JP6653463B2 - 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 the refrigeration apparatus configured to use a carbon dioxide refrigerant, an auxiliary compression means provided separately from the compression means and a refrigerant circuit downstream of the gas cooler and upstream of the main throttle means are 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 A first auxiliary throttle means for adjusting the pressure of the refrigerant flowing out of the first pipe, and a second auxiliary pipe provided at a position lower than the first height and flowing out of the second pipe, After passing through the second flow path, the second auxiliary throttle means for adjusting the pressure of the first refrigerant among the refrigerants diverted downstream of the second flow path, and flows out of the second pipe. A third auxiliary throttle means for adjusting a pressure of a second refrigerant among refrigerants diverted downstream of the second flow path after passing through the second flow path of the split heat exchanger; An auxiliary circuit for sucking the refrigerant having passed through the third flow path of the third auxiliary throttle means and the first flow path of the split heat exchanger into the auxiliary compression means, and an open / close valve, which flowed out of the first pipe. The first refrigerant of the split heat exchanger in the auxiliary circuit A first bypass circuit that flows into the downstream side of the road, and a refrigerant in which a refrigerant whose pressure is adjusted by the first auxiliary throttle unit and a refrigerant whose pressure is adjusted by the second auxiliary throttle unit are mixed. A return circuit for sucking the intermediate pressure portion of the compression means, and a refrigerant flowing out of the tank flows into the second flow path of the split heat exchanger, and a refrigerant flows through the first flow path of the split heat exchanger. A main circuit for causing a third refrigerant of the refrigerant diverted downstream of the second flow path to flow into the main throttle means after heat exchange with the main flow path, the compression means, the auxiliary compression means, A throttle unit, the pressure adjusting throttle unit, the first auxiliary throttle unit, the second auxiliary throttle unit, the third auxiliary throttle unit, and a control unit for controlling an operation of the on-off valve. Take the configuration.

  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 PH diagram showing an operation state according to an operation example 1 of the refrigeration apparatus. PH diagram showing an operation state according to an operation example 2 of the refrigeration apparatus. 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 apparatus shown in FIG. 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 apparatus shown in FIG. FIG. 1 is a refrigerant circuit diagram of a refrigeration apparatus having a different configuration from FIG.

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

(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 connected to the high-stage suction port 19 of the compressor 11.

  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.

  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 is located downstream of the gas cooler 28 and upstream of the electric expansion valve 39. 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. One end of a tank outlet pipe 37 is connected to a lower portion of the tank 36, and the other end of the tank outlet pipe 37 is connected to the refrigerant pipe 8 at the unit outlet 6. 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. The tank 36 is located downstream of the electric expansion valve 33 and upstream of the electric expansion valve 39. The split heat exchanger 29 is located downstream of the tank 36 and upstream of the electric expansion valve 39.

  One end of a gas pipe 42 is connected to an upper part of the tank 36. 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 an outlet of the electric expansion valve 43. The other end of the intermediate pressure return pipe 44 communicates with the intermediate pressure suction pipe 26 that is connected to the intermediate pressure section of the compressor 11.

  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.

  Further, one end of the branch pipe 71 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 branch pipe 71 is connected to a suction port 64 of the auxiliary compressor 60. The configuration of the auxiliary compressor 60 will be described later.

  In the middle of the branch pipe 71, an electric expansion valve 70 (an example of a third auxiliary circuit throttle unit) is arranged. A first flow path 29A of the split heat exchanger 29 is provided in the middle of the branch pipe 71 on the downstream side of the electric expansion valve 70.

  The branch pipe 71 is connected to the bypass circuit 73 on the downstream side of the first flow path 29A. The other end of the bypass circuit 73 is connected to the gas pipe 42. In the bypass circuit 73, an electromagnetic valve 74 is provided. The solenoid valve 74 is controlled by the control device 57 to either the open state or the closed state.

  The refrigerant that has passed through the second flow path 29B of the split heat exchanger 29 has three directions (the first refrigerant flowing to the electric expansion valve 47 and the first refrigerant flowing to the electric expansion valve 70) on the downstream side of the second flow path 29B. (The third refrigerant flowing to the electric expansion valve 39).

  The above-described electric expansion valve 43 (first auxiliary circuit throttle unit), electric expansion valve 47 (second auxiliary circuit throttle unit), and electric expansion valve 70 (third auxiliary circuit throttle unit) This constitutes the auxiliary throttle means in the embodiment. The branch pipe 71 constitutes the auxiliary circuit 48 in the present embodiment. The intermediate pressure return pipe 44 constitutes a return circuit 80 in the present embodiment.

  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.

  The refrigerator unit 3 includes an auxiliary compressor 60 (an example of an auxiliary compression unit). 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.

  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 a branch pipe 71 is connected to the suction port 64. The discharge port 65 is connected to one end of a pipe 72. The other end of the pipe 72 is connected to the high-pressure discharge pipe 27.

  The rotary compression element 63 compresses the refrigerant sucked from the branch pipe 71, 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.

  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. 70, the electric expansion valve 39, and the solenoid valve 74 are 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).

  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 flows into the high-stage suction port 19 (intermediate pressure section) of the compressor 11.

  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.

(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, the refrigerant gas in a supercritical state from the gas cooler 28 is reduced in pressure by the electric expansion valve 33 to be in a gas-liquid two-phase mixed state, and flows into the tank 36 from above via the tank inlet pipe 34. 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 flowing from the tank 36 to the tank outlet pipe 37 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 return circuit 80 will be described. The temperature of the gas refrigerant accumulated in the upper portion of the tank 36 is reduced by the pressure reduction of the electric expansion valve 33. 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 intermediate pressure return pipe 44 and mixes with the refrigerant that has passed through the electric expansion valve 47. Then, the refrigerant flows into the intermediate pressure suction pipe 26 from the intermediate pressure return pipe 44, mixes with the refrigerant discharged from the intercooler 24, and is sucked into the high-stage suction port 19 of the compressor 11.

  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 when the refrigeration apparatus R is started (the 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 when 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 into the return circuit 80. Will be able to Conversely, by reducing the valve opening of the electric expansion valve 43, the amount of refrigerant flowing into the return circuit 80 is reduced, and the inconvenience of reducing the pressure of the refrigerant at the unit outlet 6 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 return circuit 80 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 refrigerants 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 and mixes with the refrigerant having passed through the electric expansion valve 43. Then, the refrigerant flows into the intermediate pressure suction pipe 26 from the intermediate pressure return pipe 44, mixes with the refrigerant discharged from the intercooler 24, and is sucked into the high-stage suction port 19 of the compressor 11.

  The valve opening of the electric expansion valve 47 is set by the control device 57. For example, when the temperature (discharge temperature) of the refrigerant discharged from the high-stage discharge port 21 of the compressor 11 is higher than a target value, the control device 57 sets the electric expansion valve 47 to the open state. The discharge temperature is detected by a discharge temperature sensor (not shown) and is input to the control device 57.

(3-1) Control of the Electric Expansion Valve 70 and the Solenoid Valve 74 In the present embodiment, the opening and closing of the electric expansion valve 70 and the solenoid valve 74 are controlled by the control device 57, so that the flow of the refrigerant flowing out of the tank 36 is reduced. Can switch. Hereinafter, each of Operation Example 1 and Operation Example 2 will be described.

<Operation example 1>
In this operation example, the control device 57 sets the electric expansion valve 70 to the closed state (the state where the valve opening is zero) and sets the solenoid valve 74 to the open state (an example of a first setting). . In this case, the flow of the refrigerant flowing out of the tank 36 is as follows.

  The refrigerant flowing from the tank 36 into the tank outlet pipe 37 passes through the second flow path 29B of the split heat exchanger 29, and then flows through the branch pipe 71 because the electric expansion valve 70 is in the closed state. It flows into each of the expansion valve 47 and the electric expansion valve 39.

  Further, the refrigerant flowing from the tank 36 into the gas pipe 42 is divided in the gas pipe 42.

  As described above, one of the refrigerants branched in the gas pipe 42 is throttled by the electric expansion valve 43, then flows into the intermediate pressure return pipe 44, mixes with the refrigerant that has passed through the electric expansion valve 47, and returns to the intermediate pressure return. It flows into the intermediate pressure suction pipe 26 from the pipe 44. Thereafter, the refrigerant mixes with the refrigerant from the intercooler 24 and is drawn into the high-stage suction port 19 of the compressor 11 from the intermediate-pressure suction pipe 26. The sucked refrigerant is compressed by the second rotary compression element 16 and becomes a high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure refrigerant is discharged from the high-stage discharge port 21 and flows into the high-pressure discharge pipe 27.

  The other of the refrigerant diverted in the gas pipe 42 flows into the bypass circuit 73, passes through the solenoid valve 74 in the open state, and flows into the branch pipe 71. Thereafter, the refrigerant is sucked from the branch pipe 71 into the suction port 64 of the auxiliary compressor 60. When the electric element 62 of the auxiliary compressor 60 is driven by the control device 57, the rotary compression element 63 rotates. Thus, the sucked refrigerant is compressed by the rotary compression element 63 and becomes a high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure refrigerant flows into the high-pressure discharge pipe 27 from the discharge port 65 via the pipe 72 and mixes with the refrigerant discharged from the high-stage discharge port 21 of the compressor 11.

  Next, effects obtained by this operation example will be described with reference to FIGS.

  FIG. 2 is a PH diagram showing an operation state of the refrigeration apparatus having no auxiliary compressor in an environment in a high temperature period. This refrigeration apparatus has, for example, a configuration in which the auxiliary compressor 60, the electric expansion valve 70, the branch pipe 71, the pipe 72, the bypass circuit 73, and the solenoid valve 74 are removed from the configuration shown in FIG. This is a configuration in which a first flow path 29A of the heat exchanger 29 is provided. 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 X3 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. A line extending obliquely upward from X5 indicates a pressure increase by the auxiliary compressor 60, and a line extending obliquely upward from X11 indicates a pressure increase by the compressor 11.

  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. X11 indicates a specific enthalpy / pressure when the refrigerant flowing through the intermediate pressure suction pipe 26 flows into the high-stage suction port 19 of the compressor 11. X5 in FIG. 3 indicates the specific enthalpy / pressure when flowing into the suction port 64 of 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.

  On the other hand, in the refrigeration apparatus R of the present embodiment, the auxiliary compressor 60 is provided separately from the compressor 11 which is a two-stage compressor, and the solenoid valve 74 of the bypass circuit 73 is opened. Only in this case, the refrigerant suction amount (exclusion volume) is increased. 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.

<Operation example 2>
In this operation example, the control device 57 sets the electric expansion valve 70 to an open state (a state in which the valve opening is larger than zero) and sets the solenoid valve 74 to a closed state (an example of a second setting). ). In this case, the flow of the refrigerant flowing out of the tank 36 is as follows.

  The refrigerant flowing from the tank 36 into the gas pipe 42 does not flow through the bypass circuit 73 because the solenoid valve 74 is closed, but flows into the electric expansion valve 43. Then, as described above, the refrigerant is throttled by the electric expansion valve 43, then flows into the intermediate pressure return pipe 44, mixes with the refrigerant having passed through the electric expansion valve 47, and flows from the intermediate pressure return pipe 44 to the intermediate pressure suction pipe 26. Flows into. Thereafter, the refrigerant mixes with the refrigerant from the intercooler 24 and is drawn into the high-stage suction port 19 of the compressor 11 from the intermediate-pressure suction pipe 26. The sucked refrigerant is compressed by the second rotary compression element 16 and becomes a high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure refrigerant is discharged from the high-stage discharge port 21 and flows into the high-pressure discharge pipe 27.

  Further, the refrigerant flowing from the tank 36 into the tank outlet pipe 37 passes through the second flow path 29B of the split heat exchanger 29, and is then split into three.

  One of the three divided refrigerants after passing through the second flow path 29B flows into the electric expansion valve 39.

  In addition, one of the three refrigerants that have diverted after passing through the second flow path 29B flows into the liquid pipe 46, is throttled by the electric expansion valve 47, and then flows into the intermediate pressure return pipe 44, It mixes with the refrigerant that has passed through the electric expansion valve 43.

  Further, one of the refrigerants branched after passing through the second flow path 29 </ b> B flows into the electric expansion valve 70, is throttled by the electric expansion valve 70, and then flows through the first flow path of the split heat exchanger 29. Flows into 29A where it evaporates. The heat absorption at this time increases the supercooling of the refrigerant flowing through the second flow path 29B. Then, the refrigerant that has passed through the first flow path 29A is sucked from the branch pipe 71 into the suction port 64 of the auxiliary compressor 60. When the electric element 62 of the auxiliary compressor 60 is driven by the control device 57, the rotary compression element 63 rotates. Thus, the sucked refrigerant is compressed by the rotary compression element 63 and becomes a high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure refrigerant flows into the high-pressure discharge pipe 27 from the discharge port 65 via the pipe 72 and mixes with the refrigerant discharged from the high-stage discharge port 21 of the compressor 11.

  In this operation example, the control device 57 adjusts the amount of the liquid refrigerant flowing through the first flow path 29A of the split heat exchanger 29 by controlling the electric expansion valve 70 to the open state. Here, an example of control of the valve opening of the electric expansion valve 70 in this operation example will be described.

  For example, based on the temperature of the showcase 4, the controller 57 first determines the temperature at the outlet of the second flow path 29B of the split heat exchanger 29 (hereinafter referred to as the outlet temperature. Temperature). Next, the controller 57 determines a temperature at which the refrigerant is evaporated in the split heat exchanger 29 (hereinafter, referred to as an evaporation temperature, for example, a temperature at X13 in FIG. 4 described later) as a temperature lower than the outlet temperature. Then, the control device 57 sets the valve opening of the electric expansion valve 70 so that the temperature of the refrigerant in the first flow path 29A becomes the evaporation temperature.

  Next, effects obtained by this operation example will be described with reference to FIG.

  FIG. 4 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, in summer).

  4, the same elements as those in FIGS. 2 and 3 are denoted by the same reference numerals. The line from X3 to X13 indicates the pressure reduction by the electric expansion valve 70. The dotted line L1 indicates the specific enthalpy / pressure from when the refrigerant throttled by the electric expansion valve 70 flows out of the electric expansion valve 70, flows through the auxiliary compressor 60, and flows into the high-pressure discharge pipe 27.

  As is clear from the lines from X2 to X3 shown in FIGS. 3 and 4, in this operation example, a greater degree of supercooling can be ensured, so that the refrigerating capacity can be ensured. However, in the present operation example, since the intermediate pressure is fixed at the excluded volume ratio of the compressor 11, for example, when the outside air temperature is high or when the cooling condition of the showcase 4 is set to the middle temperature zone, the intermediate pressure is fixed. When the pressure increases, protection control (for example, medium pressure cut, step-out, etc.) is required.

(3-2) Switching control between operation example 1 and operation example 2 For example, the control device 57 responds to an operation performed by the user (operation for instructing which of the operation example 1 and the operation example 2 to execute). Control may be performed to execute either Operation Example 1 or Operation Example 2.

  Alternatively, for example, the control device 57 normally controls the operation example 2 to be executed, and when the intermediate pressure MP detected by the intermediate pressure sensor 52 becomes higher than a preset threshold, the control device 57 starts the operation example 2. Control may be performed so as to switch to the first operation example. Thus, the intermediate pressure can be reduced without performing protection control.

  The control device 57 may switch between the first operation example and the second operation example in accordance with the outside air temperature, the cooling condition of the showcase 4, and the like.

  The operation example 1 and the operation example 2 have been described above. The refrigerating apparatus R of the present embodiment can obtain the following effects in addition to the effects obtained by the above-described operation example 1 and the operation example 2.

  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 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. 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.

(4) Another configuration example 1 of the refrigeration apparatus R
FIG. 5 is a refrigerant circuit diagram of a refrigeration apparatus R having a configuration different from that of FIG. In FIG. 5, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted below.

  The refrigerating apparatus R shown in FIG. 5 includes an electric expansion valve 75 instead of the electromagnetic valve 74 in the bypass circuit 73 shown in FIG.

  In this operation example, the control device 57 sets the electric expansion valve 70 and the electric expansion valve 75 to an open state (a state where the valve opening is greater than zero) (an example of a third setting).

  The valve opening of the electric expansion valve 70 is set, for example, as follows. First, the control device 57 determines the outlet temperature of the second flow path 29B of the split heat exchanger 29 (for example, the temperature at X3 in FIG. 6 described later) based on the temperature of the showcase 4. Next, the control device 57 determines an evaporation temperature (for example, a temperature at X15 in FIG. 6 described later) at which the refrigerant is evaporated in the split heat exchanger 29 as a temperature lower than the outlet temperature. Then, the control device 57 sets the valve opening of the electric expansion valve 70 so that the temperature of the refrigerant in the first flow path 29A becomes the evaporation temperature.

  The valve opening of the electric expansion valve 75 is set, for example, as follows. The control device 57 controls the electric expansion valve based on the intermediate pressure detected by the intermediate pressure sensor 52 and the temperature of the refrigerant discharged from the auxiliary compressor 60 (hereinafter, referred to as discharge refrigerant temperature, which is detected by a sensor (not shown)). A valve opening of 75 is set. For example, when the detected intermediate pressure is higher than the target value and the detected discharge refrigerant temperature is lower than the target value, the control device 57 controls the electric expansion valve 75 to a closed state.

  Next, effects obtained by the operation of this configuration example will be described with reference to FIG.

  FIG. 6 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, in summer).

  6, the same elements as those in FIGS. 2 and 3 are denoted by the same reference numerals. The line from X3 to X15 indicates the pressure reduction by the electric expansion valve 70. The dotted line L2 indicates the specific enthalpy / pressure from when the refrigerant throttled by the electric expansion valve 70 flows out of the electric expansion valve 70, flows through the auxiliary compressor 60, and flows into the high-pressure discharge pipe 27.

  As is clear from a comparison between FIG. 3 (operation example 1) and FIG. 6, in the operation of this configuration example, the intermediate pressure is higher than in operation example 1, but the degree of supercooling can be ensured. As is apparent from a comparison between FIG. 4 (operation example 2) and FIG. 6, in the operation of this configuration example, the degree of supercooling cannot be secured as compared with operation example 2, but the intermediate pressure can be reduced.

(5) Another configuration example 2 of the refrigeration apparatus R
FIG. 7 is a refrigerant circuit diagram of a refrigeration apparatus R having a configuration different from that of FIG. In FIG. 7, 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 illustrated in FIG. 7 includes a bypass circuit 82 and a solenoid valve 81 in addition to the configuration illustrated in FIG. One end of the bypass circuit 82 is connected to the refrigerant introduction pipe 22, and the other end of the bypass circuit 82 is connected to the suction port 64 of the auxiliary compressor 60.

  In the middle of the bypass circuit 82, an electromagnetic valve 81 is provided. The opening and closing of the solenoid valve 81 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 81, estimates the outside air temperature, and refers to the data table to determine the electromagnetic The opening and closing of the valve 81 is set. Note that a check valve may be provided instead of the electromagnetic valve 81.

  For example, when the outside air temperature is about 32 degrees Celsius (high-temperature environment, for example, in summer), the controller 57 closes the solenoid valve 81 and drives the compressor 11 and the auxiliary compressor 60. Thereby, the refrigerant circulates as described in the operation example 1 or the operation example 2 described above.

  On the other hand, for example, when the outside air temperature is equal to or lower than 20 degrees Celsius (low-temperature environment; for example, in winter), the control device 57 opens the solenoid valve 81, does not drive the compressor 11, and operates the auxiliary compressor. 60 is driven. The control device 57 maximizes the valve opening of the electric expansion valve 33 and closes the electric expansion valve 43, the electric expansion valve 47, and the electric expansion valve 70.

  Thus, the refrigerant that has exited from the evaporator 41 flows into the bypass circuit 82 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 82 Flows into.

  FIG. 8 shows a PH diagram when the refrigerant flows through the bypass circuit 82. 8 are the same as those in FIGS. 2 and 3. As shown in FIG. 8, 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.

  The bypass circuit 82 and the solenoid valve 81 (or the check valve) may be added to the configuration shown in FIG.

(6) Another configuration example 3 of the refrigeration apparatus R
FIG. 9 is a refrigerant circuit diagram of a refrigeration apparatus R having a configuration different from that of FIG. FIG. 9 is a simplified version of FIG. 1, and the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted below.

  The refrigeration apparatus R illustrated in FIG. 9 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. 9, 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 drawn into each of the compressor 11 and the compressor 11a.

  In FIG. 9, 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.

  The compressor 11a may be added to the configuration shown in FIG.

(7) Another configuration example 4 of the refrigeration apparatus R
In the configurations shown in FIGS. 1, 5, 7, and 9, only one auxiliary compressor 60 is provided, but a plurality of auxiliary compressors 60 may be provided. In that case, the refrigerant from the branch pipe 71 is sucked into each of the plurality of auxiliary compressors 60.

  As described above, in the present embodiment, the compressor 11 (compression means) 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 constituted by the expansion valve (main throttle means) 39 and the evaporator 41, and in the refrigeration apparatus R using carbon dioxide refrigerant, the auxiliary compressor 60 (auxiliary compression means) provided separately from the compressor 11 is provided. ), An electric expansion valve 33 (pressure regulating throttle means) connected to the refrigerant circuit 1 downstream of the gas cooler 28 and upstream of the electric expansion valve 39 and adjusting the pressure of the refrigerant flowing out of the gas cooler 28. 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 refrigerant circuit downstream of the tank 36 and upstream of the electric expansion valve 39. Provided in 1 , The split heat exchanger 29 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 (first pipe) provided at the first height of the tank 36. Flow from a motor-operated expansion valve 43 (first auxiliary throttle means) for adjusting pressure and a tank outlet pipe 37 (second pipe) provided at a position lower than the first height. An electric expansion valve 47 (second auxiliary throttle means) for adjusting the pressure of the first refrigerant of the refrigerant diverted downstream of the second flow path 29B after passing through the second flow path 29B; After flowing out of the outlet pipe 37 and passing through the second flow path 29B of the split heat exchanger 29, an electric motor that adjusts the pressure of the second refrigerant among the refrigerants diverted downstream of the second flow path 29B. Expansion valve 70 (third auxiliary throttle means), electric expansion valve 70 and An auxiliary circuit 48 for sucking refrigerant passing through the first flow path 29A of the split heat exchanger 29 into the auxiliary compressor 60, and a solenoid valve 74 or an electric expansion valve 75 (open / close valve) are provided. A bypass circuit 73 (first bypass circuit) for allowing the refrigerant to flow downstream of the first flow path 29A of the split heat exchanger 29 in the auxiliary circuit 48; a refrigerant whose pressure has been adjusted by the electric expansion valve 43; The return circuit 80 for allowing the refrigerant mixed with the refrigerant whose pressure has been adjusted by the valve 47 to be sucked into the intermediate pressure portion of the compressor 11 and the refrigerant flowing out of the tank 36 to the second flow passage 29B of the split heat exchanger 29 After flowing and exchanging heat with the refrigerant flowing through the first flow path 29A of the split heat exchanger 29, the refrigerant of the refrigerant divided at the downstream side of the second flow path 29B flows into the electric expansion valve 39. Of the compressor 11, the auxiliary compressor 60, the electric expansion valve 39, the electric expansion valve 33, the electric expansion valve 43, the electric expansion valve 47, the electric expansion valve 70, and the solenoid valve 74 or the electric expansion 75 A control device 57 (control means) for controlling the operation.

  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 control device 57 sets the electric expansion valve 70 to the closed state and the electromagnetic valve 74 to the first state, and sets the electric expansion valve 70 to the open state and the electromagnetic valve 74 to the closed state. Switch to the second setting.

  Further, the control device 57 performs the third setting to open the electric expansion valve 70 and open the electric expansion valve 75.

  Further, the refrigeration apparatus R further includes a bypass circuit 82 (second bypass circuit) that connects the auxiliary compressor 60 and the refrigerant introduction pipe 22 provided downstream of the evaporator 41 and upstream of the compressor 11. The bypass circuit 82 is provided with a check valve or an electromagnetic valve 81 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.

  Further, the refrigeration apparatus R includes a plurality of auxiliary compressors 60, and the refrigerant flowing through the auxiliary circuit 48 is sucked into the plurality of auxiliary compressors 60.

  The refrigerating apparatus R includes a plurality of compressors 11 and 11a provided in parallel with each other. An intermediate pressure portion of the plurality of compressors 11 and 11a is provided with a refrigerant whose pressure is adjusted by the electric expansion valve 43 and an electric motor. The refrigerant mixed with the refrigerant whose pressure is adjusted by the expansion valve 47 is sucked.

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

  The disclosure contents of the specification, drawings and abstract included in Japanese Patent Application No. 2006-022124 filed on Feb. 8, 2016 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 (third piping)
38 Main circuit 39 Electric expansion valve (Main throttle means)
41 Evaporator 42 Gas pipe (first pipe)
43 electric expansion valve (first auxiliary circuit throttle means)
44 Intermediate pressure return pipe 46 Liquid pipe (second pipe)
47 Electric expansion valve (second auxiliary circuit throttle means)
48 Auxiliary circuit 49 High pressure 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 electric expansion valve (third auxiliary circuit throttle means)
71 Branch piping (fourth piping)
72 piping 73 bypass circuit (first bypass circuit)
74, 81 Solenoid valve 75 Electric expansion valve 82 Bypass circuit (second bypass circuit)

Claims (7)

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 separately from 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 refrigerant flowing out of a first pipe provided at a first height of the tank;
After flowing out of a second pipe provided at a position lower than the first height, and passing through the second flow path of the split heat exchanger, the flow splits downstream of the second flow path. Second auxiliary throttle means for adjusting the pressure of the first refrigerant of the refrigerant,
After flowing out of the second pipe and passing through the second flow path of the split heat exchanger, the pressure of the second refrigerant of the refrigerant diverted downstream of the second flow path is adjusted. A third auxiliary aperture means,
An auxiliary circuit for sucking the refrigerant having passed through the first flow path of the third auxiliary throttle means and the split heat exchanger into the auxiliary compression means;
An on-off valve provided, a first bypass circuit for causing the refrigerant flowing out of the first pipe to flow into the auxiliary circuit downstream of the first flow path of the split heat exchanger,
A return circuit for sucking a refrigerant in which the refrigerant whose pressure is adjusted by the first auxiliary throttle means and the refrigerant whose pressure is adjusted by the second auxiliary throttle means is mixed into the intermediate pressure portion of the compression means;
After flowing the refrigerant flowing out of the tank into the second flow path of the split heat exchanger and exchanging heat with the refrigerant flowing through the first flow path of the split heat exchanger, the second flow path A main circuit for causing a third refrigerant of the refrigerant divided on the downstream side of the main flow to flow into the main throttle means,
The compression unit, the auxiliary compression unit, the main throttle unit, the pressure adjustment throttle unit, the first auxiliary throttle unit, the second auxiliary throttle unit, the third auxiliary throttle unit, and the on-off valve Control means for controlling the operation of
Refrigeration equipment. The on-off valve is a solenoid valve,
The control means includes:
A first setting for closing the third auxiliary throttle unit and opening the solenoid valve, and for opening the third auxiliary throttle unit and closing the solenoid valve. Switch between the second setting,
The refrigeration apparatus according to claim 1. The on-off valve is an electric expansion valve,
The control means includes:
Making a third setting to open the third auxiliary throttle means and open the electric expansion valve;
The refrigeration apparatus according to claim 1. A second bypass circuit that connects the auxiliary compression unit and a pipe provided downstream of the evaporator and upstream of the compression unit,
The second 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, at least one auxiliary compression means,
The at least one auxiliary compression means includes:
The refrigerant flowing through the auxiliary circuit is sucked,
The refrigeration apparatus according to claim 1. 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,
A refrigerant in which a refrigerant whose pressure is adjusted by the first auxiliary throttle unit and a refrigerant whose pressure is adjusted by the second auxiliary throttle unit is mixed is sucked.
The refrigeration apparatus according to claim 1.