature) and the opening degree of the electric expansion valve 33, and refers to the data table to open the electric expansion valve 33. The degree may be set, or the opening may be calculated from a calculation formula.

(2-1-3) Control of the High Pressure Side Pressure HP at the Upper Limit MHP During the control as described above, the high pressure side pressure upstream of the electric expansion valve 33 due to the installation environment and load. When the HP has increased to the predetermined upper limit MHP, the control device 57 further increases the valve opening of the electric expansion valve 33. Since the high-pressure side pressure HP tends to decrease due to the increase in the valve opening, the high-pressure side pressure HP can always be maintained at the upper limit value MHP or less. This makes it possible to reliably suppress the abnormal rise of the high-pressure side pressure HP upstream of the electric expansion valve 33 and reliably protect the compressor 11, and to forcibly stop (protect) the compressor 11 due to abnormal high pressure. Operation) can be avoided beforehand.

  Here, the supercritical refrigerant gas flowing out of the gas cooler 28 is reduced in pressure by the electric expansion valve 33 and the expander 72 to be in a gas-liquid two-phase mixed state, and flows into the tank 36 from above via the tank inlet pipe 34. I do. The tank 36 temporarily stores and separates the liquid / gas refrigerant that has flowed in from the tank inlet pipe 34, and has a role of a high-pressure side pressure of the refrigerating device R (in this case, the compressor 11 that is upstream from the tank 36 and upstream of the tank 36). (The region up to the high-pressure discharge pipe 27) and serves to absorb fluctuations in the refrigerant circulation amount.

  The liquid refrigerant accumulated in the lower portion of the tank 36 flows out of the tank 36 to a tank outlet pipe 37 (main circuit 38). Hereinafter, the flow of the refrigerant in the main circuit 38 will be described.

  The liquid refrigerant flowing out of the tank 36 flows into the second flow path 29B of the split heat exchanger 29, and is cooled (supercooled) in the second flow path 29B by the refrigerant flowing through the first flow path 29A. Thereafter, the liquid refrigerant exits the refrigerator unit 3 and flows from the refrigerant pipe 8 into the electric expansion valve 39.

  The refrigerant that has flowed into the electric expansion valve 39 is throttled and expanded by the electric expansion valve 39 to further increase the liquid component, flow into the evaporator 41, and evaporate. The cooling effect is exhibited by the endothermic effect by this. The control device 57 controls the opening degree of the electric expansion valve 39 based on the output of a temperature sensor (not shown) for detecting the temperatures of the inlet side and the outlet side of the evaporator 41 to control the degree of superheat of the refrigerant in the evaporator 41. Is adjusted to an appropriate value.

  The low-temperature gas refrigerant flowing out of the evaporator 41 returns from the refrigerant pipe 9 to the refrigerator unit 3, passes through the refrigerant introduction pipe 22, and communicates with the first rotary compression element 14 of the compressor 11. Sucked into. The above is the flow of the refrigerant in the main circuit 38.

(2-2) Control of Electric Expansion Valve 43 The flow of the refrigerant in the auxiliary circuit 48 will be described. The temperature of the gas refrigerant accumulated in the upper portion of the tank 36 is reduced by evaporation in the tank 36. This gas refrigerant flows out of the tank 36 to the gas pipe 42. As described above, the electric expansion valve 43 is connected to the gas pipe 42. After being throttled by the electric expansion valve 43, the gas refrigerant flows into the first flow path 29 </ b> A of the split heat exchanger 29. Then, the gas refrigerant cools the refrigerant flowing through the second flow path 29B in the first flow path 29A, and then flows into the intermediate pressure suction pipe 26 via the intermediate pressure return pipe 44. Then, the gas refrigerant flowing from the intermediate pressure return pipe 44 into the intermediate pressure suction pipe 26 is mixed with the refrigerant discharged from the intercooler 24 as described above, so that the suction port 64 of the auxiliary compressor 60 and the high stage of the compressor 11 Each of the side suction ports 19 is sucked.

  The electric expansion valve 43 plays a role of adjusting the pressure in the tank 36 (the pressure of the refrigerant flowing into the electric expansion valve 39) to a predetermined target value SP, in addition to the function of restricting the refrigerant flowing out of the upper part of the tank 36. . The control device 57 controls the valve opening of the electric expansion valve 43 based on the output of the unit outlet sensor 53. This is because if the valve opening of the electric expansion valve 43 increases, the amount of gas refrigerant flowing out of the tank 36 increases, and the pressure in the tank 36 decreases.

  In the present embodiment, the target value SP is set to a value lower than the high pressure side pressure HP and higher than the intermediate pressure MP. Then, the control device 57 calculates the valve opening adjustment value of the electric expansion valve 39 from the difference between the pressure OP (pressure of the refrigerant flowing into the electric expansion valve 39) in the tank 36 detected by the unit outlet sensor 53 and the target value SP. (Step number) is calculated and added to the valve opening at the time of starting described later to control the pressure OP in the tank 36 to the target value SP. That is, when the pressure OP in the tank 36 rises above the target value SP, the valve opening of the electric expansion valve 43 is increased to allow the gas refrigerant to flow out of the tank 36 into the gas pipe 42, and conversely, the target value SP When it falls further, the valve opening degree is reduced to control in the closing direction.

(2-2-1) Setting of the degree of opening of the electric expansion valve 43 when the operation is started The controller 57 sets the outside air temperature or the detection pressure (high pressure side pressure HP) of the high pressure sensor 49 which is an index indicating the outside air temperature. Based on this, the valve opening of the electric expansion valve 43 at the time of starting the refrigeration apparatus R (valve opening at the time of starting) is set. In the case of the present embodiment, the control device 57 previously stores a data table indicating the relationship between the outside air temperature at the time of starting or the high pressure side pressure HP (outside air temperature) and the valve opening degree of the electric expansion valve 43 at the time of starting. I have.

  Then, the control device 57 increases from the outside air temperature at start-up or the detected pressure (high pressure side pressure HP) as the high pressure side pressure HP (outside air temperature) increases based on the data table, and conversely, increases the high pressure side pressure. The opening degree of the electric expansion valve 43 at the time of starting is set so as to decrease as the HP decreases. As a result, it is possible to suppress an increase in the pressure in the tank 36 at the time of starting in an environment where the outside air temperature is high, and to prevent an increase in pressure of the refrigerant flowing into the electric expansion valve 39.

  In this embodiment, the control is performed with the target value SP of the pressure OP in the tank 36 fixed. However, similarly to the case of the electric expansion valve 33, the outside air temperature or the high pressure sensor 49 which is an index indicating the outside air temperature is used. The target value SP may be set based on the detected pressure (high pressure HP). In this case, the control device 57 increases as the outside air temperature or the high-pressure side pressure HP increases. Therefore, in an environment where the outside air temperature is high, the target value SP during the operation of the pressure of the refrigerant flowing into the electric expansion valve 39 increases.

  That is, in a situation where the pressure becomes high under the influence of the high outside air temperature, the intermediate pressure MP becomes high. Therefore, even if the valve opening of the electric expansion valve 43 becomes large, it is possible to prevent the disadvantage that the refrigerant does not easily flow through the auxiliary circuit 48. Will be able to Conversely, by reducing the valve opening of the electric expansion valve 43, the amount of refrigerant flowing into the auxiliary circuit 48 can be reduced, and the disadvantage that the pressure of the refrigerant at the unit outlet 6 decreases can be prevented. Accordingly, regardless of the change in the outside air temperature due to the change of the season, the valve opening of the electric expansion valve 43 can be appropriately controlled, and the change in the pressure of the refrigerant at the unit outlet 6 can be suppressed. Can be adjusted.

(2-2-2) Control at the specified value MOP of the tank pressure OP When the control is performed as described above, the tank pressure OP (the electric expansion valve 39 is When the pressure of the flowing refrigerant has increased to the predetermined specified value MOP, the control device 57 increases the valve opening of the electric expansion valve 43 by a predetermined step. Due to the increase in the valve opening, the pressure OP in the tank 36 tends to decrease, so that the pressure OP can always be maintained at the specified value MOP or less, and the influence of the high-pressure side pressure fluctuation is suppressed, and the electric expansion is prevented. The effect of suppressing the pressure of the refrigerant conveyed to the valve 39 can be reliably achieved.

(2-3) Control of Electric Expansion Valve 47 The flow of the refrigerant in the auxiliary circuit 48 will be described. The liquid refrigerant accumulated in the lower part in the tank 36 flows from the tank 36 to the tank outlet pipe 37, and after passing through the second flow path 29B, is branched. One of the divided liquid refrigerant flows into the liquid pipe 46 and is throttled by the electric expansion valve 47. Thereafter, the liquid refrigerant flows into the intermediate pressure return pipe 44, merges with the gas refrigerant from the electric expansion valve 43, flows into the first flow path 29A of the split heat exchanger 29, and evaporates there. The heat absorption at this time increases the supercooling of the refrigerant flowing through the second flow path 29B.

  Thereafter, the gas refrigerant that has flowed out of the first flow path 29A flows into the intermediate pressure suction pipe 26 and mixes with the refrigerant that flowed out of the intercooler 24, so that the suction port 64 of the auxiliary compressor 60 and the high stage of the compressor 11 Each of the side suction ports 19 is sucked.

  The control device 57 controls the valve opening of the electric expansion valve 47 to adjust the amount of liquid refrigerant flowing through the first flow path 29A of the split heat exchanger 29. For example, the control device 57 controls the valve opening of the electric expansion valve 47 based on the temperature (discharge temperature) of the refrigerant discharged from the compressor 11 to the gas cooler 28 detected by the discharge temperature sensor 50. Thereby, the amount of the liquid refrigerant flowing through the first flow path 29A of the split heat exchanger 29 is adjusted, and the discharge temperature of the refrigerant discharged from the compressor 11 to the gas cooler 28 is controlled to a predetermined target value TDT. That is, when the actual discharge temperature is higher than the target value TDT, the valve opening degree of the electric expansion valve 47 is increased, and when it is lower, it is decreased. Thus, the discharge temperature of the refrigerant of the compressor 11 is maintained at the target value TDT, and the compressor 11 is protected.

(2-4) Effect of Refrigeration Unit R Next, effects obtained by the refrigeration unit R will be described with reference to FIGS.

  FIG. 8 is a PH diagram showing an operation state of the refrigeration apparatus R in an environment in a high temperature period. On the other hand, FIG. 9 shows an operation state of a refrigeration apparatus without an auxiliary compressor (refrigeration apparatus in which the auxiliary compressor 60, the pipes 68, 69, and the expander 72 are removed from the configuration of FIG. 7) in an environment in a high temperature period. FIG. The environment in the high-temperature period is, for example, an environment in which the outside air temperature is about 32 degrees Celsius (for example, summer).

  In FIG. 8, a line from X1 to X2 indicates pressure reduction by the electric expansion valve 33 and the expander 72. On the other hand, in FIG. 9, a line from X1 to X2 indicates pressure reduction by the electric expansion valve 33. 8 and 9, a line from X3 to X4, a line from X5 to X6, and a line from X3 to X8 are an electric expansion valve 39, an electric expansion valve 43, and an electric expansion valve, respectively. The reduced pressure by 47 is shown.

  8 and 9, X9 indicates a specific enthalpy / pressure when the refrigerant having passed through the electric expansion valve 43 and the refrigerant having passed through the electric expansion valve 47 are mixed. X10 indicates the specific enthalpy / pressure when the mixed refrigerant passes through the first flow path 29A of the split heat exchanger 29. X11 indicates the specific enthalpy / pressure when the refrigerant flowing through the intermediate pressure suction pipe 26 flows into each of the high-stage suction port 19 of the compressor 11 and the suction port 64 of the auxiliary compressor 60.

  As is clear from the comparison between FIGS. 8 and 9, the intermediate pressure (MP) of the refrigeration apparatus R can be lower than that of the refrigeration apparatus without the auxiliary compressor 60.

  As described above, in the two-stage compressor in which the first rotary compression element and the second rotary compression element are driven by the same rotary shaft, the excluded volume ratio between the low-stage side and the high-stage side is determined. The intermediate pressure is determined according to the excluded volume ratio. Therefore, it has not been possible to reduce the intermediate pressure by increasing the suction amount (exclusion volume) of the refrigerant only on the high stage side.

  In contrast, the refrigeration apparatus R of the present embodiment includes the auxiliary compressor 60 provided in parallel with the compressor 11 which is a two-stage compressor, thereby reducing the refrigerant suction amount (excluded volume) in the intermediate pressure section. We are increasing. Thereby, even if the excluded volume ratio in the compressor 11 is determined, the intermediate pressure can be reduced.

  By reducing the intermediate pressure, the pressure OP in the tank 36 (the pressure at the time of X3) can be reduced. As a result, the specific enthalpy at the outlet of the tank 36 can be reduced, and the refrigerating capacity can be secured. Further, it is possible to prevent the pressure OP in the tank 36 from exceeding the critical pressure CP in an environment in a high temperature period, and to perform gas-liquid separation. In addition, protection control (for example, medium pressure cut, step-out, etc.) for forcibly stopping the compressor 11 at a predetermined high pressure value (abnormal high pressure) can be avoided, and stable operation of the refrigeration apparatus R can be realized.

  Further, in the refrigeration apparatus R of the present embodiment, since the expansion energy collected by the expander 72 is used for the compression operation of the auxiliary compressor 60, power consumption for driving the auxiliary compressor 60 can be reduced.

  In the refrigeration apparatus R of the present embodiment, the point X2 in FIG. 8 moves to the left of the point X1 by recovering the expansion energy by the expander 72, so that the refrigerant separated in the tank 36 and flowing out of the gas pipe 42 is discharged. As the amount of steam decreases and the flow rate of the refrigerant compressed in the second stage of the compressor 11 and the auxiliary compressor 60 decreases, power consumption for driving the compressor 11 and the auxiliary compressor 60 can be reduced.

  Further, in the refrigeration apparatus R of the present embodiment, since the pressure of the refrigerant sent to the showcase 4 is reduced, the design pressure of the piping can be reduced, and a thin-walled pipe can be used.

  Further, in the refrigeration apparatus R of the present embodiment, the liquid refrigerant is held in the tank 36 and the amount thereof can be continuously changed, so that the amount of the refrigerant circulating in the refrigeration circuit 1 can be stably maintained at an appropriate amount.

  Further, in the refrigeration apparatus R of the present embodiment, the required degree of supercooling can be ensured by providing the tank 36 functioning as an economizer, the electric expansion valves 43 and 47, and the split heat exchanger 29.

  In the present embodiment, the configuration of the refrigeration apparatus R illustrated in FIG. 7 has been described, but the configuration of the refrigeration apparatus R is not limited to the configuration illustrated in FIG. Hereinafter, another configuration example of the refrigeration apparatus R will be described.

(3) Another configuration example 1 of the refrigeration apparatus R
FIG. 10 is a refrigerant circuit diagram of a refrigeration apparatus R having a configuration different from that of FIG. FIG. 10 is a simplified version of FIG. 7, and the same components as those in FIG. 7 are denoted by the same reference numerals, and the description thereof will be omitted below.

  The refrigeration apparatus R illustrated in FIG. 10 includes a compressor 11a in addition to the configuration illustrated in FIG. The compressor 11a is a two-stage compressor provided in parallel with the compressor 11, and has the same configuration as the compressor 11.

  In the refrigeration apparatus R shown in FIG. 10, the refrigerant from the evaporator 41 is sucked into each of the compressor 11 and the compressor 11a. The refrigerant in which the refrigerant from the intercooler 24 and the refrigerant from the intermediate pressure return pipe 44 are mixed is sucked into each of the compressor 11, the compressor 11a, and the auxiliary compressor 60.

  In FIG. 10, the electric expansion valve 39, the showcase 4, and the evaporator 41 are provided one by one. However, the electric expansion valve 39, the showcase 4, and the evaporator 41 are each provided with a plurality. It may be. For example, one electric expansion valve 39, one showcase 4, and one evaporator 41 are set as one set, and the set is provided in parallel.

(4) Another configuration example 2 of the refrigeration apparatus R
In the configuration shown in FIGS. 7 and 10, only one auxiliary compressor 60 is provided, but a plurality of auxiliary compressors 60 may be provided. The plurality of auxiliary compressors 60 are provided in parallel with each other, and are provided in parallel with one or more compressors 11 (compressors 11a). The refrigerant in which the refrigerant from the intercooler 24 and the refrigerant from the intermediate pressure return pipe 44 are mixed is sucked into each of the plurality of auxiliary compressors 60.

  As described above, in the present embodiment, the compressor (compression means) 11 having the first rotary compression element 14 and the second rotary compression element 16 driven by the same rotary shaft, the gas cooler 28, The refrigerant circuit 1 is configured by the expansion valve (main throttle means) 39 and the evaporator 41, and in the refrigeration apparatus R using carbon dioxide refrigerant, an auxiliary compressor (auxiliary compression means) provided in parallel with the compressor 11 60, an electric expansion valve (pressure regulating throttle means) 33 connected to the refrigerant circuit 1 downstream of the gas cooler 28 and upstream of the electric expansion valve 39 to adjust the pressure of the refrigerant flowing out of the gas cooler 28; Is connected to the refrigerant circuit 1 on the downstream side of the gas cooler 28 and on the upstream side of the electric expansion valve 39, and is provided in parallel with the electric expansion valve 33, and expands the refrigerant divided after flowing out of the gas cooler 28. Both are an expander (expansion means) 72 for recovering expansion energy, an electric expansion valve 33 and a tank 36 connected to the refrigerant circuit 1 downstream of the expander 72 and upstream of the electric expansion valve 39. A split heat exchanger 29 provided in the refrigerant circuit 1 downstream of the tank 36 and upstream of the electric expansion valve 39 and having a first flow path 29A and a second flow path 29B; An electric expansion valve (first auxiliary throttle means) 43 for adjusting the pressure of the refrigerant flowing out of the gas pipe 42 provided at the first height, and a tank outlet pipe provided at a position lower than the first height After flowing out of the second heat exchanger 37 and passing through the second flow passage 29B of the split heat exchanger 29, the electric expansion valve (the second expansion valve) adjusts the pressure of one of the refrigerants diverted downstream of the second flow passage 29B. Auxiliary expansion means) 47 and an electric expansion valve After flowing the refrigerant in which the refrigerant whose pressure has been adjusted by Step 3 and the refrigerant whose pressure has been adjusted by the electric expansion valve 47 are mixed, flows into the first flow path 29A of the split heat exchanger 29, and then the intermediate pressure section of the compressor 11 After the refrigerant flowing out of the tank 36 and the auxiliary circuit 48 sucked into the auxiliary compressor 60 flows into the second flow path 29B of the split heat exchanger 29, and exchanges heat with the refrigerant flowing through the first flow path 29A. A main circuit 38 for flowing the other of the refrigerant diverted on the downstream side of the second flow path 29B into the electric expansion valve 39, the compressor 11, the auxiliary compressor 60, the electric expansion valve 39, the electric expansion valve 33, A control device (control means) 57 for controlling the operation of the electric expansion valve 43, the electric expansion valve 47, and the expander 72 is provided. The expansion energy recovered by the expander 72 is used for the compression operation of the auxiliary compressor 60. This is used for And

  Thereby, when using the carbon dioxide refrigerant, it is possible to increase the suction amount (excluded volume) of the refrigerant in the intermediate pressure section, and to reduce the intermediate pressure even if the excluded volume ratio in the compressor 11 is determined. Can be. As a result, the specific enthalpy at the outlet of the tank 36 can be reduced, and the refrigerating capacity can be secured.

  Further, since the expansion energy collected by the expander 72 is used for the compression operation of the auxiliary compressor 60, power consumption for driving the auxiliary compressor 60 can be reduced.

  Also, by collecting expansion energy by the expander 72, the point X2 in FIG. 8 moves to the left from the point X1, so that the refrigerant vapor separated by the tank 36 and flowing out from the gas pipe 42 decreases, and the compressor 11 By reducing the flow rate of the refrigerant compressed by the second stage and the auxiliary compressor 60, power consumption for driving the compressor 11 and the auxiliary compressor 60 can be reduced.

  In the refrigerating apparatus R, the rotation speed of the auxiliary compressor 60 is variable.

  The refrigerating apparatus R includes a plurality of auxiliary compressors 60 provided in parallel with each other. The plurality of auxiliary compressors 60 have split heat generated after the pressures are adjusted by the electric expansion valves 43 and 47. The refrigerant flowing through the first flow path 29A of the exchanger 29 is sucked.

  Further, the refrigeration apparatus R includes a plurality of compressors 11 and 11a provided in parallel with each other. After that, the refrigerant flowing through the first flow path 29A of the split heat exchanger 29 is sucked.

  The second embodiment of the present invention has been described above.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention.

  The disclosure contents of the specification, drawings and abstract included in the Japanese application of Japanese Patent Application No. 2006-022114 filed on Feb. 8, 2016 and the Japanese application of Japanese Patent Application No. 2006-022117 filed on Feb. 8, 2016 are as follows. All are incorporated herein by reference.

  INDUSTRIAL APPLICABILITY The present invention is suitable for use in a refrigerating apparatus in which a refrigerant circuit includes a compression unit, a gas cooler, a main throttle unit, and an evaporator.

R Refrigerator 1 Refrigerant circuit 3 Refrigerator unit 4 Showcase 6 Unit outlet 7 Unit inlet 8, 9 Refrigerant piping 11, 11a Compressor 12, 61 Closed vessel 13, 62 Electric element 14 First rotary compression element 16 Second Rotary compression element 17 Low-stage suction port 18 Low-stage discharge port 19 High-stage suction port 21 High-stage discharge port 22 Refrigerant introduction pipe 23 Intermediate pressure discharge pipe 24 Intercooler 26 Intermediate pressure suction pipe 27 High pressure discharge pipe 28 Gas cooler 29 Split heat exchanger 29A First flow path 29B Second flow path 31 Gas cooler blower 32 Gas cooler outlet pipe 33 Electric expansion valve (pressure regulating throttle means)
34 tank inlet piping 36 tank 37 tank outlet piping 38 main circuit 39 electric expansion valve (main throttle means)
41 evaporator 42 gas pipe 43 electric expansion valve (first auxiliary circuit throttle means)
44 Intermediate pressure return pipe 46 Liquid pipe 47 Electric expansion valve (second auxiliary circuit throttle means)
48 Auxiliary circuit 49 High pressure sensor 50 Discharge temperature sensor 51 Low pressure sensor 52 Intermediate pressure sensor 53 Unit outlet sensor 57 Control device (control means)
Reference Signs List 60 auxiliary compressor 63 rotary compression element 64 suction port 65 discharge port 70 bypass circuit 71 solenoid valve 72 expander

Claims (9)

A refrigerant circuit includes a compression unit having a first rotary compression element and a second rotary compression element driven by the same rotary shaft, a gas cooler, a main throttle unit, and an evaporator. Refrigeration equipment,
Auxiliary compression means provided in parallel with the compression means,
On the downstream side of the gas cooler, connected to the refrigerant circuit on the upstream side of the main throttle means, pressure adjusting throttle means for adjusting the pressure of the refrigerant flowing out of the gas cooler,
A tank connected to the refrigerant circuit on the downstream side of the pressure adjusting throttle unit and upstream of the main throttle unit,
A split heat exchanger provided in the refrigerant circuit on the downstream side of the tank and on the upstream side of the main throttle means, and having a first flow path and a second flow path;
First auxiliary throttle means for adjusting the pressure of the refrigerant flowing out of a pipe provided at a first height of the tank;
After flowing out of a pipe provided at a position lower than the first height and passing through the second flow path of the split heat exchanger, of the refrigerant divided on the downstream side of the second flow path, A second auxiliary throttle means for adjusting one of the pressures;
A refrigerant in which a refrigerant whose pressure has been adjusted by the first auxiliary throttle unit and a refrigerant whose pressure has been adjusted by the second auxiliary throttle unit has flowed into the first flow path of the split heat exchanger. Later, an auxiliary circuit for sucking the intermediate pressure portion of the compression means and the auxiliary compression means,
The refrigerant flowing out of the tank flows into the second flow path of the split heat exchanger, and after exchanging heat with the refrigerant flowing through the first flow path, the refrigerant is separated at the downstream side of the second flow path. A main circuit for causing the other of the refrigerant to flow into the main throttle means,
Control means for controlling the operation of the compression means, the auxiliary compression means, the main throttle means, the pressure adjustment throttle means, the first auxiliary throttle means, and the second auxiliary throttle means.
Refrigeration equipment. The auxiliary compression unit further includes a bypass circuit that connects a pipe provided downstream of the evaporator and upstream of the compression unit,
The bypass circuit is provided with a check valve, or an electromagnetic valve whose opening and closing are controlled by the control unit.
The refrigeration apparatus according to claim 1. The rotation speed of the auxiliary compression means is variable,
The refrigeration apparatus according to claim 1. Apart from the auxiliary compression means, in parallel with the auxiliary compression means, comprises at least one auxiliary compression means,
The at least one auxiliary compression means includes:
The refrigerant flowing through the first flow path of the split heat exchanger is sucked after the pressure is adjusted by the first auxiliary throttle means and the second auxiliary throttle means,
The refrigeration apparatus according to any one of claims 1 to 3. Apart from the compression means, in parallel with the compression means, comprises at least one compression means,
In the intermediate pressure portion of the at least one compression means,
The refrigerant flowing through the first flow path of the split heat exchanger is sucked after the pressure is adjusted by the first auxiliary throttle means and the second auxiliary throttle means,
The refrigeration apparatus according to claim 1. A refrigerant circuit includes a compression unit having a first rotary compression element and a second rotary compression element driven by the same rotary shaft, a gas cooler, a main throttle unit, and an evaporator. Refrigeration equipment,
Auxiliary compression means provided in parallel with the compression means,
On the downstream side of the gas cooler, connected to the refrigerant circuit on the upstream side of the main throttle means, pressure adjusting throttle means for adjusting the pressure of the refrigerant flowing out of the gas cooler,
On the downstream side of the gas cooler, connected to the refrigerant circuit on the upstream side of the main throttle means, provided in parallel with the pressure adjustment throttle means, and expands the refrigerant that has been divided after flowing out of the gas cooler, Expansion means for recovering expansion energy;
A tank connected to the refrigerant circuit on the upstream side of the main throttle unit, on the downstream side of the pressure adjustment throttle unit and the expansion unit,
A split heat exchanger provided in the refrigerant circuit on the downstream side of the tank and on the upstream side of the main throttle means, and having a first flow path and a second flow path;
First auxiliary throttle means for adjusting the pressure of refrigerant flowing out of a pipe provided at a first height of the tank;
After flowing out of a pipe provided at a position lower than the first height, and after passing through the second flow path of the split heat exchanger, of the refrigerant divided on the downstream side of the second flow path, A second auxiliary throttle means for adjusting one of the pressures;
A refrigerant in which a refrigerant whose pressure has been adjusted by the first auxiliary throttle unit and a refrigerant whose pressure has been adjusted by the second auxiliary throttle unit has flowed into the first flow path of the split heat exchanger. Later, an auxiliary circuit for sucking the intermediate pressure portion of the compression means and the auxiliary compression means,
The refrigerant flowing out of the tank flows into the second flow path of the split heat exchanger and exchanges heat with the refrigerant flowing through the first flow path. A main circuit for causing the other of the two to flow into the main throttle means,
Control means for controlling operations of the compression means, the auxiliary compression means, the main throttle means, the pressure adjustment throttle means, the first auxiliary throttle means, the second auxiliary throttle means, and the expansion means; ,
The expansion energy recovered by the expansion means is used for a compression operation of the auxiliary compression means,
Refrigeration equipment. The rotation speed of the auxiliary compression means is variable,
The refrigeration apparatus according to claim 6. Apart from the auxiliary compression means, in parallel with the auxiliary compression means, comprises at least one auxiliary compression means,
The at least one auxiliary compression means includes:
The refrigerant flowing through the first flow path of the split heat exchanger is sucked after the pressure is adjusted by the first auxiliary throttle means and the second auxiliary throttle means,
The refrigeration apparatus according to claim 6. Apart from the compression means, in parallel with the compression means, comprises at least one compression means,
In the intermediate pressure portion of the at least one compression means,
The refrigerant flowing through the first flow path of the split heat exchanger is sucked after the pressure is adjusted by the first auxiliary throttle means and the second auxiliary throttle means,
The refrigeration apparatus according to any one of claims 6 to 8.