JP6264688B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to a refrigeration apparatus in which a refrigerant circuit is configured by a compression unit, a gas cooler, a main throttle unit, and an evaporator, and a high pressure side is a supercritical pressure.

  Conventionally, this type of refrigeration apparatus has a refrigeration cycle composed of a compression means, a gas cooler, a throttle means, etc., and the refrigerant compressed by the compression means dissipates heat in the gas cooler and is depressurized by the throttle means, and then in an evaporator. The refrigerant was evaporated, and ambient air was cooled by evaporation of the refrigerant at this time. In recent years, chlorofluorocarbon refrigerants cannot be used in this type of refrigeration system due to natural environmental problems. For this reason, the thing using the carbon dioxide which is a natural refrigerant | coolant is developed as a substitute of a fluorocarbon refrigerant | coolant. The carbon dioxide refrigerant is a refrigerant having a high and low pressure difference, and has a low critical pressure. It is known that the high pressure side of the refrigerant cycle is brought into a supercritical state by compression (see, for example, Patent Document 1).

  Moreover, in the heat pump device constituting the water heater, a carbon dioxide refrigerant capable of obtaining an excellent heating action in the gas cooler has been used. In that case, the refrigerant discharged from the gas cooler is expanded in two stages, There has also been developed an apparatus in which a gas-liquid separator is interposed between expansion devices to enable gas injection into a compressor (see, for example, Patent Document 2).

  On the other hand, for example, in an refrigeration system that uses an endothermic action in an evaporator installed in a showcase or the like to cool the interior, the refrigerant temperature at the outlet of the gas cooler is high due to factors such as high outside air temperature (heat source temperature on the gas cooler side). Under higher conditions, the specific enthalpy at the inlet of the evaporator increases, which causes a problem that the refrigerating capacity is remarkably reduced. In such a case, if the discharge pressure (high-pressure side pressure) of the compression means is increased in order to ensure the refrigeration capacity, the compression power increases and the coefficient of performance decreases.

  Therefore, the refrigerant cooled by the gas cooler is divided into two refrigerant streams, one of the divided refrigerant streams is squeezed by the auxiliary throttle means, and then flows into one passage of the split heat exchanger, and the other refrigerant stream is split. A so-called split-cycle refrigeration apparatus has been proposed in which heat is exchanged by flowing through the other flow path of the heat exchanger and then flows into the evaporator via the main throttle means. According to such a refrigeration apparatus, the second refrigerant flow can be cooled by the first refrigerant flow expanded under reduced pressure, and the refrigeration capacity can be improved by reducing the specific enthalpy at the inlet of the evaporator. (For example, refer to Patent Document 3).

Japanese Patent Publication No. 7-18602 JP 2007-178042 A JP 2011-133207 A

  However, particularly in a refrigeration apparatus using a refrigerant such as carbon dioxide, when the outside air temperature rises, the high-pressure side pressure of the refrigerant circuit from which the refrigerant is discharged from the compression means increases, and the operation efficiency of the compression means decreases and the worst. In this case, there is a risk of damaging the compression means. In this case, in a refrigeration apparatus using a refrigerant such as carbon dioxide, the high-pressure side pressure varies greatly depending on the season, so it is difficult to determine an appropriate refrigerant charging amount.

  Further, when the outside air temperature fluctuates, the pressure of the refrigerant flowing into the main throttle means fluctuates greatly, and the control of the main throttle means and the refrigeration capacity become unstable. Furthermore, in a store such as a supermarket, when supplying a refrigerant from a refrigerator equipped with a compression means or a gas cooler to a showcase in a store provided with a main throttle means or an evaporator, the main throttle means on the showcase side Since the high-pressure side pressure is high, it is necessary to use a long refrigerant pipe (liquid pipe) with a high pressure resistance, which is disadvantageous in terms of construction cost.

  Furthermore, when the operation is started in an environment where the outside air temperature is high, the first refrigerant flow is not liquefied in the refrigerant circuit having a high evaporation temperature, and even if the split cycle as described above is configured, the first refrigerant flow The cooling effect of the second refrigerant flow can hardly be expected. For this reason, there is a problem that liquid refrigerant cannot be sent to the main throttle means, the refrigeration capacity is lowered, and as a result, the refrigerant discharge temperature of the compression means is also raised.

  The present invention has been made to solve the conventional technical problem, and when the high pressure side becomes a supercritical pressure, the compression means is protected from an increase in the high pressure side pressure and the like, and the outside air temperature is affected. An object of the present invention is to provide a refrigeration apparatus capable of ensuring a stable refrigeration capacity that is not performed.

In the refrigeration apparatus of the present invention, a refrigerant circuit is constituted by a compression means, a gas cooler, a main throttle means, and an evaporator, and the high pressure side becomes a supercritical pressure, and the downstream side of the gas cooler is the main circuit. A pressure adjusting throttle means connected to the refrigerant circuit upstream of the throttle means; a tank downstream of the pressure adjusting throttle means and connected to the refrigerant circuit upstream of the main throttle means; and the tank The split heat exchanger provided in the refrigerant circuit on the downstream side of the main throttle means and the refrigerant in the tank flow through the auxiliary throttle means to the first flow path of the split heat exchanger. After that, the auxiliary circuit to be sucked into the intermediate pressure part of the compression means and the refrigerant flowed out from the lower part of the tank, flowed to the second flow path of the split heat exchanger, and heat exchanged with the refrigerant flowing through the first flow path. After that, the main circuit to flow into the main throttle means and the pressure And control means for controlling the adjusting throttle means, the control means, by means diaphragm pressure control to adjust the high-pressure side pressure of the refrigerant circuit on the upstream side of the pressure regulating throttle means, the auxiliary diaphragm means, The auxiliary circuit has a first auxiliary circuit throttle means, the auxiliary circuit has a gas pipe that allows the refrigerant to flow out from the upper part of the tank and flow into the first auxiliary circuit throttle means, and the control means has the first auxiliary circuit. The pressure of the refrigerant flowing into the main throttle means is adjusted by the throttle means for use .

  In the refrigeration apparatus according to a second aspect of the present invention, in the above invention, the control means sets the opening degree at the time of starting the pressure adjusting throttle means in such a direction that the higher the outside air temperature is, the higher the outside air temperature is. It is characterized by.

  In the refrigeration apparatus according to a third aspect of the present invention, in each of the above-described inventions, the control means controls the opening degree of the pressure adjusting throttle means to thereby set the high pressure side pressure of the refrigerant circuit upstream of the pressure adjusting throttle means. The target value of the high-pressure side pressure is set in such a direction that the higher the outside air temperature is, the higher the outside air temperature is based on an index representing the outside air temperature.

  In the refrigeration apparatus according to a fourth aspect of the present invention, in each of the above inventions, the control means opens the pressure adjusting throttle means when the high pressure side pressure of the refrigerant circuit upstream of the pressure adjusting throttle means rises to a predetermined upper limit value. It is characterized by increasing the degree.

In the refrigeration apparatus according to a fifth aspect of the present invention, in each of the above inventions, the control means is based on an index representing the outside air temperature, and the opening degree at the start time of the first auxiliary circuit throttle means in a direction of increasing as the outside air temperature increases. Is set.

In the refrigeration apparatus according to a sixth aspect of the present invention, in each of the above-described inventions, the control means controls the opening of the first auxiliary circuit throttle means so that the pressure of the refrigerant flowing into the main throttle means becomes a predetermined target value. In addition to controlling, a target value of the pressure of the refrigerant flowing into the main throttle means is set in a direction to increase the higher the outside air temperature based on the index representing the outside air temperature.

In the refrigeration apparatus according to a seventh aspect of the present invention, in each of the above inventions, the control means increases the opening of the first auxiliary circuit throttle means when the pressure of the refrigerant flowing into the main throttle means rises to a predetermined specified value. It is characterized by making it.

In the refrigeration apparatus according to an eighth aspect of the present invention, in each of the above inventions, the auxiliary throttle means has a second auxiliary circuit throttle means, and the auxiliary circuit causes the refrigerant to flow out from the lower part of the tank, and the second auxiliary circuit throttle. The control means has a liquid pipe to be introduced into the means, the control means controls the opening degree of the second auxiliary circuit throttle means, and adjusts the amount of liquid refrigerant flowing through the first flow path of the split heat exchanger, The discharge temperature of the refrigerant discharged from the compression means to the gas cooler is controlled to a predetermined target value.

According to a ninth aspect of the present invention, in the refrigeration apparatus according to the present invention, the control means changes the target value of the refrigerant discharge temperature in a direction of lowering the higher the evaporation temperature, based on an index representing the evaporation temperature of the refrigerant in the evaporator. It is characterized by doing.

According to a tenth aspect of the present invention, there is provided a refrigeration apparatus comprising an internal heat exchanger for exchanging heat between the refrigerant flowing into the main throttle means and the refrigerant discharged from the evaporator.

The refrigeration apparatus according to an eleventh aspect of the present invention is characterized in that carbon dioxide is used as a refrigerant in each of the above inventions.

According to the present invention, in the refrigerating apparatus in which the refrigerant circuit is configured by the compression unit, the gas cooler, the main throttle unit, and the evaporator, and the high pressure side is the supercritical pressure, the downstream side of the gas cooler and the main throttle unit A pressure adjusting throttle means connected to the upstream refrigerant circuit, a tank downstream of the pressure adjusting throttle means and connected to the refrigerant circuit upstream of the main throttle means, and a downstream side of the tank. The split heat exchanger provided in the refrigerant circuit on the upstream side of the main throttle means and the refrigerant in the tank are passed through the first flow path of the split heat exchanger via the auxiliary throttle means, and then the compression means The auxiliary circuit to be sucked into the intermediate pressure part and the refrigerant flow out from the lower part of the tank, flow into the second flow path of the split heat exchanger, exchange heat with the refrigerant flowing through the first flow path, and then to the main throttle means With a main circuit to flow in The refrigerant flowing in the first flow path of the split heat exchanger constituting the auxiliary circuit is expanded by the auxiliary throttle means, and the refrigerant flowing in the second flow path of the split heat exchanger constituting the main circuit is supercooled. Thus, the specific enthalpy at the evaporator inlet can be reduced to effectively improve the refrigerating capacity. The auxiliary throttle means has a first auxiliary circuit throttle means, and the auxiliary circuit has a gas pipe that causes the refrigerant to flow out from the upper part of the tank and flow into the first auxiliary circuit throttle means. However, since the pressure of the refrigerant flowing into the main throttle means is adjusted by the first auxiliary circuit throttle means, this first auxiliary circuit throttle means suppresses the influence of fluctuations in the high-pressure side pressure. As a result, the pressure of the refrigerant conveyed to the main throttle means can be controlled. Further, by reducing the pressure of the refrigerant flowing into the main throttle means by the first auxiliary circuit throttle means, it is possible to use a pipe having a low pressure resistance as the pipe leading to the main throttle means. Thereby, it becomes possible to improve workability and construction cost. In particular, the pressure in the tank is reduced by extracting low-temperature gas from the upper part of the tank through the first auxiliary circuit throttle means. As a result, the temperature is lowered in the tank, so that the refrigerant condenses, and the liquid refrigerant can be effectively stored in the tank.

  Further, since the refrigerant flowing in the first flow path of the split heat exchanger is returned to the intermediate pressure portion of the compression means, the amount of refrigerant sucked into the low pressure portion of the compression means is reduced, and the refrigerant is compressed from low pressure to intermediate pressure. The amount of compression work in the compression means is reduced. As a result, the compression power in the compression means is reduced and the coefficient of performance is improved.

  Furthermore, a part of the refrigerant liquefied by expansion by the pressure adjusting throttle means evaporates in the tank to become a gas refrigerant having a lowered temperature, and the rest becomes liquid refrigerant and is temporarily stored in the lower part of the tank. It becomes. Then, since the liquid refrigerant in the lower part of the tank flows into the main throttle means through the second flow path of the split heat exchanger constituting the main circuit, the refrigerant is caused to flow into the main throttle means in a full state. In particular, it is possible to improve the refrigerating capacity under refrigeration conditions where the evaporation temperature in the evaporator is high.

  Furthermore, since the tank has the effect of absorbing the fluctuation of the circulating refrigerant amount in the refrigerant circuit, the refrigerant filling amount error is also absorbed.

  Particularly, the control means controls the pressure adjusting throttle means, and the pressure adjusting throttle means adjusts the high pressure side pressure of the refrigerant circuit upstream from the pressure adjusting throttle means. It is possible to avoid the disadvantage that the high pressure side pressure at which the pressure is discharged increases and the operation efficiency of the compression means decreases, or that the compression means is damaged.

  In this case, as in the second aspect of the invention, the control means sets the opening degree at the time of starting the pressure adjusting throttle means in such a direction that the higher the outside air temperature is, the higher the outside air temperature is. It is possible to suppress an increase in the high-pressure side pressure at the time of start-up in a high temperature environment and to protect the compression means.

  The control means controls the high pressure side pressure of the refrigerant circuit upstream of the pressure adjusting throttle means to a predetermined target value by controlling the opening degree of the pressure adjusting throttle means. In addition, by setting the target value of the high-pressure side pressure in the direction of increasing the higher the outside air temperature based on the index representing the outside air temperature, the high-pressure side upstream of the pressure adjusting throttle means in the environment where the outside air temperature is high The target value during pressure operation increases, and the target value decreases in an environment where the outside air temperature is low.

  As a result, the target value increases in a situation where the high pressure side pressure increases due to the influence of a high outside air temperature, so that the opening degree of the pressure adjusting throttle means becomes excessively large and the in-tank pressure is prevented from becoming too high. Will be able to. On the other hand, the target value also decreases in a situation where the high pressure side pressure is low at low outside air temperature, so that the opening of the pressure adjusting throttle means becomes excessively small and the disadvantage that the amount of refrigerant flowing into the tank decreases is prevented. Will be able to.

  As a result, it is possible to appropriately realize both the securing of the refrigerating capacity and the protection of the compression means by appropriately controlling the opening degree of the pressure adjusting throttle means regardless of the change in the outside air temperature accompanying the change of season. It becomes like this.

  Further, when the high pressure side pressure of the refrigerant circuit upstream of the pressure adjusting throttle means rises to a predetermined upper limit value, the control means increases the opening degree of the pressure adjusting throttle means. By doing so, the high pressure side pressure can always be maintained below the upper limit value. As a result, it is possible to reliably suppress the abnormal increase in the high pressure side pressure upstream of the pressure adjusting throttle means and to reliably protect the compression means, and to stop the compression means due to the abnormal high pressure (protection operation). This can be avoided beforehand.

In this case, the control means as the invention of claim 5 is based on an index that represents the outside air temperature, the higher the outside air temperature is high, to set the opening degree at the start of the first auxiliary circuit throttle means at increasing direction Thus, it is possible to suppress an increase in the pressure in the tank at the time of start-up in an environment where the outside air temperature is high, and to prevent an increase in the pressure of the refrigerant flowing into the main throttle means.

According to the sixth aspect of the invention, the control means controls the opening of the first auxiliary circuit throttle means to control the pressure of the refrigerant flowing into the main throttle means to a predetermined target value, and the outside air. If the target value of the pressure of the refrigerant flowing into the main throttle means is set in the direction of increasing the higher the outside air temperature based on the index representing the temperature, the refrigerant flowing into the main throttle means in an environment where the outside air temperature is high The target value becomes higher during the operation of the pressure, and the target value becomes lower in an environment where the outside air temperature is low.

  As a result, in a situation where the pressure increases due to the influence of a high outside air temperature, the target value of the pressure of the refrigerant flowing into the main throttle means becomes high, so the opening degree of the first auxiliary circuit throttle means becomes excessively large. It is possible to prevent the disadvantage that the refrigerant flows excessively in the auxiliary circuit. On the other hand, when the pressure is low at a low outside air temperature, the target value of the pressure of the refrigerant flowing into the main throttle means also becomes low, so the opening degree of the first auxiliary circuit throttle means becomes too small and flows into the auxiliary circuit. This makes it possible to prevent the disadvantage that the amount of refrigerant to be reduced is excessively reduced.

  As a result, the amount of refrigerant flowing through the auxiliary circuit can be accurately adjusted by appropriately controlling the opening degree of the first auxiliary circuit throttle means regardless of the change in the outside air temperature accompanying the change of season. Become.

Further, as in the seventh aspect of the invention, when the control means increases the opening degree of the first auxiliary circuit throttle means when the pressure of the refrigerant flowing into the main throttle means rises to a predetermined specified value. The pressure of the refrigerant conveyed to the main throttle means can always be kept below the specified value, and the effect of suppressing the pressure fluctuation of the high-pressure side and the effect of suppressing the pressure of the refrigerant conveyed to the main throttle means are ensured. Can be achieved.

According to the invention of claim 8 , in addition to each of the above inventions, the auxiliary throttle means has the second auxiliary circuit throttle means, and the auxiliary circuit causes the refrigerant to flow out from the lower part of the tank, and the second auxiliary circuit. A liquid pipe for flowing into the circuit throttle means is provided, and the control means controls the opening degree of the second auxiliary circuit throttle means to adjust the amount of liquid refrigerant flowing through the first flow path of the split heat exchanger. As a result, the discharge temperature of the refrigerant discharged from the compression means to the gas cooler is controlled to a predetermined target value, so that the first flow path of the split heat exchanger passes through the second auxiliary circuit throttle means. It is possible to increase the supercooling of the main circuit refrigerant flowing through the second flow path of the split heat exchanger by flowing the liquid refrigerant in the lower part of the tank.

  Thereby, the liquid phase ratio of the refrigerant conveyed to the main throttle means can be increased and can be made to flow into the main throttle means in a full state. Further, since the temperature of the refrigerant sucked by the compression unit is also lowered, the discharge temperature of the refrigerant discharged from the compression unit to the gas cooler can be lowered to the target value as a result, and the compression unit is reliably protected. Can be achieved.

In this case, as in the ninth aspect of the invention, the control means changes the target value of the refrigerant discharge temperature in the direction of lowering the higher the evaporation temperature, based on the index indicating the evaporation temperature of the refrigerant in the evaporator. By doing so, it is possible to ensure the supercooling of the refrigerant in the main circuit in the split heat exchanger, and to maintain the refrigeration capacity stably, particularly under refrigeration conditions where the evaporation temperature in the evaporator is high.

Further, if an internal heat exchanger for exchanging heat between the refrigerant flowing into the main throttle means and the refrigerant discharged from the evaporator is provided as in the invention of claim 10 , the low temperature discharged from the evaporator by the internal heat exchanger is provided. This makes it possible to cool the refrigerant flowing into the main throttle means, so that the specific enthalpy at the evaporator inlet can be reduced to effectively improve the refrigerating capacity.

  In particular, in a high outside air temperature environment where the outside air temperature is high, there is no pressure difference between the pressure in the tank adjusted by the auxiliary throttle means and the intermediate pressure portion of the compression means. In such a case, depending on the situation, the refrigerant in the main circuit flowing in the second flow path can hardly be supercooled by the refrigerant in the auxiliary circuit flowing in the first flow path in the split heat exchanger. The liquid-rich refrigerant cannot be sent to the means, but even under such circumstances, the refrigerant flowing into the main throttling means is cooled by the low-temperature refrigerant that has exited the evaporator in the internal heat exchanger, and the main throttling means is full. Since it becomes possible to supply the refrigerant, it is possible to improve the refrigerating capacity.

In particular, when carbon dioxide is used as the refrigerant as in the invention of claim 11 , the above-described inventions can effectively improve the refrigerating capacity and improve the performance.

It is a refrigerant circuit figure of the refrigerating device of one example to which the present invention is applied. FIG. 2 is a PH diagram of a combined cycle of a two-stage expansion cycle and a split cycle executed by the control device of the refrigeration apparatus of FIG. 1. FIG. 2 is a PH diagram of a two-stage expansion cycle executed by the control device of the refrigeration apparatus in FIG. 1. FIG. 2 is a PH diagram of a split cycle executed by the control device of the refrigeration apparatus of FIG. 1.

(1) Configuration of Refrigeration Apparatus R Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a refrigerant circuit diagram of a refrigeration apparatus R according to an embodiment to which the present invention is applied. The refrigeration apparatus R in this embodiment is a show of a refrigerator unit 3 installed in a machine room or the like of a store such as a supermarket, and one or a plurality of units (only one is shown in the drawing) installed in the store sales area. 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 so that a predetermined refrigerant circuit 1 is provided. It is composed.

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

  The refrigerator unit 3 includes a compressor 11 as compression means. In this embodiment, the compressor 11 is an internal intermediate pressure type two-stage compression rotary compressor, and includes an airtight container 12, an electric element 13 as a drive element disposed and housed in the upper part of the internal space of the airtight container 12, and the A first (low stage side) rotary compression element (first compression element) 14 and a second (high stage side) rotary compression element (first stage) disposed below the electric element 13 and driven by the rotating shaft thereof. 2 compression elements) 16 and a rotary compression mechanism.

  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 raises it to an intermediate pressure for discharge. The rotary compression element 16 further sucks in the intermediate pressure refrigerant compressed and discharged by the first rotary compression element 14, compresses it to a high pressure, and discharges it to the high pressure side of the refrigerant circuit 1. The compressor 11 is a variable frequency compressor, and the rotational frequency of the first rotary compression element 14 and the second rotary compression element 16 can be controlled by changing the operating frequency of the electric element 13.

  On the side surface of the sealed container 12 of the compressor 11, a low-stage suction port 17 communicating with the first rotary compression element 14, a low-stage discharge port 18 communicating with the inside of the sealed container 12, and a second rotational compression A high-stage suction port 19 and a high-stage discharge port 21 communicating with the element 16 are formed. One end of the refrigerant introduction pipe 22 is connected to the lower stage side suction port 17 of the compressor 11, and the other end is connected to the refrigerant pipe 9 at the unit inlet 7. A second flow path 15B of the internal heat exchanger 15 is interposed in the refrigerant introduction pipe 22.

  The low-pressure refrigerant gas (LP: about 2.6 MPa in the normal operation state) sucked into the low-pressure portion of the first rotary compression element 14 from the low-stage suction port 17 is intermediate pressure by the first rotary compression element 14. The pressure is increased to (MP: about 5.5 MPa in a normal operation state) and discharged into the sealed container 12. Thereby, the inside of the airtight container 12 becomes an intermediate pressure (MP).

  One end of the 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 in the sealed container 12 is discharged, and the other end is connected to the inlet of the intercooler 24. Has been. The intercooler 24 air-cools the intermediate pressure refrigerant discharged from the first rotary compression element 14, and one end of an intermediate pressure suction pipe 26 is connected to the outlet of the intercooler 24. The other end of the pressure suction pipe 26 is connected to the higher 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 side suction port 19 is compressed in the second stage by the second rotary compression element 16 to generate a high temperature and high pressure (HP). : Supercritical pressure of about 9 MPa in a normal operation state).

  One end of a high-pressure discharge pipe 27 is connected to the 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 is a gas cooler (heat radiator) 28. Connected to the entrance. An oil separator 20 is provided in the high-pressure discharge pipe 27. The oil separator 20 separates the oil in the refrigerant discharged from the compressor 11 and returns it to the sealed container 12 of the compressor 11 through the oil passage 25A and the electric valve 25B. Reference numeral 55 denotes a float switch for detecting the oil level in the compressor 11.

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

  One end of a gas cooler outlet pipe 32 is connected to the 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 as a pressure adjusting throttle means. The electric expansion valve 33 is used to squeeze and expand the refrigerant discharged from the gas cooler 28 and to adjust the high-pressure side pressure of the refrigerant circuit 1 upstream from the electric expansion valve 33, and the outlet thereof is a tank inlet pipe 34. It is connected to the upper part of the tank 36 via.

  The tank 36 is a volume body having a predetermined volume space inside, and one end of a tank outlet pipe 37 is connected to the lower part 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. Has been. A second flow path 29B of the split heat exchanger 29 is interposed in the tank outlet pipe 37, and in the tank outlet pipe 37 downstream of the split heat exchanger 29, the internal heat exchanger 15 is connected. A first flow path 15A is interposed. This tank outlet pipe 37 constitutes a main circuit 38 in the present invention. Furthermore, a bypass circuit 45 is connected in parallel to the first flow path 15A of the internal heat exchanger 15, and an electromagnetic valve 50 as a valve device is interposed in the bypass circuit 45.

  On the other hand, the showcase 4 installed in the store is connected to the refrigerant pipes 8 and 9. The showcase 4 is provided with an electric expansion valve 39 and an evaporator 41 as main throttle means, 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 8). Side, the evaporator 41 is the refrigerant pipe 9 side). The evaporator 41 is provided with a cool air circulation blower (not shown) that blows air to the evaporator 41. 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 the upper portion of the tank 36, and the other end of the gas pipe 42 is connected to an inlet of an electric expansion valve 43 as a first auxiliary circuit throttle means. The gas pipe 42 causes the gas refrigerant to flow out from the upper portion of the tank 36 and to flow into the electric expansion valve 43. One end of the intermediate pressure return pipe 44 is connected to the outlet of the electric expansion valve 43, and the other end is connected to the middle pressure suction pipe 26 as an example of an intermediate pressure region connected to the intermediate pressure portion of the compressor 11. Yes. A first flow path 29 A of the split heat exchanger 29 is interposed in the intermediate pressure return pipe 44.

  One end of a liquid pipe 46 is connected to the lower part of the tank 36, and the other end of the liquid pipe 46 is connected to an intermediate pressure return pipe 44 on the downstream side of the electric expansion valve 43. Further, an electric expansion valve 47 as a second auxiliary circuit throttle means is interposed in the liquid pipe 46. The electric expansion valve 43 (first auxiliary circuit throttle means) and the electric expansion valve 47 (second auxiliary circuit throttle means) constitute auxiliary throttle means in the present application. Further, the liquid pipe 46 causes liquid refrigerant to flow out from the lower portion of the tank 36 and to flow into the electric expansion valve 47. The intermediate pressure return pipe 44, the electric expansion valves 43 and 47, and the gas pipe 42 and the liquid pipe 46 on the upstream side of the electric expansion valves 43 and 47 constitute an auxiliary circuit 48 in the present invention.

  With such a configuration, 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. Furthermore, the split heat exchanger 29 is positioned downstream of the tank 36 and upstream of the electric expansion valve 39, and the refrigerant circuit 1 of the refrigeration apparatus R in this embodiment is configured as described above.

  Various sensors are attached to various portions of the refrigerant circuit 1. That is, a high pressure sensor 49 is attached to the high pressure discharge pipe 27, and the high pressure side pressure HP of the refrigerant circuit 1 (the high pressure side discharge port 21 of the compressor 11, which is the pressure of the refrigerant discharged from the compressor 11 to the gas cooler 28). The pressure between the inlets of the electric expansion valve 33 is detected. A low pressure sensor 51 is attached to the refrigerant introduction pipe 22 to detect a low pressure LP of the refrigerant circuit 1 (pressure between the outlet of the electric expansion valve 39 and the low stage suction port 17). Further, an intermediate pressure sensor 52 is attached to the intermediate pressure suction pipe 26, and an intermediate pressure MP (the pressure between the inside of the hermetic container 12 and the high-stage side suction port 19, between the electric expansion valve and the intermediate pressure region 1 of the refrigerant circuit). The pressure in the intermediate pressure return pipe 44 after the outlets 43 and 47) is detected.

  A unit outlet sensor 53 is attached to the tank outlet pipe 37 on the downstream side of the split heat exchanger 29, and this unit outlet sensor 53 detects the pressure TP in the tank 36. That is, the pressure in the tank 36 becomes 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. A unit outlet temperature sensor 54 is attached to the tank outlet pipe 37 on the upstream side of the internal heat exchanger 15 to detect the temperature IT of the refrigerant flowing into the first flow path 15A of the internal heat exchanger 15. Further, a unit inlet temperature sensor 56 is attached to the refrigerant introduction pipe 22 on the downstream side of the internal heat exchanger 15, and detects the temperature OT of the refrigerant that has exited the second flow path 15B of the internal heat exchanger 15. Furthermore, a discharge temperature sensor 61 is attached to the high-pressure discharge pipe 27 connected to the high-stage discharge port 21 of the compressor 11 to detect the temperature (discharge temperature) of the refrigerant discharged from the compressor 11 to the gas cooler 29. To do.

  These sensors 49, 51, 52, 53, 54, 56, 61 are connected to the input of the control device 57 constituting the control means of the refrigerator unit 3 composed of a microcomputer, and the float switch 55 is also connected to the control device 57. Connected to the input. The output of the control device 57 includes an electric element 13 of the compressor 11, an electric valve 25B, a gas cooler blower 31, an electric expansion valve (pressure adjusting throttle means) 33, an electric expansion valve (first auxiliary circuit throttle means). ) 43, an electric expansion valve (second auxiliary circuit throttle means) 47, an electromagnetic valve 50, and an electric expansion valve (main throttle means) 39 are connected, and the control device 57 is based on the output of each sensor, setting data, etc. Control these.

  In the following description, it is assumed that the control device 57 controls the electric expansion valve (main throttle means) 38 on the showcase 4 side and the above-mentioned cool air circulation blower. Through a control device (not shown) on the side of the showcase 4 that operates in cooperation with the control device 57. Therefore, the control means in the present invention has 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 Apparatus R Next, the operation of the refrigeration apparatus R with the above configuration 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 is rotated from the low-stage suction port 17. The refrigerant gas (carbon dioxide) having a low pressure (LP: about 2.6 MPa in a normal operation state) is sucked into the low pressure portion. Then, the pressure is increased to an intermediate pressure (MP described above: about 5.5 MPa in the normal operation state) by the first rotary compression element 14 and discharged into the sealed container 12. Thereby, the inside of the airtight container 12 becomes an intermediate pressure (MP).

  Then, the intermediate-pressure refrigerant gas in the sealed container 12 enters the intercooler 24 from the low-stage discharge port 18 through the intermediate-pressure discharge pipe 23, and is then air-cooled there, and then through the intermediate-pressure suction pipe 26 to the high-stage suction. Return to mouth 19. The intermediate pressure (MP) refrigerant gas that has returned to the high-stage suction port 19 is sucked into the second rotary compression element 16, and the second stage compression is performed by the second rotary compression element 16, resulting in a high temperature. The refrigerant gas becomes high-pressure (HP: supercritical pressure of about 9 MPa in the above-described normal operation state) and is discharged from the high-stage discharge port 21 to the high-pressure discharge pipe 27.

  The refrigerant gas discharged to the high-pressure discharge pipe 27 flows into the oil separator 20, and the oil contained in the refrigerant is separated. The separated oil passes through the oil passage 25A, and is returned to the hermetic container 12 through the electric valve 25B. The control device 57 controls the motor-operated valve 25B based on the oil level in the sealed container 12 detected by the float switch 55, and adjusts the return amount of oil to maintain the oil level in the sealed container 12.

(2-1) Control of Electric Expansion Valve 33 On the other hand, the refrigerant gas from which the oil has been separated by the oil separator 20 flows into the gas cooler 28 and is air-cooled, and then passes through the gas cooler outlet pipe 32 and then the electric expansion valve (pressure). Adjustment throttling means) 33. The electric expansion valve 33 is provided to control the high-pressure side pressure HP of the refrigerant circuit 1 upstream of the electric expansion valve 33 to a predetermined target value THP (for example, 9 MPa as described above, set as described later). The valve opening degree is controlled by the control device 57 based on the output of the high pressure sensor 49.

(2-1-1) Setting of the opening degree at the start of the electric expansion valve 33 Here, first, the control device 57 is based on the detected pressure (high pressure side pressure HP) of the high pressure sensor 49 which is an index indicating the outside air temperature. The opening of the electric expansion valve 33 at the start of R (starting opening) is set. 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 controller 57 can determine the outside temperature from the high pressure side pressure HP. In the case of the embodiment, the control device 57 has in advance a data table showing the relationship between the high-pressure side pressure HP (outside air temperature) at the time of starting and the opening degree of the electric expansion valve 33 at the time of starting. The outside air temperature is estimated, and the electric pressure increases in proportion to the higher high pressure side pressure HP (outside air temperature) based on the above data table, and conversely decreases as the high pressure side pressure HP decreases (set in the data table). The opening degree of the expansion valve 33 when starting is set.

  This suppresses the high pressure side pressure HP of the refrigerant circuit 1 upstream of the electric expansion valve 33 from abnormally rising when the compressor 11 is started (starting of the refrigeration apparatus R) in an environment where the outside air temperature is high. As a result, the compressor 11 can be protected. Further, the high pressure side pressure HP of the compressor 11 increases particularly at the time of starting. For this reason, a protective operation for forcibly stopping the compressor 11 at a predetermined high value (abnormally high pressure) is provided. By setting the opening degree of the electric expansion valve 33 as described above, Stopping can also be suppressed or prevented.

  In the embodiment, the controller 57 estimates the outside air temperature from the high pressure side pressure HP detected by the high pressure sensor 49. However, the present invention is not limited to this, and a separate outside temperature sensor is provided to directly detect the outside air temperature. It is good (hereinafter the same).

(2-1-2) Setting of the target value THP of the high pressure side pressure HP during operation Further, the control device 57 is based on the detected pressure (high pressure side pressure HP) of the high pressure sensor 49 which is an index indicating the outside air temperature as described above. To set the target value THP described above. In this case, the control device 57 sets the target value THP in such a direction that the higher the high-pressure side pressure HP (outside air temperature), the higher the pressure, and vice versa. In this case, the standard value of the target value THP of the high pressure side pressure HP is 9 MPa as described above. The control device 57 calculates the adjustment value (number of steps) of the valve opening of the electric expansion valve 33 from the difference between the high pressure side pressure HP detected by the high pressure sensor 49 and the target value THP, and adds it to the valve opening at the time of starting described above. Thus, the electric expansion valve 33 is controlled. Thereby, the high pressure side pressure HP is controlled to the target value THP.

  In this case as well, a preset data table may be used, or may be calculated from a calculation formula. However, when the control is difficult, it is preferable to directly take in the outside temperature using the outside temperature sensor as described above.

  As a result, the target value THP during operation of the high-pressure side pressure HP upstream from the electric expansion valve 33 is high in an environment where the outside air temperature is high, and the target value THP is low in an environment where the outside air temperature is low. That is, since the target value THP increases in a situation where the high pressure side pressure HP increases due to the influence of a high outside air temperature, the valve opening degree of the electric expansion valve 33 becomes excessively large and the pressure in the tank 36 becomes too high. Can be prevented. Conversely, in a situation where the high pressure side pressure HP is low at a low outside air temperature, the target value THP is also low, so that the valve opening degree of the electric expansion valve 33 becomes excessively small and the amount of refrigerant flowing into the tank 36 is reduced. Can be prevented.

  Then, regardless of the change in the outside air temperature due to the change of season, the valve opening degree of the electric expansion valve 33 is appropriately controlled, and both the securing of the refrigeration capacity of the refrigeration apparatus R and the protection of the compressor 11 are suitably performed. Can be realized.

(2-1-3) Control with the upper limit value MHP of the high pressure side pressure HP When the control is performed as described above, the high pressure side pressure upstream of the electric expansion valve 33 due to the influence of the installation environment and load. When HP has increased to a predetermined upper limit value MHP (for example, 11 MPa or the like), the control device 57 increases the valve opening of the electric expansion valve 33 by a predetermined step. As the valve opening increases, the high-pressure side pressure HP tends to decrease, so that the high-pressure side pressure HP can always be kept below the upper limit value MHP. As a result, it is possible to reliably suppress the abnormal increase in the high-pressure side pressure HP upstream from the electric expansion valve 33 and reliably protect the compressor 11, and forcibly stop the compressor 11 due to the abnormal high pressure. (Protection operation) can be avoided in advance.

  The supercritical refrigerant gas emitted from the gas cooler 28 is liquefied by being throttled and expanded by the electric expansion valve 33, and flows into the tank 36 from the upper part via the tank inlet pipe 34, and a part thereof is evaporated. To do. The tank 36 temporarily stores and separates the liquid / gas refrigerant that has exited the electric expansion valve 33 and the high-pressure side pressure of the refrigeration apparatus R (in this case, the high-pressure discharge of the compressor 11 upstream of the tank 36). It plays a role of absorbing pressure changes in the region up to the pipe 27) and fluctuations in the refrigerant circulation rate. The liquid refrigerant accumulated in the lower part of the tank 36 flows out of the tank outlet pipe 37 (main circuit 38), and the first flow path 29A (as will be described later) in the second flow path 29B of the split heat exchanger 29. After being cooled (supercooled) by the refrigerant flowing through the auxiliary circuit 48), it is further cooled by the refrigerant flowing through the second flow path 15B in the first flow path 15A of the internal heat exchanger 15, and then the refrigerator unit. 3 and flows into the electric expansion valve (main throttle means) 39 from the refrigerant pipe 8. The operation of the electromagnetic valve 50 will be described later.

  The refrigerant that has flowed into the electric expansion valve 39 is squeezed there and expanded to further increase the liquid content, and flow into the evaporator 41 to evaporate. The cooling effect is exhibited by the endothermic action. The control device 57 controls the valve opening degree of the electric expansion valve 39 based on the output of a temperature sensor (not shown) that detects the temperatures of the inlet side and the outlet side of the evaporator 41 and sets the superheat degree of the refrigerant in the evaporator 41 to an appropriate value. Adjust to. The low-temperature gas refrigerant discharged from the evaporator 41 returns to the refrigerator unit 3 from the refrigerant pipe 9, and after cooling the refrigerant flowing through the first flow path 15A with the second flow path 15B of the internal heat exchanger 15, the refrigerant The air is sucked into the low-stage suction port 17 communicating with the first rotary compression element 14 of the compressor 11 through the introduction pipe 22. The above is the flow of the main circuit 38.

(2-2) Control of Electric Expansion Valve 43 Next, the flow of the auxiliary circuit 48 will be described. As described above, an electric expansion valve 43 (first auxiliary circuit throttle means) is connected to the gas pipe 42 connected to the upper portion of the tank 36, and the gas refrigerant is supplied from the upper portion of the tank 36 through the electric expansion valve 43. Flows out and flows into the first flow path 29A of the split heat exchanger 29.

  The temperature of the gas refrigerant that accumulates in the upper part of the tank 36 is reduced by evaporation in the tank 36. The gas refrigerant in the upper part of the tank 36 flows out from the gas pipe 42 constituting the auxiliary circuit 48 connected to the upper part, is throttled through the electric expansion valve 43, and then the first flow path of the split heat exchanger 29. Flows into 29A. Therefore, after the refrigerant flowing through the second flow path 29B is cooled, it joins the intermediate pressure suction pipe 26 via the intermediate pressure return pipe 44 and is sucked into the intermediate pressure portion of the compressor 11.

  The electric expansion valve 43 has a function 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 from the upper portion of the tank 36. Fulfill. The control device 57 controls the valve opening degree of the electric expansion valve 43 based on the output of the unit outlet sensor 53. This is because if the valve opening degree 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 embodiment, the target value SP is set to be lower than the high pressure side pressure HP and higher than the intermediate pressure MP, for example, 6 MPa. Then, the controller 57 adjusts the valve opening degree of the electric expansion valve 39 from the difference between the pressure TIP in the tank 36 detected by the unit outlet sensor 53 (pressure of the refrigerant flowing into the electric expansion valve 39) and the target value SP ( The number of steps) is calculated and added to the valve opening at the time of starting to be described later, and the pressure TIP in the tank 36 (pressure of the refrigerant flowing into the electric expansion valve 39) is controlled to the target value SP. That is, when the pressure TIP in the tank 36 rises above the target value SP, the valve opening degree of the electric expansion valve 43 is increased so that the gas refrigerant flows out of the tank 36 into the gas pipe 42, and conversely from the target value SP. When it descends, the valve opening is reduced and controlled to close.

(2-2-1) Setting of the opening degree at the start of the electric expansion valve 43 Here, the control device 57 detects the pressure detected by the high-pressure sensor 49 (high-pressure side pressure HP), which is an index indicating the outside air temperature, or the outside air as described above. In the case where a temperature sensor is provided, the valve opening degree (starting opening degree) of the electric expansion valve 43 when starting the refrigeration apparatus R is set based on the directly detected outside air temperature). In the case of the embodiment, as described above, the control device 57 has in advance a data table indicating the relationship between the high-pressure side pressure HP (outside air temperature) at the time of starting and the valve opening degree at the time of starting the electric expansion valve 43.

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

  In the embodiment, as described above, the target value SP of the pressure TIP in the tank 36 (pressure of the refrigerant flowing into the electric expansion valve 39) is fixed to 6 MPa, but in the case of the electric expansion valve 33, Similarly to the above, the target value SP may be set based on the detected pressure (high pressure side pressure HP) of the high pressure sensor 49 which is an index indicating the outside air temperature. In this case, the target value SP is set in such a direction that the higher the high pressure side pressure HP (outside air temperature) is, the lower the pressure is higher.

  Therefore, in an environment where the outside air temperature is high, the target value SP during operation of the pressure of the refrigerant flowing into the electric expansion valve 39 is high, and in an environment where the outside air temperature is low, the target value SP is low. In other words, in a situation where the pressure increases due to the influence of a high outside air temperature, the target value SP of the pressure of the refrigerant flowing into the electric expansion valve 39 increases, so that the valve opening degree of the electric expansion valve 43 becomes excessively large and the auxiliary circuit Thus, it is possible to prevent inconvenience of excessive flow of the refrigerant to the 48. On the other hand, when the pressure is low at a low outside air temperature, the target value SP of the pressure of the refrigerant flowing into the electric expansion valve 39 is also low, so that the valve opening degree of the electric expansion valve 43 becomes too small and flows into the auxiliary circuit 48. This makes it possible to prevent the disadvantage that the amount of refrigerant to be reduced is excessively reduced. As a result, the amount of refrigerant flowing in the auxiliary circuit 48 can be accurately adjusted by appropriately controlling the valve opening degree of the electric expansion valve 43 regardless of the change in the outside air temperature accompanying the change in season.

(2-2-2) Control of tank internal pressure TIP with specified value MTIP Note that when the control is performed as described above, the internal pressure TIP (electric expansion valve 39 in the electric expansion valve 39) is affected by the installation environment and load. When the pressure of the refrigerant flowing in) increases to a predetermined specified value MTIP (for example, 7 MPa or the like), the control device 57 increases the valve opening degree of the electric expansion valve 43 by a predetermined step. As the valve opening increases, the pressure TIP in the tank 36 tends to decrease, so that the pressure TIP can always be maintained below the specified value MTIP. It becomes possible to reliably achieve the effect of suppressing the pressure of the refrigerant conveyed to the valve 39.

(2-3) Control of the electric expansion valve 47 The electric expansion valve 47 (second auxiliary circuit throttle means) is connected to the liquid pipe 46 connected to the lower portion of the tank 36 as described above. The liquid refrigerant flows out from the lower portion of the tank 36 via the electric expansion valve 47, merges with the gas refrigerant from the gas pipe 42, and flows into the first flow path 29 </ b> A of the split heat exchanger 29.

  That is, the liquid refrigerant that accumulates in the lower part of the tank 36 flows out from the liquid pipe 46 that constitutes the auxiliary circuit 48 connected to the lower part, is throttled through the electric expansion valve 47, and then the first of the split heat exchanger 29. It flows into the flow path 29A and evaporates there. The heat absorption at this time increases the supercooling of the refrigerant flowing through the second flow path 29B, and then merges with the intermediate pressure suction pipe 26 via the intermediate pressure return pipe 44 and sucks into the intermediate pressure portion of the compressor 11. It is.

  In this way, the electric expansion valve 47 throttles the liquid refrigerant flowing out from the lower part of the tank 36, evaporates it in the first flow path 29A of the split heat exchanger 29, and the refrigerant of the main circuit 38 that flows into the second flow path 29B. The control device 57 adjusts the amount of liquid refrigerant flowing through the first flow path 29A of the split heat exchanger 29 by controlling the valve opening degree of the electric expansion valve 47.

  When the amount of supercooling of the refrigerant in the main circuit 38 in the split heat exchanger 29 increases, the liquid phase ratio of the refrigerant conveyed to the electric expansion valve 39 increases, so that the electric expansion valve 39 has a full refrigerant. Will flow in, and the temperature of the refrigerant sucked by the compressor 11 will also decrease. As a result, the discharge temperature of the refrigerant discharged from the compressor 11 to the gas cooler 28 also decreases.

  Therefore, the control device 57 controls the opening degree 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 61, thereby performing split heat exchange. The amount of liquid refrigerant flowing through the first flow path of the vessel 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 opening degree of the electric expansion valve 47 is increased, and when the actual discharge temperature is lower, the opening is reduced. Thereby, the discharge temperature of the refrigerant of the compressor 11 is maintained at the target value TDT, and the compressor 11 is protected.

  In that case, based on the detected pressure (low pressure side pressure LP) of the low pressure sensor 51, which is an index indicating the refrigerant evaporation temperature in the evaporator 41, the control device 57 lowers and lowers the lower pressure LP (evaporation temperature). The target value TDT of the refrigerant discharge temperature of the compressor 11 is changed in such a direction as to increase it. For example, when the evaporation temperature is lower than −20 ° C., the target value TDT is set to + 70 ° C., and when the evaporation temperature is −20 ° C. or higher, the target value TDT is changed to + 100 ° C.

  This ensures supercooling of the refrigerant in the main circuit 38 in the second flow path 29B of the split heat exchanger 29, particularly under refrigeration conditions (such as a refrigeration showcase) where the evaporation temperature in the evaporator 41 is high, and refrigerating capacity is increased. It can be maintained stably.

(2-4) Actual Operation of Refrigeration Apparatus R for Each Outside Air Temperature Next, the actual operation status of the refrigeration apparatus R will be described for each outside air temperature with reference to the PH diagrams of FIGS.

(2-4-1) Interim period FIG. 2 shows an intermediate period environment where the outside air temperature is about + 25 ° C., for example. As described above, the control device 57 controls the valve opening degree of the electric expansion valve 33 to control the high pressure side pressure HP upstream from the electronic expansion valve 33 to the target value THP. To adjust the amount of the gas refrigerant flowing out from the gas pipe 42, and the pressure TIP in the tank 36 (the pressure of the refrigerant flowing into the electric expansion valve 39) is controlled to the target value SP. Further, the valve opening degree of the electric expansion valve 47 is controlled to adjust the amount of liquid refrigerant flowing out from the liquid pipe 46, and the refrigerant discharge temperature of the compressor 11 is adjusted to the target value TDT.

  A line descending from X1 to X2 in FIG. The pressure of X2 (pressure TIP in the tank 36) is adjusted to the target value SP by the electric expansion valve 43. The liquid / gas is separated from the tank 36 at X2, and the line from X2 to the left indicates the supercooling of the liquid refrigerant toward the electric expansion valve 39 of the main circuit 38. Similarly, the electric expansion valve 39 throttles the pressure at X3 and the pressure drops (the same applies to FIG. 3).

  Since the intermediate pressure MP becomes low in the intermediate period, there is a difference from the pressure TIP in the tank 36 adjusted by the electric expansion valve 43. As a result, the split heat exchanger 29 can secure a heat exchange amount necessary for the supercooling of the refrigerant in the main circuit 38, so that the refrigerant circuit 1 has a two-stage expansion cycle and a so-called split cycle combined cycle. Become.

(2-4-2) At high outdoor temperatures (summer, etc.)
FIG. 3 shows a case where the outside air temperature is an environment (summer season or the like) where the outside air temperature is + 30 ° C. or higher. At such a high outside air temperature, the intermediate pressure MP becomes high and there is no difference from the pressure TIP in the tank 36. Therefore, the heat exchange amount in the split heat exchanger 29 is reduced, and the refrigerant of the main circuit 38 is reduced. Overcooling cannot be secured. Further, since the high-pressure side pressure HP tends to increase, the valve opening of the electric expansion valve 33 is increased from that in the intermediate period in order to suppress it (control by the control device 57).

  Therefore, the amount of refrigerant flowing into the tank 36 increases, but the control device 57 controls the valve of the electric expansion valve 43 in order to suppress an increase in the pressure TIP (pressure of the refrigerant flowing into the electric expansion valve 39) in the tank 36. Increase the opening. For this reason, the amount of refrigerant returned to the intermediate pressure portion (intermediate pressure suction pipe 26) of the compressor 11 increases, so that the intermediate pressure MP increases. Therefore, the refrigerant subcooling effect of the main circuit 38 in the split heat exchanger 29 is reduced, and the refrigerant circuit 1 becomes a so-called two-stage expansion cycle.

  An internal heat exchanger 15 is provided to compensate for a decrease in the heat exchange amount in the split heat exchanger 29, which will be described later.

(2-4-3) At low outside temperatures (winter etc.)
Next, FIG. 4 shows a time when the outside air temperature is lowered to + 20 ° C. or lower (in winter). At such a low outside air temperature, the high pressure side pressure HP is low, but the target value THP is also low as described above, so that the valve opening degree of the electric expansion valve 33 is almost fully open. Therefore, the pressure TIP in the tank 36 becomes a pressure close to the high-pressure side pressure HP, and the effect of the tank 36 is reduced. However, the refrigerant that has exited the gas cooler 28 is liable to be liquefied due to the low outside air temperature. The refrigerant that has entered the tank 36 via the valve 33 is almost liquefied, and a large amount of liquid refrigerant is stored in the tank 36.

  Therefore, since the liquid refrigerant is throttled in the electric expansion valves 43 and 47 and evaporates in the first flow path 29A of the split heat exchanger 29, the effect of the split heat exchanger 29 increases, and the main circuit 38 The refrigerant in the (second flow path 29B) can be supercooled, and the refrigerant circuit 1 enters a split cycle.

(2-5) Function of Internal Heat Exchanger 15 Next, control of the electromagnetic valve 50 by the control device 57 will be described. As described above, in the internal heat exchanger 15, the refrigerant flowing through the first flow path 15A and flowing into the main throttle means 39 is cooled by the low-temperature refrigerant discharged from the evaporator 41 flowing through the second flow path 15B. Therefore, the specific enthalpy at the inlet of the evaporator 41 can be further reduced to improve the refrigerating capacity more effectively.

  In particular, in a high outside air temperature environment where the outside air temperature is high as shown in FIG. 3, as described above, the pressure TIP (pressure X2 in FIG. 3) in the tank 36 adjusted to the target value SP by the electric expansion valve 43, The pressure difference from the intermediate pressure (MP) of the intermediate pressure suction pipe 26 entering the compressor 11 disappears. In such a case, since the valve opening degree of the electric expansion valve 43 increases as described above, depending on the situation, the second flow is caused by the refrigerant in the auxiliary circuit 49 flowing through the first flow path 29A in the split heat exchanger 29. The refrigerant in the main circuit 38 flowing through the path 29B can hardly be supercooled.

  In such a situation, the state of the refrigerant that reaches the electric expansion valve 39 through the second flow path 29B of the split heat exchanger 29 is substantially on the saturated liquid line indicated by X3 in FIG. It becomes. Therefore, the pressure of the refrigerant throttled by the electric expansion valve 39 falls from X3 in FIG. In this case, the enthalpy difference indicated by the lower side is reduced, and the refrigerating capacity is reduced.

  However, in the embodiment, the refrigerant flowing into the electric expansion valve 39 is cooled by the low-temperature refrigerant discharged from the evaporator 41 in the internal heat exchanger 15, and the supercooling on the left side of the saturated liquid line as shown by the broken line in FIG. Since the refrigerant can be supercooled to the region (indicated by X4), the refrigerant can be supplied to the electric expansion valve 39 in a liquid-rich full state, and the refrigeration capacity can be improved even in such a situation. It becomes possible.

(2-6) Control of Electromagnetic Valve 50 On the other hand, when the refrigeration apparatus R is pulled down, the temperature of the refrigerant exiting the evaporator 41 may be higher than the refrigerant flowing into the electric expansion valve 39. Therefore, the control device 57 detects the temperature IT of the refrigerant flowing into the first flow path 15A of the internal heat exchanger 15 detected by the unit outlet temperature sensor 54 and the first temperature of the internal heat exchanger 15 detected by the unit inlet temperature sensor 56. Based on the temperature OT of the refrigerant exiting the second flow path 15B, when IT <OT, the electromagnetic valve 50 is opened (when IT ≧ OT, the electromagnetic valve 50 is closed).

  As a result, the refrigerant bypasses the first flow path 15A of the internal heat exchanger 15 and flows between the bypasses 45 and flows into the electric expansion valve 39. Therefore, the electric expansion valve 39 is supplied with the refrigerant from the evaporator 41. It is possible to eliminate the inconvenience that the refrigerant flowing into the tank is heated in reverse.

  In the embodiment, the bypass circuit 45 is connected in parallel to the first flow path 15A of the internal heat exchanger 15. However, the present invention is not limited thereto, and a bypass circuit and an electromagnetic valve may be provided in parallel to the second flow path 15B. Good.

  As described in detail above, in the present invention, the electric expansion valve 33 connected to the refrigerant circuit 1 downstream of the gas cooler 28 and upstream of the electric expansion valve 39, and downstream of the electric expansion valve 33. A tank 36 connected to the refrigerant circuit 1 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; An auxiliary circuit 48 that causes the refrigerant in 36 to flow into the first flow path 29A of the split heat exchanger 29 via the electric expansion valve 43 and the electric expansion valve 47 and then sucked into the intermediate pressure portion of the compressor 11; A main circuit 38 that causes the refrigerant to flow out from the lower portion of the tank 36, flows into the second flow path 29B of the split heat exchanger 29, exchanges heat with the refrigerant flowing through the first flow path 29A, and then flows into the electric expansion valve 39. It is equipped with auxiliary times The refrigerant flowing in the first flow path 29A of the split heat exchanger 29 constituting 48 is expanded by the electric expansion valves 43 and 47, and flows to the second flow path 29B of the split heat exchanger 29 constituting the main circuit 38. The refrigerant can be supercooled, and the specific enthalpy at the inlet of the evaporator 41 can be reduced to effectively improve the refrigerating capacity.

  Further, since the refrigerant flowing through the first flow path 29A of the split heat exchanger 29 is returned to the intermediate pressure portion of the compressor 11, the amount of refrigerant sucked into the low pressure portion of the compressor 11 is reduced, and from low pressure to intermediate pressure. The amount of compression work in the compressor 11 for compression is reduced. As a result, the compression power in the compressor 11 is reduced and the coefficient of performance is improved.

  Further, a part of the refrigerant liquefied by expansion by the electric expansion valve 33 evaporates in the tank 6 to become a gas refrigerant having a lowered temperature, and the rest becomes liquid refrigerant and is temporarily stored in the lower part of the tank 36. It becomes a shape. The liquid refrigerant in the lower part of the tank 36 flows into the electric expansion valve 39 through the second flow path 29B of the split heat exchanger 29 constituting the main circuit 38. It becomes possible to allow the refrigerant to flow into 39, and it is possible to improve the refrigerating capacity especially under refrigeration conditions where the evaporation temperature in the evaporator 41 is high. Furthermore, since the tank 36 has the effect of absorbing the fluctuation of the circulating refrigerant amount in the refrigerant circuit 1, the refrigerant filling amount error is also absorbed.

  In particular, since the electric expansion valve 33 is controlled by the control device 57 and the high pressure side pressure HP of the refrigerant circuit 1 upstream of the electric expansion valve 33 is adjusted by the electric expansion valve 33, the compressor 11 The high-pressure side pressure HP at which the refrigerant is discharged becomes high, so that the operation efficiency of the compressor 11 is lowered, or the inconvenience of causing damage to the compressor 11 can be avoided.

  In this case, the control device 57 sets the opening degree at the start of the electric expansion valve 33 in a direction that increases as the outside air temperature increases based on the index representing the outside air temperature. The increase in the high-pressure side pressure HP can be suppressed, and the compressor 11 can be protected.

  Further, the control device 57 controls the valve opening degree of the electric expansion valve 33 to control the high-pressure side pressure HP of the refrigerant circuit 1 upstream of the electric expansion valve 33 to a predetermined target value THP, and the outside air temperature. Since the target value THP of the high-pressure side pressure HP is set in the direction of increasing the higher the outside air temperature based on the index representing the pressure, the high-pressure side pressure HP upstream of the electric expansion valve 33 is being operated in an environment where the outside air temperature is high. The target value THP becomes low and the target value THP becomes low in an environment where the outside air temperature is low.

  As a result, the target value THP increases in a situation where the high-pressure side pressure HP increases due to the influence of a high outside air temperature, so that the valve opening degree of the electric expansion valve 33 becomes excessively large and the pressure in the tank 36 becomes too high. Can be prevented. Conversely, in a situation where the high pressure side pressure HP is low at a low outside air temperature, the target value THP is also low, so that the valve opening degree of the electric expansion valve 33 becomes excessively small and the amount of refrigerant flowing into the tank 36 is reduced. Can be prevented.

  As a result, it is possible to appropriately realize both the securing of the refrigerating capacity and the protection of the compressor 11 by appropriately controlling the opening degree of the electric expansion valve 33 regardless of the change in the outside air temperature accompanying the change in season. It becomes like this.

  Further, when the high pressure side pressure HP of the refrigerant circuit 1 upstream of the electric expansion valve 33 is increased to a predetermined upper limit value MHP, the control device 57 increases the valve opening degree of the electric expansion valve 33, so that the high pressure side pressure HP is increased. Can always be kept below the upper limit value MHP. As a result, the compressor 11 can be reliably protected by accurately suppressing an abnormal increase in the high-pressure side pressure HP upstream from the electric expansion valve 33, and the compressor 11 can be stopped (protective operation) due to an abnormal high pressure. ) Can be avoided in advance.

  In addition, an electric expansion valve 43 is provided, the auxiliary circuit 48 has a gas pipe 42 through which refrigerant flows out from the upper portion of the tank 36 and flows into the electric expansion valve 43, and the control device 57 is operated by the electric expansion valve 43. Since the pressure TIP of the refrigerant flowing into the engine 39 is adjusted, the electric expansion valve 43 controls the pressure TIP of the refrigerant conveyed to the electric expansion valve 39 while suppressing the influence of the fluctuation of the high-pressure side pressure HP. Will be able to.

  Further, by lowering the pressure TIP of the refrigerant flowing into the electric expansion valve 39 by the electric expansion valve 43, it is possible to use a pipe having a low pressure resistance as the pipe reaching the electric expansion valve 39. Thereby, it becomes possible to improve workability and construction cost.

  In particular, when the low temperature gas is extracted from the upper part of the tank 36 via the electric expansion valve 43, the pressure in the tank 36 is reduced. As a result, the temperature is lowered in the tank 36, so that the refrigerant condenses, and the liquid refrigerant can be effectively stored in the tank 36.

  In this case, since the control device 57 sets the opening degree of the electric expansion valve 43 at the time of starting the electric expansion valve 43 in such a direction that the higher the outside air temperature is, based on the index representing the outside air temperature, the starting time in the environment where the outside air temperature is high. It is possible to suppress an increase in the pressure in the tank 36 and to prevent an increase in the pressure of the refrigerant flowing into the electric expansion valve 39.

  Further, the control device 57 controls the valve opening degree of the electric expansion valve 43 to control the pressure TIP of the refrigerant flowing into the electric expansion valve 39 to a predetermined target value SP, and based on an index representing the outside air temperature, If the target value SP of the pressure of the refrigerant flowing into the electric expansion valve 39 is set so as to increase as the outside air temperature increases, the pressure TIP of the refrigerant flowing into the electric expansion valve 39 in an environment where the outside air temperature is high. The target value SP during operation increases, and the target value SP decreases in an environment where the outside air temperature is low.

  As a result, in a situation where the pressure increases due to the influence of a high outside air temperature, the target value SP of the pressure TIP of the refrigerant flowing into the electric expansion valve 39 increases, so that the valve opening degree of the electric expansion valve 43 becomes excessively large. It is possible to prevent the inconvenience that the refrigerant flows excessively in the auxiliary circuit 48. On the other hand, in a situation where the pressure becomes low at a low outside air temperature, the target value SP of the pressure TIP of the refrigerant flowing into the electric expansion valve 39 also becomes low, so that the valve opening degree of the electric expansion valve 43 becomes too small and It is possible to prevent a disadvantage that the amount of refrigerant flowing in is excessively reduced. As a result, the amount of refrigerant flowing in the auxiliary circuit 48 can be accurately adjusted by appropriately controlling the valve opening degree of the electric expansion valve 43 regardless of the change in the outside air temperature accompanying the change in season.

  Further, when the pressure of the refrigerant flowing into the electric expansion valve 39 rises to a predetermined specified value MTIP, the control device 57 increases the valve opening degree of the electric expansion valve 43, so that the refrigerant conveyed to the electric expansion valve 39 is increased. It becomes possible to always maintain the pressure TIP below the specified value MTIP, and it is possible to reliably achieve the effect of suppressing the influence of the high pressure side pressure fluctuation and the effect of suppressing the pressure of the refrigerant conveyed to the electric expansion valve 39. Become.

  In addition, an electric expansion valve 47 is provided, and the auxiliary circuit 48 has a liquid pipe 46 through which refrigerant flows out from the lower portion of the tank 36 and flows into the electric expansion valve 47, and the controller 57 controls the valve opening degree of the electric expansion valve 47. By controlling the amount of liquid refrigerant flowing through the first flow path 29A of the split heat exchanger 29, the discharge temperature of the refrigerant discharged from the compressor 11 to the gas cooler 28 is controlled to a predetermined target value TDT. Therefore, the liquid refrigerant in the lower part of the tank 36 is caused to flow through the first flow path 29A of the split heat exchanger 29 via the electric expansion valve 47, and the main circuit 38 flowing through the second flow path 29B of the split heat exchanger 29 is supplied. The supercooling of the refrigerant can be increased.

  Thereby, the liquid phase ratio of the refrigerant conveyed to the electric expansion valve 39 can be increased and can be made to flow into the electric expansion valve 39 in a full state. Further, since the temperature of the refrigerant sucked by the compressor 11 is also lowered, as a result, the refrigerant discharge temperature discharged from the compressor 11 to the gas cooler 28 can be lowered to the target value TDT. It is possible to protect the compressor 11.

  In this case, the control device 57 changes the target value TDT of the refrigerant discharge temperature in a direction to lower the higher the evaporation temperature based on the index representing the refrigerant evaporation temperature in the evaporator 41. Under refrigeration conditions where the evaporation temperature is high, it is possible to ensure supercooling of the refrigerant in the main circuit 38 in the split heat exchanger 29 and stably maintain the refrigeration capacity.

  In addition, an internal heat exchanger 15 is provided for exchanging heat between the refrigerant flowing into the electric expansion valve 39 and the refrigerant discharged from the evaporator 41, and the low-temperature refrigerant discharged from the evaporator 41 in the internal heat exchanger 15. Thus, the refrigerant flowing into the electric expansion valve 39 can be cooled, so that the specific enthalpy at the inlet of the evaporator 41 can be reduced to effectively improve the refrigerating capacity.

  In particular, in a high outside air temperature environment where the outside air temperature is high, there is no pressure difference between the pressure in the tank 36 adjusted by the electric expansion valve 43 and the intermediate pressure MP of the compressor 11. In such a case, depending on the situation, the refrigerant in the main circuit 38 flowing in the second flow path 29B can be almost supercooled by the refrigerant in the auxiliary circuit 48 flowing in the first flow path 29A in the split heat exchanger 29. However, even in such a situation, the refrigerant flowing into the electric expansion valve 39 is cooled by the low-temperature refrigerant discharged from the evaporator 41 in the internal heat exchanger 15. In addition, since the refrigerant can be supplied to the electric expansion valve 39 in the full liquid state, it is possible to improve the refrigerating capacity. In particular, when carbon dioxide is used as a refrigerant as in the embodiment, according to the present invention, the refrigerating capacity can be effectively improved and the performance can be improved.

R Refrigeration apparatus 1 Refrigerant circuit 3 Refrigerator unit 4 Showcase 8, 9 Refrigerant pipe 11 Compressor 15 Internal heat exchanger 15A First flow path 15B Second flow path 22 Refrigerant introduction pipe 26 Intermediate pressure suction pipe 28 Gas cooler 29 Split heat exchanger 29A 1st flow path 29B 2nd flow path 32 Gas cooler outlet piping 33 Electric expansion valve (throttle means for pressure adjustment)
36 Tank 37 Gas cooler outlet piping 38 Main circuit 39 Electric expansion valve (main throttle means)
41 Evaporator 42 Gas piping 43 Electric expansion valve (first auxiliary circuit throttle means)
44 Intermediate pressure return pipe 45 Bypass circuit 46 Liquid pipe 47 Electric expansion valve (second throttle means for auxiliary circuit)
48 Auxiliary circuit 50 Solenoid valve (valve device)
57 Control device (control means)

Claims (11)

In the refrigerating apparatus in which the refrigerant circuit is configured by the compression means, the gas cooler, the main throttle means, and the evaporator, and the high pressure side is the supercritical pressure,
A pressure adjusting throttle means connected to the refrigerant circuit downstream of the gas cooler and upstream of the main throttle means;
A tank connected to the refrigerant circuit downstream of the pressure adjusting throttle means and upstream of the main throttle means;
A split heat exchanger provided in the refrigerant circuit downstream of the tank and upstream of the main throttle means;
An auxiliary circuit for causing the refrigerant in the tank to flow into the first flow path of the split heat exchanger through the auxiliary throttle means and then sucking into the intermediate pressure portion of the compression means;
A main circuit that causes the refrigerant to flow out from the lower portion of the tank, flows into the second flow path of the split heat exchanger, exchanges heat with the refrigerant flowing through the first flow path, and then flows into the main throttle means;
Control means for controlling the pressure adjusting throttle means,
The control means adjusts the high-pressure side pressure of the refrigerant circuit upstream of the pressure adjusting throttle means by the pressure adjusting throttle means ,
The auxiliary throttle means has a first auxiliary circuit throttle means,
The auxiliary circuit has a gas pipe that causes the refrigerant to flow out from the upper part of the tank and to flow into the first auxiliary circuit throttle means,
The said control means adjusts the pressure of the refrigerant | coolant which flows in into the said main aperture means by the said 1st auxiliary circuit aperture means, The freezing apparatus characterized by the above-mentioned .   2. The refrigeration according to claim 1, wherein the control means sets the opening degree at the time of starting the pressure adjusting throttle means in a direction of increasing as the outside air temperature increases based on an index representing the outside air temperature. apparatus. The control means controls the high pressure side pressure of the refrigerant circuit upstream of the pressure adjusting throttle means to a predetermined target value by controlling the opening of the pressure adjusting throttle means,
The refrigeration apparatus according to claim 1 or 2, wherein the target value of the high-pressure side pressure is set in a direction in which the higher the outside air temperature is, the higher the outside air temperature is, based on an index representing the outside air temperature.   The control means increases the opening of the pressure adjusting throttle means when the high pressure side pressure of the refrigerant circuit upstream of the pressure adjusting throttle means rises to a predetermined upper limit value. The refrigeration apparatus according to any one of claims 1 to 3. Wherein, based on an index that represents the outside air temperature, the higher the outside air temperature is high, 1 to claim, characterized in by increasing direction to set the opening degree at the start of the first auxiliary circuit throttle means The refrigeration apparatus according to claim 4 . The control means controls the pressure of the refrigerant flowing into the main throttle means to a predetermined target value by controlling the opening of the first auxiliary circuit throttle means,
Based on the indicator of the outside air temperature, the higher the outside air temperature is high, both in the direction to increase one of claims 1 to 5, characterized in that for setting a target value of the pressure of the refrigerant flowing into the main throttle means refrigeration apparatus according to any. Wherein, when the pressure of the refrigerant flowing into the main throttle means is increased to a predetermined specified value, according to claim 1 or claims, characterized in that to increase the opening of the first auxiliary circuit throttle means Item 7. The refrigeration apparatus according to any one of Items 6 to 6 . The auxiliary throttle means has second auxiliary circuit throttle means,
The auxiliary circuit has a liquid pipe that causes the refrigerant to flow out from the lower part of the tank and flow into the second auxiliary circuit throttle means,
The control means controls the opening degree of the second auxiliary circuit throttle means, and adjusts the amount of liquid refrigerant flowing through the first flow path of the split heat exchanger, so that the compression means changes the gas cooler. The refrigerating apparatus according to any one of claims 1 to 7 , wherein the discharge temperature of the discharged refrigerant is controlled to a predetermined target value. Wherein, based on an index that represents the evaporation temperature of the refrigerant in the evaporator, as the evaporation temperature is high, to claim 8, characterized in that changing the target value of the discharge temperature of the refrigerant in the direction to lower The refrigeration apparatus described. The refrigeration according to any one of claims 1 to 9 , further comprising an internal heat exchanger for exchanging heat between the refrigerant flowing into the main throttle means and the refrigerant discharged from the evaporator. apparatus. The refrigeration apparatus according to any one of claims 1 to 10 , wherein carbon dioxide is used as the refrigerant.

Images