JP4948562B2 - refrigerator - Google Patents

Description

  The present invention relates to a refrigerator, and more particularly to a temperature adjustment mechanism for refrigerated storage of food with high quality.

  In general, when refrigerated storage of foods, it is desirable to maintain a temperature range as low as possible except for foods that cause low-temperature injury or the like in order to maintain quality. However, it is known that at 0 ° C. or lower, especially below the freezing point of the food, the food is likely to freeze, and when partial freezing occurs, cell damage occurs and the quality is likely to deteriorate.

The following is a conventional technique for suppressing quality deterioration when food is stored at low temperature.
As a refrigerator that realizes a supercooled state that is not frozen while being below the freezing point, for example, “a food set that contains moisture at or above the temperature set value in the refrigerator of the heat insulation box is higher than the freezing point of the stored cold storage product. The refrigerator is operated in a refrigerated temperature zone of 0 ° C. or higher, and is stored in the supercooled temperature zone that is a set temperature below the freezing point of the cold insulated product for a predetermined time during the supercooled operation. (For example, refer to Patent Document 1).

  In addition, as a method for maintaining the supercooled state for as long as possible, for example, “Food that tends to deteriorate when frozen is quickly stored in a cooling room having a structure with high heat insulation from the outside temperature, and then sealed. Then, the food starts to freeze slightly or quickly cools to a state just before the start of freezing, and then the temperature is adjusted to a temperature not higher than 4 ° C. and higher than the temperature at which the food hardly or not freezes. There is a method of “secondary cooling” (see, for example, Patent Document 2).

  Furthermore, as a refrigerator having a function of detecting the start of freezing after the release of supercooling with a sensor and preventing the progress of freezing by changing the operation of the refrigerator, for example, “When the release of supercooling is detected, the temperature of the stored item is changed. There is a refrigerator that includes a control device that controls to perform the supercooling operation again after being raised from the freezing point, or a control device that performs control to perform an operation different from the supercooling operation (for example, patents) Reference 3).

JP 2001-4260 A (Claim 1) JP-A-62-166872 (Claim 1) Japanese Patent No. 3903066 (Claim 8 and Claim 9)

  However, in Patent Document 1, the set temperature zone time below the freezing point is specified, but since the set temperature zone time above the freezing point is not specified, the average temperature throughout the storage period becomes high and the quality is high. There was a possibility of decline. In patent document 2, since the countermeasure when a supercooled state is cancelled | released and frozen by a certain factor is not taken, the foodstuff which quality deteriorates may generate | occur | produce. In Patent Document 3, the transition to the high temperature zone is detected as the reset temperature after detecting the overcooling cancellation, but there is no provision for the temperature and time on the high temperature side, so there is a possibility that deterioration due to high temperature may proceed. .

  The present invention has been made to solve the above-described problems, and a first object is to provide a refrigerator that can stably maintain a supercooled state of food. The second object is to provide a refrigerator that can prevent ice crystals from growing into large needle-like crystals even when freezing of food is released and freezing starts.

Refrigerator according to the present invention, the coercive cold room, a refrigerating compartment and a vegetable compartment, and a temperature adjusting mechanism for cooling or heating the cold chamber, and a control means for controlling the temperature adjusting mechanism, location in the cold chamber the contained object that he a refrigerator capable of subcooled, said control means includes a first step and second step, starting the second step at the end of the first step The temperature adjusting mechanism is controlled, and the first step sets the set temperature of the cold storage chamber to a low temperature side set temperature θL lower than the freezing point of the object for the first predetermined time T1 , serial switching example high temperature side set temperature .theta.H than the freezing point to a first predetermined time T 1 after, during a second predetermined time, and set to the high temperature side set temperature .theta.H, after switching to the high temperature side set temperature .theta.H , Air that is hotter than the air in the cold room, Wherein by introducing a vegetable compartment in the cold chamber consists of a series of control that decompress the contained object, the second step, switching the set temperature again after the second predetermined time to said .theta.L, the It is characterized by comprising a series of controls for maintaining the inside of the cold insulation chamber at the aforementioned θL.

  In the present invention, even when the supercooled state of the food is released and fine ice crystals are generated almost uniformly inside the food and freezing is started, the temperature is raised to a high temperature zone at a predetermined timing. Thus, the supercooled state can be realized by dissolving the fine ice crystals generated in a short time when the supercooling is released and then returning to the low temperature range again, so that the supercooled state of the food can be maintained stably.

(A) It is a figure which shows the temperature change of the foodstuff in the case of maintaining supercooling stably during cooling. (B) It is a figure which shows the temperature change of the foodstuff when it cancels | releases supercooling in the middle of cooling, and falls into freezing. (A) It is a figure which shows the time change of the preset temperature in the temperature control which concerns on Embodiment 1 of this invention. (B) It is a figure which shows the time change of air temperature. (C) It is a figure which shows the time change of food temperature. (A) It is a figure which shows the time change of food temperature in case defrosting succeeds after generation | occurrence | production of supercooling cancellation | release. (B) It is a figure which shows the time change of food temperature in case defrosting fails after generation | occurrence | production of supercooling cancellation | release. It is a figure which shows the time change of the air temperature in the temperature control which concerns on Embodiment 1 of this invention, and food temperature. It is a figure which shows the temperature change of the foodstuff in the temperature control which concerns on Embodiment 2 of this invention. It is an example of the front view of the refrigerator provided with the cold storage room which concerns on Embodiment 3 of this invention. It is a figure which shows the result of the supercooling repetition experiment which concerns on Embodiment 5 of this invention. It is a figure which shows the time change of the air temperature in the temperature control which concerns on Embodiment 5 of this invention.

Embodiment 1 FIG.
FIG. 1 shows the temperature change when food is put in a refrigerator provided with a mechanism for cooling the inside of the cold insulation chamber to a freezing point θf or less.
FIG. 1 (A) shows that the food placed in the cold storage chamber has been stably changed at the set temperature after being cooled to the set temperature below the freezing point θf of the food. That is, it shows a case where the supercooled state of the food is maintained, which is an ideal state.

  In the case of FIG. 1A described above, the food placed in the cold storage chamber is supercooled in the low temperature range, so that quality deterioration due to ice crystal growth due to freezing does not occur. However, when a sudden temperature change occurs due to the impact of opening or closing the door or for some reason, the supercooled state is canceled, and fine ice crystals are generated almost uniformly inside the food, which may start freezing. .

  FIG. 1B shows a case where the supercooling state is canceled and freezing is started at a certain time point below the freezing point θf. When the supercooling is released, ice crystals are generated inside the food, and the state shifts to a state where water and ice coexist, and the temperature of the food changes to the food freezing point θf. After this, freezing proceeds and becomes equal to the set temperature after completion of freezing. Depending on the set temperature at this time, the quality of the food may further deteriorate.

Therefore, the air temperature in the cold room is controlled as follows. FIG. 2 shows the time-dependent changes in the air and food temperature in the cold storage chamber when one set temperature is set in the cold storage chamber on each of the high temperature side and the low temperature side and the low temperature side set temperature θL is switched from the high temperature side set temperature θH. Show.
The set temperature in the cold insulation chamber is controlled as shown in FIG. 2A so as to realize the change with time of the air temperature as shown in FIG. That is, the air is cooled from the high temperature side set temperature θH to the low temperature side set temperature θL, and the state of the low temperature side set temperature θL is maintained for a predetermined time. Next, at time T1, air heating in the cold insulation chamber is started to the high temperature side set temperature θH, and one cycle is completed at time T2.

  FIG. 2C shows a temperature change when the food does not release the supercooling when the set temperature in the cold insulation chamber is controlled as shown in FIG. If the food does not release the supercooling, the time of the food lags behind the time-dependent change in the air temperature in the cold insulation chamber, but the temperature of the food depends on the heat capacity, and is set between the high temperature side set temperature θH and the low temperature side set temperature θL. The temperature changes continuously.

On the other hand, FIG. 3 shows an example of a change in the temperature of the food when the supercooling is released.
The food placed in the cool room is supercooled in a low temperature range, but the supercooled state may be canceled if a sudden temperature change occurs due to a door opening / closing impact or some factor. When the supercooling is released, fine ice crystals are formed almost uniformly inside the food and freezing is started.

  Therefore, by detecting the start of freezing of the food at a predetermined timing or by raising the temperature to a high temperature zone, it is possible to dissolve the fine ice crystals generated in a short time when the supercooling is released. Thereafter, at a predetermined timing or by detecting the completion of thawing of the food and returning the air temperature to the low temperature range again, it is possible to suppress the quality deterioration of the food.

  FIG. 3A shows that the supercooling is released and freezing is started at time T when the food temperature becomes equal to or lower than the freezing point θf. Next, thawing is started inside the food by switching the inside of the cold storage room to the high temperature side set temperature at time T1, and thawing is completed at time Tf2. Then, the food temperature rises and reaches the air temperature (= high temperature side set temperature) θH at time T2.

  In FIG. 3B, as in FIG. 3A, freezing is started from time T and thawing is started from time T1, but since thawing is not completed at time T2, the next cycle starts. The case where cooling starts is shown. This is a case where the ice crystals remaining inside the food are used as a core, and the freezing of the food proceeds rapidly so that the food does not enter a supercooled state and reaches the low temperature side set temperature θL set below the freezing point θf of the food. It is.

  As described above, in order to avoid the freezing after the supercooling is released, when the up and down operation of the set temperature of the cold insulation chamber is repeated, the high temperature side set temperature θH, the low temperature side set temperature θL, the time T1, the time T2, the cooling rate, etc. If this setting is not fully taken into account, the supercooling release frequently occurs, the freezing occurs, or the average temperature in the cold storage chamber increases, which increases the risk of food quality degradation.

  Desirably, the fine ice crystals generated when the supercooling is released grows, and before damaging the cells, the thawing of the fine ice crystals is started and immediately after thawing without excess or deficiency, What is necessary is just to re-cool food. However, the release of supercooling depends on the stochastic state of binding between water molecules. In addition, the cooling capacity, the type and size of food, the handling method of the user, etc. vary, and since the temperature of all foods being cooled cannot be monitored each time, the necessary and sufficient parameters are selected and the temperature up / down control sequence is selected. Need to be determined.

Therefore, in the present invention, the following temperature control is performed. FIG. 4 shows temperature changes in the air and food in the cold storage chamber by the preset temperature switching control according to Embodiment 1 of the present invention. The control unit for controlling the air temperature in the cool room is controlled so that the set temperature in the cool room is the low temperature side set temperature θL during the air low temperature set time TL and the high temperature side set temperature θH during the air high temperature set time TH. . At this time, in the food temperature graph, in region 1, the supercooling of the food starts to be released at time T, and a small amount of ice crystals are instantaneously generated when the supercooling is released. In region 2, freezing proceeds with a small amount of ice crystals as nuclei. In region 3, heat is applied to the ice generated in region 2, and thawing proceeds.
In addition, on the graph of the food temperature of FIG. 4, the latent heat Q1 released when changing from water to ice, the latent heat Q2 taken away from the water during the freezing process, and the heat Q3 given to the ice during the thawing process are shown. is there.

As a result of experiments from the above viewpoint, regarding these three calories (Q1, Q2 and Q3), if the temperature control is performed so as to satisfy the following formula, the food is thawed sufficiently even when the supercooling is released. It was found that the supercooled state can be realized again.
That is, in a food that changes in temperature as shown in FIG.
Q3 ≧ Q1 + Q2
Q1: Latent heat when supercooling is released
= Δ (θT−θL) (K) × W (g) × Cp (J / g · K)
Q2: Latent heat accumulated during freezing while it is in a low temperature zone after overcooling is released
= Δ (θf−θL) (K) × (T1-T) (sec)
× kf (J / sec · K)
Q3: Heat given to food during thawing while in a high temperature zone
= Δ (θf−θH) (K) × (Ttw−Tf) (sec)
× ktw (J / sec · K)
θT: temperature at which supercooling is released θL: low temperature set temperature W: water content of food Cp: heat capacity of water θf: freezing point of food T1: low temperature set time T: from low temperature setting to start cooling until supercooling is released Time kf: heat transfer coefficient during cooling θH: high temperature side set temperature Ttw: thawing completion time Tf: time to reach food freezing point while air temperature is rising at high temperature setting ktw: heat transfer coefficient during temperature rise The heat transfer coefficient kf can be estimated from the cooling rate and the heating rate while the food is not frozen. The time T at which the food starts to be supercooled and the freezing temperature θTf of the food can be determined from a test using a representative food to be cooled. Therefore, the above constants are calculated and determined by a simple experiment, and the high temperature side set temperature θH, the low temperature side set temperature θL, and the low temperature set time T1 are controlled so as to satisfy the above relational expression. Quality preservation is possible.

Embodiment 2. FIG.
FIG. 5 shows a simpler temperature up / down sequence setting method according to the second embodiment of the present invention. In this method, the cooling operation time (low temperature setting time TL) is controlled to be longer than the heating operation time (high temperature setting time TH). In other words, it is only necessary to control so that the integrated time when the food is below the freezing point is longer than the integrated time when the food is above the freezing point. That the low temperature time is long means that the relational expression Δ (θL−θf) <Δ (θH−θf) is satisfied. By setting in this way, it becomes difficult for supercooling cancellation to occur. Further, the average temperature of the food can be lowered, and the food can be stored at high quality.

Embodiment 3 FIG.
Among the foods, tests on fresh foods that are required to be stored without freezing revealed that foods can be stored in high quality by setting the average temperature in the cold storage chamber to 1 ° C. or lower. Moreover, it turned out that the occurrence probability of the supercooling cancellation | release of a foodstuff can be suppressed by making the average temperature of a cold storage room more than the freezing point of the foodstuff to be cooled. Although the freezing temperature of food varies, it can be set to about −2 ° C. for sashimi and about −5 ° C. for raw meat. By setting the average temperature to 1 ° C. or lower and the freezing point or higher, the probability of canceling the supercooling can be suppressed low. By realizing a state in which it is difficult to release the supercooling, it is possible to reduce the possibility of falling into a frozen state that causes a deterioration in quality.

  The temperature set as the low temperature zone (low temperature side set temperature) is preferably as low as possible, but is preferably between 0 ° C. and −20 ° C. which is the freezing point of water from the viewpoint of energy consumption necessary for cooling. Further, it was found that when the temperature was changed from −2 ° C. to −7 ° C., the supercooling release hardly occurred. Further, it was found that the supercooling release hardly occurs when the cooling rate is changed from 300 ° C./hour to 0.35 ° C./hour. That is, by setting the temperature as described above, it is possible to preserve food with high quality.

  As the temperature set as the high temperature zone (high temperature side set temperature), the lower the temperature, the lower the quality of the food, but the longer the thawing time. From such a viewpoint, the high temperature zone is preferably between 0 ° C. and 20 ° C., which is the melting point of water, and more preferably in the range of 3 ° C. to 7 ° C. Note that in order to realize a high temperature zone, an electromagnetic field such as a heat exchanger, a heater, a Peltier element, or a microwave may be applied, but these require energy other than cooling. In addition, the above-mentioned numerical value is based on the performance limit of a household refrigerator.

FIG. 6 shows an example of a general household refrigerator having a plurality of rooms set at a plurality of temperatures. The refrigerator main body 101 includes a refrigerator compartment 102, a cold storage compartment 103, an egg compartment 104, an ice making compartment 105, a switching room 106, a freezing compartment 107, and a vegetable compartment 108. A ventilation path 1 is provided between the refrigerator compartment 102 and the cold insulation chamber 103.
In the case of a general household refrigerator, the refrigerator compartment 102 is often set to 3 ° C to 5 ° C. As shown in FIG. 6, the cold insulation chamber 103 of the present invention is provided in a part of the refrigerator main body 101, and at the time of cooling, cold air generated by passing through a cooling heat exchanger (not shown) is kept in the cold insulation chamber 103. The air in the refrigerator compartment 102 having a temperature higher than that of the cold insulation chamber 103 may be introduced into the cold insulation chamber 103 during heating or indirect cooling. By adopting the above-described structure, a heating device other than the original cooling heat exchanger of the refrigerator main body 101 is not required, and there is no energy loss to a heat source such as a heater. That is, a heat source for generating high-temperature air is unnecessary, and extra parts and energy are also unnecessary.

  In FIG. 6, the air in the refrigerator compartment 102 is introduced, but the air in the vegetable compartment 108 set to a temperature higher than that of the cold storage compartment 103 or the air outside the refrigerator main body 101 may be introduced. When the temperature of the cold insulation chamber 103 rises, the power loss can be reduced by introducing air from other chambers in the refrigerator main body 101 without using a heater or the like. In addition, the cooling heat exchanger may be heated to introduce the warm air into the cold insulation chamber 103.

Embodiment 4 FIG.
As a result of examining the control of the temperature of the cold room in more detail, the low temperature setting time is set to 120 to 240 minutes, and the high temperature setting time is set to 140 to 230 minutes, so that the food can be stored with high quality maintained. I found out that Therefore, in consideration of control redundancy, by setting one cycle from the start of the high temperature side set temperature to the end of the low temperature set temperature within the range of 4 hours to 9 hours, food can be stored in a high quality state. It becomes possible.

Embodiment 5 FIG.
FIG. 7 shows the experimental results of verifying the likelihood (probability) of canceling the supercooling when the supercooling is repeated according to the fifth embodiment of the present invention.
When the temperature up / down control is repeated and the probability of canceling the supercooling is verified, as shown in FIG. 7, when the number of the temperature up / down control increases, the probability of releasing the supercooling gradually increases, and the start time of the supercooling release It turns out that there is a tendency to become short gradually.

  Therefore, as shown in FIG. 8, when the next temperature up / down control is performed after the supercooling is repeated several times, the ratio of the low temperature set time (TL) / high temperature set time (TH) can be reduced. desirable. That is, (TLa / THa)> (TLb / THb) may be satisfied. Here, the subscript a means initial, and the subscript b means after several cycles. In addition, after several cycles of temperature up / down control, it is desirable to set at least one of the low temperature side set temperature and the high temperature side set temperature to a higher temperature. By appropriately combining these, it is possible to suppress an increase in the occurrence probability of cancellation of supercooling, and food can be stored in a high quality state.

  In addition, by changing the temperature up / down control with the storage period of the food, it is possible to more stably store under cooling. For this purpose, it is preferable to provide a control for increasing at least one of the low temperature set temperature and the high temperature set temperature as the food storage period becomes longer.

Embodiment 6 FIG.
In the above, in order to keep the temperature as low as possible while reducing the probability of canceling the supercooling, the timing of the temperature up and down is determined by a preset time. It is desirable to detect the state and control the temperature accordingly. For this purpose, a sensor for detecting the temperature of the food may be provided in the cold insulation chamber, and the temperature adjustment mechanism may be operated so that the food temperature becomes a preset temperature.
As a sensor for detecting the food temperature, there is a method for detecting infrared rays emitted from the food surface. In addition, there is a method in which a radio wave radiation antenna and a detector are combined by utilizing the fact that the moisture content of food varies depending on temperature.

  Or you may provide the sensor which detects whether the water | moisture content in a foodstuff is a liquid or ice. As a freezing detection sensor, there is a method of detecting a difference in dielectric constant between water and ice using the above-described radio wave radiation antenna and detector. At this time, the frequency of the radiated radio wave may be changed, and the determination of water and ice may be made based on the detected intensity at several frequencies. By changing the temperature up / down control based on food sensing information, it is possible to more stably store under cooling.

  Furthermore, there is a method of detecting infrared rays that are reflected or transmitted by emitting infrared rays to food. There is also a method of detecting sound reflected or transmitted by applying sound waves to the food itself or propagating sound waves through the food. In addition, when using the sensor which detects freezing, the above-mentioned periodic temperature up-and-down control may be stopped and it may preserve | save for a long term with a low-temperature setting. That is, a predetermined temperature rise may be performed at the time when freezing is detected, the frozen ice is melted, and the low temperature setting is performed again.

  According to the present invention, in a refrigerator provided with a mechanism for raising and lowering the temperature of food, by repeating the temperature range below the freezing point and above the freezing point at a predetermined timing, it is possible to avoid the progress of freezing and to lower the temperature. The supercooled state can be maintained more stably, and the food can be stored in a high quality state. As a result, the food can be stored for a long time in a state where the food is delicious and the merchantability is maintained, which can contribute to reduction of waste of food and energy saving.

  DESCRIPTION OF SYMBOLS 1 Air supply path, 101 Refrigerator main body, 102 Cold storage room, 103 Cold storage room which applies this invention, 104 Egg room, 105 Ice making room, 106 Switching room, 107 Freezing room, 108 Vegetable room, Q1 When supercooling is cancelled | released Latent heat, Q2 Latent heat accumulated during freezing while in the low temperature zone after cancellation of supercooling, Q3 Heat given to food during thawing while in the high temperature zone, θT Temperature to cancel supercooling, θL Low temperature Air temperature at the time of setting, W Water content of food, Heat capacity of Cp water, θf Freezing point of food, T1 Low temperature setting time, T Time from the start of cooling after low temperature setting to release of supercooling, heat during kf cooling Transfer coefficient, θH Air temperature at high temperature setting, Ttw thawing completion time, Tf Time to reach food freezing point while air temperature is rising at high temperature setting, ktw Heat transfer coefficient during temperature increase, THA initial high temperature side Constant temperature time maintaining time maintaining TLa initial low temperature side set temperature, time maintaining the high temperature side set temperature after THb periodic number elapses, the low temperature-side set temperature maintenance time after TLb of period elapses.

Claims (15)

Holding a cold room, and a refrigerator compartment and a vegetable compartment,
A temperature adjustment mechanism for cooling or heating the cold insulation chamber;
Control means for controlling the temperature adjustment mechanism,
A refrigerator capable of supercooling an object to be placed in the cold storage chamber,
The control means includes
It has first and second steps,
It controls the temperature adjustment mechanism to start the second step at the end of the first step,
The first step includes
During the first predetermined time T1, the set temperature of the cold storage chamber is set to a low temperature side set temperature θL lower than the freezing point of the object to be stored ,
Switching example high temperature side set temperature .theta.H than before Symbol the freezing point after the first predetermined time T 1 elapses during a second predetermined time, and set to the high temperature side set temperature .theta.H,
After switching to the high temperature side set temperature θH, from a series of controls to defrost the contents by introducing air that is hotter than the air in the cold storage chamber from the cold storage room or the vegetable room to the cold storage room. Configured,
The second step includes
The refrigerator is configured by a series of controls of switching the set temperature to the θL again after the second predetermined time elapses and maintaining the cold storage chamber at the θL. The time until the supercooling release a third predetermined time T from the start of cooling before Symbol contained object,
Before SL .theta.L, the θH and the T1 is
Temperature θT at which the object to be supercooled is released, water content W of the object to be stored, heat capacity Cp of water, freezing point θf of the object to be stored, T, heat transfer coefficient kf of the object to be cooled The amount of heat calculated from the thawing completion time Ttw of the object to be stored, the time Tf at which the object reaches the freezing point during the temperature increase, and the heat transfer coefficient ktw of the object to be increased is Q3 ≧ Q1 + Q2. The refrigerator according to claim 1, wherein the refrigerator is determined so as to satisfy.
Q1 = Δ (θT−θL) (K) × W (g) × Cp (J / g · K)
Q2 = Δ (θf−θL) (K) × (T1-T) (sec)
× kf (J / sec · K)
Q3 = Δ (θf−θH) (K) × (Ttw−Tf) (sec)
× ktw (J / sec · K) The refrigerator according to claim 1 or 2, wherein the control means sets the first predetermined time T longer than the second predetermined time. The control means has an integrated time ΣTL in which the temperature of the object to be stored is lower than the freezing point and an integrated time ΣTH in which the temperature of the object to be stored is higher than the freezing point, so that ΣTL> ΣTH. The refrigerator according to any one of claims 1 to 3, wherein the temperature adjustment mechanism is controlled as follows. The refrigerator according to any one of claims 1 to 4, wherein the control means controls the temperature adjusting mechanism so that an average temperature of the air in the cold insulation chamber or the objects to be contained is 1 ° C or less. . The said control means controls the said temperature adjustment mechanism so that the average temperature of the air in the said cold storage room or the said to-be-contained object may be more than the said freezing point. refrigerator. The refrigerator according to any one of claims 1 to 6, characterized in that in the range of 7 ° C. - said θL from -2 ° C.. The said control means controls the said temperature adjustment mechanism so that it may become 0.35 degree-C / hour <= v <= 300 degree-C / hour at the cooling rate v at the time of the switching from the said θH to the said θL. The refrigerator in any one of 1 thru | or 7. The refrigerator according to any one of claims 1 to 8, wherein the θH is in a range of 3 ° C to 7 ° C. The control means adjusts the temperature of the cold insulation chamber by introducing the air in a compartment in the refrigerator provided separately from the cold insulation chamber into the cold insulation chamber. The refrigerator according to any one of 9. The refrigerator according to any one of claims 1 to 10, wherein the first step is performed at least once in a period of 4 hours to 9 hours. The control for gradually decreasing the ratio of (low temperature temperature zone setting time) / (high temperature temperature zone setting time) as the storage time of the objects to be contained is performed. Refrigerator. The refrigerator according to any one of claims 1 to 12, wherein control for gradually increasing at least one of the θL and the θH is performed as the storage time of the contents to be stored becomes longer. A temperature detection sensor for detecting the temperature of the object to be contained;
The refrigerator according to any one of claims 1 to 13, wherein the control means adjusts the temperature in the cold storage room based on data obtained from the temperature detection sensor. Comprising a freezing detection sensor for detecting a frozen state of the object to be contained;
The refrigerator according to any one of claims 1 to 14, wherein the control means adjusts the temperature in the cold storage room based on data obtained from the freezing detection sensor.

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