JPH0355758B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Industrial Application Field The present invention relates to a device for preventing condensation of food stored in a refrigerator, and particularly relates to a device for preventing condensation of food stored in a refrigerator, and particularly to a device for preventing condensation of food stored in a refrigerator. This invention relates to a food condensation prevention device that detects condensation and controls the power load of a refrigerator.

(b) Prior art When food, such as rice packed in a plastic bag, is stored in a refrigerator and stored at a predetermined temperature, such as 15°C, when it is taken out of the refrigerator, the temperature of the air inside and outside the refrigerator and the humidity of the outside air may cause the rice to There are times when the temperature of the plastic bag falls below the dew point temperature, and at this time dew forms on both the inner and outer surfaces of the plastic bag and on the surface of the rice grains. The surface of the rice gets wet due to dew generated on the inside of the plastic bag and on the surface of the rice, and if it is stored as is, the quality of the rice deteriorates extremely in a short period of time, especially during the rainy season when the outside air is humid. Mold grows on the surface of rice grains, resulting in a deterioration in the quality and taste of the rice grains.

(c) Object of the Invention The present invention provides a food condensation prevention device that allows the internal temperature of a refrigerator to be higher than the dew point temperature.

(D) Structure of the Invention The present invention provides a humidity sensor that senses the relative humidity of outside air and outputs a voltage between terminals according to the relative humidity, and an outside humidity sensor that senses outside air temperature and outputs a voltage between terminals that corresponds to the outside air temperature. a calculation unit that inputs the voltage between both terminals of the temperature sensor, the humidity sensor, and the outside temperature sensor, calculates and outputs a dew point temperature determined according to relative humidity and outside temperature from the deviation of both inputs, and stores the food; an internal temperature sensor that senses the internal temperature of the refrigerator and outputs a voltage between terminals according to the internal temperature; a cooling device that cools the refrigerator; and an output of the calculation section and between the terminals of the internal temperature sensor. When a voltage is input and the voltage across the terminals of the internal temperature sensor is greater than the output of the calculation section, the cooling device is driven, and when the voltage across the terminals of the internal temperature sensor is smaller than the output of the calculation section, the cooling device is stopped. and a cooling operation control section that controls the operation of the cooling device, and provides an apparatus for preventing condensation of food such that the internal temperature of the refrigerator is equal to or higher than the dew point temperature.

(E) Embodiment Hereinafter, an embodiment of the present invention will be described based on FIGS. 1 to 3. Figure 1 is an electrical circuit diagram of a food condensation prevention device. For example, the outside temperature is T ₁ ℃, the inside temperature of a refrigerator containing food such as rice packed in a plastic bag is T _{2 ℃, and the outside temperature is T 2} ℃. The temperature inside the warehouse is controlled so that the following formula (S) is satisfied, assuming the relative humidity is X%, and dew is automatically prevented from forming on the surface when the rice is taken out of the warehouse. In formula (S), 5 is a constant, and 100 represents that the amount of water vapor within a predetermined volume is equal to the saturated amount of water vapor in the same volume, meaning that the relative humidity is 100%.

T ₂ > T ₁ −100−X/5 ...(S) 1 is a transformer connected to AC power supply 2, 3, 4
are the first and second secondary windings. The second secondary winding 4 is connected to the input terminals a, b of the diode rectifier bridge 5.
connected to the output terminal c of the rectifying bridge 5,
d are connected to the first and second wirings 6 and 7, respectively. A smoothing capacitor 8 is connected between the first and second wirings 6 and 7. A is the first and second resistance
R ₁ , R ₂ and the first NPN transistor (hereinafter the first
The collector of the first transistor 9 is connected to the first wiring ₆ via the first resistor R1.
The base is connected to the second wiring 7 via the Zener diode 10, and the second resistor _R2 is connected between the base and collector. The emitter of the first transistor 9 is connected to the second wiring 7 through a series circuit of the third resistor _R3 and the outside temperature sensor 11, and the emitter of the first transistor
It is connected to an operational amplifier (hereinafter referred to as an amplifier) 12 and a second operational amplifier (hereinafter referred to as a comparator) 13 to supply power.

14 is a relative humidity-to-voltage converter (hereinafter referred to as a converter) to which AC power is supplied from the first secondary winding 3 of the transformer 1, and a humidity sensor 14' that senses the relative humidity of the outside air is connected to it. Outputs the terminal voltage V ₁ according to the relative humidity outside the refrigerator. (+) of converter 14A
The side output terminal 14C is connected to the fourth resistor _R4 and the fifth resistor _R5.
It is connected to the second wiring 7 via a voltage dividing resistor circuit. The middle point of the voltage dividing resistor circuit is the sixth resistor R ₆
The midpoint of the series circuit of the third resistor R ₃ and the outside temperature sensor 11 is connected to the (+) side input terminal of the amplifier 12 via the (-) side input terminal of the amplifier 12 . Furthermore, the output terminal 1 of the amplifier 12
A negative feedback resistor is connected between 2a and the (-) side input terminal.
R ₇ is connected and the output terminal is resistor R and output terminal 12
Diode that blocks current from flowing in the a direction
D' is connected to the (+) side input terminal of the comparator 13. Further, between the emitter of the first transistor 9 and the second wiring 7, there is an eighth resistor _R8 and an internal temperature sensor 16 for sensing the internal temperature of the refrigerator.
A series circuit is connected to the internal temperature sensor 16.
A variable resistor R' for finely adjusting the (-) side input voltage of the comparator 13 is connected in parallel with. The midpoint of this series circuit is connected to the (-) side input terminal of the comparator 13, and a positive feedback resistor _R9 is connected between the (+) side input terminal and the output terminal 13a. or,
The output terminal 13a is connected to the second wiring 7 via a series circuit of a tenth resistor _R10 and an eleventh resistor _R11 . In addition, a 12th resistor is connected between the first and second wirings 6 and 7.
A voltage dividing circuit consisting of a series connection of R ₁₂ and a 13th resistor R ₁₃ is connected, and the midpoint E of this voltage dividing circuit is connected to the comparator 1.
Since it is connected to the (+) side input terminal of comparator 13, the (+) side input voltage of comparator 13 is connected to the 12th and 13th resistor.
The voltage will not drop below the voltage divided by R ₁₂ and R ₁₃ .

18 is the second NPN provided as a switching element
type transistor (hereinafter referred to as a second transistor), the base is connected to the midpoint 19 of the series circuit, the emitter is connected to the second wiring 7, and the collector is connected to the excitation winding 20a of the relay 20 and the first wiring 6.
It is connected to the first wiring 6 through a parallel circuit with a diode D whose direction is positive. Also, 20s
is a load control switch that is turned on when the excitation winding 20a is energized and turned off when it is not energized;
0s controls the operation of the cooling device 21, which is composed of a compressor and the like that cools the refrigerator, and when the switch 20s is turned on, the cooling device 21 starts operating, and when the switch 20s is turned off, the operation is stopped. In addition, (+) (-) of the converter 14 to which the humidity sensor 14' is connected
As shown in FIG. 2, the voltage V ₁ between both terminals gradually increases as the relative humidity sensed by the humidity sensor 14 increases. Further, the voltages V ₂ and V ₃ between the terminals of the internal temperature sensor 16 and the outside temperature sensor 11 gradually decrease as the outside temperature rises, as shown in FIG.

Furthermore, the comparator 13, the second transistor 18, and the relay 20 constitute a cooling operation control section that controls the operation of the cooling device 21.

Hereinafter, the operation of the food condensation prevention device will be explained. For example, when the outside temperature is 25°C and the relative humidity is 70%, the voltage V ₁ between the terminals of the converter 14 is 7V, the voltage V ₃ between the terminals of the outside temperature sensor 11 is 4V, and the voltage V ₃ between the terminals of the amplifier 12 is ( −) side input voltage 3.75V, the output voltage V ₄ of the amplifier 12 is
It becomes 8.4V. At this time, the temperature inside the refrigerator is expressed in equation (S) as T ₁ = 25,
The value obtained by substituting X=70, that is, the dew point temperature
The temperature is controlled to be higher than 19℃. That is,
When the (+) side input voltage V ₅ of the comparator 13 is 4.4V, the internal temperature is lower than 19°C and the voltage V ₂ between the terminals of the internal temperature sensor 16 is 4.6, the (-) side input voltage of the comparator 13 is
The side input voltage is higher than the (+) side input voltage, the comparator 13 outputs a low level signal (hereinafter referred to as "L" signal), the second transistor 18 is turned off, and the excitation winding 20a of the relay 20 is turned off. It becomes energized. When the excitation winding 20a is de-energized, the load control switch 20s is turned off, the cooling operation is stopped, and the temperature inside the refrigerator gradually rises. As the internal temperature rises, the terminal voltage V ₂ decreases, and when the (+) side input voltage of the comparator 13 becomes higher than the (-) side input voltage, the comparator 1
3 is a high level signal (hereinafter referred to as "H" signal)
is output, the second transistor 18 is turned on, the excitation winding 20a is energized, the load control switch 20s is turned on, the cooling operation is restarted, and the temperature inside the refrigerator and the temperature of the rice gradually decrease. The temperature inside the refrigerator gradually decreases.
When the temperature drops below 19°C, the (+) side input voltage of the comparator 13 becomes lower than the (-) side input voltage, and the comparator 13 outputs an "L" signal and the cooling operation is stopped to reduce the temperature inside the refrigerator and the rice temperature. gradually increases. Similarly, the cooling operation is restarted and stopped repeatedly as the internal temperature rises and falls, and the rice temperature is controlled to be higher than 19℃, and the difference between the outside temperature and the internal temperature (rice grain temperature) is 6.
kept below ℃.

Also, when the outside temperature is 30°C and the relative humidity is 70%, the voltage V ₃ between the terminals of the outside temperature sensor 11 is equal to the outside temperature 25
℃, and the (+) side input voltage of the amplifier 12 decreases, so the output voltage V ₄ of the amplifier 12 becomes
The input voltage on the (+) side of the comparator 13 becomes lower than 4.4V. Therefore, the temperature inside the refrigerator is higher than the temperature before the outside temperature rises.In equation (S), T ₁ =
The temperature is controlled to be higher than 24°C, which is obtained by substituting 30. Also, the outside temperature is 22
℃, the voltage V ₃ between the terminals of the outside air temperature sensor 11 increases compared to when the outside air temperature is 25 ℃,
The output voltage V ₄ of the amplifier 12 rises above 8.4V, and the (+) side input voltage of the comparator 13 rises above 4.4V. Therefore, the temperature inside the refrigerator (rice grain temperature) is lower than the temperature before the temperature outside the refrigerator decreases. In equation (S), T ₁ = 22, X = 70
The difference between the outside air temperature and the rice grain temperature is kept below 6°C, the same as when the outside temperature is 30°C.

Next, when the outside temperature is 25℃ and the outside relative humidity is 90%,
The voltage V ₁ between the terminals of the converter 14 is 9V, the voltage V ₃ between the terminals of the outside temperature sensor 11, that is, the (+) side input voltage of the amplifier 12 is 4V, and the (-) side input voltage is
When it is 3.9V and the difference between both input voltages is small compared to when the relative humidity is 70%, the output voltage _V4 of the amplifier 12 is smaller compared to when the relative humidity is 70% and 6.3V, and it is less than the reference value. The comparator 13 outputs an "H" signal or an "L" signal by comparing the voltage 3.8V at the midpoint E and the voltage V ₂ between the terminals of the temperature sensor 16 in the refrigerator, and the temperature in the refrigerator (that is, the rice temperature) is T ₁ = 25 in equation (S),
The relative humidity is controlled to be higher than the 23℃ found by substituting X=90, and the difference between the outside temperature and the inside temperature is 70% relative humidity.
It is kept below 2°C, which is less than when Also, if the outside air temperature gradually increases while the relative humidity remains unchanged at 70%, the voltage between the terminals of the outside air temperature sensor 11 will increase.
V ₃ gradually decreases, the output voltage of amplifier 12 V ₄
decreases. Here, when the outside temperature rises to 30℃, the output voltage V ₄ is the voltage between the 12th resistor R ₁₂ and the 13th resistor
lower than the voltage at the midpoint E of the voltage divider resistor circuit with R ₁₃ ,
The voltage at the middle point, that is, the voltage V ₅ between the terminals of the 13th resistor R 13 is applied to the (+) side input terminal of the comparator ₁₃ , and the voltage between the terminals of the internal temperature sensor 16 is applied based on this voltage V ₅ between the terminals. The voltage V ₂ is controlled, and the temperature inside the warehouse (rice grain temperature) does not rise to 28°C, which is obtained by substituting T ₁ = 30 and X = 90 into equation (S).
It is kept below 25°C determined by the voltage V ₅ between the terminals of resistor R ₁₃ .

Furthermore, when the outside temperature is 25°C and the relative humidity is 50%, the voltage between the terminals of the converter 14, V ₁ is 5V, and the voltage between the terminals of the outside temperature sensor, V ₃ , is (+) of the amplifier 12.
The side input voltage is 4V, the (-) side input voltage is 3.4V, and the difference between both input voltages is larger than when the relative humidity is 70%.The output voltage _V4 of the amplifier 12 is 11.6V, and the relative humidity is 70%. The comparator 1 compares the terminal voltage V ₅ 4.9V of the 13th resistor R ₁₃ , which is larger than that at 70%, and the voltage V ₂ between the terminals of the internal temperature sensor 16, which serves as a reference.
3 outputs an "H" signal or "L" signal, and the temperature inside the warehouse (rice grain temperature) is controlled to be higher than 15℃, which is obtained by substituting T ₁ = 25 and X = 50 into equation (S), and the outside air The difference between the temperature and the inside temperature is kept lower than 10°C, which is larger than when the relative humidity is 70%. Further, when the relative humidity remains unchanged at 50%, when the outside air temperature gradually decreases, the voltage V ₃ between the terminals of the outside air temperature sensor 11 gradually increases, and the output voltage V ₄ of the amplifier 12 increases. When the outside temperature drops to 20℃,
The output voltage V ₄ is approximately equal to the voltage supplied from the first wiring 6 to the amplifier 12, and a voltage dropped by the resistor R and the diode D is applied to the (+) side input terminal of the comparator 13. Comparing the (+) side input voltage of the comparator 13 with the terminal voltage _V2 of the internal temperature sensor 16, the comparator 13 outputs an "H" signal or an "L" signal, and the internal temperature is determined by the formula (S) to T ₁
= 20 and X = 50, the temperature did not drop to 10℃, which was determined by the voltage supplied from the first wiring 6 to the amplifier 12, and the temperature of the rice was kept higher than 15℃. It will be done. Note that when the outside temperature rises from 25°C to 30°C without changing the relative humidity, the voltage V ₃ between the terminals of the outside temperature sensor 11 decreases accordingly, the output voltage V ₄ of the amplifier 12 also decreases, and the internal temperature ( Rice grain temperature) is given in equation (S) by T ₁ = 30,
The temperature is kept higher than the 20℃ calculated by substituting X=50.

Therefore, the temperature inside the refrigerator (rice grain temperature) is maintained higher than the dew point temperature, and when the relative humidity is 70%, the difference between the outside temperature and the temperature inside the refrigerator (rice grain temperature) is less than 6℃ regardless of changes in the outside temperature. When the relative humidity rises to 90%, the difference between the outside temperature and the inside temperature (rice grain temperature) remains below 2℃, which is lower than when the relative humidity is 70%, regardless of the outside temperature. ,
Furthermore, when the relative humidity reaches 50%, the difference between the outside air temperature and the inside temperature (rice grain temperature) is kept below 10℃, and when the rice is taken out of the warehouse, both the inside and outside surfaces of the plastic bag and the It can reliably prevent dew condensation on the surface and prevent quality deterioration after the customer takes the rice home. In addition, the temperature inside the refrigerator is automatically maintained between 15℃ and 25℃, regardless of the outside temperature and relative humidity outside the refrigerator, so rice can be stored for long periods in the refrigerator without deteriorating its quality. You can also leave it there. Furthermore, when the relative humidity is high, the difference between the outside air temperature and the surface temperature of the rice grains is kept low, which not only reliably prevents dew condensation on the rice grains, but also reduces the operating time of the cooling device, and the power consumption of the refrigerator. can be reduced.

(F) Other Embodiments In the above embodiments, the food stored in the refrigerator was explained as rice grains, but similarly to the above embodiments, when the outside air relative humidity is high, the outside air is By controlling the temperature difference between the temperature and the grain temperature to be small, and increasing the temperature difference between the outside air temperature and the grain temperature when the outside air relative humidity is low, dew condensation can be prevented on the surface of the wheat when it is transported outside the warehouse. It is possible to reliably prevent this from happening, and it is possible to prevent the quality from deteriorating after the customer takes the wheat, etc. home from the rice store.

(G) Effects of the Invention As detailed above, according to the present invention, the calculation section calculates the dew point temperature determined according to the relative humidity and temperature of the outside air, outputs a voltage according to the calculated value, and also outputs a voltage according to the calculated value. The operation control unit compares the voltage between the terminals of the internal temperature sensor and the output voltage of the calculation unit, and when the voltage between the terminals is greater than the output voltage of the calculation unit, the cooling device is driven, and the voltage between the terminals By making the cooling system stop when the output voltage is lower than the output voltage of As a result, the temperature inside the refrigerator can be maintained above the dew point temperature.
Therefore, when food that is kept at approximately the same temperature as the inside temperature is transported out of the refrigerator, it is possible to prevent condensation from forming on the surface of the food, which will be maintained above the dew point temperature, and to prevent storage after transport. Therefore, deterioration in food quality can be suppressed.

[Brief explanation of drawings]

Fig. 1 is an electric circuit diagram of a food dew condensation prevention device shown as an embodiment of the present invention, Fig. 2 is a voltage characteristic diagram between the relative humidity terminals of the converter, and Fig. 3 is the outside air temperature sensor and the inside of the refrigerator. FIG. 3 is a temperature-terminal voltage characteristic diagram of a temperature sensor. 11...Outside temperature sensor, 14'...Humidity sensor, 16...Inside temperature sensor, 21...Cooling device.

Claims (1)

[Claims] 1. A humidity sensor that senses the relative humidity of outside air and outputs a voltage between terminals according to the relative humidity, an outside temperature sensor that senses outside air temperature and outputs a voltage between terminals that corresponds to the outside air temperature, and the humidity sensor and the storage A calculation unit that inputs the voltage between both terminals of the outside temperature sensor and calculates and outputs the dew point temperature determined according to the relative humidity and outside temperature from the deviation of both inputs, and senses the inside temperature of the refrigerator that stores food. An internal temperature sensor that outputs a voltage between terminals according to the internal temperature of the refrigerator, a cooling device that cools the refrigerator, an output of the calculation section and a voltage between the terminals of the internal temperature sensor, and The cooling device is configured to drive the cooling device when the voltage across the terminals of the temperature sensor is greater than the output of the computing section, and to stop the cooling device when the voltage across the terminals of the internal temperature sensor is smaller than the output of the computing section. A food condensation prevention device comprising: a cooling operation control section that controls the operation of the device.