JPS5812510B2 - Frost detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a frost detection method that detects the presence or absence of frost formation and the amount of frost formation in a cooler such as a showcase, and outputs a defrosting signal.

Currently, large-capacity food showcases are widely used in food superstores, markets, etc., and in these showcases, the displayed food inside the showcase is cooled by a stream of cold air circulating through a cooler.

A major problem in cooling the inside of the showcase is that frost forms on the cooler, reducing its cooling efficiency, and therefore defrosting is normally performed at regular intervals using a timer.

Defrosting methods for such coolers include single-heater method, hot gas method, and off-cycle method, but as mentioned above, defrosting is carried out at regular intervals regardless of the frost formation state. Therefore, the disadvantage is that the loss in power consumption is extremely large compared to the case where defrosting is performed one by one by observing frost formation.

Therefore, as means for detecting frost formation on a cooler, methods using an electric device and methods using an optical guide using a light guide have been proposed.

The present invention reliably detects the above frost formation and outputs it as a frost formation signal (defrost signal), and uses this defrost signal to defrost the cooler using a heater method, hot gas method, off-cycle method, etc. This is intended to significantly reduce power consumption, and according to the present invention, it is possible to reduce power consumption by as much as 30%.

In addition, in implementing the present invention, the temperature signal inside the case is constantly recorded on chart paper, and when an abnormality occurs in this temperature signal, it can be captured as a defrosting signal, so that defrosting management of coolers such as showcases can be performed. It is effective for

The principle of the method of the present invention will be explained below.

The decrease in the heat exchange rate (cooling effect) of the cooler is caused by the following (A), (
It consists of factors B) and (C).

(5) During normal operation of the fan and compressor (1)
Frost or ice forms on the cooling coils and fins due to humidity and moisture in the air inside the case (warehouse) and outside, which prevents heat exchange on the surfaces of the cooling coils and fins.

(2) If frost formation or icing occurs when the airflow passes through the cooling coil or fins, the airflow volume will be lower than a predetermined value and heat exchange will be reduced.

If left unattended, the temperature inside the refrigerator will rise.

(B) If the fan stops or cannot send the predetermined air volume under any of the conditions, the temperature inside the refrigerator will rise.

(C) If the compressor fails or stops, or if the cooling capacity drops below a predetermined level due to any condition, the temperature inside the refrigerator will rise.

Therefore, in the present invention, the temperature rise signal A inside the case detects that the cooling effect has decreased due to frost formation or icing on the cooling coil or fins, the signal B detects that the fan is operating normally, and the compressor is operating normally. A defrosting signal D is generated by combining the signal C that detects a certain condition.

As the means for outputting the above-mentioned signals B and C, any commonly used means can be used, but as the means for outputting the signal A, a temperature sensing device consisting of a combination of a temperature sensor such as a thermistor and a heating element such as an electric heating element inside the case is used. A sensor may be used to extract the normal amount flowing through the heating element in response to the temperature inside the case as a temperature signal inside the case.

In the following, the method of the invention will be explained by means of embodiments shown in the drawings.

In Figure 1, 1 is a showcase with a cooler 2 at the bottom.
and a fan 3 are disposed, and the fan 3 causes a cool air flow 4 to pass through the cooler 2 to recycle the inside of the case.

5 shows the exhibits inside the case.

Reference numeral 6 denotes a temperature sensor in the case, and as shown in FIG. 2, it has a structure in which a temperature sensor 7 such as a thermistor and a heating element 8 such as an electric heating element placed close to the temperature sensor 7 are surrounded by a single shield 6.

The temperature sensor 6 inside the case controls the amount of heat generated by the heating element 8 so that the temperature sensed inside the case by the thermistor 7 is constant, so the amount of heat generated by the heating element 8 changes as the temperature inside the case changes. will increase or decrease, and by plotting this energization amount on chart paper, etc., it is possible to detect a rise in the temperature inside the case.

As shown in Figures 1 and 3, signal B detects normal operation of fan 3, signal C detects normal operation of compressor 9 operating cooler 2, and temperature rise inside the case from sensor 6. The signal A is input to the amplifier 10 at the same time.

Therefore, when the temperature signal from the sensor 6 is a signal indicating a temperature rise inside the case while the detection signals B and C indicating that the fan and compressor are operating normally are input to the amplifier 10, This signal is output as a defrosting signal D.

For example, as shown in FIG. 4, the temperature rise signal A1 inside the case
Fan normal operation signal B1 Compressor normal operation signal C
Relays a, b, and C operated by defrosting signal circuit 11
If they are incorporated in series, the defrosting output signal D will be obtained only when the signals A, B, and C are input at the same time.

The present inventor's results show that the temperature curve D measured by the thermometer in the showcase 1 shows a wavy back and forth between 0°C and -5°C, but this is due to the fact that the thermostat is turned on at 0°C and the compressor is turned on. 9 is activated, the thermostat is cut off at -5°C, and the compressor 9 is stopped.

On the other hand, the temperature signal from the sensor 6 is obtained as a curve E which is an inversion of the curve D.

Therefore, when frost formed on the cooler 2, an abnormal fall E' was immediately observed in the curve E, whereas no rise was observed for a while in the curve D, and an abnormal rise D was observed after a period of time had passed, and the curve E This means that the temperature rise inside the case and the frost formation were predictively detected, which can be said to demonstrate the effectiveness of the present invention.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment in which the present invention is applied to a showcase, FIG. 2 is an explanatory diagram of the same sensor as above, FIG. 3 is a block diagram of the detection circuit of FIG. 1, and FIG. FIG. 1 is an output circuit diagram, and FIG. 5 is a chart showing experimental results according to the method of the present invention.・1... Showcase, 2... Cooler, 3... Fan, 4... Cold air flow, 5...
...Exhibit product, 6...Sensor, 7...
...Thermistor, 8... Heating element, 9...
... Compressor, 10... Multiplier, 11
...Output circuit.

Claims (1)

[Claims] 1 A device that cools the inside of a case by circulating airflow through a cooler using a fan, which consists of a combination of a temperature sensor such as a thermistor and a heating element such as an electric heating element placed inside the case, and is used to cool the inside of the case by circulating airflow through a cooler. The temperature rise signal inside the case from the temperature sensing sensor which corresponds to the amount of current flowing through the heating element is extracted as a temperature signal inside the case, the normal operation signal of the above fan, and the normal operation of the compressor that operates the cooler. A method for detecting frost formation on a cooler, characterized in that the signals are combined and captured as a frost formation signal.