JP7456107B2 - binary refrigerator - Google Patents

Description

This invention relates to a binary refrigerator, and in particular to a binary refrigerator equipped with a low-temperature side cooling circuit and a high-temperature side cooling circuit.

BACKGROUND ART Conventionally, a binary refrigerator including a low-temperature side cooling circuit and a high-temperature side cooling circuit is known (see, for example, Patent Document 1).

The above-mentioned Patent Document 1 discloses a binary refrigerator including a low-temperature side cooling circuit and a high-temperature side cooling circuit. In the dual refrigerator of Patent Document 1, when the refrigerant pressure in the low-temperature side cooling circuit or the refrigerant pressure in the high-temperature side cooling circuit becomes larger than a set value, both the low-temperature side cooling circuit and the high-temperature side cooling circuit is configured to shut down the compressor.

Utility Model Publication No. 2-38050

However, in the binary refrigerator of Patent Document 1, when the pressure of the refrigerant in the low-temperature side cooling circuit or the refrigerant pressure in the high-temperature side cooling circuit becomes larger than a set value, the low-temperature side cooling circuit and the high-temperature side cooling circuit Stop both compressors. For this reason, after the compressors of both the low-temperature side cooling circuit and the high-temperature side cooling circuit are restarted, the low-temperature side cooling circuit cannot be sufficiently cooled, so the pressure of the refrigerant in the low-temperature side cooling circuit is likely to increase again. As a result, there is an inconvenience that the compressors in both the low-temperature side cooling circuit and the high-temperature side cooling circuit stop again. Therefore, there is a problem in that it is difficult to stably continue the operation of the binary refrigerator.

This invention was made to solve the above-mentioned problems, and one object of the invention is to provide a binary refrigerator that can continue to operate stably.

A binary refrigerator according to one aspect of the present invention includes a first compressor that compresses a first refrigerant, a first condenser that condenses the first refrigerant discharged from the first compressor, and a first condenser. a low temperature side cooling circuit including a first expansion valve that expands the condensed first refrigerant; a first evaporator that evaporates the first refrigerant expanded by the first expansion valve; and a second cooling circuit that compresses the second refrigerant. a compressor; a second condenser that condenses the second refrigerant discharged from the second compressor; a second expansion valve that expands the second refrigerant condensed by the second condenser; a high temperature side cooling circuit including a second evaporator capable of evaporating the second refrigerant and exchanging heat with the first condenser; and a control unit controlling the operation of the first compressor and the second compressor. The controller continues the operation of the second compressor when the operation of the first compressor is interrupted when the pressure of the first refrigerant compressed by the first compressor is higher than the first threshold value. However, the first compressor is configured to resume operation after a predetermined period of time has elapsed since the pressure of the first refrigerant became equal to or less than a second threshold value, which is smaller than the first threshold value.

In the binary refrigerating machine according to one aspect of the present invention, as described above, the controller is configured to cause the second compressor to continue operating when the operation of the first compressor is interrupted based on predetermined conditions. Configure it as follows. As a result, even when the operation of the first compressor of the low temperature side cooling circuit is interrupted, the operation of the second compressor of the high temperature side cooling circuit can be continued and the high temperature side cooling circuit can be operated. The first condenser of the low temperature side cooling circuit can be stably cooled by the second evaporator of the high temperature side cooling circuit. As a result, when the first compressor of the low-temperature side cooling circuit restarts operation, the low-temperature refrigerant of the low-temperature side cooling circuit can be sufficiently cooled, allowing stable operation of the binary refrigerator. be able to.

In the binary refrigerator according to the first aspect, preferably, the control unit operates the first compressor and the second compressor to perform a dual operation in which cooling is performed by both the low-temperature side cooling circuit and the high-temperature side cooling circuit. and a unified operation in which the second compressor is stopped and cooling is performed by the low-temperature side cooling circuit, based on at least one of the load and the outside temperature, and in the dual operation, the operation of the first compressor is switched. The second compressor is configured to continue operating when the second compressor is interrupted. With this configuration, by switching between the one-way operation and the two-way operation based on at least one of the load and the outside temperature, the two-way refrigerator can be operated efficiently. In addition, in dual operation where both the first compressor and the second compressor are operated, even when the operation of the first compressor in the low temperature side cooling circuit is interrupted, the operation of the second compressor in the high temperature side cooling circuit is By continuing to do so, stable dual operation can be performed.

In the two-dimensional refrigerator according to the first aspect, preferably, the control unit is configured to suspend operation of the first compressor during defrosting of the first evaporator, or The second compressor is configured to continue operating when the operation of the first compressor is interrupted when the pressure of the first refrigerant is higher than a first threshold value. With this configuration, if the operation of the first compressor is interrupted during defrosting of the first evaporator in the low-temperature side cooling circuit, the operation of the first compressor can be quickly resumed after defrosting the first evaporator. The cooling operation can be restarted quickly. In addition, when the operation of the first compressor of the low-temperature side cooling circuit is interrupted when the pressure of the first refrigerant is higher than the first threshold, the first refrigerant with increased pressure is transferred to the high-temperature side cooling circuit. Since the second evaporator can perform cooling, the pressure of the first refrigerant can be efficiently lowered. Thereby, the operation of the first compressor of the low-temperature side cooling circuit can be restarted quickly, and the cooling operation can be restarted quickly.

In this case, preferably, the control unit controls the pressure of the first refrigerant when the operation of the first compressor is interrupted when the pressure of the first refrigerant compressed by the first compressor is higher than the first threshold value. The first compressor is configured to resume operation after a predetermined period of time has elapsed since the pressure became equal to or less than a second threshold value, which is smaller than the first threshold value. With this configuration, the operation of the first compressor of the low-temperature side cooling circuit can be restarted while the pressure of the first refrigerant is lowered and stabilized, so that when the operation of the first compressor is restarted, In addition, the binary refrigerator can continue to operate more stably.

In the binary refrigerator according to one aspect of the present invention, as described above , when the pressure of the first refrigerant compressed by the first compressor is higher than the first threshold, the controller If the operation of the first compressor is interrupted, the operation of the first compressor is resumed after a predetermined period of time has passed after the pressure of the first refrigerant becomes equal to or less than a second threshold value, which is the pressure before starting the first compressor. Configure it as follows. Thereby , the operation of the first compressor of the low temperature side cooling circuit can be restarted after the pressure of the first refrigerant is sufficiently lowered.

In the binary refrigerator according to the above aspect, the control unit is preferably configured to start the second compressor first when starting the first compressor and the second compressor, and then start the first compressor after a predetermined time has elapsed. With this configuration, the second compressor of the high-temperature side cooling circuit is operated first, and the first compressor can be started while the low-temperature side cooling circuit is cooled, so that the binary refrigerator can be started efficiently and stably.

According to the present invention, as described above, it is possible to provide a binary refrigerator that can continue to operate stably.

FIG. 2 is a diagram showing a cooling circuit of a binary refrigerator according to an embodiment. It is a diagram showing a first example of operation of a binary refrigerator according to an embodiment. It is a figure which showed the 2nd example of operation of the binary refrigerator by one embodiment. FIG. 2 is a mapping diagram showing an example of conditions for one-way operation and two-way operation of a two-way refrigerator according to an embodiment.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments embodying the present invention will be described based on the drawings.

The configuration of the binary refrigerator 100 according to this embodiment will be described with reference to FIGS. 1 to 4. The binary refrigerator 100 is configured as a cooling device for cooling (freezing/refrigerating) fresh foods and the like in the showcase 110.

Specifically, as shown in FIG. 1, the binary refrigerator 100 includes a low temperature (low source) side cooling circuit 1, a compressor cooling circuit 2, a high temperature (high source) side cooling circuit 3, and a high temperature (high source) side cooling circuit 1. It is equipped with an exchanger 4. Note that a low-temperature (low-base) refrigerant and a high-temperature (high-base) refrigerant flow through the low-temperature side cooling circuit 1 and the high-temperature side cooling circuit 3, respectively. For example, the low-temperature refrigerant includes R744 (CO ₂ ), and the high-temperature refrigerant includes R1234yf (CF ₃ CF=CH ₂ ). Note that the low-temperature refrigerant is an example of the "first refrigerant" in the claims, and the high-temperature refrigerant is an example of the "second refrigerant" in the claims.

The low temperature side cooling circuit 1 constitutes a cooling circuit for cooling the inside of the showcase 110. The low temperature side cooling circuit 1 includes a compressor 11, a radiator 12, an expansion valve 13, and an evaporator 14. Further, the low temperature side cooling circuit 1 includes a condenser 41. Further, the low temperature side cooling circuit 1 is provided with a pressure sensor 15 and a temperature sensor 16. Note that the compressor 11 is an example of a "first compressor" in the claims, and the expansion valve 13 is an example of a "first expansion valve" in the claims. Further, the evaporator 14 is an example of a "first evaporator" in the claims, and the condenser 41 is an example of the "first condenser" in the claims.

Compressor 11 is configured to compress low-temperature refrigerant. Compressor 11 is controlled by an inverter (not shown). That is, the rotation speed of the compressor 11 is controlled by inverter control (frequency control). Thereby, the compressor 11 is configured to be able to adjust the flow rate of the low-temperature refrigerant discharged from the compressor 11. The radiator 12 is configured to pre-cool the high-temperature, high-pressure, low-temperature refrigerant flowing out from the compressor 11 before flowing it into the heat exchanger 4 . The condenser 32 is configured to condense the low-temperature refrigerant discharged from the compressor 11.

The expansion valve 13 is configured to expand the low-temperature refrigerant condensed by the condenser 32. The expansion valve 13 is configured, for example, as a needle valve. The opening degree of the expansion valve 13 is adjusted by a stepping motor (not shown) attached to the expansion valve 13. The evaporator 14 is configured to evaporate the low-temperature refrigerant expanded by the expansion valve 13. In addition, the evaporator 14 is configured to cool the air in the showcase 110 by blowing air into it by a fan.

The pressure sensor 15 is configured to detect the pressure of the low-temperature refrigerant on the high-pressure side of the low-temperature side cooling circuit 1 . That is, the pressure sensor 15 is arranged downstream of the compressor 11 and upstream of the expansion valve 13. The pressure sensor 15 is configured to detect the pressure of the low-temperature refrigerant compressed by the compressor 11. The pressure sensor 15 is configured to transmit the detected pressure to the control unit 5. The temperature sensor 16 is configured to detect the temperature of the cooling air cooled by the evaporator 14 and blown out. The temperature sensor 16 is configured to transmit the detected temperature to the control unit 5.

The compressor cooling circuit 2 is provided separately from the low temperature side cooling circuit 1. The compressor cooling circuit 2 includes an oil separator 21 and a heat exchanger 22. The oil separator 21 is configured to separate a gas phase and a liquid phase of the low-temperature refrigerant discharged from the compressor 11. The heat exchanger 22 is configured to cool carbon dioxide as a low-temperature refrigerant that has flowed out from the compressor 11. Here, in the heat exchanger 22, the low-temperature refrigerant wastes heat to the liquid-phase low-temperature refrigerant separated in the oil separator 21. As a result, the liquid-phase low-temperature refrigerant is heated. The heated low-temperature refrigerant is then supplied to the compressor 11 again and compressed.

The compressor 11 has a low stage compression section 11a and a high stage compression section 11b. The low-stage compression section 11a and the high-stage compression section 11b are driven by a common drive source in such a manner that the rotational speed ratio thereof is constant. The low-stage compression section 11a is configured to compress the sucked low-temperature refrigerant from low pressure to intermediate pressure. The high-stage compression section 11b is configured to compress the low-temperature refrigerant compressed to intermediate pressure and compress it from intermediate pressure to high pressure. In this way, the compressor 11 cools the low-temperature refrigerant (carbon dioxide) compressed to intermediate pressure by the low-stage compression section 11a in the heat exchanger 22, and then cools the low-temperature refrigerant (carbon dioxide) compressed to an intermediate pressure by the high-stage compression section 11b. carbon) is configured to compress

The high temperature side cooling circuit 3 is configured to improve the cooling performance of the low temperature side cooling circuit 1 that cools the inside of the showcase 110 by cooling the low temperature refrigerant flowing through the low temperature side cooling circuit 1. The high temperature side cooling circuit 3 includes a compressor 31, a condenser 32, and an expansion valve 33. Further, the high temperature side cooling circuit 3 includes an evaporator 42 . Further, the high temperature side cooling circuit 3 is provided with a pressure sensor 34 . Note that the compressor 31 is an example of a "second compressor" in the claims, and the condenser 32 is an example of a "second condenser" in the claims. Furthermore, the expansion valve 33 is an example of a "second expansion valve" in the claims, and the evaporator 42 is an example of a "second evaporator" in the claims.

The compressor 31 is configured to compress high temperature refrigerant. Compressor 31 is controlled by an inverter (not shown). That is, the rotation speed of the compressor 31 is controlled by inverter control (frequency control). Thereby, the compressor 31 is configured to be able to adjust the flow rate of the high temperature refrigerant discharged from the compressor 31. The condenser 32 is configured to condense the high temperature refrigerant discharged from the compressor 31.

The expansion valve 33 is configured to expand the high temperature refrigerant condensed by the condenser 32. The expansion valve 33 is composed of, for example, a needle valve. The opening degree of the expansion valve 33 is adjusted by a stepping motor (not shown) attached to the expansion valve 33. The evaporator 42 is configured to evaporate the high temperature refrigerant expanded by the expansion valve 33.

The pressure sensor 34 is configured to detect the pressure of the high temperature refrigerant on the high pressure side of the high temperature side cooling circuit 3. That is, the pressure sensor 34 is located downstream of the compressor 31 and upstream of the expansion valve 33. The pressure sensor 34 is configured to detect the pressure of the high temperature refrigerant compressed by the compressor 31. The pressure sensor 34 is configured to transmit the detected pressure to the control unit 5.

The heat exchanger 4 is configured by, for example, a plate heat exchanger. The heat exchanger 4 is constituted by a latent heat type heat exchanger. The heat exchanger 4 is provided across the high temperature side cooling circuit 3 and the low temperature side cooling circuit 1. The heat exchanger 4 is configured to be able to exchange heat between the condenser 41 of the low temperature side cooling circuit 1 and the evaporator 42 of the high temperature side cooling circuit 3. Specifically, it is configured such that the high temperature refrigerant is evaporated in the evaporator 42 and the low temperature refrigerant is condensed in the condenser 41. That is, in the heat exchanger 4, the high temperature refrigerant changes from a liquid phase to a gas phase. Furthermore, in the heat exchanger 4, the low-temperature refrigerant changes from a gas phase to a liquid phase. As a result, heat is released from the low-temperature refrigerant and absorbed by the high-temperature refrigerant.

The high temperature refrigerant is a refrigerant that can remove heat more efficiently than the low temperature refrigerant. That is, the high temperature refrigerant has a coefficient of performance equivalent to R410A and R404A. Although low-temperature refrigerants have lower heat removal efficiency than high-temperature refrigerants, they have a smaller impact on the environment than high-temperature refrigerants. The high temperature refrigerant is a refrigerant that has a lower global warming potential than R410A and R404A. The low-temperature refrigerant has a lower global warming potential than the high-temperature refrigerant. Note that the global warming potential is a numerical value that indicates the degree of the greenhouse effect.

The control unit 5 is configured to control the operation of the compressor 11 and the compressor 31. Further, the control unit 5 is configured to control the opening degrees of the expansion valve 13 and the expansion valve 33. Specifically, the control unit 5 controls the operation of the compressor 11 and the opening degree of the expansion valve 13 based on the detection results of the pressure sensor 15 and the temperature sensor 16. Further, the control unit 5 controls the operation of the compressor 31 based on the detection result of the pressure sensor 34.

Here, in this embodiment, the control unit 5 is configured to continue the operation of the compressor 31 when the operation of the compressor 11 is interrupted based on a predetermined condition. Specifically, the control unit 5 is configured to continue the operation of the compressor 31 when the operation of the compressor 11 is interrupted when the evaporator 14 is defrosted. Further, the control unit 5 is configured to continue the operation of the compressor 31 when the operation of the compressor 11 is interrupted when the pressure of the low-temperature refrigerant compressed by the compressor 11 is higher than the first threshold value. It is composed of

Here, as shown in FIG. 2, the control unit 5 is configured to protect the low temperature side cooling circuit 1 when the pressure on the high pressure side of the low temperature refrigerant detected by the pressure sensor 15 exceeds the first threshold. The compressor 11 is configured to stop operating at the same time. In addition, when the operation of the compressor 11 is interrupted when the pressure of the low-temperature refrigerant compressed by the compressor 11 is higher than the first threshold, the control unit 5 controls the control unit 5 to control the control unit 5 so that the pressure of the low-temperature refrigerant becomes higher than the first threshold. The compressor 11 is configured to resume operation after a predetermined time period has elapsed since the temperature becomes equal to or less than a second threshold value, which is smaller than the threshold value. Note that the second threshold is the pressure before starting the compressor 11. Further, the predetermined time (regular time) is set to be about several minutes (for example, about 1 minute to 5 minutes).

In the example shown in FIG. 2, the control unit 5 issues a start command for the compressor 11 of the low temperature side cooling circuit 1 and a start command for the compressor 31 of the high temperature side cooling circuit 3 at time t0. As a result, the operation of the compressor 11 and the compressor 31 is started. Then, at time t1, when the control unit 5 detects that the pressure of the low-temperature refrigerant in the low-temperature side cooling circuit 1 exceeds the first threshold, it turns off the startup command for the compressor 11 in the low-temperature side cooling circuit 1. Make it. As a result, the operation of the compressor 11 is stopped. In this case, the control unit 5 causes the compressor 31 of the high temperature side cooling circuit 3 to continue operating. When the control unit 5 detects that the pressure of the low-temperature refrigerant in the low-temperature side cooling circuit 1 has become equal to or lower than the second threshold at time t2, the control unit 5 controls the low-temperature side cooling circuit 1 at time t3 after a predetermined period of time has elapsed. The start command for the compressor 11 is turned ON. As a result, the operation of the compressor 11 is restarted.

In addition, as shown in FIG. 4, the control unit 5 operates the compressor 11 and the compressor 31 to perform two-way operation in which cooling is performed by both the low-temperature side cooling circuit 1 and the high-temperature side cooling circuit 3, and the compressor 31 is stopped and cooling is performed by the low-temperature side cooling circuit 1, the system is configured to switch between one operation and the other based on at least one of the load and the outside temperature. Specifically, the control unit 5 performs control to perform unified operation in which cooling is performed only by the low temperature side cooling circuit 1 when the outside temperature is below the temperature T1 and the load is below L1. Furthermore, when the outside temperature is equal to or higher than temperature T2 or the load is equal to or higher than L2, the control unit 5 performs control to perform dual operation in which both the low-temperature side cooling circuit 1 and the high-temperature side cooling circuit 3 perform cooling. However, T2>T1 and L2>L1. Further, a region where the outside temperature is higher than or equal to temperature T1 and lower than temperature T2 when the load is lower than or equal to L2, and a region where the load is higher than or equal to L1 and lower than or equal to L2 when the outside temperature is lower than or equal to temperature T2 are set as switching regions. That is, the control unit 5 performs control to switch to the one-way operation when the load becomes less than L1 or when the outside temperature becomes less than the temperature T1 during the two-way operation. Further, the control unit 5 performs control to switch to dual operation when the load becomes equal to or higher than L2 or when the outside temperature becomes equal to or higher than temperature T2 during single operation.

Further, the control unit 5 is configured to continue the operation of the compressor 31 when the operation of the compressor 11 is interrupted in the dual operation. That is, the control unit 5 is configured to continue operating the compressor 31 regardless of the operating state of the compressor 11 in the dual operation. However, the control unit 5 is configured to stop the operation of the compressor 31 when the pressure of the high temperature refrigerant in the high temperature side cooling circuit 3 becomes higher than a specified pressure.

Further, as shown in FIG. 3, when starting the compressor 11 and the compressor 31, the control unit 5 starts the compressor 31 first, and then starts the compressor 11 after a predetermined time (regular time) has elapsed. is configured to do so. That is, the control unit 5 issues a startup command to the compressor 31 of the high temperature side cooling circuit 3 at time t10, and operates the compressor 31. Thereafter, the control unit 5 issues a start command to the compressor 11 of the low temperature side cooling circuit 1 at time t11 after a predetermined time (regular time) has elapsed from time t10, and operates the compressor 11.

(Effects of this embodiment)
In this embodiment, the following effects can be obtained.

In this embodiment, as described above, the control unit 5 is configured to continue the operation of the compressor 31 when the operation of the compressor 11 is interrupted based on predetermined conditions. As a result, even when the operation of the compressor 11 of the low temperature side cooling circuit 1 is interrupted, the operation of the compressor 31 of the high temperature side cooling circuit 3 can be continued and the high temperature side cooling circuit 3 can be operated. , the condenser 41 of the low temperature side cooling circuit 1 can be stably cooled by the evaporator 42 of the high temperature side cooling circuit 3. As a result, when the operation of the compressor 11 of the low-temperature side cooling circuit 1 is restarted, the low-temperature refrigerant of the low-temperature side cooling circuit 1 can be sufficiently cooled, so that the operation of the binary refrigerator 100 can be stabilized. Can be continued.

Further, in this embodiment, as described above, the control unit 5 is operated in a dual operation in which the compressor 11 and the compressor 31 are operated and cooling is performed by both the low-temperature side cooling circuit 1 and the high-temperature side cooling circuit 3. , the compressor 31 is stopped and cooling is performed by the low-temperature side cooling circuit 1 to switch between a single operation based on at least one of the load and the outside temperature, and the operation of the compressor 11 is interrupted in the dual operation. When this happens, the compressor 31 is configured to continue operating. Thereby, by switching between the one-way operation and the two-way operation based on at least one of the load and the outside temperature, the two-way refrigerator can be operated efficiently. In addition, in dual operation where both the compressor 11 and the compressor 31 are operated, even when the operation of the compressor 11 of the low temperature side cooling circuit 1 is interrupted, the operation of the compressor 31 of the high temperature side cooling circuit 3 is continued. By doing so, stable dual operation can be performed.

Further, in this embodiment, as described above, when the control unit 5 interrupts the operation of the compressor 11 when defrosting the evaporator 14, or when the pressure of the low-temperature refrigerant compressed by the compressor 11 is The configuration is such that when the operation of the compressor 11 is interrupted when is larger than the first threshold value, the operation of the compressor 31 is continued. As a result, if the operation of the compressor 11 is interrupted during defrosting of the evaporator 14 of the low-temperature side cooling circuit 1, the operation of the compressor 11 is quickly restarted after defrosting the evaporator 14, and the cooling operation is quickly resumed. can be resumed. In addition, when the operation of the compressor 11 of the low-temperature side cooling circuit 1 is interrupted when the pressure of the low-temperature refrigerant is higher than the first threshold, the low-temperature refrigerant with increased pressure is transferred to the high-temperature side cooling circuit 1. Since the evaporator 42 can perform cooling, the pressure of the low-temperature refrigerant can be efficiently lowered. Thereby, the operation of the compressor 11 of the low temperature side cooling circuit 1 can be restarted quickly, and the cooling operation can be restarted quickly.

In addition, in this embodiment, as described above, the control unit 5 is configured to resume operation of the compressor 11 when the operation of the compressor 11 is interrupted when the pressure of the low-temperature refrigerant compressed by the compressor 11 is greater than the first threshold value, and resume operation of the compressor 11 a predetermined time after the pressure of the low-temperature refrigerant falls to or below a second threshold value that is smaller than the first threshold value. This allows the operation of the compressor 11 of the low-temperature side cooling circuit 1 to be resumed with the pressure of the low-temperature refrigerant reduced and stabilized, so that when the operation of the compressor 11 is resumed, the binary chiller 100 can continue to operate more stably.

Further, in the present embodiment, as described above, when the operation of the compressor 11 is interrupted when the pressure of the low-temperature refrigerant compressed by the compressor 11 is greater than the first threshold, The compressor 11 is configured to resume operation after a predetermined period of time has elapsed since the pressure of the low-temperature refrigerant became equal to or lower than a second threshold value, which is the pressure before starting the compressor 11. Thereby, the operation of the compressor 11 of the low-temperature side cooling circuit 1 can be restarted after the pressure of the low-temperature refrigerant is sufficiently lowered.

Further, in the present embodiment, as described above, when starting the compressor 11 and the compressor 31, the control unit 5 starts the compressor 31 first, and then starts the compressor 11 after a predetermined period of time has elapsed. Configure it as follows. As a result, the compressor 31 of the high-temperature side cooling circuit 3 can be operated first, and the compressor 11 can be started with the low-temperature side cooling circuit 1 cooled, so that the binary refrigerator 100 can be efficiently stabilized. It can be started by

(Modified example)
Note that the embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the description of the embodiments described above, and further includes all changes (modifications) within the meaning and range equivalent to the claims.

For example, in the above embodiment, the low temperature refrigerant (first refrigerant) contains R744 (CO ₂ ), and the high temperature refrigerant (second refrigerant) contains R1234yf (CF ₃ CF=CH ₂ ). Although shown, the present invention is not limited thereto. In the present invention, the first refrigerant and the second refrigerant are R744 (CO ₂ ) and R1234yf (CF ₃ CF=CH ₂ ), respectively, provided that the coefficient of performance, global warming potential, and pressure drop satisfy desired conditions. Other refrigerants may also be used. For example, it may be HFC (hydrofluorocarbon), other HFO (hydrofluoroolefins), or other natural refrigerants (ammonia, propane, etc.). It may also be a mixture of HFCs (R410A, R404A, etc.).

Further, in the above embodiment, an example of a configuration in which the showcase is cooled by the binary refrigerator of the present invention is shown, but the present invention is not limited to this. The dual refrigerator of the present invention may cool objects other than the showcase. For example, the dual refrigerator of the present invention may be used to cool refrigerators, freezers, air conditioners, water coolers, refrigerated trucks, vending machines, warehouses, storages, containers, and the like.

Further, in the above embodiment, an example of a configuration is shown in which the one-way operation and the two-way operation are switched based on the load and the outside temperature, but the present invention is not limited to this. In the present invention, the one-way operation and the two-way operation may be switched based on at least one of the load and the outside temperature. Moreover, you may switch between one-way operation and two-way operation based on another condition. Alternatively, only dual operation may be performed without switching to single operation.

Further, in the above embodiment, an example of a configuration in which the rotational speed of the compressor is controlled by inverter control (frequency control) is shown, but the present invention is not limited to this. In the present invention, the rotation speed of the compressor may be controlled by other than inverter control. For example, the compressor may include a DC motor, and the rotation speed may be controlled by controlling the current value.

Further, in the above embodiment, an example of a configuration in which one evaporator is provided in the low temperature side cooling circuit is shown, but the present invention is not limited to this. In the present invention, a plurality of evaporators may be provided in parallel or in series in the low temperature side cooling circuit. In this case, a plurality of evaporators may be used to cool a plurality of objects to be cooled.

1 Low temperature side cooling circuit 3 High temperature side cooling circuit 5 Control section 11 Compressor (first compressor)
13 Expansion valve (first expansion valve)
14 Evaporator (first evaporator)
31 Compressor (second compressor)
32 Condenser (second condenser)
33 Expansion valve (second expansion valve)
41 Condenser (first condenser)
42 Evaporation (second evaporator)
100 Binary refrigerator

Claims (5)

a first compressor that compresses a first refrigerant; a first condenser that condenses the first refrigerant discharged from the first compressor; and a first condenser that expands the first refrigerant condensed by the first condenser. a low temperature side cooling circuit including a first expansion valve and a first evaporator that evaporates the first refrigerant expanded by the first expansion valve;
a second compressor that compresses a second refrigerant; a second condenser that condenses the second refrigerant discharged from the second compressor; and a second condenser that expands the second refrigerant condensed by the second condenser. a high temperature side cooling circuit including a second expansion valve and a second evaporator that evaporates the second refrigerant expanded by the second expansion valve and can exchange heat with the first condenser;
A control unit that controls the operation of the first compressor and the second compressor,
The control unit controls the pressure of the first refrigerant when the operation of the first compressor is interrupted when the pressure of the first refrigerant compressed by the first compressor is higher than a first threshold value. The binary refrigerator is configured to restart the operation of the first compressor after a predetermined period of time has passed since the value becomes equal to or less than a second threshold value, which is smaller than the first threshold value. The control unit operates the first compressor and the second compressor to perform a dual operation in which cooling is performed by both the low-temperature side cooling circuit and the high-temperature side cooling circuit, and stopping the second compressor. and is configured to switch between a unified operation in which cooling is performed by the low-temperature side cooling circuit based on at least one of a load and an outside temperature, and when interrupting operation of the first compressor in the dual operation. 2. The binary refrigerator according to claim 1, wherein the binary refrigerator is configured to continue operation of the second compressor. The binary refrigeration machine according to claim 1 or 2, wherein the control unit is configured to continue operation of the second compressor when the operation of the first compressor is interrupted during defrosting of the first evaporator, or when the operation of the first compressor is interrupted when the pressure of the first refrigerant compressed by the first compressor is greater than the first threshold value. The binary refrigerator according to any one of claims 1 to 3, wherein, when operation of the first compressor is interrupted while a pressure of the first refrigerant compressed by the first compressor is higher than the first threshold value, the control unit is configured to resume operation of the first compressor a predetermined time after the pressure of the first refrigerant becomes equal to or lower than the second threshold value, which is a pressure before startup of the first compressor. The control unit is configured to start the second compressor first when starting the first compressor and the second compressor, and then start the first compressor after a predetermined period of time has elapsed. The binary refrigerator according to any one of claims 1 to 4 , wherein:

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