EP3327377A1

EP3327377A1 - Refrigerator

Info

Publication number: EP3327377A1
Application number: EP16827426.4A
Authority: EP
Inventors: Kei Nambu; Kiyoshi Mori; Kenichi Kakita; Toyoshi Kamisako
Original assignee: Panasonic Intellectual Property Management Co Ltd
Current assignee: Panasonic Intellectual Property Management Co Ltd
Priority date: 2015-07-17
Filing date: 2016-07-14
Publication date: 2018-05-30
Also published as: WO2017013859A1; CN107850366A; EP3327377A4

Abstract

A refrigerator includes: accommodating compartment (107); a cooler; an air blower for blowing cool air to accommodating compartment (107); and a controller for controlling the air blower, wherein the controller is configured to slightly freeze surfaces of foods preserved in accommodating compartment (107) and to control blowing of the cool air to accommodating compartment (107) so as to preserve the foods at a slightly freezing temperature.

Description

TECHNICAL FIELD

The present invention relates to a refrigerator which can preserve foods while keeping freshness of the foods.

BACKGROUND ART

Recently, on the background of social trends such as an increase of double-income households and aging of society, a frequency of food shopping has been decreasing, and a percentage of foods which will not be eaten immediately but preserved at home has been increasing. On the other hand, a demand for eating tasty foods having high freshness has not changed. Eventually, a demand for enhancing a freshness keeping performance of a household refrigerator has increased.
As factors in food deterioration, spoilage due to increase of microorganisms, self-decomposition due to enzymes in food and oxidation of food are mainly considered. A conventional household refrigerator has been required to satisfy a request to slow down, by low-temperature preservation, a speed of deterioration due to the above-mentioned three factors. However, when foods are preserved by freezing (-18°C or below), there arises a drawback that it is necessary to thaw the foods for taking out a part of food before cooking. In view of the above, a new temperature zone which is an intermediate temperature zone between a refrigerating temperature (4°C) and a freezing temperature has been used in preservation of foods for a relatively short period. Particularly, in preservation at a partial freezing temperature (-1°C to -5°C), only an extracellular fluid is frozen. Accordingly, the preservation performance acquired by the preservation at a temperature lower than a temperature (1°C to 4°C) for chilled preservation and the easiness in taking out a part of food can be acquired simultaneously. However, with respect to the preservation for fresh fish and meat containing a relatively large amount of fat, it cannot be said that deterioration due to oxidation of fat can be completely suppressed.
One method of fundamentally preventing oxidation of fat includes glazing used in the distribution industry. Glazing is a technique for forming a glaze on a surface of a food in order to prevent the food from being brought into contact with oxygen. More specifically, glazing is a technique for forming an ice layer having a thickness of approximately 1 mm on an outer side of a food by spraying low-temperature water onto a surface of the food which is frozen once and by freezing the food again. To realize the glazing in a household refrigerator, there has been known a technique in which a food is immersed in an immersion tank provided in a refrigerator, and the food is frozen after water is adhered to a surface of the food (for example, PTL 1).
However, in PTL 1, when foods are frozen in a state where a user places foods at random, glazes become fixed to each other by freezing thus giving rise to a drawback that it takes time and effort to divide food at the time of taking out the food. Further, additional time and effort such as periodical cleaning of the immersion tank become necessary. In addition, a drawback that a food tastes watery due to the adhesion of water occurs. Accordingly, foods to which the technique disclosed in PTL 1 can be applied are limited.
In the technique disclosed in PTL 1, it is necessary for a user to perform such an operation by himself thus giving rise to a drawback that it takes a great time and effort for performing such an operation.

Citation List

Patent Literature

PTL 1: Unexamined Japanese Patent Publication No. 3-170765

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a refrigerator which can prevent oxidation of foods by preventing contact between foods and oxygen without causing adhering together of the foods and lowering flavor of foods. Further, it is also an object of the present invention to provide a refrigerator which can keep freshness of food quickly and reliably by determining the presence or absence of an input food in an accommodating compartment with a simple specification.
More specifically, a refrigerator according to one example of an exemplary embodiment of the present invention includes: an accommodating compartment; a cooler for generating cool air; an air blower for blowing cool air from the cooler to the accommodating compartment; and a controller for controlling the air blower. The controller is configured to slightly freeze surfaces of foods preserved in the accommodating compartment and to control blowing of the cool air to the accommodating compartment so as to preserve the foods at a slightly freezing temperature.
With such a configuration, oxidation of foods can be prevented by interrupting contact between foods and oxygen due to formation of slightly frozen layer and, at the same time, dividing and cutting of foods can be easily performed, and foods to be preserved can be preserved while keeping freshness without deteriorating flavor of foods.
In the refrigerator according to one example of the exemplary embodiment of the present invention, the air blower may include: a duct for blowing the cool air from the cooler to the accommodating compartment; a damper device which is disposed in the duct; and a temperature sensor which detects a temperature in the accommodating compartment. In this case, the controller is configured to forcibly open the damper device for a predetermined time so that the surfaces of foods preserved in the accommodating compartment are quickly slightly frozen and to control opening and closing of the damper device based on a temperature detected by the temperature sensor such that the foods whose surfaces are slightly frozen are preserved at the slightly freezing temperature. With such a configuration, rapid cooling is started immediately after foods are put into the refrigerator and hence, contact between the foods and oxygen can be interrupted in a shorter time thus preventing oxidation of the foods.
In the refrigerator according to one example of the exemplary embodiment of the present invention, the controller may be configured to forcibly open the damper device for a predetermined time and to continuously operate the compressor. With such a configuration, surfaces of foods can be quickly slightly frozen and hence, contact between foods and oxygen can be interrupted in a short time thus preventing oxidation of the foods.
The refrigerator according to one example of the exemplary embodiment of the present invention may further include an accommodating compartment opening and closing detection part which detects an open and close state of the accommodating compartment, wherein the controller is configured to execute a control of the refrigerator in response to the detection of an open and close state of the accommodating compartment by the accommodating compartment opening and closing detection part. With such a configuration, an input operation of a food by a user can be detected in a shorter time and hence, a contact time between the food and oxygen can be shortened thus preventing oxidation of the food.
The refrigerator according to one example of the exemplary embodiment of the present invention may be configured such that the accommodating compartment is incorporated at a corner of a storage compartment, and a temperature in the accommodating compartment is controlled independently from a temperature in the storage compartment. With such a configuration, a slightly frozen layer which is once formed on a food is maintained in a stable manner thus maintaining an antioxidation effect. Further, a fluctuation in temperature in the accommodating compartment can be reduced and hence, freshness keeping performance of keeping freshness of preserved foods can be enhanced.
The refrigerator according to one example of the exemplary embodiment of the present invention may further include: an accommodating compartment opening and closing detection part which detects an open and close state of the accommodating compartment; and a food put-in determination part which determines presence or absence of an input food in the accommodating compartment. In this case, the food put-in determination part is configured to make the controller forcibly stop the blowing of air by the air blower for a predetermined time and to determine the presence or absence of an input food in the accommodating compartment based on a temperature detected by the temperature sensor (a gradient of a graph of a detected temperature). With such a configuration, the determination of the presence or absence of the input food in the accommodating compartment can be performed with a simple specification.
The refrigerator according to one example of the exemplary embodiment of the present invention may further include: a food put-in determination part which determines whether or not a food has been put into the accommodating compartment. In this case, after the food put-in determination part makes the controller forcibly stop blowing of cool air by the air blower for a predetermined time, and makes the controller forcibly operate the air blower for a predetermined time thus determining the presence or absence of the input food in the accommodating compartment based on a temperature detected by the temperature sensor (a gradient of a graph of a detected temperature) during a period in which the air blower is forcibly operated. With such a configuration, the determination of the presence or absence of input food in the accommodating compartment can be performed reliably with a simple specification.
The refrigerator according to one example of the exemplary embodiment of the present invention may be configured such that the determination of whether a food has been put into the accommodating compartment is performed by executing the determination by the food put-in determination part a plurality of times. With such a configuration, the determination of the presence or absence of the input food in the accommodating compartment can be performed more reliably with a simple specification.
The refrigerator according to one example of the exemplary embodiment of the present invention may further include: an accommodating compartment opening and closing detection part which detects opening or closing of the accommodating compartment ; and a food put-in determination part which determines presence or absence of an input food in the accommodating compartment, wherein the food put-in determination part may be configured to perform determination of the presence or absence of the input food in the accommodating compartment in response to detection of an open and close state of the accommodating compartment by the accommodating compartment opening and closing detection part. With such a configuration, the determination of the presence or absence of the input food can be performed more reliably.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view of a refrigerator according to a first exemplary embodiment of the present invention.
FIG. 2 is a cross-sectional view of the refrigerator according to the first exemplary embodiment of the present invention taken along line 2-2 in FIG. 1.
FIG. 3 is an enlarged view of a main part of a refrigerating compartment according to the first exemplary embodiment of the present invention.
FIG. 4 is a control block diagram for a control of the refrigerator according to the first exemplary embodiment of the present invention.
FIG. 5 is a flowchart for a control of the refrigerator according to the first exemplary embodiment of the present invention ranging from a detection of an input load to a rapid cooling operation.
FIG. 6 is a sequence chart for detection of an input load of the refrigerator according to the first exemplary embodiment of the present invention.
FIG. 7 is a sequence chart for a rapid cooling operation of the refrigerator according to the first exemplary embodiment of the present invention.
FIG. 8 is a view showing the relationship between a slightly freezing start time and a POV value after a lapse of three days of the refrigerator according to the first exemplary embodiment of the present invention.
FIG. 9A is a view showing the relationship between a temperature gradient ΔT and a rotational speed of a compressor at the time of performing first rapid cooling in the refrigerator according to a second exemplary embodiment of the present invention.
FIG. 9B is a view showing the relationship between a temperature gradient ΔT and an operation time at the time of performing second rapid cooling in the refrigerator according to the second exemplary embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Exemplary embodiments according to the present invention are hereinafter described with reference to the drawings. The present invention is not limited by the exemplary embodiments.

(First exemplary embodiment)

FIG. 1 is a front view of a refrigerator according to a first exemplary embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1, and FIG. 3 is an enlarged view of a main part of the refrigerating compartment according to the first exemplary embodiment of the present invention. FIG. 4 is a block diagram for a control of the refrigerator according to the exemplary embodiment of the present invention, and FIG. 5 is a control flowchart for a control of the refrigerator according to the first exemplary embodiment of the present invention ranging from a detection of an input load to a rapid cooling operation.
In FIG. 1 and FIG. 2, refrigerator 101 includes a storage compartment, and an inside of the storage compartment is divided into an upper stage, an intermediate stage, and a lower stage. More specifically, the storage compartment includes, on the upper stage, refrigerating compartment 102 including a double-hinged-type door (refrigerating compartment door 102a) on a front surface of the storage compartment. The storage compartment also includes, below refrigerating compartment 102, first freezing compartment 103 including a drawer door and ice-making compartment 105 disposed parallel to first freezing compartment 103 laterally and including a drawer door. The storage compartment includes: vegetable compartment 106 disposed on a lowermost portion of the storage compartment and including a drawer door; and second freezing compartment 104 disposed between ice-making compartment 105 and vegetable compartment 106.
Refrigerator 101 includes refrigerating compartment door 102a, first freezing compartment door 103a, second freezing compartment door 104a, ice-making compartment door 105a, and vegetable compartment door 106a. Refrigerating compartment 102, and ice-making compartment 105 and first freezing compartment 103 are vertically divided by heat insulating partition wall 111. In the same manner, ice-making compartment 105 and first freezing compartment 103 which are disposed parallel to each other laterally and second freezing compartment 104 are vertically divided by heat insulating partition wall 111. Further, second freezing compartment 104 and vegetable compartment 106 are also vertically divided by heat insulating partition wall 111 in the same manner.
Refrigerator 101 has heat insulating wall 110 which is filled between outer box 108 and inner box 109. In refrigerator 101, temperature changeable compartment 107 is defined as an independent storage compartment in a lower portion of the inside of refrigerating compartment 102 disposed on the upper stage of refrigerator 101. Temperature changeable compartment 107 is configured as a switching compartment. For example, in this exemplary embodiment, temperature changeable compartment 107 is configured such that a set temperature can be switched between a first temperature zone (chilled) which is a refrigerating temperature zone near 0°C, and a second temperature zone (partial freezing) of approximately -3°C which is a temperature zone between the first temperature zone and a freezing temperature zone of approximately -6°C or below.
Next, a configuration of a cooling system is described. Cooling compartment 114 is formed behind a back surface of second freezing compartment 104, and cooler 115 is disposed inside cooling compartment 114. Cooler 115 constitutes a refrigeration cycle for cooling refrigerator 101 in cooperation with compressor 112 provided to machine compartment 113 disposed on an upper portion of refrigerator 101. Air blowing fan 116 is disposed in cooling compartment 114 for forcibly circulating cool air produced by heat exchange in cooler 115. Damper device 117 is disposed above air blowing fan 116. Damper device 117 includes damper device 117a which distributes cool air flowing into refrigerating compartment 102, and damper device 117b which distributes cool air flowing into temperature changeable compartment 107. The storage compartments are configured to be used such that temperature zones of the storage compartments are set different from each other. More specifically, for example, an indoor temperature of refrigerating compartment 102 is set to a temperature zone ranging from approximately 2°C to 3°C, an indoor temperature of vegetable compartment 106 is set to a temperature zone ranging from approximately 2°C to 5°C, and indoor temperatures of first freezing compartment 103 and second freezing compartment 104 are set to a temperature zone ranging from approximately -18°C to -20°C. That is, the respective storage compartments can be used in a divided manner with respect to temperature zones. With such a configuration, a temperature zone suitable for the preservation of food can be selected, and the food can be stored at a temperature suitable for the preservation of the food. Accordingly, it is possible to realize higher freshness keeping performance and long period preservation.
Next, a configuration of temperature changeable compartment 107 and a configuration of illumination device 121 which is mounted on a ceiling surface of temperature changeable compartment 107 are described with reference to FIG. 3 and FIG. 4. Temperature changeable compartment 107 is configured as follows. An upper portion of temperature changeable compartment 107 is constituted of synthetic-resin upper surface cover 122 which is utilized also as shelf plate 118 positioned at the lowermost stage of refrigerating compartment 102. A lower side of upper surface cover 122 is constituted of synthetic-resin accommodating case 123 which is accommodated in temperature changeable compartment 107 in a state where accommodating case 123 can be pulled out in a longitudinal direction; and opening and closing door 124 which is disposed on an opening on a front surface of upper surface cover 122 of temperature changeable compartment 107 in an openable manner. Opening and closing door 124 is configured such that, during a closed time, opening and closing door 124 is brought into close contact with front surface wall 123b of accommodating case 123 so that an inside of temperature changeable compartment 107 is brought into a substantially hermetically sealed space. Opening and closing door 124 is made of a synthetic resin having high transparency such that a user can visually recognize foods accommodated in the inside of temperature changeable compartment 107.
Further, door opening and closing detection part 127 is mounted on a depth-side wall surface of temperature changeable compartment 107 such that door opening and closing detection part 127 is engaged with rear surface wall 123a of accommodating case 123 when opening and closing door 124 is closed. In this exemplary embodiment, aluminum bottom plate 128 is fitted in a bottom surface of accommodating case 123 thus realizing the enhancement of cooling performance and the enhancement of visibility due to diffusion of illumination light from illumination device 121. Aluminum bottom plate 128 is not particularly necessary.
Behind the depth-side wall surface of temperature changeable compartment 107, temperature changeable compartment back surface duct 125 which guides cool air distributed by damper device 117b to temperature changeable compartment 107 is formed. On the ceiling surface of temperature changeable compartment 107, temperature changeable compartment ceiling surface duct 126 is disposed on a downstream side of temperature changeable compartment back surface duct 125. Temperature changeable compartment ceiling surface duct 126 includes: heat insulating duct member 126a which is formed of a foamed heat insulating member having heat insulation property; and synthetic-resin duct cover 126b which covers an outer periphery of heat insulating duct member 126a and forms an ornamental plate. The duct cover 126b forms the duct in cooperation with upper surface cover 122. Cool air blow-off port 129 which discharges cool air into the inside of temperature changeable compartment 107 is formed on an upper side which faces accommodating case 123. The air blower includes at least: the ducts for blowing cool air from the cooler to the accommodating compartment (refrigerating compartment duct 120, temperature changeable compartment back surface duct 125, and temperature changeable compartment ceiling surface duct 126); the dampers disposed in the ducts (damper device 117a, damper device 117b); and the temperature sensor which detects a temperature in the accommodating compartment (temperature changeable compartment temperature sensor 133).
Inside temperature changeable compartment 107, illumination device 121 which illuminates the inside of temperature changeable compartment 107 is disposed. The illumination device 121 is disposed on a front opening and closing door side in front of a depth-side center position of temperature changeable compartment ceiling surface duct 126 in a state where illumination device 121 is embedded in duct cover 126b.
Next, refrigerating compartment door switch 130 which detects an open and closed state of refrigerating compartment door 102a is disposed in refrigerating compartment 102. At an arbitrary place outside or inside refrigerator 101, setting part 131 which switches a temperature zone and an operation mode of temperature changeable compartment 107 is disposed. Signal S1 is input to controller 132 from refrigerating compartment door switch 130, signal S2 is input to controller 132 from setting part 131, and signal S3 is input to controller 132 from door opening and closing detection part 127. Further, from controller 132, signal S4 is inputted to compressor 112, signal S5 is inputted to air blowing fan 116, signal S6 is inputted to damper device 117a, and signal S7 is inputted to damper device 117b respectively so that a predetermined cooling operation is performed.
Hereinafter, the manner of operation and effects of refrigerator 101 having the above-mentioned configuration are described with reference to FIG. 5 to FIG. 7.
First, in a state where a temperature zone of temperature changeable compartment 107 is set to the second temperature zone (partial freezing (PF)) by setting part 131, when opening and closing door 124 is closed, refrigerating compartment door switch 130 detects closing of refrigerating compartment door 102a (STEP 1). In response to the detection of closing of refrigerating compartment door 102a by refrigerating compartment door switch 130 (STEP 1), the presence or absence of an input load (food) is determined by food put-in determination part 134. More specifically, in a case where five minutes or more have passed after start of compressor 112 and compressor 112 is operated at a predetermined rotational speed which is set corresponding to an outside air temperature (STEP 2), the rapid cooling starting determination as to whether or not the inside of temperature changeable compartment 107 is rapidly cooled is started (STEP 3). In STEP 2, when five minutes have not passed after start of compressor 112, at a point of time that five minutes have passed, processing shifts to STEP 3.
In STEP 3, when it is determined that there is no load (input food is absent), a usual partial freezing control is performed (STEP 4). On the other hand, when it is determined that an input load is present in STEP 3, a predetermined rapid cooling operation is started. Although the rapid cooling operation is described in detail later, outline of the rapid cooling operation is as follows. That is, first rapid cooling in STEP 5 is performed and, thereafter, second rapid cooling in STEP 6 is performed. After the predetermined rapid cooling operation is finished, a deep freeze protecting operation in STEP 7 is performed.
Preferably, the rapid cooling canceling determination (STEP 8) in which the presence or absence of an input load is determined again is performed between the first rapid cooling in STEP 5 and the second rapid cooling in STEP 6. The rapid cooling canceling determination (STEP 8) is substantially equal to the rapid cooling starting determination performed for advancing STEP 2 to STEP 3 described later.
The rapid cooling canceling determination may be performed based on a gradient of a temperature detected by temperature changeable compartment temperature sensor 133 when damper device 117b for temperature changeable compartment (partial freezing compartment) 107 is forcibly closed for a predetermined time.
The sequence of food put-in determination part 134 relating to the rapid cooling starting determination for advancing STEP 2 to STEP 3 is described with reference to FIG. 6.
When the rapid cooling starting determination is started, damper device 117a for the refrigerating compartment is forcibly opened, damper device 117b for temperature changeable compartment (partial freezing compartment) 107 is forcibly closed. Compressor 112 is operated for three minutes while maintaining a predetermined rotational speed in a state where a flow rate of discharged cool air is set to a predetermined amount. After a lapse of three minutes, damper device 117a for the refrigerating compartment is forcibly closed, and damper device 117b for temperature changeable compartment (partial freezing compartment) 107 is forcibly opened. A temperature in temperature changeable compartment 107 after a lapse of four minutes from the start of input load detection sequence and a temperature in temperature changeable compartment 107 after a lapse of five minutes from the start of input load detection sequence are detected by temperature changeable compartment temperature sensor 133, and a temperature gradient ΔT is calculated (see FIG. 6). When a value of temperature gradient ΔT is larger than a predetermined threshold value which is set based on a partial freezing compartment temperature after a lapse of four minutes, it is determined that an input load is present, and the rapid cooling operation is started.
In the above-mentioned sequence, by stopping cooling of temperature changeable compartment 107 for three minutes from the start of the detection, a temperature changing state of temperature changeable compartment 107 can be made stable thus stabilizing a temperature gradient ΔT. Usually, during a partial freezing operation, a rotational speed of compressor 112, a quantity of discharged cool air, and an amount of load already accommodated in temperature changeable compartment 107 are not fixed. Further, an indoor temperature is always in a rising or lowering state. Even when these conditions become different immediately before the detection, the determination should be made based on a fixed threshold value. By continuing an operation under the above-mentioned predetermined conditions for three minutes prior to the start of cooling of temperature changeable compartment 107, a value of temperature gradient ΔT can mainly reflect an input thermal load. As a result, regardless of an operation state immediately before the detection, accurate determination can be made in a stable manner.
In addition, by starting cooling after raising a temperature in temperature changeable compartment 107 in a first-half three minutes, an absolute value of a temperature gradient ΔT can be increased compared to a case where the cooling is started immediately. Due to such an increase of the absolute value of temperature gradient ΔT, a value of temperature gradient ΔT and an S/N ratio of measurement irregularities of temperature changeable compartment temperature sensor 133 are increased thus eventually enhancing accuracy of the determination based on a value of temperature gradient ΔT.
Further, by forcibly cooling refrigerating compartment 102 in a concentrated manner in first-half three minutes, a temperature of refrigerating compartment 102 is lowered compared to a usual operation time. Accordingly, when a temperature of refrigerating compartment 102 is adjusted again, damper device 117a is closed for a longer time compared to a usual case. As described later, to increase a speed of slight freezing of a surface layer of a food, it is important that a state where damper device 117a is closed and only damper device 117b is opened is continued after start of rapid cooling. The above-mentioned preliminary cooling of refrigerating compartment 102 has an effect of extending a continuous opening time of damper device 117b thus accelerating slight freezing of a surface layer of a food.
After a lapse of three minutes from the start of input load detection sequence, damper device 117a is closed and damper device 117b is opened. Accordingly, temperature changeable compartment 107 is cooled at a maximum cooling speed. A temperature gradient may be influenced depending on an opening and closing timing immediately after the damper devices are opened or closed. Accordingly, the determination is performed using a value of stable temperature gradient ΔT which is a temperature gradient obtained after four to five minutes from the finish of the opening and closing operation as an index.
Compared to a case where there is no input thermal load in temperature changeable compartment 107 (indicated by symbol b in FIG. 6), in a case where a certain large amount of thermal load is put in the temperature changeable compartment 107, the lowering of an indoor temperature detected by temperature changeable compartment temperature sensor 133 becomes slow (indicated by symbol a in FIG. 6), and a value of temperature gradient ΔT becomes small.
A threshold value of temperature gradient ΔT is set in a variable manner in accordance with the following various conditions. When an indoor temperature after a lapse of three minutes is relatively high, a temperature is likely to be lowered in a cooling operation during second-half two minutes. Accordingly, an absolute value of a threshold value of temperature gradient ΔT is set to a relatively large value. On the other hand, when an indoor temperature after a lapse of three minutes is relatively low, an absolute value of a threshold value of temperature gradient ΔT is set to a relatively small value. When an outside air temperature is relatively high, cooling performance during second-half two minutes is likely to become relatively low. Accordingly, an absolute value of a threshold value of temperature gradient ΔT is set to a relatively small value. When a rotational speed of compressor 112 is relatively high, cooling performance becomes relatively high. Accordingly, an absolute value of a threshold value of temperature gradient ΔT is set to a relatively large value.
In determining the presence or the absence of an input thermal load in accordance with the detection sequence, particularly when a value of a temperature gradient ΔT is close to a threshold value, whether or not the determination can be accurately made is decided probabilistically in accordance with a normal distribution. The erroneous determination includes a first erroneous determination of determining that there is no input thermal load even though an input thermal load is present (it is not necessary to perform rapid cooling) and an erroneous determination of determining that an input thermal load is present even though there is no input thermal load (it is necessary to perform rapid cooling). A threshold value of temperature gradient ΔT may be set such that a probability of the first erroneous determination is equal to a probability of the second erroneous determination. When it makes sense to rapidly and reliably cool an input thermal load in use, to minimize a probability of the first erroneous determination, a threshold value of a temperature gradient ΔT is set to a large value compared to the above-mentioned case where probabilities of the first and second erroneous determinations are equal. On the other hand, it may be considered disadvantageous to excessively cool an object to be cooled which is already cooled inside temperature changeable compartment 107. In such a case, a threshold value of temperature gradient ΔT may be set small as compared to the above-mentioned case, to minimize a probability of the second erroneous determination where the probabilities of the first and second erroneous determinations are equal.
To increase a probability of accurate determination, it is effective to set an amount of intrusion of heat into temperature changeable compartment 107 from the wall surface to a fixed value. When temperature changeable compartment 107 is disposed in refrigerating compartment 102, regardless of a change in outside air temperature, a change in temperature of refrigerating compartment 102 falls within a predetermined range. Accordingly, an amount of intrusion of heat can be easily set to a fixed value, and it is effective for enhancing determination accuracy.
In the case where a temperature in temperature changeable compartment 107 becomes a predetermined temperature or more and opening and closing door 124 is opened for a predetermined time or more, rapid cooling described later or cooling by a usual partial freezing operation may be started without using the detection sequence shown in FIG. 6. As a result, a partial freezing compartment temperature can be quickly lowered without taking time for a detection operation. Accordingly, it is possible to prevent the lowering of freshness due to a rise of a food temperature.
Next, a rapid cooling sequence shown in FIG. 7 is described. The rapid cooling operation is performed by first rapid cooling in which a cooling performance is relatively large and second rapid cooling in which a cooling performance is larger than that of a usual partial freezing operation and smaller than that of the first rapid cooling. An operation condition at the time of performing the first rapid cooling is described hereinafter. That is, a rotational speed of compressor 112 is set higher as compared to a rotational speed of compressor 112 in the usual operation time. That is, the rotational speed of compressor 112 is set such that an amount of cool air introduced to temperature changeable compartment 107 is increased. In the first rapid cooling operation time, damper device 117b for temperature changeable compartment 107 is forcibly set to an open state, damper device 117a for refrigerating compartment 102 is set such that opening of damper device 117a is more difficult, and compressor 112 is set to be operated without being stopped.
In the second rapid cooling operation time, by adjusting a temperature in temperature changeable compartment 107, it is possible to prevent a food from being cooled to a predetermined temperature or below. The second rapid cooling is operated under any one of the above-mentioned operation conditions at the time of performing the first rapid cooling operation. Alternatively, the second rapid cooling may be operated under a condition between an operation condition at the time of performing the first rapid cooling operation and an operation condition at the time of performing a usual operation.
The first rapid cooling having large cooling performance has an effect of accelerating slight freezing of a food. On the other hand, when the first rapid cooling is continued, temperature changeable compartment 107 having a limited capacity is mainly cooled and hence, cold heat in evaporator 115 is not completely emitted to the indoor so that a temperature of evaporator 115 is likely to be continuously lowered. As a result, an operation of compressor 112 must be stopped for protecting compressor 112 from low pressure. As described later, to accelerate slight freezing, it is indispensable to continue the cooling in a sequential manner. Accordingly, it is necessary to prevent a temperature of evaporator 115 from becoming lower than a predetermined temperature. Accordingly, the first rapid cooling is finished in thirty minutes, for example, and the second rapid cooling is started at a lower rotational speed. In the second rapid cooling, a rotational speed of compressor 112 is set such that the lowering of a temperature of evaporator 115 below a predetermined temperature is prevented even when compressor 112 is continuously operated. In the case where a temperature of the evaporator is lowered even when such an operation is performed, damper device 117a may be forcibly opened.
By providing the second rapid cooling which exhibits the lower cooling performance than the first rapid cooling, it is possible to acquire an effect of avoiding the occurrence of a phenomenon that a food which is already slightly frozen in temperature changeable compartment 107 is made hard by deep freezing, a phenomenon that frost is formed in temperature changeable compartment 107, and a phenomenon that a food placed adjacently to temperature changeable compartment 107 is unexpectedly slightly frozen and the like.
To rapidly and reliably realizing slight freezing of a food, it is necessary to continuously cool the food for a predetermined time due to the following reason. That is, in a case where a food is slightly frozen, when a surface layer of the food is slightly frozen, a specific heat on the surface layer of the food becomes approximately a half of a specific heat of a unfrozen portion in the inside of the food, and a thermal conductivity on the surface layer of the food becomes approximately four times as large as a thermal conductivity in the unfrozen portion. When the cooling is temporarily stopped in such a situation, heat of the unfrozen portion is easily transferred to the slightly frozen portion by heat conduction and hence, a temperature of the slightly frozen portion is easily increased again. As a result, a temperature of a portion which is temporarily slightly frozen is easily increased to 0°C, and melting is started. The repetition of slight freezing and melting physically deteriorates a food and lowers a quality of the food and hence, the repetition of slight freezing and melting is not preferable.
To realize slight freezing of a surface layer rapidly and reliably, it is necessary to make the slightly frozen layer exhibit a heat insulating effect in such a manner that a slightly frozen layer is made to grow to have a thickness of approximately 1 mm so that the slightly frozen layer itself exhibits a latent heat accumulating effect thus preventing heat inside the food from being transferred to an outermost layer. Accordingly, by making the slightly frozen layer grow to have a fixed thickness, the slightly frozen layer can be reliably formed on a surface layer of a food. A time required for generating a slightly frozen layer is hardly influenced by a super cooling phenomenon so that the time is relatively stable.
Foods such as meat and fish contain phospholipid in cell membranes, and contain neutral lipid in subcutaneous tissues. However, an unsaturated fatty acid which is a constitutional element of the phospholipid and the neutral lipid is automatically oxidized by being brought into contact with oxygen thus generating hydroxyperoxide. It is said that when a human eats hydroxyperoxide, hydroxyperoxide works as a harmful substance because DNA is damaged due to a radical reaction in a human body and a physiologically active substance is oxidized.
In this respect, when a slightly frozen layer is uniformly formed on a surface layer of a food by the above-mentioned rapid cooling, an ice in an extracellular fluid exhibits a diffusion coefficient of oxygen smaller than that of water by two or more digits. Accordingly, it is possible to substantially interrupt cells and the inside of a food from oxygen. Oxygen is indispensable for the above-mentioned autoxidation and hence, the generation of hydroxyperoxide can be prevented. In this manner, by accelerating slight freezing of the surface layer, oxidation of a food containing fat can be suppressed. That is, by suppressing the increase of values such as AV (Acid Value), POV (Peroxide Value), and TBA (Thiobarbituric Acid) which are oxidation indexes, the suppression of oxidation can be confirmed.
FIG. 8 is a view showing the relationship between a POV value of a surface layer freezing time at the time of freezing a food and a POV value after a lapse of three days. In FIG. 8, a POV value taken on a vertical axis is indicated in a relativized manner by setting a POV value in a 0th day as 1.0. From FIG. 8, it is found that, with respect to two kinds of fish foods, when a surface layer freezing time exceeds a predetermined time, an oxidation index value is increased during three preservation days. It is also found that, to suppress the increase of a POV value during three days thus substantially stopping oxidation, it is effective to slightly freeze a surface of a food within eight hours so as to interrupt contact between oxygen and fat.
In the same manner, it is also found that when the surface layer is slightly frozen within eight hours, a K value (an index indicative of freshness) is not increased during three days. In addition, in a case of beef and pork, it is found that when a surface layer slight freezing is performed within eight hours, an oxidation index value after a lapse of seven days is not increased. In this exemplary embodiment, cooling performance at the time of rapid cooling operation is set such that a surface of a food is slightly frozen within eight hours.
In the midst of the first rapid cooling, a rapid cooling canceling determination may be performed in which a continuation of the rapid cooling operation is determined again. The rapid cooling canceling determination is basically equal to the detection sequence shown in FIG. 6. However, a threshold value of temperature gradient ΔT is decided separately. The rapid cooling canceling determination may be performed a plurality of times. Even when the second erroneous determination is performed in accordance with the detection sequence, by performing the rapid cooling canceling determination, the rapid cooling operation can be stopped in the midst of operation. Accordingly, unnecessary rapid cooling can be stopped thus preventing the energy consumption from being excessively increased.
When the second rapid cooling is finished, an operation mode returns to the usual partial freezing operation. When a temperature of cooler 115 is lower than a predetermined temperature at the time of shifting the operation mode to the usual partial freezing operation mode, there may be a case where it is determined that cooling is unnecessary so that compressor 112 is stopped. Usually, while compressor 112 is stopped, air blowing fan 116 for blowing cool air of evaporator 115 into the refrigerator is stopped. However, during shifting of an operation mode, the fan may be operated. With such an operation, the increase of a temperature of evaporator 115 can be accelerated thus shortening a stop time of compressor 112 compared to a usual time. As a stop time of compressor 112 is shorter, a time until the slight freezing can be achieved becomes shorter due to the above-mentioned reasons. Accordingly, it is possible to acquire a desirable result in terms of keeping freshness.
After an operation mode returns to a usual operation, as shown in FIG. 7, a protection time is provided for a predetermined time in which the rapid cooling is not started and the usual partial freezing operation is performed. When a food which is slightly frozen exists in temperature changeable compartment 107 before a thermal load is put in temperature changeable compartment 107, a temperature of the food may be temporarily lowered due to rapid cooling operation, and the food may be further hardened from a slightly frozen state. By providing the protection time, a temperature of the food approaches a temperature at the time of performing the usual partial freezing operation during the protection time so that a hardness of the food is also returned to a desired hardness. When the projection time is not provided and a thermal load is continuously put into temperature changeable compartment 107, a state of an existing slightly frozen food approaches a frozen state from a slightly frozen state thus giving rise to a drawback such as the decrease of advantageous effects of slight freezing or the like. However, the present invention can prevent the occurrence of such a drawback.
As the above-mentioned protection time becomes longer, a temperature of an existing slightly frozen food is reliably and easily returned to a slightly freezing temperature. A length of the protection time is set such that a temperature in temperature changeable compartment 107 falls within a range of slightly freezing temperature zone during a standard preservation period of a food by taking into account the increase of a temperature during protection time and the increase of a temperature during a defrost operation which is periodically performed. Alternatively, the length of the protection time may be set such that a force for cutting a food is not increased to a predetermined value or more during a standard preservation period of the food.
As one example, FIG. 7 shows an example where a rapid cooling operation time is set to 2.5 hours, and a protection time is set to 3 hours. In this case, one rapid cooling cycle is 5.5 hours, and this cycle is substantially equal to a time cycle for preparing breakfast, lunch, or dinner in general. Accordingly, even when a rapid cooling operation is started with the increase of a partial freezing compartment temperature at a certain meal preparation time, rapid cooling can be performed at a next meal preparation time in the same manner. Accordingly, freshness of an existing slightly frozen food can be reliably kept.
When a thermal load is input in temperature changeable compartment 107 during the protection time, the determination of rapid cooling is performed by operating only the detection sequence. When it is determined that rapid cooling is necessary, rapid cooling is performed immediately after the protection time is finished.
As described above, refrigerator 101 according to this exemplary embodiment includes: accommodating compartment (temperature changeable compartment 107); the air blower for blowing cool air from cooler 115 to the accommodating compartment; and controller 132 for controlling the air blower. In refrigerator 101 of this exemplary embodiment, controller 132 is configured to slightly freeze surfaces of foods preserved in the accommodating compartment, and to control blowing of cool air to the accommodating compartment so as to preserve the foods having slightly frozen surfaces at a slightly freezing temperature. With such a configuration, contact between a food and oxygen can be interrupted by the slightly frozen layer thus preventing oxidation of the food. Further, dividing and cutting of a food can be easily performed, and flavor of the food is not deteriorated and hence, a preserved food can be preserved while keeping freshness of the food.
In refrigerator 101 of this exemplary embodiment, the air blower may include the ducts for blowing cool air from the cooler to the accommodating compartment (refrigerating compartment duct 120, temperature changeable compartment back surface duct 125, and temperature changeable compartment ceiling surface duct 126), the dampers disposed in the ducts (damper device 117a, damper device 117b), and the temperature sensor which detects a temperature in the accommodating compartment (temperature changeable temperature sensor 133). Further, the controller is configured to control blowing of cooling air or the like such that the damper device is forcibly opened for a predetermined time so that surfaces of foods preserved in the accommodating compartment are rapidly slightly frozen and, thereafter, opening and closing of the damper device is controlled based on a temperature detected by the temperature sensor such that foods having surfaces thereof slightly frozen are preserved at a slightly freezing temperature. With such a configuration, by starting the rapid cooling immediately after a food is put into the temperature changeable compartment, contact between the food and oxygen can be interrupted in a shorter time thus preventing oxidation of the food. Accordingly, the food can be preserved while further keeping freshness of the food.
Refrigerator 101 according to this exemplary embodiment may be configured such that the damper device is forcibly opened for a predetermined time and, at the same time, the compressor is continuously operated. With such a configuration, the contact between the food and oxygen can be interrupted in a shorter time thus preventing oxidation of the food. Accordingly, the food can be preserved while further keeping freshness of the food.
Refrigerator 101 of this exemplary embodiment may include: the accommodating compartment; the air blower for blowing cool air from cooler 115 to the accommodating compartment; temperature sensor 133 which detects a temperature in the accommodating compartment; and food put-in determination part 134 which determines the presence or absence of an input food in the accommodating compartment. In this case, food put-in determination part 134 forcibly stops the air blower for a predetermined time using controller 132, and determines the presence or absence of an input food in the accommodating compartment based on a gradient of a temperature in the accommodating compartment detected by temperature sensor 133. With such a configuration, the determination of the presence or absence of the input food in the accommodating compartment can be performed with a simple specification.
Food put-in determination part 134 may be configured such that after the air blower is forcibly stopped for a predetermined time, the air blower is forcibly operated for a predetermined time, and food put-in determination part 134 determines the presence or absence of an input food in the accommodating compartment based on a gradient of a temperature detected by temperature sensor 133 during the period that the air blower is forcibly operated. With such a configuration, the determination of the presence or absence of input food in the accommodating compartment can be performed reliably with a simple specification.
The determination of the presence or absence of an input food in the accommodating compartment by food put-in determination part 134 may be performed a plurality of times. With such a configuration, the determination of the presence or absence of an input food in the accommodating compartment can be performed more reliably with a simple specification.
Refrigerator 101 of this exemplary embodiment may include accommodating compartment opening and closing detection part 127 which detects opening and closing of the accommodating compartment. With such a configuration, by operating controller 132 in response to the detection of an open and close state of the accommodating compartment by accommodating compartment opening and closing detection part 127, oxidation of a food can be prevented more reliably so that a preserved food can be preserved while keeping freshness of the food.
Refrigerator 101 of this exemplary embodiment may be configured such that the accommodating compartment is incorporated in a corner of the storage compartment, and a temperature in the accommodating compartment is controlled independently from a temperature in the storage compartment (refrigerating compartment 102). With such a configuration, a slightly frozen layer which is once formed on a food is maintained in a stable manner thus maintaining an antioxidation effect.
The refrigerator includes accommodating compartment opening and closing detection part 127 which detects the open and close state of the accommodating compartment. By operating controller 132 in response to the detection of an open and close state of the accommodating compartment by accommodating compartment opening and closing detection part 127, oxidation of a food can be prevented more reliably so that a preserved food can be preserved while keeping freshness of the food.

(Second exemplary embodiment)

FIG. 9A is a view showing the relationship between temperature gradient ΔT and a rotational speed of a compressor at the time of performing first rapid cooling in a refrigerator according to a second exemplary embodiment of the present invention, and FIG. 9B is a view showing the relationship between temperature gradient ΔT and an operation time of the compressor at the time of performing second rapid cooling in the refrigerator according to the second exemplary embodiment of the present invention. The description with respect to parts identical with the corresponding parts in the first exemplary embodiment is omitted, and only parts which make the second exemplary embodiment different from the first exemplary embodiment are described.
In the rapid cooling determination sequence shown in FIG. 6, a magnitude of a value of a temperature gradient ΔT is substantially proportional to an input thermal load under a fixed condition. In refrigerator 101 of this exemplary embodiment, an operation control is performed in which a cooling amount is increased in proportion to an amount of input thermal load. As in the case of first rapid cooling shown in FIG. 9A, rapid cooling is performed when an absolute value of temperature gradient ΔT is larger than temperature gradient ΔT0, and a rotational speed is increased from R2 to R3. When an absolute value is larger than a temperature gradient ΔT1, the rotational speed is further increased to R4. In this manner, when an input thermal load is large, cooling performance is increased by lowering a temperature of evaporator 115 so that a time until a surface layer is slightly frozen can be reliably shortened. In such an operation, when a time for the first rapid cooling is extended, there arises an adverse effect such as frosting of the inside of temperature changeable compartment 107 or freezing of a food in a compartment disposed adjacently to temperature changeable compartment 107. Accordingly, the first rapid cooling time is not extended.
As in the case of second rapid cooling shown in FIG. 9B, when an absolute value of a temperature gradient ΔT falls within a range of from ΔT0 to ΔT1 inclusive, although a time for the second rapid cooling is t1, when an absolute value of a temperature gradient ΔT is equal to or more than ΔT1, a time for the second rapid cooling is extended in proportion to a value of a temperature gradient ΔT. However, even when a thermal load having a temperature gradient of ΔT2 or more is put in the accommodating compartment, a time for the second rapid cooling is not extended to time t2 or more. An upper limit line t2 is set such that an adverse effect such as frosting or freezing of a food does not occur. As described above, by adjusting a rapid cooling operation condition in conformity with an amount of an input thermal load, a time until a surface layer is slightly frozen can be reliably shortened. It is also possible to prevent the occurrence of an adverse effect due to an excessive cooling and an unnecessary increase of an operating cost.

INDUSTRIAL APPLICABILITY

As described above, the present invention provides a refrigerator which can prevent oxidation of foods by interrupting contact between foods and oxygen without causing fixing of foods to each other and lowering of flavor of foods, and can preserve a preserved food while keeping freshness of the food. Further, the present invention provides a refrigerator which can perform the determination of the presence or absence of an input food in the accommodating compartment with a simple specification. Accordingly, the present invention is applicable not only to the household refrigerator but also to business-use refrigerators, show cases, cooler boxes, and the like.

REFERENCE MARKS IN THE DRAWINGS

101: refrigerator
102: refrigerating compartment (storage compartment)
102a: refrigerating compartment door
103: first freezing compartment
103a: first freezing compartment door
104: second freezing compartment
104a: second freezing compartment door
105: ice-making compartment
105a: ice-making compartment door
106: vegetable compartment
106a: vegetable compartment door
107: temperature changeable compartment (accommodating compartment, partial freezing compartment)
108: outer box
109: inner box
110: heat insulating wall
111: heat insulating partition wall
112: compressor
113: machine compartment
114: cooling compartment
115: cooler (evaporator)
116: blowing fan
117, 117a, 117b: damper device (damper)
118: shelf plate
120: refrigerating compartment duct
121: illumination device
122: upper surface cover
123: accommodating case
123a: rear surface wall
123b: front surface wall
124: opening and closing door
125: temperature changeable compartment back surface duct
126: temperature changeable compartment ceiling surface duct
126a: heat insulating duct member
126b: duct cover
127: door opening and closing detection part (accommodating compartment opening and closing detection part)
128: bottom plate
129: cool air blow-off port
131: setting part
132: controller (controller)
133: temperature changeable compartment temperature sensor (temperature sensor)
134: food put-in determination part

Claims

A refrigerator comprising:
an accommodating compartment;

a cooler for generating cool air;

an air blower for blowing cool air from the cooler to the accommodating compartment; and

a controller for controlling the air blower,

wherein the controller is configured to control blowing of the cool air to the accommodating compartment so as to preserve the food at a slightly freezing temperature and to slightly freeze a surface of food preserved in the accommodating compartment.
The refrigerator according to claim 1, wherein
the air blower includes:
a duct for blowing the cool air from the cooler to the accommodating compartment;

a damper which is disposed in the duct; and

a temperature sensor which detects a temperature in the accommodating compartment, and

the controller is configured to forcibly open the damper for a predetermined time so that the surfaces of the foods preserved in the accommodating compartment are quickly slightly frozen and to control opening and closing of the damper based on a temperature detected by the temperature sensor such that the foods are preserved at the slightly freezing temperature.
The refrigerator according to claim 2, further comprising a compressor which constitutes a refrigeration cycle together with the cooler,
wherein the controller is configured to forcibly open the damper for the predetermined time and to continuously operate the compressor.
The refrigerator according to any one of claims 1 to 3, further comprising an accommodating compartment opening and closing detection part which detects an open and close state of the accommodating compartment,
wherein the controller is configured to execute a control of blowing of the cool air to the accommodating compartment in response to detection of an open and close state of the accommodating compartment by the accommodating compartment opening and closing detection part.
The refrigerator according to any one of claims 1 to 4, wherein the accommodating compartment is incorporated at a corner of a storage compartment, and a temperature in the accommodating compartment is controlled independently from a temperature in the storage compartment.
The refrigerator according to any one of claims 1 to 5, further comprising:
a temperature sensor which detects a temperature in the accommodating compartment; and

a food put-in determination part which determines whether or not a food has been put into the accommodating compartment,

wherein the food put-in determination part is configured to make the controller forcibly stop blowing of the cool air by the air blower for a predetermined time and to determine presence or absence of an input food in the accommodating compartment based on a temperature detected by the temperature sensor.
The refrigerator according to claim 6, wherein
the food put-in determination part makes the controller forcibly stop the blowing of the cool air by the air blower for the predetermined time, and makes the controller forcibly operate the air blower for a predetermined time, to determine presence or absence of an input food in the accommodating compartment based on a temperature detected by the temperature sensor during a period in which the air blower is forcibly operated.
The refrigerator according to claim 6 or 7, wherein the determination by the food put-in determination part is executed a plurality of times.
The refrigerator according to any one of claims 1 to 8, further comprising:
an accommodating compartment opening and closing detection part which detects opening or closing of the accommodating compartment; and

a food put-in determination part for determining presence or absence of an input food in the accommodating compartment,

wherein the food put-in determination part is configured to perform determination of the presence or absence of the input food in the accommodating compartment in response to detection of an open and close state of the accommodating compartment by the accommodating compartment opening and closing detection part.