JPS629169A - Control system of defrostation of open showcase - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a defrosting control system for an open showcase.

[Prior art and its problems]

As is well known, in this type of open showcase, the frost that forms on the surface of the cooler gradually increases as time passes during cold storage operation, resulting in a decrease in cold storage performance. For this reason, the cold storage operation is usually temporarily stopped several times a day to defrost the ice. As the defrosting means in this case, various pan defrosting methods are known, such as a drawer heating method, a hot gas defrosting method, and an air defrosting method using outside air heat.

By the way, as a conventional defrosting control method, a constant defrosting cycle Jv K L/taka is set in advance by a timer system 8+c, regardless of the amount of frost formed on the cooler.

For example, defrosting is performed by switching from cold storage operation to defrosting every 6 hours or every 12 hours.

However, with this method of defrosting at predetermined intervals using timer control, even if the defrosting cycle is set in advance to match average ambient conditions, it will not work in open showcases that are operated throughout the year. Since the ambient conditions constantly change, it is not possible to respond to variations in the ambient conditions.

In other words, in the case of severe ambient conditions such as higher temperature and higher humidity than the preset ambient conditions, the amount of frost on the cooler increases in the early hours and the cooling capacity decreases. Since defrosting is not performed until then, the temperature inside the refrigerator and, therefore, the temperature of the products displayed inside the refrigerator increases significantly, leading to deterioration in freshness. On the other hand, if the ambient conditions are low temperature and low humidity, defrosting will occur at the scheduled time even though the amount of frost is small and there is sufficient cooling capacity, resulting in excessive defrosting. When the temperature inside the refrigerator increases, the temperature of the products displayed in the refrigerator increases, causing a problem that accelerates the deterioration of the freshness of the products. By accurately detecting the point at which the cooling capacity reaches the limit due to frost buildup on the refrigerator, defrosting is performed in a timely manner, thereby eliminating excess or underdefrosting and minimizing loss of freshness of products in the warehouse. The purpose of the present invention is to provide a demand-type defrosting control system that allows

[Key points of the invention]

In order to achieve the above object, the present invention includes a temperature sensor installed in the refrigerant pipe leading from the expansion valve to the exit of the case, or in the cooling fin of the cooler to detect the temperature of the core;
and a control unit that takes the temperature detection value of the temperature sensor as input and compares it with a predetermined set value, and outputs a defrosting signal based on the comparison result, and the detected value of the temperature sensor described above is the set value. This system is designed to defrost the cooler by outputting a defrost signal from the control unit when the temperature exceeds the frost limit, thereby accurately detecting the frosting range of the cooler that can maintain the appropriate cooling capacity. By performing defrosting, reducing the number of times of defrosting and reducing the heat cycle caused by defrosting, it is possible to maintain the freshness of the products in the refrigerator.

[Embodiments of the invention]

Fig. 1 is a block diagram of an open showcase according to an embodiment of the present invention, Fig. 2 is a block diagram of a defrosting control system, and Fig. 3 is a block diagram of a defrosting control system.
The figure shows a time chart of the defrosting control operation. First, in FIG. 1, 1 is the outer case of the open showcase, 2 is the inner box that defines the internal product display room 3, and a cold air circulation duct 4 is formed between the outer box 1 and the inner box. A cooler 6 connected to a refrigerator 5 and a blower fan 7 are installed here. With the configuration so far, the refrigerator 5 and fan 7 are operated during cold storage operation, and the cooled air exchanges heat with the cooler 6 and circulates through the duct 4 as shown by arrow A. A cold air curtain is blown from the air curtain suita port 4a toward the suction port 4b. Here, in the cold air circulation duct 4, a defrosting heater 8 as a defrosting means is installed on the inlet side of the cooler 6. Further, a refrigerant circulation path is formed by the compressor 5, an expansion valve 9, and a cooler 6, and an expansion valve 9 is provided in a refrigerant pipe 1o that connects the discharge side of the refrigerator 5 and the cooler 6. A temperature sensor 9 is arranged in the refrigerant pipe of the cooler 6 to detect the temperature of the core.

The sensor 9 may also be attached to a refrigerant pipe that runs from the expansion valve through the cooler 6 to the outlet of the showcase, and the same temperature is detected. The temperature sensor 9 is connected to a control section 12 built into the case as shown in FIG.

As will be described later, this control unit 12 inputs the temperature detection value t of the temperature sensor 9, compares and calculates this detection value t and a predetermined set value during the cold preservation period, and based on the calculation result, performs a calculation as shown in FIG. It plays the role of outputting defrosting commands to the refrigerator 5 and defrosting heater 8 shown.

Next, the defrosting control operation with the above configuration will be explained based on the time chart shown in FIG. 3. In other words, as shown in Fig. 8, when the frost formation on the cooler 6 gradually increases as time passes during cold storage operation, the ventilation passages in the cooler become clogged with frost, increasing ventilation resistance and reducing the amount of ventilation inside the duct. gradually decreases. Also, when the amount of ventilation in the duct decreases, the load on the cooler 6 decreases, but on the other hand, the refrigerating capacity of the refrigerator remains the same, so the expansion valve 9 is closed. The temperature of the pipe leading to the l'fX outlet begins to drop. In other words, the temperature detection value t of the temperature sensor 11 gradually decreases with the passage of time.

On the other hand, from another actual machine test, we actually measured the relationship between the temperature that has risen to the cooler and the above-mentioned rising temperature, and from this measurement result, we determined the temperature TM when the frost formation limit Q was reached. The value TM is set as a set value in the control unit 12 that is used as fertilizer. When the temperature detected by the temperature sensor 9 reaches the temperature corresponding to the N quantity limit Q, the control unit 12 outputs a defrosting signal, switches from cold preservation operation to defrosting based on this defrosting command, and freezes The machine 5 is stopped and the defrosting heater 8 is energized.

In addition, the control unit 12 calculates the ratio of the detected temperature to the time, and inputs the ratio of the temperature to the time when the frosting limit is reached from the experimental results as a set value, and also calculates the ratio of the temperature to the time detected during the cooling period. It performs a comparison calculation between the ratio and the above set value, and outputs a defrosting command based on the calculation result. With this configuration, when the air temperature in the duct rises and the ratio of temperature to time reaches a set value, the control unit 12 can output a defrosting signal.

At the end of defrosting, for example, the temperature detected by the temperature sensor 11 is monitored, and when this temperature value reaches a predetermined temperature, it is determined that the frost has disappeared and the cold storage operation is restarted.

Although the illustrated example uses the defrosting heater 8 as the defrosting means, the same applies to cases where other defrosting means such as a hot gas defrosting method are employed.

〔Effect of the invention〕

As described above, according to the present invention, the expansion valve
It is installed in the refrigerant piping leading to the case outlet or the cooling fins of the cooler to detect the air temperature in the core part.The temperature detection value of the temperature sensor is input and compared with a predetermined set value, and based on the comparison result. The controller has a control section that outputs a defrosting signal, and when the detected value of the temperature sensor exceeds a predetermined set value, the control section outputs a defrosting signal and defrosts the cooler. As a result, the timing for defrosting the cooler is such that the defrost command is output when the amount of nitrogen deposited in the cooler reaches the limit amount in terms of cooling capacity, regardless of the length of the cold storage operation. .

In other words, frost formation M changes depending on the ambient conditions during cold storage operation.
It is possible to accurately determine the amount of defrost and defrost only when defrosting is necessary, thus eliminating the need for too much or too little defrosting, minimizing unnecessary temperature rises of products in the warehouse, and improving product quality. It is possible to provide an effective defrosting control method for an open shutter case that can be maintained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an open zipper case according to an embodiment of the present invention, FIG. 2 is a defrosting control block diagram, and FIG. 3 is a time chart of control operations. In the figure, 4...Cold air circulation ventilation duct, 4a...Air curtain outlet, 6...Cooler, 7...Blower fan, 8...
... Defrost heater, 9... Expansion valve, 10... Refrigerant piping, 11... Temperature sensor, 12... Control unit. Figure 1 Operating hours Figure 3

Claims (1)

[Claims] 1) A cooler and a blower fan connected to an expansion valve in the refrigerant circulation path are installed in a cold air circulation ventilation duct defined in the case, and during cold preservation operation, heat exchange with the cooler is provided. A defrosting control system for an open showcase in which cold air cooled by exchange is circulated and ventilated to form a cold air curtain in front of the case, and the defrosting control system is a defrosting control system for an open showcase that circulates and ventilates cold air cooled by exchange to form a cold air curtain in front of the case. A temperature sensor that is installed on the cooling fin to detect the temperature of that part, and a control unit that takes the temperature detection value of this temperature sensor as input and compares it with a predetermined set value, and outputs a defrosting signal based on the comparison result. A defrosting control method for an open showcase, characterized in that when the detected value of the temperature sensor exceeds the set value, a defrosting signal is output from the control unit to defrost the cooler. . 2) In the defrosting control method for an open showcase as described in claim 1, the control unit calculates the ratio of the detected temperature value to time, and the ratio of the detected temperature value to time is a predetermined set value. An open showcase defrost control system that outputs a defrost signal from the control unit when the temperature exceeds the limit.