JP2010243103A - Method of adjusting oxygen concentration in food storage space - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem on high cost as an oxygen sensor is expensive in adjusting oxygen concentration by using the oxygen sensor, in a case when the oxygen concentration in the food storage space is decreased by an oxygen concentration adjusting means applying an ion conductive high polymer solid electrolyte membrane. <P>SOLUTION: A control method for calculating the oxygen concentration Xi in the food storage space from an integrated value Ai of electric current values flowing in the oxygen concentration adjusting means, and determining a time to switch off (stopping operation) of the oxygen concentration adjusting means on the basis of the relationship between the oxygen concentration and a target oxygen concentration, is used. Thus the oxygen concentration of the food storage space can be adjusted at low costs without using the oxygen sensor. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for controlling the oxygen concentration of a storage such as a refrigerator that enables adjustment of the oxygen concentration of an atmosphere in which food is stored.

  As a method for preserving food for a long period of time, freezing is generally used. However, frozen storage destroys the tissue of food, and for meat and the like, it cannot be denied that the taste is lowered by the outflow of drip upon thawing.

  In addition, the freezing storage has a drawback in that it takes time for thawing when cooking. In addition, a method for reducing the oxygen concentration has been devised as a means for long-term storage, and it is possible to prevent oxidation and discoloration of fats and oils in foods.

  As an effective deoxygenation technique for that purpose, an electrochemical oxygen concentration adjusting means using a polymer solid electrolyte membrane is known, and a refrigerator using this is proposed (Patent Document 1), but it has been put into practical use. Not in.

  In this method, the following elements are used. The structure of the element is such that a catalyst layer such as platinum is provided on both sides of a cation conductive polymer solid electrolyte, and a supply electrode is provided on both sides thereof. By applying a voltage to the supply electrode, water is decomposed and oxygen and hydrogen ions are generated on the anode side, and the generated hydrogen ions move to the cathode side in the polymer solid electrolyte. The cathode faces a space to be deoxygenated, and oxygen in the space reacts with hydrogen ions moved from the anode to generate water. Apparently, the oxygen on the cathode side decreases and the oxygen on the anode side increases, so that it acts as an oxygen pump and can reduce the oxygen concentration on the cathode side.

  In addition, oxygen concentration adjusting means using an anion conductive polymer solid electrolyte instead of a cation conductive polymer solid electrolyte is also known. In this case, oxygen is reduced together with water on the cathode side. Hydroxyl ions are generated, and are moved in the polymer solid electrolyte from the cathode to the anode by the electric field to which they are applied, and are oxidized at the anode to generate oxygen and water. Therefore, in the case of an anion conducting membrane, oxygen is pumped from the cathode to the anode (Patent Document 2).

  The oxygen concentration can be adjusted by operating the oxygen pump to reduce the oxygen concentration in the food storage space. At that time, the oxygen concentration in the food storage space is detected by an oxygen sensor, A method for stopping the oxygen pump and introducing air from the outside is disclosed (Patent Document 3).

In addition, the oxygen concentration adjusting means using a solid polymer electrolyte is driven by applying a constant voltage, regardless of whether it is cationic or anionic, its deoxygenation rate and oxygen enrichment rate strongly depend on the humidity of the atmosphere. In this case, it is known that the deoxygenation rate fluctuates greatly due to a change in humidity.
JP-A-2005-48977 Japanese Patent Laid-Open No. 10-100028 JP 2008-134054 A

When oxygen concentration is reduced by removing oxygen in the cathode side space for storing food or the like by the oxygen concentration adjusting means using the solid polymer electrolyte, 1/2 to 1/4 of the oxygen concentration in the air If the concentration is not set, a clear effect cannot be obtained. However, when the solid polymer electrolyte is cationically conductive, excessive hydrogen ions may be supplied relative to the amount of oxygen in the air if the oxygen concentration adjusting means is continuously operated to reduce the oxygen concentration. In this case, the oxygen concentration becomes almost zero, and hydrogen is generated from excess hydrogen ions, which may cause an explosion or the like. In addition, when the polymer solid electrolyte is anion-conductive, hydrogen is not generated due to excessive supply of hydrogen ions. However, when the stored food is vegetable, the oxygen concentration is almost zero. There was a problem that deterioration progressed due to oxygen respiration.

  On the other hand, the above problem can be solved by monitoring the oxygen concentration with an oxygen sensor and operating the oxygen concentration adjusting means according to the oxygen concentration. However, since the oxygen sensor is expensive, it is realized at a low cost. There was a problem that it was difficult.

  The following explains the mechanism of hydrogen release and the reason why it is difficult to avoid excessive supply of protons.

  First, the mechanism of hydrogen release is as follows.

  Even when deoxygenation progresses and the oxygen concentration becomes 0, the supply of hydrogen ions from the anode to the cathode continues as long as a voltage is applied to the oxygen concentration adjusting means. This hydrogen ion should react with oxygen originally, but since there is no oxygen, it is reduced at the cathode to become hydrogen and released into the space on the cathode side.

  The present invention solves the above-mentioned conventional problems, avoids hydrogen release to a space for storing food and the like and anaerobic breathing of vegetables, and safe food storage at a target oxygen concentration at a low cost. An object is to provide a storage such as a refrigerator.

  In order to solve the above conventional problems, the method for adjusting the oxygen concentration in the food storage space of the present invention comprises an oxygen concentration adjusting means comprising a solid polymer electrolyte membrane having ion conductivity sandwiched between an anode and a cathode; A method for controlling the oxygen concentration of the food storage space in a storage having a food storage space capable of adjusting the oxygen concentration by using the oxygen concentration adjusting means, wherein a voltage is applied between the anode and the cathode. Then, a current is supplied to the oxygen concentration adjusting means, a deoxygenation amount is calculated from an integral value of the current, and a stop timing of the oxygen concentration adjusting means is determined from the initial oxygen amount and the deoxygenation amount in the food storage space. It is characterized by doing.

  Since the deoxygenation amount can be calculated from the integrated value of the current flowing through the oxygen concentration adjusting means, the oxygen concentration in the food storage space can be calculated based on the initial oxygen amount in the food storage space. If the oxygen concentration adjusting means is stopped when the calculated oxygen concentration is reached, the target oxygen concentration is realized, hydrogen ions are not excessively supplied during deoxygenation, and hydrogen release is avoided. Moreover, the oxygen concentration does not become zero, and the deterioration of the vegetables due to anoxic respiration does not proceed. As a result, it is possible to obtain the effect of safely realizing the target oxygen concentration at a low cost.

  In the storage room for adjusting the oxygen concentration according to the present invention, no deterioration occurs due to anoxic respiration of vegetables whose oxygen concentration is almost 0, and excessive supply of hydrogen ions does not occur, so that release of hydrogen is avoided. The space in which food is stored can be safely and efficiently made the target oxygen concentration at low cost. As a result, it is possible to obtain an effect that enables food to be stored safely in a high quality state for a long period of time at a low cost.

According to a first aspect of the present invention, there is provided an oxygen concentration adjusting means comprising a solid polymer electrolyte membrane having ion conductivity sandwiched between an anode and a cathode, and food preservation capable of adjusting the oxygen concentration by using the oxygen concentration adjusting means. And a method for controlling the oxygen concentration of the food storage space in a storage room having a space,
Applying a voltage between the anode and the cathode to pass a current through the oxygen concentration adjusting means, calculating a deoxygenation amount from an integral value of the current, and an initial oxygen amount in a space leading to the food storage space; It is constituted by determining the stop time of the oxygen concentration adjusting means from the deoxygenation amount.

  The amount of oxygen removal is determined by the integrated value of the current flowing through the oxygen concentration adjusting means. For this reason, if the volume of the initial food storage space is known, the oxygen concentration can be calculated without detecting the oxygen concentration using an oxygen sensor. Furthermore, when the calculated oxygen concentration reaches the target oxygen concentration, the operation of the oxygen concentration adjusting means is stopped, so that the oxygen concentration of the food storage space can be adjusted at a low cost without using an oxygen sensor. The effect becomes. At this time, supply of excess hydrogen ions to oxygen in the food storage space does not occur, and all the hydrogen ions react with oxygen to become water. In this way, the release of hydrogen is avoided, and the effect of enabling safe oxygen concentration adjustment and high-quality food storage is obtained.

  In particular, the second invention has a configuration in which, in the first invention, the value of the current flowing through the oxygen concentration adjusting means is constant.

  Since the value of the current flowing through the oxygen concentration adjustment means is constant, the calculation of the integrated value of the current becomes a simple product of the value of the current and the time when the current is passed, and there is no need for complicated integration. The effect of reducing the load on the food storage and adjusting the oxygen concentration in the food storage space at a lower cost can be obtained.

  In the third invention, in particular, in the second invention, when the current applied to the oxygen concentration adjusting unit is controlled at a constant current, the voltage applied to the oxygen concentration adjusting unit exceeds an allowable maximum value. It is configured by reducing the current value for constant current control.

  If the voltage applied to the oxygen concentration adjusting means becomes too high in order to keep the current value constant, the degradation of the catalyst progresses over a long period of time, the current value decreases, and the deoxygenation rate increases. The long-term reliability cannot be secured. The allowable voltage is determined by the required durability (time to secure the characteristics).

  On the other hand, when the relative humidity of the atmosphere decreases, the ionic conductivity of the solid electrolyte decreases and the resistance increases, so that the applied voltage increases under constant current control. For example, when the temperature rises and the relative humidity decreases, for example, by opening a storage door, the voltage increases. In this case, if the humidity is too low, the applied voltage exceeds the allowable maximum value, and the above-described deterioration tends to proceed.

  On the other hand, when the voltage applied to the oxygen concentration adjusting means exceeds the allowable maximum value, the voltage can be adjusted below the allowable value by reducing the constant current value. The effect of ensuring the reliability is obtained.

  In the fourth invention, in particular, in the second or third invention, when the current flowing through the oxygen concentration adjusting means is subjected to constant current control, the voltage applied to the oxygen concentration adjusting means falls below an allowable maximum value. Is configured by increasing the current value for constant current control.

  As the relative humidity of the atmosphere increases, the ionic conductivity of the solid electrolyte increases and the resistance decreases, so that the applied voltage decreases under constant current control. For example, when the door of an open storage is closed, the relative humidity increases as the temperature decreases, and the applied voltage decreases.

  Since the value of the current flowing through the oxygen concentration adjusting means increases as the relative humidity of the atmosphere increases, when the relative humidity increases due to a decrease in the temperature of the atmosphere or the like, the voltage applied to avoid an increase in the current value decreases.

  On the other hand, when the voltage applied to the oxygen concentration adjusting means falls below the allowable maximum value, the oxygen concentration can be adjusted more efficiently by having a configuration in which the current value for constant current control is increased. The effect becomes.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments.

(Embodiment 1)
In the present embodiment, taking a storage room having a deoxygenation auxiliary container as an example, the present invention “deoxygenation amount is calculated from the integrated value of current at the time of deoxygenation, and the initial oxygen amount in the space leading to the food storage space” The stop time of the oxygen concentration adjusting means is determined from the amount of deoxygenation and the oxygen removal amount ”.

  FIG. 1 is a cross-sectional view showing a food storage space through which a deoxygenation auxiliary container that can adjust the oxygen concentration in a refrigerator as a storage in the present embodiment.

  FIG. 1 shows one of a plurality of storage chambers of a refrigerator as a storage, which is formed by a storage chamber door 1 on the entire surface, a heat insulating partition wall 2 on the upper and lower surfaces, and a partition plate 4. A food storage container 7 whose inside is a food storage space 8 is connected to the deoxygenation auxiliary container 6 while maintaining air permeability. In the figure, for simplicity, the inorganic substances of the cathode and the anode of the oxygen concentration adjusting means 5 are omitted, but the deoxygenation auxiliary container 6 leading to the food storage space 8 has an internal deoxygenation. Therefore, the cathode side of the oxygen concentration adjusting means 5 is arranged facing the inside of the deoxidation auxiliary vessel 6. Similarly, although omitted, the food storage container 7 has a sealable opening / closing part in the inside view of the deoxidation auxiliary container leading to the food storage space 8, and food can be taken in and out from there. It is.

  In addition, a cooler, a fan, etc. are installed in the space between the partition plate 4 and the main body heat insulating wall 3 or the space connected thereto, and cool air is supplied to the storage room. Equipment, fans, etc. are omitted.

  FIG. 2 shows the procedure for controlling the oxygen concentration during deoxygenation of the food storage space of the present embodiment.

  Below, the specific procedure of oxygen concentration control is demonstrated using FIG. 2, referring FIG.

  First, before the oxygen concentration is controlled, the food storage container 7 is opened, and after the food is placed in the food storage container 7, the food storage container 7 is sealed.

  Subsequently, the oxygen concentration is controlled according to the actual procedure. As shown in FIG. 2, first, the items shown in the preparation block are performed. Specifically, the target oxygen concentration of the food storage space is set and the volume of the food storage space is calculated.

The volume of the food storage space is precisely defined from FIG. 1 as a volume other than the volume occupied by the food in the food loss container 7 and the volume in the deoxygenation auxiliary container 6. However, since the volume of the food is not constant and it is difficult to accurately determine the volume of the food storage space, the volume of the food storage space is ignored for the sake of convenience, ignoring the volume of the undefined food storage container. Is assumed to be equal to the volume of. The target oxygen concentration is set to 0 for simplicity. Actually, even if the oxygen concentration in the deoxygenation auxiliary container becomes 0, the oxygen concentration in the food storage space does not become 0 or almost 0 because air in the food storage container exists. That is, the deoxygenation auxiliary container has an effect of preventing the oxygen concentration in the food storage space from becoming zero.

  After the preparation block is finished, the standard voltage V0 is applied to the oxygen concentration adjusting means. By doing so, the oxygen concentration adjusting means is turned on.

  Next, an oxygen concentration adjustment procedure surrounded by a broken line is performed.

Specifically, first, at every fixed time t _0, calculates an integrated value A1 (A) of the current value. Further, taking into account that four electrons correspond to one oxygen molecule, the amount of deoxygenation is calculated from A1 (A). Next, the oxygen concentration in the food storage space is calculated using this deoxygenation amount. At the time of calculation, the oxygen concentration X is calculated on the assumption that the volume of the deoxygenation auxiliary container is the volume of the food storage space and oxygen corresponding to the deoxygenation amount is removed therefrom as described above. Finally, the oxygen concentration X in the food storage space calculated above is compared with the target oxygen concentration 0. If X is 0 or less, the voltage applied to the oxygen concentration adjusting means is set to 0, and the oxygen concentration adjusting means Is turned off. If the oxygen concentration X is larger than 0, the above operation is repeated again after time t0.

  By the above operation, oxygen corresponding to the volume in the deoxygenation auxiliary container is removed. The oxygen concentration in the food storage space can be determined by the volume of the deoxygenation auxiliary container and the volume other than food in the food storage container. For example, if the ratio is 2: 1, the oxygen concentration in the food storage space is about 7%. It becomes. By changing this volume ratio, the oxygen concentration level of the food storage space can be set.

  As described above, by using the method of the present invention, it is possible to avoid the oxygen concentration in the food storage space from being close to 0, and to obtain the effect of avoiding hydrogen generation and deterioration due to oxygen-free breathing of vegetables.

  Next, the configuration and operation of the oxygen concentration adjusting means will be described in detail with reference to FIG. 3, taking as an example an oxygen concentration adjusting means using a polymer solid electrolyte having cation conductivity.

  FIG. 3 is a cross-sectional view of the oxygen concentration adjusting means 5 in the present embodiment. As shown in FIG. 3, the oxygen concentration adjusting means 5 has a polymer solid electrolyte membrane 12 at the center, a cathode 13 on the left side, an anode 14 on the right side, and a supply electrode 15 provided outside each electrode. In addition, these are fixed by a frame 11. Further, the oxygen concentration adjusting means 5 is configured so that the cathode 13 is inside the deoxygenation auxiliary hand vessel 8 and the anode 14 is outside the deoxygenation auxiliary vessel 8 in order to deoxygenate the inside of the deoxygenation auxiliary vessel 8. Be placed.

  Subsequently, the operation of the oxygen concentration adjusting means 5 will be described with reference to FIG. The voltage application to the oxygen concentration adjusting means 5 is performed by voltage application to the two supply electrodes 15. By this voltage application, water vapor in the air is electrolyzed on the anode 14 side to generate oxygen, and simultaneously generated hydrogen ions are passed through the polymer solid electrolyte membrane 12 from the anode 14 to the cathode 13 by the applied voltage. Move to. Since water is supplied as water vapor from the space on the anode 14 side, the humidity in the space on the anode 14 side decreases.

  On the other hand, oxygen in the cathode 13 side space reacts with hydrogen ions that have moved to the cathode 13 side to become water. Thus, deoxidation on the cathode 13 side proceeds. At this time, much of the generated water is taken into the electrolyte membrane, but a part of the water is released to the cathode 13 side space and raises the humidity of the corresponding space. Further, the water taken into the electrolyte moves to the anode 11 side and is decomposed into oxygen and hydrogen ions.

  Accordingly, as a whole, the oxygen concentration in the cathode 13 side space decreases and the oxygen concentration on the anode 14 side increases, so that oxygen is pumped from the cathode 13 side to the anode 14 side. At the same time, the water vapor is pumped from the anode 14 side to the cathode 13 side.

  As the polymer solid electrolyte membrane 12 used in the present embodiment, for example, a perfluorocarbon sulfonic acid membrane (film thickness: several tens of microns to several hundreds of microns) is preferably used. For the anode 14 and the cathode 13, a porous electrode is used which has a suitable water repellency by pressure molding a mixture of a carbon powder carrying a catalyst such as platinum and a fluororesin powder. Further, a carbon cloth, carbon paper, or the like is used for the power supply body 12. However, the anode 14 is preferably formed by forming a platinum layer directly on the polymer solid electrolyte 12 without using carbon powder that is easily oxidized by applying a voltage as a carrier such as platinum. Further, as the anode-side suction electrode 15, mesh-like titanium whose surface is platinum-plated is preferably used instead of the carbon paper or carbon cloth.

  In addition, the structure and material of each part described in this Embodiment can be applied suitably also in the following embodiment, unless the difference in structure is described.

(Embodiment 2)
Next, a second embodiment will be described.

  In the present embodiment, the same configuration as that of the first embodiment has the same operational effects, and the same reference numerals are given and description thereof is omitted. Therefore, only different parts will be described.

  The structural feature of the present embodiment is that constant current control is performed on the current flowing through the oxygen concentration adjusting means when oxygen concentration adjustment is performed. The configuration of the food storage space and the oxygen concentration adjusting means in which the deoxygenation auxiliary container is connected with air permeability is the same as that of the embodiment.

  Since the current flowing through the oxygen concentration adjustment means is a constant current, no complicated calculation is required when calculating the integral of the current value, the circuit required for the calculation is simplified, and the oxygen concentration can be adjusted at a lower cost. The effect which becomes possible is acquired.

  Note that the configuration described in this embodiment can be preferably applied to the following embodiment, unless the difference in configuration is particularly described.

(Embodiment 3)
Next, a third embodiment will be described.

  In the present embodiment, the same configuration as in the first and second embodiments has the same operational effects, and the same reference numerals are given and the description thereof is omitted. Therefore, only different parts will be described.

  The structural feature of the present embodiment is that the voltage applied to the oxygen concentration adjusting means is provided with an allowable maximum value, and the procedure for increasing the current value when the applied voltage falls below the maximum allowable voltage. Is to introduce.

  Below, the oxygen concentration control method in this Embodiment is demonstrated using FIGS.

First, the outline of the oxygen concentration control method will be described with reference to FIG.
First, the preparation block procedure is performed, and then a voltage is applied to the oxygen concentration adjusting means to turn on the oxygen concentration adjusting means. Next, the procedures of the two blocks of the oxygen concentration adjusting means off determination block and the current value control block are performed in parallel. The former is to stop the operation of the oxygen concentration adjusting means according to the amount of deoxygenation, and the latter is to change the level of the current value under constant current control by the voltage applied to the oxygen concentration adjusting means. Is. As will be described later, the minimum unit in the hand is repeatedly executed for each of the two blocks at time t0, and this repetition is determined to be off in the oxygen concentration adjusting means off determination block. Continue to turn off (stop operation).

  Next, the oxygen concentration adjusting means off determination block will be described in detail with reference to FIG. From FIG. 5, first, the integral value of the current value is calculated at every fixed time t0. The calculation is performed by adding the current value Ii at each time over the continuous time t0 (t0 × (I1 + I2 + I3...)). Next, the food storage space oxygen concentration Xi is calculated in the same manner as in the first embodiment. Thereafter, the oxygen concentration Xi is compared with the target oxygen concentration (= 0). If the oxygen concentration Xi is 0 or less, the oxygen concentration adjusting means is turned off. Start the procedure.

  Next, the current value control block will be described in detail with reference to FIG.

  As shown in FIG. 6, in this block procedure, first, the voltage Vi applied to the oxygen concentration adjusting means realizing the current value Ii at that time is compared with the maximum allowable voltage Vmax, and the former is compared. If is large, constant current control is performed by reducing the current value. When the voltage Vi is smaller than the maximum allowable voltage Vmax, constant current control is performed by increasing the current value. If the voltage Vi is equal to the maximum allowable voltage Vmax, the constant current control is continued without changing the current value.

  Next, FIG. 7 shows the relationship between the value of the current flowing through the oxygen concentration adjusting means and the voltage applied to the oxygen concentration adjusting means when the oxygen concentration is controlled as described above.

  Although the initial current value I0 is set to be relatively small, the voltage for securing the current I0 is close to Vmax + 1/10 × Vmax because the humidity is low immediately after the food storage container is closed. ing. However, when the humidity increases with time, the voltage drops considerably at time t0, and becomes a value lower than Vmax-1 / 10 × Vmax. For this reason, at time t0, the current value is increased and constant current control is performed. At time t0 to 2t0, the voltage initially increases due to the increase in the current value, but the voltage decreases as the humidity increases. This is the same phenomenon as time 0 to t0.

  An inflection point is seen in the voltage at times 2t0 to 3t0. This is because the temperature in the food storage space increased and the humidity decreased because the front door of the refrigerator was opened (time 2t0 to tc) at time tc. However, when the door is closed again (time tc to 3t0), the humidity increases, and the voltage for maintaining the current value decreases. Thereafter, the same change in current value and voltage as in time 0 to 2t0 is observed again in time 3 to 5to.

  As described above, by using the oxygen concentration control method of the present embodiment, application of an excessively large voltage to the oxygen concentration adjusting means is avoided, and the maximum current is allowed to flow below an allowable voltage, and the efficiency of oxygen concentration adjustment. The effect that can be maximized is obtained.

  As described above, if the oxygen concentration control method of the present invention is used, low-cost, high-efficiency and long-term durability can be secured, and high-quality preservation of vegetables, meat, etc. can be performed in a safe state. Regardless of business use or home use, it can be applied to a storage such as a refrigerator for storing food, and a storage such as a refrigerator for storing chemicals, medical materials and chemicals sensitive to oxygen concentration.

Sectional drawing which showed the food storage space which can adjust the oxygen concentration in the refrigerator in Embodiment 1, 2, 3 of this invention The figure which showed the procedure of the oxygen concentration adjustment in Embodiment 1, 2 of this invention Sectional drawing of the oxygen concentration adjusting means in Embodiment 1, 2, and 3 of this invention The figure which showed the procedure of the oxygen concentration adjustment in Embodiment 3 of this invention The figure which showed the operation procedure of the oxygen concentration adjustment means off judgment block in Embodiment 3 of this invention The figure which showed the operation procedure of the electric current value control block in Embodiment 3 of this invention The figure which showed the relationship between the electric current value which flows into an oxygen concentration adjustment means, and the voltage applied to an oxygen concentration adjustment means

DESCRIPTION OF SYMBOLS 1 Storage chamber door 2 Heat insulation partition wall 3 Main body heat insulation wall 4 Partition plate 5 Oxygen concentration adjustment means 6 Deoxygenation auxiliary container 7 Food preservation container 8 Food preservation space 9 Frame 10 Polymer solid electrolyte membrane 11 Cathode 12 Anode 13 Supply electrode

Claims (4)

A storage having an oxygen concentration adjusting means including an ion conductive solid polymer electrolyte membrane sandwiched between an anode and a cathode, and a food storage space capable of adjusting the oxygen concentration by using the oxygen concentration adjusting means. In the method for controlling oxygen concentration in the food storage space,
Applying a voltage between the anode and the cathode to pass a current through the oxygen concentration adjusting means, calculating a deoxygenation amount from an integral value of the current, and an initial oxygen amount in a space leading to the food storage space; A method for controlling oxygen concentration in a food storage space, wherein a stop time of the oxygen concentration adjusting means is determined from the amount of deoxygenation. The food storage space oxygen concentration control method according to claim 1, wherein the current flowing through the oxygen concentration adjusting means is controlled at a constant current. 3. When the current flowing through the oxygen concentration adjusting means is subjected to constant current control, if the voltage applied to the oxygen concentration adjusting means exceeds an allowable maximum value, the current value for the constant current control is lowered. The oxygen concentration control method of the food storage space as described. 3. The current value for the constant current control is increased when the voltage applied to the oxygen concentration adjusting means falls below an allowable maximum value during constant current control of the current flowing through the oxygen concentration adjusting means. 4. The method for controlling oxygen concentration in a food storage space according to 3.