JPS6024385B2 - Defrost control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a defrosting control device that efficiently defrosts freezing and refrigerating equipment such as an open showcase.

Conventionally, defrosting of the cooler of refrigerator/freezer equipment was performed at fixed time intervals using a timer device.

The defrosting time interval using this method is generally determined based on the operating conditions that cause the most frost on the food, so it is not suitable for cooling equipment for frozen foods with low management target temperatures, such as ice cream, where spring frost occurs very early and in large amounts. This is significant because of the need to defrost reliably, but in open showcases for meat, fresh fish, dairy products, fruits and vegetables, etc., where the target temperature is higher, fog formation is much greater than this. Defrosting is performed even when there is little need for defrosting. This was often inconvenient from the standpoint of product temperature control or energy saving. In recent years, this method has been improved and is now widely used in home refrigerators, etc., by integrating the cumulative operation time of the refrigerator, that is, the closing time of the internal temperature controller, and then adjusting the cumulative operating time of the refrigerator to a predetermined value. There is a method to start defrosting when the frost is reached.

This method eliminates the drawbacks of the previous method to some extent because it provides a defrosting interval commensurate with the load on the cooler, and is simple and ingenious as the only accessory device is a time calculator. It has its drawbacks. That is, when the refrigerator starts intermittent operation, when the refrigerator stops, the frost layer on the heat transfer surface of the cooler naturally partially melts, the density of the frost increases, and the thickness of the frost layer decreases.

Furthermore, if the operating rate of the refrigerator becomes smaller and the stop time becomes longer relative to the operating time, the fog layer may hardly grow. Since the defrosting method based on the operation time integration cannot distinguish the difference in the fogging situation depending on the operation rate, the integration time must be set assuming the case of continuous operation, which is the worst condition.

Therefore, in practical operation, the defrosting frequency becomes higher than necessary. For example, open showcases installed in supermarkets etc. have large entrances, so the outside air load is very large, so a temperature controller is used to stop the refrigerator or stop the flow of cold soot from the cooler. Then, the inlet air temperature of the cooler installed in the air passage of the open showcase immediately rises, and the frost on the cooler quickly melts. In such a cooling system, this method results in defrosting more frequently than necessary. This method is effective for appliances with closed cooling compartments such as household refrigerators, but for example in open showcases where the inlet air temperature of the cooler rises immediately when cooling operation is stopped. Since the frequency of defrosting is higher than necessary for the cooling system, it cannot be said to be a very effective defrosting method.

On the other hand, in showcases for frozen foods such as ice cream, the operating rate is very high because the management target temperature is low, and the defrosting interval is therefore short.

Conventionally, defrosting of such showcases is carried out by setting a timer device three times at approximately fixed times: before the store opens, immediately after the store closes, and at night. This is to avoid that if defrosting is performed while the store is open, the internal temperature will rise too much and have a negative impact on the products. However, the method of determining the defrosting interval based on the cumulative operating time or the method that only takes the operating rate into account causes the inconvenience of defrosting while the store is open.
Therefore, if the management target temperature is very low, defrosting using a timer is reasonable. The present invention has been made to improve the above-mentioned drawbacks of the conventional examples, and the time interval for defrosting (hereinafter referred to as the defrost interval) is determined by changing the time period during which the cooler is performing cooling operation, that is, cooling operation. In addition to obtaining the optimal defrosting start time by changing the operating rate (hereinafter referred to as the operation rate), if the target temperature of the controlled object is below a certain temperature, defrosting is performed at regular intervals, ensuring safety and energy savings. The purpose of the present invention is to provide a defrosting control device that performs optimal defrosting.

In order to clarify the advantages of the present invention, the algorithm for determining the defrosting start time will be explained in detail below.

FIG. 1 is a diagram showing the operating characteristics of the cooling system for an open showcase obtained through experiments. In the figure, the horizontal axis represents the elapsed time after defrosting is completed, and the vertical axis represents the operating rate. A and B use the difference in air conditions around the open showcase as a parameter, and A is a case where the enthalpy of the surrounding air is higher than B. FIG. 2 is an explanatory diagram showing the relationship between the operating rate and the optimum defrosting interval based on the experiment shown in FIG. 1.

C in the figure shows the case where defrosting is performed when the cumulative operating time reaches the set defrosting interval in the conventional example, for example, the operating rate is 50.
% is twice the defrost interval during continuous operation, and the operating rate is 40
% is 2. This indicates that it will become a sound. Set the defrost interval to 1 and set the operation rate to LO for the defrost interval during continuous operation.
Then, this relationship can be expressed as a hyperbola of 1=lo/ (0≦≦1). However, as mentioned above, in such a case, the defrosting frequency will be higher than necessary. D is a diagram showing the relationship between the defrosting interval and the operating rate according to the present invention, in which the defrosting interval is determined by taking the operating rate shown in FIG. 1 into account. In this diagram, the operating rate is 50%.
In this example, the defrosting interval is 35 times longer than continuous operation. Such characteristic curves are largely derived from experiments, as shown in FIG. 1, and are specific to each individual showcase and its cooling system. Furthermore, if the management target temperature is below a certain value, it is necessary to automatically shift to a defrosting interval using a timer.

FIG. 3 is an overall configuration diagram showing an embodiment in which a defrosting control device based on the defrosting control method of the present invention is applied to a cooling system for an open showcase.

1 is an open showcase as a load, 2 is a refrigerator as a cooling heat source, 3 is a cold soot flow path, 4 is a refrigerant cutoff valve disposed in the refrigerator flow path 3, 5 is a soot expansion valve, and 6 is a soot expansion valve. A cooler disposed in the air passage of the open showcase 1, 7 a defrosting means for melting the frost on the cooler 5, 8 a temperature detector for detecting the temperature inside the open showcase, 9 is a defrost control device.

Next, the operation will be explained. The cold butterfly compressed in the refrigerator 2 passes through the refrigerant flow path 3, and if the cutoff valve 4 is open, the pressure is reduced by the expansion valve 5, evaporates in the cooler 6, and passes through the air path inside the open showcase 1. The air is cooled, becomes low-pressure cold soot gas, and returns to the refrigerator 2. Although only one open showcase is connected in FIG. 3 for ease of understanding, it is common for a plurality of oven showcases to be connected to one refrigerator. The temperature detector 8 detects the temperature inside the open showcase 1, and the defrost control device 9 receives the signal from the detector 8, opens and closes the shutoff valve 4, and adjusts the temperature inside the open showcase 1. conduct.

In addition, the defrosting control device 9 integrates the open time of the shutoff valve 4 and determines the cooling operation ratio (hereinafter referred to as operation ratio) of the open showcase 1.
Calculate. To determine the timing to start defrosting, first determine the set value of the cumulative opening time of the shutoff valve 4 based on the operating rate starting from the end of the previous defrosting operation, and then set the cumulative opening time of the shutoff valve 4 to reach the set value. When this occurs, the defrosting control device 9 outputs a defrosting signal to the defrosting means. The operation of the defrosting control device 9 will be described in detail below. FIG. 4 is a block diagram showing the configuration of one embodiment of the defrosting control device 9. In the figure, reference numeral 11 denotes an internal temperature signal input line, into which a signal from the temperature sensor 8 of FIG. 1 is input.
Reference numeral 12 denotes a temperature control circuit, which compares the temperature signal 11 with the set temperature of a temperature setting device 21 that sets the management target temperature inside the refrigerator, and if the former exceeds the latter, a temperature control signal 19 ( 3) is outputted via the gate circuit 18.

If the former is lower than the latter, a temperature control signal 10 (closing signal for the shutoff valve 4 in FIG. 3) for turning off the cooling means is similarly output. Reference numeral 13 denotes a first timer circuit that integrates the operating time since the end of the previous defrosting, that is, the time of the temperature control signal 19 for opening the cutoff valve 4.

Reference numeral 14 denotes a second timer circuit that integrates the elapsed time from the time when the previous defrosting ended to the present time.

Reference numeral 15 denotes an operating rate calculation circuit which divides the integrated value of the operating time by the elapsed time to calculate the operating rate.

17 is a defrost interval setting device to set the defrost interval time when continuous operation is to be performed.

Reference numeral 16 denotes a defrosting interval determining circuit, which gates the operating rate calculation result output of the operating rate calculation circuit 15, the set value output of the defrosting interval setting device 17, and the operating time integrated value output of the first timer circuit 13. It is input through the gate 24a of the circuit 24.

First, it is determined whether the integrated value of the operating time has reached the defrost interval setting value. If this is not achieved, defrosting is not started and the temperature check operation is continued. If this is reached, then the operating rate is determined. For example, the operating rate is 100% to 8
If it is 0%, the defrost interval extension coefficient is set to 1 and defrosting is started immediately. Next, when the operating rate is 80 to 60%, the defrost interval extension coefficient is set to 1.2. For example, if the setting value of the defrost interval setting device 7 is 10 hours, this is multiplied by a coefficient of 1.2 to set the above-mentioned value. This means that the value is considered to be one hour. In other words, defrosting will be started when the cumulative value of the operating time has increased by two more hours. Similarly, the driving rate is 6
It goes without saying that even when the value is 0% or less, the above-described operation can be performed by defining the defrost interval extension coefficient. As mentioned above, the relationship between the operating rate and the defrosting interval extension coefficient differs for each open showcase, so it is necessary to collect them through experiments and define each value in advance. Of course, in order to provide versatility, it is also possible to provide a setting means that can set the operating rate and the coefficient in several stages. Now, by the above-described operation, the defrost interval determining circuit 16 outputs the defrost signal 20, and the defrosting means 7 shown in FIG. 3 is operated to perform defrosting.

At the same time, the gate circuit 18 is opened and the temperature control signal 19 is closed. Reference numeral 22 denotes a periodic defrosting temperature setting device which distinguishes that periodic defrosting is to be performed when the management target temperature falls below this set value.

That is, the setting value of the regular defrosting temperature setting device 22 is compared with the setting value of the temperature setting device 21 in the comparison circuit 23, and if the former is lower than the latter, the defrosting start time is determined according to the above-mentioned procedure. Next, if the former exceeds the latter, it means that the control target temperature is extremely low, and it is necessary to perform regular defrosting. It operates to output the calculation result of %. Further, the gate circuit 24 has a gate 24b.
is opened and outputs the elapsed time data of the timer circuit 14 to the defrosting interval determining circuit 16. As a result, the defrost interval determination circuit 16 outputs the defrost signal 20 to perform defrosting when the elapsed time reaches the set value of the defrost interval determiner 17.

In other words, in this case, defrosting is performed at regular intervals. In the above embodiment, the defrosting interval is set by the setting device, but since this defrosting interval is almost determined by the management target temperature, it is also possible to configure the defrosting interval to be determined by the set temperature of the temperature setting device 21. . For example, there is a management target temperature suitable for meat, fresh fish, etc., and the defrosting interval applicable to this temperature range is generally known, so there is no problem in determining the defrosting interval based on the management target temperature. That is, by removing the defrosting interval setting device 17 and inputting the output of the temperature setting device 21 to the defrosting interval determining circuit 16 instead, this can be easily realized and the configuration can be made even simpler. Furthermore, according to the present invention, if the operating rate is extremely low, there may be cases where defrosting is not required at all. However, for example, the timer circuits 13 and 14, the operation rate calculation circuit 15, the defrost interval setting device 17, the defrost interval determining circuit 16, etc. may malfunction or break down, and in this case, the necessary defrosting may not be performed. Alternatively, there is a risk that it may be left undefrosted for a very long time. Therefore, in order to prevent this, it is also possible to further provide a timer means to measure the time so that, for example, defrosting can be performed once every two hours. Although the configuration of the present invention is as described above, the functions of calculation, comparison, and judgment can be performed using microcomputers, which have recently become rapidly popular, making it possible to realize advanced functions at a low cost and with high reliability. .

As described above, according to the present invention, it is possible to always select an efficient defrosting start time, and it is possible to obtain practically effective effects such as power saving and preventing the number of temperature rises in the refrigerator.

[Brief explanation of drawings]

Fig. 1 is an operating characteristic diagram of the cooling system of an open showcase, Fig. 2 is an explanatory diagram showing the relationship between the operating rate and the optimum defrosting interval, and Fig. 3 is a defrosting control device using the defrosting control method of the present invention. FIG. 4 is a block diagram showing the structure of an embodiment of the defrosting control device. In the figure, 4 is a branch valve, 7 is a defrosting means, 8 is a temperature detector, 12 is a temperature adjustment circuit, 13 is a first timer circuit,
14 is a second timer circuit, 15 is an operating rate calculation circuit, 1
6 is a defrosting interval determining circuit, 17 is a defrosting interval setting device, 21 is a temperature setting device, 22 is a fixed temperature setting device,
23 is a comparator. Note that the same reference numerals in the figures indicate the same or corresponding parts. Fig. 1 Fig. 2 Fig. 4 Weave

Claims (1)

[Scope of Claims] 1. Control target temperature in a device that performs defrosting to remove frost on a cooler by performing temperature control so that the temperature detected by the temperature detection means matches the target temperature set by the temperature setting means. is greater than or equal to a predetermined value, when the cumulative cooling operation time reaches the preset defrost time interval, a coefficient determined according to the operating rate of the cooling operation so far is applied to the defrost time interval. The multiplied value is regarded as the defrost time interval and a defrost signal is output at this time interval, and if the management target temperature falls below a preset value, the previous defrost signal is output at the preset defrost time interval. A defrosting control device characterized in that a defrosting signal is output when an elapsed time from an end point is reached. 2 If the control target temperature is above a predetermined value, when the cumulative cooling operation time reaches the preset defrosting time interval, the operating rate of the cooling operation up to now is divided into at least two or more groups, and the operation rate is divided into two or more. The value obtained by multiplying the defrosting time interval by a correspondingly determined coefficient is regarded as the defrosting time interval, and defrosting is performed, or the elapsed time from the end of the previous defrosting exceeds a certain determined value. The defrosting control device according to claim 1, is configured to output a defrosting signal to perform defrosting at a predetermined time interval if the defrosting is performed at a predetermined time interval. 3 If the management target temperature is higher than a predetermined value, when the cumulative time of cooling operation reaches the defrosting time interval determined by the management target temperature, the coefficient determined according to the operating rate of cooling operation up to that point is Defrost is performed by considering the value multiplied by the frost time interval as the defrost time interval, or defrost is performed at this time interval when the elapsed time from the end of the previous defrost exceeds a certain value. A defrosting control device according to claim 1, which outputs a defrosting signal to perform defrosting. 4 If the control target temperature is higher than the predetermined value, the cumulative cooling operation time reaches the defrosting time interval determined by the control target temperature, or the elapsed time from the end of the previous defrosting is determined. The defrosting control device according to claim 1, which outputs a defrosting signal when the defrosting value is reached.