JPS61191849A - Method of operating 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 This invention is a freezing or refrigeration system that installs an evaporator inside the case body and circulates and ventilates the cold air obtained by exchanging heat with the evaporator by operating a refrigeration device to keep the products in the refrigerator cold. Concerning how to operate the showcase of specifications.

In order to maintain the quality of the products, the showcases installed and used in stores such as supermarkets are desired to be able to stably maintain the quality of the products inside at a predetermined refrigeration temperature throughout the entire operating period of the showcase.

The amount of frost that accumulates on the evaporator over the course of operation and the defrosting time required to melt and remove the accumulated frost have a major influence. To discuss this point in detail, first, it is well known that frost forms on the evaporator as the refrigeration system operates, and that this frost covers the surface of the evaporator and accumulates. However, when frost accumulates on the evaporator, it not only reduces the heat exchange efficiency of the evaporator, but also narrows the cross section of the ventilation passage between the fins of the evaporator, making it impossible to obtain a sufficient amount of cold air circulation. This causes the cold storage performance to deteriorate and the product temperature to rise. Moreover, the amount of frost formed above is approximately proportional to the continuous operation time of the refrigeration equipment, and tends to increase as the surrounding conditions of the case become more humid.Furthermore, the cold retention performance of the showcase is affected by evaporation when the amount of frost exceeds the limit. The container becomes clogged with frost and becomes extremely worse. On the other hand, in order to remove the frost accumulated in the evaporator as described above, stop the refrigeration equipment before the amount of frost buildup exceeds the limit, and then defrost the heater in this state.
Defrosting is performed using well-known forced defrosting methods such as hot gas defrosting or air defrosting, but during the defrosting period, the refrigeration equipment is stopped and cold storage is performed. Since defrosting heat is actively applied from the outside, some increase in quality cannot be avoided. Moreover, the greater the amount of frost formation, the greater the amount of heat required for defrosting and the greater the time required for defrosting, which increases the temperature of the product.

By the way, many showcases currently on the market run cold storage operations 4 to 6 times a day, that is, for 4 to 6 hours, in order to remove the frost that has accumulated over the course of cold storage operation. After this, the refrigeration equipment is temporarily stopped, and during this stop period, defrosting heat is applied externally using heater defrosting, hot gas defrosting, etc. to perform forced defrosting, which takes about 30 minutes to accumulate in the evaporator. The frost that is present is being wiped out.

The present invention has been made in view of the above points, and embodiments thereof will be described below with reference to the drawings.

Figure 1 (1) shows the opening (3) for storing and taking out products on the front.
A freezing or refrigerating showcase whose main body is composed of an insulating wall (2) formed with (
7), and an interior (11) equipped with multiple shelves (9) and multiple lights (10) such as fluorescent lights.
), and Suita and suction ports (12), (13), (14), and (15) of both the passages facing each other are formed at both upper and lower ends of the opening, and the first and second passages (6> As shown by the arrows in (8), a two-layer air curtain (At) (A2) with different temperatures is formed at the opening (3>) by the cold air flow and protective air flow circulated by both blowers (5) and (7), respectively. Inside the warehouse (1
1). Surrounded by a broken line (16)
is a refrigeration system, which includes a refrigerant compressor (17) - a condenser (18) -
Liquid electromagnetic valve (19) 7 - temperature type expansion valve (2''0) - constitutes an acid cycle.

(21) is a control device that controls the temperature inside the refrigerator (11);
A temperature sensor (22) that constantly detects the temperature of cold air in the showcase and a liquid electromagnetic valve (19) that controls the supply of liquid refrigerant to the evaporator (4) are connected to the device.

As shown in Figure 2, this device includes a power supply (23) and a processing section (24) that has built-in comparison and timer functions and compares each signal.
and a setting unit (25) that stores each temperature setting value to be controlled and outputs a signal with a time width corresponding to the temperature inside the refrigerator (11);
A day/night switching section (26) that signals when the store is open or closed when the lights (10) are turned on or off, and the temperature sensor <zz>i, which turns on and off according to the signal from the processing section Output section (
27).

Showcase (1) with the next control device (21)
Each temperature side will be explained with reference to FIGS. 3 to 5. In each figure, (L,) is the temperature curve of the circulating cold air detected by the salinity sensor (22), and (L,) is the signal waveform of the output section (27) that controls the opening and closing of the liquid solenoid valve (19). , (L,) is the signal waveform of the day/night switching unit (26), (TS') is the limit setting value during business hours, ('I'D) is the upper limit setting value during business hours, (TN) is the non-business time limit setting value. Lower limit set value at time, (
ID') indicates the lower limit set value during non-business hours, and (6th) indicates the temperature range of automatic setting change at night when the light (10) is turned off.

Figure 3 shows the characteristics of both on/off and night setback control. (TS) is used to turn the output signal (L,) into the OF hand, and when the upper limit setting value (1"D) is used to turn the output signal (L,) into ONL, repeated on/off control is performed.
Due to N, there will be a night setback, and the lower limit i constant value (TN) will be set during non-business hours of the store when the lights (10) are turned off.
The output signal (L,) is turned off at the upper limit setting value (TD'), and the output signal (L,) is turned on at the upper limit setting value (TD') to perform on/off control.

Figure 4 shows the characteristics of the oscillator-off, night setback, and duty cycle controls. ) during on/off control, performs daytime duty cycle control that forcibly closes the liquid solenoid valve (19) and intermittently stops the supply of liquid refrigerant to the evaporator (4). During non-business hours, (TN)((
Turn off the output signal (L,) and turn it on and off between τ, )> (τ, )), and forcefully close the night set pack and liquid solenoid valve (19) to supply liquid refrigerant to the evaporator (4). Each control is performed during the night duty cycle, which stops intermittently.During this duty cycle, the blowers (5) and (7) continue to operate, and during this time, the frost in the evaporator (4>) is circulated. It will be dissolved by the evaporation effect of cold air.

Figure 5 shows the characteristics of override in duty cycle control, where (?R) is the duty cycle temperature width, (LA> is the override signal waveform, and the showcase (?
1) The temperature inside may rise as shown by the chain line, which may adversely affect the product load. In this case, the temperature (('1
'S) + ('1'R) or (IN) + (TR)
), the output signal (L, ) is immediately turned ON, and an override is performed to forcibly return to cooling operation.

Incidentally, the cooling operation is stopped by the next Dewey cycle after the temperature has decreased to (TS) or (TN) ((τ)-(τ,) or (de)-(τm)).

Therefore, according to the present invention, since the supply of liquid refrigerant to the evaporator is periodically stopped for a short time during the cooling operation, the amount of frost on the evaporator increases as the time elapses during the cooling operation. At the same time, during this period, the frost can be slightly reduced by off-cycle defrosting due to the evaporation effect of the circulating cold air, and as a result, the frost can be defrosted without causing a large temperature rise of the circulating cold air, and moreover, the frost can be reduced slightly per day. In addition to reducing the number of defrosting operations, the evaporator mower can be operated at a high heat exchange rate to provide sufficient cooling performance.

[Brief explanation of drawings]

The drawings show an embodiment of the method of operating the showcase of the present invention,
FIG. 1 is a longitudinal sectional view of the showcase, FIG. 2 is a block diagram of the control device, and FIGS. 3 to 5 are characteristic diagrams showing the operation of the control device. (4)...Evaporator, (5)...Blower, (21
)...control device, (22)...temperature sensor,
(24)...processing section, (25)...setting section, (2
6)... Day/night switching section, (27)... Output section. Figure 2 Figure 3

Claims (1)

[Claims] 1. In a showcase that cools the inside of a refrigerator to a predetermined temperature by forcibly circulating cool air that has been heat exchanged in an evaporator using a blower, during cooling operation, the supply of liquid refrigerant to the evaporator is periodically interrupted for a short period of time. A method of operating a showcase, in which the blower is stopped temporarily, and the blower continues to operate during this period to perform off-cycle defrosting of the evaporator.