WO2024262611A1 - Refrigerator - Google Patents

Abstract

A refrigerator according to the present disclosure comprises: a storage chamber in which a stored object can be heated; and a dielectric heating mechanism that generates high-frequency power and that supplies the high-frequency power to the storage chamber to generate an electric field inside the storage chamber. The dielectric heating mechanism comprises: an electrode disposed in the storage chamber; an oscillation circuit that supplies high-frequency power to the electrode; a matching circuit that executes impedance matching; a detection unit that is connected between the oscillation circuit and the matching circuit and that measures incident wave power and reflected wave power; and a control unit. The control unit controls the oscillation circuit and the matching circuit on the basis of the incident wave power and the reflected wave power, and detects an abnormality in the incident wave power or the reflected wave power.

Description

refrigerator

This disclosure relates to a refrigerator equipped with a storage compartment that has the function of thawing frozen foods.

Patent Document 1 discloses a refrigerator capable of thawing frozen products. The refrigerator described in Patent Document 1 includes, inside its main body, a refrigeration unit and a freezing chamber, as well as a high-frequency generating magnetron and a heating chamber.

The refrigerator described in Patent Document 1 can supply cold air from a refrigeration unit to a heating chamber via a cold air circulation duct, and can also supply high frequency waves from a magnetron to the heating chamber to thaw frozen items stored in the heating chamber. In other words, this heating chamber is a storage chamber in which frozen items can be thawed.

Patent Document 2 discloses a refrigeration device capable of supplying cold air uniformly inside the freezer. The freezer described in Patent Document 2 is equipped with one or both of an alternating electric field generating unit that applies an alternating electric field to the object to be frozen and a magnetic field generating unit that applies a magnetic field inside a closed space, and applies one or both of the alternating electric field and the magnetic field to the object to be frozen.

JP 2002-147919 A JP 2003-214751 A

The objective of this disclosure is to provide a refrigerator that can detect a malfunction by detecting noise contained in sparks caused by frost, condensation, and deterioration over time such as temperature stress, and quickly shuts down the operation to prevent the malfunction from expanding.

The refrigerator disclosed herein comprises a storage compartment capable of heating stored items, and a dielectric heating mechanism that generates high-frequency power and supplies the high-frequency power to the storage compartment to generate an electric field inside the storage compartment. The dielectric heating mechanism comprises an electrode disposed in the storage compartment, an oscillation circuit that supplies high-frequency power to the electrode, a matching circuit that matches the impedance of the electrode, a detection unit connected between the oscillation circuit and the matching circuit to measure incident wave power output from the matching circuit to the electrode and reflected wave power returning to the oscillation circuit, and a control unit. The control unit controls the oscillation circuit and the matching circuit based on the incident wave power and the reflected wave power, and detects abnormalities in the incident wave power or the reflected wave power.

The refrigerator disclosed herein can detect abnormalities more accurately and stop operation appropriately.

FIG. 1 is a vertical cross-sectional view of a refrigerator according to an embodiment of the present disclosure. FIG. 2 is a front cross-sectional view showing the freezing/thawing compartment of the refrigerator according to the embodiment. FIG. 3 is a side cross-sectional view showing the freezing/thawing compartment of the refrigerator according to the embodiment. FIG. 4 is a vertical cross-sectional view showing how the freezing/thawing compartment is incorporated into the main body of the refrigerator according to the embodiment. FIG. 5 is a front sectional view showing a modified example of the freezing/thawing compartment in the refrigerator according to the embodiment. FIG. 6 is a side cross-sectional view showing a modified example of the freezing/thawing compartment in the refrigerator according to the embodiment. FIG. 7 is a vertical cross-sectional view showing how the freezing/thawing compartment is incorporated into the main body of the refrigerator according to the embodiment. FIG. 8 is a schematic diagram showing an electrode holding area on the rear side of a freezing/thawing compartment in a refrigerator according to an embodiment. FIG. 9 is a block diagram of a dielectric heating mechanism disposed in the refrigerator according to the embodiment. FIG. 10 is a schematic circuit diagram of an AC/DC converter in the dielectric heating mechanism. FIG. 11 is a plan view of a first electrode and a second electrode of a freezing/thawing compartment in a refrigerator according to an embodiment, as viewed from above. FIG. 12 is a diagram showing the relationship between the electrode distance between the first electrode and the second electrode and the electric field intensity between the two electrodes. FIG. 13A is an electric field simulation diagram showing the results of a simulation performed on a dielectric heating configuration. FIG. 13B is an electric field simulation diagram showing the results of a simulation performed on the dielectric heating configuration of the freezing/thawing compartment in the refrigerator according to the embodiment. FIG. 14 is a diagram showing the control signal in the electric field generation process, the temperatures of the food and the freezing/thawing compartment, and the humidity in the freezing/thawing compartment in the configuration of the embodiment. FIG. 15 is a flow chart showing the control after the electric field generation process is completed in the freezing/thawing chamber in the configuration of this embodiment. FIG. 16A is a waveform diagram showing a cooling operation in a conventional refrigerator. FIG. 16B is a waveform diagram showing the cooling operation in the refrigerator according to the embodiment. FIG. 17 is a waveform diagram showing the state of each element during a rapid cooling operation in the configuration of the embodiment. FIG. 18A is a diagram illustrating an example of the high frequency blocking circuit when the door of the refrigerator according to the embodiment is opened. FIG. 18B is a diagram illustrating another example of the high-frequency blocking circuit when the door of the refrigerator according to the embodiment is opened. FIG. 18C is a diagram illustrating still another example of the high frequency blocking circuit when the door of the refrigerator in accordance with the embodiment is opened. FIG. 19A is a cross-sectional view showing an example of cable wiring to a freezing/thawing compartment in a refrigerator according to an embodiment. FIG. 19B is a cross-sectional view showing an example of cable wiring to a freezing/thawing compartment in a refrigerator according to an embodiment. FIG. 20A is a timing chart showing a process for an abnormal sensor voltage of a dielectric heating mechanism in a refrigerator according to an embodiment. FIG. 20B is a timing chart for detecting spark occurrence in a dielectric heating mechanism in a refrigerator according to an embodiment. FIG. 20C is a timing chart for detecting spark generation in a dielectric heating mechanism in a refrigerator according to an embodiment. FIG. 21 is a timing chart for detecting an abnormality in the electric circuit of the dielectric heating mechanism in the refrigerator according to the embodiment. FIG. 22 is a timing chart for detecting an abnormality in the electric circuit of the dielectric heating mechanism in the refrigerator according to the embodiment. FIG. 23 is a flowchart showing a process for determining whether or not there is an abnormality in the dielectric heating mechanism in the refrigerator according to the embodiment.

(The knowledge that formed the basis of this disclosure)
At the time when the inventors conceived the subject matter of the present disclosure, the refrigerator described in Patent Document 1 was known.

The refrigerator described in Patent Document 1 irradiates the frozen items in the heating chamber with high-frequency waves from a magnetron via an antenna or the like, thereby heating the frozen items. Therefore, if there is an uneven distribution of high-frequency waves in the heating chamber, it is difficult to heat the frozen items evenly and defrost them to the desired state.

The above conventional refrigerators are equipped with a magnetron that generates high frequency waves, as well as a cooling mechanism for the magnetron. Therefore, it is difficult to reduce the size of the above conventional refrigerators.

In addition, studies have been conducted to suppress the formation of ice crystals by applying an alternating electric field to the preserved item when freezing it. For example, Patent Document 2 describes a freezing device that applies an alternating electric field to the item to be frozen. However, with the freezing device described in Patent Document 2, it is difficult to melt the ice crystals that form in the preserved item, and freezing destroys the cell membrane of the preserved item.

The technology described in Patent Document 1 and the technology described in Patent Document 2 are difficult to apply simultaneously due to differences in output frequency and output power. As described in Patent Document 2, when a device using metal components is used in a freezer environment, malfunctions may occur due to condensation or frost caused by moisture in food or moisture from the outside. In order to solve these problems, the inventors conceived the subject matter of the present disclosure.

The objective of this disclosure is to provide a small, reliable refrigerator that can freeze, store, and thaw items stored in a storage compartment in a desired state.

Below, as an embodiment of the present disclosure, a refrigerator with a freezing function and a defrosting function will be described with reference to the attached drawings. The refrigerator according to the present disclosure is not limited to the configuration described in the embodiment below, but can also be applied to a freezer that only has a freezing function. Therefore, in this disclosure, a refrigerator is a device that has one or both of a refrigerator compartment and a freezer compartment.

(Embodiment)
A refrigerator 1 according to an embodiment of the present disclosure will be described with reference to the drawings.

[1-1. Overall configuration of refrigerator]
Fig. 1 is a vertical cross-sectional view of a refrigerator 1 according to the present embodiment. The left and right sides in Fig. 1 correspond to the front side and rear side, respectively, of the refrigerator 1. As shown in Fig. 1, a main body 2 of the refrigerator 1 is an insulated box body including an outer box 3, an inner box 4, and a thermal insulation material 40.

The outer box 3 is mainly made of steel plate. The inner box 4 is made of resin such as ABS (Acrylonitrile, Butadiene, Styrene). The heat insulating material 40 is, for example, rigid urethane foam, which is foamed and filled into the space between the outer box 3 and the inner box 4.

The main body 2 of the refrigerator 1 has multiple storage compartments, namely, a refrigerator compartment 5, a freezer/thaw compartment 6, an ice-making compartment 7, a freezer compartment 8, and a vegetable compartment 9. An openable and closable door is provided at the front opening of each storage compartment. The doors cover the front openings of the multiple storage compartments to prevent cold air from leaking out of the storage compartments.

In the refrigerator 1 according to this embodiment, the refrigerator compartment 5 is the uppermost of the multiple storage compartments. Directly below the refrigerator compartment 5, two storage compartments, the ice-making compartment 7 and the freezer/thaw compartment 6, are arranged side by side on the left and right. The freezer compartment 8 is arranged directly below the ice-making compartment 7 and the freezer/thaw compartment 6. The vegetable compartment 9 is arranged directly below the freezer compartment 8.

The configuration and arrangement of each storage compartment in the refrigerator 1 according to this embodiment is an example, and the present disclosure is not limited thereto. The configuration and arrangement of each storage compartment can be changed as appropriate depending on the specifications, etc.

Refrigerator compartment 5 is maintained at a temperature for refrigerating food and other preserved items, specifically 1°C to 5°C. Vegetable compartment 9 is maintained at a temperature range equal to or slightly higher than refrigerator compartment 5, for example 2°C to 7°C. Freezer compartment 8 is maintained in the freezing temperature range for frozen storage, specifically, for example -22°C to -15°C.

The freezing/thawing compartment 6 is normally maintained at the same freezing temperature range as the freezing compartment 8. In the freezing/thawing compartment 6, an electric field generation process is carried out to thaw the stored items (frozen goods) in response to a command from the user to start generating an electric field (hereinafter, an electric field generation command). The configuration of the freezing/thawing compartment 6 and the details of the electric field generation process will be described later.

A machine room 10 is located at the top of the refrigerator 1 (the top in this embodiment). The machine room 10 houses components that make up the refrigeration cycle, such as a compressor 19 and a dryer that removes moisture during the refrigeration cycle. The location of the machine room 10 is not limited to the top of the refrigerator 1, but is determined appropriately depending on the location of the refrigeration cycle, etc. For example, the machine room 10 may be located at the bottom of the refrigerator 1.

The cooling compartment 11 is located behind the freezer compartment 8 and vegetable compartment 9, which are located at the bottom of the refrigerator 1. The cooling compartment 11 is equipped with a cooler 13 and a cooling fan 14. The cooler 13 is a component of the refrigeration cycle that generates cold air. The cooling fan 14 blows the cold air generated by the cooler 13 through the air passage 12 to the three storage compartments (the refrigerator compartment 5, the freezer/thaw compartment 6, and the ice-making compartment 7).

A damper 12a is disposed in the air passage 12. The control unit 50 (see FIG. 9 described later) controls the rotation speed of the compressor 19 and the cooling fan 14, and controls the opening and closing of the damper 12a, to maintain the temperature of each storage compartment within a predetermined temperature range.

A defrost heater 15 is disposed at the bottom of the cooling chamber 11. The defrost heater 15 is a heater for removing frost and ice that adheres to the cooler 13 and its surroundings. A drain pan 16, a drain tube 17, and an evaporator dish 18 are disposed below the defrost heater 15. These are components for evaporating moisture that is generated during defrosting, etc.

The refrigerator 1 according to this embodiment includes an operation unit 47 (see FIG. 9 described below). A user uses the operation unit 47 to input various commands to the refrigerator 1 (for example, temperature settings for each storage compartment, a quick cooling command, a command to generate an electric field, a command to stop ice making, etc.). The operation unit 47 has a display unit for notifying the user of necessary information.

The refrigerator 1 may be equipped with a wireless communication unit that can be connected to a wireless LAN (local area network) to input various commands from the user's external terminal. The refrigerator 1 may also be equipped with a voice recognition unit for inputting commands by voice from the user.

Figures 2, 3, 5, and 6 are vertical cross-sectional views showing the freezing/thawing compartment 6 of the refrigerator 1 according to this embodiment.

Figures 2 and 5 are views of refrigerator 1 as seen from the front side. Therefore, the left and right sides in Figures 2 and 5 correspond to the left and right sides of refrigerator 1, respectively. Figures 3 and 6 are views of refrigerator 1 as seen from the right side. Therefore, the left and right sides in Figures 3 and 6 correspond to the front and rear sides of refrigerator 1, respectively. In the following drawings showing the configuration of refrigerator 1 (except for Figure 11), the top and bottom of refrigerator 1 correspond to the top and bottom of the drawings.

In Figures 2, 3, 5, and 6, the freezing/thawing chamber 6 is both a freezing chamber and a thawing chamber. That is, the freezing/thawing chamber 6 freezes stored items such as food and keeps them at a freezing temperature range. When an electric field generation command is input to the operation unit 47, an electric field generation process is performed in the freezing/thawing chamber 6, and the frozen stored items are thawed by dielectric heating.

The features of Figures 2, 3, 5, and 6 will be described later.

An air passage 12 is disposed behind and above the freezing/thawing chamber 6. The air passage 12 connects the cooling chamber 11 with the freezing/thawing chamber 6. A plurality of cold air inlet holes 20 are disposed on the top surface of the freezing/thawing chamber 6. The cold air generated by the cooler 13 flows through the air passage 12 and is introduced into the freezing/thawing chamber 6 through the plurality of cold air inlet holes 20. This allows the freezing/thawing chamber 6 to be maintained in the same freezing temperature range as the freezing chamber 8.

A damper 12a is disposed in the air passage 12. The damper 12a is controlled to open and close so that the freezing/thawing chamber 6 is maintained at a predetermined freezing temperature range. This allows the items contained in the freezing/thawing chamber 6 to be frozen and preserved.

A cold air exhaust hole (not shown) is formed on the rear surface of the freezing/thawing compartment 6. After cooling the inside of the freezing/thawing compartment 6, the cold air returns to the cooling compartment 11 via the cold air exhaust hole and an air passage (not shown), and is re-cooled by the cooler 13. That is, in the refrigerator 1 according to this embodiment, the cold air generated by the cooler 13 circulates through the refrigerator 1.

The top, back, two sides, and bottom of the freezing/thawing chamber 6 form the storage space of the freezing/thawing chamber 6. These surfaces are formed by inner surface members 32a, 32b, and 32c molded from an electrically insulating material (e.g., resin). Hereinafter, inner surface members 32a to 32c are collectively referred to as inner surface member 32.

A door 29 is placed at the front opening of the freezing/thawing chamber 6. When the door 29 is closed, the storage space of the freezing/thawing chamber 6 is sealed. A storage case 31 with an open top is placed on the rear side of the door 29 in the freezing/thawing chamber 6. When the door 29 is opened and closed back and forth, the storage case 31 moves back and forth in conjunction with this movement. This movement allows the storage case 31 to be removed from the freezing/thawing chamber 6, making it easier to take in and out stored items such as food.

[1-2. Dielectric heating mechanism for generating an electric field in the storage space]
A dielectric heating mechanism for generating an electric field in the storage space of the freezing/thawing chamber 6 will now be described.

The dielectric heating mechanism can adjust the amount of heat by controlling the output power. If the amount of heat applied to the stored item exceeds the amount of cooling in the freezing/thawing chamber 6, the stored item is heated. If the amount of heat applied to the stored item is less than the amount of cooling in the freezing/thawing chamber 6, the stored item is cooled.

FIG. 9 is a block diagram of the dielectric heating mechanism arranged in the refrigerator 1. As shown in FIG. 9, the dielectric heating mechanism in this embodiment includes a power supply unit 48, an oscillator circuit 22, a matching circuit 23, a first electrode 24, a second electrode 25, and a control unit 50.

The oscillator circuit 22 is an oscillator section that receives power from the power supply section 48 and generates a high-frequency signal. The oscillator circuit 22 is constructed using semiconductor elements, is miniaturized, and is disposed on an electrode holding substrate 52 in an electrode holding area 30 (see Figures 3, 4, 6, and 7) described below. The oscillator circuit 22 and the matching circuit 23 correspond to an electric field forming section for forming a high-frequency electric field to be applied between the first electrode 24 and the second electrode 25.

The first electrode 24 is a flat electrode located at the top (near the top surface) of the freezing/thawing chamber 6. The second electrode 25 is a flat electrode located at the bottom (near the bottom surface) of the freezing/thawing chamber 6. The first electrode 24 and the second electrode 25 are a pair of electrodes arranged facing each other at a predetermined vertical distance (see electrode distance H in Figure 8) in the storage space (thawing space) of the freezing/thawing chamber 6. The first electrode 24 and the second electrode 25 are fixed to an electrode holding substrate 52, which will be described later.

In other words, in the dielectric heating mechanism according to this embodiment, the first electrode 24 and the second electrode 25 are arranged substantially parallel to each other. In this disclosure, "substantially parallel" does not mean strictly parallel, but includes errors resulting from variations in processing accuracy, etc.

The first electrode 24 is disposed near the top surface of the storage space, and the second electrode 25 is disposed near the bottom surface of the storage space, with the storage space in between. The inner surface member 32 covers the matching circuit 23 on the rear side, the first electrode 24 on the top surface, and the second electrode 25 on the bottom surface, thereby preventing damage to these elements due to contact with the stored items.

In this embodiment, a first electrode 24 and a second electrode 25 are disposed near the top and bottom surfaces of the storage space, respectively. However, the present disclosure is not limited to this configuration. It is sufficient that the first electrode 24 and the second electrode 25 are disposed substantially parallel to each other and facing each other across the storage space (thawing space).

For example, the second electrode 25 may be disposed near the top surface of the storage space, and the first electrode 24 may be disposed near the bottom surface of the storage space. The first electrode 24 and the second electrode 25 may be disposed opposite each other in the left-right direction (depth direction in FIG. 1).

The oscillator circuit 22 outputs a high-frequency voltage in the VHF band (40.68 MHz in this embodiment). The high-frequency voltage output by the oscillator circuit 22 creates an electric field between the first electrode 24 and the second electrode 25, resulting in dielectric heating of the stored object, which is a dielectric placed in the storage space.

The first electrode 24, the second electrode 25, and the stored object form a load impedance in the storage space. The matching circuit 23 adjusts the impedance in the matching circuit 23 so that the load impedance matches the output impedance of the oscillation circuit 22.

The matching circuit 23 performs impedance matching to minimize the reflected wave relative to the incident wave. The incident wave is the electromagnetic wave output by the oscillator circuit 22 toward the first electrode 24. The reflected wave is the electromagnetic wave of the incident wave that returns from the first electrode 24 to the oscillator circuit 22.

As shown in FIG. 9, the refrigerator 1 further includes a current detection unit 57 and a cooling mechanism 58 as an abnormality avoidance means. The current detection unit 57 is disposed at the input of the oscillator circuit 22, and detects the value of the current supplied from the power supply unit 48 to the oscillator circuit 22 (specifically, the second amplifier circuit 22c).

The cooling mechanism 58 dissipates heat generated by losses during conversion from DC power to high-frequency power in the oscillator circuit 22 and by consumption of reflected wave power from the electrode holding substrate 52 toward the oscillator circuit 22 due to impedance mismatch. Cooling control, described below, operates the oscillator circuit 22 within a temperature range where heat-induced failures do not occur.

The heat generated per unit time in the oscillator circuit 22 depends on the sum of the input power of the power supply unit 48 and the reflected wave power toward the oscillator circuit 22 minus the incident wave power output from the oscillator circuit 22.

Therefore, the heat generated in the oscillation circuit 22 can be calculated from the output voltage of the power supply unit 48, the current value detected by the current detection unit 57, and the incident wave power value and reflected wave power value in the detection unit 51 described below. The control unit 50 controls the cooling mechanism 58 to exert a predetermined cooling capacity for the calculated heat in the oscillation circuit 22, thereby maintaining the temperature of the oscillation circuit 22 at or below a predetermined value.

The oscillator circuit 22 includes a detector 51. The detector 51 detects the incident wave and the reflected wave, and transmits the respective detection values to the controller 50. The oscillator circuit 22 is electrically connected to the first electrode 24 via the detector 51 and the matching circuit 23. The controller 50 calculates the ratio of the detection value of the reflected wave power to the detection value of the incident wave power as a reflectance, and performs various controls, which will be described later, based on the reflectance.

The control unit 50 may calculate the ratio of the detected value of the reflected wave power to the set power value of the electromagnetic wave output from the oscillator circuit 22 as the reflectivity. The control unit 50 may perform various controls, described later, based only on the detected value of the reflected wave, regardless of the set output value of the electromagnetic wave and the detected value of the incident wave.

The control unit 50 controls the oscillation circuit 22 and the matching circuit 23 based on signals from the operation unit 47, the temperature sensor 49, etc. The control unit 50 includes a processor such as a CPU (Central Processing Unit) and a memory such as a ROM (Read Only Memory). The control unit 50 performs various controls by having the CPU execute a control program stored in the memory.

In addition, an A/D converter (not shown) is provided at the output section of the sensors (detection section 51, temperature sensor 49, current detection section 57) required for controlling the dielectric heating mechanism, or at the input section of the control section 50 for the output signals of these sensors. The A/D converter converts the analog values output from the sensors into digital values and inputs them to the control section 50.

[1-3. Configuration of the circuit board of the dielectric heating mechanism]
It is desirable that the wiring connecting the oscillation circuit 22, the matching circuit 23, and the first electrode 24 be short. Similarly, it is desirable that the wiring connecting the oscillation circuit 22, the matching circuit 23, and the second electrode 25 be short.

For this reason, the electrode holding substrate 52 (see Figures 3, 4, 6, 7, 8, 19A, and 19B) and the first electrode 24 are directly connected without the use of a lead wire or a coaxial cable. Similarly, the electrode holding substrate 52 and the second electrode 25 are directly connected. The electrode holding substrate 52 is disposed in the electrode holding area 30 at the rear of the freezing/thawing chamber 6 and includes a matching circuit 23.

The matching circuit 23 has adjustable inductance and capacitance values. The control unit 50 adjusts the inductance and capacitance values of the matching circuit 23 to control impedance matching by the matching circuit 23. The matching circuit 23 generates heat due to losses in the inductor. Hereinafter, this heat is referred to as waste heat by the matching circuit 23.

In a device including a matching circuit 23 and metal parts such as a first electrode 24, a second electrode 25, and an electromagnetic shield 26 (described later, for example, the top-side electromagnetic shield 26a, the back-side electromagnetic shield 26b, the bottom-side electromagnetic shield 26c, and the door-side electromagnetic shield 26d shown in Figures 2 and 3) arranged around the matching circuit 23, condensation is likely to occur in the freezing temperature range. In this embodiment, the matching circuit 23 is arranged on the electrode holding substrate 52, so that waste heat from the matching circuit 23 is conducted to the device, preventing condensation.

The first electrode 24, the second electrode 25, and the electromagnetic shield 26 described below also generate heat due to electrical losses. However, this heat is usually slight and does not contribute to preventing condensation and frost. Therefore, it is possible to prevent condensation and frost by intentionally increasing the heat generation by using a material with high loss.

If the control unit 50 detects the possibility of condensation or frosting, regardless of whether an electric field is generated in the freezing/thawing chamber 6, it uses waste heat to prevent condensation and frosting. In other words, the control unit 50 prevents condensation and frosting by appropriately operating the oscillation circuit 22 to intentionally generate waste heat.

In order to more accurately determine whether the impedance matching provided by the matching circuit 23 is sufficient, it is desirable to place the detection unit 51 on the electrode holding substrate 52 together with the matching circuit 23. This eliminates the need for lead wires, coaxial cables, and connectors for connecting these between the matching circuit 23 and the detection unit 51, making it possible to simplify the structure.

In addition, by arranging the matching circuit 23, the detection unit 51, and the oscillator circuit 22 all on a single board, it is possible to further reduce transmission loss due to lead wires and coaxial cables, and improve the accuracy of impedance matching.

For example, the oscillator circuit 22 and the matching circuit 23 may be arranged on separate boards and electrically connected by lead wires or a coaxial cable. In this case, these elements are arranged rationally by making effective use of the space inside the refrigerator, for example by installing the oscillator circuit 22 in the machine room 10 which has a large amount of free space. However, for impedance matching including the coaxial cable, it is preferable to arrange the oscillator circuit 22 and the detection unit 51 on a single board.

[1-4. System structure of dielectric heating mechanism]
In the dielectric heating mechanism according to this embodiment, the first electrode 24 and the second electrode 25 face each other substantially parallel to each other with a predetermined gap (see electrode gap H in FIG. 8 ). This makes the electric field uniform in the storage space of the freezing/thawing chamber 6. In this dielectric heating mechanism, the electrode gap H is maintained as described below.

Figure 8 shows the electrode holding area 30 on the rear side of the freezing/thawing compartment 6. Figure 8 is a schematic diagram of the electrode holding area 30 as viewed from the rear side of the freezing/thawing compartment 6. Therefore, the left and right sides in Figure 8 correspond to the right and left sides, respectively, of the refrigerator 1 when viewed from the front side.

As shown in FIG. 8, a first electrode 24 is disposed at the top of the freezing/thawing chamber 6 (near the top surface), and a second electrode 25 is disposed at the bottom of the freezing/thawing chamber 6 (near the bottom surface).

The first electrode 24 has positive electrode terminal 24a, positive electrode terminal 24b, and positive electrode terminal 24c. The positive electrode terminals 24a to 24c are arranged side by side in the left-right direction near the center of the rear end of the first electrode 24. Each of the positive electrode terminals 24a to 24c protrudes from the rear end of the first electrode 24 and has a shape that is bent upward or downward at a right angle.

Similarly, the second electrode 25 has cathode terminal 25a, cathode terminal 25b, and cathode terminal 25c. Cathode terminals 25a to 25c are arranged side by side in the left-right direction near the center of the rear end of the second electrode 25. Each of cathode terminals 25a to 25c protrudes from the rear end of the second electrode 25 and has a shape that is bent upward or downward at a right angle.

The first electrode 24 and the second electrode 25 are fixed to the upper and lower parts, respectively, of the electrode holding substrate 52. The matching circuit 23 and the detection unit 51 are disposed on the electrode holding substrate 52. Therefore, the first electrode 24 and the second electrode 25 are held at a predetermined distance (see electrode distance H in Figure 8) by the electrode holding substrate 52.

Since the matching circuit 23 and the like are arranged on the electrode holding substrate 52, the rigidity of the electrode holding substrate 52 is improved by the copper foil wiring pattern. Therefore, the electrode holding substrate 52 can cantilever-support the first electrode 24 and the second electrode 25 at a predetermined interval (see electrode interval H in FIG. 8). As described above, the oscillator circuit 22 and the like may also be arranged on the electrode holding substrate 52.

The positive electrode terminals 24a to 24c of the first electrode 24 are connected to a connection terminal (not shown) on the positive side of the matching circuit 23. The cathode terminals 25a to 25c of the second electrode 25 are connected to a connection terminal (not shown) on the cathode side of the matching circuit 23. The positive electrode terminals 24a to 24c and the cathode terminals 25a to 25c are connected to the connection terminals of the matching circuit 23 by surface contact with a specified contact area to ensure reliability even when a large current flows.

In this embodiment, in order to ensure a reliable connection through surface contact, the flat terminals are connected to each other by screwing. The connection between the terminals is not limited to a connection by screwing, so long as a reliable connection is possible. However, in order to prevent condensation and frosting by utilizing the waste heat mentioned above, it is desirable to have a connection between the terminals with excellent thermal conductivity.

As described above, the electrode holding substrate 52, which is an electrode holding mechanism, is disposed behind the freezing/thawing chamber 6. The electrode holding substrate 52 positions the first electrode 24 and the second electrode 25 substantially parallel to each other.

In this embodiment, the freezing/thawing chamber 6 is equipped with a high-frequency heating module 53 (see, for example, FIG. 4). The high-frequency heating module 53 is a module that integrates a first electrode 24, a second electrode 25 that is parallel to the first electrode 24, and an electrode holding substrate 52 that holds the first electrode 24 and the second electrode 25. This makes it easy to hold the first electrode 24 and the second electrode 25 approximately parallel.

[1-5. Anomaly detection in dielectric heating mechanism]
Anomalies in the dielectric heating mechanism include temperature anomalies, sparks, and circuit failures. Temperature anomalies refer to an abnormal rise in temperature of the oscillation circuit 22 and the matching circuit 23 due to the operating conditions and the surrounding environment. The high-frequency power input to the matching circuit 23 is converted into a high-frequency electric field between the first electrode 24, which is an oscillation electrode, and the second electrode 25, which is an opposing electrode. The stored object is dielectrically heated by this high-frequency electric field.

A portion of the incident wave power input to the first electrode 24 is reflected without acting on the stored object, becoming reflected wave power. This reflected wave power is consumed as heat in the equivalent series resistance of the capacitor included in the matching circuit 23 and in the resistance component of the inductor included in the matching circuit 23, raising the temperature of the matching circuit 23. In this embodiment, the matching circuit 23 corresponds to the matching section.

The temperature of the components included in the matching circuit 23 may deviate from its operating temperature range due to the combination of heat generation from the matching circuit 23 and external factors that increase the ambient temperature. External factors that increase the ambient temperature include opening and closing the freezer/thaw chamber 6 and defrosting.

For this reason, in this embodiment, a temperature sensor 49 is disposed in the matching circuit 23. When the temperature of the matching circuit 23 detected by the temperature sensor 49 exceeds a predetermined threshold, the control unit 50 causes the oscillator circuit 22 to stop high-frequency output, thereby allowing the matching circuit 23 to operate within a safe temperature range.

Since the temperature sensor is placed away from the actual heat generating element, the output signal from the temperature sensor may not have a sufficient response speed. Therefore, the temperature characteristics of the capacitors and inductors included in the matching circuit 23 may be measured from the reflectance obtained based on the information from the detection unit 51, and the response speed of the output signal from the temperature sensor may be corrected.

The dielectric heating mechanism includes an oscillator circuit 22, a matching circuit 23, a detector 51, and a controller 50. The oscillator circuit 22 supplies high-frequency power to the electrodes (first electrode 24, second electrode 25). The matching circuit 23 performs impedance matching of the electrodes.

The detection unit 51 is connected between the oscillation circuit 22 and the matching circuit 23, and measures the incident wave power output from the matching circuit 23 to the electrode and the reflected wave power returning to the oscillation circuit 22. The control unit 50 controls the oscillation circuit 22 and the matching circuit 23 based on the incident wave power and the reflected wave power, and detects abnormalities in the incident wave power or the reflected wave power. In other words, the control unit 50 functions as an abnormality detection means.

A spark refers to a momentary short circuit state that occurs between the first electrode 24 or the second electrode 25 and the electromagnetic shield 26, between the first electrode 24 or the second electrode 25 and a stored object, etc. The control unit 50 detects sparks based on information obtained from the detection unit 51, and if a spark is detected, it immediately stops the oscillation circuit 22.

The detection unit 51 is a sensor that outputs a voltage whose magnitude corresponds to the input high-frequency power. In this embodiment, the VHF (Very High Frequency) band of 30 MHz to 300 MHz is used as the fundamental wave of the oscillator circuit 22. For this reason, the detection unit 51 is also designed to detect high-frequency power in the VHF band.

On the other hand, the detection unit 51 is also sensitive to high-frequency noise of several to several hundred MHz contained in the spark. Therefore, when high-frequency noise from the spark reaches the detection unit 51 via a coaxial cable 56 (cables 56a and 56b, described below with reference to Figures 19A and 19B), the detection unit 51 outputs the sum of the output voltage corresponding to the fundamental wave of the oscillator circuit 22 and the output voltage corresponding to the high-frequency noise.

The sum of the power of high-frequency noise is very large compared to the fundamental wave of the oscillator circuit 22, which contains a single frequency. For this reason, when a spark occurs, the output voltage of the detector 51 rises to a value that would not be possible under normal operation.

Unlike other circuit abnormalities, the voltage rise in the detection unit 51 due to a spark also occurs on the incident side of the detection unit 51. The control unit 50 can more reliably detect the occurrence of a spark by using information on the incident wave power or information on the incident wave power and reflected wave power.

The detection unit 51 is exposed to noise even under normal circumstances, and may accidentally output an abnormal voltage without the occurrence of a spark. When this abnormal voltage exceeds a predetermined threshold, the oscillator circuit 22 stops outputting the high-frequency voltage and stops the operation of the dielectric heating mechanism, causing frequent abnormal stops. In this case, not only does it increase the burden on the user, but it can also significantly impair the quality of the stored items. For this reason, it is necessary to detect the occurrence of sparks more reliably.

Figures 20A and 20B show the transition of the A/D converted value of the incident wave power or the reflected wave power. This A/D converted value is a digital value obtained by converting the analog signal output from the detection unit 51, for example, by an A/D converter connected to the output unit of the detection unit 51. The control unit 50 refers to the A/D converted values obtained from the several samplings immediately prior to the time of abnormality detection, and performs spark detection based on the number of these values that exceed a predetermined threshold value.

As shown in FIG. 20A, the control unit 50 does not determine that a spark has occurred if the number is 1, and as shown in FIG. 20B, it determines that a spark has occurred if the number is 2 or more.

The above threshold for determining whether a spark has occurred can be freely set by the designer according to the circumstances of the noise occurrence, so long as it is 2 or more. This makes it possible to distinguish between accidental noise and noise caused by sparks, and to perform spark detection more reliably.

The load impedance fluctuates due to the momentary short circuit that occurs when a spark occurs, and the input current to the oscillator circuit 22 fluctuates significantly accordingly. Taking advantage of this, as shown in FIG. 20C, the control unit 50 may detect a spark when the incident wave power or the incident wave power and the reflected wave power exceed their respective predetermined thresholds, and the current value supplied to the oscillator circuit 22 detected by the current detection unit 57 exceeds another predetermined threshold. This can improve the accuracy of spark detection.

A circuit fault refers to a permanent short circuit between the first electrode 24 or the second electrode 25 and the electromagnetic shield 26, a short circuit in the matching circuit 23, a fault in the manipulator which is the impedance adjustment means in the matching circuit 23, and a short circuit or break in a high-frequency transmission line such as the coaxial cable 56 (see Figures 19A and 19B described below).

In either state, the load impedance is significantly different from that in the normal state. This makes it difficult for the matching circuit 23 to match the impedance, and the reflectance increases. The resulting strong temperature stress may cause the oscillator circuit 22 to fail.

In the case of a circuit failure due to a short circuit, there is a risk of localized heat generation due to the short circuit current. For the above reasons, it is necessary to detect the circuit failure, stop the oscillator circuit 22, and notify the user to request repairs.

If a short circuit or break occurs in a high-frequency-related circuit, the control unit 50 fixes the impedance between the electrodes and the matching circuit 23 to the failure mode impedance, regardless of the state of the matching circuit 23 and the stored object. The control unit 50 can immediately detect a circuit failure by detecting a sudden deterioration in reflectivity when the matching circuit 23 has not been controlled immediately before.

However, even during normal operation, reflectance can take any value from 0% to 100%, making it difficult to determine the reflectance using a threshold value. During the defrosting operation, reflectance is constantly changing, making it difficult to determine the reflectance using the rate of change over time.

Graph (a) in Figure 21 shows the transition of reflectance when a circuit failure is detected during a period in which there is no change in reflectance due to control by the matching circuit 23. In graph (a) in Figure 21, the thick solid line shows the reflectance calculated based on the A/D converted value obtained from the detection unit 51. The dashed dotted line shows the average value of the reflectance calculated based on the A/D converted values obtained by sampling the most recent few times. The two dotted lines show the upper and lower limits of the normal range of reflectance centered on the average reflectance.

Graph (b) in Figure 21 shows the timing of detection of a circuit fault. The rising edge of graph (b) in Figure 21 indicates the time when an abnormality is detected. If no circuit abnormality occurs, the most recent reflectance shows a value similar to the previous few reflectances, so the reflectance falls within the normal range.

If a circuit abnormality occurs, the reflectance increases suddenly and deviates from the normal range. The control unit 50 detects a circuit failure by detecting the point in time when the reflectance deviates from the normal range, not immediately after the impedance adjustment is performed by the matching circuit 23.

If the manipulator of the matching circuit 23 fails, or if a circuit failure has already occurred, the impedance does not fluctuate in response to the control signal from the control unit 50. Therefore, the reflectance hardly changes. Figure 22 shows the change in reflectance when the impedance adjustment in the matching circuit 23 was performed immediately before.

Graph (a) in FIG. 22 shows the switching timing of the control signal to the matching circuit 23. Graph (b) in FIG. 22 shows the change in reflectance from the control signal input to the matching circuit 23.

The time from when the matching circuit 23 receives the control signal to when it actually performs impedance adjustment and the reflectance finishes changing is almost constant each time. Therefore, the control unit 50 records the change in reflectance during the predetermined reflectance change acquisition time Rt from the input of the control signal to the matching circuit 23, that is, the difference between the maximum and minimum reflectance values, as ΔΓ.

If the reflectance change ΔΓ is equal to or less than a predetermined threshold value after the reflectance change acquisition time Rt has elapsed, the control unit 50 determines that an abnormality has occurred, since the reflectance has not changed despite the impedance adjustment in the matching circuit 23. As shown in FIG. 22, the control unit 50 detects a circuit failure by making a determination based on a comparison of the reflectance change ΔΓ immediately after the impedance adjustment in the matching circuit 23 with the threshold value.

The control unit 50 needs to detect sparks, circuit failures, and temperature abnormalities, safely shut down the dielectric heating mechanism, and identify the type of abnormality that has occurred in order to prompt the user to improve operating conditions and perform repairs.

FIG. 23 shows the flow of abnormality determination. As shown in FIG. 23, first, the control unit 50 determines whether the temperature of the matching circuit 23 is equal to or lower than a predetermined threshold value (step S201). If the temperature of the matching circuit 23 is higher than the threshold value (No in step S201), the control unit 50 determines that an abnormal temperature of the matching circuit 23 has been detected (step S202). If the temperature of the matching circuit 23 is equal to or lower than the threshold value (Yes in step S201), the control unit 50 determines that the temperature is within the normal range and moves the process to step S203.

In step S203, to determine whether a spark has been detected, the control unit 50 calculates the number of values of incident wave power obtained during a predetermined period of time until the time of abnormality detection that exceed a predetermined threshold (see FIG. 20B). Alternatively, the control unit 50 may calculate the number of values of both incident wave power and reflected wave power obtained during a predetermined period of time until the time of abnormality detection that exceed another predetermined threshold.

Specifically, the control unit 50 performs this calculation based on the A/D conversion value of the incident wave power, or the A/D conversion values of both the incident wave power and the reflected wave power, obtained by sampling a predetermined number of times up to the timing of abnormality detection.

If these values do not exceed the threshold value a predetermined number of times (e.g., twice) (No in step S203), the control unit 50 determines that a spark has been detected (step S204).

If these values exceed the threshold value a predetermined number of times (e.g., twice) or more (Yes in step S203), the control unit 50 determines whether or not it is immediately after impedance adjustment in the matching circuit 23 (step S205).

If it is within a predetermined time since the impedance adjustment was performed (Yes in step S205), the control unit 50 records the maximum and minimum reflectance values within the predetermined time (step S206) and calculates the reflectance variation ΔΓ (step S210). If the reflectance variation ΔΓ is equal to or less than a predetermined threshold (No in step S207), the control unit 50 determines that the matching circuit 23 is faulty (step S209).

On the other hand, if a predetermined time has elapsed since impedance adjustment was performed in the matching circuit 23 (No in step S205), in step S211, the control unit 50 refers to the A/D converted values of the incident wave power and the reflected wave power for the last few times and calculates the average value of the reflectivity for the last few times (see Figure 22).

In step S212, the control unit 50 calculates the difference between the reflectance value at the time of the abnormality detection and the average value of the past several reflectance values before the abnormality detection was performed. If the difference exceeds a predetermined threshold value (No in step S208), the control unit 50 determines that a failure of the matching circuit 23 has been detected (step S209).

In this embodiment, as described above, the detection method is different depending on whether it is within a predetermined time after the impedance adjustment in the matching circuit 23 or after a predetermined time has elapsed since the impedance adjustment.

If any abnormality is detected, the high frequency output of the oscillator circuit 22 is temporarily stopped, and depending on the type of abnormality, the system will automatically recover, the system will be stopped, or the details of the failure will be displayed to the user. Note that it is preferable to judge in the following order: temperature abnormality, spark detection, and circuit failure detection, but it is also possible to judge in a different order.

[1-6. Structure of the freezing/thawing compartment]
As described above, the main body 2 of the refrigerator 1 is an insulated box body composed of the outer box 3 formed of a steel plate, the inner box 4 made of resin, and the insulating material 40. The insulating material 40 is, for example, rigid urethane foam, and is foamed and filled in the space between the outer box 3 and the inner box 4.

As shown in Figures 2 and 3, the freezing/thawing chamber 6 has an inner surface member 32a arranged inside the insulating material 40 as an outer frame. An electromagnetic wave shield 26 is arranged around the freezing/thawing chamber 6. The electromagnetic wave shield 26 includes a top-side electromagnetic wave shield 26a, a back-side electromagnetic wave shield 26b, a bottom-side electromagnetic wave shield 26c, and a door-side electromagnetic wave shield 26d, and surrounds the freezing/thawing chamber 6 to prevent electromagnetic waves from leaking to the outside.

The inner surface member 32a separates the electrode holding area 30 from the freezing/thawing chamber 6. The rear electromagnetic shield 26b is disposed on the rear side of the inner surface member 32a. The rear electromagnetic shield 26b separates the interior of the freezing/thawing chamber 6 from the electrode holding substrate 52, which includes the matching circuit 23 and the like. This makes it possible to prevent the freezing/thawing chamber 6 and the electrode holding substrate 52 from affecting each other in terms of impedance and electric field.

　Plate-shaped inner surface members 32b and 32c are arranged at the top and bottom of the space surrounded by inner surface member 32a, respectively. A first electrode 24 is arranged on the top surface of inner surface member 32b, and a second electrode 25 is arranged on the bottom surface of inner surface member 32c.

The inner surface members 32b and 32c are held at a predetermined distance (see electrode spacing H in Figures 2 and 3). In other words, the first electrode 24 and the second electrode 25 are held in a substantially parallel state by the electrode holding substrate 52 and the inner surface member 32.

Due to variations in the foaming of the foamed insulation 40, the top and bottom surfaces of the freezing/thawing chamber 6 may not be parallel. However, with the above-described configuration, the first electrode 24 and the second electrode 25 are kept approximately parallel without being affected by the outer box 3.

FIG. 4 is a vertical cross-sectional view showing how the freezing/thawing compartment 6 is installed in the main body 2 of the refrigerator 1. FIG. 4 is a view of the refrigerator 1 as seen from the right side. Therefore, the left and right sides in FIG. 4 correspond to the front and rear sides of the refrigerator 1, respectively.

The high-frequency heating module 53 is pre-assembled before the manufacturing process. As shown in FIG. 4, in the manufacturing process, first, the high-frequency heating module 53 is inserted into the outer box 3 of the refrigerator 1. Next, the door unit including the door 29, the door-side electromagnetic shield 26d, the gasket 36, and the storage case 31 is inserted into the high-frequency heating module 53. This completes the refrigerator 1.

This embodiment may also have the configurations shown in Figures 5, 6, and 7. Like Figure 4, Figure 7 is a vertical cross-sectional view showing how the freezing/thawing compartment 6 is incorporated into the main body 2 of the refrigerator 1. Therefore, the left and right sides in Figure 7 are the same as those in Figure 4. In Figures 5 to 7, the outer box 3, inner box 4, insulating material 40, inner surface member 32, and electromagnetic wave shield 26 are the same as those in Figures 2 and 3.

As shown in Figures 5 to 7, flat inner surface members 32b and 32c are arranged horizontally at the top and bottom of the space surrounded by inner surface member 32a. A first electrode 24 is arranged on the top surface of inner surface member 32b, and a second electrode 25 is arranged on the bottom surface of inner surface member 32c.

The front sides of the inner surface members 32b and 32c are fixed by the support 54. The back sides of the inner surface members 32b and 32c are fixed by the electrode holding substrate 52 and the inner surface member 32c. This keeps the first electrode 24 and the second electrode 25 in a substantially parallel state.

The inner surface members 32b and 32c are held at a predetermined distance (see electrode spacing H in Figures 5 to 7), so that the first electrode 24 and second electrode 25 are held in a substantially parallel state by the electrode holding substrate 52, the support 54, and the inner surface member 32.

The inner surface member 32 is preferably made of a material with a thermal conductivity equal to or less than 10 W/(m·k) of common industrial ceramic materials that is unlikely to cause condensation even in the freezer compartment 8. In this embodiment, the inner surface member 32 is made of a resin such as polypropylene, ABS (Acrylonitrile-Butadiene-Syrene), or polycarbonate.

To reduce heat capacity, the electromagnetic wave shield 26 is configured to be thinner than the inner surface member 32. This makes it possible to prevent condensation on the electromagnetic wave shield 26 and the inner surface member 32 that contacts the electromagnetic wave shield 26.

In this way, according to this embodiment, the electrode holding mechanism allows the first electrode 24 and the second electrode 25 to be arranged approximately parallel to each other with a predetermined distance between them (see, for example, electrode distance H in FIG. 5). Therefore, in the dielectric heating mechanism of the freezing/thawing chamber 6, bias in the high-frequency electric field on the electrode surface is suppressed, and the high-frequency electric field is made uniform. As a result, the stored items (frozen products) can be heated more uniformly.

According to this embodiment, the refrigerator 1 is completed by inserting the high-frequency heating module 53, which is a pre-assembled unit, into the outer box 3. In other words, the refrigerator 1 can be manufactured through a simple manufacturing process.

[1-7. Electromagnetic wave shielding mechanism]
As described above, in the refrigerator 1 according to this embodiment, it is possible to dielectrically heat a stored object (dielectric) by placing it between the first electrode 24 and the second electrode 25 in the freezing/thawing compartment 6. Therefore, in order to prevent electromagnetic waves from leaking outside the freezing/thawing compartment 6, the refrigerator 1 according to this embodiment is provided with an electromagnetic wave shielding mechanism that surrounds the freezing/thawing compartment 6.

As shown in Figures 2, 3, and 5, a top-side electromagnetic wave shield 26a is disposed above the top surface of the freezing/thawing chamber 6. The top-side electromagnetic wave shield 26a is disposed on the upper surface of the inner surface member 32a that constitutes the top surface of the freezing/thawing chamber 6, and is disposed so as to cover the top surface of the freezing/thawing chamber 6. The top-side electromagnetic wave shield 26a has multiple openings. This reduces the area of the portion of the top-side electromagnetic wave shield 26a that faces the first electrode 24.

These openings have a slit shape with the longitudinal direction being the front-to-rear direction of the refrigerator 1. This allows the magnetic field (or current) flowing forward from the positive terminals 24a-24c to pass smoothly over the top-side electromagnetic shield 26a. This suppresses leakage magnetic fields from diffusing to the surrounding area. The inventors analyzed this through electromagnetic wave simulations.

This configuration suppresses the generation of unnecessary electric fields between the top-side electromagnetic wave shield 26a and the first electrode 24. The top-side electromagnetic wave shield 26a may have a mesh structure with many openings.

The top electromagnetic wave shield 26a may be placed inside the refrigerator compartment 5 located above the freezer/thaw compartment 6. However, since a partial compartment and a chilled compartment are often placed in the refrigerator compartment 5, the top surfaces of the partial compartment and the chilled compartment may also be used as the electromagnetic wave shield.

The rear electromagnetic shield 26b is arranged to cover the electrode holding area 30 arranged on the rear side of the freezing/thawing chamber 6. The rear electromagnetic shield 26b prevents the electric field generated between the first electrode 24 and the second electrode 25 and the high-frequency noise generated in the matching circuit 23 from affecting the control of the cooling fan 14 and the damper 12a. An electromagnetic shield (not shown) is also arranged on the side of the freezing/thawing chamber 6.

Next, the door-side electromagnetic shield 26d arranged on the door 29 will be described. The door 29 is attached to the body of the refrigerator 1 and covers the front opening of the freezing/thawing compartment 6 in an openable and closable manner. For this reason, in a configuration in which the door-side electromagnetic shield 26d is connected to the grounded part of the body of the refrigerator 1 by a wired path, the wired path repeatedly expands and contracts as the door 29 is opened and closed. In other words, such a configuration is not preferable because it can cause metal fatigue in the wired path to break.

Generally, to prevent leakage of electromagnetic waves, it is necessary to make the gap between the door-side electromagnetic shield 26d and the cross rail 21 (see Figure 1) narrower than 1/4 of the wavelength λ of the electromagnetic waves when the door 29 is closed. The cross rail 21 is the electromagnetic shield on the main body side that is connected to the outer box 3 and grounded. In this embodiment, this gap is made even smaller (for example, within 30 mm).

When the door 29 is closed, the door-side electromagnetic shield 26d comes close to the grounded cross rail 21. This configuration provides the same effect as grounding by wired path. By making the end of the door-side electromagnetic shield 26d bent toward the main body of the refrigerator 1, the door-side electromagnetic shield 26d can be easily brought close to the cross rail 21.

The door-side electromagnetic shield 26d may be placed close to components other than the cross rail 21, such as the top-side electromagnetic shield 26a and the bottom-side electromagnetic shield 26c.

Next, we will explain the connection to the electromagnetic shield and ground to other circuits.

Figure 10 is a schematic circuit diagram of the AC/DC converter in the dielectric heating mechanism. In this circuit, the AC voltage from the AC commercial power source ACV is rectified by the bridge diode BD1 and rectifier capacitor C0 and converted into a DC voltage. This DC voltage is input to the DC/DC converter.

The DC/DC converter shown in FIG. 10 is a flyback type switching power supply circuit. However, the present disclosure is not limited to this, and any switching power supply that uses a transformer, such as a forward type, push-pull type, or half-bridge type, may be used. FIG. 10 shows only the main circuit components, and omits the noise filter, power supply control circuit, and protection circuit.

As shown in Figure 10, the AC voltage from the AC commercial power supply ACV is rectified and smoothed by bridge diode BD1 and rectifier capacitor C0 and converted into a DC voltage. This DC voltage is called the primary DC power supply DCV0 (or first power supply unit). The zero volt reference potential of the primary DC power supply DCV0 is called the primary ground GND0 (or first ground).

The primary DC power supply DCV0 is applied to the primary winding P1 of the switching transformer T1. The switching transformer T1 operates at a switching frequency of several tens of kHz using the field effect transistor Q1.

The power stored in the primary winding P1 is transferred to the electrically insulated secondary winding S1 by electromagnetic induction, and is rectified by the secondary rectifier diode D1 and secondary rectifier capacitor C1. This outputs the secondary DC power supply DCV1 (second power supply unit).

The secondary winding S2 has an output section disposed between its two ends. The output voltage of the secondary winding S2 is rectified by the secondary rectifier diode D2 and the secondary rectifier capacitor C2. This outputs a secondary DC power supply DCV2 (second power supply section) with a lower voltage than the secondary DC power supply DCV1. The zero volt reference potential of the secondary DC power supplies DCV1 and DCV2 is called the secondary ground GND1 (or second ground).

The primary DC power supply DCV0 is applied to the primary winding P2 of the switching transformer T2 as well as to the switching transformer T1. The switching transformer T2 operates at a switching frequency of several tens of kHz using the field effect transistor Q2.

The power stored in the primary winding P2 is transferred to the electrically insulated secondary winding S3 by electromagnetic induction and is rectified by the secondary rectifier diode D3 and secondary rectifier capacitor C3. This outputs a secondary DC power supply DCV3 (third power supply unit). The zero volt reference potential of the secondary DC power supply DCV3 is called the secondary ground GND2 (or third ground).

In the switching transformer T1, the insulation between the primary winding P1 and the secondary winding S1 has a performance equal to or higher than the basic insulation specified in the Electrical Appliance and Material Safety Act of Japan or the IEC (International Electrotechnical Commission) standards. The same applies to the insulation between the primary winding P2 and the secondary winding S3 in the switching transformer T2.

In the oscillator circuit 22, the oscillator source 22a outputs micropower having a frequency of 40.68 MHz, which is assigned to the ISM band (Industrial Scientific and Medical Band), using a crystal oscillator or the like. This micropower is amplified by the first amplifier circuit 22b, and further amplified by the second amplifier circuit 22c. The power amplified by these amplifier circuits is output to the matching circuit 23. Note that the output frequency of the oscillator source 22a is not limited to 40.68 MHz.

In this embodiment, the secondary side DC power supply DCV1 is supplied to the second amplifier circuit 22c of the oscillator circuit 22. The secondary side DC power supply DCV2 is supplied to the oscillation source 22a, the first amplifier circuit 22b, the detector 51, and the matching circuit 23 of the oscillator circuit 22. The secondary side DC power supply DCV3 is supplied to the controller 50.

As a result, the circuit system in which the secondary ground GND1 is the zero volt reference potential includes the oscillator circuit 22, the detector 51, the matching circuit 23, and the second electrode 25. The circuit system in which the secondary ground GND2 is the zero volt reference potential includes the control unit 50. The control unit 50 may be connected to the secondary DC power supply DCV2 and the secondary ground GND1.

The second electrode 25 has the same potential as the secondary ground GND1. It is desirable that the electromagnetic shield 26 is insulated from the second electrode 25 or is connected at a certain distance from the second electrode 25. This reduces the electric field and magnetic field applied to the electromagnetic shield, and suppresses leakage of the electric field and magnetic field to the outside. In other words, the effectiveness of the electromagnetic shield is improved.

　Explains how to improve the effectiveness of electromagnetic shielding.

The first method is to not connect the electromagnetic shield 26 to any of the primary ground GND0, secondary ground GND1, or secondary ground GND2. This method is particularly effective when the total area or volume of the electromagnetic shield is equal to or greater than a predetermined value. This method reduces the adverse effects of noise, such as high-frequency noise leaking to the outside through the ground line.

The second method is to connect the electromagnetic shield 26 to the primary ground GND0. The primary ground GND0 is usually connected to the metal outer casing 3 and has a large ground surface area. Therefore, the zero volt reference potential of the primary ground GND0 is the most stable. This method not only improves the effectiveness of the electromagnetic shield 26, but also reduces malfunctions due to noise.

The third method is to connect the electromagnetic shield 26 to the secondary ground GND2. With this method, the second electrode 25 and the electromagnetic shield 26 are insulated in two stages by the switching transformers T1 and T2. This makes it difficult for high-frequency noise to leak from the first electrode 24 to the electromagnetic shield 26, and stabilizes the electric field generated between the first electrode 24 and the second electrode 25.

The fourth method is to connect the secondary ground GND1 at a location some distance away from the second electrode 25 (at least outside the electromagnetic shield 26). This method provides a certain degree of shielding effect and makes it difficult for high-frequency noise to leak from the first electrode 24 to the electromagnetic shield 26. Therefore, the electric field generated between the first electrode 24 and the second electrode 25 is stable.

The effectiveness of the above methods for improving the shielding effect may vary depending on the system structure and wiring. Therefore, it is necessary to select the most suitable method from these methods, taking into consideration the efficiency of electric field generation between the first electrode 24 and the second electrode 25 and the effectiveness of the electromagnetic wave shielding.

In the refrigerator 1 according to this embodiment, the outer box 3 made of steel plate functions as an electromagnetic wave shield. This prevents electromagnetic waves inside the refrigerator 1 from leaking to the outside.

In the above electromagnetic shielding configuration, malfunctions and radio wave leakage can become a problem due to normal mode noise generated within the system and common mode noise conducted to the secondary ground GND1 or secondary ground GND2. In particular, common mode noise is often superimposed on the cable that conducts the high-frequency output generated by the oscillator circuit 22 and radiated from the surface of the cable.

For this reason, coaxial cables are usually used for transmitting high-frequency output. However, common mode noise can also be transmitted to the outside of the outer conductor, which is supposed to act as a shield within a coaxial cable.

FIGS. 19A and 19B show a specific configuration for preventing malfunction and radio wave leakage due to common mode noise. In FIG. 19A, electrode holding substrate 52 including matching circuit 23 and the like is placed away from oscillator circuit 22 (not shown in FIG. 19A) including detection section 51. Coaxial cable 56a electrically connects electrode holding substrate 52 and detection section 51. The outer shell of outer box 3 of refrigerator 1 is made of a metal material, and coaxial cable 56a is wired inside outer box 3.

This configuration prevents radio waves generated by common mode noise conducted to the coaxial cable 56a from leaking to the outside. Note that the multiple types of coaxial cables shown below are collectively referred to as coaxial cables 56. In this embodiment, the coaxial cables 56 correspond to the connecting wires.

As shown in FIG. 19A, the coaxial cable 56a is wired so that it contacts the inside of the outer box 3 at at least one point. The outer box 3 has a large surface area and a reference potential that is approximately equal to the potential of the primary ground GND0 (see FIG. 10). Therefore, common mode noise conducted to the coaxial cable 56a can escape to the primary ground GND0.

As shown in FIG. 19B, the coaxial cable 56b is wired inside the outer box 3, while the coaxial cable 56b is wired so as not to come into contact with the inside of the outer box 3.

In order to prevent malfunctions and radio wave leakage, either the configuration in FIG. 19A or the configuration in FIG. 19B is selected depending on the path of the common mode noise that is conducted through the coaxial cable 56 and the outer casing 3. It is necessary to design so that the positional relationship between the coaxial cable 56 and the outer casing 3 is reliably the configuration in FIG. 19A or the configuration in FIG. 19B. It is not desirable to have a design where it is unclear which will be the case during mass production.

[1-8. Configuration of the first electrode and the second electrode and thawing performance according to said configuration]
Fig. 11 is a plan view of the first electrode 24 and the second electrode 25 of the freezing/thawing compartment 6 as viewed from above. The left side, right side, upper side, and lower side in Fig. 11 correspond to the left side, right side, rear side, and front side of the refrigerator 1, respectively.

As shown in FIG. 11, the size of the first electrode 24 is smaller than that of the second electrode 25. The first electrode 24 has an electrode hole 41, and the second electrode 25 has an electrode hole 42. The electrode holes 41 and 42 correspond to the first electrode hole and the second electrode hole, respectively.

Each of the electrode holes 41, 42 has a plurality of through holes in the shape of elongated slits. In the electrode holes 41, 42, each of the plurality of through holes is arranged so that the longitudinal direction of the through hole is along the front-rear direction of the refrigerator 1. The plurality of through holes are also arranged in the short direction of the through hole, i.e., in the left-right direction of the refrigerator 1. The plurality of through holes in the electrode hole 41 have the same size and pitch as the plurality of through holes in the electrode hole 41.

This electrode shape makes it easier for high-frequency current input from the rear side of the freezing/thawing chamber 6, where the positive terminals 24a-24c (see FIG. 8) of the first electrode 24 are located, to flow forward. As a result, the electric field generated between the first electrode 24 and the second electrode 25 becomes stronger.

The through hole of electrode hole 41 does not completely overlap with the through hole of electrode hole 42 when viewed from above, but is positioned so that it is shifted by about half the width in the short direction (left and right direction) of the through holes.

In this embodiment, electrode holes 41 having multiple through holes are formed on the electrode surface of the first electrode 24, so that the area where a strong electric field is formed on the electrode surface of the first electrode 24 is uniformly distributed. In other words, the edge of the opening in the electrode hole 41 becomes an electric field concentration area where the electric field is concentrated on the electrode surface of the first electrode 24. As a result, uniform dielectric heating can be performed on the stored item.

The shape and arrangement of electrode holes 41, 42 shown in FIG. 11 are examples. The shape and arrangement of electrode holes 41, 42 are designed as appropriate depending on the specifications, configuration, efficiency, manufacturing costs, etc. of the refrigerator. For example, the shape of the through holes of electrode holes 41, 42 may be a perfect circle. In this case, similar to the above, it is desirable that the through hole of electrode hole 41 does not completely overlap with the through hole of electrode hole 42 when viewed from above, but is shifted in either direction by about half the diameter.

The first electrode 24 according to the present disclosure is not limited to the above configuration, and may, for example, have at least one opening. The edge of the opening becomes an electric field concentration region where the electric field is concentrated on the electrode surface of the first electrode 24. In other words, the first electrode 24 according to the present disclosure may be configured so that the electric field concentration region is dispersed on the electrode surface.

Furthermore, the second electrode 25 according to the present disclosure is not limited to the above configuration, but may have an opening for forming a desired electric field between the two electrodes.

The electrode holding substrate 52 is configured to reliably hold the first electrode 24 and the second electrode 25 at a predetermined distance (see, for example, electrode spacing H in FIG. 8). The predetermined distance (see, for example, electrode spacing H in FIG. 8) is shorter than the dimension of the long side of the first electrode 24 (dimension D in FIG. 11). If the first electrode 24 is circular, it is desirable that the electrode spacing H be shorter than its diameter, and if it is elliptical, it is desirable that the electrode spacing H be shorter than its major axis.

Figure 12 shows the relationship between the electrode spacing H (see, for example, Figure 8) and the electric field strength between the two electrodes. As shown in Figure 12, the wider the electrode spacing H, the weaker the electric field strength tends to be.

In particular, if the electrode spacing H exceeds H1 (100 mm), the electric field strength drops significantly. Furthermore, if the electrode spacing H exceeds H2 (125 mm), the electric field strength drops to a level where heating is impossible. Therefore, the electrode spacing H must be 125 mm or less, and it is preferable that it is 100 mm or less.

The inventors performed a simulation of the generation of an electric field between electrodes using a freezing/thawing chamber 6 having the electrode configuration of this embodiment and a freezing/thawing chamber 6 having an electrode configuration of a comparative example. The electrode configuration of the comparative example is an electrode configuration in which the first electrode 24 or the second electrode 25 does not have an electrode hole.

Figure 13A shows the results of a simulation performed on a freezing/thawing chamber 6 having an electrode configuration of a comparative example. Figure 13B shows the results of a simulation performed on a freezing/thawing chamber 6 having an electrode configuration of this embodiment. In Figures 13A and 13B, the darker areas are areas where the electric field is concentrated. From these results, it can be seen that in the case shown in Figure 13B, electric field concentration is alleviated over the entire electrode compared to the case shown in Figure 13A, and the electric field is made more uniform.

In this embodiment, as shown in FIG. 11, the first electrode 24 and the second electrode 25 are arranged so that the central axis of the electrode hole 41 along the vertical direction does not coincide with the central axis of the electrode hole 42 along the vertical direction. The vertical direction of the electrode hole 41 is the direction along the normal to the flat plate-like first electrode 24, and the vertical direction of the electrode hole 42 is the direction along the normal to the flat plate-like second electrode 25. With this configuration, electric field concentration is alleviated throughout the electrodes.

In addition, in an electrode configuration in which the first electrode 24 and the second electrode 25 are arranged so that the central axis of the electrode hole 41 along the vertical direction coincides with the central axis of the electrode hole 42 along the vertical direction, the concentration of the electric field is generally alleviated compared to an electrode configuration including a second electrode 25 that does not have an electrode hole. The alleviation of the electric field concentration is particularly noticeable at the four corners.

In this embodiment, the freezing/thawing chamber 6 has a storage case 31 fixed to the back of the door 29, as shown in Figures 3 and 4. The storage case 31 moves back and forth inside the freezing/thawing chamber 6 as the door 29 is opened and closed.

The freezing/thawing chamber 6 has rails arranged on both sides so that the storage case 31 can move smoothly inside the freezing/thawing chamber 6. The freezing/thawing chamber 6 also has sliding members arranged on both outside sides of the storage case 31 that slide on the rails. The rails and sliding members are arranged outside the area between the first electrode 24 and the second electrode 25 inside the freezing/thawing chamber 6 so as not to be dielectrically heated.

[1-9. Heat treatment by generating an electric field]
In the refrigerator 1 according to this embodiment, when an electric field generation command is input to the operation unit 47, an electric field generation process is performed in the space between the first electrode 24 and the second electrode 25 in the freezing/thawing compartment 6.

In the electric field generation process of this embodiment, as described below, the control unit 50 controls the cooling mechanism and the cold air introduction mechanism in addition to the dielectric heating mechanism. The cooling mechanism includes a refrigeration cycle such as the compressor 19 and the cooler 13. The cold air introduction mechanism includes the cooling fan 14 and the damper 12a.

In the electric field generation process of this embodiment, a predetermined high-frequency voltage is applied between the first electrode 24 and the second electrode 25, and the food is dielectrically heated by the high-frequency electric field between the electrodes. During dielectric heating, the control unit 50 controls the opening and closing of the damper 12a to introduce cold air continuously or intermittently.

Figure 14 shows the control signals (waveforms (a) and (b)) to the dielectric heating mechanism (oscillator circuit 22) and the cold air introduction mechanism (damper 12a) during the electric field generation process, the temperature [°C] of the food and the freezing/thawing chamber 6 (waveform (c)), and the humidity [% RH] of the freezing/thawing chamber 6 (waveform (d)).

As a characteristic of the frequency used for the electric field generation process, a configuration using VHF waves is less likely to cause "partial cooking" than a configuration using microwaves. Furthermore, to achieve more uniform thawing, the refrigerator 1 according to this embodiment is equipped with an electrode holding substrate 52. This holds the flat plate-shaped first electrode 24 and second electrode 25 approximately parallel and at a predetermined distance (see electrode distance H in Figure 8).

As shown in FIG. 14, when an electric field generation command is input (tm1 in FIG. 14), the oscillator circuit 22 is turned on (waveform (a) in FIG. 14), and a high-frequency voltage of, for example, 40.68 MHz is applied between the first electrode 24 and the second electrode 25. This starts the thawing process. At this time, the damper 12a is open, so the temperature of the freezing/thawing chamber 6 is maintained at the freezing temperature t1 (for example, -20°C).

The damper 12a is closed after a predetermined period of time has elapsed since the start of thawing (tm2 in FIG. 14). When the damper 12a is closed, the temperature in the freezing/thawing chamber 6 begins to rise. In the electric field generation process according to this embodiment, the damper 12a is controlled to open and close in conjunction with dielectric heating. This suppresses the rise in the surface temperature of the frozen product, and thawing is performed without causing so-called "partial cooking."

The control unit 50 controls the opening and closing of the damper 12a based on the reflectance. When the reflectance increases and reaches a preset threshold, the control unit 50 opens the damper 12a to lower the temperature in the freezing/thawing chamber 6 (tm3 in FIG. 14).

In this way, by controlling the opening and closing of damper 12a, cold air is intermittently introduced into freezing/thawing chamber 6 (waveform (b) in FIG. 14), so that the stored items in the storage space of freezing/thawing chamber 6 are dielectrically heated while being maintained in the desired frozen state, and the temperature of the stored items reaches target temperature t2 (waveform (c) in FIG. 14). When control unit 50 detects the desired thawed state based on the reflectance, it ends the electric field generation process.

As the melting of the stored material progresses due to dielectric heating, the amount of melted water molecules in the stored material increases, causing a change in the dielectric constant of the stored material. This causes the impedance matching state to shift, and the reflectance to increase. When the reflectance reaches a preset threshold, the control unit 50 causes the matching circuit 23 to perform impedance matching to reduce the reflectance.

In the electric field generation process of this embodiment, the control unit 50 detects the completion of thawing when the reflectance after performing impedance matching by the matching circuit 23 exceeds a threshold value for detecting the completion of thawing. The threshold value for detecting the completion of thawing is preset to detect when the melting of the stored item has reached the desired thawed state.

Here, the desired thawed state of the stored item means that the user can cut the stored item with one hand and there is only a small amount of dripping from the stored item.

As described above, by controlling the opening and closing of the damper 12a, relatively low-humidity cold air is intermittently supplied to the freezing/thawing chamber 6 via the air passage 12 and the cold air inlet 20. Therefore, unlike when the damper 12a is always closed, the humidity in the freezing/thawing chamber 6 never reaches 100% (waveform (d) in Figure 14). As a result, condensation is prevented from occurring in the freezing/thawing chamber 6.

[1-10. Preservation treatment by generating an electric field]
FIG. 15 is a flow chart showing the control of the cooling and electric field generation process for bringing food into a desired state in the freezing/thawing compartment 6.

As described above, when the reflectance exceeds the threshold for detecting the completion of thawing after performing impedance matching in the electric field generation process, the control unit 50 performs the control after the electric field generation process shown in FIG. 15. For example, the stored item is maintained in the desired thawed state after the thawing process is completed.

One method of control for this purpose is to adjust the temperature of the freezing/thawing chamber 6 to the so-called slightly freezing temperature range, for example, about -1°C to -3°C. Another method is to adjust the temperature of the freezing/thawing chamber 6 to the freezing temperature range, for example, -18°C to -20°C.

Furthermore, the temperature of the freezing/thawing chamber 6 may be periodically changed. By periodically changing the temperature of the freezing/thawing chamber 6, for example, from -12°C to -5°C, the composition of the food can be affected. In the above control method, a low-output high-frequency electric field is continuously applied, or a high-frequency electric field is intermittently applied, to cool and heat the stored items and maintain them at the desired temperature ranges.

As shown in FIG. 15, in step S101, after the start of the preservation process, the control unit 50 detects the presence or absence of a stored item in the freezing/thawing chamber 6 based on the reflectance (step S101).

Specifically, the control unit 50 causes the matching circuit 23 to operate intermittently and causes the oscillator circuit 22 to output low-power electromagnetic waves intermittently. The control unit 50 compares the reflectance with a preset threshold value for detecting the presence or absence of stored items to determine the presence or absence of stored items in the freezing/thawing chamber 6.

If the control unit 50 detects that no stored item is present in the freezing/thawing chamber 6 (No in step S101), the control unit 50 transitions the process to step S105. In step S105, the control unit 50 adjusts the temperature of the freezing/thawing chamber 6 to a freezing temperature range, for example, -18°C to -20°C. Hereinafter, the process of step S105 is referred to as the freezing process.

If the control unit 50 detects that a stored item is present in the freezing/thawing chamber 6 (Yes in step S101), in step S102, it determines whether the stored item includes a non-frozen item after thawing based on the change in reflectance.

Even when the electric field generation process for the stored item is complete, there are cases where the user does not immediately remove the stored item from the freezing/thawing chamber 6. In such cases, the control unit 50 controls the cooling mechanism to maintain the slightly freezing temperature range in the freezing/thawing chamber 6, which allows the stored item to be kept in the desired thawed state, for a predetermined time. If the stored item is stored beyond this predetermined time, the control unit 50 shifts the temperature of the freezing/thawing chamber 6 to the freezing temperature range in order to maintain the freshness of the stored item.

In step S102, if the control unit 50 determines that the time since the completion of thawing has exceeded the predetermined time while the thawed stored item is still stored (step S102), it also shifts the process to step S105 and performs the freezing process.

In step S102, if the control unit 50 determines that no thawed non-frozen items are stored in the freezing/thawing compartment 6 (No in step S102), it transitions the process to step S103.

In step S103, the control unit 50 determines whether the food temperature exceeds the target temperature. If the food temperature exceeds the target temperature (Yes in step S103), the control unit 50 shifts the process to step S105 and performs the freezing process. If not (No in step S103), the control unit 50 shifts the process to step S104 and raises the temperature of the food by generating an electric field.

Below, a specific example of this control is described. In the freezing process, the refrigerator 1 according to this embodiment performs dielectric heating so that the stored items (food) are frozen and stored in a desired state.

Generally, when food is frozen, moisture inside the freezing/thawing chamber 6 and moisture inside the food cause frost to form on the inside of the food packaging. When frost forms on the surface of the food, the food suffers from freezer burn. Freezer burn is a phenomenon in which food becomes dry and flaky due to freezing, making it no longer fresh and tasty.

To prevent freezer burn, the refrigerator 1 according to this embodiment performs cooling and dielectric heating simultaneously.

FIGS. 16A and 16B are waveform diagrams showing the state of each element during cooling operation. FIG. 16A is a waveform diagram showing the cooling operation in a conventional refrigerator. FIG. 16B is a waveform diagram showing the cooling operation in refrigerator 1 according to the present embodiment.

In FIG. 16A, waveform (1) indicates the ON/OFF of the cooling operation. The ON/OFF of the cooling operation corresponds to, for example, opening and closing of damper 12a, or turning compressor 19 ON/OFF. That is, when the cooling operation is "ON", cold air is introduced into freezer compartment 8. When the cooling operation is "OFF", damper 12a is closed, blocking the introduction of cold air into freezer compartment 8.

Therefore, as shown in waveform (2) of Figure 16A, the temperature of the food in freezer compartment 8 fluctuates greatly around a preset freezing temperature t1 (e.g., -20°C). As a result, with conventional cooling operations, the food may not be frozen in the desired state, with water evaporating and frosting occurring repeatedly on the surface of the food in freezer compartment 8.

On the other hand, in the cooling operation of refrigerator 1 shown in FIG. 16B, unlike conventional cooling operations, food is cooled and dielectrically heated at the same time. Waveform (1) in FIG. 16B shows the opening and closing of damper 12a.

In FIG. 16B, "ON" indicates that the damper 12a is open. In this state, cold air is introduced into the freezing/thawing chamber 6 through the air passage 12 and the cold air introduction hole 20. "OFF" indicates that the damper 12a is closed. In this state, the introduction of cold air into the freezing/thawing chamber 6 is blocked. In the cooling operation of this embodiment, the introduction of cold air is performed simultaneously with dielectric heating. Therefore, to prevent a decrease in cooling capacity, the time for introducing cold air is set longer than in the conventional example.

The waveform (2) in FIG. 16B shows the operating state of the oscillator circuit 22. As shown in the waveform (2) in FIG. 16B, the control unit 50 turns on the oscillator circuit 22 when the damper 12a is open to perform dielectric heating.

In the cooling operation of this embodiment, dielectric heating is performed at a lower output than in the thawing operation. The control unit 50 adjusts the output power by controlling the power supplied to the oscillation circuit 22 and by PWM control (intermittent control) of the output of the oscillation circuit 22.

As a result, as shown by waveform (3) in FIG. 16B, the temperature of the food in the freezing/thawing chamber 6 is maintained at the preset freezing temperature t1 (e.g., -20°C). In other words, fluctuations in the food temperature are suppressed.

The results of these experiments showed that if the fluctuation in food temperature was less than about 0.1 K, the occurrence of frost could be prevented. In other words, by suppressing the fluctuation in food temperature, the occurrence of frost could be suppressed.

Furthermore, by applying dielectric heating at the same frequency as thawing but with a lower output power than thawing, it is possible to suppress the extension of ice crystals inside the food. When dielectric heating is performed, an electric field tends to concentrate at the tips of the ice crystals that have formed inside the food. For this reason, even if the temperature inside the freezing/thawing chamber 6 is below the maximum ice crystal formation zone, the ice crystals will only extend slowly.

As described above, the refrigerator 1 according to this embodiment performs dielectric heating during the cooling operation during frozen storage, allowing the frozen items to be frozen and stored in a desired state.

[1-11. Freezing treatment by generating an electric field]
The refrigerator 1 according to this embodiment performs a freezing process on non-frozen food newly placed in the freezing/thawing compartment 6 based on a user's command inputted via the operation unit 47. Fig. 17 is a waveform diagram showing the state of each element during the rapid cooling operation which is the freezing process.

The waveform (a) in FIG. 17 indicates whether or not a stored item (food) is present in the freezing/thawing chamber 6. The control unit 50 determines whether or not a stored item is present in the freezing/thawing chamber 6 based on the reflectance.

Waveform (b) in FIG. 17 shows that the control unit 50 intermittently acquires information from the matching circuit 23 and the detection unit 51. Waveform (c) in FIG. 17 shows an example of the transition of the reflectance. When the reflectance falls below the first threshold value R1 [%], the control unit 50 determines that a stored item has been placed in the freezing/thawing chamber 6.

When rapidly cooling food stored in the freezing/thawing compartment 6, the control unit 50 increases the rotation speed of the compressor 19 and cooling fan 14 of the cooling mechanism to perform forced continuous operation with increased cooling capacity. As shown in waveform (d) of Figure 17, the control unit 50 forcibly opens the damper 12a of the air passage 12 leading to the freezing/thawing compartment 6 to introduce cold air.

During the rapid cooling operation, dielectric heating 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). Dielectric heating at this time is performed intermittently (period h in waveform (e) in Figure 17) in order to reduce the output (for example, to several tens of watts or less) from that during thawing.

To start dielectric heating, the control unit 50 detects that the food temperature has entered the maximum ice crystal formation zone by detecting an increasing change in reflectance as the food passes through the latent heat zone. In this embodiment, dielectric heating is started when the detected reflectance enters a preset second threshold value R2 [%] (see waveform (e) in Figure 17).

If the reflectance is in the range between the second threshold value R2 [%] and the third threshold value R3 [%], the control unit 50 determines that the temperature of the food is in the maximum ice crystal formation zone and continues dielectric heating. If a predetermined time pr1 (see waveform diagram (c) in Figure 17) has passed since the reflectance entered the third threshold value R3 [%], it determines that the temperature of the food has passed the maximum ice crystal formation zone and stops dielectric heating.

As described above, the control unit 50 stops the dielectric heating, terminates the rapid cooling operation, and performs the normal cooling operation. In this way, even when performing the rapid cooling operation, the food can be maintained in a desired frozen state by performing dielectric heating for the desired period of time.

[1-12. Safety control using door switches]
As described above, in order to prevent electromagnetic waves from leaking to the outside, refrigerator 1 according to this embodiment includes electromagnetic wave shield 26 surrounding freezing/thawing compartment 6. Furthermore, since the steel plate itself functions as an electromagnetic wave shield, external leakage of electromagnetic waves is prevented by closing door 29.

However, when the door 29 is opened, there is a possibility that electromagnetic waves may leak from the opening of the freezing/thawing chamber 6. Therefore, safety measures are necessary.

The refrigerator 1 according to this embodiment includes a door open/close detector 55a (see FIG. 9) that detects the opening of the door 29. When the door open/close detector 55a detects that the door 29 is open, the controller 50 stops the oscillator circuit 22 and stops the power supply to the first electrode 24.

In addition to door 29 of freezer/thaw compartment 6, refrigerator 1 has multiple doors that cover the front openings of refrigerator compartment 5, ice-making compartment 7, freezer compartment 8, and vegetable compartment 9. Refrigerator 1 also has door opening/closing detector 55b, door opening/closing detector 55c, door opening/closing detector 55d, and door opening/closing detector 55e. Door opening/closing detectors 55b, 55c, 55d, and 55e detect the opening of the doors of refrigerator compartment 5, ice-making compartment 7, freezer compartment 8, and vegetable compartment 9, respectively.

If the electromagnetic wave shield 26 is functioning adequately, no electromagnetic waves will leak out beyond the specified limit. Therefore, even if any of the door opening/closing detectors 55b-55e detects the opening of a door to a storage compartment other than the freezer/thaw compartment 6, the controller 50 will continue to operate the oscillator circuit 22.

However, if design issues mean that the electromagnetic wave shield 26 cannot fully surround the freezing/thawing chamber 6, measures are required to prevent electromagnetic waves from leaking out.

If it is not possible to place the electromagnetic wave shield 26 on the top surface of the freezing/thawing chamber 6, when the door of the storage chamber above the freezing/thawing chamber 6 (in this embodiment, the refrigerator chamber 5 (see Figure 1)) is opened, the control unit 50 stops the oscillation circuit 22.

If it is not possible to place the electromagnetic wave shield 26 on the bottom surface of the freezing/thawing chamber 6, when the door of the storage chamber below the freezing/thawing chamber 6 (in this embodiment, the freezing chamber 8 and the vegetable chamber 9 (see Figure 1)) is opened, the control unit 50 stops the oscillation circuit 22.

If the electromagnetic wave shield 26 cannot be placed on the side of the freezing/thawing chamber 6, when the door of the storage chamber (in this embodiment, the ice-making chamber 7 (see FIG. 1)) on the side of the freezing/thawing chamber 6 is opened, the control unit 50 stops the oscillation circuit 22.

In this way, when the door to the storage compartment on the side where the electromagnetic wave shield 26 cannot be placed is opened, the control unit 50 stops the oscillator circuit 22 to prevent leakage of electromagnetic waves.

The following describes how to stop the oscillator circuit 22.

FIG. 18A shows a configuration in which the door open/close detector 55a cuts off the power supply from the power supply 48 to the oscillator circuit 22. As shown in FIG. 18A, the door open/close detector 55a is a switch mechanism that is conductive when the door 29 is closed and cuts off the power when the door 29 is opened. When the door 29 is opened, the door open/close detector 55a cuts off the power supply to the oscillator circuit 22, reliably stopping the operation of the oscillator circuit 22.

FIG. 18B shows a configuration in which a door open/close detector 55a stops the operation of the power supply controller 48a, which controls the power supply 48. As shown in FIG. 18B, the door open/close detector 55a is a switch mechanism similar to that in FIG. 18A. When the door 29 is opened, the door open/close detector 55a cuts off the power supply to the power supply controller 48a, thereby cutting off the power supply from the power supply 48 to the oscillation circuit 22, and reliably stops the operation of the oscillation circuit 22.

In the configuration shown in FIG. 18B, the operation of the oscillator circuit 22 is stopped by cutting off the power supply to the circuitry within the power supply control unit 48a, but the present disclosure is not limited to this.

For example, the power supply control unit 48a may include an overcurrent protection circuit that detects an overcurrent. In this case, when the overcurrent protection circuit detects the occurrence of an overcurrent, the power supply control unit 48a stops the power supply. The power supply unit 48 may recognize the occurrence of an overcurrent as an overload state and stop the power supply.

FIG. 18C shows a configuration for determining whether the door 29 is open or closed using a door open/close detector 55a and a magnetic sensor 55f. As shown in FIG. 18C, the door open/close detector 55a is disposed between the magnetic sensor 55f and the controller 50.

The door open/close detection unit 55a is conductive when the door 29 is closed and is cut off when the door 29 is opened. The magnetic sensor 55f sends a signal indicating whether the door 29 is open or closed to the control unit 50. The control unit 50 sends a signal indicating whether the power supply control unit 48a is operating or not to the power supply control unit 48a in response to the signal from the magnetic sensor 55f.

In the configuration shown in FIG. 18C, when the door 29 is opened, the power supply control unit 48a is no longer able to receive a signal from the magnetic sensor 55f. This stops the power supply to the oscillation circuit 22.

In the configuration shown in Figures 18A to 18C, power supply and control signal conduction/cutoff are achieved by hardware. This provides high resistance to high frequency noise and external noise, and makes malfunctions less likely to occur.

In the configuration shown in Figures 18B and 18C, the door open/close detection unit 55a is conductive when the door 29 is closed and is cut off when the door 29 is opened. However, a circuit that is cut off when the door 29 is closed and is conductive when the door 29 is opened may be used. In that case, the logic for stopping the power supply control unit 48a is reversed.

The refrigerator 1 according to this embodiment includes a freezing/thawing compartment 6 that has both a freezing function and a thawing function. However, according to the present disclosure, the same effect can be obtained even in a configuration that includes a thawing compartment that only has a thawing function.

[2-1. Effects, etc.]
As described above, the refrigerator 1 according to one embodiment of the present disclosure includes a storage compartment (freeze/thaw 6) capable of heating stored items, and a dielectric heating mechanism that generates high-frequency power and supplies the high-frequency power to the storage compartment to generate an electric field inside the storage compartment.

The dielectric heating mechanism includes an oscillator circuit 22 that supplies high-frequency power to the electrodes (first electrode 24, second electrode 25), a matching circuit 23 that matches the impedance of the electrodes, a detector 51 that is connected between the oscillator circuit 22 and the matching circuit 23 and measures the incident wave power output from the matching circuit 23 to the electrodes and the reflected wave power returning to the oscillator circuit 22, and a controller 50.

The control unit 50 controls the oscillation circuit 22 and the matching circuit 23 based on the incident wave power and the reflected wave power, and detects abnormalities in the incident wave power or the reflected wave power. In other words, the control unit 50 functions as an abnormality detection means. According to this aspect, in a refrigerator equipped with a dielectric heating mechanism, it is possible to more accurately detect abnormalities in the dielectric heating mechanism, thereby appropriately stopping heating.

A refrigerator 1 according to another aspect of the present disclosure includes a storage compartment (freeze/thaw 6) capable of heating stored items, a dielectric heating mechanism that generates high-frequency power and supplies the high-frequency power to the storage compartment to generate an electric field inside the storage compartment, and a cooling mechanism 58 that cools the dielectric heating mechanism.

The dielectric heating mechanism includes an oscillator circuit 22 that supplies high-frequency power to the electrodes (first electrode 24, second electrode 25), a matching circuit 23 that matches the impedance of the electrodes, a detector 51 that is connected between the oscillator circuit 22 and the matching circuit 23 and measures the incident wave power output from the matching circuit 23 to the electrodes and the reflected wave power returning to the oscillator circuit 22, and a controller 50.

The control unit 50 controls the oscillation circuit 22 and the matching circuit 23 based on the incident wave power and the reflected wave power, and also controls the cooling mechanism 58, which is an anomaly avoidance means, to avoid anomalies in the incident wave power or the reflected wave power. According to this embodiment, an anomaly can be avoided by operating the cooling mechanism 58 before an anomaly is determined.

This disclosure is applicable to various refrigerators.

REFRIGERATION CIRCUIT 2 BODY 3 OUTER BOX 4 INNER BOX 5 REFRIGERATOR COMPARTMENT 6 FREEZER/THAW COMPARTMENT 7 ICE COMPARTMENT 8 FREEZER COMPARTMENT 9 VEGETABLE COMPARTMENT 10 MACHINE COMPARTMENT 11 COOLING COMPARTMENT 12 AIR GUIDE 12a DAMPER 13 COOLER 14 COOLING FAN 15 DEFROST HEATER 16 DRAIN PAN 17 DRAIN TUBE 18 EVAPORATION DISH 19 COMPRESSOR 20 COOL AIR INTRODUCTION HOLE 21 CROSSRAIL 22 OSCILLATOR CIRCUIT 22a OSCILLATOR SOURCE 22b FIRST AMPLIFIER CIRCUIT 22c SECOND AMPLIFIER CIRCUIT 23 MATCHING CIRCUIT 24 FIRST ELECTRODE 24a, 24b, 24c POSITIVE ELECTRODE TERMINAL 25 SECOND ELECTRODE 25a, 25b, 25c CATHODE TERMINAL 26 ELECTROMAGNETIC WAVE SHIELD 26a TOP SIDE ELECTROMAGNETIC WAVE SHIELD 26b REAR SIDE ELECTROMAGNETIC WAVE SHIELD 26c Bottom side electromagnetic wave shield 26d Door side electromagnetic wave shield 29 Door 30 Electrode holding area 31 Storage case 32, 32a, 32b, 32c Inner surface member 36 Gasket 40 Insulating material 41 Electrode hole 42 Electrode hole 47 Operation unit 48 Power supply unit 48a Power supply control unit 49 Temperature sensor 50 Control unit 51 Detection unit 52 Electrode holding substrate 53 High frequency heating module 54 Support 55a, 55b, 55c, 55d, 55e Door opening/closing detection unit 55f Magnetic sensor 56, 56a, 56b Coaxial cable 57 Current detection unit 58 Cooling mechanism

Claims (12)

A storage chamber capable of heating stored items;
A dielectric heating mechanism configured to generate high-frequency power and supply the high-frequency power to the storage chamber to generate an electric field inside the storage chamber,
The dielectric heating mechanism includes:
an electrode disposed in the storage chamber;
an oscillator circuit configured to supply the high frequency power to the electrode;
a matching circuit configured to match the impedance of the electrode;
A detection unit connected between the oscillation circuit and the matching circuit and configured to measure an incident wave power output from the matching circuit to the electrode and a reflected wave power returning to the oscillation circuit;
a control unit configured to control the oscillation circuit and the matching circuit based on the incident wave power and the reflected wave power, and to detect an abnormality in the incident wave power or the reflected wave power. A storage chamber capable of heating stored items;
a dielectric heating mechanism configured to generate high frequency power and supply the high frequency power to the storage chamber to generate an electric field inside the storage chamber;
A cooling mechanism configured to cool the dielectric heating mechanism,
The dielectric heating mechanism includes:
an electrode disposed in the storage chamber;
an oscillator circuit configured to supply the high frequency power to the electrode;
a matching circuit configured to match the impedance of the electrode;
A detection unit connected between the oscillation circuit and the matching circuit and configured to measure an incident wave power output from the matching circuit to the electrode and a reflected wave power returning to the oscillation circuit;
The refrigerator according to claim 1, further comprising: a control unit configured to control the oscillation circuit and the matching circuit based on the incident wave power and the reflected wave power, and to control the cooling mechanism to avoid an abnormality in the incident wave power or the reflected wave power. The refrigerator according to claim 1, wherein the control unit is configured to determine that an abnormality has occurred based on the number of values of the incident wave power, or the incident wave power and the reflected wave power, that exceed their respective predetermined thresholds obtained during a predetermined period of time. The refrigerator according to claim 1, wherein the control unit is configured to determine that an abnormality has occurred when the incident wave power, or the incident wave power and the reflected wave power, exceed their respective predetermined thresholds, and the current supplied to the oscillation circuit exceeds another predetermined threshold. The refrigerator according to claim 1, wherein the control unit is configured to determine that an abnormality has occurred when the difference between the values of the incident wave power and the reflected wave power at the time of abnormality detection and the values up to the time of abnormality detection exceeds a predetermined threshold value. The refrigerator according to claim 1, wherein the control unit is configured to determine that an abnormality has occurred when the change in the reflected wave power within a predetermined time from the impedance adjustment in the matching circuit, or the change in the reflectance, which is the ratio of the reflected wave power to the incident wave power, does not exceed a predetermined threshold value. The refrigerator according to claim 1, wherein the control unit is configured to determine that an abnormality has occurred when the change in the reflected wave power or the reflectance, which is the ratio of the reflected wave power to the incident wave power, exceeds a predetermined threshold value after a predetermined time has elapsed since the impedance adjustment in the matching circuit. The refrigerator according to claim 1, wherein the control unit is configured to determine that an abnormality has occurred when the value of the incident wave power, or the value of the incident wave power and the reflected wave power, exceeds a respective predetermined threshold value, and the value of the current supplied to the oscillation circuit exceeds another predetermined threshold value. a temperature sensor disposed in the matching circuit;
The refrigerator according to claim 1 , wherein the control unit is configured to determine that an abnormality has occurred when the temperature detected by the temperature sensor exceeds a predetermined threshold value. a temperature sensor disposed in the matching circuit;
The refrigerator according to claim 1, wherein the control unit is configured to determine an abnormality based on the temperature detected by the temperature sensor and a time change in reflectance, which is a ratio of the reflected wave power to the incident wave power. The refrigerator according to claim 2, wherein the control unit is configured to control the cooling mechanism according to the current value supplied to the oscillation circuit. The refrigerator according to claim 2, wherein the control unit is configured to control the cooling mechanism according to the incident wave power, the reflected wave power, and a current value supplied to the oscillation circuit.

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