JPS6015860B2 - Defrost control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a defrosting device for freezing and refrigeration equipment, and more specifically, it detects the appropriate defrosting time for freezing and refrigeration equipment by a simple method,
Furthermore, the present invention relates to a defrosting control device for efficient defrosting which can optionally be performed by timer means.

Conventionally, the time to defrost a cooler of a freezing or refrigeration device has been determined by a timer device based on a predetermined cumulative time since the end of the previous defrost.

Since the predetermined cumulative time using this method is generally determined based on the operating conditions that cause the most frost on the food, defrosting is performed even when there is little frost formation and defrosting is unnecessary, which is a problem in terms of product temperature control and energy saving. There were many inconveniences from this point of view. 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 opening time of the internal temperature regulator, 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 it is simple and ingenious, as 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 decreases. Furthermore, if the operating rate of the refrigerator becomes smaller and the stop time becomes longer relative to the operating time, the frost layer may hardly grow. Considering such a case, the integrated time set for the defrosting control device based on the operating time integration in the conventional example is based on the case of continuous operation of the refrigerator, and is designed assuming the worst case of 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 etc. have a large opening.
The outside air load is extremely large. Therefore, when the refrigerator is stopped or the flow of hot 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 immediately rises, and the cooler The frost on top will melt quickly. If the conventional system is implemented in such a cooling system, the defrosting frequency will be completely higher than necessary. In other words, the conventional defrosting control device based on operation time integration is applicable to household refrigerators and other devices that have a closed cooled compartment, in other words, the inlet air temperature of the cooler does not rise much even when the cooling operation is stopped. is effective, but it is not very suitable for cooling systems where the inlet air temperature of the cooler rises quickly when the cooling operation is stopped, such as an open showcase, as the defrosting frequency becomes higher than necessary. I can say that.
The present invention has been made to improve the drawbacks of the conventional examples described above, and the set value of the cumulative closing time of the temperature regulator at the time of starting defrosting is changed depending on the ratio of closing and opening of the temperature regulator, The purpose is to obtain the optimal defrosting start time, and it can be used selectively in combination with conventional timer means.

Furthermore, it is possible to output a defrosting end signal preferentially in synchronization with an external controller if necessary. In order to clarify the advantages of the present invention, the algorithm for setting the defrosting start time will be described in detail below.

FIG. 2 was obtained through an experiment and is an operational characteristic diagram of an open showcase cooling system for explaining the algorithm of the defrosting method of the present invention.

In Figure 2, the machine axis is the elapsed time after the end of defrosting, the vertical axis is the operating rate, the parameters A and B are when the air conditions around the open showcase are different, and A is compared to B. This is the case when the enthalpy of the surrounding 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.

Furthermore, in case A, the operating rate increases as time passes and finally becomes continuous operation, and in this case it can be seen that the characteristics of the cooler have deteriorated due to cooling. 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 a diagram showing what kind of defrosting interval is suitable for the operating rate based on an experiment like the one shown in FIG. 2.

Characteristic curve A is a conventional example in which defrosting is performed when the cumulative operating time reaches the set defrost interval.For example, at an operating rate of 50%, it is twice the defrosting interval during continuous operation, and the operating rate is 40%. So 2. If the defrost interval is 1, the operating rate is LO, 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 carrying out a number of experiments such as those shown in FIG. 2, and is specific to a particular showcase and its cooling system. The present invention is intended to determine in advance an appropriate defrost interval for the above-mentioned operating rate, and thereby determine when to start defrosting the cooler.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram showing an embodiment in which a defrosting control device according to the defrosting control method of the present invention is applied to a cooling system for an oven showcase.

1 is an open showcase as a load, 2 is a refrigerator as a cooling heat source, 3 is a soot flow path, 4 is a refrigerant valve disposed in the refrigerant flow path 3, 5 is an expansion valve for a lining medium, 6 is a cooler installed in the air passage of the open showcase 1, 7 is a cooler 6
8 is a temperature detector for detecting the temperature inside the open showcase, and 9 is a controller.

Also, a temperature detector is attached to the cooler 6 to output the temperature of the cooler to the defrosting end detector 11. The operation of the open showcase cooling system configured as above will be explained below.

The high-pressure liner liquid produced by the cooler 2 passes through the refrigerant flow path 3, and if the shroud valve 4 is open, it is depressurized by the expansion valve 5 and evaporated in the cooler 6, and then flows through the air path in the open showcase 1. The air passing through is cooled, becomes low-pressure soot gas, and returns to the refrigerator 2. 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 dotted line in FIG. The temperature detector 8 detects the temperature inside the open showcase 1, and the controller 9 receives a signal from the detector,
The temperature inside the open showcase 1 is adjusted by opening and closing the shutter valve 4.

The controller 9 also integrates the opening times of the shutters and valves and calculates the cooling operation ratio (hereinafter simply referred to as operation ratio) of the open showcase 1. The time to start defrosting is determined as follows. First, the setting 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. Further, the controller 9 includes a timer means, and when the timer means is selected, a defrosting signal is outputted from the controller 9 to the defrosting means 7 when a predetermined time inputted in advance is reached. The operation of the controller 9 will be explained in detail below.

FIG. 4 is a block diagram showing a detailed circuit of the controller 9 of FIG. 1.

In this figure, reference numeral 20 indicates an internal temperature signal that is input to the temperature control circuit 21, and a temperature setting input 22 by external or human operation is transmitted via a gate 23 to an ON signal 24 (in FIG. 1) for the cooling means. Opening of the opening valve 4) is output. 25
is a timer circuit that integrates the output time of the ON signal from the temperature control circuit 21.

26 is a timer circuit that outputs the elapsed time since the end of the previous defrosting.

Reference numeral 35 denotes an operation rate calculation circuit which calculates the operation rate based on the output of the cumulative ON time of the timer circuit 25 and the output of the elapsed time of the timer circuit 26.

A defrosting interval setting circuit 27 receives an initial defrosting interval setting input 28 from the outside and initializes the defrosting interval.

Further, the operating rate calculation circuit 35 determines and outputs a preset amount of the defrosting interval according to the operating rate to the defrosting interval setting circuit 27. Thereby, the preset amount of the defrost interval changes dynamically depending on the operating rate. This part is a characteristic operation of the present invention. The timer circuit 25 also outputs the on-time integrated value to the defrosting interval setting circuit 27. Defrost interval setting circuit 27
outputs the defrosting signal 29 (to the defrosting means 7 in FIG. 1) when the on-time integrated value by the defrosting interval setting circuit 27 reaches the defrosting interval set by the operation rate calculation circuit 26. . At this time, the defrosting signal 9 is also input to the gate 23, and the output of the on signal 24 is stopped. Similarly, when the defrosting signal 29 is artificially outputted only by the timer means, by inputting the artificially operated switching signal 30 to the timer circuit 26,
Only the timer circuit 26 is input to the defrost interval setting circuit 27, and the output of the timer circuit 25 and the output of the operating rate calculation circuit 35 are not input to the defrost interval setting circuit 26. As a result, the defrost signal 29 is output when the defrost interval reaches the initial preset value. At this time, the defrosting signal 29 is also input to the gate 23, and the output of the on signal 24 is stopped. Further, 31 is a defrost end detector for outputting a defrost end signal to the defrost end device 33 when the cooler temperature signal 32 reaches the defrost end temperature.

Further, if necessary, a defrost end signal 34 from an external controller is input to the defrost end device 33, and a defrost end signal is output from the defrost end device 33 in synchronization with this. The defrosting end signal is also input to the gate 23, and the output stop of the on signal 24 is canceled. Also, the defrosting termination device 3
3 is configured to end defrosting even when the internal temperature signal 20 reaches a predetermined temperature or higher. However, in this case, in a normal operating state, the defrost detector is configured to detect the end of defrosting first. With the configuration as described above, the defrosting frequency is not more than necessary as in the conventional case, and an optimum defrosting interval can be obtained.

Next, a specific example of a defrosting interval determining method will be described. When the operation rate calculation circuit 35 changes the preset amount of the defrost interval, first, the defrost interval initially set from the outside in the defrost interval setting circuit 27 is set as the defrost interval during continuous operation, for example.
The initial setting amount is stored in the defrosting interval setting circuit 27. The operation rate calculation circuit 35 outputs a change signal for the preset amount of the defrost interval to the defrost interval setting circuit 27 according to the operation rate. Set the initial setting value to be a coefficient corresponding to the operating rate. The coefficient may be determined according to 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 %>operating rate>80% is the same coefficient, and 80≧operating rate>70% is another coefficient) It may be a coefficient that changes stepwise. When the preset amount is changed in this way 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 cooler, but as mentioned above,
The ratio of the appropriate defrosting interval corresponding to the operation rate to the defrosting interval during continuous operation, that is, the coefficient corresponding to the operation, does not differ greatly even in open showcases with different internal temperature ranges. In other words, the defrost interval setting circuit 2 is initially
If only the initial setting value of the defrost interval (defrost interval during continuous operation) set in 7 is set to the value of the open showcase to be controlled, the controller 9 will be able to control the open showcase in various temperature ranges inside the refrigerator. It can be used in all cases. Taking the idea further, the controller shown in FIG. 4 has a temperature adjustment circuit 21 that controls the temperature inside the refrigerator, and this temperature adjustment circuit 21 has a setting input 22 for the temperature inside the refrigerator of the open showcase. Since the input 22 is given, the initial defrost interval can be set from the temperature regulation circuit 21 to the defrost interval setting circuit 27. This is because, as mentioned above, the defrosting interval during continuous operation is determined depending on the temperature range inside the cold storage refrigerator. With this configuration, by simply setting the temperature, the optimal defrost interval will be automatically selected for open showcases in any temperature range, allowing for easy and efficient defrosting. .

In addition, if it is necessary to defrost using a conventional timer due to the frosted state of the showcase, the timer means included in the controller 9 can be artificially switched and used.
Users will be able to use it in a wider variety of ways.

In the case of the above embodiment, an efficient defrosting cycle can be obtained without requiring any new detection means, and the controller 9 in FIG.
If it is realized by electronic circuit means or the like, there will be no problems in cost, reliability, etc. when implementing the present invention.

Furthermore, according to this embodiment, even if the amount of mist 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. In addition, even if the defrost end signal detector does not output a defrost end signal for some reason, defrosting is ended by the temperature detector inside the dust or by a signal from an external controller, making the defrost control device more reliable. can be obtained. As described above, according to the present invention, it is possible to always select an efficient defrosting start time, and there are effects such as power saving and prevention of temperature rise inside the refrigerator.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of the defrosting control device according to the present invention applied to a cooling system for an open showcase, and FIG. 2 is a diagram of the cooling system for an open showcase for explaining the present invention. The operating characteristic diagram, Figure 3 is an explanatory diagram showing the appropriate defrosting interval for the operating rate in the open showcase cooling system, and Figure 4 is the
FIG. 2 is a circuit block diagram showing details of the control device shown in the figure. In the figure, 7 is a defrosting device, 8 is a temperature detector, 9 is a controller, 10 is a temperature detector, 21 is a temperature adjustment circuit, 23 is a gate, 25 is an on-time integration timer, 26 is an elapsed time integration timer, 27 is a defrosting interval setting circuit.
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)

[Claims] 1. A temperature control device that controls the cooling means on and off so as to maintain the room temperature to be cooled within a set temperature range, and an operation that calculates the operating rate of the cooling means and sets the defrosting operation time interval according to the operating rate. A rate calculation circuit, a defrosting device for removing frost attached to the cooling means, and an elapsed time since the previous defrosting.
a first defrosting control means that causes the defrosting device to perform a defrosting operation when an operation time interval set by the operation rate calculation circuit is reached; A second defrosting control means for operating the defrosting device when the cumulative time reaches a preset cumulative time, and a means for selecting either one of the first or second defrosting control means. A defrosting control device characterized by: