JP7478990B2 - refrigerator - Google Patents

Description

The present invention relates to a refrigerator having a freezing function and a storage compartment capable of thawing frozen items.

A typical refrigerator is equipped with a freezer compartment and is used to freeze ingredients and foods for long-term storage. It is desirable for such frozen foods to be thawed in a short time and used in cooking in a thawed state as close to fresh as possible.

There are methods for thawing frozen foods, such as natural thawing at room temperature and thawing under running tap water, but these thawing methods do not satisfy the short thawing time required by cooks. In ordinary households, microwave cooking appliances, so-called microwave ovens, are used to thaw frozen foods in a short time. However, when thawing frozen foods in a microwave oven, although it is possible to thaw frozen foods in a short time, there are cases where an undesirable thawing state occurs, such as so-called "partially cooked" in which high-frequency energy is concentrated in the previously thawed area and the food cannot be thawed evenly. Thus, when thawing frozen foods using a microwave oven, it is not easy to achieve a desirable high-quality thawed state. Here, a high-quality thawed state refers to a thawed state that is unpalatable as food, such as one that has "partially cooked".

Patent Document 1 discloses a refrigerator equipped with a high-frequency heating chamber that is configured to supply cold air and thaw frozen items while irradiating them with microwaves. In the refrigerator of Patent Document 1, the surface of the frozen items in the high-frequency heating chamber is covered with cold air, and the inside of the frozen items is thawed by irradiating the frozen items with microwaves.

JP 2002-147919 A

The refrigerator disclosed in Patent Document 1 is provided with a magnetron to generate microwaves, and is configured to irradiate microwaves to frozen items in a high-frequency heating chamber for microwave heating. The refrigerator in Patent Document 1 is configured to be large overall as it is equipped with a magnetron, which is a microwave generating means, and a cooling mechanism for the magnetron, making it difficult to reduce the size of the refrigerator. In addition, because the refrigerator is configured to irradiate microwaves from an antenna to frozen items in a high-frequency heating chamber for microwave heating, it is difficult to heat the frozen items evenly and defrost them to the desired state.

In addition, in conventional refrigerators, when room temperature food stored in the storage compartment is frozen, frost forms on the inside of the food packaging due to moisture in the cold storage compartment and moisture inside the food. When this frost forms on the surface of the food, the food becomes dry and has a crisp texture, and is no longer tasty and fresh ("freezer burn"). A challenge in this field has been to perform the freezing process to prevent this "freezer burn" from occurring.

The present invention aims to provide a refrigerator that has excellent performance as a food storage facility, having a thawing function that can easily thaw frozen products to a high-quality state, and also capable of storing the stored items in the storage compartment in the desired state during freezing and frozen storage processes.

A refrigerator according to one aspect of the present invention comprises at least one storage compartment having a storage space capable of containing stored items and being cooled, an inner surface member constituting the inner surface of the storage compartment, a cooling mechanism that generates cold air, an air passage that guides the cold air from the cooling mechanism to the storage compartment, a pair of electrodes arranged opposite each other across the storage space, a high-frequency electric field forming unit for forming a high-frequency electric field to be applied between the pair of electrodes, a cold-air introduction mechanism provided in the air passage that guides the cold air formed by the cooling mechanism to the storage compartment, and a control unit that controls the cooling mechanism and the cold-air introduction mechanism to introduce cold air from the air passage when the high-frequency electric field is applied between the pair of electrodes, wherein the inner surface member has a cold-air introduction hole, and the cold air in the air passage is introduced from the cold-air introduction hole into the storage compartment.

The present invention provides a refrigerator that has a thawing function that can easily thaw frozen products to a high-quality state, and also has excellent performance as a food storage facility, storing the preserved items stored in the storage compartment in the desired state during freezing and frozen storage processes.

FIG. 1 is a cross-sectional view showing a vertical section of a refrigerator according to a first embodiment of the present invention. FIG. 1 is a vertical cross-sectional view showing a freezing/thawing compartment in a refrigerator according to a first embodiment of the present invention. FIG. 1 is a block diagram showing a configuration of a dielectric heating mechanism provided in a refrigerator according to a first embodiment. FIG. 1 is a diagram showing an electrode holding area on the rear side of a freezing/thawing compartment in a refrigerator according to a first embodiment. FIG. 1 is a plan view showing an oscillation electrode and an inner surface member on the top surface side of a freezing/thawing compartment in a refrigerator according to a first embodiment; FIG. 1 is a back view showing a counter electrode on a bottom side arranged opposite to an oscillation electrode in the refrigerator of the first embodiment. FIG. 11 is a plan view showing a modified example of the oscillation electrode in the refrigerator according to the first embodiment. FIG. 1A is a cross-sectional view showing a schematic diagram of a dielectric heating configuration provided with a counter electrode having no electrode holes; and FIG. 1B is an electric field simulation diagram showing the results of a simulation performed on the dielectric heating configuration shown in FIG. FIG. 1A is a cross-sectional view showing a schematic diagram of a dielectric heating configuration provided with a counter electrode having an electrode hole; and FIG. 1B is an electric field simulation diagram showing the results of a simulation performed on the dielectric heating configuration shown in FIG. FIG. 13 shows the waveforms of the control signals for the oscillator circuit and the damper during the defrosting process in the configuration of the first embodiment, and also shows the food temperature, the room temperature in the freezing/defrosting compartment, and the humidity in the freezing/defrosting compartment at that time. 1 is a flowchart showing control after the thawing process is completed in the freezing/thawing compartment in the configuration of the first embodiment. FIG. 1A is a waveform diagram showing a cooling operation during freezing in a conventional refrigerator; and FIG. 1B is a waveform diagram showing a cooling operation performed in a freezing/thawing compartment in a refrigerator according to a first embodiment. FIG. 1 is a waveform diagram showing the state of each element during rapid cooling in the configuration of the first embodiment.

Below, as an embodiment of the refrigerator of the present invention, a refrigerator with a freezing function will be described with reference to the attached drawings. Note that the refrigerator of the present invention is not limited to the configuration of the refrigerator described in the following embodiment, but can also be applied to freezers that have only a freezing function, and includes various refrigerators and freezers that have the technical features described in the following embodiment. Therefore, in the present invention, a refrigerator is configured to have a refrigeration compartment and/or a freezing compartment.

In addition, the numerical values, shapes, configurations, steps, and order of steps shown in the following embodiments are merely examples and do not limit the present invention. Among the components in the following embodiments, those components that are not described in an independent claim that indicates the highest concept are described as optional components. Note that in the embodiments, the same elements may be given the same reference numerals even in modified examples, and descriptions thereof may be omitted. In addition, the drawings mainly show each component in a schematic manner to facilitate understanding.

First, various embodiments of the refrigerator of the present invention will be illustrated.
A refrigerator according to a first aspect of the present invention includes:
At least one storage chamber having a storage space capable of storing and cooling stored items;
A cooling mechanism for generating cold air;
an air passage that guides cool air from the cooling mechanism to the storage chamber;
an oscillation electrode provided in the storage space;
a counter electrode provided in the storage space and facing the oscillation electrode;
a high frequency electric field generating unit for generating a high frequency electric field to be applied between the oscillation electrode and the counter electrode;
a cold air introduction mechanism provided in the air passage and guiding the cold air generated by the cooling mechanism to the storage chamber;
a control unit that controls the cooling mechanism and the cold air introduction mechanism to introduce cold air from the air passage when a high frequency electric field is applied between the oscillation electrode and the counter electrode;
The refrigerator according to the first aspect thus configured can reliably perform freezing, freezing and thawing processes on the stored items stored in the storage compartment so that the stored items maintain a desired high quality state.

A second aspect of the present invention is the refrigerator of the first aspect, further comprising a reflected wave detection unit that detects a reflected wave returning from the oscillation electrode toward the high frequency electric field generating unit,
The control unit may be configured to control the cooling mechanism and the cold air introduction mechanism based on a reflectance that indicates a ratio of a reflected wave to an electromagnetic wave output from the oscillation electrode.

The refrigerator of the third aspect of the present invention may be the refrigerator of the first or second aspect described above, further comprising an inner surface member that constitutes the inner surface of the storage chamber, and the inner surface member may be configured to cover the opposing electrode surfaces of the oscillation electrode and the counter electrode.

The refrigerator according to a fourth aspect of the present invention is the third aspect, and may be configured such that the inner surface member has a cold air inlet hole, and cold air in the air passage is introduced into the storage chamber through the cold air inlet hole.

A fifth aspect of the refrigerator according to the present invention is any one of the first to fourth aspects, in which the oscillation electrode is disposed on the top side of the heating chamber, the counter electrode is disposed on the bottom side of the heating chamber, and an opening is formed in the oscillation electrode through which cool air from the air passage passes.

A sixth aspect of the present invention provides a method for controlling a refrigerator, comprising the steps of: inputting a thawing command for a frozen item that is a stored item stored in a storage compartment;
applying a high frequency electric field to an oscillation electrode and a counter electrode disposed on either side of a storage space of the storage chamber when a defrosting command is input;
and controlling a cooling mechanism for generating cold air and a cold air introduction mechanism for introducing the cold air into the storage chamber when a high frequency electric field is applied between the oscillation electrode and the counter electrode. The control method of the sixth aspect having such steps can reliably perform freezing, freezing and thawing processes on the preserved items stored in the storage chamber so that the preserved items maintain a desired high quality state.

A seventh aspect of the present invention provides a control method for a refrigerator according to the sixth aspect, comprising: detecting a reflected wave returning from the oscillation electrode toward a high frequency electric field forming unit that forms a high frequency electric field;
The method may further include controlling the introduction of cool air into the storage chamber based on a reflectance indicating a ratio of a reflected wave to an electromagnetic wave output from the oscillation electrode.

The refrigerator control method of the eighth aspect of the present invention may be the seventh aspect, in which the thawing process in response to a thawing command for frozen items stored in the storage compartment is terminated based on the reflectance.

The refrigerator control method of the ninth aspect of the present invention may be the eighth aspect, in which the storage compartment is maintained in a slightly freezing temperature range after the thawing process in response to a thawing command is completed.

The refrigerator control method of the tenth aspect of the present invention may be any of the sixth to ninth aspects, and may further comprise the step of performing a freezing process on a thawed stored item when the thawed stored item has been continuously stored in the storage chamber for a predetermined time from the end of the thawing process in response to a thawing command.

The refrigerator control method of the eleventh aspect of the present invention may be any of the sixth to tenth aspects, in which a high-frequency electric field is applied to the oscillation electrode and the counter electrode during freezing, freezing and thawing of a stored item stored in a storage compartment.

(Embodiment 1)
A first embodiment of a refrigerator according to the present invention will be described below with reference to the drawings. Fig. 1 is a diagram showing a vertical cross section of a refrigerator 10 according to the first embodiment. In Fig. 1, the left side is the front side of the refrigerator 10, and the right side is the rear side of the refrigerator 10. The refrigerator 10 is composed of an insulated box body formed of an outer box 1 mainly made of steel plate, an inner box 2 molded from a resin such as ABS, and an insulating material (e.g., rigid foamed urethane) 40 filled and foamed in the space between the outer box 1 and the inner box 2.

The insulated box of the refrigerator 10 has multiple storage compartments, and an openable door is provided at the front opening of each storage compartment. When the door is closed, each storage compartment is sealed to prevent cold air from leaking. In the refrigerator 10 of the first embodiment, the top storage compartment is the refrigerator compartment 3. Two storage compartments, an ice-making compartment 4 and a freezer/thawing compartment 5, are arranged side by side on both sides directly below the refrigerator compartment 3. Furthermore, a freezer compartment 6 is provided directly below the ice-making compartment 4 and the freezer/thawing compartment 5, and a vegetable compartment 7 is provided at the bottom directly below the freezer compartment 6. Each storage compartment in the refrigerator 10 of the first embodiment has the above configuration, but this configuration is one example, and the layout and configuration of each storage compartment can be changed as appropriate during design depending on specifications, etc.

Refrigerator compartment 3 is maintained at a temperature that will not freeze food and other preserved items, specifically, at a temperature range of 1°C to 5°C. Vegetable compartment 7 is maintained at a temperature range equal to or slightly higher than that of refrigerator compartment 3, specifically, at 2°C to 7°C. Freezer compartment 6 is set to a freezing temperature range for frozen storage, specifically, at a temperature range of -22°C to -15°C. Freezer/thaw compartment 5 is normally maintained at the same freezing temperature range as freezer compartment 6, and a thawing process is performed to thaw the stored items (frozen goods) in response to a thawing command from the user. The configuration of freezer/thaw compartment 5 and details regarding the thawing process will be described later.

A machine room 8 is provided at the top of the refrigerator 10. The machine room 8 houses components that make up the refrigeration cycle, such as a compressor 9 and a dryer that removes moisture during the refrigeration cycle. The location of the machine room 8 is not limited to the top of the refrigerator 10, but is determined appropriately depending on the location of the refrigeration cycle, and it may be located in another area, such as the bottom of the refrigerator 10.

The cooling chamber 11 is provided on the rear side of the freezer chamber 6 and the vegetable chamber 7 in the lower region of the refrigerator 10. The cooling chamber 11 is provided with a cooler 12, which is a component of the refrigeration cycle that generates cold air, and a cooling fan 13 that blows the cold air generated by the cooler 12 to each storage chamber (3, 4, 5, 6, 7). The cold air generated by the cooler 12 flows through an air duct 18 connected to each storage chamber by the cooling fan 13 and is supplied to each storage chamber. A damper 19 is provided in the air duct 18 connected to each storage chamber, and each storage chamber is maintained at a predetermined temperature range by controlling the rotation speed of the compressor 9 and the cooling fan 13 and opening and closing control of the damper 19. A defrost heater 14 is provided at the bottom of the cooling chamber 11 to remove frost and ice that adheres to the cooler 12 and its surroundings. A drain pan 15, a drain tube 16, and an evaporation dish 17 are provided at the bottom of the defrost heater 14, and are configured to evaporate moisture generated during defrosting, etc.

The refrigerator 10 of the first embodiment is provided with an operation unit 47 (see FIG. 3 described later). The user can use the operation unit 47 to give various commands to the refrigerator 10 (for example, temperature setting for each storage compartment, a quick cooling command, a defrosting command, a command to stop ice making, etc.). The operation unit 47 also has a display unit that notifies the occurrence of abnormalities, etc. The refrigerator 10 may also be configured to have a wireless communication unit and connect to a wireless LAN network so that various commands can be input from the user's external terminal. The refrigerator 10 may also be configured to have a voice recognition unit so that the user can input commands by voice.

Figure 2 is a vertical cross-sectional view showing the freezing/thawing compartment 5 in the refrigerator 10 of the first embodiment. The freezing/thawing compartment 5 is a freezer that keeps stored items such as food stored in the freezing/thawing compartment 5 at a freezing temperature range, and also becomes a thawing compartment that performs a thawing process by dielectric heating when a thawing command for the stored items is input in the refrigerator 10.

In order to maintain the freezing/thawing chamber 5 at the same freezing temperature range as the freezing chamber 6, the cold air generated in the cooler 12 flows through air ducts 18 provided on the back and top sides of the freezing/thawing chamber 5 and is introduced into the freezing/thawing chamber 5 through multiple cold air inlet holes 20 provided on the top surface of the freezing/thawing chamber 5. A damper 19 is provided in the air duct 18 leading from the cooling chamber 11 to the freezing/thawing chamber 5, and the freezing/thawing chamber 5 is maintained at a specified freezing temperature range by controlling the opening and closing of the damper 19, and the stored items are frozen and preserved.

A cold air exhaust hole 21 is formed on the back surface of the freezing/thawing chamber 5. The cold air that is introduced into the freezing/thawing chamber 5 and cools the interior of the freezing/thawing chamber 5 returns to the cooling chamber 11 through the cold air exhaust hole 21 and the return air passage 34, and is re-cooled by the cooler 12. That is, in the refrigerator 10 of the first embodiment, the cold air generated by the cooler 12 is configured to circulate.

The top, back, both sides, and bottom of the freezing/thawing chamber 5, which constitute the inner surface of the storage space, are formed of an inner surface member 32 made of a resin material molded from an electrically insulating material. A door 29 is provided at the front opening of the freezing/thawing chamber 5, and the storage space of the freezing/thawing chamber 5 is sealed when the door 29 is closed. In the freezing/thawing chamber 5 of embodiment 1, a storage case 31 with an open top is provided on the back side of the door 29, and the storage case 31 moves back and forth at the same time when the door 29 is opened and closed in the forward and backward directions. The forward opening of the door 29 makes it easy to put food and other preserved items into and take them out of the storage case 31.

Next, we will explain the dielectric heating mechanism that performs dielectric heating to thaw the items stored frozen in the freezing/thawing chamber 5.

Figure 3 is a block diagram showing the configuration of the dielectric heating mechanism provided in the refrigerator 10 of the first embodiment. The dielectric heating mechanism in the first embodiment includes an oscillator circuit 22 that receives power from a power supply unit 48 to form a predetermined high-frequency signal, a matching circuit 23, an oscillator electrode 24, a counter electrode 25, and a control unit 50. The oscillator circuit 22, which is made of semiconductor elements, is miniaturized and is provided in the machine room 8 of the refrigerator 10. The oscillator circuit 22 is electrically connected to the matching circuit 23 by a coaxial cable. The matching circuit 23 is disposed in the electrode holding area 30 (see Figure 2), which is the space on the rear side of the freezing/thawing chamber 5. The oscillator circuit 22 and the matching circuit 23 form a high-frequency electric field forming unit for forming a high-frequency electric field to be applied between the oscillator electrode 24 and the counter electrode 25.

The oscillation electrode 24 is a planar electrode disposed on the top surface side of the freezing/thawing chamber 5. The counter electrode 25 is a planar electrode disposed on the bottom surface side of the freezing/thawing chamber 5. The oscillation electrode 24 and the counter electrode 25 are disposed opposite each other across the storage space (thawing space) of the freezing/thawing chamber 5, and a spacing regulation part 33, which will be described in the "electrode holding mechanism" below, is provided to set the opposing distance to a predetermined distance (first distance) that has been set in advance. As a result, in the dielectric heating mechanism in the first embodiment, the oscillation electrode 24 and the counter electrode 25 are disposed approximately parallel to each other. In the present invention, "approximately parallel" refers to an essentially parallel state, but also includes errors due to variations in processing accuracy, etc.

The oscillation electrode 24 is provided on one side of the storage space, and the counter electrode 25 is provided on the other side of the storage space, sandwiching the storage space. The matching circuit 23 on the back side, the oscillation electrode 24 on the top side, and the counter electrode 25 on the bottom side, which constitute the dielectric heating mechanism, are covered with an inner surface member 32, which reliably prevents the stored items from burning due to contact with them.

In the configuration of the first embodiment, the oscillator electrode 24 is provided on the top surface of the storage space of the freezing/thawing chamber 5, and the counter electrode 25 is provided on the bottom surface of the storage space of the freezing/thawing chamber 5. However, the present invention is not limited to this configuration, and it is sufficient that the oscillator electrode 24 and the counter electrode 25 face each other across the storage space (thawing space). The same effect can be achieved even if they are arranged upside down or facing each other in the left-right direction.

2, the freezing/thawing chamber 5 has a configuration in which cold air from the cooler 12 passes through the air passage 18 and is introduced from the top side of the freezing/thawing chamber 5. At the top side of the freezing/thawing chamber 5, an oscillation electrode 24 is arranged on the underside of the air passage 18, and the cold air from the cooling chamber 11 flows over the oscillation electrode 24. In the refrigerator 10 of the first embodiment, an insulated box is formed by the outer box 1, the inner box 2, and the insulating material 40 filled and foamed between them, and the space in which the storage chamber is formed in this insulated box does not have high dimensional accuracy. In the space in which the freezing/thawing chamber 5 is formed, an area that becomes the air passage 18 is formed on the top side, and this area that becomes the air passage 18 becomes a space that can absorb dimensional variations in the insulated box. The cold air that has passed through the air passage 18 passes through multiple electrode holes 41 formed in the oscillation electrode 24 and is introduced into the freezing/thawing chamber 5 from the cold air introduction hole 20 of the inner surface member 32 on the top side, as will be described later.

The oscillator circuit 22 outputs a high-frequency voltage in the VHF band (40.68 MHz in the first embodiment). When the oscillator circuit 22 outputs a high-frequency voltage, an electric field is formed between the oscillator electrode 24 to which the oscillator circuit 22 is connected and the counter electrode 25, and the stored material, which is a dielectric material, placed in the storage space between the oscillator electrode 24 and the counter electrode 25 in the freezing/thawing chamber 5 is dielectrically heated.

The matching circuit 23 adjusts the load impedance formed by the oscillation electrode 24, the counter electrode 25, and the stored object contained in the freezing/thawing chamber 5 so that it matches the output impedance of the oscillation circuit 22. The matching circuit 23 minimizes the reflected waves of the output electromagnetic waves by matching the impedance. The dielectric heating mechanism in the first embodiment is provided with a reflected wave detection unit 51 that detects the reflected waves returning from the oscillation electrode 24 to the oscillation circuit 22. Therefore, the oscillation circuit 22 is electrically connected to the oscillation electrode 24 via the reflected wave detection unit 51 and the matching circuit 23. The control unit 50 calculates the ratio (reflectance) of the reflected wave output to the electromagnetic wave output based on the electromagnetic waves output from the oscillation circuit 22 after impedance matching in the matching circuit 23 and the reflected waves detected by the reflected wave detection unit 51, and performs various controls based on the calculation results as described below.

As shown in the block diagram of FIG. 3, in the dielectric heating mechanism, the control unit 50 drives and controls the oscillation circuit 22 and the matching circuit 23 based on signals from the operation unit 47, which allows the user to perform setting operations, and the temperature sensor 49, which detects the temperature inside the cabinet. The control unit 50 is composed of a CPU, and executes control programs stored in a memory such as a ROM to perform various controls.

In addition, since it is desirable for the length of the positive electrode wiring connecting the oscillation circuit 22, the matching circuit 23, and the oscillation electrode 24 to be short, the high-frequency electric field generating section of the oscillation circuit 22 and the matching circuit 23 may be arranged in the electrode holding area 30 on the rear side of the freezing/thawing chamber 5.

[Electrode retention mechanism]
The dielectric heating mechanism in the first embodiment configured as described above has a configuration in which the flat-plate oscillating electrode 24 and the counter electrode 25 face each other substantially parallel to each other, thereby achieving a uniform electric field in the thawing space, which is the storage space of the freezing/thawing chamber 5. In order to thus dispose the oscillating electrode 24 and the counter electrode 25 substantially parallel to each other with a predetermined gap (first gap) therebetween, the dielectric heating mechanism in the first embodiment has an electrode holding mechanism, which will be described below.

Figure 4 shows the electrode holding area 30 on the rear side of the freezing/thawing chamber 5 in embodiment 1, and shows the electrode holding mechanism in the electrode holding area 30. Figure 4 shows the electrode holding area 30 as viewed from the rear side, with the oscillation electrode 24 disposed on the upper side (top side) and the counter electrode 25 disposed on the lower side (bottom side). A positive terminal 24a protrudes from the center of the rear end of the flat plate-shaped oscillation electrode 24, and support members 24b, 24b protrude on both sides. The positive terminal 24a and the support member 24b protrude downward (bottom side) from the rear end of the flat plate-shaped oscillation electrode 24 at a right angle. Similarly, a negative terminal 25a protrudes from the center of the rear end of the flat plate-shaped counter electrode 25, and support members 25b, 25b protrude on both sides. The negative terminal 25a and the support member 25b are bent at a right angle and protrude upward (toward the top surface) from the rear end of the flat counter electrode 25. That is, the protruding ends of the positive terminal 24a of the oscillation electrode 24 and the support member 24b face each other, respectively, with the protruding ends of the negative terminal 25a of the counter electrode 25 and the support member 25b.

As described above, the protruding direction of each of the support members 24b, 24b of the oscillation electrode 24 faces the protruding direction of each of the support members 25b, 25b of the counter electrode 25, and each of the support members 24b, 24b is linearly joined to the opposing support members 25b, 25b via the spacing defining portion 33. The spacing defining portion 33 is a planar member formed of an electrically insulating material that is not substantially dielectrically heated. As shown in FIG. 4, the spacing defining portion 33 has an H-shape when viewed from the rear side, and the support members (24b, 25b) are connected to the four upper and lower ends of the H-shape, and the matching circuit 23 is fixed to the center part of the H-shape. Therefore, the oscillation electrode 24 and the counter electrode 25 are fixed to both the upper and lower ends of the spacing defining portion 33, the matching circuit 23 is fixed to the center part of the spacing defining portion 33, and the oscillation electrode 24, the counter electrode 25, and the matching circuit 23 are securely held by the spacing defining portion 33. In this way, the spacing defining portion 33 is configured to reliably hold the oscillation electrode 24 and the counter electrode 25, which are essentially planar plate-like members, at a predetermined distance (first distance). Since the matching circuit 23 is fixed to the center of the H-shape of the spacing defining portion 33, the rigidity is high and the spacing defining portion 33 is configured to be able to cantilever-hold the oscillation electrode 24 and the counter electrode 25 at a predetermined opposing distance (first distance). The spacing defining portion 33 may also be configured to include a high-frequency electric field generating portion for the oscillation circuit 22 and the matching circuit 23.

The positive terminal 24a of the oscillation electrode 24 and the negative terminal 25a of the counter electrode 25 are connected to the positive and negative connection terminals of the matching circuit 23. The connection between the positive terminal 24a and the negative terminal 25a and each connection terminal of the matching circuit 23 is a surface-contact connection with a predetermined contact area so as to ensure reliability even when a large current flows. In the first embodiment, in order to ensure a reliable surface-contact connection, the flat terminals are connected to each other by screws. Note that the connection between the terminals may be any connection means that provides a reliable surface-contact connection, and is not limited to a screw connection.

In the first embodiment, the terminal width w (see FIG. 4) of the positive terminal 24a protruding from the rear end of the oscillation electrode 24 is formed to be significantly narrower than the electrode width W (see FIG. 4) of the rear end of the oscillation electrode 24 (w << W). This is to make it difficult for heat generated in the matching circuit 23 to be conducted to the oscillation electrode 24, and to suppress the thermal conduction between the matching circuit 23 and the oscillation electrode 24, thereby suppressing the occurrence of condensation in the matching circuit 23 when the oscillation electrode 24 is cooled. In addition, in the counter electrode 25, the terminal width of the negative terminal 25a is also formed to be significantly narrower than the electrode width of the rear end of the counter electrode 25 from which the negative terminal 25a protrudes, similar to the terminal width of the positive terminal 24a. By narrowing the terminal width of the negative terminal 25a in this way, the thermal conduction between the counter electrode 25 and the matching circuit 23 is suppressed.

As shown in Figures 2 and 4, the cold air that has frozen the stored items in the freezing/thawing chamber 5 is configured to return from the cold air exhaust hole 21 through the return air duct 34, passing through the electrode holding area 30, and to the cooling chamber 11. Because the return air duct 34 is configured to pass through the electrode holding area 30 in this way, the cold air from the freezing/thawing chamber 5 is not released in the electrode holding area 30, and condensation is prevented in the electrode holding area 30, including the matching circuit 23.

In addition, in a configuration in which the oscillator circuit 22 is disposed in the electrode holding area 30, a cooling configuration in which a heat sink, which is a heat dissipation member in the oscillator circuit 22, is brought into contact with the return air passage 34 for cooling may be used.

As described above, an electrode holding mechanism is provided on the rear side of the freezing/thawing chamber 5, so that the flat oscillating electrode 24 and the counter electrode 25 face each other in a substantially parallel manner. In the configuration of embodiment 1, an electrode holding mechanism is also provided on the front side of the freezing/thawing chamber 5 to further ensure that the oscillating electrode 24 and the counter electrode 25 face each other in a substantially parallel manner.

As described above, the insulated box of the refrigerator 10 is composed of the outer box 1 made of steel plate, the inner box 2 molded from resin, and the insulating material (e.g., rigid foamed urethane) 40 filled and foamed in the space between the outer box 1 and the inner box 2. The insulated box of the refrigerator 10 is also provided with a cross rail 35, which is a frame for defining the edge of the front opening of each storage compartment. The cross rail 35 of the frame is joined to a predetermined position of the outer box 1 and is positioned with high precision relative to the outer box 1. Therefore, the position of the cross rail 35 relative to the outer box 1 is not affected by the insulating material 40 filled and foamed, and is positioned with high precision.

As shown in FIG. 2, a cross rail 35 is provided on the front edge of the freezing/thawing chamber 5, and this cross rail 35 defines the front opening of the freezing/thawing chamber 5. This front opening is opened and closed by a door 29 of the freezing/thawing chamber 5. A gasket 36 is provided between the door 29 and the cross rail 35 to prevent leakage of cold air when the door is closed.

The electrode holding mechanism on the front side of the freezing/thawing chamber 5 utilizes a cross rail 35, which is a frame that precisely defines the front opening of the freezing/thawing chamber 5. The first and second holding claws 37 and 38, which are holding members, are integrally formed at a predetermined interval on the approximately parallel frame material above and below the cross rail 35. The first and second holding claws 37 and 38, which are holding members, may be configured to be joined to the cross rail 35, which is a frame.

The first holding claw 37, which is a holding member, is configured to engage the front end of the oscillation electrode 24 so as to sandwich it, and determines the position of the front end of the oscillation electrode 24. The second holding claw 38, which is a holding member, is configured to support the front end of the counter electrode 25, and determines the position of the front end of the counter electrode 25. The first holding claw 37 and the second holding claw 38 hold the front end of the oscillation electrode 24 and the counter electrode 25 at a predetermined interval (first interval). The first holding claw 37 and the second holding claw 38 also maintain the oscillation electrode 24 and the counter electrode 25 in an electrically insulated state.

Therefore, in the refrigerator 10 of embodiment 1, the dielectric heating mechanism of the freezing/thawing compartment 5 is provided with electrode holding mechanisms on both the back and front sides, so that the oscillation electrode 24 and the counter electrode 25 can be arranged with a highly accurate opposing distance, and can also be arranged reliably and approximately parallel with a predetermined distance (first distance). As a result, the dielectric heating mechanism of the freezing/thawing compartment 5 is configured to prevent bias in the high-frequency electric field on the electrode surface and to homogenize the high-frequency electric field, making it possible to perform a uniform thawing process on stored items (frozen goods).

[Electromagnetic wave shielding mechanism]
As described above, in freezing/thawing compartment 5, the dielectric material, which is a stored object, is placed in the atmosphere of the high-frequency electric field between oscillating electrode 24 and counter electrode 25 and is dielectrically heated, so that electromagnetic waves can be emitted in freezing/thawing compartment 5. In order to prevent these electromagnetic waves from leaking outside refrigerator 10, refrigerator 10 of the first embodiment is provided with an electromagnetic wave shielding mechanism that surrounds freezing/thawing compartment 5.

As shown in FIG. 2, a top-side electromagnetic wave shield 26 is disposed above the air passage 18 on the top side of the freezing/thawing chamber 5. The top-side electromagnetic wave shield 26 is disposed on the top surface of the heat insulating material 40 constituting the bottom side of the refrigerator chamber 3 directly above the freezing/thawing chamber 5, and is disposed so as to cover the top side of the freezing/thawing chamber 5. The top-side electromagnetic wave shield 26 has multiple openings and is configured so that the effective opposing area with respect to the oscillation electrode 24 is small. The top-side electromagnetic wave shield 26 configured in this manner is configured to suppress the generation of unnecessary electric fields between the oscillation electrode 24. The top-side electromagnetic wave shield 26 may be a mesh structure having multiple openings. The top-side electromagnetic wave shield 26 may be disposed inside the refrigerator chamber 3 located directly above the freezing/thawing chamber 5, but the refrigerator chamber 3 often has a partial chamber or chilled chamber, and the top surface of the partial chamber or chilled chamber may be used as the electromagnetic wave shield.

A rear electromagnetic shield 27 is also provided to cover the electrode holding area 30 having the matching circuit 23 and other components provided on the rear side of the freezing/thawing chamber 5. Providing the rear electromagnetic shield 27 in this manner prevents the electric field generated between the oscillation electrode 24 and the counter electrode 25 and the high-frequency noise generated by the matching circuit 23 from affecting the operation (control) of the electrical components of the cooling fan 13 and the damper 19. An electromagnetic shield (not shown) is also provided on the side of the freezing/thawing chamber 5.

Next, the door-side electromagnetic shield 39 provided on the door 29 that opens and closes the front opening of the freezing/thawing compartment 5 will be described. Since the door 29 is configured to open and close relative to the body of the refrigerator 10, if the electromagnetic shield provided on the door 29 is connected to the grounded part of the body of the refrigerator 10 by a wired path, the wired path will repeatedly expand and contract as the door 29 is opened and closed, and metal fatigue will accumulate in the wired path. Since such a connection configuration can cause the wired path to break, it is not preferable to connect the electromagnetic shield 39 provided on the door 29 to the grounded part of the body of the refrigerator 10 by a wired path.

In general, to prevent electromagnetic wave leakage, it is necessary to make the distance between the door-side electromagnetic shield 39 and the cross rail 35, which serves as the electromagnetic shield on the main body side, shorter than 1/4 of the wavelength λ of the electromagnetic wave when the door 29 is closed. In the first embodiment, the distance is further reduced to obtain the effect of contact without providing a wired path. For example, the distance between the door-side electromagnetic shield 39 and the cross rail 35 when the door 29 is closed is set to within 30 mm. Since the cross rail 35 connected to the outer box 1 is grounded, by bringing the door-side electromagnetic shield 39 close to the cross rail 35 when the door 29 is closed, an effect equivalent to grounding by a wired path can be obtained. In addition, by making the end of the door-side electromagnetic shield 39 bent toward the main body side of the refrigerator 10, the door-side electromagnetic shield 39 can be easily brought close to the cross rail 35.

In the refrigerator 10 of the first embodiment, the outer box 1 is made of a steel plate, and the steel plate itself functions as an electromagnetic wave shield. This reliably prevents electromagnetic waves from inside the refrigerator 10 from leaking outside the refrigerator 10.

[Configuration of Oscillation Electrode and Counter Electrode]
When the user opens the door 29, high-humidity air flows from the outside into the freezing/thawing compartment 5, which is maintained in the freezing temperature range, and the inside of the freezing/thawing compartment 5 becomes prone to condensation. If condensation occurs on the surfaces of the oscillation electrode 24 and the counter electrode 25, the electric field formation between the electrodes becomes unstable, and a state in which desired dielectric heating is not performed may occur. In order to prevent such a state from occurring, the refrigerator 10 of the first embodiment is configured to cover the oscillation electrode 24 and the counter electrode 25 with an inner surface member 32, and to introduce cold air into the freezing/thawing compartment 5 through a plurality of cold air introduction holes 20 formed in the oscillation electrode 24. The cold air introduced into the freezing/thawing compartment 5 is cold air sent from the cooling compartment 11 through the air passage 18 by the cooling fan 13, and the cold air at the time of introduction is in a relatively low humidity state. Therefore, even if the door 29 is opened and closed and high humidity air flows in from the outside, low humidity cold air is blown into the freezing/thawing chamber 5 from the multiple cold air inlet holes 20 formed over the entire top side, and the air inside the freezing/thawing chamber 5 is exhausted from the cold air exhaust holes 21 on the back side, so that the inside of the freezing/thawing chamber 5 is less likely to develop condensation.

Figure 5 is a plan view of the oscillation electrode 24 and the inner surface member 32 on the top side of the freezing/thawing chamber 5, as viewed from above. As shown in Figure 5, the oscillation electrode 24 has a plurality of electrode holes 41 formed therein, which are distributed over the entire surface of the electrode surface of the oscillation electrode 24. The electrode holes 41 are arranged approximately uniformly at equal intervals on the electrode surface of the oscillation electrode 24. The electrode holes 41 of the oscillation electrode 24 are provided in correspondence with the positions of the cold air introduction holes 20 formed in the inner surface member 32 that covers the lower surface of the oscillation electrode 24. The hole diameter D of the electrode hole 41 is formed to be larger than the hole diameter d of the cold air introduction hole 20 of the inner surface member 32 (D>d).

Since multiple electrode holes 41 are formed at equal intervals and approximately uniformly on the electrode surface of the oscillation electrode 24, the areas where a strong electric field is formed on the electrode surface of the oscillation electrode 24 are uniformly distributed, resulting in a configuration that allows uniform dielectric heating of stored items. In other words, the edges of the openings of the electrode holes 41 become the electric field concentration areas. Note that the shapes and arrangements of the multiple cold air introduction holes 20 and electrode holes 41 shown in Figure 5 are examples, and the shapes and arrangements of the cold air introduction holes 20 and electrode holes 41 are appropriately designed taking into account efficiency and manufacturing costs according to the specifications and configuration of the refrigerator.

Figure 6 is a back view showing the bottom side of the counter electrode 25 arranged opposite the oscillation electrode 24. Figure 6 is a view of the counter electrode 25 seen from below, and an inner surface member 32 that becomes the bottom surface of the freezing/thawing chamber 5 is arranged on the counter electrode 25. As shown in Figure 6, a plurality of electrode holes 42 are formed at equal intervals and approximately evenly on the electrode surface of the counter electrode 25, similar to the oscillation electrode 24. However, in the configuration of embodiment 1, the electrode holes 42 of the counter electrode 25 are formed in a position that does not face the electrode holes 41 of the oscillation electrode 24. That is, the position of the central axis extending in the vertical direction of the electrode hole 42 of the counter electrode 25 is shifted from the position of the central axis extending in the vertical direction of the electrode hole 41 of the oscillation electrode 24, and the electrode holes 42 of the counter electrode 25 and the electrode holes 41 of the oscillation electrode 24 are shifted in position in the vertical direction (opposing direction).

In the configuration of the first embodiment, the shape and arrangement of the electrode holes 41 of the oscillation electrode 24 are described as being arranged with a plurality of electrode holes 41 arranged at equal intervals and approximately uniformly, but the present invention is not limited to such a configuration. For example, the oscillation electrode 24 may have at least one opening, and the edge of the opening becomes an electric field concentration area on the electrode surface of the oscillation electrode 24 where the electric field is concentrated. In other words, the present invention is sufficient as long as the electric field concentration area is dispersed on the electrode surface of the oscillation electrode 24. In addition, in the first embodiment, the configuration in which a plurality of electrode holes 42 are provided on the electrode surface of the counter electrode 25 is described, but the present invention is not limited to the configuration in which a plurality of electrode holes 42 are provided on the counter electrode 25, and it is sufficient that the opening is formed so that a desired electric field is formed between the electrode and the oscillation electrode 24.

7 is a plan view showing an example of a modified example of the oscillation electrode 24 in the first embodiment. The modified example shown in FIG. 7(a) shows an example in which one opening portion is formed as the electrode hole 41A in the oscillation electrode 24. In the first embodiment, the opening portion formed in the oscillation electrode 24 is the electrode opening, and this electrode opening includes the electrode holes (41, 41A). The electrode opening 41A shown in FIG. 7(a) includes a circular opening 41a, an arc-shaped opening 41b, and a communication opening 41c that communicates the respective openings (41a, 41b). By making the electrode opening 41A in such a shape, the region in which the electric field becomes strong on the electrode surface of the oscillation electrode 24 can be dispersed. The modified example shown in FIG. 7(b) shows a modified example of the electrode opening (41B) in the oscillation electrode 24, and is an example in which an electrode notch portion 41B in which a notch portion is formed in the oscillation electrode 24 is formed. As shown in FIG. 7B, by forming the electrode cutout 41B as an opening, the area where the electric field is strong on the electrode surface of the oscillation electrode 24 is dispersed. The cold air introduction hole 20 formed in the inner surface member 32 covering the lower surface of the oscillation electrode 24 is formed at a position corresponding to the electrode opening (41, 41A, 41B) of the oscillation electrode 24, and is configured so that the cold air from the air passage 18 is smoothly introduced into the freezing/thawing chamber 5.

As described above, in the first embodiment, the top surface of the freezing/thawing chamber 5 is configured so that cold air is introduced into the freezing/thawing chamber 5 through the electrode openings (41, 41A, 41B), which are the openings of the oscillation electrode 24 that constitute the underside of the air passage 18. Therefore, the freezing/thawing chamber 5 is configured so that cold air is blown through the cold air introduction holes 20 formed on the top surface, and a uniform and rapid freezing process can be performed in the freezing/thawing chamber 5. In addition, since the electrode surface of the oscillation electrode 24 is formed so that the electric field concentration area is dispersed, uniform dielectric heating can be performed on the stored items, and good thawing can be performed.

In the configuration shown in Figures 5 and 6, the electrode hole 41 of the oscillation electrode 24 and the electrode hole 42 of the counter electrode 25 are formed so that the central axes extending in the vertical direction (opposing direction) do not coincide with each other, thereby dispersing the area of electric field concentration in the oscillation electrode 24 and the counter electrode 25, and homogenizing the electric field in the storage space where the oscillation electrode 24 and the counter electrode 25 face each other. As a result, the stored items placed in the storage space of the freezing/thawing chamber 5 can be subjected to more uniform dielectric heating.

The inventors performed a simulation of the generation of an electric field between the electrodes using a freezing/thawing chamber 5 having the electrode configuration of embodiment 1 and, as a comparative example, a freezing/thawing chamber 5X having an electrode configuration with a counter electrode 25X that does not have an electrode hole.

Figure 8(a) is a cross-sectional view showing a schematic diagram of an electrode configuration in which an opposing electrode 25X having no electrode holes is provided, and is a diagram of the freezing/thawing chamber 5X cut in the left-right direction. Figure 8(b) shows the results of a simulation of the electric field strength when an electric field is applied to the electrodes of the electrode configuration shown in Figure 8(a). In Figure 8(b), the darker parts are areas where the electric field is concentrated. As is clear from this electric field simulation diagram, the electric field is concentrated at the outer edge parts of the electrode, and especially at the corner parts.

Figure 9(a) is a cross-sectional view showing a schematic of the electrode configuration of the freezing/thawing chamber 5 having the configuration of embodiment 1, and is a view of the freezing/thawing chamber 5 cut in the left-right direction. Figure 9(b) shows the results of a simulation of the electric field strength when an electric field is applied to the electrodes of the electrode configuration shown in Figure 9(a). In Figure 9(b) as in Figure 8(b), the darker parts are areas where the electric field is concentrated. As is clear from this electric field simulation diagram, compared to the electric field simulation diagram of Figure 8(b), the dielectric heating configuration of Figure 9(a) has reduced electric field concentration over the entire electrode, and it can be seen that the electric field is made uniform.

As shown in FIG. 9(b), the electrode holes 41 of the oscillation electrode 24 and the electrode holes 42 of the counter electrode 25 are arranged so that their central axes extending in the vertical direction (opposing direction) do not coincide, thereby reducing electric field concentration throughout the entire electrode. In an electrode configuration in which the electrode holes 41 of the oscillation electrode 24 and the electrode holes 42 of the counter electrode 25 are arranged so that their central axes extending in the vertical direction (opposing direction) coincide, electric field concentration is reduced compared to the configuration in which the counter electrode 25X without an electrode hole shown in FIG. 8 is provided, and the electric field concentration is particularly reduced at the corners.

In the freezing/thawing compartment 5 of the refrigerator 10 of the first embodiment, as shown in FIG. 2, the storage case 31 is fixed to the rear side of the door 29. The storage case 31 moves back and forth inside the freezing/thawing compartment 5 as the door 29 opens and closes. In the configuration of the first embodiment, rails 52 are provided on both sides of the freezing/thawing compartment 5 so that the storage case 31 can move smoothly inside the freezing/thawing compartment 5 (see FIG. 9). In addition, frames 53 that slide on the rails 52 are provided on both outer sides of the storage case 31. The sliding members of the rails 52 and the frames 53 are provided in positions outside the dielectric heating area, which is the area where the oscillation electrode 24 and the counter electrode 25 of the freezing/thawing compartment 5 face each other, so as not to be dielectrically heated.

[Decompression process]
In refrigerator 10 of embodiment 1, when a defrost command is input, a defrosting process is performed on the stored item (frozen item) between oscillation electrode 24 and counter electrode 25 in freezing/defrosting compartment 5. In the defrosting process of embodiment 1, as described below, control unit 50 controls a dielectric heating mechanism having oscillation circuit 22 and matching circuit 23, and also controls a cooling mechanism including a refrigeration cycle such as compressor 9 and cooler 12, and a cold air introduction mechanism including cooling fan 13, damper 19, etc.

In the thawing process in the first embodiment, a predetermined high-frequency voltage is applied between the oscillator electrode 24 and the counter electrode 25, and the high-frequency electric field between the electrodes dielectrically heats the frozen product. During this dielectric heating, the damper 19 is controlled to open and close, and cold air is intermittently introduced. Figure 10 shows the waveforms of the control signals for the dielectric heating mechanism (oscillating circuit 22) and the cold air introduction mechanism (damper 19) during the thawing process, as well as the food temperature, room temperature in the freezing/thawing chamber 5, and humidity in the freezing/thawing chamber 5 at that time.

The configuration using VHF waves as the frequency characteristic for the defrosting process is less likely to cause "partial cooking" than the configuration using microwaves, but to further improve the uniformity of the defrosting, the refrigerator 10 of the first embodiment is provided with a spacing regulation part 33, which reliably holds the oscillation electrode 24 and the counter electrode 25, which are essentially flat plate-like members, approximately parallel with a predetermined spacing (first spacing).

As shown in FIG. 10, in the thawing process, when a thawing command is input (thawing start), the oscillation circuit is turned on and a high-frequency voltage of, for example, 40 MHz is applied between the oscillation electrode 24 and the counter electrode 25. At this time, the damper 19 is in an open state, so the room temperature of the freezing/thawing chamber 5 is maintained at the freezing temperature t1 (for example, -20°C). The damper 19 is closed after a predetermined period has elapsed since the start of thawing. When the damper 19 is closed, the room temperature of the freezing/thawing chamber 5 begins to rise. In the thawing process in embodiment 1, dielectric heating is performed and the damper 19 is controlled to open and close, thereby suppressing the rise in the surface temperature of the frozen product and performing thawing without causing so-called "partial cooking". The control unit 50 controls the opening and closing of the damper 19 based on the ratio (reflectance) of the reflected wave detected by the reflected wave detection unit 51 to the electromagnetic wave matched by the matching circuit 23 and supplied between the oscillation electrode 24 and the counter electrode 25. When the reflectance reaches a preset threshold and increases, the control unit 50 opens the damper 19 to lower the temperature inside the freezing/thawing chamber 5. In this way, by controlling the opening and closing of the damper 19, cold air is intermittently introduced into the freezing/thawing chamber 5, so that the stored items in the storage space (thawing space) of the freezing/thawing chamber 5 are dielectrically heated while maintaining the desired frozen state, and reach the desired thawed state.

The thawing process is complete when the desired thawed state is reached, but in order to detect the desired thawed state at which the thawing process is complete, the thawing process of embodiment 1 uses reflectance. As the melting of the stored object progresses due to dielectric heating, the number of melted water molecules in the stored object increases. As the number of melted water molecules in the stored object increases, the dielectric constant changes and the impedance matching state shifts. As a result, the reflectance, which is the ratio of reflected waves to output electromagnetic waves, increases. In the thawing process, when the reflectance increases and reaches a preset threshold, the matching circuit 23 performs impedance matching to reduce the reflectance.

In the thawing process of the first embodiment, the completion of thawing is detected when the reflectance after impedance matching by the matching circuit 23 exceeds the threshold for completion of thawing. The threshold for completion of thawing is used to detect when the melting of the stored object has reached a desired thawed state. Here, the desired thawed state of the stored object is a state in which a woman can cut the stored object with one hand and the amount of dripping from the stored object is very small. The threshold for completion of thawing is a value determined in advance by experiment.

As shown in FIG. 10, the damper 19 is controlled to open and close so that relatively low-humidity cold air that has passed through the air passage 18 is supplied to the freezing/thawing chamber 5 through the cold air inlet 20, so that the humidity in the freezing/thawing chamber 5 never reaches 100%, preventing condensation from forming in the freezing/thawing chamber 5.

[Control after completion of decompression process]
Fig. 11 is a flowchart showing control after the thawing process is completed in the freezing/thawing compartment 5. Each step shown in the flowchart in Fig. 11 is performed by the CPU of the control unit 50 executing a control program stored in a memory such as a ROM. As described above, when the reflectance after impedance matching by the matching circuit 23 in the thawing process exceeds the threshold value for the completion of thawing, the control after the completion of the thawing process shown in Fig. 11 is performed.

As shown in step 101 of FIG. 11, after the thawing process is completed, the room temperature of the freezing/thawing chamber 5 is maintained in the so-called slightly freezing temperature range, for example, about -1° to -3°C. By maintaining the freezing/thawing chamber 5 in the slightly freezing temperature range in this way, the stored items are maintained in the desired thawed state. When the freezing/thawing chamber 5 is maintained at the slightly freezing temperature, the presence or absence of stored items in the freezing/thawing chamber 5 is constantly detected (step 102). The presence or absence of stored items in the freezing/thawing chamber 5 is detected using the reflectance, which is constantly detected. For this reason, the matching circuit 23 is always intermittently operated, and low-power electromagnetic waves are intermittently output from the oscillation electrode 24. The control unit 50 compares the reflectance with a preset threshold value for the presence or absence of stored items to determine the presence or absence of stored items in the freezing/thawing chamber 5.

When it is detected in step 102 that there is no stored item in the freezing/thawing chamber 5, it is determined that the stored item has been removed in the desired thawed state, and the room temperature of the freezing/thawing chamber 5 is set to the freezing temperature range, for example, -18°C to -20°C (step 105).

In step 102, when it is detected that there is a stored item in the freezing/thawing chamber 5, it is determined whether the stored items present include new non-frozen items (e.g., room temperature food). Whether new non-frozen items are present in the freezing/thawing chamber 5 is determined by a change in reflectance. In step 103, when it is determined that new non-frozen items have been placed in the freezing/thawing chamber 5, the room temperature of the freezing/thawing chamber 5 is set as the freezing temperature zone (step 105).

On the other hand, in step 103, when it is determined that no new non-frozen items are stored in the freezing/thawing chamber 5 and that the thawed stored items are still being held, it is determined whether the time since the completion of thawing has exceeded a predetermined time (step 104). Even if the thawing process for the stored items is completed, the user may not immediately remove the stored items from the freezing/thawing chamber 5. In such a case, the refrigerator 10 of the first embodiment is configured to maintain the slightly freezing temperature range in which the desired thawed state can be maintained for the stored items in the freezing/thawing chamber 5 for a predetermined time. If the stored items are stored in the freezing/thawing chamber 5 for more than the predetermined time, the refrigerator 10 of the first embodiment controls the room temperature of the freezing/thawing chamber 5 to be shifted to the freezing temperature range in order to maintain the freshness of the stored items. In step 104, when it is determined that the time since the completion of thawing has exceeded a predetermined time while the thawed stored items are still being held, the process proceeds to step 105, and the freezing process is performed with the room temperature of the freezing/thawing chamber 5 in the freezing temperature range.

As described above, in the refrigerator 10 of embodiment 1, after the thawing process is completed, the stored items can be kept in the desired thawed state in the freezing/thawing compartment 5 for a specified period of time to maintain their freshness, and appropriate temperature control can be performed for the stored items inside the freezing/thawing compartment 5.

[Freezing/thawing chamber freezing operation]
The refrigerator 10 of the first embodiment is configured to perform dielectric heating so that food, which is a preserved item, is frozen and preserved in a desired state during a freezing process in which the room temperature of the freezing/thawing compartment 5 is maintained within the freezing temperature range. Generally, when food is frozen, frosting occurs on the inner surface of the food packaging due to moisture in the freezing/thawing compartment 5 and moisture inside the food. When such frosting occurs on the surface of the food, the food becomes dry and has a dry texture, and is no longer tasty and fresh ("freezer burn"). To prevent such a condition, the refrigerator 10 of the first embodiment performs a dielectric heating operation together with a cooling operation at the same time.

Figure 12 is a waveform diagram showing the state of each element during the cooling operation. Figure 12(a) is a waveform diagram showing the cooling operation during frozen storage in a conventional refrigerator, and Figure 12(b) is a waveform diagram showing the cooling operation performed in the freezing/thawing compartment 5 in the refrigerator 10 of embodiment 1.

In FIG. 12(a), (1) is a waveform diagram showing the ON/OFF of the cooling operation. The ON/OFF of the cooling operation corresponds to, for example, the opening and closing of a damper, or the ON/OFF operation of a compressor. ON indicates a state in which cold air is being introduced into the freezer, and OFF indicates a state in which the damper is closed and the introduction of cold air into the freezer is blocked. Therefore, as shown in the waveform diagram of FIG. 12(a)(2), the temperature of the food in the freezer will fluctuate greatly above and below the preset freezing temperature T1 (for example, -20°C). As a result, evaporation of water and frost formation will occur repeatedly on the surface of the food in the freezer, and the food may not be frozen in a desirable state.

On the other hand, in the cooling operation of the first embodiment shown in FIG. 12(b), unlike the conventional cooling operation, the food is cooled and dielectrically heated at the same time. (1) in FIG. 12(b) is a waveform diagram showing the opening and closing operation of the damper 19, with ON indicating that the damper 19 is open and cold air is introduced into the freezing/thawing chamber 5 from the cold air inlet 20 through the air passage 18. OFF indicating that the damper 19 is closed and the introduction of cold air into the freezing/thawing chamber 5 is blocked. The introduction of cold air in the cooling operation of the first embodiment is performed simultaneously with dielectric heating, so the introduction time of the cold air is set longer than in the conventional example, which means that the cooling capacity is increased.

Figure 12(b) (2) is a waveform diagram showing the operating state of dielectric heating when the oscillator circuit 22 is driven and controlled. When the damper 19 is open, dielectric heating is also performed at the same time. In the cooling operation in embodiment 1, dielectric heating is performed with a much smaller output than in the thawing operation. As a result, as shown in Figure 12(b) (3), the temperature of the food in the freezing/thawing chamber 5 is maintained at a preset freezing temperature T1 (e.g., -20°C), and fluctuations in the food temperature are suppressed.

Experiments have shown that if the fluctuation in food temperature is less than about 0.1 K, frost formation can be prevented. At the very least, the smaller the fluctuation in food temperature, the more the occurrence of frost can be suppressed. Furthermore, inside the food, dielectric heating has the effect of suppressing the growth of ice crystals. When dielectric heating is performed, the electric field tends to gather at the tips of the ice crystals that have formed inside the food, so even if the temperature inside the freezing/thawing chamber 5 is below the maximum ice crystal formation zone, the ice crystals will only grow slowly.

As described above, in the refrigerator 10 of embodiment 1, the dielectric heating operation is performed even during the cooling operation during frozen storage, so that the frozen items can be frozen and stored in the desired state.

[Freezing process]
In the refrigerator 10 of the first embodiment, it is possible to perform a freezing process on non-frozen food newly placed in the freezing/thawing compartment 5 based on a user's command from the operation unit 47. FIG. 13 is a waveform diagram showing the state of each element in the rapid cooling operation, which is a freezing process. In FIG. 13, (a) is a graph showing whether or not a preserved item (food) is present in the freezing/thawing compartment 5. The determination of whether or not a preserved item is present in the freezing/thawing compartment 5 is made by the control unit 50 based on the ratio (reflectance) of the reflected wave detected by the reflected wave detection unit 51 to the output electromagnetic wave. (b) of FIG. 13 shows that the control unit 50 intermittently acquires information from the matching circuit 23 and the reflected wave detection unit 51. (c) of FIG. 13 is a graph showing an example of the transition of the reflectance. The control unit 50 determines that a preserved food item has been placed in the freezing/thawing compartment 5 when the reflectance becomes equal to or less than the first threshold value R1.

When rapidly cooling food stored in the freezing/thawing compartment 5, the rotation speed of the compressor 9 and cooling fan 13 of the cooling mechanism is increased to increase the cooling capacity and perform forced continuous operation. In addition, the damper 19 of the air passage 18 leading to the freezing/thawing compartment 5 is forcibly driven in a continuous open state, and the cold air introduction mechanism is driven and controlled so that cold air is introduced (see the waveform diagram in Figure 13 (d)).

In the rapid cooling operation, a dielectric heating operation is performed to suppress the growth of ice crystals when the food temperature is in the maximum ice crystal formation zone (approximately -1°C to approximately -5°C). The dielectric heating operation at this time is performed at a low output of approximately 1W to approximately 10W, and dielectric heating is performed intermittently (period H in Figure 13(e)). In order to start the dielectric heating operation, the food temperature entering the maximum ice crystal formation zone is detected by an increase in the change in reflectance when the food passes through the latent heat zone. In the first embodiment, when the detected reflectance enters a preset second threshold value R2, the dielectric heating operation is started (see Figure 13(e)). Note that the region from the second threshold value R2 to the third threshold value R3 in reflectance is considered to be the maximum ice crystal formation zone for the food, and the dielectric heating operation is continued. When a predetermined time (t2) has elapsed since the reflectance entered the third threshold value R3, it is determined that the food has passed the maximum ice crystal formation zone, and the dielectric heating operation is stopped.

As described above, when it is determined that the food has passed the maximum ice crystal formation zone, the dielectric heating operation is stopped, and the rapid cooling operation is terminated, and the normal cooling operation is started. In this way, even when the rapid cooling operation is performed, the dielectric heating operation is performed for the desired period of time, so that the food can be frozen to a desired state.

As described above, the freezing/thawing compartment 5 of the refrigerator in embodiment 1 has the excellent effect of being able to freeze and store frozen items in a desired state, and being able to thaw frozen items in a desired state to a desired state in a short period of time, and by using a dielectric heating mechanism made up of semiconductor elements, it is possible to achieve a compact refrigerator with a thawing function.

In the refrigerator of the first embodiment, the freezing/thawing compartment 5 is described as having both a freezing function and a thawing function, but the refrigerator may be configured with a thawing compartment 5 that only has a thawing function.

As described above, the refrigerator of the present invention has a thawing function that can easily thaw frozen items to a high-quality state, as explained in embodiment 1, and also has excellent performance as a food storage facility, storing stored items stored in the storage chamber in a desired state during freezing and frozen storage processes. Therefore, according to the present invention, it is possible to provide a highly safe refrigerator with reliable cooling, storage, and thawing functions that can freeze, store, and thaw stored items stored in the storage chamber in a desired state.

As described above, the refrigerator of the present invention has the excellent effect of being able to store frozen products in a desired state and being able to thaw frozen products in a desired state to a desired state in a short period of time, and by using a dielectric heating mechanism made up of semiconductor elements, it is possible to achieve a compact refrigerator with a thawing function.

Although the present invention has been described in the embodiments with a certain degree of detail, the disclosed contents of the embodiments may vary in the details of the configuration, and substitutions, combinations, and changes in the order of elements in the embodiments may be made without departing from the scope and spirit of the invention as claimed.

The refrigerator of the present invention is configured to be able to process stored items in a desired state for freezing, storage, and thawing, and therefore has a configuration that increases the added value of the refrigerator and has high market value.

LIST OF SYMBOLS 1 Outer box 2 Inner box 3 Refrigerator compartment 4 Ice maker compartment 5 Freezer/thaw compartment 6 Freezer compartment 7 Vegetable compartment 8 Machine compartment 9 Compressor 10 Refrigerator 11 Cooling compartment 12 Cooler 13 Cooling fan 14 Defrost heater 15 Drain pan 16 Drain tube 17 Evaporation dish 18 Air passage 19 Damper 20 Cold air inlet 21 Cold air exhaust 22 Oscillation circuit 23 Matching circuit 24 Oscillation electrode 25 Counter electrode 26 Top side electromagnetic shield 27 Rear side electromagnetic shield 28 Front side electromagnetic shield 29 Door 30 Electrode holding area 31 Storage case 32 Inner surface member 33 Spacing regulation section 34 Return air passage 39 Door side electromagnetic shield 40 Insulation material 41 Electrode hole (oscillation electrode)
42 Electrode hole (counter electrode)
47 Operation unit 48 Power supply unit 49 Temperature sensor 50 Control unit 51 Reflected wave detection unit

Claims (3)

At least one storage chamber having a storage space capable of storing and cooling stored items;
An inner surface member that configures an inner surface of the storage chamber;
A cooling mechanism for generating cold air;
an air passage that guides cool air from the cooling mechanism to the storage chamber;
A pair of electrodes arranged opposite to each other across the storage space;
a high frequency electric field generating unit for generating a high frequency electric field to be applied between the pair of electrodes;
a cold air introduction mechanism provided in the air passage and guiding the cold air generated by the cooling mechanism to the storage chamber;
a control unit that controls the cooling mechanism and the cold air introduction mechanism so as to introduce cold air from the air passage when a high-frequency electric field is applied between the pair of electrodes;
the pair of electrodes is an oscillation electrode and a counter electrode, the inner surface member is an electrically insulating resin member,
the electrode surfaces of the oscillation electrode and the counter electrode facing each other are covered with the inner surface member,
The refrigerator is configured such that the inner surface member has a cold air introduction hole, and cold air in the air passage is introduced into the storage compartment through the cold air introduction hole. a reflected wave detection unit that detects a reflected wave returning from the oscillation electrode toward the high frequency electric field generating unit,
The refrigerator according to claim 1 , wherein the control unit is configured to control the cooling mechanism and the cold air introduction mechanism based on a reflectance indicating a ratio of a reflected wave to an electromagnetic wave output from the oscillation electrode. 3. The refrigerator according to claim 1, wherein the oscillation electrode is disposed on a top surface side of the storage compartment, the counter electrode is disposed on a bottom surface side of the storage compartment, and an opening portion is formed in the oscillation electrode through which cool air from the air passage passes.

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