Freezer and method for controlling freezer

Abstract

To provide a freezer capable of ensuring a required degree of overcooling, and a method for controlling the freezer.SOLUTION: A refrigerator comprises a refrigeration cycle, a sensor, and a control device. The refrigeration cycle has a circulation line, a first compression part, a middle part, a second compression part, an injection pipe, an overcooling heat exchanger, an overcooling expansion valve, a main expansion valve, an evaporator, a bypass pipe, and a bypass valve. The control device has: an acquisition unit that acquires physical quantities related to the refrigeration cycle; a determination unit that determines whether a degree of overcooling of a refrigerant in the circulation line that has passed through the overcooling heat exchanger is below a target value based on the physical quantities related to the refrigeration cycle; and a valve control unit that controls the bypass valve to open the bypass pipe when the degree of overcooling of the refrigerant in the circulation line that has passed through the overcooling heat exchanger is below the target value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a refrigerator and a method for controlling a refrigerator. [Background technology]

[0002] Patent Document 1 discloses a two-stage screw refrigerator. This two-stage screw refrigerator is configured with a refrigerant / oil circulation flow path and a branch flow path. The refrigerant / oil circulation flow path includes a first-stage screw compressor, a second-stage screw compressor, a condenser, a subcooling heat exchanger, a main expansion valve, and an evaporator. The branch flow path branches off from a portion between the condenser and the subcooling heat exchanger in the refrigerant / oil circulation flow path, passes through a subcooling heat exchange expansion valve, and passes through the subcooling heat exchanger, and then joins an intermediate stage located on the suction side of the second-stage screw compressor at the discharge side of the first-stage screw compressor. The subcooling heat exchanger receives intermediate-pressure refrigerant that has been throttled and expanded to an intermediate pressure by the subcooling heat exchange expansion valve, bypassing a portion of the high-pressure refrigerant discharged from the second-stage screw compressor. This intermediate-pressure refrigerant immediately after the throttle expansion is injected into the intermediate stage, increasing the degree of subcooling of most of the remaining high-pressure refrigerant to the main expansion valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-315506 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the refrigerator described in Patent Document 1, for example, under low differential pressure conditions where the outside air temperature is low and the evaporation pressure is high, the differential pressure between the high-pressure refrigerant and the intermediate-pressure refrigerant becomes small, and the flow rate of the intermediate-pressure refrigerant that has been throttled and expanded to the intermediate pressure decreases. As a result, the degree of subcooling by the subcooling heat exchanger decreases, and the necessary degree of subcooling cannot be secured.

[0005] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a refrigerator capable of ensuring a required degree of subcooling, and a method for controlling the refrigerator. [Means for solving the problem]

[0006] In order to solve the above problems, a refrigerator according to the present disclosure includes a refrigeration cycle, a sensor for detecting physical quantities related to the refrigeration cycle, and a control device for controlling the refrigeration cycle. The refrigeration cycle includes a circulation line for circulating a refrigerant, a first compression unit provided in the circulation line for compressing a low-pressure refrigerant supplied from an outside to generate an intermediate-pressure refrigerant, a middle stage provided in the circulation line from which the intermediate-pressure refrigerant generated by the first compression unit is discharged, a second compression unit provided in the circulation line for compressing the intermediate-pressure refrigerant in the middle stage to generate a high-pressure refrigerant, a condenser for condensing the high-pressure refrigerant generated by the second compression unit, an injection pipe branching from a downstream side of the condenser in the circulation line and returning the refrigerant that has passed through the condenser to the middle stage, a subcooling heat exchanger that subcools the refrigerant that has passed through the condenser and flows through the circulation line by exchanging heat with the refrigerant flowing through the injection pipe, and a refrigerant that is provided upstream of the subcooling heat exchanger in the injection pipe and flows through the injection pipe. the control device has a subcooling expansion valve that expands the refrigerant that has passed through the subcooling heat exchanger before being supplied to the subcooling heat exchanger; a main expansion valve that is provided in the circulation line and expands the refrigerant that has passed through the subcooling heat exchanger; an evaporator that is provided downstream of the main expansion valve in the circulation line and evaporates the refrigerant that has passed through the main expansion valve; a bypass pipe that branches off from the injection pipe downstream of the subcooling heat exchanger and guides the refrigerant flowing through the injection pipe to a side upstream of the first compression section in the circulation line between the evaporator and the first compression section; and a bypass valve that is provided in the bypass pipe and opens and closes the bypass pipe. The control device has an acquisition unit that acquires a physical quantity related to the refrigeration cycle, a determination unit that determines whether or not a degree of subcooling of the refrigerant in the circulation line that has passed through the subcooling heat exchanger is below a target value based on the physical quantity related to the refrigeration cycle, and a valve control unit that controls the bypass valve to open the bypass pipe when the degree of subcooling of the refrigerant in the circulation line that has passed through the subcooling heat exchanger is below a target value.

[0007] In order to solve the above problems, a control method for a refrigerator according to the present disclosure is a control method for a refrigerator including a refrigeration cycle, a sensor for detecting a physical quantity related to the refrigeration cycle, and a control device for controlling the refrigeration cycle, the refrigeration cycle including a circulation line for circulating a refrigerant, a first compression unit provided in the circulation line for compressing a low-pressure refrigerant supplied from an outside to generate an intermediate-pressure refrigerant, a middle stage provided in the circulation line from which the intermediate-pressure refrigerant generated by the first compression unit is discharged, a second compression unit provided in the circulation line for compressing the intermediate-pressure refrigerant in the middle stage to generate a high-pressure refrigerant, a condenser for condensing the high-pressure refrigerant generated by the second compression unit, an injection pipe branching from a downstream side of the condenser in the circulation line and returning the refrigerant that has passed through the condenser to the middle stage, a subcooling heat exchanger that subcools the refrigerant that has passed through the condenser and flows through the circulation line by exchanging heat with the refrigerant flowing through the injection pipe, and a refrigerant flowing through the injection pipe, the refrigeration cycle including ... and a first compression unit provided in the injection pipe upstream of the subcooling heat exchanger. a subcooling expansion valve for expanding a refrigerant that has passed through the subcooling heat exchanger before being supplied to the subcooling heat exchanger; a main expansion valve provided in the circulation line for expanding the refrigerant that has passed through the subcooling heat exchanger; an evaporator provided in the circulation line downstream of the main expansion valve for evaporating the refrigerant that has passed through the main expansion valve; a bypass pipe that branches off from the injection pipe downstream of the subcooling heat exchanger and guides the refrigerant flowing through the injection pipe to a side in the circulation line between the evaporator and the first compression section and upstream of the first compression section; and a bypass valve provided in the bypass pipe for opening and closing the bypass pipe, wherein the control device acquires physical quantities related to the refrigeration cycle; the control device determines, based on the physical quantities related to the refrigeration cycle, whether or not a degree of subcooling of the refrigerant in the circulation line that has passed through the subcooling heat exchanger is below a target value; and, when a degree of subcooling of the refrigerant in the circulation line that has passed through the subcooling heat exchanger is below a target value, the control device controls the bypass valve to open the bypass pipe. Effect of the Invention

[0008] According to the refrigerator and the refrigerator control method of the present disclosure, a necessary degree of subcooling can be ensured. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic configuration diagram of a refrigerator according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is a functional block diagram of a control device according to the first embodiment of the present disclosure. [Diagram 3] 2 is a ph diagram showing an example of a change in state of a refrigerant circulating in the refrigerator according to the first embodiment of the present disclosure. FIG. [Figure 4] 2 is a ph diagram showing an example of a change in state of a refrigerant circulating in the refrigerator according to the first embodiment of the present disclosure. FIG. [Diagram 5] 2 is a ph diagram showing an example of a change in state of a refrigerant circulating in the refrigerator according to the first embodiment of the present disclosure. FIG. [Figure 6] 4 is a flowchart showing the procedure of a control method for a refrigerator according to the first embodiment of the present disclosure. [Figure 7] FIG. 4 is a diagram illustrating a correlation between outside air temperature and a degree of subcooling according to the first embodiment of the present disclosure. [Figure 8] FIG. 4 is a schematic configuration diagram of a refrigerator according to a second embodiment of the present disclosure. [Figure 9] FIG. 11 is a functional block diagram of a control device according to a second embodiment of the present disclosure. [Figure 10] 10 is a flowchart showing the steps of a control method for a refrigerator according to a second embodiment of the present disclosure. [Figure 11] FIG. 11 is a schematic configuration diagram of a refrigerator according to a third embodiment of the present disclosure. [Figure 12] FIG. 11 is a functional block diagram of a control device according to a third embodiment of the present disclosure. [Figure 13] 10 is a flowchart showing the steps of a control method for a refrigerator according to a third embodiment of the present disclosure. [Figure 14] FIG. 11 is a diagram illustrating a correlation between outside air temperature and a degree of subcooling according to a third embodiment of the present disclosure. [Figure 15]FIG. 11 is a schematic configuration diagram of a refrigerator according to a fourth embodiment of the present disclosure. [Figure 16] FIG. 11 is a functional block diagram of a control device according to a fourth embodiment of the present disclosure. [Figure 17] 10 is a flowchart showing the procedure of a control method for a refrigerator according to a fourth embodiment of the present disclosure. [Figure 18] FIG. 2 is a hardware configuration diagram according to an embodiment of the present disclosure. [Figure 19] FIG. 13 is a schematic configuration diagram of a refrigerator according to a modified example of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] First Embodiment (Refrigeration unit configuration) Hereinafter, a refrigerator 1 according to an embodiment of the present disclosure will be described with reference to FIGS. As shown in Fig. 1, the refrigerator 1 includes a refrigeration cycle 2, a sensor 50, and a control device 60. The refrigeration cycle 2 includes a refrigerant line 20, a compressor 30, a condenser 3, a subcooling heat exchanger 4, a subcooling expansion valve 5, a check valve 6, a main expansion valve 7, an evaporator 8, an accumulator 9, and a bypass valve 10. The refrigerator 1 uses, for example, CO2 as a refrigerant. The refrigerant line 20 includes a circulation line 21, an injection pipe 22, and a bypass pipe 23.

[0011] (Circulation Line) The refrigerant is circulated through the circulation line 21. In the circulation line 21, a compressor 30, a condenser 3, a subcooling heat exchanger 4, a main expansion valve 7, an evaporator 8, and an accumulator 9 are arranged in this order.

[0012] (Injection tube) The injection pipe 22 branches off from the circulation line 21 downstream of the condenser 3. The injection pipe 22 passes through the subcooling heat exchanger 4 and is connected to the compressor 30. The injection pipe 22 returns the refrigerant that has passed through the condenser 3 to a region in the compressor 30 from which an intermediate-pressure refrigerant is discharged (a middle stage portion 33 described later).

[0013] (Bypass pipe) The bypass pipe 23 branches off from the injection pipe 22 downstream of the subcooling heat exchanger 4. The bypass pipe 23 guides the refrigerant flowing through the injection pipe 22 to a position between the evaporator 8 and the first compression section 32 in the circulation line 21 and upstream of the first compression section 32. In this embodiment, the bypass pipe 23 connects a region between the subcooling heat exchanger 4 and the compressor 30 in the injection pipe 22 and a region between the evaporator 8 and the accumulator 9 in the circulation line 21 and upstream of the accumulator 9. The bypass pipe 23 allows the refrigerant flowing through the injection pipe 22 to flow into the circulation line 21 before (upstream of) the accumulator 9.

[0014] (Compressor) The compressor 30 has a casing 31, a first compression section 32, a middle stage section 33, and a second compression section .

[0015] (First compression section) The first compression section 32 is housed in the casing 31. The first compression section 32 compresses a low-pressure refrigerant supplied from the outside to generate an intermediate-pressure refrigerant.

[0016] (Middle section) The middle section 33 is a region within the casing 31 from which the intermediate-pressure refrigerant generated in the first compression section 32 is discharged.

[0017] (Second compression section) The second compression section 34 is housed within the casing 31. The second compression section 34 compresses the intermediate-pressure refrigerant in the middle stage section 33 to generate high-pressure refrigerant.

[0018] (Condenser) The condenser 3 is provided on the circulation line 21 downstream of the second compression section . The condenser 3 condenses the high-pressure refrigerant generated in the second compression section .

[0019] (Supercooling heat exchanger) The subcooling heat exchanger 4 is provided downstream of the condenser 3 in the circulation line 21. The subcooling heat exchanger 4 subcools the refrigerant that has passed through the condenser 3 and flows through the circulation line 21 by exchanging heat with the refrigerant that flows through the injection pipe 22.

[0020] (Subcooling expansion valve) The subcooling expansion valve 5 is provided upstream of the subcooling heat exchanger 4 in the injection pipe 22. The subcooling expansion valve 5 expands the refrigerant flowing through the injection pipe 22 before it is supplied to the subcooling heat exchanger 4.

[0021] (non-return valve) The check valve 6 is provided in the injection pipe 22 downstream of the subcooling heat exchanger 4. The check valve 6 prevents the refrigerant from flowing back from the compressor 30 through the bypass pipe 23 to the low-pressure side (upstream of the first compression section 32 of the circulation line 21).

[0022] (Main expansion valve) The main expansion valve 7 is provided on the circulation line 21 downstream of the subcooling heat exchanger 4. The main expansion valve 7 expands the refrigerant that has passed through the subcooling heat exchanger 4.

[0023] (Evaporator) The evaporator 8 is provided downstream of the main expansion valve 7 in the circulation line 21. The evaporator 8 evaporates the refrigerant that has passed through the main expansion valve 7.

[0024] (accumulator) The accumulator 9 is provided in the circulation line 21 between the evaporator 8 and the first compression section 32. The accumulator 9 recovers liquid refrigerant contained in the refrigerant returning from the circulation line 21 and the bypass pipe 23 to the compressor 30, and prevents liquid backflow.

[0025] (Bypass valve) The bypass valve 10 is provided in the bypass pipe 23. The bypass valve 10 is an electromagnetic valve that opens and closes the bypass pipe 23 and is controlled by a control device 60, which will be described later.

[0026] (Sensor) The sensor 50 detects a physical quantity related to the refrigeration cycle 2. The sensor 50 in this embodiment includes an outside air temperature sensor 51.

[0027] (Outside air temperature sensor) The outdoor air temperature sensor 51 is attached to an outdoor unit (not shown) etc. The outdoor air temperature sensor 51 detects the outdoor air temperature.

[0028] (Control device) The control device 60 controls the refrigeration cycle 2. As shown in FIG.

[0029] (Acquisition Department) The acquisition unit 61 acquires a physical quantity related to the refrigeration cycle 2 (for example, a physical quantity detected by the sensor 50, etc.).

[0030] (Judgment Department) The determination unit 62 determines whether the degree of subcooling of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4 falls below a target value based on a physical quantity related to the refrigeration cycle 2 (for example, a physical quantity detected by the sensor 50, etc.). In the following, unless otherwise specified, the "degree of subcooling" means "the degree of subcooling of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4" and represents the difference between the saturation temperature in the circulation line 21 immediately before passing through the subcooling heat exchanger 4 (position d) and the measured temperature immediately after passing through the subcooling heat exchanger 4 (position f). The determination unit 62 in this embodiment has an evaporation temperature determination unit 62a and an outside air temperature determination unit 62b.

[0031] (Evaporation temperature determination section) The evaporation temperature determination unit 62a determines whether or not the evaporation temperature of the evaporator 8 is equal to or higher than a threshold value.

[0032] (Outside air temperature determination section) The outside air temperature determination unit 62b determines whether the outside air temperature is equal to or lower than a threshold value.

[0033] (Valve control section) When the degree of subcooling of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4 falls below a target value, the valve control unit 63 controls the bypass valve 10 to open the bypass pipe 23. When the evaporation temperature of the evaporator 8 is equal to or higher than a threshold value and the outside air temperature is equal to or lower than a threshold value, the valve control unit 63 in this embodiment controls the bypass valve 10 to open the bypass pipe 23. Note that in this embodiment, the evaporation temperature of the evaporator 8 is preset in the control device 60, for example, when setting the internal temperature of the refrigerator 1.

[0034] (Operation of refrigerator) The operation of the refrigerator 1 according to the embodiment of the present disclosure will be described. The refrigerant circulates within the circulation line 21, and changes its state as shown in Figures 3 and 4. The states of the refrigerant at the positions of the alphabet (a to g) in Figures 3 and 4 correspond to the states indicated by the same alphabet in Figure 1.

[0035] Here, the refrigerant that has been throttled and expanded to an intermediate pressure by the subcooling expansion valve 5 flows into the subcooling heat exchanger 4, with part of the high-pressure refrigerant generated in the second compression section 34 being bypassed by the injection pipe 22. The refrigerant immediately after this throttle expansion is injected into the middle stage section 33 of the compressor 30, and the degree of supercooling of most of the remaining high-pressure refrigerant to the main expansion valve 7 is increased.

[0036] 3, under conditions where the outside air temperature is high and the evaporation temperature is low (high differential pressure conditions), the differential pressure (Δ1) between the high-pressure refrigerant (position d) and the intermediate-pressure refrigerant (position e) increases. This increases the injection flow rate of the refrigerant into the middle stage 33, and the degree of subcooling (Δ2) of the high-pressure refrigerant in the subcooling heat exchanger 4 (d → f) increases, ensuring the required degree of subcooling.

[0037] 4, under conditions where the outside air temperature is low and the evaporation temperature is high (low differential pressure conditions), the differential pressure (Δ1) between the high-pressure refrigerant (position d) and the intermediate-pressure refrigerant (position e) becomes small. This reduces the injection flow rate of the refrigerant into the middle stage 33, and the degree of subcooling (Δ2) of the high-pressure refrigerant in the subcooling heat exchanger 4 (d → f) becomes small, so that the required degree of subcooling may not be secured. As a countermeasure to this, the refrigerator 1 is provided with a bypass pipe 23 and a bypass valve 10 that opens and closes the bypass pipe 23.

[0038] Fig. 5 is a ph diagram when the outside air temperature is low and the evaporation temperature is high (low differential pressure condition) and the bypass pipe 23 is opened. The state of the refrigerant at each position of the alphabet (a to g) in Fig. 5 corresponds to the state indicated by the same alphabet in Fig. 1. Under conditions where the outside air temperature is low and the evaporation temperature is high (low differential pressure conditions), when the valve control unit 63 controls the bypass valve 10 to open the bypass pipe 23, the refrigerant that is originally injected into the middle stage unit 33 flows upstream (low pressure side) of the first compression unit 32. As a result, the high-pressure refrigerant at position d is throttled and expanded to a low pressure by the subcooling expansion valve 5, and the differential pressure (Δ1) between the high-pressure refrigerant (position d) and the low-pressure refrigerant (position e) becomes large. Therefore, even under conditions where the outside air temperature is low and the evaporation temperature is high (low differential pressure conditions), the flow rate of the throttled and expanded refrigerant (position e) can be secured, so that the degree of subcooling (Δ2) obtained by the subcooling expansion valve 5 can be increased and the required degree of subcooling can be secured.

[0039] (Procedure for controlling refrigerator) Next, a method for controlling the refrigerator 1 to open the bypass pipe 23 at an appropriate timing will be described.

[0040] The control method of the refrigerator 1 includes the steps of: the control device 60 acquiring the physical quantity detected by the sensor 50 (in this embodiment, step S2 described later); the control device 60 determining whether or not the degree of subcooling of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4 is below a target value based on the physical quantity related to the refrigeration cycle 2 (e.g., the physical quantity detected by the sensor 50) (in this embodiment, step S3 described later); and, when the degree of subcooling of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4 is below the target value, the control device 60 controlling the bypass valve 10 to open the bypass pipe 23 (in this embodiment, step S4 described later).

[0041] Hereinafter, the control method of the refrigerator 1 in this embodiment will be described in detail with reference to Figs. 6 and 7. Here, the control method of the refrigerator 1 will be described taking as an example a case where the target value of the degree of supercooling is about 10°C. Note that the actually secured degree of supercooling may deviate slightly from the target value of the degree of supercooling. In other words, when the target value of the degree of supercooling is 10°C, even if the actually secured degree of supercooling is 7°C or 8°C, it may be considered that the required degree of supercooling of 10°C is secured.

[0042] FIG. 6 is a flow chart showing the procedure of the control method of this embodiment. Fig. 7 is a diagram showing the correlation between the outside air temperature and the degree of supercooling for each evaporation temperature (ET) zone. Fig. 7 shows that the lower the evaporation temperature, the greater the degree of supercooling. Fig. 7 also shows that in any evaporation temperature zone, in a region where the outside air temperature is 0°C or lower, the degree of supercooling is approximately constant, and in a region where the outside air temperature is 0°C or higher, the degree of supercooling gradually increases as the outside air temperature increases. Fig. 7 also shows the region where the degree of supercooling is 10°C or lower with a dashed line.

[0043] As shown in FIG. 7, first, the evaporation temperature determination unit 62a determines whether or not the evaporation temperature of the evaporator 8, which is set in advance, is equal to or higher than a threshold value (−30° C. in this embodiment) (step S1). Here, as shown in FIG. 7, in a temperature range in which the evaporation temperature (ET) is −25° C. to −30° C. or lower, the target degree of subcooling of 10° C. or higher is ensured regardless of the outside air temperature. On the other hand, in a temperature range in which the evaporation temperature (ET) is −20° C. to −25° C. or higher, the target degree of subcooling of 10° C. is not ensured in a region in which the outside air temperature is 10° C. or lower. Therefore, in step S1, the threshold value for determining the evaporation temperature of the evaporator 8 is set to −30° C., and the evaporation temperature determination unit 62a determines whether or not the evaporation temperature of the evaporator 8 is equal to or higher than this threshold value (−30° C.) to determine whether or not the degree of subcooling is below the target value (10° C.). If the evaporation temperature of the evaporator 8 is not equal to or higher than the threshold value (-30°C) (step S1; NO), the degree of subcooling will not fall below the target value of 10°C, and the control flow ends without opening the bypass pipe 23. On the other hand, if the evaporation temperature of the evaporator 8 is equal to or higher than the threshold value (-30°C) (step S1; YES), the degree of subcooling may fall below the target value of 10°C, and the flow proceeds to step S2.

[0044] In step S2, the acquisition unit 61 acquires the outside air temperature from the outside air temperature sensor 51. After that, the outside air temperature determination unit 62b determines whether the outside air temperature is equal to or lower than the threshold value (step S3). As described above, in the region where the outside air temperature is equal to or lower than 10°C, the target degree of supercooling of 10°C is not ensured. Therefore, in step S3, the threshold value for determining the outside air temperature is set to 10°C, and the outside air temperature determination unit 62b determines whether the temperature is equal to or lower than this threshold value (10°C) to determine whether the degree of supercooling falls below the target value (10°C). If the outside air temperature is not equal to or lower than the threshold value (10°C) (step S3; NO), the degree of supercooling will not fall below the target value of 10°C, and the control flow ends without opening the bypass pipe 23. On the other hand, if the outside air temperature is equal to or lower than the threshold value (10°C) (step S3; YES), the valve control unit 63 controls the bypass valve 10 to open the bypass pipe 23 (step S4).

[0045] By step S4, the refrigerant that is originally injected into the middle stage section 33 flows upstream (low pressure side) of the first compression section 32. This increases the pressure difference (Δ1) between the high pressure refrigerant (position d) and the low pressure refrigerant (position e), and the flow rate of the throttled and expanded refrigerant (position e) can be ensured. This increases the degree of subcooling (Δ2) obtained by the subcooling expansion valve 5, and ensures the required degree of subcooling. Through the above procedures, the control flow of the refrigerator 1 related to opening of the bypass pipe 23 ends. The timing for blocking the bypass pipe 23 may be, for example, when a predetermined time has elapsed since the bypass pipe 23 was opened (step S4), or, similar to the procedure described above, when it is determined that the degree of subcooling has exceeded the target value based on the evaporation temperature or the outside air temperature. The order of the steps can be changed as appropriate. For example, step S2 may be performed before step S3, and may be performed before step S1.

[0046] (Action and effect) The refrigerator 1 of the present embodiment can provide the following advantageous effects.

[0047] In this embodiment, the bypass pipe 23 branches off from the injection pipe 22 downstream of the subcooling heat exchanger 4, and guides the refrigerant flowing through the injection pipe 22 to the upstream side of the first compression section 32 between the evaporator 8 and the first compression section 32 in the circulation line 21. The bypass pipe 23 is provided with a bypass valve 10 for opening and closing the bypass pipe 23. The control device 60 has an acquisition unit 61, a determination unit 62, and a valve control unit 63. The acquisition unit 61 acquires a physical quantity related to the refrigeration cycle 2. The determination unit 62 determines whether or not the degree of subcooling of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4 falls below a target value based on the physical quantity related to the refrigeration cycle 2. The valve control unit 63 controls the bypass valve 10 to open the bypass pipe 23 when the degree of subcooling of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4 falls below a target value.

[0048] Normally, under conditions where the outside air temperature is low and the evaporation temperature is high (low differential pressure conditions), the differential pressure (Δ1) between the high-pressure refrigerant (position d) and the low-pressure refrigerant (position e) becomes small, and the injection flow rate of the refrigerant to the middle stage 33 decreases. As a result, the degree of subcooling (Δ2) of the high-pressure refrigerant in the subcooling heat exchanger 4 (d → f) becomes small. In this embodiment, the control device 60 judges whether the degree of supercooling falls below the target value based on the physical quantity related to the refrigeration cycle 2. When the degree of supercooling falls below the target value, the control device 60 can control the bypass valve 10 to open the bypass pipe 23. Then, the refrigerant that is originally injected into the middle stage section 33 flows upstream (low pressure side) of the first compression section 32. As a result, the differential pressure (Δ1) between the high pressure refrigerant (position d) that passes through the circulation line 21 and is supplied to the supercooling heat exchanger 4 and the low pressure refrigerant (position e) that passes through the injection pipe 22 and is supplied to the supercooling heat exchanger 4 increases, and the flow rate of the refrigerant (position e) that is throttled and expanded by the supercooling expansion valve 5 can be secured. Therefore, the degree of supercooling (Δ2) obtained by the supercooling expansion valve 5 can be increased, and the required degree of supercooling can be secured. As described above, according to this embodiment, the control device 60 opens the bypass pipe 23 at an appropriate timing so that the degree of subcooling does not become smaller than the target value, thereby making it possible to ensure a necessary degree of subcooling.

[0049] In this embodiment, the sensor 50 includes an outside air temperature sensor 51. The outside air temperature sensor 51 detects the outside air temperature. The determination unit 62 has an evaporation temperature determination unit 62a and an outside air temperature determination unit 62b. The evaporation temperature determination unit 62a determines whether the evaporation temperature of the evaporator 8 is equal to or higher than a threshold value. The outside air temperature determination unit 62b determines whether the outside air temperature is equal to or lower than a threshold value. The valve control unit 63 controls the bypass valve 10 to open the bypass pipe 23 when the evaporation temperature of the evaporator 8 is equal to or higher than the threshold value and the outside air temperature is equal to or lower than the threshold value.

[0050] The higher the evaporation temperature is and the lower the outside air temperature is, the smaller the degree of supercooling tends to be. In this embodiment, first, the control device 60 judges whether or not the evaporation temperature is equal to or higher than a threshold value (-30°C) for a target value of the degree of supercooling (10°C). After it is judged that the evaporation temperature is equal to or higher than the threshold value, the control device 60 judges whether or not the outside air temperature is equal to or lower than a threshold value (10°C). If the outside air temperature is equal to or lower than the threshold value, there is a possibility that the degree of supercooling will fall below the target value, and therefore the control device 60 controls the bypass valve 10 to open the bypass pipe 23. In this way, the control device 60 performs two-stage judgment based on the evaporation temperature and the outside air temperature, thereby enabling the bypass pipe 23 to be opened with high efficiency and at a more appropriate timing.

[0051] In this embodiment, the evaporation temperature of the evaporator 8 is set in advance in the control device 60.

[0052] This makes it possible to eliminate the need for a step of detecting or calculating the evaporation temperature of the evaporator 8, thereby simplifying the control of the refrigerator 1.

[0053] In this embodiment, the bypass pipe 23 is provided with a check valve 6 .

[0054] As a result, even if the bypass pipe 23 is opened, the check valve 6 prevents the refrigerant from flowing back from the compressor 30 through the bypass pipe 23 to the low-pressure side (upstream of the first compression section 32 of the circulation line 21).

[0055] Second Embodiment Next, a second embodiment will be described with reference to Fig. 8 to Fig. 10. The same components as those in the above embodiment will be denoted by the same reference numerals and names, and the description will be omitted as appropriate. The components not described below are assumed to be the same as those in the above embodiment.

[0056] As shown in FIG. 8, in the refrigerator 101 of this embodiment, the sensor 150 includes an outside air temperature sensor 51 and a low-pressure side pressure sensor 52.

[0057] (Low pressure side pressure sensor) The low-pressure side pressure sensor 52 is provided in the circulation line 21 between the main expansion valve 7 and the first compression section 32, and upstream of the first compression section 32. More specifically, the low-pressure side pressure sensor 52 is provided in the circulation line 21 between the accumulator 9 and the compressor 30, and upstream of the compressor 30. The low-pressure side pressure sensor 52 detects the evaporation pressure (saturation pressure) of the evaporator 8.

[0058] (Control device) As shown in FIG. 9, the control device 160 further includes an evaporation temperature calculation unit 64 in addition to the acquisition unit 61, the determination unit 62, and the valve control unit 63.

[0059] (Evaporation temperature calculation section) The evaporation temperature calculation unit 64 calculates the evaporation temperature (saturation temperature) of the evaporator 8 based on the evaporation pressure (saturation pressure) of the evaporator 8.

[0060] (Procedure for controlling refrigerator) Next, a method for controlling the refrigerator 101 that opens the bypass pipe 23 at an appropriate timing will be described. In this embodiment, the method for controlling the refrigerator 101 will be described by taking as an example a case where the target value of the degree of subcooling is about 10°C.

[0061] FIG. 10 is a flow chart showing the procedure of the control method of this embodiment. As shown in FIG. 10, first, the acquisition unit 61 acquires the evaporation pressure from the low-pressure side pressure sensor 52 (step S11). Next, the evaporation temperature calculation unit 64 calculates the evaporation temperature (saturation temperature) of the evaporator 8 based on the evaporation pressure (saturation pressure) of the evaporator 8 (step S12). After that, the evaporation temperature determination unit 62a determines whether the calculated evaporation temperature of the evaporator 8 is equal to or higher than a threshold value (-30°C in this embodiment) (step S13). If the evaporation temperature of the evaporator 8 is not equal to or higher than the threshold value (-30°C) (step S13; NO), the degree of subcooling will not fall below the target value of 10°C, so the control flow ends without opening the bypass pipe 23. On the other hand, if the evaporation temperature of the evaporator 8 is equal to or higher than the threshold value (-30°C) (step S13; YES), the degree of subcooling may fall below the target value of 10°C, so the flow proceeds to step S14.

[0062] In step S14, the acquisition unit 61 acquires the outside air temperature from the outside air temperature sensor 51. After that, the outside air temperature determination unit 62b determines whether the outside air temperature is equal to or lower than a threshold value (10°C in this embodiment) (step S15). If the outside air temperature is not equal to or lower than the threshold value (10°C) (step S15; NO), the degree of subcooling does not fall below the target value of 10°C, and the control flow ends without opening the bypass pipe 23. On the other hand, if the outside air temperature is equal to or lower than the threshold value (10°C) (step S15; YES), the valve control unit 63 controls the bypass valve 10 to open the bypass pipe 23 (step S16).

[0063] By step S16, the refrigerant that is originally injected into the middle stage section 33 flows upstream (low pressure side) of the first compression section 32. As a result, similar to the first embodiment, the pressure difference (Δ1) between the high pressure refrigerant (position d) and the low pressure refrigerant (position e) increases, and the degree of subcooling (Δ2) obtained by the subcooling expansion valve 5 can be increased. Therefore, the necessary degree of subcooling can be secured. Through the above procedures, the control flow of the refrigerator 101 related to the opening of the bypass pipe 23 is completed. The timing for blocking the bypass pipe 23 may be, for example, when a predetermined time has elapsed since the bypass pipe was opened (step S16), or, similar to the procedure described above, when it is determined that the degree of subcooling has exceeded the target value based on the evaporation temperature or the outside air temperature. The order of the steps can be changed as appropriate. For example, step S14 may be executed before step S15, for example, before step S11.

[0064] (Action and effect) The refrigerator 101 of this embodiment can provide the following advantageous effects.

[0065] In this embodiment, the sensor 150 further includes a low-pressure side pressure sensor 52. The low-pressure side pressure sensor 52 is provided in the circulation line 21 between the main expansion valve 7 and the first compression section 32 and upstream of the first compression section 32, and detects the evaporation pressure of the evaporator 8. The control device 160 further includes an evaporation temperature calculation section 64. The evaporation temperature calculation section 64 calculates the evaporation temperature of the evaporator 8 based on the evaporation pressure of the evaporator 8.

[0066] This allows the control device 160 to calculate an accurate evaporation temperature. Therefore, the control device 160 can perform the determination based on the evaporation temperature with higher accuracy. Therefore, the control device 160 can open the bypass pipe at a more appropriate timing.

[0067] <Third embodiment> Next, a third embodiment will be described with reference to Fig. 11 to Fig. 14. The same components as those in the above-mentioned embodiment will be denoted by the same reference numerals and names, and the description thereof will be omitted as appropriate. The components not described below are assumed to be the same as those in the above-mentioned embodiment.

[0068] As shown in FIG. 11, the refrigerator 201 of the present embodiment includes a control device 260.

[0069] (Control device) As shown in FIG. 12, the control device 260 further includes an outside air temperature threshold calculation unit 65 in addition to an acquisition unit 61, a determination unit 62, and a valve control unit 63.

[0070] (Outside air temperature threshold calculation section) The outside air temperature threshold calculation unit 65 calculates a threshold used for determining the outside air temperature based on the evaporation temperature of the evaporator 8.

[0071] (Procedure for controlling refrigerator) Next, a method for controlling the refrigerator 201 that opens the bypass pipe 23 at an appropriate timing will be described. In this embodiment, the method for controlling the refrigerator 201 will be described by taking as an example a case where the target value of the degree of subcooling is about 10°C.

[0072] FIG. 13 is a flow chart showing the procedure of the control method of this embodiment. As shown in Fig. 13, first, the evaporation temperature determination unit 62a determines whether or not the preset evaporation temperature of the evaporator 8 is equal to or higher than a threshold value (-30°C in this embodiment) (step S21). If the evaporation temperature of the evaporator 8 is not equal to or higher than the threshold value (-30°C) (step S21; NO), the degree of subcooling will not fall below the target value of 10°C, so the control flow ends without opening the bypass pipe 23. On the other hand, if the evaporation temperature of the evaporator 8 is equal to or higher than the threshold value (-30°C) (step S21; YES), the degree of subcooling may fall below the target value of 10°C, so the flow proceeds to step S22.

[0073] In step S22, the outside air temperature threshold calculation unit 65 calculates a threshold used to determine the outside air temperature based on the evaporation temperature of the evaporator 8. For example, the outside air temperature threshold is calculated as follows.

[0074] FIG. 14, like FIG. 7, is a diagram showing the correlation between the outside air temperature and the degree of subcooling for each evaporation temperature (ET) band. As shown in FIG. 14, when the evaporating temperature (ET) is in the temperature range of -15°C to -20°C and when the evaporating temperature (ET) is in the temperature range of -20°C to -25°C, the degree of supercooling falls below the target value of 10°C when the outside air temperature is around 10°C. In step S22, the threshold value of the outside air temperature at which the degree of supercooling is 10°C is accurately determined. For example, when the evaporating temperature (ET) is in the temperature range of -15°C to -20°C, the outside air temperature (about 7°C) at the intersection of the line indicating the correlation and the line indicating the degree of supercooling of 10°C is set as the threshold value used to determine the outside air temperature. Also, when the evaporating temperature (ET) is in the temperature range of -20°C to -25°C, the outside air temperature (about 12°C) at the intersection of the line indicating the correlation and the line indicating the degree of supercooling of 10°C is set as the threshold value used to determine the outside air temperature.

[0075] After step S22, the acquisition unit 61 acquires the outside air temperature from the outside air temperature sensor 51 (step S23). After that, the outside air temperature determination unit 62b determines whether the outside air temperature is equal to or lower than a threshold value (step S24). If the outside air temperature is not equal to or lower than the threshold value (10°C) (step S24; NO), the degree of subcooling does not fall below the target value of 10°C, and the control flow ends without opening the bypass pipe 23. On the other hand, if the outside air temperature is equal to or lower than the threshold value (10°C) (step S24; YES), the valve control unit 63 controls the bypass valve 10 to open the bypass pipe 23 (step S25).

[0076] By step S25, the refrigerant that is originally injected into the middle stage section 33 flows upstream (low pressure side) of the first compression section 32. As a result, similar to the first embodiment, the pressure difference (Δ1) between the high pressure refrigerant (position d) and the low pressure refrigerant (position e) increases, and the degree of subcooling (Δ2) obtained by the subcooling expansion valve 5 can be increased. Therefore, the necessary degree of subcooling can be secured. Through the above procedures, the control flow of the refrigerator 201 related to the opening of the bypass pipe 23 ends. The timing for blocking the bypass pipe 23 may be, for example, when a predetermined time has elapsed since the bypass pipe was opened (step S25), or, similar to the procedure described above, when it is determined that the degree of subcooling has exceeded the target value based on the evaporation temperature or the outside air temperature. The order of the steps can be changed as appropriate. For example, step S23 may be performed before step S24, for example, before step S21. Furthermore, the evaporation temperature does not have to be preset in the control device 260, and may be calculated from the detected value of the evaporation pressure as in the second embodiment.

[0077] (Action and effect) The refrigerator 201 of this embodiment can provide the following advantageous effects.

[0078] In this embodiment, the control device 260 further includes an outside air temperature threshold calculation unit 65. The outside air temperature threshold calculation unit 65 calculates a threshold used to determine the outside air temperature based on the evaporation temperature of the evaporator 8.

[0079] This allows the control device 260 to calculate an accurate threshold value for the outside air temperature. Therefore, the control device 260 can make a determination based on the outside air temperature with higher accuracy. Therefore, the control device 260 can open the bypass pipe 23 at a more appropriate timing.

[0080] <Fourth embodiment> Next, a fourth embodiment will be described with reference to Fig. 15 to Fig. 17. The same components as those in the above-mentioned embodiment will be denoted by the same reference numerals and names, and the description thereof will be omitted as appropriate. The components not described below are assumed to be the same as those in the above-mentioned embodiment.

[0081] As shown in FIG. 15, in a refrigerator 301 of the present embodiment, a sensor 350 includes a high-pressure side pressure sensor 53 and a line temperature sensor .

[0082] (High pressure side pressure sensor) The high-pressure side pressure sensor 53 is provided in the circulation line 21 between the second compression section 34 and the main expansion valve 7, and downstream of the second compression section 34. More specifically, the high-pressure side pressure sensor 53 is provided in the circulation line 21 between the connection section (position d) of the condenser 3 and the injection pipe 22, and upstream of position d. The high-pressure side pressure sensor 53 detects the saturation pressure of the circulation line 21.

[0083] (Line temperature sensor) The line temperature sensor 54 is provided in the circulation line 21 between the subcooling heat exchanger 4 and the main expansion valve 7, and upstream (at position f) of the main expansion valve 7. The line temperature sensor 54 detects the temperature in the circulation line 21.

[0084] (Control device) As shown in FIG. 16, the control device 360 ​​further includes a saturation temperature calculation unit 66 and a degree of subcooling calculation unit 67 in addition to the acquisition unit 61, the determination unit 62, and the valve control unit 63.

[0085] (Saturation temperature calculation part) The saturation temperature calculation unit 66 calculates the saturation temperature in the vicinity of the position d on the circulation line 21 based on the saturation pressure in the vicinity of the position d.

[0086] (Supercooling degree calculation section) The subcooling degree calculation unit 67 calculates the degree of subcooling of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4 from the temperature difference between the calculated saturation temperature and the temperature detected by the line temperature sensor 54.

[0087] (Judgment Department) The determination unit 62 includes a degree of subcooling determination unit 62c and a duration determination unit 62d.

[0088] (Supercooling degree determination section) The subcooling degree determination unit 62c determines whether the calculated subcooling degree is equal to or less than a target value.

[0089] (Duration determination unit) The duration determining unit 62d determines whether the state in which the calculated degree of supercooling is equal to or lower than the target value continues for a predetermined time or longer. The valve control unit 63 controls the bypass valve 10 to open the bypass pipe 23 when the state in which the calculated degree of subcooling is equal to or lower than the target value continues for a predetermined time or longer.

[0090] (Procedure for controlling refrigerator) Next, a method for controlling the refrigerator 301 that opens the bypass pipe 23 at an appropriate timing will be described. In this embodiment, the method for controlling the refrigerator 301 will be described by taking as an example a case where the target value of the degree of subcooling is about 10°C.

[0091] FIG. 17 is a flow chart showing the procedure of the control method of this embodiment. As shown in FIG. 17, first, the acquisition unit 61 acquires the saturation pressure of the connection part (position d) of the condenser 3 and the injection pipe 22 in the circulation line 21 from the high-pressure side pressure sensor 53 (step S31). Next, the evaporation temperature calculation unit calculates the saturation temperature based on the acquired saturation pressure of the circulation line 21 (step S32). After that, the acquisition unit 61 acquires the temperature of the refrigerant between the subcooling heat exchanger 4 and the main expansion valve 7 in the circulation line 21 and upstream of the main expansion valve 7 (position f) (step S33). After step S33, the subcooling degree calculation unit 67 calculates the subcooling degree of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4 from the temperature difference between the calculated saturation temperature and the temperature detected by the line temperature sensor 54 (step S34).

[0092] Thereafter, the subcooling degree determination unit 62c determines whether the calculated subcooling degree is equal to or less than the target value (10°C in this embodiment) (step S35). If the calculated subcooling degree is not equal to or less than the target value (10°C) (step S35; NO), the control flow ends without opening the bypass pipe 23. On the other hand, if the calculated subcooling degree is equal to or less than the target value (10°C) (step S35; YES), the flow proceeds to step S36.

[0093] In step S36, the duration determination unit 62d determines whether the state in which the calculated degree of subcooling is equal to or less than the target value has continued for a predetermined time or more. If the state in which the calculated degree of subcooling is equal to or less than the target value has not continued for the predetermined time or more, the control flow ends without opening the bypass pipe 23. On the other hand, if the state in which the calculated degree of subcooling is equal to or less than the target value has continued for the predetermined time or more (step S36; YES), the valve control unit 63 controls the bypass valve 10 to open the bypass pipe 23 (step S37).

[0094] By step S37, the refrigerant that is originally injected into the middle stage section 33 flows upstream (low pressure side) of the first compression section 32. As a result, similar to the first embodiment, the pressure difference (Δ1) between the high pressure refrigerant (position d) and the low pressure refrigerant (position e) increases, and the degree of subcooling (Δ2) obtained by the subcooling expansion valve 5 can be increased. Therefore, the necessary degree of subcooling can be secured. Through the above procedures, the control flow of the refrigerator 301 related to the opening of the bypass pipe 23 is completed. The timing for blocking the bypass pipe 23 may be, for example, when a predetermined time has elapsed since the bypass pipe was opened (step S37), or when it is determined that the calculated degree of subcooling has exceeded the target value, similar to the procedure described above. In addition, the order of the steps can be changed as appropriate. For example, step S33 may be executed before step S34, for example, before step S31.

[0095] (Action and effect) The refrigerator 301 of this embodiment can provide the following advantageous effects.

[0096] In this embodiment, the sensor 350 includes a high-pressure side pressure sensor 53 and a line temperature sensor 54. The high-pressure side pressure sensor 53 is provided between the second compression section 34 and the main expansion valve 7 in the circulation line 21 and downstream of the second compression section 34, and detects the saturation pressure of the circulation line 21. The line temperature sensor 54 is provided between the subcooling heat exchanger 4 and the main expansion valve 7 in the circulation line 21 and upstream of the main expansion valve 7, and detects the temperature in the circulation line 21. The control device 360 ​​has a saturation temperature calculation unit 66 and a subcooling degree calculation unit 67. The saturation temperature calculation unit 66 calculates the saturation temperature based on the saturation pressure of the circulation line 21. The subcooling degree calculation unit 67 calculates the subcooling degree of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4 from the temperature difference between the calculated saturation temperature and the temperature detected by the line temperature sensor 54. The determination unit 62 has a subcooling degree determination unit 62c and a duration determination unit 62d. The subcooling degree determination unit 62c determines whether the calculated subcooling degree is equal to or less than a target value. The duration determination unit 62d determines whether the state in which the calculated subcooling degree is equal to or less than the target value continues for a predetermined time or more. When the state in which the calculated subcooling degree is equal to or less than the target value continues for a predetermined time or more, the valve control unit 63 controls the bypass valve 10 to open the bypass pipe 23.

[0097] In this embodiment, the control device 360 ​​can calculate the degree of subcooling each time from the physical quantity detected by the sensor 350. This allows the control device 360 ​​to more accurately determine that the degree of subcooling falls below the target value. This allows the control device 360 ​​to open the bypass pipe 23 at a more appropriate timing.

[0098] (Hardware configuration) The control devices 60, 160, 260, and 360 of the above-described embodiments are implemented in a computer as shown in Fig. 18. Fig. 18 is an example of a schematic block diagram showing the configuration of a computer in which the control devices 60, 160, 260, and 360 according to the embodiments are implemented. The computer 1100 includes a processor 1110, a main memory 1120, a storage 1130, and an interface 1140.

[0099] The operation of each functional unit of the control devices 60, 160, 260, 360 is stored in the form of a program in the storage 1130. The processor 1110 reads the program from the storage 1130, loads it in the main memory 1120, and executes the above-mentioned processing in accordance with the program. The processor 1110 also secures a storage area in the main memory 1120 in accordance with the program.

[0100] The program may be for realizing a part of the functions to be performed by the computer 1100. For example, the program may be for realizing the functions by combining with other programs already stored in the storage 1130 or by combining with other programs implemented in other devices. The computer 1100 may also include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions to be realized by the processor 1110 may be realized by the integrated circuit.

[0101] Examples of storage 1130 include a magnetic disk, a magneto-optical disk, and a semiconductor memory. Storage 1130 may be an internal medium directly connected to the bus of computer 1100, or an external medium connected to computer 1100 via interface 1140 or a communication line. In addition, when this program is distributed to computer 1100 via a communication line, computer 1100 that receives the program may load the program in main memory 1120 and execute the above-mentioned processing. Storage 1130 may be a non-transitory tangible storage medium.

[0102] The program may be for realizing part of the above-mentioned functions. Furthermore, the program may be a so-called difference file (difference program) that realizes the above-mentioned functions in combination with other programs already stored in the storage 1130.

[0103] (Other embodiments) Although the embodiments of the present disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do not depart from the gist of the present disclosure are also included. In the above embodiment, the target value of the degree of supercooling is set to 10° C., the threshold value used to determine the evaporation temperature is set to −30° C., and the threshold value used to determine the outside air temperature is set to 10° C. However, the present invention is not limited to this. These target values ​​and threshold values ​​can be changed as appropriate.

[0104] In the above embodiment, the configuration of the refrigeration cycle 2 has been described in a simplified manner, but the present invention is not limited thereto. Other configurations (not shown) may be provided in the refrigeration cycle 2. For example, a tank may be provided between the compressor 30 and the subcooling heat exchanger 4 in the circulation line 21, downstream of the compressor 30.

[0105] In addition, the above embodiment has been described with reference to an example in which the number of compressors 30 provided in the refrigerators 1, 101, 201, and 301 is one, but the present invention is not limited thereto. As shown in FIG. 19, the refrigerator 1 may include a plurality of compressors 30 (two in FIG. 19). The plurality of compressors 30 are connected in series. In this case, the circulation line 21 has a connection line 24. For two adjacent compressors 30, the second compression section 34 of the upstream compressor 30 and the first compression section 32 of the downstream compressor 30 are connected by the connection line 24. The refrigerant discharged from the second compression section 34 of the most downstream compressor 30 is sent to the condenser 3. The injection pipes 22 (22a, 22b, and 22c) are provided between each of the compression sections (32 and 34). Further, the supercooling heat exchanger 4 (4a, 4b, 4c) is provided for each of the injection pipes 22 (22a, 22b, 22c). In the illustrated example, the first supercooling heat exchanger 4a, the second supercooling heat exchanger 4b, and the third supercooling heat exchanger 4c are arranged in series from the downstream side on the circulation line 21 connecting the condenser 3 and the main expansion valve 7. The first injection pipe 22a connected to the upstream compressor 30 passes through the first supercooling heat exchanger 4a and is connected to the middle stage 33 of the compressor 30. The second injection pipe 22b connected between the upstream compressor 30 and the downstream compressor 30 passes through the second supercooling heat exchanger 4b and is connected between the second compression section 34 of the upstream compressor 30 and the first compression section 32 of the downstream compressor 30. Further, the third injection pipe 22c connected to the downstream compressor 30 passes through the third subcooling heat exchanger 4c and is connected to the middle stage 33 of the downstream compressor 30. The bypass pipe 23 and the bypass valve 10 are provided only in the first injection pipe 22a among the multiple injection pipes 22. This modification is applicable not only to the refrigerator 1 of the first embodiment, but also to the refrigerators 101, 201, and 301 of the second to fourth embodiments. Furthermore, the third injection pipe 22c sends the gas refrigerant via the subcooling heat exchanger 4c, but a gas-liquid separator (receiver) may also be used.

[0106] In the above embodiment, the bypass pipe 23 is connected upstream (before) the accumulator 9, but this is not limited thereto. The bypass pipe 23 may be connected downstream of the accumulator 9 and upstream of the first compression section 32. However, connecting the bypass pipe 23 upstream (before) the accumulator 9 is advantageous in that liquid backflow in the accumulator 9 can be prevented.

[0107] <Additional Notes> The refrigerators 1, 101, 201, and 301 and the control methods for the refrigerators described in the respective embodiments can be understood, for example, as follows.

[0108] (1) A refrigerator 1, 101, 201, 301 according to a first aspect includes a refrigeration cycle 2, a sensor 50, 150, 350 for detecting a physical quantity related to the refrigeration cycle 2, and a control device 60, 160, 260, 360 for controlling the refrigeration cycle 2. The refrigeration cycle 2 includes a circulation line 21 for circulating a refrigerant, a first compression section 32 provided in the circulation line 21 for compressing a low-pressure refrigerant supplied from an outside to generate an intermediate-pressure refrigerant, a middle section 33 provided in the circulation line 21 for discharging the intermediate-pressure refrigerant generated in the first compression section 32, and a control device 60, 160, 260, 360 for controlling the refrigeration cycle 2. a second compression section 34 provided in the circulation line 21 and compressing an intermediate-pressure refrigerant in the middle stage section 33 to generate a high-pressure refrigerant; a condenser 3 for condensing the high-pressure refrigerant generated in the second compression section 34; an injection pipe 22 branching from a downstream side of the condenser 3 in the circulation line 21 and returning the refrigerant that has passed through the condenser 3 to the middle stage section 33; a supercooling heat exchanger 4 for supercooling the refrigerant that has passed through the condenser 3 and flows through the circulation line 21 by exchanging heat with the refrigerant that flows through the injection pipe 22; a subcooling expansion valve 5 provided upstream of the subcooling heat exchanger 4 and expanding the refrigerant flowing through the injection pipe 22 before being supplied to the subcooling heat exchanger 4; a main expansion valve 7 provided in the circulation line 21 and expanding the refrigerant that has passed through the subcooling heat exchanger 4; an evaporator 8 provided downstream of the main expansion valve 7 in the circulation line 21 and evaporating the refrigerant that has passed through the main expansion valve 7; a bypass pipe 23 that guides the refrigerant flowing through the injection pipe 22 to a position upstream of the injection pipe 22, and a bypass valve 10 that is provided in the bypass pipe 23 and opens and closes the bypass pipe 23. The control device 60, 160, 260, 360 has an acquisition unit 61 that acquires a physical quantity related to the refrigeration cycle 2, a determination unit 62 that determines whether or not the degree of subcooling of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4 falls below a target value based on the physical quantity related to the refrigeration cycle 2, and a determination unit 63 that, when the degree of subcooling of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4 falls below the target value,and a valve control unit 63 that controls the bypass valve 10 to open the bypass pipe 23.

[0109] In this embodiment, the control device 60, 160, 260, 360 judges whether the degree of supercooling falls below the target value based on the physical quantity related to the refrigeration cycle 2. When the degree of supercooling falls below the target value, the control device 60, 160, 260, 360 can control the bypass valve 10 to open the bypass pipe 23. Then, the refrigerant that is originally injected into the middle stage section 33 flows upstream (low pressure side) of the first compression section 32. As a result, the pressure difference between the high pressure refrigerant that passes through the circulation line 21 and is supplied to the supercooling heat exchanger 4 and the low pressure refrigerant that passes through the injection pipe 22 and is supplied to the supercooling heat exchanger 4 increases, and the flow rate of the refrigerant throttled and expanded by the supercooling expansion valve 5 can be secured. Therefore, the degree of supercooling obtained by the supercooling expansion valve 5 can be increased, and the required degree of supercooling can be secured.

[0110] (2) The refrigeration machine 1, 101, 201 of the second aspect is the refrigeration machine 1, 101, 201 of the first aspect, wherein the sensor 50, 150 includes an outside air temperature sensor 51 that detects the outside air temperature, the judgment unit 62 has an evaporation temperature judgment unit 62a that judges whether the evaporation temperature of the evaporator 8 is equal to or higher than a threshold value, and an outside air temperature judgment unit 62b that judges whether the outside air temperature is equal to or lower than the threshold value, and the valve control unit 63 may control the bypass valve 10 to open the bypass pipe 23 when the evaporation temperature of the evaporator 8 is equal to or higher than the threshold value and the outside air temperature is equal to or lower than the threshold value.

[0111] The higher the evaporation temperature is and the lower the outside air temperature is, the smaller the degree of subcooling tends to be. In this embodiment, the control device 60, 160, 260 performs two-stage judgment based on the evaporation temperature and the outside air temperature, thereby enabling the bypass pipe 23 to be opened efficiently and at a more appropriate timing.

[0112] (3) The refrigerator 1, 201 according to a third aspect is the refrigerator 1, 201 according to the second aspect, and the evaporation temperature of the evaporator 8 may be set in advance in the control device 60, 260.

[0113] This makes it possible to eliminate the need for a step of detecting or calculating the evaporation temperature of the evaporator 8.

[0114] (4) A refrigeration machine 101 according to a fourth aspect is the refrigeration machine 101 according to the second aspect, wherein the sensor 150 is provided in the circulation line 21 between the main expansion valve 7 and the first compression section 32 and upstream of the first compression section 32, and further includes a low-pressure side pressure sensor 52 that detects an evaporation pressure of the evaporator 8, and the control device 160 may further include an evaporation temperature calculation unit 64 that calculates an evaporation temperature of the evaporator 8 based on the evaporation pressure of the evaporator 8.

[0115] This allows the control device 160 to calculate an accurate evaporation temperature, thereby enabling the control device 160 to perform determination based on the evaporation temperature with higher accuracy.

[0116] (5) A refrigerator 201 according to a fifth aspect is the refrigerator 201 according to any one of the second to fourth aspects, and the control device 260 may further have an outside air temperature threshold calculation unit 65 that calculates a threshold used to determine the outside air temperature based on the evaporation temperature of the evaporator 8.

[0117] This allows the control device 260 to calculate an accurate threshold value for the outside air temperature, thereby enabling the control device 260 to make a determination based on the outside air temperature with higher accuracy.

[0118] (6) A refrigerator 301 according to a sixth aspect is the refrigerator 301 according to the first aspect, wherein the sensor 350 includes a high-pressure side pressure sensor 53 that is provided in the circulation line 21 between the second compression section 34 and the main expansion valve 7 and downstream of the second compression section 34 and detects a saturation pressure of the circulation line 21, and a line temperature sensor 54 that is provided in the circulation line 21 between the subcooling heat exchanger 4 and the main expansion valve 7 and upstream of the main expansion valve 7 and detects a temperature in the circulation line 21, and the control device 360 ​​includes a saturation temperature calculation unit 6 that calculates a saturation temperature based on the saturation pressure of the circulation line 21. and a subcooling degree calculation unit 67 that calculates the degree of subcooling of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4 from the temperature difference between the calculated saturation temperature and the temperature detected by the line temperature sensor 54, the judgment unit 62 has a subcooling degree judgment unit 62c that judges whether the calculated subcooling degree is equal to or lower than a target value, and a duration judgment unit 62d that judges whether the state in which the calculated subcooling degree is equal to or lower than the target value continues for a predetermined time or more, and the valve control unit 63 may control the bypass valve 10 to open the bypass pipe 23 when the state in which the calculated subcooling degree is equal to or lower than the target value continues for a predetermined time or more.

[0119] In this embodiment, the control device 360 ​​can calculate the degree of subcooling each time from the physical quantity detected by the sensor 350. This allows the control device 360 ​​to more accurately determine that the degree of subcooling falls below the target value.

[0120] (7) A control method for a refrigerator according to a seventh aspect is a control method for a refrigerator 1, 101, 201, 301 including a refrigeration cycle 2, a sensor 50, 150, 350 for detecting a physical quantity related to the refrigeration cycle 2, and a control device 60, 160, 260, 360 for controlling the refrigeration cycle 2. The refrigeration cycle 2 includes a circulation line 21 for circulating a refrigerant, a first compression unit 32 provided in the circulation line 21 for compressing a low-pressure refrigerant supplied from an outside to generate an intermediate-pressure refrigerant, and a discharge compressor 33 for discharging the intermediate-pressure refrigerant generated by the first compression unit 32. a second compression section 34 provided in the circulation line 21 and compressing an intermediate-pressure refrigerant in the middle stage section 33 to generate a high-pressure refrigerant; a condenser 3 for condensing the high-pressure refrigerant generated in the second compression section 34; an injection pipe 22 branching from a downstream side of the condenser 3 in the circulation line 21 and returning the refrigerant that has passed through the condenser 3 to the middle stage section 33; a supercooling heat exchanger 4 for supercooling the refrigerant that has passed through the condenser 3 and flows through the circulation line 21 by exchanging heat with the refrigerant that flows through the injection pipe 22; a subcooling expansion valve 5 provided upstream of the subcooling heat exchanger 4 in the circulation line 21 and expanding the refrigerant flowing through the injection pipe 22 before being supplied to the subcooling heat exchanger 4; a main expansion valve 7 provided in the circulation line 21 and expanding the refrigerant that has passed through the subcooling heat exchanger 4; an evaporator 8 provided downstream of the main expansion valve 7 in the circulation line 21 and evaporating the refrigerant that has passed through the main expansion valve 7; and a second compression section 32 branching off from the injection pipe 22 downstream of the subcooling heat exchanger 4 and connecting the evaporator 8 and the first compression section 32 in the circulation line 21. a bypass pipe 23 for guiding the refrigerant flowing through the injection pipe 22 to an upstream side of the first compression section 32, and a bypass valve 10 provided in the bypass pipe 23 for opening and closing the bypass pipe 23, wherein the control devices 60, 160, 260, 360 acquire a physical quantity related to the refrigeration cycle 2; and the control devices 60, 160, 260, 360 determine whether or not a degree of subcooling of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4 falls below a target value based on the physical quantity related to the refrigeration cycle 2.260, 360 include a step of controlling the bypass valve 10 to open the bypass pipe 23 when the degree of subcooling of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4 falls below a target value.

[0121] (8) A method of controlling a refrigerator according to an eighth aspect is the method of controlling a refrigerator according to the seventh aspect, wherein the sensor 50, 150 includes an outside air temperature sensor 51 for detecting an outside air temperature, and may further include the steps of the control device 60, 160, 260 determining whether or not an evaporation temperature of the evaporator 8 is equal to or higher than a threshold value, the control device 60, 160, 260 determining whether or not the outside air temperature is equal to or lower than a threshold value, and the control device 60, 160, 260 controlling the bypass valve 10 to open the bypass pipe 23 when the evaporation temperature of the evaporator 8 is equal to or higher than the threshold value and the outside air temperature is equal to or lower than the threshold value.

[0122] (9) A method for controlling a refrigerator according to a ninth aspect is the method for controlling a refrigerator according to the eighth aspect, wherein the evaporation temperature of the evaporator 8 may be set in advance in the control device 60, 260.

[0123] (10) A method of controlling a refrigerator according to a tenth aspect is the method of controlling a refrigerator according to the eighth aspect, wherein the sensor 150 is provided in the circulation line 21 between the main expansion valve 7 and the first compression section 32 and upstream of the first compression section 32, and further includes a low-pressure side pressure sensor 52 that detects an evaporation pressure of the evaporator 8, and the control device 160 may further include a step of calculating an evaporation temperature of the evaporator 8 based on the evaporation pressure of the evaporator 8.

[0124] (11) A method of controlling a refrigerator according to an eleventh aspect is a method of controlling the refrigerator 201 according to any one of the eighth to tenth aspects, and may further include a step in which the control device 260 calculates a threshold value used to determine the outside air temperature based on the evaporation temperature of the evaporator 8.

[0125] (12) A control method for a refrigerator according to a twelfth aspect is a control method for the refrigerator 301 according to the seventh aspect, wherein the sensor 350 includes a high-pressure side pressure sensor 53 that is provided in the circulation line 21 between the second compression section 34 and the main expansion valve 7 and downstream of the second compression section 34 and detects a saturation pressure of the circulation line 21, and a line temperature sensor 54 that is provided in the circulation line 21 between the subcooling heat exchanger 4 and the main expansion valve 7 and upstream of the main expansion valve 7 and detects a temperature in the circulation line 21, and the control device 360 ​​calculates a saturation temperature based on the saturation pressure of the circulation line 21; The method may further include a step in which the control device 360 ​​calculates the degree of subcooling of the refrigerant in the circulation line 21 that has passed through the subcooling heat exchanger 4 from the temperature difference between the calculated saturation temperature and the temperature detected by the line temperature sensor 54; a step in which the control device 360 ​​determines whether the calculated degree of subcooling is equal to or lower than a target value; a step in which the control device 360 ​​determines whether the state in which the calculated degree of subcooling is equal to or lower than the target value has continued for a predetermined time or more; and a step in which the control device 360 ​​controls the bypass valve 10 to open the bypass pipe 23 when the state in which the calculated degree of subcooling is equal to or lower than the target value has continued for a predetermined time or more. [Explanation of symbols]

[0126] 1...refrigerating machine 2...refrigeration cycle 3...condenser 4...subcooling heat exchanger 5...subcooling expansion valve 6...check valve 7...main expansion valve 8...evaporator 9...accumulator 10...bypass valve 20...refrigerant line 21...circulation line 22...injection pipe 23...bypass pipe 30...compressor 31...casing 32...first compression section 33...middle stage section 34...second compression section 50...sensor 51...outside air temperature sensor 60...control device 61...acquisition section 62...determination section 62a...evaporation temperature determination section 62b...outside air temperature determination section 63...valve control section 101...refrigeration machine 150...sensor 52...low pressure side pressure sensor 160...control device 64...evaporation temperature calculation unit 201...refrigeration machine 260...control device 65...outside air temperature threshold calculation unit 301: Refrigeration machine 350: Sensor 53: High pressure side pressure sensor 54: Line temperature sensor 360: Control device 62c: Subcooling degree determination unit 62d: Duration determination unit 66: Saturation temperature calculation unit 67: Subcooling degree calculation unit 24: Connection line 22a: First injection tube 22b: Second injection tube 1100... computer 1110... processor 1120... main memory 1130... storage 1140... interface 4a...first subcooling heat exchanger 4b...second subcooling heat exchanger 4c...third subcooling heat exchanger 22a...first injection tube 22b...second injection tube 22c...third injection tube

Claims

1. The refrigeration cycle, A sensor for detecting a physical quantity related to the refrigeration cycle; A control device for controlling the refrigeration cycle; Equipped with The refrigeration cycle includes: A circulation line for circulating a refrigerant; a first compression section provided in the circulation line and compressing a low-pressure refrigerant supplied from an outside to generate an intermediate-pressure refrigerant; a middle stage portion provided in the circulation line and into which the intermediate-pressure refrigerant generated in the first compression portion is discharged; a second compression section provided in the circulation line and compressing the intermediate-pressure refrigerant in the middle stage section to generate a high-pressure refrigerant; a condenser that condenses the high-pressure refrigerant generated in the second compression section; an injection pipe that branches off from the circulation line downstream of the condenser and returns the refrigerant that has passed through the condenser to the middle section; a subcooling heat exchanger that subcools the refrigerant that has passed through the condenser and is flowing through the circulation line by exchanging heat with the refrigerant that is flowing through the injection pipe; a subcooling expansion valve provided upstream of the subcooling heat exchanger in the injection pipe, for expanding the refrigerant flowing through the injection pipe before the refrigerant is supplied to the subcooling heat exchanger; A main expansion valve that is provided in the circulation line and expands the refrigerant that has passed through the subcooling heat exchanger; an evaporator provided downstream of the main expansion valve in the circulation line and configured to evaporate the refrigerant that has passed through the main expansion valve; a bypass pipe that branches off from the injection pipe downstream of the subcooling heat exchanger and guides the refrigerant flowing through the injection pipe to a portion of the circulation line between the evaporator and the first compression unit and upstream of the first compression unit; a bypass valve provided in the bypass pipe for opening and closing the bypass pipe; having The control device includes: An acquisition unit that acquires a physical quantity related to the refrigeration cycle; a determination unit that determines whether or not a degree of subcooling of the refrigerant in the circulation line that has passed through the subcooling heat exchanger is below a target value based on a physical quantity related to the refrigeration cycle; A valve control unit that controls the bypass valve to open the bypass pipe when the degree of subcooling of the refrigerant in the circulation line that has passed through the subcooling heat exchanger falls below a target value; A refrigerator having the above structure.

2. the sensor includes an outside air temperature sensor for detecting an outside air temperature; The determination unit is an evaporation temperature determination unit that determines whether an evaporation temperature of the evaporator is equal to or higher than a threshold; an outside air temperature determination unit that determines whether the outside air temperature is equal to or lower than a threshold; having The refrigerator according to claim 1 , wherein the valve control unit controls the bypass valve to open the bypass pipe when an evaporation temperature of the evaporator is equal to or higher than a threshold and an outside air temperature is equal to or lower than a threshold.

3. The refrigerator according to claim 2 , wherein an evaporation temperature of the evaporator is preset in the control device.

4. The sensor further includes a low-pressure side pressure sensor that is provided in the circulation line between the main expansion valve and the first compression section and upstream of the first compression section and detects an evaporation pressure of the evaporator. The refrigerator according to claim 2 , wherein the control device further comprises an evaporation temperature calculation unit that calculates an evaporation temperature of the evaporator based on an evaporation pressure of the evaporator.

5. The control device includes: The refrigerator according to claim 2 , further comprising an outside air temperature threshold calculation unit that calculates a threshold used for determining an outside air temperature based on an evaporation temperature of the evaporator.

6. The sensor includes: a high-pressure side pressure sensor that is provided in the circulation line between the second compression section and the main expansion valve and downstream of the second compression section and detects a saturation pressure of the circulation line; a line temperature sensor provided in the circulation line between the subcooling heat exchanger and the main expansion valve and upstream of the main expansion valve, the line temperature sensor detecting a temperature in the circulation line; Including, The control device includes: a saturation temperature calculation unit that calculates a saturation temperature based on the saturation pressure of the circulation line; a subcooling degree calculation unit that calculates a subcooling degree of the refrigerant in the circulation line that has passed through the subcooling heat exchanger from a temperature difference between the calculated saturation temperature and the temperature detected by the line temperature sensor; having The determination unit is a subcooling degree determination unit that determines whether the calculated subcooling degree is equal to or less than a target value; a duration determination unit that determines whether a state in which the calculated degree of supercooling is equal to or lower than a target value continues for a predetermined time or more; having 2. The refrigerator according to claim 1, wherein the valve control unit controls the bypass valve to open the bypass pipe when a state in which the calculated degree of subcooling is equal to or lower than a target value continues for a predetermined time or longer.

7. A method for controlling a refrigerator including a refrigeration cycle, a sensor for detecting a physical quantity related to the refrigeration cycle, and a control device for controlling the refrigeration cycle, comprising: The refrigeration cycle includes: A circulation line for circulating a refrigerant; a first compression section provided in the circulation line and compressing a low-pressure refrigerant supplied from an outside to generate an intermediate-pressure refrigerant; a middle stage portion provided in the circulation line and into which the intermediate-pressure refrigerant generated in the first compression portion is discharged; a second compression section provided in the circulation line and compressing the intermediate-pressure refrigerant in the middle stage section to generate a high-pressure refrigerant; a condenser that condenses the high-pressure refrigerant generated in the second compression section; an injection pipe that branches off from the circulation line downstream of the condenser and returns the refrigerant that has passed through the condenser to the middle section; a subcooling heat exchanger that subcools the refrigerant that has passed through the condenser and is flowing through the circulation line by exchanging heat with the refrigerant that is flowing through the injection pipe; a subcooling expansion valve provided upstream of the subcooling heat exchanger in the injection pipe, for expanding the refrigerant flowing through the injection pipe before the refrigerant is supplied to the subcooling heat exchanger; A main expansion valve that is provided in the circulation line and expands the refrigerant that has passed through the subcooling heat exchanger; an evaporator provided downstream of the main expansion valve in the circulation line and configured to evaporate the refrigerant that has passed through the main expansion valve; a bypass pipe that branches off from the injection pipe downstream of the subcooling heat exchanger and guides the refrigerant flowing through the injection pipe to a portion of the circulation line between the evaporator and the first compression unit and upstream of the first compression unit; a bypass valve provided in the bypass pipe for opening and closing the bypass pipe; having The control device acquires a physical quantity related to the refrigeration cycle; The control device determines whether or not a degree of subcooling of the refrigerant in the circulation line that has passed through the subcooling heat exchanger falls below a target value based on a physical quantity related to the refrigeration cycle; and when a degree of subcooling of the refrigerant in the circulation line that has passed through the subcooling heat exchanger falls below a target value, the control device controls the bypass valve to open the bypass pipe.

8. the sensor includes an outside air temperature sensor for detecting an outside air temperature; The control device determines whether an evaporation temperature of the evaporator is equal to or higher than a threshold value; The control device determines whether an outside air temperature is equal to or lower than a threshold value; The method for controlling a refrigerator according to claim 7, further comprising the step of: controlling the bypass valve to open the bypass pipe when an evaporation temperature of the evaporator is equal to or higher than a threshold value and an outside air temperature is equal to or lower than a threshold value, by the control device.

9. The method for controlling a refrigerator according to claim 8 , wherein an evaporation temperature of the evaporator is preset in the control device.

10. The sensor further includes a low-pressure side pressure sensor that is provided in the circulation line between the main expansion valve and the first compression section and upstream of the first compression section and detects an evaporation pressure of the evaporator. The method for controlling a refrigerator according to claim 8 , further comprising the step of: the control device calculating an evaporation temperature of the evaporator based on an evaporation pressure of the evaporator.

11. The method for controlling a refrigerator according to claim 8 , further comprising the step of: the control device calculating a threshold value used for determining an outside air temperature based on an evaporation temperature of the evaporator.

12. The sensor includes: a high-pressure side pressure sensor that is provided in the circulation line between the second compression section and the main expansion valve and downstream of the second compression section and detects a saturation pressure of the circulation line; a line temperature sensor provided in the circulation line between the subcooling heat exchanger and the main expansion valve and upstream of the main expansion valve, the line temperature sensor detecting a temperature in the circulation line; Including, The control device calculates a saturation temperature based on a saturation pressure of the circulation line; The control device calculates a degree of subcooling of the refrigerant in the circulation line that has passed through the subcooling heat exchanger from a temperature difference between the calculated saturation temperature and the temperature detected by the line temperature sensor; A step of the control device determining whether the calculated degree of subcooling is equal to or less than a target value; A step of determining whether or not a state in which the calculated degree of subcooling is equal to or lower than a target value continues for a predetermined time or more by the control device; 8. The method of controlling a refrigerator according to claim 7, further comprising: when a state in which the calculated degree of subcooling is equal to or lower than a target value continues for a predetermined time or more, the control device controls the bypass valve to open the bypass pipe.

Images