JPS6224711B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the operation of a refrigerated or refrigerated show case that keeps displayed products cool by circulating and ventilating cold air inside the store using a refrigerator.

First, the general structure of an open case will be described with reference to FIG. In Figure 1, 1 is the outer box of the case body of the open show case, 2 is the inner box, 3,
Reference numeral 4 denotes an evaporator and a blower fan of a refrigerator placed in a cold air circulation duct 5 partitioned between the outer box 1 and the inner box 2; 6 a product display shelf installed inside the inner box 2;
Reference numeral 7 indicates the products displayed inside the warehouse, 8 indicates a canopy-shaped lighting fixture installed protruding from the top of the front of the cabinet toward the outside of the cabinet, and 9 indicates the above-mentioned lighting fixture 8, the cabinet installed on the ceiling of the interior of the cabinet, and the bottom surface of each shelf 6. This is an internal lighting light. The evaporator 3 is connected to a separate refrigerator condensing unit (not shown). In this configuration, during storage operation, the cold air that has passed through the evaporator 3 flows into the duct 5 as shown by arrow A, reaches the open front area of the cabinet, and flows from the cold air outlet 10 in the upper part to the suction inlet 11 in the lower part. A cold air curtain A' is blown out to prevent outside air from entering and to keep the products 7 displayed in the warehouse cold. Note 12
is a defrosting heater placed close to the evaporator 3.

Such open show cases are installed in stores such as supermarkets, and are operated refrigerated with all the lights turned on during store operations.
When the store is closed, such as at night or on holidays, the store operates refrigerated with the lights turned off. By the way, as an example, in an open case for meat and fresh fish, the standard ambient conditions are a temperature of 25°C, a humidity of 60% (summer), and all lights of the open case are turned on. Storage operation is performed to maintain the average temperature of displayed products at a predetermined temperature of about 0°C. In addition, in order to maintain this rated performance, in a general open-air case, in order to maintain the temperature of the air that circulates inside the refrigerator and blows out from the cold air outlet 10 in Figure 1 at approximately a predetermined temperature, a The refrigerator is equipped with a temperature controller 13 that is activated by sensing the air temperature of the refrigerator and provides an operation control signal to the refrigerator. This temperature controller 13 is equipped with an electronic or mechanical thermostat that uses bimetal, and its operation signal is used to connect, for example, an electromagnetic contactor inserted in the power supply circuit of a refrigerator compressor, or a refrigerant circuit of a refrigerator. The inserted liquid solenoid valve is opened and closed to operate and stop the refrigerator. The operation control circuit of such a refrigerator is shown in FIG. In the diagram
CM is the compressor motor of the refrigerator, 52C is the electromagnetic contactor, FM is the fan motor of the blower fan 4 in Figure 1, TM is the defrost timer that sets the defrost cycle, and H is the defrost heater 12 in Figure 1. , 23I indicates the temperature regulator 13. The contact of the temperature controller 23I switches to the high temperature contact when the cold air temperature is higher than the set temperature, and to the low temperature contact when the cold air temperature is lower than the set temperature, and this contact switching operation causes the temperature of the air exiting the evaporator to drop below the set temperature. If this occurs, the refrigerator will be stopped, and if the temperature rises above the set temperature again, the refrigerator will be operated to maintain the temperature of the product at an appropriate temperature during cold storage operation.

On the other hand, the operating conditions for open show cases that are installed and operated in stores are summer and winter, whether or not there is an air conditioner in the store, lighting in the store during business hours and closing time, and whether the lights inside the show case are turned on or off. ,
Additionally, the surrounding environment may vary from the standard ambient conditions mentioned above depending on the presence or absence of a night cover used when the store is closed at night. For this reason, if the operating temperature setting of the temperature controller is set at a constant value to maintain the temperature of the cold air blown into the refrigerator at a constant level based on the ambient conditions mentioned above, it is possible to For example, in the case of an open meat case, the temperature of the products displayed in the warehouse changes as shown in characteristic lines A and B in Figure 3 depending on the on/off conditions, etc., making it impossible to maintain the specified product temperature. . In the figure, the horizontal axis represents the case surrounding conditions in terms of the enthalpy of the surrounding air; for example, the enthalpy of air under standard ambient conditions indicated by point X; temperature 25° C. and humidity 60% is 13.5 Kcal/Kg. Note that the line (b) is the operating setting value of the temperature controller, and the line (c) is the characteristic line of the average product temperature when the illumination light is turned off. As is clear from Figure 3, when the ambient temperature drops or the lights are turned off, such as when the store is closed at night, the amount of heat entering the open store case decreases, causing the temperature of displayed products to drop below 0°C. There is a risk that the meat will become supercooled and begin to freeze, resulting in quality deterioration.Furthermore, continuing to operate the freezer until the meat temperature drops below 0℃ will consume more electricity than necessary. It is also unfavorable in terms of energy saving. In this way, by simply using a temperature controller and setting its operating set value in accordance with standard ambient conditions, it is difficult to maintain the product temperature stably against changes in ambient conditions.

In addition to the above-mentioned problems, show cases have the problem of a decrease in cold storage performance and an increase in product temperature due to frost formation. That is, as the storage operation progresses, frost forms and adheres to the evaporator due to outside air entering through the opening of the case body. This amount of frost is determined by the refrigerant in the evaporator,
Assuming that the evaporation temperature is constant, the evaporation temperature increases as the cold storage operation time of the refrigerator increases and as the humidity of the surrounding outside air increases. Moreover, the frost that accumulates on the evaporator not only covers the surface of the plate fin coil type evaporator and deteriorates the heat exchange rate, but also causes frost clogging between the plate fins, which significantly obstructs the ventilation of cold air inside the refrigerator and keeps it cool. This will cause a significant drop in performance.

For this reason, in the past, the refrigerator was temporarily stopped after 4 to 6 hours of cold storage operation, and during this stop period, a well-known defrosting means such as an electric heater method or a hot gas method was used to wipe out the frost. Defrosting heat is forcibly applied to the evaporator from the outside to melt and remove the frost. However, during defrosting, the refrigerator is stopped, and the defrosting heat is supplied from outside by a heater, etc., so it is possible to avoid raising the internal temperature and therefore the product temperature to a certain extent. I can't. Furthermore, when the refrigerator is operated continuously, the amount of frost increases approximately in proportion to the cold storage operation time. Further, the greater the amount of accumulated frost, the longer the defrosting time required for defrosting, and the longer the defrosting time, the greater the rise in the temperature of the products in the warehouse. Considering the above-mentioned conventional operation control method using a temperature controller, the problem of frost formation is that the temperature controller turns off relatively frequently in a light load operation range where the ambient conditions are lower than standard ambient conditions, causing the refrigerator to shut off. stopped,
In addition, since off-cycle frost protection is performed while the refrigerator is stopped, the amount of frost that accumulates during cold storage operation is relatively small. On the other hand, in an overload operating region where the temperature and humidity are higher than the standard ambient conditions, the amount of outside air heat entering increases, so the circulating cold air inside the refrigerator hardly drops below the set temperature of the temperature controller, and the refrigerator is kept in storage mode. It will be in continuous operation for most of the period. For this reason, the amount of accumulated frost increases significantly, and the cold storage performance decreases due to frost clogging even before the defrosting cycle, resulting in a problem in which the rate of increase in product temperature increases.

In this way, with the conventional show case operation control system, there is a problem of overcooling in the light load operation region.
On the other hand, in the overload operation range under harsh ambient conditions such as in summer, the refrigerator is operated continuously, and the amount of accumulated frost during cold storage operation increases significantly, resulting in a significant decrease in cooling performance. This made it extremely difficult to maintain a stable product temperature.

The present invention has been made in consideration of the above points, and its purpose is to solve various problems with conventional operation control methods, and to maintain stable internal storage even when the surrounding conditions change over a wide range while the show case is in operation. To provide a method for controlling the operation of a freezing and refrigerating case in which the temperature of displayed products can be maintained.

According to the present invention, the present invention detects the ambient conditions of the case, and compares them with the standard ambient conditions to reduce the operating rate in light load operation areas where the ambient conditions are low temperature and low humidity, and to reduce the operation rate in overload operation areas where the ambient conditions are hot and humid. This is achieved by setting a high operating rate and performing a duty cycle operation in which the refrigerator is alternately started and stopped periodically.

The present invention will be described in detail below based on illustrated embodiments.

First, FIGS. 4 and 5 show an explanatory diagram of the operation control operation according to the present invention and a schematic diagram of the controller. The controller 14 shown in FIG. 5 has an electronic relay circuit 15 built into a main body 16, and is equipped with a temperature sensor 17 and a humidity sensor 18. For example, as shown by the dotted line in FIG.
It is installed on the top of the case body. Note that 19 is a switch for blinking the interior illumination light 9, 20 is a relay contact inserted in the circuit of the electromagnetic contactor 52C for operating and stopping the refrigerator, and 21 is an adjustment dial. Although the detailed circuit of the electronic relay circuit 15 is not shown, the state of the air surrounding the case detected by the temperature sensor 17 and the humidity sensor 18 is converted into enthalpy, and this is converted into a reference setting value predetermined based on standard ambient conditions. compared to
The circuit is configured to periodically control the relay contact 20 on and off so that the refrigerator is operated in a duty cycle at an operating rate as will be described in detail later, depending on the degree of the deviation. Also, the adjustment dial 21
The standard value of the duty cycle is manually set in advance based on standard ambient conditions according to the specifications of the case, the application, the capacity of the refrigerator, etc. Here, the operation rate refers to the ratio of the refrigerator operating time to the cooling operation time of the case, that is, the distribution ratio of the duty-on time when the contact 20 is on and the duty-off time when the contact 20 is off in the duty cycle. There is. Then, in the electronic relay circuit 15, when the enthalpy of the air surrounding the case is low compared to the reference value, that is, in a low-temperature, low-humidity, light-load operation region, the operation rate is reduced accordingly, and in a high-temperature, high-humidity overload operation region, the operation rate is lowered accordingly. Set the operating rate high. Furthermore, the on/off state of the illumination lamp 9 is detected based on the on/off conditions of the switch 19, and when the illumination lamp 9 is turned off, the operation rate of the refrigerator is corrected to be slightly lower than when it is turned on. Further, the operating rate of the refrigerator can be changed steplessly or stepwise depending on the surrounding conditions of the case. These can be easily implemented using well-known electronic circuit design techniques.

Next, FIG. 6 shows an operation control circuit incorporating the above-mentioned controller 14. This circuit differs from the conventional circuit shown in FIG. 2 in that a controller 14 according to the present invention is inserted in place of the temperature regulator 23I, and the refrigerator is in dual mode during cold storage operation except during the defrosting period. It is operated on a take cycle. Moreover, the operating rate due to this duty cycle operation changes every moment as the surrounding conditions of the case change. Further, FIGS. 7 and 8 show operating characteristics of a meat cutter case employing the controller according to the present invention, as an example. Figures 7 and 8 show the case of the aforementioned stepless setting method and stepwise setting method of the operating rate, respectively, and the characteristic lines D and E represent changes in ambient conditions when the interior lighting is turned on. The set value of the refrigerator operation rate is shown on the characteristic line.
Further, each of the characteristic lines 1, 1, 1, and 1 corresponds to the average temperature of the product obtained by actual measurement from an actual machine test corresponding to the operation rate characteristics 2, 5, 5, 6, and 5, respectively. Furthermore, FIG. 9 shows an operation chart when the show case is actually installed and operated in a store. In the diagram
DCon represents the duty-on time, and DCoff represents the duty-off time.

According to the above-mentioned operation control method of the present invention, the duty cycle operation sets the duty off time for each cycle even during the cold storage operation period, and the off cycle defrosting is performed during the duty cycle off time. It will be done. Therefore, the amount of accumulated frost that accompanies cold storage operation is small, and the evaporator is not clogged with frost, so a sufficient amount of cold air circulation can be ensured and high cold storage performance can be maintained. This also makes it possible to extend the defrosting cycle by energizing the heater, extending defrosting from once every 4 to 6 hours to 12 to 24 hours and once a day. It has become possible to reduce the number of defrosting operations to once or twice. Moreover, since the operation rate of the refrigerator is changed according to changes in the ambient conditions of the case, the temperature of the product can be maintained stably. As shown in Figures 7 and 8, even under severe ambient conditions, it is best to keep the operating rate to a maximum of 90 to 95%, and to continue the duty cycle operation without increasing it to 100%. This is necessary to prevent frost clogging and extend the defrosting cycle. It goes without saying that the present invention is not limited to the illustrated open case, but can also be applied to various other types of freezing and refrigerating cases.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the open show case.
Figure 2 is an operation control circuit diagram using the conventional method, and Figure 3 is a temperature characteristic diagram of the show case using the conventional method.
FIG. 4 is an explanatory diagram of the principle of control operation of the present invention, FIG. 5 is a configuration circuit diagram of a controller used to implement the present invention, FIG. 6 is an operation control circuit diagram employing the controller of FIG. 7 and 8 are operational characteristic diagrams of the show case according to the present invention, and FIG. 9 is an operation chart of the show case. 1... Outer box of the case body, 2... Inner box, 3...
Evaporator, 7...Product, 9...Interior lighting, 14...
... Controller, 15 ... Electronic relay circuit, 17
... Temperature sensor, 18 ... Humidity sensor, 20 ...
Relay contact for controlling the operation and stopping of refrigerators.

Claims (1)

[Scope of Claims] 1. A case for freezing and refrigerating a case in which an evaporator is installed inside the case body, and cool air obtained by exchanging heat with the evaporator by operating a refrigerator is circulated to keep products displayed in the case cool. Detects the ambient conditions and sets the chiller to a low operating rate in light-load operation areas where the ambient conditions are low and low humidity, and a high operating rate in overload operating areas where the ambient conditions are hot and humid, compared to standard ambient conditions. A method for controlling the operation of a frozen/refrigerated open case, characterized in that duty cycle operation is performed by alternately and periodically repeating operation and stop. 2. In the operation control method as set forth in claim 1, there is provided a refrigerating/refrigerating case that detects whether a lighting lamp inside the case is turned on or off, and lowers the operating rate of the refrigerator when the lamp is turned off compared to when the lamp is turned on. Operation control method.