JPH02303543A - Method for controlling operation of low-temperature thermostatic chamber - Google Patents

Abstract

PURPOSE:To allow the automatic and sure execution of the defrosting of a cooler by detecting the time from the start of the operation of a refrigerator until a heater starts operating and controlling the defrosting operation of the refrigerator according to the change in the abovementioned time. CONSTITUTION:The temp. in a housing 1a is controlled by the refrigerator 7 and a heater 8. The time from the start of the operation of the refrigerator 7 until the heater 8 starts operating is detected and the defrosting operation of the refrigerator 7 is controlled according to the change in this time. As a result, the defrosting of the cooler is surely executed and the cooling capacity of the cooler is sufficiently exhibited.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for controlling the operation of a low-temperature thermostat, and more specifically, to an operation control method that can efficiently and reliably remove frost adhering to the cooler of a refrigerator. Regarding the method.

[Conventional technology]

Traditionally, in low-temperature thermostats, a refrigerator cooler and a heater are installed inside the refrigerator, and the operation time of the refrigerator and the heater are controlled to maintain the interior at a predetermined temperature. I have to. The method of controlling the operating time of the refrigerator and heater is to operate only the refrigerator when the temperature inside the refrigerator is higher than a certain set temperature, and to operate only the heater when the temperature inside the refrigerator is lower than that. One method is to keep the temperature at the set temperature, and the other is to keep the temperature inside the refrigerator at the set temperature by operating the refrigerator at predetermined intervals and the heater at the same time in the entire temperature range, and controlling the operating time of both. ing.

[Problem to be solved by the invention]

In the former method, if the set temperature is higher than 0°C, almost no frost will form on the cooler, but if the set temperature is negative, frost will form on the cooler and its cooling capacity will gradually decrease. is decreasing.

Furthermore, this method has the disadvantage that the temperature control accuracy is inferior to the latter method because the refrigerator and heater are operated alternately.

On the other hand, in the latter method, the temperature is controlled by operating the refrigerator and heater at the same time, so the temperature control accuracy is excellent, but the refrigerator still operates even when the internal temperature is lower than the set temperature. As a result, frost builds up on the cooler, reducing the cooling capacity of the refrigerator.

Therefore, in either method, it is necessary to defrost the cooler at appropriate intervals to restore the cooling capacity of the cooler.

Therefore, an object of the present invention is to provide a temperature control method for a low-temperature constant temperature bath that can defrost the cooler automatically and reliably.

[Means to solve the problem]

In order to achieve the above object, the temperature control method for a low-temperature constant temperature oven of the present invention is an operation control method for a low-temperature constant temperature oven that controls the internal temperature using a refrigerator and a heater. The present invention is characterized in that the time until the heater starts operating is detected, and the defrosting operation of the refrigerator is controlled according to the change in the time.

[Function] As described above, by detecting the activation start time of the heater, it is possible to know a decrease in the operating capacity of the cooler, and it is possible to control the timing of the defrosting operation and the duration of the defrosting operation.

〔Example〕

Hereinafter, the present invention will be explained in more detail based on one embodiment shown in the drawings.

First, as shown in Fig. 2, a compressor 2
, condenser 3. Throttle valve 4. Cooler 5 and valve 6 for defrosting operation
A refrigerator 7 and a heater 8 are provided.

The refrigerator 7 compresses, condenses, and expands refrigerant to cool the cooler 5 and lower the temperature in the refrigerator interior 1a, like a known refrigerator, and the heater 8 cools the refrigerator interior 1a by energizing or the like. It is used to heat the

Although the temperature control of the low-temperature constant temperature chamber 1 having such a configuration can be performed by any of the methods described above, an example in which the latter method is adopted will be described here.

That is, as shown in FIG. 1, the refrigerator 7 is activated (ON) at predetermined intervals to cool the inside of the refrigerator, and the temperature inside the refrigerator is detected by a known temperature sensor or the like, and the temperature inside the refrigerator is lower than the set temperature. When the temperature drops, the heater 8 is activated (ON) to maintain the internal temperature at the set temperature.

Here, the operation time of the refrigerator 7 is tx, the time from the start of operation of the refrigerator 7 to the start of operation of the heater 8 is ty,
If the time of defrosting operation is tz, there is almost no frost on the cooler 5, for example, immediately after the start of operation of the low-temperature constant temperature bath 1, t.
In xl, the operation start time tyt of the heater 8 is
It shows a substantially constant value depending on the configuration of the low-temperature constant temperature bath 1, the capacity of the refrigerator 7, the set temperature, etc.

When the frost attached to the cooler 5 naturally melts when the refrigerator 7 stops operating, or when the operating conditions are such that almost no frost formation occurs, the operation start time ty of the heater 8 is set at the initial stage. This value is approximately the same as the time tyt, and it can be seen that there is no need to perform defrosting operation in such a case.

On the other hand, when frost forms on the cooler 5, the cooling capacity of the cooler 5 gradually decreases, and the degree of decrease in the temperature inside the refrigerator decreases. The time at tyt becomes longer than the initial time tyt. That is, if the cooler 5 cannot be completely defrosted when the refrigerator 7 stops operating, the operation start time ty of the heater 8 gradually becomes longer as the capacity of the cooler 5 decreases, and the heater 8 operation interval becomes shorter than the initial period. It will be longer than .

Therefore, the operation time and stop time of the refrigerator 7, and the time from the start of operation of the refrigerator 7 to the first operation of the heater 8, that is, the time from the start of operation of the refrigerator 7 until the heater 8 starts operation. By detecting this, it is possible to know the change in the cooling capacity of the cooler 5, that is, the state of frost on the cooler 5.

Therefore, by detecting the operating time of both and controlling the defrosting operation of the refrigerator 7 according to the operating time of the heater 8 with respect to the operating time of the refrigerator 7, defrosting of the cooler 5 can be reliably performed. becomes possible. For example, by setting the operating time tx of the refrigerator 7, the operating start time ty of the heater 8, and the defrosting operation time tz for a certain set temperature using a predetermined calculation formula, the first As shown in the figure, refrigerator 7
The operation start time of the heater is t with respect to the operation time tXl of
In the case of yi, the time of the defrosting operation is set as tZl, and when the operation start time of the heater 8 with respect to the operating time of the refrigerator 7 is tx2 is ty2, the time of the defrosting operation is set as tx2.
Defrosting operation of the refrigerator 7 can be performed according to changes in the operation interval of the heater 8.

In addition, if the operation start time ty of the heater 8 becomes long and complete defrosting cannot be achieved by introducing hot gas only when the refrigerator 7 is stopped, the operation of the heater 8 will start for the operation time txn of the refrigerator 7. The defrosting operation time is set to tzn according to the time tyn, and the valve 6 is closed before the operation of the refrigerator 7 is stopped.
It can also be set to open and start introducing hot gas to the cooler 5 to perform defrosting operation.

Therefore, even if the amount of frost on the cooler 5 changes greatly depending on the set temperature, internal atmosphere, etc., defrosting operation can be performed at a reliable timing and time, and the cooling capacity of the cooler 5 can be fully utilized. can be done.

In addition, even in the above-mentioned temperature control method of operating the refrigerator and heater alternately, the operating time of the refrigerator becomes longer as frost forms on the cooler, and the ratio of the operating time of the refrigerator to the operating time of the heater increases. Since the temperature changes, it is possible to control the defrosting operation based on this change.

〔Effect of the invention〕

As explained above, the temperature control method for a low-temperature constant temperature bath according to the present invention controls the defrosting operation of the refrigerator according to changes in the operation start time of the heater, so that the defrosting of the cooler can be reliably performed. The cooling capacity of the cooler can be fully utilized. Therefore, it is possible to prevent a decrease in temperature control accuracy due to frost formation on the cooler, and it is not only possible to perform reliable temperature control over the entire temperature range, but also to eliminate unnecessary operation of the refrigerator due to a decrease in cooling capacity. It is also possible to reduce operating costs and extend the life of the device.

[Brief explanation of drawings]

FIG. 1 is a timing diagram showing an embodiment of temperature control of a low-temperature constant temperature bath according to the present invention, and FIG. 2 is a circuit diagram of the low-temperature constant temperature bath. 1... Low-temperature constant temperature bath 5... Cooler 7... Freezer 8... Heater tx... Operating time of refrigerator ty... Start time of heater operation 12... Defrosting operating time

Claims (1)

[Claims] 1. In a method for controlling the operation of a low-temperature thermostat that controls the internal temperature using a refrigerator and a heater, detecting the time from the start of operation of the refrigerator to the start of operation of the heater, and detecting the time from the start of operation of the refrigerator to the start of operation of the heater, 1. A method for controlling the operation of a low-temperature constant temperature bath, the method comprising controlling the defrosting operation of a refrigerator according to the conditions.