JPS6024387B2 - Defrost control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a defrosting device for refrigeration equipment such as an open showcase, and particularly to a device for efficient defrosting.

Conventionally, the defrosting of the cooler of a freezing/refrigerating device has been carried out using a timer device at predetermined cumulative time intervals from the end of the previous defrosting.

Since the predetermined cumulative time interval using this method is generally determined based on the operating conditions with the highest amount of frost formation, defrosting is performed even when there is little frost formation and defrosting is unnecessary, resulting in problems in overflow management and There were many inconveniences from the Tsurumi point of view of energy conservation. In recent years, this method has been improved and is now widely used in household refrigerators, etc., by integrating the cumulative operating time of the refrigerator, that is, the closing time of the internal temperature controller, and when it reaches a predetermined value. There is a defrost control method that starts defrosting.

This method has an automatic function that allows the defrost interval to be matched to the load of the cooler, that is, when the load is low, the defrost interval is longer, and when the load is high, the defrost interval is shortened. Although the device is simple and ingenious in that the only accessory device is a time integrator, it has the following 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 becomes thinner. Furthermore, if the operation rate of the refrigerator becomes lower and the stop time becomes longer relative to the operation time, the frost layer may hardly grow. When considering such a case, the setting cumulative time of the defrosting control device based on the cumulative operation time of the conventional example is based on the case of continuous operation of one refrigerator, and the design is performed assuming the worst case in use. As a result, it can be seen that the defrosting frequency becomes higher than necessary in practical operation including actual intermittent operation. In particular, open showcases installed in supermarkets and the like have large closed parts and have a very large outside air load.

Therefore, when the refrigerator is stopped or the flow of soot in the cooler is stopped by the temperature controller, the inlet air temperature of the cooler installed in the air path of the open showcase rises immediately, and the cooler The frost on top will melt quickly. In such a cooling system, if the system of the above-mentioned subsidiary example is implemented, the defrosting frequency will be completely more than necessary. In other words, the defrosting control device based on operation time integration in the above-mentioned example is one that has a closed cooled storage such as a household refrigerator, or in other words, the inlet air temperature of the cooler does not rise much even when the cooling operation is stopped. However, in cooling systems where the inlet air temperature of the cooler rises quickly while cooling operation is stopped, such as an open showcase, defrosting becomes more frequent than necessary. It can be said that it is not very suitable. In addition, in the above-mentioned example, if the power source of the control device is cut off due to a power outage, etc., the accumulated operating time up to that point will be reset, and after the power is restored, the accumulated operating time will start anew. Even when defrosting is required, a defrosting start signal is not output, causing problems such as defrosting failure. The present invention has been made in order to improve the drawbacks of the above-mentioned conventional examples, and the time interval for defrosting (hereinafter referred to as the defrost interval) is changed to the time period during which the cooler is performing cooling operation, that is, The defrost control device is designed to change the cooling operation rate (hereinafter referred to as the operation rate) to obtain the optimal defrost start time, and to continue operating without any inconvenience after the power is restored, even if the control device's power is cut off. This is what we are trying to provide.

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

FIG. 2 is an operational characteristic diagram of an open showcase cooling system obtained through experiments and used to explain the algorithm of the defrosting method of the present invention.

In Fig. 2, Fujiki is the elapsed time after the end of defrosting, the vertical axis is the operating rate, and the parameters A and B are when the air conditions around the open showcase are different. This is the case when the enthalpy of air is high.

From FIG. 2, it can be seen that in case B, the operating rate is constant with respect to the elapsed time, and from this it can be seen that the characteristics of the cooler do not deteriorate due to frost formation.

In case A, the operation rate increases as time passes and finally becomes continuous operation, and in this case it is clear that the characteristics of the cooler have deteriorated due to frost formation. In this way, it has been found that there are regions where defrosting is virtually unnecessary depending on the operating rate, and conversely, if these characteristics are clarified, it will be possible to obtain accurate information on when to start defrosting based on the operating rate. It turns out that it is possible. FIG. 3 is an explanatory diagram of what kind of defrosting interval is suitable for the operating rate based on an experiment like the one shown in FIG. 2.

The characteristic curve A is for defrosting when the cumulative operating time reaches the set defrost interval.For example, at an operating rate of 50%, the operating rate is twice the defrosting interval during continuous operation, and the operating rate is 40%. %, it will be 2.3 sounds.If the defrost interval is 1, the operating rate is , and the defrost interval during continuous operation is lo, then 1=L/(=0 to 1)
That is. However, as mentioned above, in this case, the frequency of defrosting becomes higher than necessary. In the present invention, the defrosting interval is determined based on the operating rate as explained in FIG. 2, and an appropriate defrosting start time is selected.

B in FIG. 3 is an example of this, and shows the appropriate defrosting interval at each operating rate. Such a characteristic curve can be obtained by conducting many experiments as shown in Fig. 2, and is unique to a certain showcase and its cooling system. The frost interval is calculated in advance, and the time to start defrosting the cooler is determined based on the frost interval. The details of the present invention will be explained below according to the illustrated embodiments.

FIG. 1 shows -
FIG. 1 is an overall configuration diagram showing an example. In the figure, 1 is an open showcase that is a load, 2 is a refrigerator that is a cooling heat source,
3 is a refrigerant flow path, 4 is a refrigerant cutoff valve disposed in the cold soot flow path 3, 5 is a refrigerant expansion valve, and 6 is a cooler disposed in the air path of the open showcase 1. , 7 is a defrosting means for melting the frost on the cooler 6, 8 is a temperature detector for detecting the temperature inside the open showcase, and 9 is a controller. The operation of the open showcase configured as above will be explained below.

The high-pressure cold soot liquid produced by the refrigerator 2 passes through the cold soot flow path 3, and if the shroud valve 4 is open, it is evaporated in the cooler 6 where the pressure is reduced by the expansion valve 5, and the liquid is evaporated in the open showcase 1. The air passing through the air path is cooled and becomes low-pressure cold soot gas, which is then sent to refrigerator 2.
Reflux to. In FIG. 1, in order to think more generally, there is not a one-to-one correspondence between the refrigerator 2 and the open showcase 1, but instead there is a plurality of other open showcases (not shown) serving as loads on the refrigerator. 2 through a flow path indicated by a broken line in FIG. The temperature detector 8 detects the temperature inside the open showcase 1, and the controller 9 receives the signal from the detector 8, opens and closes the shutter valve 4, and adjusts the temperature inside the open showcase 1. conduct. The controller 9 also integrates the open time of the shutter valves 4 and calculates the cooling operation ratio (hereinafter simply referred to as the operation ratio) of the open showcase. The time to start defrosting is determined as follows. First, the set value for the cumulative opening time of the shingle valve 4 is determined based on the operating rate starting from the end of the previous defrosting operation, and when the cumulative opening time of the shingle valve 4 reaches the set value, the A frost signal is output from the controller 9 to the defrosting means 7. The operation of the controller 9 will be explained in detail below. FIG. 4 is a control circuit block diagram for explaining the operation of the controller 9 in FIG. 1.

In this figure, reference numeral 10 indicates an internal temperature signal that is input to the temperature control circuit 12, and a cooling means ON signal 19 (in FIG. and the opening/closing of valve 4). Reference numeral 13 denotes an on-time integration timer circuit that integrates the output time of the on-signal from the temperature control circuit 12.

14 is an elapsed time integration timer circuit which outputs the elapsed time since the end of the previous defrosting.

Reference numeral 15 denotes an operation rate calculation circuit which calculates the operation rate based on the output of the on-time cumulative time of the on-time cumulative timer circuit 13 and the elapsed time output of the elapsed time cumulative timer circuit 14.

A defrosting interval setting circuit 16 receives an initial defrosting interval setting input 17 from the outside and initializes the defrosting interval.

Further, the continuous rotation rate calculation circuit 15 determines and outputs a preset amount of the defrost interval according to the operating rate to the defrost interval setting circuit 16. As a result, the IJ set amount for the defrost interval changes dynamically depending on the operating rate. Further, the on-time integration timer circuit 13 also outputs the on-time integration value to the defrosting interval setting circuit 16. The defrosting interval setting circuit 16 is connected to the operation rate calculation circuit 1.
When the on-time integrated value by the defrost interval setting circuit 16 reaches the defrost interval preset by 5, the defrost signal 20 is output to the defrost means 7 shown in FIG. At this time, the defrosting output 20 is also input to the gate 18, and the output of the on signal 19 is stopped. Further, 21 is a timer for starting forced defrosting, which is configured to output a defrosting start signal after a predetermined period of time when the power is turned on. 9a is a temperature control device consisting of a temperature control circuit 12 and a gate 18;
b is a defrosting interval control circuit consisting of an on-time accumulating timer circuit 13, an elapsed time accumulating timer circuit 14, an operating rate calculating unit 15, and a defrosting interval setting circuit 16.

Next, a specific example of a defrosting interval determining method will be described. When the operation rate calculation circuit 15 changes the preset amount of the defrost interval, first, the defrost interval initially set from the outside in the defrost interval setting circuit 16 is set as, for example, the defrost interval during continuous operation,
The initial setting amount is stored in the defrosting interval setting circuit 16.

Depending on the operating rate, the operation rate calculation circuit 15 either outputs a change signal for the preset amount of the defrost interval to the defrost interval setting circuit 16, or uses the signal content as a coefficient to multiply the initial setting value, and the preset amount after the change is set to the initial value. Set the set value to be a coefficient corresponding to the operating rate. The coefficient may be determined based on the appropriate defrosting period as shown in Figure 3, and the value of the coefficient may be one that changes continuously depending on the operating rate, or it may be determined by dividing the operating rate to a certain extent (for example, 100
It may be a coefficient that changes stepwise (such as when %≧operating rate>80% is the same coefficient, and when 80≧operating rate 70% is another coefficient). Further, the operation setting time of the forced defrosting start timer 21 may be set so as to issue a defrosting start signal in a relatively short time in order to avoid defrosting failures. When the preset amount is changed as described above using a coefficient corresponding to the operating rate, there are the following advantages. First of all, in open showcases where defrosting control is to be performed, the absolute value of the appropriate defrost interval will naturally differ greatly depending on the temperature range inside the storage compartment, but as mentioned above, defrosting during continuous operation the ratio of the appropriate defrost interval corresponding to the operating rate to the interval;
In other words, the coefficients corresponding to the above-mentioned operations do not differ greatly even in open showcases with different internal temperature ranges. In other words, only the initial setting value of the defrost interval (defrost interval during continuous operation) that is initially set in the defrost interval setting circuit 16 by external input or human operation input is the value of the open showcase to be controlled. If set to , the controller can be used commonly for open showcases with various internal temperature ranges. Taking the idea further, the controller 9 in FIG. 4 has a temperature adjustment circuit 12 that controls the temperature inside the refrigerator, and this temperature adjustment circuit 12 is given a setting input 11 for the temperature inside the open showcase. Therefore, using the input 11, the temperature adjustment circuit 1
2 to the defrost interval setting circuit 16 to set an initial defrost interval. This is because, as mentioned above, the defrosting interval during continuous operation is determined depending on the temperature range within the storage compartment. With this configuration, by simply setting the temperature, the optimum defrosting interval will be automatically selected in any temperature range of the open showcase, and defrosting will be easily and efficiently performed.

In the case of the above embodiment, an efficient defrosting cycle can be obtained without requiring any new detection means, and if the controller 9 in FIG. 1 is realized by electronic circuit means or the like, the present invention can be carried out. There are no problems with cost or reliability.

Furthermore, according to this embodiment, even if the amount of frost increases rapidly for some reason and the cooling efficiency decreases, the operation rate increases accordingly, and the defrost interval is corrected to be shorter by the above-mentioned function. Therefore, no problems occur, it can cope with any load fluctuations, and efficient defrosting is always performed. Further, even if an abnormal situation such as a fin source cutoff of the controller occurs, defrosting is started in a relatively short time after recovery, so defrosting failures can be prevented. As described above, according to the present invention, an efficient defrosting start time can always be selected, and practical effects such as power saving and prevention of temperature rise inside the refrigerator can be obtained.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 shows the case where the defrosting control device based on the defrosting control method of the present invention is applied to the cooling system of an open showcase.
An overall configuration diagram showing an embodiment, FIG. 2 is an operating characteristic diagram of an open showcase cooling system to explain the defrosting method of the present invention, and FIG. FIG. 4 is an explanatory diagram showing the frost interval, and FIG. 4 is a control circuit block diagram for explaining the operation of the control device of FIG. 1. In the figure, 7 is a defrosting means, 8 is a temperature detector, 9a is a temperature control device, 9b is a defrost interval control device, 12
is the forced defrost start timer. Note that the same reference numerals in the figures indicate the same or corresponding parts. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. Defrosting means for a cooler that cools a room to be cooled, and temperature control that controls on/off the cooling operation of the cooler to maintain the temperature of the room to be cooled within a set temperature range. It stores the relationship between the cooling operation rate of the device and the cooler and a predetermined appropriate defrosting interval, calculates the cooling operation rate of the cooler since the end of the previous defrosting, and calculates the elapsed time since the end of defrosting. a defrosting interval control device that operates the defrosting means when the calculated cooling operation rate reaches the appropriate defrosting interval within the elapsed time, and when the power to each of the control devices is suddenly cut off. A defrosting control device comprising forced defrosting means that forcibly operates the defrosting means after a predetermined period of time has passed after recovery. 2. Claim 1 characterized in that the defrost interval control device is configured so that the appropriate defrost interval to be compared with the elapsed time is determined by multiplying the defrost interval during continuous operation by a predetermined coefficient. Defrosting device as described in section.