Cooling device

Abstract

To provide a cooling device that can control the evaporation temperature of a refrigerant in an evaporator to an optimum value in accordance with an operation state of the cooling device.SOLUTION: In this cooling device 100, one expansion valve 13 is provided in each of a plurality of branch refrigerant flow paths 16. One evaporator 14 is provided such that the plurality of branch refrigerant flow paths 16 passes therethrough so as to cool the same cooling region 110.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cooling device. [Background technology]

[0002] BACKGROUND ART Conventionally, cooling devices have been known in which a refrigerant flow path includes a plurality of branch refrigerant flow paths (see, for example, Patent Document 1).

[0003] The above-mentioned Patent Document 1 describes a cooling device including a plurality of paths (branched refrigerant paths) in which a refrigerant path branches into a plurality of paths downstream of an expansion valve and upstream of an evaporator, and merges downstream of the evaporator and upstream of a compressor. In the cooling device described in the above-mentioned Patent Document 1, the refrigerant path is branched into a plurality of paths by a distributor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-232011 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the cooling device described in Patent Document 1, as described above, the refrigerant flow path is branched into multiple paths (branch refrigerant flow paths) by a distributor, so it is not possible to individually adjust the refrigerant flow rate for each of the multiple branch refrigerant flow paths. In this case, it is relatively difficult to control the evaporation temperature of the refrigerant in the evaporator to an optimal value that matches the operating conditions of the cooling device. For this reason, there is a demand for a cooling device that can adjust the refrigerant flow rate for each of the multiple branch refrigerant flow paths and control the evaporation temperature of the refrigerant in the evaporator to an optimal value that matches the operating conditions of the cooling device.

[0006] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide a cooling device that can control the evaporation temperature of the refrigerant in the evaporator to an optimal value that matches the operating conditions of the cooling device. [Means for solving the problem]

[0007] In order to achieve the above object, a cooling device according to one aspect of the present invention includes a compressor that compresses a refrigerant, a condenser that condenses the refrigerant compressed by the compressor, an expansion valve that expands the refrigerant condensed by the condenser to adjust the flow rate of the refrigerant, an evaporator that evaporates the refrigerant expanded by the expansion valve, and a refrigerant flow path through which the refrigerant flows, the refrigerant flow path being branched into a plurality of branch refrigerant flow paths downstream of the condenser and upstream of the expansion valve, and configured so that the plurality of branch refrigerant flow paths join together downstream of the evaporator and upstream of the compressor, one expansion valve is provided for each of the plurality of branch refrigerant flow paths, and one evaporator is provided so that the plurality of branch refrigerant flow paths pass through the evaporator so as to cool the same cooling region, or one evaporator is provided so that the same cooling region is cooled.

[0008] In a cooling device according to one aspect of the present invention, as described above, one expansion valve is provided for each of the plurality of branch refrigerant flow paths, and one evaporator is provided for each of the plurality of branch refrigerant flow paths so as to cool the same cooling region, or one evaporator is provided for each of the plurality of branch refrigerant flow paths so as to cool the same cooling region. This allows the expansion valves provided for each of the plurality of branch refrigerant flow paths to individually adjust the refrigerant flow rate for each of the plurality of branch refrigerant flow paths. As a result, the evaporation temperature of the refrigerant in the evaporator can be controlled to an optimal value suited to the operating conditions of the cooling device. Furthermore, pressure loss when the refrigerant passes through the evaporator can be reduced.

[0009] The cooling device according to the above aspect preferably further includes a control unit that individually controls the opening and closing degrees of each of the plurality of expansion valves based on the degree of superheat, which is the difference between the evaporator inlet temperature and the evaporator outlet temperature, in each of the plurality of branch refrigerant flow paths so as to cool the same cooling region. With this configuration, the control unit controls the opening and closing degrees of the expansion valves provided in each of the plurality of branch refrigerant flow paths, making it possible to easily individually adjust the flow rate of the refrigerant for each of the plurality of branch refrigerant flow paths.

[0010] In the above-described configuration including a control unit that individually controls the opening and closing degrees of each of the plurality of expansion valves based on the degree of superheat in each of the plurality of branch refrigerant flow paths, the control unit preferably further includes an inlet temperature sensor provided in at least one of the plurality of branch refrigerant flow paths to detect the inlet temperature of the evaporator, and a plurality of outlet temperature sensors provided in each of the plurality of branch refrigerant flow paths to detect the outlet temperature of the evaporator. With this configuration, the inlet temperature sensor provided in at least one of the plurality of branch refrigerant flow paths and the plurality of outlet temperature sensors provided in each of the plurality of branch refrigerant flow paths can easily individually obtain the degree of superheat, which is the difference between the inlet temperature of the evaporator and the outlet temperature of the evaporator, in each of the plurality of branch refrigerant flow paths. Note that, since the inlet temperature of the evaporator is approximately the same for all of the plurality of branch refrigerant flow paths, it is sufficient that the inlet temperature sensor is provided in at least one of the plurality of branch refrigerant flow paths.

[0011] In the cooling device according to the above aspect, the cooling region is preferably a freezer compartment for freezing commodities therein, and the refrigerant is R1234yf. Here, in the Mollier diagram (pressure-specific entropy diagram) for R1234yf, the isotherm at a temperature near -30°C has a relatively dense pressure scale compared to other refrigerants used to cool the freezer compartment. In other words, when R1234yf is used to cool the freezer compartment, it is relatively difficult to control the evaporation temperature to a target value. Therefore, with the above configuration, the evaporation temperature of the refrigerant in the evaporator can be effectively controlled to an optimal value suited to the operating conditions of the cooling device. Furthermore, because R1234yf has a lower density than other refrigerants used to cool the freezer compartment, if the pressure loss when passing through the evaporator is large, the refrigeration capacity of the cooling device will be significantly reduced. Therefore, with the above configuration, the pressure loss when the refrigerant passes through the evaporator can be effectively suppressed.

[0012] The cooling device according to the above aspect preferably further includes a plurality of capillary tubes arranged between the condenser and the evaporator in each of the plurality of branch refrigerant flow paths. With this configuration, the refrigerant can be expanded (reduced in pressure) in each of the plurality of branch refrigerant flow paths due to the flow path resistance of the capillary tubes. This reduces the amount of expansion of the refrigerant by the expansion valve in each of the plurality of branch refrigerant flow paths, thereby reducing the load acting on the expansion valve.

[0013] The cooling device according to the above aspect is preferably used in a vending machine or a showcase. With this configuration, the evaporation temperature of the refrigerant in the evaporator in the vending machine or showcase can be controlled to an optimum value suited to the operating conditions of the cooling device. Furthermore, in the vending machine or showcase, pressure loss when the refrigerant passes through the evaporator can be suppressed.

[0014] The cooling device according to the above aspect preferably further includes a control unit that controls the compressor frequency based on the evaporation temperature of the refrigerant in the evaporator. The control unit is configured to control the compressor frequency while gradually lowering the target evaporation temperature as the temperature difference between the evaporator inlet and the evaporator outlet in the cooling region decreases. With this configuration, when the evaporation temperature of the refrigerant in the evaporator is relatively high, the amount of heat removed from the cooled fluid in the evaporator is relatively large. This reduces the time required to cool the cooling region compared to when the target evaporation temperature of the refrigerant in the evaporator is not changed (always at the final target value). Furthermore, because the target evaporation temperature is gradually lowered, control by the control unit is simplified, unlike when the target evaporation temperature is continuously lowered, and the control burden on the control unit can be reduced.

[0015] In the above-described configuration in which the control unit controls the compressor frequency while gradually lowering the target value of the evaporation temperature as the inlet / outlet temperature difference decreases, the control unit is preferably configured to: when the inlet / outlet temperature difference decreases to a first threshold, lower the target value of the evaporation temperature to a first target value and control the compressor frequency so that the evaporation temperature becomes the first target value; and when the inlet / outlet temperature difference decreases to a second threshold smaller than the first threshold, lower the target value of the evaporation temperature to a second target value smaller than the first target value and control the compressor frequency so that the evaporation temperature becomes the second target value. With this configuration, it is possible to easily control the compressor frequency while gradually lowering the target value of the evaporation temperature as the inlet / outlet temperature difference between the evaporator inlet and the evaporator outlet in the cooling region decreases. [Effects of the Invention]

[0016] According to the present invention, as described above, it is possible to provide a cooling device that can control the evaporation temperature of the refrigerant in the evaporator to an optimum value that matches the operating conditions of the cooling device. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram showing the overall configuration of a cooling device according to a first embodiment of the present invention. [Figure 2] FIG. 3 is a diagram showing a control flow of a compressor in the cooling device according to the first embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing a control flow of an expansion valve in the cooling device according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing the overall configuration of a cooling device according to a second embodiment of the present invention. [Figure 5] FIG. 6 is a diagram for explaining the control of the target value of the evaporation temperature, the compressor, and the expansion valve in the cooling device according to the second embodiment of the present invention. [Figure 6] FIG. 1 is a diagram showing the overall configuration of a cooling device according to a first modified example of the present invention. [Figure 7] FIG. 10 is a diagram showing the overall configuration of a cooling device according to a second modified example of the present invention. [Figure 8] FIG. 10 is a diagram showing the overall configuration of a cooling device according to a third modified example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings.

[0019] [First embodiment] The configuration of a cooling device 100 according to a first embodiment of the present invention will be described with reference to Figures 1 to 3. The cooling device 100 is used in a vending machine or a showcase.

[0020] (Overall configuration of the cooling device) As shown in FIG. 1, the cooling device 100 is a device for cooling a cooling region 110. The cooling region 110 is a freezer compartment for freezing commodities therein. The cooling device 100 includes a compressor 11, a condenser 12, an expansion valve 13, an evaporator 14, and a refrigerant flow path 15. The compressor 11, the condenser 12, the expansion valve 13, and the evaporator 14 are connected in this order by the refrigerant flow path 15. A refrigerant flows through the refrigerant flow path 15. The refrigerant is R1234yf.

[0021] The compressor 11 compresses the sucked refrigerant (gas). The compressor 11 discharges the compressed refrigerant (gas) to the high-pressure side (condenser 12 side). The refrigerant (gas) compressed by the compressor 11 flows into the condenser 12, which is arranged downstream of the compressor 11, via a refrigerant flow path 15. The compressor 11 is configured to be able to adjust the amount of refrigerant discharged to the condenser 12 side by adjusting the frequency of an inverter (not shown) for driving the compressor 11. In the following description, the frequency of the inverter may be referred to as the "frequency of the compressor 11."

[0022] The condenser 12 condenses the refrigerant (gas) compressed by the compressor 11. The refrigerant (liquid) condensed by the condenser 12 flows through a refrigerant flow path 15 and into an expansion valve 13 arranged downstream of the condenser 12.

[0023] Expansion valve 13 adjusts the flow rate of the refrigerant by expanding the refrigerant (liquid) condensed by condenser 12. The refrigerant (gas-liquid two-phase) expanded by expansion valve 13 flows into evaporator 14, which is located downstream of expansion valve 13, via refrigerant flow path 15. Expansion valve 13 is configured to be able to change its opening / closing degree (opening degree) in order to adjust the flow rate of the refrigerant flowing into evaporator 14.

[0024] The evaporator 14 evaporates the refrigerant (gas-liquid two-phase) expanded by the expansion valve 13 and flowing in from the expansion valve 13 side. The evaporation of the refrigerant in the evaporator 14 cools the cooling region 110 in which the evaporator 14 is arranged. The refrigerant (gas) evaporated by the evaporator 14 flows into the compressor 11 via the refrigerant flow path 15.

[0025] (Multiple branched refrigerant flow paths) The refrigerant flow path 15 is branched into a plurality (two) of branched refrigerant flow paths 16 (first branch refrigerant flow path 16a and second branch refrigerant flow path 16b) downstream of the condenser 12 and upstream of the expansion valve 13, and includes a plurality (two) of branch refrigerant flow paths 16 that merge downstream of the evaporator 14 and upstream of the compressor 11. One expansion valve 13 is provided for each of the plurality (two) of branch refrigerant flow paths 16. The first branch refrigerant flow path 16a and the second branch refrigerant flow path 16b are provided with a first expansion valve 13a and a second expansion valve 13b, respectively. One evaporator 14 is provided so that the plurality (two) of branch refrigerant flow paths 16 (first branch refrigerant flow path 16a and second branch refrigerant flow path 16b) pass through it to cool the same cooling region 110.

[0026] The cooling device 100 includes a plurality of capillary tubes 17 (first capillary tube 17a and second capillary tube 17b) arranged between the condenser 12 and the evaporator 14 in each of a plurality (two) of branch refrigerant flow paths 16 (first branch refrigerant flow path 16a and second branch refrigerant flow path 16b).

[0027] (Compressor and expansion valve control) The cooling device 100 includes an inlet temperature sensor 21, an outlet temperature sensor 22, a cooling region temperature sensor 23, and a control unit 30.

[0028] The inlet temperature sensor 21 detects the inlet temperature of the evaporator 14. The inlet temperature of the evaporator 14 detected by the inlet temperature sensor 21 is output to the control unit 30. The inlet temperature sensor 21 is provided in the first branch refrigerant flow path 16a, but not in the second branch refrigerant flow path 16b. That is, the inlet temperature sensor 21 is provided in at least one of the multiple (two) branch refrigerant flow paths 16 (the first branch refrigerant flow path 16a and the second branch refrigerant flow path 16b).

[0029] The outlet temperature sensor 22 detects the outlet temperature of the evaporator 14. The outlet temperature of the evaporator 14 detected by the outlet temperature sensor 22 is output to the control unit 30. One outlet temperature sensor 22 is provided for each of the multiple (two) branch refrigerant flow paths 16 (first branch refrigerant flow path 16a and second branch refrigerant flow path 16b). That is, the cooling device 100 includes multiple outlet temperature sensors 22 (first outlet temperature sensor 22a and second outlet temperature sensor 22b).

[0030] The cooling region temperature sensor 23 detects the temperature in the cooling region 110. The temperature in the cooling region 110 detected by the cooling region temperature sensor 23 is output to the control unit 30.

[0031] The control unit 30 individually controls the opening and closing degrees of each of the expansion valves 13 based on the degree of superheat, which is the difference between the inlet temperature of the evaporator 14 and the outlet temperature of the evaporator 14, in each of the branch refrigerant flow paths 16 so as to cool the same cooling region 110. Specifically, the control unit 30 individually controls the opening and closing degrees of each of the expansion valves 13 so as to increase the opening degrees of the expansion valves 13 in the branch refrigerant flow paths 16 whose superheat degrees are greater than a target value and decrease the opening degrees of the expansion valves 13 in the branch refrigerant flow paths 16 whose superheat degrees are less than the target value. The control unit 30 individually controls the opening and closing degrees of each of the expansion valves 13 so that the total opening and closing degrees of the expansion valves 13 is constant.

[0032] The control unit 30 controls the frequency of the compressor 11 so that when the temperature of the air in the cooling area 110 is higher than the target value, the frequency of the compressor 11 is increased, and when the temperature of the air in the cooling area 110 is lower than the target value, the frequency of the compressor 11 is decreased.

[0033] (Compressor control flow) 2, in step S11, the control unit 30 starts the compressor 11. After that, the process proceeds to step S12.

[0034] In step S12, the control unit 30 determines whether the temperature in the cooling region 110 is lower than the final target value. If the control unit 30 determines that the temperature in the cooling region 110 is lower than the compressor stop temperature for stopping the compressor 11, the process proceeds to step S13. If the control unit 30 determines that the temperature in the cooling region 110 is equal to or higher than the compressor stop temperature, the process proceeds to step S14.

[0035] In step S13, the control unit 30 stops the compressor 11. Thereafter, the control unit 30 ends the control of the compressor 11.

[0036] In step S14, the control unit 30 determines whether the temperature in the cooling region 110 is greater than the target value. If the control unit 30 determines that the temperature in the cooling region 110 is greater than the target value, the process proceeds to step S15. If the control unit 30 determines that the temperature in the cooling region 110 is not greater than the target value, the process proceeds to step S16.

[0037] In step S15, the control unit 30 increases the frequency of the compressor 11. After that, the process returns to step S12.

[0038] In step S16, the control unit 30 determines whether the temperature in the cooling region 110 is lower than the target value. If the control unit 30 determines that the temperature in the cooling region 110 is lower than the target value, the control unit 30 proceeds to step S17. If the control unit 30 determines that the temperature in the cooling region 110 is not lower than the target value, the control unit 30 returns to step S12.

[0039] In step S17, the control unit 30 reduces the frequency of the compressor 11. After that, the process returns to step S12.

[0040] (Expansion valve control flow) 3, in step S21, the control unit 30 determines whether the temperature in the cooling region 110 is lower than the final target value. If the control unit 30 determines that the temperature in the cooling region 110 is lower than the compressor stop temperature for stopping the compressor 11, the control unit 30 ends the control of the expansion valve 13. If the control unit 30 determines that the temperature in the cooling region 110 is equal to or higher than the compressor stop temperature, the control unit 30 proceeds to step S22.

[0041] In step S22, the control unit 30 determines whether the degree of superheat is smaller than the target value. If the control unit 30 determines that the degree of superheat is smaller than the target value, the process proceeds to step S22. If the control unit 30 determines that the degree of superheat is not smaller than the target value, the process returns to step S24.

[0042] In step S23, the control unit 30 reduces the opening degree of the expansion valve 13. After that, the process returns to step S21.

[0043] In step S24, the control unit 30 determines whether the degree of superheat is greater than the target value. If the control unit 30 determines that the degree of superheat is greater than the target value, the process proceeds to step S25. If the control unit 30 determines that the degree of superheat is not greater than the target value, the process returns to step S21.

[0044] In step S25, the control unit 30 increases the opening degree of the expansion valve 13. After that, the process returns to step S21.

[0045] (Effects of the first embodiment) In the first embodiment, the following effects can be obtained.

[0046] In the first embodiment, as described above, one expansion valve 13 is provided for each of the plurality of branch refrigerant flow paths 16. Furthermore, one evaporator 14 is provided so that the plurality of branch refrigerant flow paths 16 pass through it to cool the same cooling region 110. This allows the expansion valves 13 provided for each of the plurality of branch refrigerant flow paths 16 to individually adjust the flow rate of the refrigerant for each of the plurality of branch refrigerant flow paths 16. As a result, the evaporation temperature of the refrigerant in the evaporator 14 can be controlled to an optimum value suited to the operating conditions of the cooling device 100. Furthermore, pressure loss when the refrigerant passes through the evaporator 14 can be suppressed.

[0047] Furthermore, in the first embodiment, as described above, the cooling device 100 includes the control unit 30 that individually controls the opening and closing of each of the plurality of expansion valves 13 based on the degree of superheat, which is the difference between the inlet temperature of the evaporator 14 and the outlet temperature of the evaporator 14, in each of the plurality of branch refrigerant flow paths 16 so as to cool the same cooling region 110. In this way, the control unit 30 controls the opening and closing of the expansion valve 13 provided one for each of the plurality of branch refrigerant flow paths 16, making it possible to easily adjust the flow rate of the refrigerant for each of the plurality of branch refrigerant flow paths 16 individually.

[0048] Furthermore, in the first embodiment, as described above, the cooling device 100 includes an inlet temperature sensor 21 provided in at least one of the plurality of branch refrigerant flow paths 16 to detect the inlet temperature of the evaporator 14, and a plurality of outlet temperature sensors 22 provided in each of the plurality of branch refrigerant flow paths 16 to detect the outlet temperature of the evaporator 14. Thus, the inlet temperature sensor 21 provided in at least one of the plurality of branch refrigerant flow paths 16 and the plurality of outlet temperature sensors 22 provided in each of the plurality of branch refrigerant flow paths 16 can easily and individually obtain the degree of superheat, which is the difference between the inlet temperature of the evaporator 14 and the outlet temperature of the evaporator 14, in each of the plurality of branch refrigerant flow paths 16. Note that the inlet temperature of the evaporator 14 is approximately the same for all of the plurality of branch refrigerant flow paths 16, so it is sufficient that the inlet temperature sensor 21 is provided in at least one of the plurality of branch refrigerant flow paths 16.

[0049] In the first embodiment, as described above, the cooling region 110 is a freezer compartment for freezing commodities therein. The refrigerant is R1234yf. In the Mollier diagram (pressure-specific entropy diagram) for R1234yf, the isotherm at a temperature near -30°C has a relatively dense pressure scale compared to other refrigerants used to cool the freezer compartment. In other words, when R1234yf is used to cool the freezer compartment, it is relatively difficult to control the evaporation temperature to a target value. Therefore, the evaporation temperature of the refrigerant in the evaporator 14 can be effectively controlled to an optimal value suited to the operating conditions of the cooling device 100. Furthermore, because R1234yf has a lower density than other refrigerants used to cool the freezer compartment, if the pressure loss when passing through the evaporator 14 is large, the refrigeration capacity of the cooling device 100 will be significantly reduced. Therefore, the pressure loss when the refrigerant passes through the evaporator 14 can be effectively suppressed.

[0050] Furthermore, in the first embodiment, as described above, the cooling device 100 includes a plurality of capillary tubes 17 arranged between the condenser 12 and the evaporator 14 in each of the plurality of branch refrigerant flow paths 16. This allows the refrigerant to expand (depressurize) in each of the plurality of branch refrigerant flow paths 16 due to the flow path resistance of the capillary tubes 17. This reduces the amount of expansion of the refrigerant by the expansion valve 13 in each of the plurality of branch refrigerant flow paths 16, thereby reducing the load acting on the expansion valve 13.

[0051] Furthermore, in the first embodiment, as described above, the cooling device 100 is used in a vending machine or a showcase. This makes it possible to control the evaporation temperature of the refrigerant in the evaporator 14 in the vending machine or showcase to an optimum value that matches the operating conditions of the cooling device 100. Furthermore, in the vending machine or showcase, it is possible to suppress pressure loss when the refrigerant passes through the evaporator 14.

[0052] [Second embodiment] The configuration of a cooling device 200 according to a second embodiment of the present invention will be described with reference to Figures 4 and 5. In the figures, the same components as those in the cooling device 100 according to the first embodiment are denoted by the same reference numerals.

[0053] (Overall configuration of the cooling device) As shown in FIG. 4, the cooling device 200 includes a compressor 11, a condenser 12, an expansion valve 13, an evaporator 14, and a refrigerant flow path 15.

[0054] (Multiple branched refrigerant flow paths) The refrigerant flow path 15 is branched into a plurality (two) of branched refrigerant flow paths 16 (first branch refrigerant flow path 16a and second branch refrigerant flow path 16b) downstream of the condenser 12 and upstream of the expansion valve 13, and includes a plurality (two) of branch refrigerant flow paths 16 that merge downstream of the evaporator 14 and upstream of the compressor 11. One expansion valve 13 is provided for each of the plurality (two) of branch refrigerant flow paths 16. The first branch refrigerant flow path 16a and the second branch refrigerant flow path 16b are provided with a first expansion valve 13a and a second expansion valve 13b, respectively. One evaporator 14 is provided so that the plurality (two) of branch refrigerant flow paths 16 (first branch refrigerant flow path 16a and second branch refrigerant flow path 16b) pass through it to cool the same cooling region 110.

[0055] (Compressor and expansion valve control) The cooling device 200 includes an evaporation temperature sensor (not shown), an air inlet sensor 224, an air outlet temperature sensor 225, and a control unit 230.

[0056] The evaporation temperature sensor detects the evaporation temperature of the refrigerant in the evaporator 14. The evaporation temperature of the refrigerant in the evaporator 14 detected by the evaporation temperature sensor is output to the control unit 230.

[0057] The air inlet sensor 224 detects the temperature of the air inlet of the evaporator 14 in the cooling region 110. The temperature of the air inlet of the evaporator 14 in the cooling region 110 detected by the air inlet sensor 224 is output to the control unit 230.

[0058] The outlet temperature sensor 225 detects the temperature of the outlet of the evaporator 14 in the cooling region 110. The temperature of the outlet of the evaporator 14 in the cooling region 110 detected by the outlet temperature sensor 225 is output to the control unit 230.

[0059] 5, the control unit 230 controls (PID control) the frequency of the compressor 11 based on the evaporation temperature of the refrigerant in the evaporator 14. The control unit 230 controls (PID control) the opening / closing degree of the expansion valve 13 based on the degree of superheat. Specifically, the control unit 230 controls (PID control) the opening / closing degree of the first expansion valve 13a based on the degree of superheat in the first branch refrigerant flow path 16a, and controls (PID control) the opening / closing degree of the second expansion valve 13b based on the degree of superheat in the second branch refrigerant flow path 16b.

[0060] (Change in target evaporation temperature) As shown in FIG. 5, the control unit 230 is configured to control the frequency of the compressor 11 while gradually lowering the target value of the evaporation temperature as the inlet / outlet temperature difference between the suction port of the evaporator 14 and the outlet port of the evaporator in the cooling region 110 decreases.

[0061] Specifically, when the inlet / outlet temperature difference falls to a first threshold value TV1, the control unit 230 lowers the target value of the evaporation temperature from a zeroth target value DV0 to a first target value DV1 and controls the frequency of the compressor 11 so that the evaporation temperature reaches the first target value DV1. Furthermore, when the inlet / outlet temperature difference falls to a second threshold value TV2 that is smaller than the first threshold value TV1, the control unit 230 lowers the target value of the evaporation temperature to a second target value DV2 that is smaller than the first target value DV1 and controls the frequency of the compressor 11 so that the evaporation temperature reaches the second target value DV2. The second target value DV2 is the final target value. In other words, the target value of the evaporation temperature changes in three stages. This control is performed when recovering the temperature in the cooling region 110 to a temperature that allows normal operation after a defrosting operation or product loading.

[0062] The other configurations of the cooling device 200 of the second embodiment are similar to those of the cooling device 100 of the first embodiment.

[0063] (Effects of the second embodiment) In the second embodiment, the following effects can be obtained.

[0064] In the second embodiment, as described above, one expansion valve 13 is provided for each of the plurality of branch refrigerant flow paths 16. Furthermore, one evaporator 14 is provided so that the plurality of branch refrigerant flow paths 16 pass through it and cool the same cooling region 110. As a result, similar to the first embodiment, the expansion valves 13 provided for each of the plurality of branch refrigerant flow paths 16 can individually adjust the refrigerant flow rate for each of the plurality of branch refrigerant flow paths 16. As a result, similar to the first embodiment, the evaporation temperature of the refrigerant in the evaporator 14 can be controlled to an optimal value that matches the operating status of the cooling device 100. Furthermore, similar to the first embodiment, pressure loss when the refrigerant passes through the evaporator 14 can be suppressed.

[0065] Furthermore, in the second embodiment, as described above, the cooling device 200 includes a control unit 230 that controls the frequency of the compressor 11 based on the evaporation temperature of the refrigerant in the evaporator 14. The control unit 230 is configured to control the frequency of the compressor 11 while gradually lowering the target value of the evaporation temperature as the inlet / outlet temperature difference between the suction port of the evaporator 14 and the outlet port of the evaporator 14 in the cooling region 110 decreases. As a result, when the evaporation temperature of the refrigerant in the evaporator 14 is relatively high, the amount of heat removed from the fluid to be cooled in the evaporator 14 becomes relatively large. Therefore, the time required to cool the cooling region 110 can be shortened compared to when the target value of the evaporation temperature of the refrigerant in the evaporator 14 is not changed (it is always the final target value). Furthermore, because the target value of the evaporation temperature is gradually lowered, the control by the control unit 230 is simplified, unlike when the target value of the evaporation temperature is continuously lowered, and the control burden on the control unit 230 can be reduced.

[0066] Furthermore, in the second embodiment, as described above, the control unit 230 is configured to: when the inlet / outlet temperature difference falls to a first threshold TV1, reduce the target value of the evaporation temperature to a first target value DV1 and control the frequency of the compressor 11 so that the evaporation temperature becomes the first target value DV1; and when the inlet / outlet temperature difference falls to a second threshold TV2 that is smaller than the first threshold TV1, reduce the target value of the evaporation temperature to a second target value DV2 that is smaller than the first target value DV1 and control the frequency of the compressor 11 so that the evaporation temperature becomes the second target value DV2. This makes it easy to control the frequency of the compressor 11 while gradually reducing the target value of the evaporation temperature as the inlet / outlet temperature difference between the suction port of the evaporator 14 and the outlet of the evaporator 14 in the cooling region 110 decreases.

[0067] The other effects of the second embodiment are the same as those of the first embodiment.

[0068] [Variations] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims rather than the description of the above embodiments, and further includes all modifications (variations) within the meaning and scope of the claims.

[0069] For example, in the first and second embodiments described above, an example was shown in which one evaporator 14 is provided so that multiple branch refrigerant flow paths 16 pass through it to cool the same cooling region 110, but the present invention is not limited to this. In the present invention, as in a cooling device 300 according to a first modified example shown in Fig. 6, one evaporator 314 may be provided for each of the multiple branch refrigerant flow paths 16 to cool the same cooling region 110.

[0070] Furthermore, in the above first and second embodiments, an example has been shown in which refrigerant flow path 15 is branched into two downstream of condenser 12 and upstream of expansion valve 13 and includes two branch refrigerant flow paths 16 that merge downstream of evaporator 14 and upstream of compressor 11, but the present invention is not limited to this. In the present invention, the refrigerant flow path may be branched into N or more (N≧3) paths downstream of the condenser and upstream of the expansion valve, and may include N (N≧3) branch refrigerant flow paths that merge downstream of the evaporator and upstream of the compressor.

[0071] Furthermore, in the first embodiment, the cooling device 100 includes an inlet temperature sensor 21 provided in at least one of the branch refrigerant flow paths 16 to detect the inlet temperature of the evaporator 14, and a plurality of outlet temperature sensors 22 provided in each of the branch refrigerant flow paths 16 to detect the outlet temperature of the evaporator 14. However, the present invention is not limited to this. The present invention does not necessarily include the inlet temperature sensor 21 provided in at least one of the branch refrigerant flow paths 16 to detect the inlet temperature of the evaporator 14, and the plurality of outlet temperature sensors 22 provided in each of the branch refrigerant flow paths 16 to detect the outlet temperature of the evaporator 14, as in a cooling device 400 according to a second modification shown in FIG. 7 . The cooling device 400 also includes a plurality of temperature-type expansion valves 413 provided in each of the branch refrigerant flow paths 16, each capable of indirectly obtaining the degree of superheat, which is the difference between the inlet temperature of the evaporator 14 and the outlet temperature of the evaporator 14, in each of the branch refrigerant flow paths 16.

[0072] In the first and second embodiments, the cooling area 110 is a freezer compartment for freezing the products therein, but the present invention is not limited to this. In the present invention, the cooling area may be a refrigerator compartment for refrigerating the products therein.

[0073] Furthermore, in the first and second embodiments, an example was shown in which the refrigerant was R1234yf, but the present invention is not limited to this. In the present invention, the refrigerant may be a refrigerant other than R1234yf.

[0074] In the above first and second embodiments, the cooling device 100 (200) includes a plurality of capillary tubes 17 arranged between the condenser 12 and the evaporator 14 in each of the plurality of branched refrigerant flow paths 16, but the present invention is not limited to this. In the present invention, the cooling device does not necessarily have to include a plurality of capillary tubes arranged between the condenser and the evaporator in each of the plurality of branched refrigerant flow paths.

[0075] In the first and second embodiments, the cooling device 100 (200) is used in a vending machine or a showcase, but the present invention is not limited to this. In the present invention, the cooling device may be used in devices other than a vending machine or a showcase.

[0076] In the second embodiment, the target value of the evaporation temperature is changed in three stages, but the present invention is not limited to this. In the present invention, the target value of the evaporation temperature may be changed in two stages, or may be changed in four or more stages.

[0077] In the first and second embodiments, the cooling device 100 (200) includes the compressor 11, the condenser 12, the expansion valve 13, the evaporator 14, the refrigerant flow path 15, and the capillary tube 17. However, the present invention is not limited to this. As in a cooling device 500 according to a third modification shown in Fig. 8, the present invention may include, in addition to the compressor 11, the condenser 12, the expansion valve 13, the evaporator 14, the refrigerant flow path 15, and the capillary tube 17, an internal heat exchanger 541 that exchanges heat between a portion of the refrigerant flow path 15 that is upstream of the compressor 11 and downstream of the evaporator 14 and a portion of the refrigerant flow path 15 that is downstream of the condenser 12 and upstream of the expansion valve 13, an accumulator 542 that is arranged upstream of the compressor 11 and that stores high-pressure gas, and a defrosting heater 543 that is provided in the evaporator 14. [Explanation of symbols]

[0078] 11 Compressor 12 Condenser 13, 413 Expansion valve 14, 314 Evaporator 15 refrigerant flow path 16 Branched refrigerant flow path 17 Capillary tube 21 Inlet temperature sensor 22 Outlet temperature sensor 30, 230 Control section 100, 200, 300, 400, 500 chillers 110 Cooling area DV1 First target value DV2 Second target value TV1 First Threshold TV2 Second Threshold

Claims

1. a compressor that compresses a refrigerant; a condenser that condenses the refrigerant compressed by the compressor; an expansion valve that expands the refrigerant condensed by the condenser and adjusts the flow rate of the refrigerant; an evaporator that evaporates the refrigerant expanded by the expansion valve; a refrigerant flow path through which the refrigerant flows, the refrigerant flow path includes a plurality of branched refrigerant flow paths that are branched into a plurality of paths downstream of the condenser and upstream of the expansion valve and that join together downstream of the evaporator and upstream of the compressor, the expansion valve is provided in each of the plurality of branched refrigerant flow paths, The cooling device, wherein the evaporator is provided so that the plurality of branched refrigerant flow paths pass through the evaporator to cool the same cooling region, or the evaporator is provided so that one evaporator is provided for each of the plurality of branched refrigerant flow paths to cool the same cooling region.

2. 2. The cooling device according to claim 1, further comprising a control unit that individually controls the opening and closing degrees of each of the plurality of expansion valves based on each degree of superheat, which is the difference between the inlet temperature of the evaporator and the outlet temperature of the evaporator, in each of the plurality of branch refrigerant flow paths so as to cool the same cooling region.

3. an inlet temperature sensor provided in at least one of the plurality of branched refrigerant flow paths, the inlet temperature sensor detecting an inlet temperature of the evaporator; The cooling device according to claim 2 , further comprising a plurality of outlet temperature sensors, one for each of the plurality of branched refrigerant flow paths, for detecting an outlet temperature of the evaporator.

4. the cooling area is a freezer compartment for freezing the goods therein; 2. The cooling device of claim 1, wherein the refrigerant is R1234yf.

5. The cooling device according to claim 1 , further comprising a plurality of capillary tubes disposed between the condenser and the evaporator in each of the plurality of branched refrigerant flow paths.

6. The cooling device according to claim 1, which is used in a vending machine or a showcase.

7. a control unit that controls a frequency of the compressor based on an evaporation temperature of the refrigerant in the evaporator, 2. The cooling device according to claim 1, wherein the control unit is configured to control the frequency of the compressor while gradually lowering the target value of the evaporation temperature as the inlet / outlet temperature difference between the evaporator inlet and the evaporator outlet in the cooling region decreases.

8. The control unit When the inlet / outlet temperature difference decreases to a first threshold value, the target value of the evaporation temperature is decreased to a first target value, and the frequency of the compressor is controlled so that the evaporation temperature becomes the first target value; 8. The cooling device according to claim 7, wherein when the inlet / outlet temperature difference decreases to a second threshold value that is smaller than the first threshold value, the target value of the evaporation temperature is decreased to a second target value that is smaller than the first target value, and the frequency of the compressor is controlled so that the evaporation temperature becomes the second target value.

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