Cooling room

Abstract

To make a period of heater defrosting longer by improving a defrosting capacity in off-cycle defrosting.SOLUTION: A control portion 22 can execute heater defrosting for heating an evaporator 6 by energizing a defrost heater 23 and off-cycle defrosting for keeping a compressor 14 in a stop state over a prescribed defrosting time T1. When a standby time T2 shorter than the defrosting time T1 has passed from the start of off-cycle defrosting, the control portion 22 fully opens an expansion valve 17 and guides a refrigerant from a condenser 15 to the evaporator 6 through the expansion valve 17.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to defrosting control of an evaporator for cooling the interior of a refrigerator such as a refrigerated showcase or a commercial refrigerator. [Background technology]

[0002] Moisture contained in the air inside the refrigerator may cool and solidify on the evaporator that cools the interior of the refrigerator, forming frost. Known defrosting methods for melting and removing this frost include the heater defrosting method, which uses a heater to heat the evaporator, and the off-cycle defrosting method, which stops the refrigerator operation and melts the frost naturally. The former method has a higher defrosting capacity than the latter method, and the latter method consumes less power than the former method, so there are many attempts to use both methods depending on the situation.

[0003] Stores such as supermarkets that use refrigerated showcases with openings on the front or top, so-called refrigerated open showcases, do not want to perform heater defrosting when the store is open. This is because, compared to when the store is closed and the openings are covered with night covers, outside air is more likely to enter the store when the store is open, and the temperature inside the store is more likely to become relatively high due to customers entering and leaving the store. If heater defrosting is performed under such circumstances, the air warmed by the heater will circulate inside the store, causing the temperature inside the store to rise significantly, making fresh foods inside the store more likely to spoil. From the viewpoint of maintaining the freshness of the products inside the store, it is desirable to perform only off-cycle defrosting and not heater defrosting when the store is open. A refrigerated open showcase that performs off-cycle defrosting when the store is open and heater defrosting when the store is closed is disclosed in, for example, Patent Document 1 and is publicly known. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 63-263377 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, the disadvantage of the off-cycle defrost system is that it has a lower defrosting capacity than the heater defrost system. In particular, if the store has long business hours, even if the heater defrost is performed just before opening to completely remove the frost, the off-cycle defrost system may not be able to keep up with removing the frost that increases during the store's opening hours, resulting in clogging of the evaporator and a decrease in its cooling capacity. In such cases, the heater defrost must be performed even when the store is open, which may cause damage to fresh food stored in the store.

[0006] An object of the present invention is to increase the defrosting capacity of the off-cycle defrost in a refrigerator capable of carrying out heater defrost and off-cycle defrost, thereby lengthening the heater defrost cycle. [Means for solving the problem]

[0007] The refrigerator according to the present invention is a refrigerator that cools the air in the interior 5 with a refrigeration cycle 13 including a compressor 14, a condenser 15, an expansion valve 17, and an evaporator 6, and is equipped with a defrost heater 23 for defrosting the evaporator 6, and a control unit 22 that is responsible for controlling the defrosting of the evaporator 6. The control unit 22 controls a heater defrost that energizes the defrost heater 23 to heat the evaporator 6, and Set between 10 and 15 minutes and off-cycle defrosting in which the compressor 14 is kept stopped for a predetermined defrosting time T1. At the same time as stopping the compressor 14 and starting the off-cycle defrosting, the control unit 22 fully closes the expansion valve 17, and when a standby time T2 shorter than the defrosting time T1 has elapsed, the control unit 22 fully opens the expansion valve 17 to guide the refrigerant from the condenser 15 to the evaporator 6 through the expansion valve 17.

[0009] The standby time T2 is set to be equal to or greater than half the defrosting time T1.

[0010] During off-cycle defrost, the cooling fan 16 that cools the condenser 15 is driven. Effect of the Invention

[0011] In the refrigerator according to the present invention, when a predetermined waiting time T2 has elapsed since the start of off-cycle defrosting, the refrigerant is guided from the condenser 15 to the evaporator 6 through the expansion valve 17 which is fully opened. This allows the evaporator 6 to be heated from the inside by the refrigerant, and the frost on the evaporator 6 to be melted faster. By fully opening the expansion valve 17, a drop in the temperature of the refrigerant at the expansion valve 17 is avoided, and the refrigerant coming out of the condenser 15 can be guided to the evaporator 6 at almost the same temperature, and can be sufficiently heated. In other words, according to the present invention, the defrosting capacity of the off-cycle defrosting can be increased, and the heater defrosting period can be lengthened.

[0012] Incidentally, the refrigerant that has passed through the condenser 15 is not as hot as the so-called hot gas discharged from the compressor 14, so even if this refrigerant is introduced to the evaporator 6, the temperature inside the container 5 does not rise significantly. Furthermore, in the present invention, the refrigerant is introduced to the evaporator 6 after a predetermined waiting time T2 has elapsed, rather than immediately after the start of off-cycle defrost. In other words, the time during which the refrigerant flows through the evaporator 6 (heating time T3) is limited to a short time from the time the waiting time T2 has elapsed until the end of off-cycle defrost, so that the rise in temperature inside the container 5 due to the refrigerant can be suppressed.

[0014] The time obtained by subtracting the standby time T2 from the defrost time T1 is the time during which the refrigerant flows through the evaporator 6, that is, the heating time T3. By setting the standby time T2 to half or more of the defrost time T1, the heating time T3 is limited to half or less of the defrost time T1, and the temperature rise in the interior 5 caused by the refrigerant can be more reliably suppressed.

[0015] If the cooling fan 16 that cools the condenser 15 is driven while the off-cycle defrost is being performed, the refrigerant remaining in the condenser 15 is forcibly air-cooled during the period from the start of the off-cycle defrost until the waiting time T2 has elapsed, and the refrigerant cooled to near the outside air temperature can be guided to the evaporator 6, thereby further suppressing the temperature rise inside the cabinet 5 due to the refrigerant. [Brief description of the drawings]

[0016] [Figure 1] 4 is a timing chart showing the driving states of each device constituting the refrigerated showcase according to the first embodiment of the present invention. [Diagram 2] FIG. 2 is a vertical cross-sectional view showing a schematic configuration of the refrigerated showcase. [Diagram 3] FIG. 2 is a diagram showing the configuration of a refrigeration cycle installed in the refrigerated showcase. [Figure 4] FIG. 2 is a configuration diagram of a refrigeration cycle mounted in a refrigerated showcase according to a reference example. [Diagram 5] 4 is a timing chart showing the driving states of each device constituting the refrigerated showcase. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] (First embodiment) A first embodiment of a refrigeration cabinet according to the present invention is shown in Fig. 1 to Fig. 3. As shown in Fig. 2, the refrigeration cabinet according to this embodiment is a flat open showcase (hereinafter simply referred to as a refrigerated showcase) for displaying fresh foods such as meat and fish in a refrigerated state in a store such as a supermarket, and comprises a heat-insulating outer box 1 with an open top and an inner box 2 placed inside it. The space surrounded by the inner box 2 forms a display room 3 for fresh foods, and a cold air duct 4 is formed between the outer box 1 and the inner box 2. The display room 3 and the cold air duct 4 form the interior 5 of the refrigerated showcase according to this embodiment.

[0018] The cold air duct 4 is provided with an evaporator 6 for cooling the air in the interior 5, and an interior fan 7 for circulating the air in the interior 5. An intake port 8 and an exhaust port 9 are formed at both ends of the cold air duct 4, facing each other above the display room 3. When the interior fan 7 is driven, the cold air cooled by the evaporator 6 is blown out from the exhaust port 9, forming an air curtain of cold air flowing toward the intake port 8, thereby cooling the display room 3 and blocking the intrusion of outside air into the display room 3.

[0019] Outside the refrigerated showcase, in the machine room 12 below the outer box 1, there are installed a compressor 14 and a condenser 15 which constitute a refrigeration cycle 13 together with an evaporator 6, and a cooling fan 16 for cooling these devices 14 and 15. As shown in FIG. 3, the refrigeration cycle 13 is configured by connecting the compressor 14, the condenser 15, the expansion valve 17, the evaporator 6, and an accumulator 18 with a refrigerant pipe 19. When the compressor 14 is driven, a low-temperature, low-pressure liquid refrigerant cooled through the condenser 15 and the expansion valve 17 is supplied to the evaporator 6, and the air passing through the evaporator 6 is heat exchanged (cooled). The expansion valve 17 is an electronic expansion valve which adjusts the refrigerant flow rate by controlling the valve opening time per unit time, and the opening degree (proportion of the valve opening time) of the expansion valve 17 during the cooling operation is set to about 30 to 40%. The expansion valve 17 may be one which can change the cross-sectional area of ​​the flow passage.

[0020] Moisture contained in the air inside the refrigerator may cool and solidify on the evaporator 6, forming frost. The defrost control for melting and removing the frost will be described below. The control unit 22 of the refrigerated showcase can execute heater defrosting, which energizes the defrost heater 23 attached to the evaporator 6 to heat the evaporator 6, and off-cycle defrosting, which stops the compressor 14 and melts the frost naturally by ventilation using the inside fan 7. While the heater defrosting is intended to completely remove the frost, the off-cycle defrosting is mainly performed to reduce the volume of the frost. It is not essential to drive the inside fan 7 in the off-cycle defrosting, but it is desirable to drive the inside fan 7 from the viewpoint of promoting defrosting and maintaining the air curtain.

[0021] Heater defrost is performed twice a day, approximately every 12 hours, before the store opens and after the store closes. Off-cycle defrost is performed about 1 to 3 times between heater defrosts. In this embodiment, the start condition of off-cycle defrost is set to 3 hours after the start of the previous defrosting operation (heater defrost or off-cycle defrost). The end condition is set to a predetermined defrosting time T1 after the start of off-cycle defrost. The defrosting time T1 can be set between 10 and 15 minutes, for example, and is set to 10 minutes in this embodiment. Note that the defrosting time T1 does not need to be a constant value at all times, and may be a variable that varies depending on the amount of frost on the evaporator 6, the outside air temperature, and the like.

[0022] At a preset time before opening time or after closing time, the control unit 22 stops the cooling operation of the interior 5 and starts the heater defrost. More specifically, as shown in the timing chart of FIG. 1, at time p1 when the heater defrost start time is reached, the control unit 22 stops the compressor 14 and the cooling fan 16, closes the expansion valve 17, and starts the power supply to the defrost heater 23. The progress of the heater defrost can be determined by the temperature of the evaporator 6, and when the temperature rises to a predetermined defrost end temperature (for example, 10°C), the control unit 22 considers that the frost on the evaporator 6 has sufficiently melted and resumes the cooling operation (time p2). More specifically, the power supply to the defrost heater 23 is stopped, and after a draining time of several minutes has elapsed, the expansion valve 17 is opened to start the compressor 14 and the cooling fan 16. Although not shown in this chart, the expansion valve 17 is temporarily opened just before time p2 when the cooling operation is resumed. This is for equalizing the pressure on the high pressure side and the low pressure side of the refrigeration cycle 13.

[0023] At the next point p3, the above-mentioned off-cycle defrost start condition is satisfied, and the control unit 22 closes the expansion valve 17 to stop the compressor 14. At this time, the cooling fan 16 and the internal fan 7 continue to be driven, and are maintained in the driven state until the end of the off-cycle defrost. Between point p3 and point p4, the frost on the evaporator 6 melts relatively slowly due to the ventilation from the internal fan 7. During this time, the refrigerant remaining in the condenser 15 is forcibly air-cooled by the cooling fan 16, and the condensation of the refrigerant progresses.

[0024] The next time point p4 is a time point when a predetermined waiting time T2 has elapsed from time point p3, and the opening degree of the expansion valve 17 is switched from fully closed to fully open. As a result, the refrigerant that has been air-cooled to near the outside air temperature in the condenser 15 flows into the evaporator 6 via the expansion valve 17. Since the expansion valve 17 is fully open, the temperature of the refrigerant hardly drops in the expansion valve 17. The refrigerant that flows into the evaporator 6 is in a liquid state, and its temperature is about 25 to 30°C. After time point p4, in addition to the ventilation from the interior fan 7 to the evaporator 6, the evaporator 6 is heated from the inside by the refrigerant, so that the frost on the evaporator 6 melts faster than before time point p4. It is desirable to set the waiting time T2 to at least half of the defrosting time T1 (10 minutes), and in this embodiment, it is set to 7 minutes. In other words, the heating time T3 during which the evaporator 6 is heated by the refrigerant is set to 3 minutes (T3 = T1 - T2).

[0025] At the next time point p5, the end condition for the off-cycle defrost is satisfied, that is, the defrosting time T1 has elapsed since time point p3, and the control unit 22 resumes the cooling operation. In detail, the compressor 14 is started and the expansion valve 17 is switched from full open to the opening during the cooling operation (approximately 30 to 40%) so that the low-temperature, low-pressure liquid refrigerant decompressed by the expansion valve 17 is supplied to the evaporator 6.

[0026] As described above, in the refrigerated showcase according to this embodiment, when the standby time T2 has elapsed since the start of the off-cycle defrost, the refrigerant is guided from the condenser 15 to the evaporator 6 through the expansion valve 17 that is fully opened. This allows the evaporator 6 to be heated from the inside by the refrigerant, and the frost on the evaporator 6 to be melted quickly. By fully opening the expansion valve 17, the temperature drop of the refrigerant in the expansion valve 17 can be avoided, and the refrigerant coming out of the condenser 15 can be guided to the evaporator 6 at almost the same temperature, and can be heated sufficiently. In other words, according to this embodiment, the defrosting capacity of the off-cycle defrost can be increased, and the heater defrost cycle can be lengthened. In other words, the heater defrost during opening, which was difficult to avoid when the store's business hours are long, is no longer necessary, and the freshness of the fresh food in the storage 5 can be maintained at a high level.

[0027] In the present invention, it is not essential to cool the condenser 15 with the cooling fan 16 during off-cycle defrosting. However, by driving the cooling fan 16 as in this embodiment, the refrigerant remaining in the condenser 15 can be forcibly air-cooled and its temperature can be lowered to near the outside air temperature during the period from the start of off-cycle defrosting to the lapse of the standby time T2. Even if this refrigerant is guided to the evaporator 6, the temperature inside the container 5 does not rise significantly. Furthermore, in this embodiment, the standby time T2 is set to half or more of the defrosting time T1, and the heating time T3 during which the refrigerant flows through the evaporator 6 is limited to half or less of the defrosting time T1, so that the temperature rise inside the container 5 due to the refrigerant can be more reliably suppressed.

[0028] ( Reference example ) Reference example Cooling Warehouse This is shown in Figures 4 and 5. Reference example The refrigeration cycle 13 according to the present invention includes an expander 27 made of a capillary tube instead of the expansion valve 17 whose opening degree is adjustable. The refrigeration cycle 13 also includes a bypass passage 28 that bypasses the expander 27, and an opening / closing means 29 made of a solenoid valve that opens and closes the bypass passage 28.

[0029] As shown in the timing chart of FIG. 5, the bypass passage 28 during the cooling operation is closed by the opening and closing means 29. Therefore, the refrigerant coming out of the condenser 15 is decompressed by passing through the expansion device 27, and flows into the evaporator 6 in a low-temperature, low-pressure state. The bypass passage 28 continues to be closed during the execution of the heater defrost (times p1 to p2) from the cooling operation. The bypass passage 28 is also closed at time p3 when the off-cycle defrost starts, but at time p4 when the standby time T2 has elapsed from that time, the control unit 22 opens the opening and closing means 29 and guides the refrigerant from the condenser 15 to the evaporator 6 through the bypass passage 28. Since no expansion means is provided in the bypass passage 28, the refrigerant coming out of the condenser 15 flows into the evaporator 6 almost without being cooled, and heats it from the inside. The refrigerant flowing into the evaporator 6 is in a liquid state, and its temperature is about 25 to 30° C. The supply of the refrigerant through the bypass passage 28 continues until time p5 when the off-cycle defrost ends.

[0030] As mentioned above, Reference example In the refrigerated showcase according to the present invention, when the standby time T2 has elapsed since the start of off-cycle defrosting, the refrigerant is guided from the condenser 15 to the evaporator 6 through the bypass passage 28 that bypasses the expander 27. This allows the evaporator 6 to be heated from the inside with the refrigerant, and the melting of frost on the evaporator 6 can be accelerated. By passing the refrigerant through the bypass passage 28 that does not have an expansion means, the refrigerant coming out of the condenser 15 can be guided to the evaporator 6 at almost the same temperature, and can be heated sufficiently. In other words, Reference example This also increases the defrosting capacity of the off-cycle defrost, thereby lengthening the heater defrost cycle. Since the other configurations and effects are the same as those of the first embodiment, the same members are given the same reference numerals and their description will be omitted. [Explanation of symbols]

[0031] 5 Inside the warehouse 6. Evaporator 13 Refrigeration cycle 14 Compressor 15 Condenser 16 Cooling fan 17 Expansion valve 22 Control section 23 Defrost heater 27 Expander 28 Bypass Road 29 Opening and closing means T1 Defrost time T2 Waiting Time T3 Heating time

Claims

1. A refrigerator that cools air inside the refrigerator (5) using a refrigeration cycle (13) including a compressor (14), a condenser (15), an expansion valve (17), and an evaporator (6), The cooling system includes a defrosting heater (23) for defrosting the evaporator (6) and a control unit (22) for controlling the defrosting of the evaporator (6), the control unit (22) is capable of executing a heater defrost mode in which a defrost heater (23) is energized to heat the evaporator (6), and an off-cycle defrost mode in which the compressor (14) is maintained in a stopped state for a predetermined defrost time (T1) set between 10 and 15 minutes; The cooling cabinet is characterized in that, at the same time as stopping a compressor (14) and starting off-cycle defrosting, a control unit (22) fully closes an expansion valve (17), and when a standby time (T2) shorter than the defrosting time (T1) has elapsed, the control unit (22) fully opens the expansion valve (17) to guide a refrigerant from a condenser (15) to an evaporator (6) through the expansion valve (17).

2. 2. The refrigerator according to claim 1, wherein the waiting time (T2) is set to at least half the defrosting time (T1).

3. 3. The refrigerator according to claim 1, wherein a cooling fan (16) for cooling the condenser (15) is driven during off-cycle defrosting.

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