JPS6115062A - Defrostation system 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 method for an open showcase using cold air circulation.

[Prior art and its problems]

As defrosting methods for analogous open showcases, in addition to the conventional hot gas defrosting method and heater defrosting method, the heat retained in the outside air around the showcase is used as a defrosting heat source, and the surrounding outside air is used during defrosting. A so-called fan defrosting method, which defrosts the cooler by actively sucking air into a circulation ventilation duct inside the case, is also known and has been put into practical use in some cases. (Publication of patent application in 1973)
2-2 (Refer to Publication No. 1693) By the way, the fan defrosting method described above defrosts by using the enthalpy of the outside air as a defrosting heat source. The defrosting time from the start to the end of frost is long (it takes a long time, especially when the ambient temperature is 0℃)
If the temperature is lowered below, defrosting will not proceed. On the other hand, since the refrigerator is stopped during the defrosting time, the temperature of meat, fresh fish, and other products displayed in the showcase increases as the defrosting time increases, resulting in quality deterioration. invite,
In general, it is said that it is desirable to limit the defrosting time to within 30 minutes.
If the frost cannot be completely removed even after 0 minutes have elapsed, a control system is adopted in which the defrosting operation is forcibly returned to the cold storage operation using timer control. For this reason, in the fan defrosting method described above, if defrosting is performed when the outside temperature is low, the frost will remain unmelted and the cooler will enter cold storage operation with frost still attached to it, resulting in a decrease in cooling performance. Cause. From this point of view, an electric defrost heater is installed in advance near the cooler in the showcase as an auxiliary heat source, and the defrost heater is energized at the same time as the fan defrosting described above during defrosting. Attempts have been made to reduce defrosting time. However, like this combined defrosting method,
If the defrosting heater is simply energized during defrosting, unless the ambient temperature is low, the amount of heat applied to the case will be excessive, causing heat shock to the products in the refrigerator and unnecessarily deteriorating the quality of the products. Not only that, but power consumption also increases more than necessary.

[Purpose of the invention] This invention was made in consideration of the above points, and its purpose is to compensate for the weaknesses of the fan defrosting method by using a defrosting heater in combination with the fan defrosting method, while also being able to reduce the heat shock given to the products in the refrigerator. To provide a defrosting system capable of completing defrosting within a desired time even when the ambient outside air temperature is as low as possible. [Key points of the invention]

In order to achieve the above object, the present invention additionally provides a defrost heater on the upstream side of the cooler in the circulation ventilation duct defined in the showcase, and also installs a defrost heater in the power supply circuit of the defrost heater. In addition to drawing outside air into the circulation ventilation duct during defrosting, the output of the defrosting heater is controlled via the energization control means based on the detected value of the ambient temperature of the case body. The energization of the heater is controlled so that the heater output increases as the ambient temperature decreases.

[Embodiments of the invention]

FIGS. 1 and 2 each show the structure and cold storage operation of an open showcase according to the present invention. The ventilation state during defrosting, FIGS. 3 and 4 are defrosting heater control circuit diagrams of different embodiments of the present invention, and FIG. 5 is a characteristic diagram of defrosting operation. In Figures 1 and 2, 1 is an outer box of the case main body with an open front, 2 is an inner box, and two layers of circulation ventilation ducts 3 and 4 are defined between the inner box and the outer box. A cooler 5, which is an evaporator of the refrigerator, and an inner fan 6 are installed in the circulation ventilation duct 3 in the inner layer, and a reversible outer fan 7 is installed in the circulation ventilation duct 4 in the outer layer. ing. Further, on the upstream side of the cooler 4 in the circulation ventilation duct 3, there is an electric defrost heater 8, and a defrost heater energization controller 9, which will be described in detail later, is located in a canopy part of the upper front member of the case body. is installed together with the ambient temperature detection sensor 11. With the above configuration, during cold storage operation, the cooler 5. Blow fan 6.
7, the cold air is circulated in the same direction in the circulation ventilation duct 3.4 as shown by the solid line arrow in Fig. 1, and a two-layer cold air curtain is blown out from the front opening of the case body. This blocks outside heat from entering the warehouse and keeps the products displayed on the product display shelves 10 cool. On the other hand, when the predetermined cold storage operation time has elapsed and the cold storage operation is switched to defrosting under timer control, the refrigerator stops and the outer fan 7 switches to reverse operation while the inner fan 6 continues to operate. As shown by the dotted line arrow in FIG. It is reversed and sucked into the inner circulation ventilation duct 3 and flows through the cooler 5. Thereby, the outside air with high enthalpy gives heat to the cooler 5 and defrosts it. Next, FIG. 3 shows the control operation of the defrosting heater 8 newly installed in the showcase according to the present invention and the energization controller 9 that controls the energization of the defrosting heater. This will be explained together with the control circuit shown in FIG. In Figure 3,
12 is a defrost timer that switches the timer contact from "cold preservation" to "defrost" so as to issue a defrost command at a predetermined cycle; 13 is T and R connected in series with the defrost heater 8 and inserted in the circuit;
14 is an ambient temperature sensor 1, which is a two-way three-terminal cyrisk as a current control element well known as IAC (product name).
This is a control unit that inputs a temperature detection value of 0 and provides a gate control signal to the thyristor 13, and the thyristor 1
By gate controlling 3, the output of the defrosting heater 8 is controlled by changing its energization rate. Here, the operating temperature is 0.
The control characteristics of the defrosting heater using the circuit shown in FIG. 3 for oven cases for meat and fresh fish at ℃ are shown in FIG. 5, that is, represented by the defrosting heater output characteristic line A or B in FIG. As shown in FIG.
Output starts when the ambient temperature drops to 5℃, and increases as the ambient temperature decreases so that it reaches 100% output when the ambient temperature drops to the same temperature as the showcase operating temperature. It is linearly controlled. As a result, in combination with the fan defrosting described in FIG. 2, the defrosting time could be completed within 30 minutes as shown by characteristic line C. Note that the characteristic AID represents the defrosting time required when the defrosting heater is not used. The embodiment shown in FIG. 4 employs a duty cycle timer as the defrosting heater energization control means to control the energization of the defrosting heater 8. Reference numeral 15 is this duty cycle timer, and the duty cycle timer is used as the defrosting heater energization control means. The timer contact inserted in the power supply circuit No. 8 is controlled to turn on and off. In this case, the duty cycle timer 15 is turned on via the MUS section 14 according to the ambient temperature at that time. By changing the off period, the energization rate to the defrosting heater 8, that is, the output of the heater, can be controlled as shown by characteristic line A or B in FIG. 5. In addition to the above, for example, a chopper control method may be employed as the defrosting heater energization control means. As mentioned above, by controlling the output of the defrost heater, which is also used as an auxiliary heat source for the fan defrost method, according to the ambient outside temperature at that time, the power consumption of the defrost heater can be reduced to the minimum required power. Defrosting could be completed within the scheduled time even at low ambient temperatures without causing heat shock to the products in the warehouse.

【Effect of the invention】

As described above, according to the present invention, a defrosting heater is additionally provided on the upstream side of the cooler in the circulation ventilation duct, and a power supply control means for the heater is provided in the power supply circuit of the defrosting heater. In addition to sucking outside air into the circulation ventilation duct in the event of frost, the output of the defrosting heater increases as the ambient temperature decreases based on the detected value of the ambient temperature of the case body via the energization control means. By controlling the energization of the heater, even when defrosting at low ambient air temperatures, defrosting can be done within the desired time with minimal power consumption and less heat shock than products in the refrigerator. Frost can be terminated.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams showing the state of ventilation inside the case during cold storage operation and defrosting of the open showcase according to the present invention, respectively, and FIGS. 3 and 4 are diagrams of different embodiments of the present invention, respectively. The defrosting heater control circuit diagram, FIG. 5, is a characteristic diagram of defrosting according to the method of the present invention.

Claims (1)

[Claims] 1) A cooler and a blower fan are provided in a circulation ventilation duct defined between an inner box and an outer box of the front-open case body,
When switching from cold storage operation to defrosting mode, the cooler is stopped and the blower fan is operated to draw outside air through the open surface of the case body into the circulation ventilation duct, and transfer the heat held by the outside air to the cooler. In the open showcase defrosting method, which defrosts the temperature by applying a
The power supply circuit of the defrosting heater is provided with heater energization control means, and when defrosting, the energization control means is controlled based on the detected value of the ambient temperature of the case body, in addition to drawing outside air into the circulation ventilation duct. A defrosting control method for an open showcase, characterized in that the output of the defrosting heater is controlled so that the output of the defrosting heater increases as the ambient temperature decreases. 2) In the defrosting method according to claim 1,
Based on the usage temperature of the showcase, the defrost heater starts energizing when the ambient temperature of the showcase drops below a predetermined temperature, and the output reaches 100% when the ambient temperature drops to around the usage temperature of the showcase. A defrosting control method for an open showcase characterized by controlling the energization of a defrosting heater so that the following is achieved.