JPS6024386B2 - 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.

Defrosting of the coolers of subordinate refrigeration equipment was performed at regular intervals using a timer device.

The defrosting time interval using this method is generally determined based on the operating conditions that produce the most frost, so it is not suitable for cooling equipment for frozen foods with low control target temperatures, such as ice cream, which frosts very quickly and in large amounts. This is meaningful because it is necessary to defrost reliably, but in open showcases for meat, fresh fish, dairy products, fruits and vegetables, etc., where the target temperature is higher, frost formation is much less than this and defrosting is required. Defrosting is performed even when frost is not necessary, which is often inconvenient from the viewpoint 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 when the cumulative operating time of the refrigerator reaches a predetermined value. There is a method of starting defrosting at this point.

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 integrator. It has its drawbacks. That is, when the refrigerator starts intermittent operation, when the refrigerator stops, the fog layer on the heat transfer surface of the cooler naturally partially melts, the density of the fog increases, and the thickness of the frost layer becomes thicker.

Furthermore, if the operating rate of the refrigerator becomes smaller or 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 frost formation depending on the operation rate, the integration time must be set assuming the worst case of continuous operation.

Therefore, in practical operation, the defrosting frequency becomes higher than necessary. For example, open showcases installed in supermarkets have large openings, so the outside air load is extremely large. The inlet air temperature of the cooler installed in the air passage of the 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 chambers 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 that this method is very effective as a defrosting method.

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. This defrosting system has the function of changing the operating rate (hereinafter referred to as the operation rate) to obtain the optimal defrosting start time, as well as defrosting and canceling defrosting whenever necessary, and performs optimal defrosting that is safe, reliable, and leads to energy savings. The purpose is to provide a control device.

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 machine axis is the elapsed time after defrosting is completed, and the vertical axis is the operating rate. A and B use the difference in the air condition 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 of the dependent example reaches the set defrost interval.For example, when the operation rate is 50%, the operation rate is twice the defrost interval during continuous operation and the operation rate is 40%. So 2
．． It shows that it will be 5 times more. Defrost interval 1,
This relationship can be expressed as a hyperbola of 1=L/(SI of OS), where lo is the defrosting interval during continuous operation of the operating rate. 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 consideration. This figure shows an example in which when the operating rate reaches 50%, the defrosting interval becomes 3.3 sounds during 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. 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 that is a load, 2 is a refrigerator that is a cooling heat source, 3 is a refrigerant flow separation, 4 is a cold cutoff valve arranged in the cold soot flow path 3, 5 is a solvent expansion valve, and 6 is an open show. A cooler disposed in the air passage of the case 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 a defrosting means for melting the frost on the cooler 5; It is a frost control device.

Next, the operation will be explained. The cold soot 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, and evaporates in the cooler 6. It is cooled, becomes low-pressure refrigerant gas, and flows back 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 open showcases to be connected to one refrigerator. The temperature detector 8 detects the temperature inside the shield of 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.
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 an embodiment of the defrosting control device 9. As shown in FIG. In the figure, 9a is a temperature control device;
9b is a defrosting interval control circuit, and 11 is an internal temperature signal input line to which a signal from the temperature sensor 8 shown in 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 19 (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 which integrates the operating time since the end of the previous defrosting, that is, integrates the time of the temperature control signal 19 passing through the shutoff 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 rotation is to be performed.

Reference numeral 16 denotes a defrosting interval determining circuit, which receives the operating rate calculation result output of the operating rate calculation circuit 15, the setting value output of the defrosting interval setting device 17, and the operating time integrated value output of the first timer circuit 13. shall be.

First, it is determined whether the cumulative value of operating time has reached the defrost interval setting value. If this is not achieved, defrosting is not started and temperature control operation continues. 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 17 is 1q 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, it goes without saying that even when the operating rate is 60% or less, the defrosting interval extension coefficient can be defined and the above operation can be performed. As mentioned above, the relationship between the operating rate and the defrost interval extension coefficient differs for each oven showcase, so it is necessary to collect data 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 closed and the temperature control signal 19 is closed.

Reference numeral 22 denotes a forced defrosting start switch, and when this switch 22 is operated, the defrosting interval determining circuit 16 outputs a signal for forcibly defrosting.

In addition, this operation causes the 3-minute timer circuit 24 to start operating, and when 3 minutes have elapsed, it outputs the defrost end signal 25, which is input to the defrost interval determining circuit 16 via the OR gate circuit 26 to force the defrost. Finish the frost. Reference numeral 23 denotes a forced defrosting stop switch, and the operation of this switch 23 is input to the defrosting interval determining circuit 16 via an OR gate circuit 26, and the forced defrosting is ended in the same manner as described above.

The operation of this embodiment is as described above, but in another embodiment, the signal 27 is generated by operating the forced defrosting start switch 22.
(indicated by a broken line) to the first timer circuit 13 and the second timer circuit 14 to reset the cumulative value of operating time and the value of the elapsed time from the end of the previous defrosting to the present time. The initial synchronization of the defrost interval can be performed.

Still another embodiment is shown in FIG.

In the figure, the same numbers as in FIG. 4 indicate the same parts. In this figure, 28 is a regular defrosting temperature setting device, and temperature setting device 21
A comparison circuit 29 compares the set value with the set value of , and if the former exceeds the latter, a signal is output to perform defrosting at fixed time intervals regardless of the cumulative value of operating time or the operating rate. As a result, the operating rate calculation circuit 15 outputs a data signal indicating that the operating rate is 100%, and the gate circuit 30' and gate 30b are opened, and the elapsed time data of the timer circuit 14 is transmitted to the defrosting interval determining circuit. 16. Therefore, the defrosting interval determining circuit 16 performs defrosting at regular intervals. Therefore, by operating the forced defrosting start switch 22, the start of this scheduled defrosting can be synchronized, and from this point on, defrosting can be performed at regular intervals. Now, if the former is equal to the latter, the operating rate calculation circuit 15 performs a predetermined calculation and outputs the result.
Further, the gate circuit 30 outputs the cumulative operating time value of the timer circuit 13 through the gate 30a, and inputs the value to the defrosting interval determining circuit 16. The operation in this case is similar to that described in the first embodiment. The embodiment shown in Fig. 5 attempts to forcibly perform scheduled defrosting when the management target temperature is lower than a certain temperature. This is because the intention is to defrost the store after the store is closed and not defrost it while the store is open for product quality control purposes, and in this case, it is desirable to defrost at regular intervals.

In another embodiment, the defrosting interval is set by a setting device, but since this defrosting interval is almost determined by the management target temperature, the defrosting interval is determined by the set temperature of the temperature setting device 21. You can also.

For example, there is a management target temperature suitable for fresh meat and fish, and the defrosting interval applicable to this temperature range is also generally known, so there is no problem in determining the defrosting interval based on the management target temperature. In other words, the defrost interval setting device 1
This can be easily achieved by removing 7 and inputting the output of the temperature setting device 21 to the defrosting interval determining circuit 16 instead.
The configuration can also be made simpler.

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 the drawing]

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, and Fig. 5 shows the configuration of the defrosting control device. FIG. 3 is a block diagram showing the configuration of another embodiment. In the figure, 4 is the end valve, 7 is the defrosting means, 8 is the temperature detector, 9a is the temperature control device, 9b is the defrosting interval control circuit, 22 is the forced defrosting start switch, and 23 is the forced defrosting end. Switch 24 is a 30 minute timer circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts. Figure 1 Figure 2 Figure 4 Jobs in Figure 5

Claims (1)

[Scope of Claims] 1. In a device that performs defrosting to remove frost on a cooler by performing temperature control so that the temperature detected by the temperature detecting means matches the target temperature set by the temperature setting means, the cooling operation is performed. When the cumulative time reaches a preset defrosting time interval, the value obtained by multiplying the defrosting time interval by a coefficient determined according to the operating rate of the cooling operation up to now is regarded as the defrosting time interval. A defrosting control device characterized by outputting a defrosting signal at time intervals of a lever or by operating a defrosting start switch. 2. The defrosting control according to claim 1, wherein the coefficient determined according to the operating rate is divided into at least two or more operating rates, and each coefficient is determined according to the classification. Device. 3. The preset defrosting time interval is configured such that the value is stored in advance in the defrosting time interval determining means for each of at least two or more temperature categories according to the set value of the management target temperature. A defrosting control device according to any one of claims 1 to 2, characterized in that: 4 If the management target temperature is higher than a predetermined value, when the cumulative cooling operation time reaches the preset defrosting time interval, the coefficient determined according to the operating rate of the cooling operation up to that point is applied to the defrosting operation. Defrosting is performed by regarding the value multiplied by the time interval as the defrosting time interval, and if it exceeds the predetermined value, a defrosting signal is output to perform defrosting at the predetermined time interval. 4. The defrosting control device according to claim 3, wherein the time point at which the start switch is operated is the start time point of the defrosting time interval.